Release 1.0.67

Implement Serialize for core::fmt::Arguments

.github/ISSUE_TEMPLATE/1-problem.md

@@ -0,0 +1,7 @@
+---
+name: Problem
+about: Something does not seem right
+
+---
+
+

.github/ISSUE_TEMPLATE/2-suggestion.md

@@ -0,0 +1,7 @@
+---
+name: Suggestion
+about: Share how Serde could support your use case better
+
+---
+
+

.github/ISSUE_TEMPLATE/3-documentation.md

@@ -0,0 +1,7 @@
+---
+name: Documentation
+about: Certainly there is room for improvement
+
+---
+
+

.github/ISSUE_TEMPLATE/4-discussion.md

@@ -0,0 +1,7 @@
+---
+name: Help or discussion
+about: This is the right place
+
+---
+
+

.github/ISSUE_TEMPLATE/5-other.md

@@ -0,0 +1,7 @@
+---
+name: Anything else!
+about: Whatever is on your mind
+
+---
+
+

.travis.yml

@@ -4,10 +4,15 @@ cache: cargo
 
 # run builds for all the trains (and more)
 rust:
-  - 1.13.0
   - stable
   - beta
   - nightly
+  - 1.13.0
+  - 1.15.0
+  - 1.20.0
+  - 1.21.0
+  - 1.25.0
+  - 1.26.0
 
 matrix:
   include:

README.md

@@ -1,9 +1,11 @@
-# Serde   [![Build Status]][travis] [![Latest Version]][crates.io]
+# Serde   [![Build Status]][travis] [![Latest Version]][crates.io] [![Rustc Version 1.13+]][rustc]
 
 [Build Status]: https://api.travis-ci.org/serde-rs/serde.svg?branch=master
 [travis]: https://travis-ci.org/serde-rs/serde
 [Latest Version]: https://img.shields.io/crates/v/serde.svg
 [crates.io]: https://crates.io/crates/serde
+[Rustc Version 1.13+]: https://img.shields.io/badge/rustc-1.13+-lightgray.svg
+[rustc]: https://blog.rust-lang.org/2016/11/10/Rust-1.13.html
 
 **Serde is a framework for *ser*ializing and *de*serializing Rust data structures efficiently and generically.**
 
@@ -23,7 +25,7 @@ You may be looking for:
 <details>
 <summary>
 Click to show Cargo.toml.
-<a href="http://play.integer32.com/?gist=9003c5b88c1f4989941925d7190c6eec" target="_blank">Run this code in the playground.</a>
+<a href="https://play.rust-lang.org/?gist=9003c5b88c1f4989941925d7190c6eec" target="_blank">Run this code in the playground.</a>
 </summary>
 
 ```toml

crates-io.md

@@ -0,0 +1,55 @@
+<!-- Serde readme rendered on crates.io -->
+
+**Serde is a framework for *ser*ializing and *de*serializing Rust data structures efficiently and generically.**
+
+---
+
+You may be looking for:
+
+- [An overview of Serde](https://serde.rs/)
+- [Data formats supported by Serde](https://serde.rs/#data-formats)
+- [Setting up `#[derive(Serialize, Deserialize)]`](https://serde.rs/codegen.html)
+- [Examples](https://serde.rs/examples.html)
+- [API documentation](https://docs.serde.rs/serde/)
+- [Release notes](https://github.com/serde-rs/serde/releases)
+
+## Serde in action
+
+```rust
+#[macro_use]
+extern crate serde_derive;
+
+extern crate serde;
+extern crate serde_json;
+
+#[derive(Serialize, Deserialize, Debug)]
+struct Point {
+    x: i32,
+    y: i32,
+}
+
+fn main() {
+    let point = Point { x: 1, y: 2 };
+
+    // Convert the Point to a JSON string.
+    let serialized = serde_json::to_string(&point).unwrap();
+
+    // Prints serialized = {"x":1,"y":2}
+    println!("serialized = {}", serialized);
+
+    // Convert the JSON string back to a Point.
+    let deserialized: Point = serde_json::from_str(&serialized).unwrap();
+
+    // Prints deserialized = Point { x: 1, y: 2 }
+    println!("deserialized = {:?}", deserialized);
+}
+```
+
+## Getting help
+
+Serde developers live in the #serde channel on
+[`irc.mozilla.org`](https://wiki.mozilla.org/IRC). The #rust channel is also a
+good resource with generally faster response time but less specific knowledge
+about Serde. If IRC is not your thing or you don't get a good response, we are
+happy to respond to [GitHub issues](https://github.com/serde-rs/serde/issues/new)
+as well.

rustfmt.toml

@@ -1,2 +1 @@
 error_on_line_overflow = false
-same_line_attributes = false

serde/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde"
-version = "1.0.34" # remember to update html_root_url
+version = "1.0.67" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "A generic serialization/deserialization framework"
@@ -9,8 +9,9 @@ repository = "https://github.com/serde-rs/serde"
 documentation = "https://docs.serde.rs/serde/"
 keywords = ["serde", "serialization", "no_std"]
 categories = ["encoding"]
-readme = "README.md"
-include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
+readme = "crates-io.md"
+include = ["Cargo.toml", "build.rs", "src/**/*.rs", "crates-io.md", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
+build = "build.rs"
 
 [badges]
 travis-ci = { repository = "serde-rs/serde" }
@@ -28,14 +29,30 @@ serde_derive = { version = "1.0", path = "../serde_derive" }
 [features]
 default = ["std"]
 
-# Re-export the derive(Serialize, Deserialize) macros. This is specifically
-# intended for library crates that provide optional Serde impls behind a Cargo
-# cfg of their own. All other crates should depend on serde_derive directly.
+# Re-export the derive(Serialize, Deserialize) macros. This is intended for
+# library crates that provide optional Serde impls behind a Cargo cfg of their
+# own.
+#
+# Mainly this is a workaround for limitations associated with
+# rust-lang/cargo#1286 in which a library crate cannot use one "serde" cfg in
+# Cargo to enable dependencies on both serde and serde_derive crates.
+#
+# The recommended way to provide optional Serde support that requires derive is
+# as follows. In particular, please do not name your library's Serde feature
+# anything other than "serde".
+#
+#     [dependencies]
+#     serde = { version = "1.0", optional = true, features = ["derive"] }
+#
+# Within the library, these optional Serde derives would be written like this.
+#
+#     #[cfg(feature = "serde")]
+#     #[macro_use]
+#     extern crate serde;
+#
+#     #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#     struct ...
 #
-# Please refer to the long comment above the line `pub use serde_derive::*` in
-# src/lib.rs before enabling this feature. If you think you need this feature
-# and your use case does not precisely match the one described in the comment,
-# please open an issue to let us know about your use case.
 derive = ["serde_derive"]
 
 # Provide impls for common standard library types like Vec<T> and HashMap<K, V>.
@@ -61,8 +78,3 @@ alloc = ["unstable"]
 # does not preserve identity and may result in multiple copies of the same data.
 # Be sure that this is what you want before enabling this feature.
 rc = []
-
-# Get serde_derive picked up by the Integer 32 playground. Not public API.
-#
-#    http://play.integer32.com/
-playground = ["serde_derive"]

serde/build.rs

@@ -0,0 +1,78 @@
+use std::env;
+use std::process::Command;
+use std::str::{self, FromStr};
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let minor = match rustc_minor_version() {
+        Some(minor) => minor,
+        None => return,
+    };
+
+    // CString::into_boxed_c_str stabilized in Rust 1.20:
+    // https://doc.rust-lang.org/std/ffi/struct.CString.html#method.into_boxed_c_str
+    if minor >= 20 {
+        println!("cargo:rustc-cfg=de_boxed_c_str");
+    }
+
+    // From<Box<T>> for Rc<T> / Arc<T> stabilized in Rust 1.21:
+    // https://doc.rust-lang.org/std/rc/struct.Rc.html#impl-From<Box<T>>
+    // https://doc.rust-lang.org/std/sync/struct.Arc.html#impl-From<Box<T>>
+    if minor >= 21 {
+        println!("cargo:rustc-cfg=de_rc_dst");
+    }
+
+    // Duration available in core since Rust 1.25:
+    // https://blog.rust-lang.org/2018/03/29/Rust-1.25.html#library-stabilizations
+    if minor >= 25 {
+        println!("cargo:rustc-cfg=core_duration");
+    }
+
+    // 128-bit integers stabilized in Rust 1.26:
+    // https://blog.rust-lang.org/2018/05/10/Rust-1.26.html
+    if minor >= 26 {
+        println!("cargo:rustc-cfg=integer128");
+    }
+
+    // Non-zero integers stabilized in Rust 1.28:
+    // https://github.com/rust-lang/rust/pull/50808
+    if minor >= 28 {
+        println!("cargo:rustc-cfg=num_nonzero");
+    }
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = match env::var_os("RUSTC") {
+        Some(rustc) => rustc,
+        None => return None,
+    };
+
+    let output = match Command::new(rustc).arg("--version").output() {
+        Ok(output) => output,
+        Err(_) => return None,
+    };
+
+    let version = match str::from_utf8(&output.stdout) {
+        Ok(version) => version,
+        Err(_) => return None,
+    };
+
+    // Temporary workaround to support the old 1.26-dev compiler on docs.rs.
+    if version.contains("0eb87c9bf") {
+        return Some(25);
+    }
+
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+
+    let next = match pieces.next() {
+        Some(next) => next,
+        None => return None,
+    };
+
+    u32::from_str(next).ok()
+}

serde/crates-io.md

@@ -0,0 +1 @@
+../crates-io.md

serde/src/de/from_primitive.rs

@@ -9,42 +9,40 @@
 use lib::*;
 
 macro_rules! int_to_int {
-    ($dst:ident, $n:ident) => (
+    ($dst:ident, $n:ident) => {
         if $dst::min_value() as i64 <= $n as i64 && $n as i64 <= $dst::max_value() as i64 {
             Some($n as $dst)
         } else {
             None
         }
-    )
+    };
 }
 
 macro_rules! int_to_uint {
-    ($dst:ident, $n:ident) => (
+    ($dst:ident, $n:ident) => {
         if 0 <= $n && $n as u64 <= $dst::max_value() as u64 {
             Some($n as $dst)
         } else {
             None
         }
-    )
+    };
 }
 
 macro_rules! uint_to {
-    ($dst:ident, $n:ident) => (
+    ($dst:ident, $n:ident) => {
         if $n as u64 <= $dst::max_value() as u64 {
             Some($n as $dst)
         } else {
             None
         }
-    )
+    };
 }
 
 pub trait FromPrimitive: Sized {
-    fn from_isize(n: isize) -> Option<Self>;
     fn from_i8(n: i8) -> Option<Self>;
     fn from_i16(n: i16) -> Option<Self>;
     fn from_i32(n: i32) -> Option<Self>;
     fn from_i64(n: i64) -> Option<Self>;
-    fn from_usize(n: usize) -> Option<Self>;
     fn from_u8(n: u8) -> Option<Self>;
     fn from_u16(n: u16) -> Option<Self>;
     fn from_u32(n: u32) -> Option<Self>;
@@ -52,54 +50,120 @@ pub trait FromPrimitive: Sized {
 }
 
 macro_rules! impl_from_primitive_for_int {
-    ($t:ident) => (
+    ($t:ident) => {
         impl FromPrimitive for $t {
-            #[inline] fn from_isize(n: isize) -> Option<Self> { int_to_int!($t, n) }
-            #[inline] fn from_i8(n: i8) -> Option<Self> { int_to_int!($t, n) }
-            #[inline] fn from_i16(n: i16) -> Option<Self> { int_to_int!($t, n) }
-            #[inline] fn from_i32(n: i32) -> Option<Self> { int_to_int!($t, n) }
-            #[inline] fn from_i64(n: i64) -> Option<Self> { int_to_int!($t, n) }
-            #[inline] fn from_usize(n: usize) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u8(n: u8) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u16(n: u16) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u32(n: u32) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u64(n: u64) -> Option<Self> { uint_to!($t, n) }
+            #[inline]
+            fn from_i8(n: i8) -> Option<Self> {
+                int_to_int!($t, n)
+            }
+            #[inline]
+            fn from_i16(n: i16) -> Option<Self> {
+                int_to_int!($t, n)
+            }
+            #[inline]
+            fn from_i32(n: i32) -> Option<Self> {
+                int_to_int!($t, n)
+            }
+            #[inline]
+            fn from_i64(n: i64) -> Option<Self> {
+                int_to_int!($t, n)
+            }
+            #[inline]
+            fn from_u8(n: u8) -> Option<Self> {
+                uint_to!($t, n)
+            }
+            #[inline]
+            fn from_u16(n: u16) -> Option<Self> {
+                uint_to!($t, n)
+            }
+            #[inline]
+            fn from_u32(n: u32) -> Option<Self> {
+                uint_to!($t, n)
+            }
+            #[inline]
+            fn from_u64(n: u64) -> Option<Self> {
+                uint_to!($t, n)
+            }
         }
-    )
+    };
 }
 
 macro_rules! impl_from_primitive_for_uint {
-    ($t:ident) => (
+    ($t:ident) => {
         impl FromPrimitive for $t {
-            #[inline] fn from_isize(n: isize) -> Option<Self> { int_to_uint!($t, n) }
-            #[inline] fn from_i8(n: i8) -> Option<Self> { int_to_uint!($t, n) }
-            #[inline] fn from_i16(n: i16) -> Option<Self> { int_to_uint!($t, n) }
-            #[inline] fn from_i32(n: i32) -> Option<Self> { int_to_uint!($t, n) }
-            #[inline] fn from_i64(n: i64) -> Option<Self> { int_to_uint!($t, n) }
-            #[inline] fn from_usize(n: usize) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u8(n: u8) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u16(n: u16) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u32(n: u32) -> Option<Self> { uint_to!($t, n) }
-            #[inline] fn from_u64(n: u64) -> Option<Self> { uint_to!($t, n) }
+            #[inline]
+            fn from_i8(n: i8) -> Option<Self> {
+                int_to_uint!($t, n)
+            }
+            #[inline]
+            fn from_i16(n: i16) -> Option<Self> {
+                int_to_uint!($t, n)
+            }
+            #[inline]
+            fn from_i32(n: i32) -> Option<Self> {
+                int_to_uint!($t, n)
+            }
+            #[inline]
+            fn from_i64(n: i64) -> Option<Self> {
+                int_to_uint!($t, n)
+            }
+            #[inline]
+            fn from_u8(n: u8) -> Option<Self> {
+                uint_to!($t, n)
+            }
+            #[inline]
+            fn from_u16(n: u16) -> Option<Self> {
+                uint_to!($t, n)
+            }
+            #[inline]
+            fn from_u32(n: u32) -> Option<Self> {
+                uint_to!($t, n)
+            }
+            #[inline]
+            fn from_u64(n: u64) -> Option<Self> {
+                uint_to!($t, n)
+            }
         }
-    )
+    };
 }
 
 macro_rules! impl_from_primitive_for_float {
-    ($t:ident) => (
+    ($t:ident) => {
         impl FromPrimitive for $t {
-            #[inline] fn from_isize(n: isize) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_i8(n: i8) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_i16(n: i16) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_i32(n: i32) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_i64(n: i64) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_usize(n: usize) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_u8(n: u8) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_u16(n: u16) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_u32(n: u32) -> Option<Self> { Some(n as Self) }
-            #[inline] fn from_u64(n: u64) -> Option<Self> { Some(n as Self) }
+            #[inline]
+            fn from_i8(n: i8) -> Option<Self> {
+                Some(n as Self)
+            }
+            #[inline]
+            fn from_i16(n: i16) -> Option<Self> {
+                Some(n as Self)
+            }
+            #[inline]
+            fn from_i32(n: i32) -> Option<Self> {
+                Some(n as Self)
+            }
+            #[inline]
+            fn from_i64(n: i64) -> Option<Self> {
+                Some(n as Self)
+            }
+            #[inline]
+            fn from_u8(n: u8) -> Option<Self> {
+                Some(n as Self)
+            }
+            #[inline]
+            fn from_u16(n: u16) -> Option<Self> {
+                Some(n as Self)
+            }
+            #[inline]
+            fn from_u32(n: u32) -> Option<Self> {
+                Some(n as Self)
+            }
+            #[inline]
+            fn from_u64(n: u64) -> Option<Self> {
+                Some(n as Self)
+            }
         }
-    )
+    };
 }
 
 impl_from_primitive_for_int!(isize);
@@ -114,3 +178,91 @@ impl_from_primitive_for_uint!(u32);
 impl_from_primitive_for_uint!(u64);
 impl_from_primitive_for_float!(f32);
 impl_from_primitive_for_float!(f64);
+
+serde_if_integer128! {
+    impl FromPrimitive for i128 {
+        #[inline]
+        fn from_i8(n: i8) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_i16(n: i16) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_i32(n: i32) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_i64(n: i64) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u8(n: u8) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u16(n: u16) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u32(n: u32) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u64(n: u64) -> Option<Self> {
+            Some(n as i128)
+        }
+    }
+
+    impl FromPrimitive for u128 {
+        #[inline]
+        fn from_i8(n: i8) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_i16(n: i16) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_i32(n: i32) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_i64(n: i64) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_u8(n: u8) -> Option<Self> {
+            Some(n as u128)
+        }
+        #[inline]
+        fn from_u16(n: u16) -> Option<Self> {
+            Some(n as u128)
+        }
+        #[inline]
+        fn from_u32(n: u32) -> Option<Self> {
+            Some(n as u128)
+        }
+        #[inline]
+        fn from_u64(n: u64) -> Option<Self> {
+            Some(n as u128)
+        }
+    }
+}

serde/src/de/ignored_any.rs

@@ -45,7 +45,8 @@ use de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
 /// }
 ///
 /// impl<'de, T> Visitor<'de> for NthElement<T>
-///     where T: Deserialize<'de>
+/// where
+///     T: Deserialize<'de>,
 /// {
 ///     type Value = T;
 ///
@@ -54,7 +55,8 @@ use de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
 ///     }
 ///
 ///     fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
-///         where A: SeqAccess<'de>
+///     where
+///         A: SeqAccess<'de>,
 ///     {
 ///         // Skip over the first `n` elements.
 ///         for i in 0..self.n {
@@ -82,19 +84,22 @@ use de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
 /// }
 ///
 /// impl<'de, T> DeserializeSeed<'de> for NthElement<T>
-///     where T: Deserialize<'de>
+/// where
+///     T: Deserialize<'de>,
 /// {
 ///     type Value = T;
 ///
 ///     fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
-///         where D: Deserializer<'de>
+///     where
+///         D: Deserializer<'de>,
 ///     {
 ///         deserializer.deserialize_seq(self)
 ///     }
 /// }
 ///
 /// # fn example<'de, D>(deserializer: D) -> Result<(), D::Error>
-/// #     where D: Deserializer<'de>
+/// # where
+/// #     D: Deserializer<'de>,
 /// # {
 /// // Deserialize only the sequence element at index 3 from this deserializer.
 /// // The element at index 3 is required to be a string. Elements before and

serde/src/de/mod.rs

@@ -52,12 +52,12 @@
 //!
 //!  - **Primitive types**:
 //!    - bool
-//!    - i8, i16, i32, i64, isize
-//!    - u8, u16, u32, u64, usize
+//!    - i8, i16, i32, i64, i128, isize
+//!    - u8, u16, u32, u64, u128, usize
 //!    - f32, f64
 //!    - char
 //!  - **Compound types**:
-//!    - [T; 0] through [T; 32]
+//!    - \[T; 0\] through \[T; 32\]
 //!    - tuples up to size 16
 //!  - **Common standard library types**:
 //!    - String
@@ -66,7 +66,7 @@
 //!    - PhantomData\<T\>
 //!  - **Wrapper types**:
 //!    - Box\<T\>
-//!    - Box\<[T]\>
+//!    - Box\<\[T\]\>
 //!    - Box\<str\>
 //!    - Rc\<T\>
 //!    - Arc\<T\>
@@ -84,10 +84,9 @@
 //!    - LinkedList\<T\>
 //!    - VecDeque\<T\>
 //!    - Vec\<T\>
-//!    - EnumSet\<T\> (unstable)
 //!  - **Zero-copy types**:
 //!    - &str
-//!    - &[u8]
+//!    - &\[u8\]
 //!  - **FFI types**:
 //!    - CString
 //!    - Box\<CStr\>
@@ -98,7 +97,8 @@
 //!    - Path
 //!    - PathBuf
 //!    - Range\<T\>
-//!    - NonZero\<T\> (unstable)
+//!    - num::NonZero*
+//!    - `!` *(unstable)*
 //!  - **Net types**:
 //!    - IpAddr
 //!    - Ipv4Addr
@@ -149,6 +149,13 @@ macro_rules! declare_error_trait {
         ///
         /// Most deserializers should only need to provide the `Error::custom` method
         /// and inherit the default behavior for the other methods.
+        ///
+        /// # Example implementation
+        ///
+        /// The [example data format] presented on the website shows an error
+        /// type appropriate for a basic JSON data format.
+        ///
+        /// [example data format]: https://serde.rs/data-format.html
         pub trait Error: Sized $(+ $($supertrait)::+)* {
             /// Raised when there is general error when deserializing a type.
             ///
@@ -171,7 +178,8 @@ macro_rules! declare_error_trait {
             ///
             /// impl<'de> Deserialize<'de> for IpAddr {
             ///     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-            ///         where D: Deserializer<'de>
+            ///     where
+            ///         D: Deserializer<'de>,
             ///     {
             ///         let s = try!(String::deserialize(deserializer));
             ///         s.parse().map_err(de::Error::custom)
@@ -195,6 +203,7 @@ macro_rules! declare_error_trait {
             /// For example if we try to deserialize a String out of a JSON file
             /// containing an integer, the unexpected type is the integer and the
             /// expected type is the string.
+            #[cold]
             fn invalid_type(unexp: Unexpected, exp: &Expected) -> Self {
                 Error::custom(format_args!("invalid type: {}, expected {}", unexp, exp))
             }
@@ -212,6 +221,7 @@ macro_rules! declare_error_trait {
             /// For example if we try to deserialize a String out of some binary data
             /// that is not valid UTF-8, the unexpected value is the bytes and the
             /// expected value is a string.
+            #[cold]
             fn invalid_value(unexp: Unexpected, exp: &Expected) -> Self {
                 Error::custom(format_args!("invalid value: {}, expected {}", unexp, exp))
             }
@@ -225,12 +235,14 @@ macro_rules! declare_error_trait {
             /// The `exp` argument provides information about what data was being
             /// expected. For example `exp` might say that a tuple of size 6 was
             /// expected.
+            #[cold]
             fn invalid_length(len: usize, exp: &Expected) -> Self {
                 Error::custom(format_args!("invalid length {}, expected {}", len, exp))
             }
 
             /// Raised when a `Deserialize` enum type received a variant with an
             /// unrecognized name.
+            #[cold]
             fn unknown_variant(variant: &str, expected: &'static [&'static str]) -> Self {
                 if expected.is_empty() {
                     Error::custom(format_args!("unknown variant `{}`, there are no variants",
@@ -244,6 +256,7 @@ macro_rules! declare_error_trait {
 
             /// Raised when a `Deserialize` struct type received a field with an
             /// unrecognized name.
+            #[cold]
             fn unknown_field(field: &str, expected: &'static [&'static str]) -> Self {
                 if expected.is_empty() {
                     Error::custom(format_args!("unknown field `{}`, there are no fields",
@@ -258,12 +271,14 @@ macro_rules! declare_error_trait {
             /// Raised when a `Deserialize` struct type expected to receive a required
             /// field with a particular name but that field was not present in the
             /// input.
+            #[cold]
             fn missing_field(field: &'static str) -> Self {
                 Error::custom(format_args!("missing field `{}`", field))
             }
 
             /// Raised when a `Deserialize` struct type received more than one of the
             /// same field.
+            #[cold]
             fn duplicate_field(field: &'static str) -> Self {
                 Error::custom(format_args!("duplicate field `{}`", field))
             }
@@ -298,7 +313,8 @@ declare_error_trait!(Error: Sized + Debug + Display);
 /// #     }
 /// #
 /// fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E>
-///     where E: de::Error
+/// where
+///     E: de::Error,
 /// {
 ///     Err(de::Error::invalid_type(Unexpected::Bool(v), &self))
 /// }
@@ -422,7 +438,8 @@ impl<'a> fmt::Display for Unexpected<'a> {
 /// #     }
 /// #
 /// fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E>
-///     where E: de::Error
+/// where
+///     E: de::Error,
 /// {
 ///     Err(de::Error::invalid_type(Unexpected::Bool(v), &self))
 /// }
@@ -435,7 +452,8 @@ impl<'a> fmt::Display for Unexpected<'a> {
 /// # use serde::de::{self, Unexpected};
 /// #
 /// # fn example<E>() -> Result<(), E>
-/// #     where E: de::Error
+/// # where
+/// #     E: de::Error,
 /// # {
 /// #     let v = true;
 /// return Err(de::Error::invalid_type(Unexpected::Bool(v), &"a negative integer"));
@@ -494,6 +512,14 @@ impl<'a> Display for Expected + 'a {
 /// [de]: https://docs.serde.rs/serde/de/index.html
 /// [codegen]: https://serde.rs/codegen.html
 /// [impl-deserialize]: https://serde.rs/impl-deserialize.html
+///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed by `Self` when deserialized. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
 pub trait Deserialize<'de>: Sized {
     /// Deserialize this value from the given Serde deserializer.
     ///
@@ -549,19 +575,25 @@ pub trait Deserialize<'de>: Sized {
 /// #
 /// # trait Ignore {
 /// fn from_str<'a, T>(s: &'a str) -> Result<T>
-///     where T: Deserialize<'a>;
+/// where
+///     T: Deserialize<'a>;
 ///
 /// fn from_reader<R, T>(rdr: R) -> Result<T>
-///     where R: Read,
-///           T: DeserializeOwned;
+/// where
+///     R: Read,
+///     T: DeserializeOwned;
 /// # }
 /// ```
+///
+/// # Lifetime
+///
+/// The relationship between `Deserialize` and `DeserializeOwned` in trait
+/// bounds is explained in more detail on the page [Understanding deserializer
+/// lifetimes].
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
 pub trait DeserializeOwned: for<'de> Deserialize<'de> {}
-impl<T> DeserializeOwned for T
-where
-    T: for<'de> Deserialize<'de>,
-{
-}
+impl<T> DeserializeOwned for T where T: for<'de> Deserialize<'de> {}
 
 /// `DeserializeSeed` is the stateful form of the `Deserialize` trait. If you
 /// ever find yourself looking for a way to pass data into a `Deserialize` impl,
@@ -606,6 +638,14 @@ where
 /// seed can be appeased by passing `std::marker::PhantomData` as a seed in the
 /// case of stateless deserialization.
 ///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed by `Self::Value` when deserialized. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
 /// # Example
 ///
 /// Suppose we have JSON that looks like `[[1, 2], [3, 4, 5], [6]]` and we need
@@ -629,7 +669,8 @@ where
 /// struct ExtendVec<'a, T: 'a>(&'a mut Vec<T>);
 ///
 /// impl<'de, 'a, T> DeserializeSeed<'de> for ExtendVec<'a, T>
-///     where T: Deserialize<'de>
+/// where
+///     T: Deserialize<'de>,
 /// {
 ///     // The return type of the `deserialize` method. This implementation
 ///     // appends onto an existing vector but does not create any new data
@@ -637,14 +678,16 @@ where
 ///     type Value = ();
 ///
 ///     fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
-///         where D: Deserializer<'de>
+///     where
+///         D: Deserializer<'de>,
 ///     {
 ///         // Visitor implementation that will walk an inner array of the JSON
 ///         // input.
 ///         struct ExtendVecVisitor<'a, T: 'a>(&'a mut Vec<T>);
 ///
 ///         impl<'de, 'a, T> Visitor<'de> for ExtendVecVisitor<'a, T>
-///             where T: Deserialize<'de>
+///         where
+///             T: Deserialize<'de>,
 ///         {
 ///             type Value = ();
 ///
@@ -653,7 +696,8 @@ where
 ///             }
 ///
 ///             fn visit_seq<A>(self, mut seq: A) -> Result<(), A::Error>
-///                 where A: SeqAccess<'de>
+///             where
+///                 A: SeqAccess<'de>,
 ///             {
 ///                 // Visit each element in the inner array and push it onto
 ///                 // the existing vector.
@@ -672,7 +716,8 @@ where
 /// struct FlattenedVecVisitor<T>(PhantomData<T>);
 ///
 /// impl<'de, T> Visitor<'de> for FlattenedVecVisitor<T>
-///     where T: Deserialize<'de>
+/// where
+///     T: Deserialize<'de>,
 /// {
 ///     // This Visitor constructs a single Vec<T> to hold the flattened
 ///     // contents of the inner arrays.
@@ -683,7 +728,8 @@ where
 ///     }
 ///
 ///     fn visit_seq<A>(self, mut seq: A) -> Result<Vec<T>, A::Error>
-///         where A: SeqAccess<'de>
+///     where
+///         A: SeqAccess<'de>,
 ///     {
 ///         // Create a single Vec to hold the flattened contents.
 ///         let mut vec = Vec::new();
@@ -699,7 +745,8 @@ where
 /// }
 ///
 /// # fn example<'de, D>(deserializer: D) -> Result<(), D::Error>
-/// #     where D: Deserializer<'de>
+/// # where
+/// #     D: Deserializer<'de>,
 /// # {
 /// let visitor = FlattenedVecVisitor(PhantomData);
 /// let flattened: Vec<u64> = deserializer.deserialize_seq(visitor)?;
@@ -737,10 +784,10 @@ where
 /// A **data format** that can deserialize any data structure supported by
 /// Serde.
 ///
-/// The role of this trait is to define the deserialization half of the Serde
-/// data model, which is a way to categorize every Rust data type into one of 27
-/// possible types. Each method of the `Serializer` trait corresponds to one of
-/// the types of the data model.
+/// The role of this trait is to define the deserialization half of the [Serde
+/// data model], which is a way to categorize every Rust data type into one of
+/// 29 possible types. Each method of the `Serializer` trait corresponds to one
+/// of the types of the data model.
 ///
 /// Implementations of `Deserialize` map themselves into this data model by
 /// passing to the `Deserializer` a `Visitor` implementation that can receive
@@ -748,17 +795,17 @@ where
 ///
 /// The types that make up the Serde data model are:
 ///
-///  - **12 primitive types**
+///  - **14 primitive types**
 ///    - bool
-///    - i8, i16, i32, i64
-///    - u8, u16, u32, u64
+///    - i8, i16, i32, i64, i128
+///    - u8, u16, u32, u64, u128
 ///    - f32, f64
 ///    - char
 ///  - **string**
 ///    - UTF-8 bytes with a length and no null terminator.
 ///    - When serializing, all strings are handled equally. When deserializing,
 ///      there are three flavors of strings: transient, owned, and borrowed.
-///  - **byte array** - [u8]
+///  - **byte array** - \[u8\]
 ///    - Similar to strings, during deserialization byte arrays can be transient,
 ///      owned, or borrowed.
 ///  - **option**
@@ -822,6 +869,23 @@ where
 /// what type is in the input. Know that relying on `Deserializer::deserialize_any`
 /// means your data type will be able to deserialize from self-describing
 /// formats only, ruling out Bincode and many others.
+///
+/// [Serde data model]: https://serde.rs/data-model.html
+///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed from the input when deserializing. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website contains example code for
+/// a basic JSON `Deserializer`.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait Deserializer<'de>: Sized {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -865,6 +929,20 @@ pub trait Deserializer<'de>: Sized {
     where
         V: Visitor<'de>;
 
+    serde_if_integer128! {
+        /// Hint that the `Deserialize` type is expecting an `i128` value.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where
+            V: Visitor<'de>
+        {
+            let _ = visitor;
+            Err(Error::custom("i128 is not supported"))
+        }
+    }
+
     /// Hint that the `Deserialize` type is expecting a `u8` value.
     fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
     where
@@ -885,6 +963,20 @@ pub trait Deserializer<'de>: Sized {
     where
         V: Visitor<'de>;
 
+    serde_if_integer128! {
+        /// Hint that the `Deserialize` type is expecting an `u128` value.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn deserialize_u128<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where
+            V: Visitor<'de>
+        {
+            let _ = visitor;
+            Err(Error::custom("u128 is not supported"))
+        }
+    }
+
     /// Hint that the `Deserialize` type is expecting a `f32` value.
     fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
     where
@@ -1084,7 +1176,8 @@ pub trait Deserializer<'de>: Sized {
     ///
     /// impl<'de> Deserialize<'de> for Timestamp {
     ///     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    ///         where D: Deserializer<'de>
+    ///     where
+    ///         D: Deserializer<'de>,
     ///     {
     ///         if deserializer.is_human_readable() {
     ///             // Deserialize from a human-readable string like "2015-05-15T17:01:00Z".
@@ -1116,6 +1209,16 @@ pub trait Deserializer<'de>: Sized {
 
 /// This trait represents a visitor that walks through a deserializer.
 ///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the requirement for lifetime of data
+/// that may be borrowed by `Self::Value`. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
+/// # Example
+///
 /// ```rust
 /// # use std::fmt;
 /// #
@@ -1135,7 +1238,8 @@ pub trait Deserializer<'de>: Sized {
 ///     }
 ///
 ///     fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
-///         where E: de::Error
+///     where
+///         E: de::Error,
 ///     {
 ///         if s.len() >= self.min {
 ///             Ok(s.to_owned())
@@ -1229,6 +1333,20 @@ pub trait Visitor<'de>: Sized {
         Err(Error::invalid_type(Unexpected::Signed(v), &self))
     }
 
+    serde_if_integer128! {
+        /// The input contains a `i128`.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default implementation fails with a type error.
+        fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
+        where
+            E: Error,
+        {
+            let _ = v;
+            Err(Error::invalid_type(Unexpected::Other("i128"), &self))
+        }
+    }
+
     /// The input contains a `u8`.
     ///
     /// The default implementation forwards to [`visit_u64`].
@@ -1275,6 +1393,20 @@ pub trait Visitor<'de>: Sized {
         Err(Error::invalid_type(Unexpected::Unsigned(v), &self))
     }
 
+    serde_if_integer128! {
+        /// The input contains a `u128`.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default implementation fails with a type error.
+        fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
+        where
+            E: Error,
+        {
+            let _ = v;
+            Err(Error::invalid_type(Unexpected::Other("u128"), &self))
+        }
+    }
+
     /// The input contains an `f32`.
     ///
     /// The default implementation forwards to [`visit_f64`].
@@ -1506,6 +1638,15 @@ pub trait Visitor<'de>: Sized {
         let _ = data;
         Err(Error::invalid_type(Unexpected::Enum, &self))
     }
+
+    // Used when deserializing a flattened Option field. Not public API.
+    #[doc(hidden)]
+    fn __private_visit_untagged_option<D>(self, _: D) -> Result<Self::Value, ()>
+    where
+        D: Deserializer<'de>,
+    {
+        Err(())
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1514,6 +1655,21 @@ pub trait Visitor<'de>: Sized {
 ///
 /// This is a trait that a `Deserializer` passes to a `Visitor` implementation,
 /// which deserializes each item in a sequence.
+///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed by deserialized sequence elements. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SeqAccess` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SeqAccess<'de> {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -1581,6 +1737,21 @@ where
 /// Provides a `Visitor` access to each entry of a map in the input.
 ///
 /// This is a trait that a `Deserializer` passes to a `Visitor` implementation.
+///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed by deserialized map entries. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `MapAccess` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait MapAccess<'de> {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -1758,6 +1929,21 @@ where
 ///
 /// `EnumAccess` is created by the `Deserializer` and passed to the
 /// `Visitor` in order to identify which variant of an enum to deserialize.
+///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed by the deserialized enum variant. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `EnumAccess` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait EnumAccess<'de>: Sized {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -1790,6 +1976,21 @@ pub trait EnumAccess<'de>: Sized {
 /// `VariantAccess` is a visitor that is created by the `Deserializer` and
 /// passed to the `Deserialize` to deserialize the content of a particular enum
 /// variant.
+///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed by the deserialized enum variant. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `VariantAccess` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait VariantAccess<'de>: Sized {
     /// The error type that can be returned if some error occurs during
     /// deserialization. Must match the error type of our `EnumAccess`.
@@ -1815,15 +2016,18 @@ pub trait VariantAccess<'de>: Sized {
     /// }
     /// #
     /// #     fn newtype_variant_seed<T>(self, _: T) -> Result<T::Value, Self::Error>
-    /// #         where T: DeserializeSeed<'de>
+    /// #     where
+    /// #         T: DeserializeSeed<'de>,
     /// #     { unimplemented!() }
     /// #
     /// #     fn tuple_variant<V>(self, _: usize, _: V) -> Result<V::Value, Self::Error>
-    /// #         where V: Visitor<'de>
+    /// #     where
+    /// #         V: Visitor<'de>,
     /// #     { unimplemented!() }
     /// #
     /// #     fn struct_variant<V>(self, _: &[&str], _: V) -> Result<V::Value, Self::Error>
-    /// #         where V: Visitor<'de>
+    /// #     where
+    /// #         V: Visitor<'de>,
     /// #     { unimplemented!() }
     /// # }
     /// ```
@@ -1850,7 +2054,8 @@ pub trait VariantAccess<'de>: Sized {
     /// #     }
     /// #
     /// fn newtype_variant_seed<T>(self, _seed: T) -> Result<T::Value, Self::Error>
-    ///     where T: DeserializeSeed<'de>
+    /// where
+    ///     T: DeserializeSeed<'de>,
     /// {
     ///     // What the data actually contained; suppose it is a unit variant.
     ///     let unexp = Unexpected::UnitVariant;
@@ -1858,11 +2063,13 @@ pub trait VariantAccess<'de>: Sized {
     /// }
     /// #
     /// #     fn tuple_variant<V>(self, _: usize, _: V) -> Result<V::Value, Self::Error>
-    /// #         where V: Visitor<'de>
+    /// #     where
+    /// #         V: Visitor<'de>,
     /// #     { unimplemented!() }
     /// #
     /// #     fn struct_variant<V>(self, _: &[&str], _: V) -> Result<V::Value, Self::Error>
-    /// #         where V: Visitor<'de>
+    /// #     where
+    /// #         V: Visitor<'de>,
     /// #     { unimplemented!() }
     /// # }
     /// ```
@@ -1903,13 +2110,17 @@ pub trait VariantAccess<'de>: Sized {
     /// #     }
     /// #
     /// #     fn newtype_variant_seed<T>(self, _: T) -> Result<T::Value, Self::Error>
-    /// #         where T: DeserializeSeed<'de>
+    /// #     where
+    /// #         T: DeserializeSeed<'de>,
     /// #     { unimplemented!() }
     /// #
-    /// fn tuple_variant<V>(self,
-    ///                         _len: usize,
-    ///                         _visitor: V) -> Result<V::Value, Self::Error>
-    ///     where V: Visitor<'de>
+    /// fn tuple_variant<V>(
+    ///     self,
+    ///     _len: usize,
+    ///     _visitor: V,
+    /// ) -> Result<V::Value, Self::Error>
+    /// where
+    ///     V: Visitor<'de>,
     /// {
     ///     // What the data actually contained; suppose it is a unit variant.
     ///     let unexp = Unexpected::UnitVariant;
@@ -1917,7 +2128,8 @@ pub trait VariantAccess<'de>: Sized {
     /// }
     /// #
     /// #     fn struct_variant<V>(self, _: &[&str], _: V) -> Result<V::Value, Self::Error>
-    /// #         where V: Visitor<'de>
+    /// #     where
+    /// #         V: Visitor<'de>,
     /// #     { unimplemented!() }
     /// # }
     /// ```
@@ -1945,17 +2157,22 @@ pub trait VariantAccess<'de>: Sized {
     /// #     }
     /// #
     /// #     fn newtype_variant_seed<T>(self, _: T) -> Result<T::Value, Self::Error>
-    /// #         where T: DeserializeSeed<'de>
+    /// #     where
+    /// #         T: DeserializeSeed<'de>,
     /// #     { unimplemented!() }
     /// #
     /// #     fn tuple_variant<V>(self, _: usize, _: V) -> Result<V::Value, Self::Error>
-    /// #         where V: Visitor<'de>
+    /// #     where
+    /// #         V: Visitor<'de>,
     /// #     { unimplemented!() }
     /// #
-    /// fn struct_variant<V>(self,
-    ///                          _fields: &'static [&'static str],
-    ///                          _visitor: V) -> Result<V::Value, Self::Error>
-    ///     where V: Visitor<'de>
+    /// fn struct_variant<V>(
+    ///     self,
+    ///     _fields: &'static [&'static str],
+    ///     _visitor: V,
+    /// ) -> Result<V::Value, Self::Error>
+    /// where
+    ///     V: Visitor<'de>,
     /// {
     ///     // What the data actually contained; suppose it is a unit variant.
     ///     let unexp = Unexpected::UnitVariant;
@@ -1977,6 +2194,16 @@ pub trait VariantAccess<'de>: Sized {
 /// Converts an existing value into a `Deserializer` from which other values can
 /// be deserialized.
 ///
+/// # Lifetime
+///
+/// The `'de` lifetime of this trait is the lifetime of data that may be
+/// borrowed from the resulting `Deserializer`. See the page [Understanding
+/// deserializer lifetimes] for a more detailed explanation of these lifetimes.
+///
+/// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+///
+/// # Example
+///
 /// ```rust
 /// #[macro_use]
 /// extern crate serde_derive;

serde/src/de/value.rs

@@ -37,10 +37,26 @@
 
 use lib::*;
 
+use self::private::{First, Second};
 use de::{self, Expected, IntoDeserializer, SeqAccess};
 use private::de::size_hint;
 use ser;
-use self::private::{First, Second};
+
+////////////////////////////////////////////////////////////////////////////////
+
+// For structs that contain a PhantomData. We do not want the trait
+// bound `E: Clone` inferred by derive(Clone).
+macro_rules! impl_copy_clone {
+    ($ty:ident $(<$lifetime:tt>)*) => {
+        impl<$($lifetime,)* E> Copy for $ty<$($lifetime,)* E> {}
+
+        impl<$($lifetime,)* E> Clone for $ty<$($lifetime,)* E> {
+            fn clone(&self) -> Self {
+                *self
+            }
+        }
+    };
+}
 
 ////////////////////////////////////////////////////////////////////////////////
 
@@ -58,6 +74,7 @@ type ErrorImpl = ();
 
 impl de::Error for Error {
     #[cfg(any(feature = "std", feature = "alloc"))]
+    #[cold]
     fn custom<T>(msg: T) -> Self
     where
         T: Display,
@@ -68,6 +85,7 @@ impl de::Error for Error {
     }
 
     #[cfg(not(any(feature = "std", feature = "alloc")))]
+    #[cold]
     fn custom<T>(msg: T) -> Self
     where
         T: Display,
@@ -78,6 +96,7 @@ impl de::Error for Error {
 }
 
 impl ser::Error for Error {
+    #[cold]
     fn custom<T>(msg: T) -> Self
     where
         T: Display,
@@ -121,11 +140,13 @@ where
 }
 
 /// A deserializer holding a `()`.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct UnitDeserializer<E> {
     marker: PhantomData<E>,
 }
 
+impl_copy_clone!(UnitDeserializer);
+
 impl<'de, E> de::Deserializer<'de> for UnitDeserializer<E>
 where
     E: de::Error,
@@ -133,9 +154,9 @@ where
     type Error = E;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf unit unit_struct newtype_struct seq tuple tuple_struct map
-        struct enum identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf unit unit_struct newtype_struct seq tuple tuple_struct
+        map struct enum identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -155,16 +176,60 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
+/// A deserializer that cannot be instantiated.
+#[cfg(feature = "unstable")]
+pub struct NeverDeserializer<E> {
+    never: !,
+    marker: PhantomData<E>,
+}
+
+#[cfg(feature = "unstable")]
+impl<'de, E> IntoDeserializer<'de, E> for !
+where
+    E: de::Error,
+{
+    type Deserializer = NeverDeserializer<E>;
+
+    fn into_deserializer(self) -> Self::Deserializer {
+        self
+    }
+}
+
+#[cfg(feature = "unstable")]
+impl<'de, E> de::Deserializer<'de> for NeverDeserializer<E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        self.never
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 macro_rules! primitive_deserializer {
     ($ty:ty, $doc:tt, $name:ident, $method:ident $($cast:tt)*) => {
         #[doc = "A deserializer holding"]
         #[doc = $doc]
-        #[derive(Clone, Debug)]
+        #[derive(Debug)]
         pub struct $name<E> {
             value: $ty,
             marker: PhantomData<E>
         }
 
+        impl_copy_clone!($name);
+
         impl<'de, E> IntoDeserializer<'de, E> for $ty
         where
             E: de::Error,
@@ -186,9 +251,9 @@ macro_rules! primitive_deserializer {
             type Error = E;
 
             forward_to_deserialize_any! {
-                bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-                byte_buf option unit unit_struct newtype_struct seq tuple
-                tuple_struct map struct enum identifier ignored_any
+                bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str
+                string bytes byte_buf option unit unit_struct newtype_struct seq
+                tuple tuple_struct map struct enum identifier ignored_any
             }
 
             fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -215,13 +280,20 @@ primitive_deserializer!(f32, "an `f32`.", F32Deserializer, visit_f32);
 primitive_deserializer!(f64, "an `f64`.", F64Deserializer, visit_f64);
 primitive_deserializer!(char, "a `char`.", CharDeserializer, visit_char);
 
+serde_if_integer128! {
+    primitive_deserializer!(i128, "an `i128`.", I128Deserializer, visit_i128);
+    primitive_deserializer!(u128, "a `u128`.", U128Deserializer, visit_u128);
+}
+
 /// A deserializer holding a `u32`.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct U32Deserializer<E> {
     value: u32,
     marker: PhantomData<E>,
 }
 
+impl_copy_clone!(U32Deserializer);
+
 impl<'de, E> IntoDeserializer<'de, E> for u32
 where
     E: de::Error,
@@ -243,9 +315,9 @@ where
     type Error = E;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -288,12 +360,14 @@ where
 ////////////////////////////////////////////////////////////////////////////////
 
 /// A deserializer holding a `&str`.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct StrDeserializer<'a, E> {
     value: &'a str,
     marker: PhantomData<E>,
 }
 
+impl_copy_clone!(StrDeserializer<'de>);
+
 impl<'de, 'a, E> IntoDeserializer<'de, E> for &'a str
 where
     E: de::Error,
@@ -336,9 +410,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -361,12 +435,14 @@ where
 
 /// A deserializer holding a `&str` with a lifetime tied to another
 /// deserializer.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct BorrowedStrDeserializer<'de, E> {
     value: &'de str,
     marker: PhantomData<E>,
 }
 
+impl_copy_clone!(BorrowedStrDeserializer<'de>);
+
 impl<'de, E> BorrowedStrDeserializer<'de, E> {
     /// Create a new borrowed deserializer from the given string.
     pub fn new(value: &'de str) -> BorrowedStrDeserializer<'de, E> {
@@ -405,9 +481,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -430,12 +506,22 @@ where
 
 /// A deserializer holding a `String`.
 #[cfg(any(feature = "std", feature = "alloc"))]
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct StringDeserializer<E> {
     value: String,
     marker: PhantomData<E>,
 }
 
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<E> Clone for StringDeserializer<E> {
+    fn clone(&self) -> Self {
+        StringDeserializer {
+            value: self.value.clone(),
+            marker: PhantomData,
+        }
+    }
+}
+
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'de, E> IntoDeserializer<'de, E> for String
 where
@@ -480,9 +566,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -506,12 +592,22 @@ where
 
 /// A deserializer holding a `Cow<str>`.
 #[cfg(any(feature = "std", feature = "alloc"))]
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct CowStrDeserializer<'a, E> {
     value: Cow<'a, str>,
     marker: PhantomData<E>,
 }
 
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'a, E> Clone for CowStrDeserializer<'a, E> {
+    fn clone(&self) -> Self {
+        CowStrDeserializer {
+            value: self.value.clone(),
+            marker: PhantomData,
+        }
+    }
+}
+
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'de, 'a, E> IntoDeserializer<'de, E> for Cow<'a, str>
 where
@@ -559,9 +655,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -585,12 +681,14 @@ where
 
 /// A deserializer holding a `&[u8]` with a lifetime tied to another
 /// deserializer.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct BorrowedBytesDeserializer<'de, E> {
     value: &'de [u8],
     marker: PhantomData<E>,
 }
 
+impl_copy_clone!(BorrowedBytesDeserializer<'de>);
+
 impl<'de, E> BorrowedBytesDeserializer<'de, E> {
     /// Create a new borrowed deserializer from the given byte slice.
     pub fn new(value: &'de [u8]) -> BorrowedBytesDeserializer<'de, E> {
@@ -615,9 +713,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct identifier ignored_any enum
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any enum
     }
 }
 
@@ -652,11 +750,8 @@ where
 {
     /// Check for remaining elements after passing a `SeqDeserializer` to
     /// `Visitor::visit_seq`.
-    pub fn end(mut self) -> Result<(), E> {
-        let mut remaining = 0;
-        while self.iter.next().is_some() {
-            remaining += 1;
-        }
+    pub fn end(self) -> Result<(), E> {
+        let remaining = self.iter.count();
         if remaining == 0 {
             Ok(())
         } else {
@@ -688,9 +783,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct enum identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 
@@ -803,9 +898,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct enum identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 
@@ -849,11 +944,8 @@ where
 {
     /// Check for remaining elements after passing a `MapDeserializer` to
     /// `Visitor::visit_map`.
-    pub fn end(mut self) -> Result<(), E> {
-        let mut remaining = 0;
-        while self.iter.next().is_some() {
-            remaining += 1;
-        }
+    pub fn end(self) -> Result<(), E> {
+        let remaining = self.iter.count();
         if remaining == 0 {
             Ok(())
         } else {
@@ -920,9 +1012,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct tuple_struct map struct
-        enum identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct tuple_struct map
+        struct enum identifier ignored_any
     }
 }
 
@@ -1062,9 +1154,9 @@ where
     type Error = E;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct tuple_struct map struct
-        enum identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct tuple_struct map
+        struct enum identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -1210,9 +1302,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct enum identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 

serde/src/export.rs

@@ -16,6 +16,9 @@ pub use lib::result::Result::{self, Err, Ok};
 
 pub use self::string::from_utf8_lossy;
 
+#[cfg(any(feature = "alloc", feature = "std"))]
+pub use lib::Vec;
+
 mod string {
     use lib::*;
 

serde/src/integer128.rs

@@ -0,0 +1,86 @@
+/// Conditional compilation depending on whether Serde is built with support for
+/// 128-bit integers.
+///
+/// Data formats that wish to support Rust compiler versions older than 1.26 may
+/// place the i128 / u128 methods of their Serializer and Deserializer behind
+/// this macro.
+///
+/// Data formats that require a minimum Rust compiler version of at least 1.26
+/// do not need to bother with this macro and may assume support for 128-bit
+/// integers.
+///
+/// ```rust
+/// #[macro_use]
+/// extern crate serde;
+///
+/// use serde::Serializer;
+/// # use serde::private::ser::Error;
+/// #
+/// # struct MySerializer;
+///
+/// impl Serializer for MySerializer {
+///     type Ok = ();
+///     type Error = Error;
+///
+///     fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error> {
+///         /* ... */
+/// #         unimplemented!()
+///     }
+///
+///     /* ... */
+///
+///     serde_if_integer128! {
+///         fn serialize_i128(self, v: i128) -> Result<Self::Ok, Self::Error> {
+///             /* ... */
+/// #             unimplemented!()
+///         }
+///
+///         fn serialize_u128(self, v: u128) -> Result<Self::Ok, Self::Error> {
+///             /* ... */
+/// #             unimplemented!()
+///         }
+///     }
+/// #
+/// #     __serialize_unimplemented! {
+/// #         bool i8 i16 i32 u8 u16 u32 u64 f32 f64 char str bytes none some
+/// #         unit unit_struct unit_variant newtype_struct newtype_variant seq
+/// #         tuple tuple_struct tuple_variant map struct struct_variant
+/// #     }
+/// }
+/// #
+/// # fn main() {}
+/// ```
+///
+/// When Serde is built with support for 128-bit integers, this macro expands
+/// transparently into just the input tokens.
+///
+/// ```rust
+/// macro_rules! serde_if_integer128 {
+///     ($($tt:tt)*) => {
+///         $($tt)*
+///     };
+/// }
+/// ```
+///
+/// When built without support for 128-bit integers, this macro expands to
+/// nothing.
+///
+/// ```rust
+/// macro_rules! serde_if_integer128 {
+///     ($($tt:tt)*) => {};
+/// }
+/// ```
+#[cfg(integer128)]
+#[macro_export]
+macro_rules! serde_if_integer128 {
+    ($($tt:tt)*) => {
+        $($tt)*
+    };
+}
+
+#[cfg(not(integer128))]
+#[macro_export]
+#[doc(hidden)]
+macro_rules! serde_if_integer128 {
+    ($($tt:tt)*) => {};
+}

serde/src/lib.rs

@@ -52,6 +52,8 @@
 //! - [Pickle], a format common in the Python world.
 //! - [Hjson], a variant of JSON designed to be readable and writable by humans.
 //! - [BSON], the data storage and network transfer format used by MongoDB.
+//! - [Avro], a binary format used within Apache Hadoop, with support for schema
+//!   definition.
 //! - [URL], the x-www-form-urlencoded format.
 //! - [XML], the flexible machine-friendly W3C standard.
 //!   *(deserialization only)*
@@ -69,6 +71,7 @@
 //! [Pickle]: https://github.com/birkenfeld/serde-pickle
 //! [Hjson]: https://github.com/laktak/hjson-rust
 //! [BSON]: https://github.com/zonyitoo/bson-rs
+//! [Avro]: https://github.com/flavray/avro-rs
 //! [URL]: https://github.com/nox/serde_urlencoded
 //! [XML]: https://github.com/RReverser/serde-xml-rs
 //! [Envy]: https://github.com/softprops/envy
@@ -79,21 +82,24 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.34")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.67")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Unstable functionality only if the user asks for it. For tracking and
 // discussion of these features please refer to this issue:
 //
 //    https://github.com/serde-rs/serde/issues/812
-#![cfg_attr(feature = "unstable", feature(nonzero, specialization))]
+#![cfg_attr(feature = "unstable", feature(specialization, never_type))]
 #![cfg_attr(feature = "alloc", feature(alloc))]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
-#![cfg_attr(feature = "cargo-clippy",
-            allow(cast_lossless, const_static_lifetime, doc_markdown, linkedlist,
-                  needless_pass_by_value, redundant_field_names, type_complexity,
-                  unreadable_literal, zero_prefixed_literal))]
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(
+        cast_lossless, const_static_lifetime, doc_markdown, linkedlist, needless_pass_by_value,
+        redundant_field_names, type_complexity, unreadable_literal, zero_prefixed_literal
+    )
+)]
 // Whitelisted clippy_pedantic lints
 #![cfg_attr(feature = "cargo-clippy", allow(
 // integer and float ser/de requires these sorts of casts
@@ -112,6 +118,7 @@
     stutter,
     use_self,
 // not practical
+    indexing_slicing,
     many_single_char_names,
     missing_docs_in_private_items,
     similar_names,
@@ -120,31 +127,31 @@
     use_debug,
 ))]
 // Blacklisted Rust lints.
-#![deny(missing_docs, unused_imports)]
+//
+// Compiler bug involving unused_imports:
+// https://github.com/rust-lang/rust/issues/51661
+#![deny(missing_docs, /*unused_imports*/)]
 
 ////////////////////////////////////////////////////////////////////////////////
 
 #[cfg(feature = "alloc")]
 extern crate alloc;
 
-#[cfg(all(feature = "unstable", feature = "std"))]
-extern crate core;
-
 /// A facade around all the types we need from the `std`, `core`, and `alloc`
 /// crates. This avoids elaborate import wrangling having to happen in every
 /// module.
 mod lib {
     mod core {
-        #[cfg(feature = "std")]
-        pub use std::*;
         #[cfg(not(feature = "std"))]
         pub use core::*;
+        #[cfg(feature = "std")]
+        pub use std::*;
     }
 
-    pub use self::core::{cmp, iter, mem, ops, slice, str};
-    pub use self::core::{isize, i16, i32, i64, i8};
-    pub use self::core::{usize, u16, u32, u64, u8};
+    pub use self::core::{cmp, iter, mem, num, ops, slice, str};
     pub use self::core::{f32, f64};
+    pub use self::core::{i16, i32, i64, i8, isize};
+    pub use self::core::{u16, u32, u64, u8, usize};
 
     pub use self::core::cell::{Cell, RefCell};
     pub use self::core::clone::{self, Clone};
@@ -155,40 +162,40 @@ mod lib {
     pub use self::core::option::{self, Option};
     pub use self::core::result::{self, Result};
 
-    #[cfg(feature = "std")]
-    pub use std::borrow::{Cow, ToOwned};
     #[cfg(all(feature = "alloc", not(feature = "std")))]
     pub use alloc::borrow::{Cow, ToOwned};
-
     #[cfg(feature = "std")]
-    pub use std::string::String;
+    pub use std::borrow::{Cow, ToOwned};
+
     #[cfg(all(feature = "alloc", not(feature = "std")))]
     pub use alloc::string::{String, ToString};
-
     #[cfg(feature = "std")]
-    pub use std::vec::Vec;
+    pub use std::string::String;
+
     #[cfg(all(feature = "alloc", not(feature = "std")))]
     pub use alloc::vec::Vec;
-
     #[cfg(feature = "std")]
-    pub use std::boxed::Box;
+    pub use std::vec::Vec;
+
     #[cfg(all(feature = "alloc", not(feature = "std")))]
     pub use alloc::boxed::Box;
-
-    #[cfg(all(feature = "rc", feature = "std"))]
-    pub use std::rc::Rc;
-    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
-    pub use alloc::rc::Rc;
-
-    #[cfg(all(feature = "rc", feature = "std"))]
-    pub use std::sync::Arc;
-    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
-    pub use alloc::arc::Arc;
-
     #[cfg(feature = "std")]
-    pub use std::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
+    pub use std::boxed::Box;
+
+    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
+    pub use alloc::rc::{Rc, Weak as RcWeak};
+    #[cfg(all(feature = "rc", feature = "std"))]
+    pub use std::rc::{Rc, Weak as RcWeak};
+
+    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
+    pub use alloc::arc::{Arc, Weak as ArcWeak};
+    #[cfg(all(feature = "rc", feature = "std"))]
+    pub use std::sync::{Arc, Weak as ArcWeak};
+
     #[cfg(all(feature = "alloc", not(feature = "std")))]
     pub use alloc::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
+    #[cfg(feature = "std")]
+    pub use std::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
 
     #[cfg(feature = "std")]
     pub use std::{error, net};
@@ -206,12 +213,12 @@ mod lib {
     #[cfg(feature = "std")]
     pub use std::path::{Path, PathBuf};
     #[cfg(feature = "std")]
-    pub use std::time::{Duration, SystemTime, UNIX_EPOCH};
-    #[cfg(feature = "std")]
     pub use std::sync::{Mutex, RwLock};
+    #[cfg(feature = "std")]
+    pub use std::time::{SystemTime, UNIX_EPOCH};
 
-    #[cfg(feature = "unstable")]
-    pub use core::nonzero::{NonZero, Zeroable};
+    #[cfg(any(core_duration, feature = "std"))]
+    pub use self::core::time::Duration;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -219,13 +226,16 @@ mod lib {
 #[macro_use]
 mod macros;
 
-pub mod ser;
+#[macro_use]
+mod integer128;
+
 pub mod de;
+pub mod ser;
 
-#[doc(inline)]
-pub use ser::{Serialize, Serializer};
 #[doc(inline)]
 pub use de::{Deserialize, Deserializer};
+#[doc(inline)]
+pub use ser::{Serialize, Serializer};
 
 // Generated code uses these to support no_std. Not public API.
 #[doc(hidden)]

serde/src/macros.rs

@@ -31,21 +31,23 @@
 /// #     type Error = value::Error;
 /// #
 /// #     fn deserialize_any<V>(self, _: V) -> Result<V::Value, Self::Error>
-/// #         where V: Visitor<'de>
+/// #     where
+/// #         V: Visitor<'de>,
 /// #     {
 /// #         unimplemented!()
 /// #     }
 /// #
 /// #[inline]
 /// fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value, Self::Error>
-///     where V: Visitor<'de>
+/// where
+///     V: Visitor<'de>,
 /// {
 ///     self.deserialize_any(visitor)
 /// }
 /// #
 /// #     forward_to_deserialize_any! {
-/// #         i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-/// #         byte_buf option unit unit_struct newtype_struct seq tuple
+/// #         i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+/// #         bytes byte_buf option unit unit_struct newtype_struct seq tuple
 /// #         tuple_struct map struct enum identifier ignored_any
 /// #     }
 /// # }
@@ -69,7 +71,8 @@
 /// #   type Error = value::Error;
 /// #
 ///     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
-///         where V: Visitor<'de>
+///     where
+///         V: Visitor<'de>,
 ///     {
 ///         /* ... */
 /// #       let _ = visitor;
@@ -77,8 +80,8 @@
 ///     }
 ///
 ///     forward_to_deserialize_any! {
-///         bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-///         byte_buf option unit unit_struct newtype_struct seq tuple
+///         bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+///         bytes byte_buf option unit unit_struct newtype_struct seq tuple
 ///         tuple_struct map struct enum identifier ignored_any
 ///     }
 /// }
@@ -105,16 +108,17 @@
 /// #     type Error = value::Error;
 /// #
 /// #     fn deserialize_any<W>(self, visitor: W) -> Result<W::Value, Self::Error>
-/// #         where W: Visitor<'q>
+/// #     where
+/// #         W: Visitor<'q>,
 /// #     {
 /// #         unimplemented!()
 /// #     }
 /// #
 /// forward_to_deserialize_any! {
 ///     <W: Visitor<'q>>
-///     bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-///     byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-///     map struct enum identifier ignored_any
+///     bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+///     bytes byte_buf option unit unit_struct newtype_struct seq tuple
+///     tuple_struct map struct enum identifier ignored_any
 /// }
 /// # }
 /// #
@@ -170,6 +174,11 @@ macro_rules! forward_to_deserialize_any_helper {
     (i64<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_i64<$l, $v>()}
     };
+    (i128<$l:tt, $v:ident>) => {
+        serde_if_integer128! {
+            forward_to_deserialize_any_method!{deserialize_i128<$l, $v>()}
+        }
+    };
     (u8<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_u8<$l, $v>()}
     };
@@ -182,6 +191,11 @@ macro_rules! forward_to_deserialize_any_helper {
     (u64<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_u64<$l, $v>()}
     };
+    (u128<$l:tt, $v:ident>) => {
+        serde_if_integer128! {
+            forward_to_deserialize_any_method!{deserialize_u128<$l, $v>()}
+        }
+    };
     (f32<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_f32<$l, $v>()}
     };

serde/src/private/mod.rs

@@ -8,5 +8,5 @@
 
 mod macros;
 
-pub mod ser;
 pub mod de;
+pub mod ser;

serde/src/private/ser.rs

@@ -12,10 +12,7 @@ use ser::{self, Impossible, Serialize, SerializeMap, SerializeStruct, Serializer
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 use self::content::{
-    SerializeStructVariantAsMapValue,
-    SerializeTupleVariantAsMapValue,
-    ContentSerializer,
-    Content,
+    Content, ContentSerializer, SerializeStructVariantAsMapValue, SerializeTupleVariantAsMapValue,
 };
 
 /// Used to check that serde(getter) attributes return the expected type.
@@ -950,7 +947,8 @@ mod content {
         where
             T: Serialize,
         {
-            let key = self.key
+            let key = self
+                .key
                 .take()
                 .expect("serialize_value called before serialize_key");
             let value = try!(value.serialize(ContentSerializer::<E>::new()));
@@ -1042,16 +1040,20 @@ pub struct FlatMapSerializer<'a, M: 'a>(pub &'a mut M);
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, M> FlatMapSerializer<'a, M>
 where
-    M: SerializeMap + 'a
+    M: SerializeMap + 'a,
 {
     fn bad_type(self, what: Unsupported) -> M::Error {
-        ser::Error::custom(format_args!("can only flatten structs and maps (got {})", what))
+        ser::Error::custom(format_args!(
+            "can only flatten structs and maps (got {})",
+            what
+        ))
     }
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, M> Serializer for FlatMapSerializer<'a, M>
-    where M: SerializeMap + 'a
+where
+    M: SerializeMap + 'a,
 {
     type Ok = ();
     type Error = M::Error;
@@ -1121,14 +1123,14 @@ impl<'a, M> Serializer for FlatMapSerializer<'a, M>
     }
 
     fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
-        Err(self.bad_type(Unsupported::Optional))
+        Ok(())
     }
 
-    fn serialize_some<T: ?Sized>(self, _: &T) -> Result<Self::Ok, Self::Error>
+    fn serialize_some<T: ?Sized>(self, value: &T) -> Result<Self::Ok, Self::Error>
     where
         T: Serialize,
     {
-        Err(self.bad_type(Unsupported::Optional))
+        value.serialize(self)
     }
 
     fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
@@ -1219,7 +1221,10 @@ impl<'a, M> Serializer for FlatMapSerializer<'a, M>
         _: usize,
     ) -> Result<Self::SerializeStructVariant, Self::Error> {
         try!(self.0.serialize_key(inner_variant));
-        Ok(FlatMapSerializeStructVariantAsMapValue::new(self.0, inner_variant))
+        Ok(FlatMapSerializeStructVariantAsMapValue::new(
+            self.0,
+            inner_variant,
+        ))
     }
 }
 
@@ -1228,7 +1233,8 @@ pub struct FlatMapSerializeMap<'a, M: 'a>(&'a mut M);
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, M> ser::SerializeMap for FlatMapSerializeMap<'a, M>
-    where M: SerializeMap + 'a
+where
+    M: SerializeMap + 'a,
 {
     type Ok = ();
     type Error = M::Error;
@@ -1257,12 +1263,17 @@ pub struct FlatMapSerializeStruct<'a, M: 'a>(&'a mut M);
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, M> ser::SerializeStruct for FlatMapSerializeStruct<'a, M>
-    where M: SerializeMap + 'a
+where
+    M: SerializeMap + 'a,
 {
     type Ok = ();
     type Error = M::Error;
 
-    fn serialize_field<T: ?Sized>(&mut self, key: &'static str, value: &T) -> Result<(), Self::Error>
+    fn serialize_field<T: ?Sized>(
+        &mut self,
+        key: &'static str,
+        value: &T,
+    ) -> Result<(), Self::Error>
     where
         T: Serialize,
     {
@@ -1283,7 +1294,8 @@ pub struct FlatMapSerializeStructVariantAsMapValue<'a, M: 'a> {
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, M> FlatMapSerializeStructVariantAsMapValue<'a, M>
-    where M: SerializeMap + 'a
+where
+    M: SerializeMap + 'a,
 {
     fn new(map: &'a mut M, name: &'static str) -> FlatMapSerializeStructVariantAsMapValue<'a, M> {
         FlatMapSerializeStructVariantAsMapValue {
@@ -1296,12 +1308,17 @@ impl<'a, M> FlatMapSerializeStructVariantAsMapValue<'a, M>
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, M> ser::SerializeStructVariant for FlatMapSerializeStructVariantAsMapValue<'a, M>
-    where M: SerializeMap + 'a
+where
+    M: SerializeMap + 'a,
 {
     type Ok = ();
     type Error = M::Error;
 
-    fn serialize_field<T: ?Sized>(&mut self, key: &'static str, value: &T) -> Result<(), Self::Error>
+    fn serialize_field<T: ?Sized>(
+        &mut self,
+        key: &'static str,
+        value: &T,
+    ) -> Result<(), Self::Error>
     where
         T: Serialize,
     {
@@ -1311,7 +1328,10 @@ impl<'a, M> ser::SerializeStructVariant for FlatMapSerializeStructVariantAsMapVa
     }
 
     fn end(self) -> Result<(), Self::Error> {
-        try!(self.map.serialize_value(&Content::Struct(self.name, self.fields)));
+        try!(
+            self.map
+                .serialize_value(&Content::Struct(self.name, self.fields))
+        );
         Ok(())
     }
 }

serde/src/ser/impls.rs

@@ -8,10 +8,7 @@
 
 use lib::*;
 
-use ser::{Serialize, SerializeTuple, Serializer};
-
-#[cfg(feature = "std")]
-use ser::Error;
+use ser::{Error, Serialize, SerializeTuple, Serializer};
 
 ////////////////////////////////////////////////////////////////////////////////
 
@@ -44,6 +41,11 @@ primitive_impl!(f32, serialize_f32);
 primitive_impl!(f64, serialize_f64);
 primitive_impl!(char, serialize_char);
 
+serde_if_integer128! {
+    primitive_impl!(i128, serialize_i128);
+    primitive_impl!(u128, serialize_u128);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 impl Serialize for str {
@@ -67,6 +69,15 @@ impl Serialize for String {
     }
 }
 
+impl<'a> Serialize for fmt::Arguments<'a> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.collect_str(self)
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 #[cfg(feature = "std")]
@@ -245,6 +256,16 @@ impl Serialize for () {
     }
 }
 
+#[cfg(feature = "unstable")]
+impl Serialize for ! {
+    fn serialize<S>(&self, _serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        *self
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 macro_rules! tuple_impls {
@@ -320,8 +341,12 @@ map_impl!(HashMap<K: Eq + Hash, V, H: BuildHasher>);
 ////////////////////////////////////////////////////////////////////////////////
 
 macro_rules! deref_impl {
-    ($($desc:tt)+) => {
-        impl $($desc)+ {
+    (
+        $(#[doc = $doc:tt])*
+        <$($desc:tt)+
+    ) => {
+        $(#[doc = $doc])*
+        impl <$($desc)+ {
             #[inline]
             fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where
@@ -340,29 +365,96 @@ deref_impl!(<'a, T: ?Sized> Serialize for &'a mut T where T: Serialize);
 deref_impl!(<T: ?Sized> Serialize for Box<T> where T: Serialize);
 
 #[cfg(all(feature = "rc", any(feature = "std", feature = "alloc")))]
-deref_impl!(<T: ?Sized> Serialize for Rc<T> where T: Serialize);
+deref_impl! {
+    /// This impl requires the [`"rc"`] Cargo feature of Serde.
+    ///
+    /// Serializing a data structure containing `Rc` will serialize a copy of
+    /// the contents of the `Rc` each time the `Rc` is referenced within the
+    /// data structure. Serialization will not attempt to deduplicate these
+    /// repeated data.
+    ///
+    /// [`"rc"`]: https://serde.rs/feature-flags.html#-features-rc
+    <T: ?Sized> Serialize for Rc<T> where T: Serialize
+}
 
 #[cfg(all(feature = "rc", any(feature = "std", feature = "alloc")))]
-deref_impl!(<T: ?Sized> Serialize for Arc<T> where T: Serialize);
+deref_impl! {
+    /// This impl requires the [`"rc"`] Cargo feature of Serde.
+    ///
+    /// Serializing a data structure containing `Arc` will serialize a copy of
+    /// the contents of the `Arc` each time the `Arc` is referenced within the
+    /// data structure. Serialization will not attempt to deduplicate these
+    /// repeated data.
+    ///
+    /// [`"rc"`]: https://serde.rs/feature-flags.html#-features-rc
+    <T: ?Sized> Serialize for Arc<T> where T: Serialize
+}
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 deref_impl!(<'a, T: ?Sized> Serialize for Cow<'a, T> where T: Serialize + ToOwned);
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "unstable")]
-impl<T> Serialize for NonZero<T>
+/// This impl requires the [`"rc"`] Cargo feature of Serde.
+///
+/// [`"rc"`]: https://serde.rs/feature-flags.html#-features-rc
+#[cfg(all(feature = "rc", any(feature = "std", feature = "alloc")))]
+impl<T: ?Sized> Serialize for RcWeak<T>
 where
-    T: Serialize + Zeroable + Clone,
+    T: Serialize,
 {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
         S: Serializer,
     {
-        self.clone().get().serialize(serializer)
+        self.upgrade().serialize(serializer)
     }
 }
 
+/// This impl requires the [`"rc"`] Cargo feature of Serde.
+///
+/// [`"rc"`]: https://serde.rs/feature-flags.html#-features-rc
+#[cfg(all(feature = "rc", any(feature = "std", feature = "alloc")))]
+impl<T: ?Sized> Serialize for ArcWeak<T>
+where
+    T: Serialize,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        self.upgrade().serialize(serializer)
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+macro_rules! nonzero_integers {
+    ( $( $T: ident, )+ ) => {
+        $(
+            #[cfg(num_nonzero)]
+            impl Serialize for num::$T {
+                fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+                where
+                    S: Serializer,
+                {
+                    self.get().serialize(serializer)
+                }
+            }
+        )+
+    }
+}
+
+nonzero_integers! {
+    // Not including signed NonZeroI* since they might be removed
+    NonZeroU8,
+    NonZeroU16,
+    NonZeroU32,
+    NonZeroU64,
+    // FIXME: https://github.com/serde-rs/serde/issues/1136 NonZeroU128,
+    NonZeroUsize,
+}
+
 impl<T> Serialize for Cell<T>
 where
     T: Serialize + Copy,
@@ -383,7 +475,10 @@ where
     where
         S: Serializer,
     {
-        self.borrow().serialize(serializer)
+        match self.try_borrow() {
+            Ok(value) => value.serialize(serializer),
+            Err(_) => Err(S::Error::custom("already mutably borrowed")),
+        }
     }
 }
 
@@ -441,7 +536,7 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "std")]
+#[cfg(any(core_duration, feature = "std"))]
 impl Serialize for Duration {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -464,7 +559,8 @@ impl Serialize for SystemTime {
         S: Serializer,
     {
         use super::SerializeStruct;
-        let duration_since_epoch = self.duration_since(UNIX_EPOCH)
+        let duration_since_epoch = self
+            .duration_since(UNIX_EPOCH)
             .expect("SystemTime must be later than UNIX_EPOCH");
         let mut state = try!(serializer.serialize_struct("SystemTime", 2));
         try!(state.serialize_field("secs_since_epoch", &duration_since_epoch.as_secs()));
@@ -494,11 +590,9 @@ macro_rules! serialize_display_bounded_length {
         // write! only provides fmt::Formatter to Display implementations, which
         // has methods write_str and write_char but no method to write arbitrary
         // bytes. Therefore `written` must be valid UTF-8.
-        let written_str = unsafe {
-            str::from_utf8_unchecked(written)
-        };
+        let written_str = unsafe { str::from_utf8_unchecked(written) };
         $serializer.serialize_str(written_str)
-    }}
+    }};
 }
 
 #[cfg(feature = "std")]

serde/src/ser/impossible.rs

@@ -10,8 +10,10 @@
 
 use lib::*;
 
-use ser::{self, Serialize, SerializeMap, SerializeSeq, SerializeStruct, SerializeStructVariant,
-          SerializeTuple, SerializeTupleStruct, SerializeTupleVariant};
+use ser::{
+    self, Serialize, SerializeMap, SerializeSeq, SerializeStruct, SerializeStructVariant,
+    SerializeTuple, SerializeTupleStruct, SerializeTupleVariant,
+};
 
 /// Helper type for implementing a `Serializer` that does not support
 /// serializing one of the compound types.

serde/src/ser/mod.rs

@@ -48,15 +48,15 @@
 //!
 //!  - **Primitive types**:
 //!    - bool
-//!    - i8, i16, i32, i64, isize
-//!    - u8, u16, u32, u64, usize
+//!    - i8, i16, i32, i64, i128, isize
+//!    - u8, u16, u32, u64, u128, usize
 //!    - f32, f64
 //!    - char
 //!    - str
 //!    - &T and &mut T
 //!  - **Compound types**:
-//!    - [T]
-//!    - [T; 0] through [T; 32]
+//!    - \[T\]
+//!    - \[T; 0\] through \[T; 32\]
 //!    - tuples up to size 16
 //!  - **Common standard library types**:
 //!    - String
@@ -81,7 +81,6 @@
 //!    - LinkedList\<T\>
 //!    - VecDeque\<T\>
 //!    - Vec\<T\>
-//!    - EnumSet\<T\> (unstable)
 //!  - **FFI types**:
 //!    - CStr
 //!    - CString
@@ -93,7 +92,8 @@
 //!    - Path
 //!    - PathBuf
 //!    - Range\<T\>
-//!    - NonZero\<T\> (unstable)
+//!    - num::NonZero*
+//!    - `!` *(unstable)*
 //!  - **Net types**:
 //!    - IpAddr
 //!    - Ipv4Addr
@@ -128,6 +128,13 @@ macro_rules! declare_error_trait {
         /// Trait used by `Serialize` implementations to generically construct
         /// errors belonging to the `Serializer` against which they are
         /// currently running.
+        ///
+        /// # Example implementation
+        ///
+        /// The [example data format] presented on the website shows an error
+        /// type appropriate for a basic JSON data format.
+        ///
+        /// [example data format]: https://serde.rs/data-format.html
         pub trait Error: Sized $(+ $($supertrait)::+)* {
             /// Used when a [`Serialize`] implementation encounters any error
             /// while serializing a type.
@@ -151,7 +158,8 @@ macro_rules! declare_error_trait {
             ///
             /// impl Serialize for Path {
             ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-            ///         where S: Serializer
+            ///     where
+            ///         S: Serializer,
             ///     {
             ///         match self.to_str() {
             ///             Some(s) => serializer.serialize_str(s),
@@ -222,7 +230,8 @@ pub trait Serialize {
     /// // This is what #[derive(Serialize)] would generate.
     /// impl Serialize for Person {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         let mut s = serializer.serialize_struct("Person", 3)?;
     ///         s.serialize_field("name", &self.name)?;
@@ -243,27 +252,27 @@ pub trait Serialize {
 
 /// A **data format** that can serialize any data structure supported by Serde.
 ///
-/// The role of this trait is to define the serialization half of the Serde data
-/// model, which is a way to categorize every Rust data structure into one of 27
-/// possible types. Each method of the `Serializer` trait corresponds to one of
-/// the types of the data model.
+/// The role of this trait is to define the serialization half of the [Serde
+/// data model], which is a way to categorize every Rust data structure into one
+/// of 29 possible types. Each method of the `Serializer` trait corresponds to
+/// one of the types of the data model.
 ///
 /// Implementations of `Serialize` map themselves into this data model by
 /// invoking exactly one of the `Serializer` methods.
 ///
 /// The types that make up the Serde data model are:
 ///
-///  - **12 primitive types**
+///  - **14 primitive types**
 ///    - bool
-///    - i8, i16, i32, i64
-///    - u8, u16, u32, u64
+///    - i8, i16, i32, i64, i128
+///    - u8, u16, u32, u64, u128
 ///    - f32, f64
 ///    - char
 ///  - **string**
 ///    - UTF-8 bytes with a length and no null terminator.
 ///    - When serializing, all strings are handled equally. When deserializing,
 ///      there are three flavors of strings: transient, owned, and borrowed.
-///  - **byte array** - [u8]
+///  - **byte array** - \[u8\]
 ///    - Similar to strings, during deserialization byte arrays can be transient,
 ///      owned, or borrowed.
 ///  - **option**
@@ -308,6 +317,15 @@ pub trait Serialize {
 /// is the `serde_json::value::Serializer` (distinct from the main `serde_json`
 /// serializer) that produces a `serde_json::Value` data structure in memory as
 /// output.
+///
+/// [Serde data model]: https://serde.rs/data-model.html
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website contains example code for
+/// a basic JSON `Serializer`.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait Serializer: Sized {
     /// The output type produced by this `Serializer` during successful
     /// serialization. Most serializers that produce text or binary output
@@ -376,7 +394,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for bool {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_bool(*self)
     ///     }
@@ -402,7 +421,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for i8 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_i8(*self)
     ///     }
@@ -428,7 +448,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for i16 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_i16(*self)
     ///     }
@@ -454,7 +475,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for i32 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_i32(*self)
     ///     }
@@ -476,7 +498,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for i64 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_i64(*self)
     ///     }
@@ -486,6 +509,37 @@ pub trait Serializer: Sized {
     /// ```
     fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error>;
 
+    serde_if_integer128! {
+        /// Serialize an `i128` value.
+        ///
+        /// ```rust
+        /// # #[macro_use]
+        /// # extern crate serde;
+        /// #
+        /// # use serde::Serializer;
+        /// #
+        /// # __private_serialize!();
+        /// #
+        /// impl Serialize for i128 {
+        ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        ///     where
+        ///         S: Serializer,
+        ///     {
+        ///         serializer.serialize_i128(*self)
+        ///     }
+        /// }
+        /// #
+        /// # fn main() {}
+        /// ```
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn serialize_i128(self, v: i128) -> Result<Self::Ok, Self::Error> {
+            let _ = v;
+            Err(Error::custom("i128 is not supported"))
+        }
+    }
+
     /// Serialize a `u8` value.
     ///
     /// If the format does not differentiate between `u8` and `u64`, a
@@ -502,7 +556,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for u8 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_u8(*self)
     ///     }
@@ -528,7 +583,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for u16 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_u16(*self)
     ///     }
@@ -554,7 +610,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for u32 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_u32(*self)
     ///     }
@@ -576,7 +633,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for u64 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_u64(*self)
     ///     }
@@ -586,6 +644,37 @@ pub trait Serializer: Sized {
     /// ```
     fn serialize_u64(self, v: u64) -> Result<Self::Ok, Self::Error>;
 
+    serde_if_integer128! {
+        /// Serialize a `u128` value.
+        ///
+        /// ```rust
+        /// # #[macro_use]
+        /// # extern crate serde;
+        /// #
+        /// # use serde::Serializer;
+        /// #
+        /// # __private_serialize!();
+        /// #
+        /// impl Serialize for u128 {
+        ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        ///     where
+        ///         S: Serializer,
+        ///     {
+        ///         serializer.serialize_u128(*self)
+        ///     }
+        /// }
+        /// #
+        /// # fn main() {}
+        /// ```
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn serialize_u128(self, v: u128) -> Result<Self::Ok, Self::Error> {
+            let _ = v;
+            Err(Error::custom("u128 is not supported"))
+        }
+    }
+
     /// Serialize an `f32` value.
     ///
     /// If the format does not differentiate between `f32` and `f64`, a
@@ -602,7 +691,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for f32 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_f32(*self)
     ///     }
@@ -624,7 +714,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for f64 {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_f64(*self)
     ///     }
@@ -649,7 +740,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for char {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_char(*self)
     ///     }
@@ -671,7 +763,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for str {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_str(self)
     ///     }
@@ -736,10 +829,12 @@ pub trait Serializer: Sized {
     /// # use Option::{Some, None};
     /// #
     /// impl<T> Serialize for Option<T>
-    ///     where T: Serialize
+    /// where
+    ///     T: Serialize,
     /// {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         match *self {
     ///             Some(ref value) => serializer.serialize_some(value),
@@ -769,10 +864,12 @@ pub trait Serializer: Sized {
     /// # use Option::{Some, None};
     /// #
     /// impl<T> Serialize for Option<T>
-    ///     where T: Serialize
+    /// where
+    ///     T: Serialize,
     /// {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         match *self {
     ///             Some(ref value) => serializer.serialize_some(value),
@@ -801,7 +898,8 @@ pub trait Serializer: Sized {
     /// #
     /// impl Serialize for () {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_unit()
     ///     }
@@ -822,7 +920,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for Nothing {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_unit_struct("Nothing")
     ///     }
@@ -846,7 +945,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for E {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         match *self {
     ///             E::A => serializer.serialize_unit_variant("E", 0, "A"),
@@ -875,7 +975,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for Millimeters {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.serialize_newtype_struct("Millimeters", &self.0)
     ///     }
@@ -905,7 +1006,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for E {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         match *self {
     ///             E::M(ref s) => serializer.serialize_newtype_variant("E", 0, "M", s),
@@ -955,10 +1057,12 @@ pub trait Serializer: Sized {
     /// use serde::ser::{Serialize, Serializer, SerializeSeq};
     ///
     /// impl<T> Serialize for Vec<T>
-    ///     where T: Serialize
+    /// where
+    ///     T: Serialize,
     /// {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         let mut seq = serializer.serialize_seq(Some(self.len()))?;
     ///         for element in self {
@@ -987,12 +1091,14 @@ pub trait Serializer: Sized {
     /// # struct Tuple3<A, B, C>(A, B, C);
     /// #
     /// # impl<A, B, C> Serialize for Tuple3<A, B, C>
-    ///     where A: Serialize,
-    ///           B: Serialize,
-    ///           C: Serialize
+    /// where
+    ///     A: Serialize,
+    ///     B: Serialize,
+    ///     C: Serialize,
     /// {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         let mut tup = serializer.serialize_tuple(3)?;
     ///         tup.serialize_element(&self.0)?;
@@ -1011,7 +1117,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for Vram {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         let mut seq = serializer.serialize_tuple(VRAM_SIZE)?;
     ///         for element in &self.0[..] {
@@ -1037,7 +1144,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for Rgb {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         let mut ts = serializer.serialize_tuple_struct("Rgb", 3)?;
     ///         ts.serialize_field(&self.0)?;
@@ -1071,7 +1179,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for E {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         match *self {
     ///             E::T(ref a, ref b) => {
@@ -1129,11 +1238,13 @@ pub trait Serializer: Sized {
     /// use serde::ser::{Serialize, Serializer, SerializeMap};
     ///
     /// impl<K, V> Serialize for HashMap<K, V>
-    ///     where K: Serialize,
-    ///           V: Serialize
+    /// where
+    ///     K: Serialize,
+    ///     V: Serialize,
     /// {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         let mut map = serializer.serialize_map(Some(self.len()))?;
     ///         for (k, v) in self {
@@ -1163,7 +1274,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for Rgb {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         let mut rgb = serializer.serialize_struct("Rgb", 3)?;
     ///         rgb.serialize_field("r", &self.r)?;
@@ -1196,7 +1308,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for E {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         match *self {
     ///             E::S { ref r, ref g, ref b } => {
@@ -1233,7 +1346,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for SecretlyOneHigher {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.collect_seq(self.data.iter().map(|x| x + 1))
     ///     }
@@ -1271,7 +1385,8 @@ pub trait Serializer: Sized {
     /// // Serializes as a map in which the values are all unit.
     /// impl Serialize for MapToUnit {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.collect_map(self.keys.iter().map(|k| (k, ())))
     ///     }
@@ -1311,7 +1426,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for DateTime {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.collect_str(&format_args!("{:?}{:?}",
     ///                                              self.naive_local(),
@@ -1351,7 +1467,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for DateTime {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         serializer.collect_str(&format_args!("{:?}{:?}",
     ///                                              self.naive_local(),
@@ -1392,7 +1509,8 @@ pub trait Serializer: Sized {
     ///
     /// impl Serialize for Timestamp {
     ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    ///         where S: Serializer
+    ///     where
+    ///         S: Serializer,
     ///     {
     ///         if serializer.is_human_readable() {
     ///             // Serialize to a human-readable string "2015-05-15T17:01:00Z".
@@ -1419,6 +1537,8 @@ pub trait Serializer: Sized {
 
 /// Returned from `Serializer::serialize_seq`.
 ///
+/// # Example use
+///
 /// ```rust
 /// # use std::marker::PhantomData;
 /// #
@@ -1441,10 +1561,12 @@ pub trait Serializer: Sized {
 /// use serde::ser::{Serialize, Serializer, SerializeSeq};
 ///
 /// impl<T> Serialize for Vec<T>
-///     where T: Serialize
+/// where
+///     T: Serialize,
 /// {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         let mut seq = serializer.serialize_seq(Some(self.len()))?;
 ///         for element in self {
@@ -1454,6 +1576,13 @@ pub trait Serializer: Sized {
 ///     }
 /// }
 /// ```
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SerializeSeq` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SerializeSeq {
     /// Must match the `Ok` type of our `Serializer`.
     type Ok;
@@ -1472,6 +1601,8 @@ pub trait SerializeSeq {
 
 /// Returned from `Serializer::serialize_tuple`.
 ///
+/// # Example use
+///
 /// ```rust
 /// use serde::ser::{Serialize, Serializer, SerializeTuple};
 ///
@@ -1484,12 +1615,14 @@ pub trait SerializeSeq {
 /// # struct Tuple3<A, B, C>(A, B, C);
 /// #
 /// # impl<A, B, C> Serialize for Tuple3<A, B, C>
-///     where A: Serialize,
-///           B: Serialize,
-///           C: Serialize
+/// where
+///     A: Serialize,
+///     B: Serialize,
+///     C: Serialize,
 /// {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         let mut tup = serializer.serialize_tuple(3)?;
 ///         tup.serialize_element(&self.0)?;
@@ -1528,10 +1661,12 @@ pub trait SerializeSeq {
 /// # }
 /// #
 /// # impl<T> Serialize for Array<T>
-///     where T: Serialize
+/// where
+///     T: Serialize,
 /// {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         let mut seq = serializer.serialize_tuple(16)?;
 ///         for element in self {
@@ -1541,6 +1676,13 @@ pub trait SerializeSeq {
 ///     }
 /// }
 /// ```
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SerializeTuple` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SerializeTuple {
     /// Must match the `Ok` type of our `Serializer`.
     type Ok;
@@ -1559,6 +1701,8 @@ pub trait SerializeTuple {
 
 /// Returned from `Serializer::serialize_tuple_struct`.
 ///
+/// # Example use
+///
 /// ```rust
 /// use serde::ser::{Serialize, Serializer, SerializeTupleStruct};
 ///
@@ -1566,7 +1710,8 @@ pub trait SerializeTuple {
 ///
 /// impl Serialize for Rgb {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         let mut ts = serializer.serialize_tuple_struct("Rgb", 3)?;
 ///         ts.serialize_field(&self.0)?;
@@ -1576,6 +1721,13 @@ pub trait SerializeTuple {
 ///     }
 /// }
 /// ```
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SerializeTupleStruct` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SerializeTupleStruct {
     /// Must match the `Ok` type of our `Serializer`.
     type Ok;
@@ -1594,6 +1746,8 @@ pub trait SerializeTupleStruct {
 
 /// Returned from `Serializer::serialize_tuple_variant`.
 ///
+/// # Example use
+///
 /// ```rust
 /// use serde::ser::{Serialize, Serializer, SerializeTupleVariant};
 ///
@@ -1604,7 +1758,8 @@ pub trait SerializeTupleStruct {
 ///
 /// impl Serialize for E {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         match *self {
 ///             E::T(ref a, ref b) => {
@@ -1624,6 +1779,13 @@ pub trait SerializeTupleStruct {
 ///     }
 /// }
 /// ```
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SerializeTupleVariant` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SerializeTupleVariant {
     /// Must match the `Ok` type of our `Serializer`.
     type Ok;
@@ -1642,6 +1804,8 @@ pub trait SerializeTupleVariant {
 
 /// Returned from `Serializer::serialize_map`.
 ///
+/// # Example use
+///
 /// ```rust
 /// # use std::marker::PhantomData;
 /// #
@@ -1665,11 +1829,13 @@ pub trait SerializeTupleVariant {
 /// use serde::ser::{Serialize, Serializer, SerializeMap};
 ///
 /// impl<K, V> Serialize for HashMap<K, V>
-///     where K: Serialize,
-///           V: Serialize
+/// where
+///     K: Serialize,
+///     V: Serialize,
 /// {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         let mut map = serializer.serialize_map(Some(self.len()))?;
 ///         for (k, v) in self {
@@ -1679,6 +1845,13 @@ pub trait SerializeTupleVariant {
 ///     }
 /// }
 /// ```
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SerializeMap` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SerializeMap {
     /// Must match the `Ok` type of our `Serializer`.
     type Ok;
@@ -1742,6 +1915,8 @@ pub trait SerializeMap {
 
 /// Returned from `Serializer::serialize_struct`.
 ///
+/// # Example use
+///
 /// ```rust
 /// use serde::ser::{Serialize, Serializer, SerializeStruct};
 ///
@@ -1753,7 +1928,8 @@ pub trait SerializeMap {
 ///
 /// impl Serialize for Rgb {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         let mut rgb = serializer.serialize_struct("Rgb", 3)?;
 ///         rgb.serialize_field("r", &self.r)?;
@@ -1763,6 +1939,13 @@ pub trait SerializeMap {
 ///     }
 /// }
 /// ```
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SerializeStruct` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SerializeStruct {
     /// Must match the `Ok` type of our `Serializer`.
     type Ok;
@@ -1792,6 +1975,8 @@ pub trait SerializeStruct {
 
 /// Returned from `Serializer::serialize_struct_variant`.
 ///
+/// # Example use
+///
 /// ```rust
 /// use serde::ser::{Serialize, Serializer, SerializeStructVariant};
 ///
@@ -1801,7 +1986,8 @@ pub trait SerializeStruct {
 ///
 /// impl Serialize for E {
 ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-///         where S: Serializer
+///     where
+///         S: Serializer,
 ///     {
 ///         match *self {
 ///             E::S { ref r, ref g, ref b } => {
@@ -1815,6 +2001,13 @@ pub trait SerializeStruct {
 ///     }
 /// }
 /// ```
+///
+/// # Example implementation
+///
+/// The [example data format] presented on the website demonstrates an
+/// implementation of `SerializeStructVariant` for a basic JSON data format.
+///
+/// [example data format]: https://serde.rs/data-format.html
 pub trait SerializeStructVariant {
     /// Must match the `Ok` type of our `Serializer`.
     type Ok;

serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.34" # remember to update html_root_url
+version = "1.0.67" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Macros 1.1 implementation of #[derive(Serialize, Deserialize)]"
@@ -8,8 +8,8 @@ homepage = "https://serde.rs"
 repository = "https://github.com/serde-rs/serde"
 documentation = "https://serde.rs/codegen.html"
 keywords = ["serde", "serialization", "no_std"]
-readme = "README.md"
-include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
+readme = "crates-io.md"
+include = ["Cargo.toml", "src/**/*.rs", "crates-io.md", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
 
 [badges]
 travis-ci = { repository = "serde-rs/serde" }
@@ -23,10 +23,9 @@ name = "serde_derive"
 proc-macro = true
 
 [dependencies]
-proc-macro2 = "0.2"
-quote = "0.4"
-serde_derive_internals = { version = "=0.22.0", default-features = false, path = "../serde_derive_internals" }
-syn = { version = "0.12", features = ["visit"] }
+proc-macro2 = "0.4"
+quote = "0.6"
+syn = { version = "0.14", features = ["visit"] }
 
 [dev-dependencies]
 serde = { version = "1.0", path = "../serde" }

serde_derive/crates-io.md

@@ -0,0 +1 @@
+../crates-io.md

serde_derive/src/bound.rs

@@ -8,13 +8,14 @@
 
 use std::collections::HashSet;
 
-use syn::{self, visit};
-use syn::punctuated::Punctuated;
+use syn;
+use syn::punctuated::{Pair, Punctuated};
+use syn::visit::{self, Visit};
 
-use internals::ast::{Data, Container};
+use internals::ast::{Container, Data};
 use internals::attr;
 
-use proc_macro2::{Span, Term};
+use proc_macro2::Span;
 
 // Remove the default from every type parameter because in the generated impls
 // they look like associated types: "error: associated type bindings are not
@@ -25,13 +26,11 @@ pub fn without_defaults(generics: &syn::Generics) -> syn::Generics {
             .params
             .iter()
             .map(|param| match *param {
-                syn::GenericParam::Type(ref param) => {
-                    syn::GenericParam::Type(syn::TypeParam {
-                        eq_token: None,
-                        default: None,
-                        ..param.clone()
-                    })
-                }
+                syn::GenericParam::Type(ref param) => syn::GenericParam::Type(syn::TypeParam {
+                    eq_token: None,
+                    default: None,
+                    ..param.clone()
+                }),
                 _ => param.clone(),
             })
             .collect(),
@@ -44,45 +43,48 @@ pub fn with_where_predicates(
     predicates: &[syn::WherePredicate],
 ) -> syn::Generics {
     let mut generics = generics.clone();
-    if generics.where_clause.is_none() {
-        generics.where_clause = Some(syn::WhereClause {
-            where_token: Default::default(),
-            predicates: Punctuated::new(),
-        });
-    }
-    generics.where_clause
-        .as_mut()
-        .unwrap()
+    generics
+        .make_where_clause()
         .predicates
         .extend(predicates.into_iter().cloned());
     generics
 }
 
-pub fn with_where_predicates_from_fields<F>(
+pub fn with_where_predicates_from_fields(
     cont: &Container,
     generics: &syn::Generics,
-    from_field: F,
-) -> syn::Generics
-where
-    F: Fn(&attr::Field) -> Option<&[syn::WherePredicate]>,
-{
-    let predicates = cont.data
+    from_field: fn(&attr::Field) -> Option<&[syn::WherePredicate]>,
+) -> syn::Generics {
+    let predicates = cont
+        .data
         .all_fields()
         .flat_map(|field| from_field(&field.attrs))
         .flat_map(|predicates| predicates.to_vec());
 
     let mut generics = generics.clone();
-    if generics.where_clause.is_none() {
-        generics.where_clause = Some(syn::WhereClause {
-            where_token: Default::default(),
-            predicates: Punctuated::new(),
-        });
-    }
-    generics.where_clause
-        .as_mut()
-        .unwrap()
-        .predicates
-        .extend(predicates);
+    generics.make_where_clause().predicates.extend(predicates);
+    generics
+}
+
+pub fn with_where_predicates_from_variants(
+    cont: &Container,
+    generics: &syn::Generics,
+    from_variant: fn(&attr::Variant) -> Option<&[syn::WherePredicate]>,
+) -> syn::Generics {
+    let variants = match cont.data {
+        Data::Enum(ref variants) => variants,
+        Data::Struct(_, _) => {
+            return generics.clone();
+        }
+    };
+
+    let predicates = variants
+        .iter()
+        .flat_map(|variant| from_variant(&variant.attrs))
+        .flat_map(|predicates| predicates.to_vec());
+
+    let mut generics = generics.clone();
+    generics.make_where_clause().predicates.extend(predicates);
     generics
 }
 
@@ -97,26 +99,39 @@ where
 //         #[serde(skip_serializing)]
 //         c: C,
 //     }
-pub fn with_bound<F>(
+pub fn with_bound(
     cont: &Container,
     generics: &syn::Generics,
-    filter: F,
+    filter: fn(&attr::Field, Option<&attr::Variant>) -> bool,
     bound: &syn::Path,
-) -> syn::Generics
-where
-    F: Fn(&attr::Field, Option<&attr::Variant>) -> bool,
-{
-    struct FindTyParams {
+) -> syn::Generics {
+    struct FindTyParams<'ast> {
         // Set of all generic type parameters on the current struct (A, B, C in
         // the example). Initialized up front.
-        all_ty_params: HashSet<syn::Ident>,
+        all_type_params: HashSet<syn::Ident>,
+
         // Set of generic type parameters used in fields for which filter
         // returns true (A and B in the example). Filled in as the visitor sees
         // them.
-        relevant_ty_params: HashSet<syn::Ident>,
+        relevant_type_params: HashSet<syn::Ident>,
+
+        // Fields whose type is an associated type of one of the generic type
+        // parameters.
+        associated_type_usage: Vec<&'ast syn::TypePath>,
     }
-    impl<'ast> visit::Visit<'ast> for FindTyParams {
-        fn visit_path(&mut self, path: &syn::Path) {
+    impl<'ast> Visit<'ast> for FindTyParams<'ast> {
+        fn visit_field(&mut self, field: &'ast syn::Field) {
+            if let syn::Type::Path(ref ty) = field.ty {
+                if let Some(Pair::Punctuated(ref t, _)) = ty.path.segments.first() {
+                    if self.all_type_params.contains(&t.ident) {
+                        self.associated_type_usage.push(ty);
+                    }
+                }
+            }
+            self.visit_type(&field.ty);
+        }
+
+        fn visit_path(&mut self, path: &'ast syn::Path) {
             if let Some(seg) = path.segments.last() {
                 if seg.into_value().ident == "PhantomData" {
                     // Hardcoded exception, because PhantomData<T> implements
@@ -125,9 +140,9 @@ where
                 }
             }
             if path.leading_colon.is_none() && path.segments.len() == 1 {
-                let id = path.segments[0].ident;
-                if self.all_ty_params.contains(&id) {
-                    self.relevant_ty_params.insert(id);
+                let id = &path.segments[0].ident;
+                if self.all_type_params.contains(id) {
+                    self.relevant_type_params.insert(id.clone());
                 }
             }
             visit::visit_path(self, path);
@@ -139,21 +154,18 @@ where
         //         mac: T!(),
         //         marker: PhantomData<T>,
         //     }
-        fn visit_macro(&mut self, _mac: &syn::Macro) {}
+        fn visit_macro(&mut self, _mac: &'ast syn::Macro) {}
     }
 
-    let all_ty_params: HashSet<_> = generics
-        .params
-        .iter()
-        .filter_map(|param| match *param {
-            syn::GenericParam::Type(ref param) => Some(param.ident),
-            _ => None,
-        })
+    let all_type_params = generics
+        .type_params()
+        .map(|param| param.ident.clone())
         .collect();
 
     let mut visitor = FindTyParams {
-        all_ty_params: all_ty_params,
-        relevant_ty_params: HashSet::new(),
+        all_type_params: all_type_params,
+        relevant_type_params: HashSet::new(),
+        associated_type_usage: Vec::new(),
     };
     match cont.data {
         Data::Enum(ref variants) => for variant in variants.iter() {
@@ -162,54 +174,47 @@ where
                 .iter()
                 .filter(|field| filter(&field.attrs, Some(&variant.attrs)));
             for field in relevant_fields {
-                visit::visit_type(&mut visitor, field.ty);
+                visitor.visit_field(field.original);
             }
         },
         Data::Struct(_, ref fields) => {
             for field in fields.iter().filter(|field| filter(&field.attrs, None)) {
-                visit::visit_type(&mut visitor, field.ty);
+                visitor.visit_field(field.original);
             }
         }
     }
 
+    let relevant_type_params = visitor.relevant_type_params;
+    let associated_type_usage = visitor.associated_type_usage;
     let new_predicates = generics
-        .params
-        .iter()
-        .filter_map(|param| match *param {
-            syn::GenericParam::Type(ref param) => Some(param.ident),
-            _ => None,
+        .type_params()
+        .map(|param| param.ident.clone())
+        .filter(|id| relevant_type_params.contains(id))
+        .map(|id| syn::TypePath {
+            qself: None,
+            path: id.into(),
         })
-        .filter(|id| visitor.relevant_ty_params.contains(id))
-        .map(|id| {
+        .chain(associated_type_usage.into_iter().cloned())
+        .map(|bounded_ty| {
             syn::WherePredicate::Type(syn::PredicateType {
                 lifetimes: None,
                 // the type parameter that is being bounded e.g. T
-                bounded_ty: syn::Type::Path(syn::TypePath {
-                    qself: None,
-                    path: id.into(),
-                }),
-                colon_token: Default::default(),
+                bounded_ty: syn::Type::Path(bounded_ty),
+                colon_token: <Token![:]>::default(),
                 // the bound e.g. Serialize
-                bounds: vec![
-                    syn::TypeParamBound::Trait(syn::TraitBound {
-                        modifier: syn::TraitBoundModifier::None,
-                        lifetimes: None,
-                        path: bound.clone(),
-                    }),
-                ].into_iter().collect(),
+                bounds: vec![syn::TypeParamBound::Trait(syn::TraitBound {
+                    paren_token: None,
+                    modifier: syn::TraitBoundModifier::None,
+                    lifetimes: None,
+                    path: bound.clone(),
+                })].into_iter()
+                    .collect(),
             })
         });
 
     let mut generics = generics.clone();
-    if generics.where_clause.is_none() {
-        generics.where_clause = Some(syn::WhereClause {
-            where_token: Default::default(),
-            predicates: Punctuated::new(),
-        });
-    }
-    generics.where_clause
-        .as_mut()
-        .unwrap()
+    generics
+        .make_where_clause()
         .predicates
         .extend(new_predicates);
     generics
@@ -221,59 +226,51 @@ pub fn with_self_bound(
     bound: &syn::Path,
 ) -> syn::Generics {
     let mut generics = generics.clone();
-    if generics.where_clause.is_none() {
-        generics.where_clause = Some(syn::WhereClause {
-            where_token: Default::default(),
-            predicates: Punctuated::new(),
-        });
-    }
-    generics.where_clause
-        .as_mut()
-        .unwrap()
+    generics
+        .make_where_clause()
         .predicates
         .push(syn::WherePredicate::Type(syn::PredicateType {
             lifetimes: None,
             // the type that is being bounded e.g. MyStruct<'a, T>
             bounded_ty: type_of_item(cont),
-            colon_token: Default::default(),
+            colon_token: <Token![:]>::default(),
             // the bound e.g. Default
-            bounds: vec![
-                syn::TypeParamBound::Trait(syn::TraitBound {
-                    modifier: syn::TraitBoundModifier::None,
-                    lifetimes: None,
-                    path: bound.clone(),
-                }),
-            ].into_iter().collect(),
+            bounds: vec![syn::TypeParamBound::Trait(syn::TraitBound {
+                paren_token: None,
+                modifier: syn::TraitBoundModifier::None,
+                lifetimes: None,
+                path: bound.clone(),
+            })].into_iter()
+                .collect(),
         }));
     generics
 }
 
 pub fn with_lifetime_bound(generics: &syn::Generics, lifetime: &str) -> syn::Generics {
-    let bound = syn::Lifetime::new(Term::intern(lifetime), Span::def_site());
+    let bound = syn::Lifetime::new(lifetime, Span::call_site());
     let def = syn::LifetimeDef {
         attrs: Vec::new(),
-        lifetime: bound,
+        lifetime: bound.clone(),
         colon_token: None,
         bounds: Punctuated::new(),
     };
 
     let params = Some(syn::GenericParam::Lifetime(def))
         .into_iter()
-        .chain(generics.params
-            .iter()
-            .cloned()
-            .map(|mut param| {
-                match param {
-                    syn::GenericParam::Lifetime(ref mut param) => {
-                        param.bounds.push(bound);
-                    }
-                    syn::GenericParam::Type(ref mut param) => {
-                        param.bounds.push(syn::TypeParamBound::Lifetime(bound));
-                    }
-                    syn::GenericParam::Const(_) => {}
+        .chain(generics.params.iter().cloned().map(|mut param| {
+            match param {
+                syn::GenericParam::Lifetime(ref mut param) => {
+                    param.bounds.push(bound.clone());
                 }
-                param
-            }))
+                syn::GenericParam::Type(ref mut param) => {
+                    param
+                        .bounds
+                        .push(syn::TypeParamBound::Lifetime(bound.clone()));
+                }
+                syn::GenericParam::Const(_) => {}
+            }
+            param
+        }))
         .collect();
 
     syn::Generics {
@@ -287,36 +284,36 @@ fn type_of_item(cont: &Container) -> syn::Type {
         qself: None,
         path: syn::Path {
             leading_colon: None,
-            segments: vec![
-                syn::PathSegment {
-                    ident: cont.ident,
-                    arguments: syn::PathArguments::AngleBracketed(
-                        syn::AngleBracketedGenericArguments {
-                            colon2_token: None,
-                            lt_token: Default::default(),
-                            args: cont.generics
-                                .params
-                                .iter()
-                                .map(|param| match *param {
-                                    syn::GenericParam::Type(ref param) => {
-                                        syn::GenericArgument::Type(syn::Type::Path(syn::TypePath {
-                                            qself: None,
-                                            path: param.ident.into(),
-                                        }))
-                                    }
-                                    syn::GenericParam::Lifetime(ref param) => {
-                                        syn::GenericArgument::Lifetime(param.lifetime)
-                                    }
-                                    syn::GenericParam::Const(_) => {
-                                        panic!("Serde does not support const generics yet");
-                                    }
-                                })
-                                .collect(),
-                            gt_token: Default::default(),
-                        },
-                    ),
-                },
-            ].into_iter().collect(),
+            segments: vec![syn::PathSegment {
+                ident: cont.ident.clone(),
+                arguments: syn::PathArguments::AngleBracketed(
+                    syn::AngleBracketedGenericArguments {
+                        colon2_token: None,
+                        lt_token: <Token![<]>::default(),
+                        args: cont
+                            .generics
+                            .params
+                            .iter()
+                            .map(|param| match *param {
+                                syn::GenericParam::Type(ref param) => {
+                                    syn::GenericArgument::Type(syn::Type::Path(syn::TypePath {
+                                        qself: None,
+                                        path: param.ident.clone().into(),
+                                    }))
+                                }
+                                syn::GenericParam::Lifetime(ref param) => {
+                                    syn::GenericArgument::Lifetime(param.lifetime.clone())
+                                }
+                                syn::GenericParam::Const(_) => {
+                                    panic!("Serde does not support const generics yet");
+                                }
+                            })
+                            .collect(),
+                        gt_token: <Token![>]>::default(),
+                    },
+                ),
+            }].into_iter()
+                .collect(),
         },
     })
 }

serde_derive/src/fragment.rs

@@ -6,15 +6,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use quote::{ToTokens, Tokens};
+use proc_macro2::TokenStream;
+use quote::ToTokens;
 use syn::token;
 
 pub enum Fragment {
     /// Tokens that can be used as an expression.
-    Expr(Tokens),
+    Expr(TokenStream),
     /// Tokens that can be used inside a block. The surrounding curly braces are
     /// not part of these tokens.
-    Block(Tokens),
+    Block(TokenStream),
 }
 
 macro_rules! quote_expr {
@@ -33,7 +34,7 @@ macro_rules! quote_block {
 /// Block fragments in curly braces.
 pub struct Expr(pub Fragment);
 impl ToTokens for Expr {
-    fn to_tokens(&self, out: &mut Tokens) {
+    fn to_tokens(&self, out: &mut TokenStream) {
         match self.0 {
             Fragment::Expr(ref expr) => expr.to_tokens(out),
             Fragment::Block(ref block) => {
@@ -46,7 +47,7 @@ impl ToTokens for Expr {
 /// Interpolate a fragment as the statements of a block.
 pub struct Stmts(pub Fragment);
 impl ToTokens for Stmts {
-    fn to_tokens(&self, out: &mut Tokens) {
+    fn to_tokens(&self, out: &mut TokenStream) {
         match self.0 {
             Fragment::Expr(ref expr) => expr.to_tokens(out),
             Fragment::Block(ref block) => block.to_tokens(out),
@@ -58,7 +59,7 @@ impl ToTokens for Stmts {
 /// involves putting a comma after expressions and curly braces around blocks.
 pub struct Match(pub Fragment);
 impl ToTokens for Match {
-    fn to_tokens(&self, out: &mut Tokens) {
+    fn to_tokens(&self, out: &mut TokenStream) {
         match self.0 {
             Fragment::Expr(ref expr) => {
                 expr.to_tokens(out);
@@ -71,8 +72,8 @@ impl ToTokens for Match {
     }
 }
 
-impl AsRef<Tokens> for Fragment {
-    fn as_ref(&self) -> &Tokens {
+impl AsRef<TokenStream> for Fragment {
+    fn as_ref(&self) -> &TokenStream {
         match *self {
             Fragment::Expr(ref expr) => expr,
             Fragment::Block(ref block) => block,

serde_derive/src/internals/ast.rs

@@ -6,10 +6,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use internals::attr;
+use internals::check;
+use internals::{Ctxt, Derive};
 use syn;
-use attr;
-use check;
-use Ctxt;
 use syn::punctuated::Punctuated;
 
 pub struct Container<'a> {
@@ -32,7 +32,7 @@ pub struct Variant<'a> {
 }
 
 pub struct Field<'a> {
-    pub ident: Option<syn::Ident>,
+    pub member: syn::Member,
     pub attrs: attr::Field,
     pub ty: &'a syn::Type,
     pub original: &'a syn::Field,
@@ -47,7 +47,7 @@ pub enum Style {
 }
 
 impl<'a> Container<'a> {
-    pub fn from_ast(cx: &Ctxt, item: &'a syn::DeriveInput) -> Container<'a> {
+    pub fn from_ast(cx: &Ctxt, item: &'a syn::DeriveInput, derive: Derive) -> Container<'a> {
         let mut attrs = attr::Container::from_ast(cx, item);
 
         let mut data = match item.data {
@@ -68,6 +68,9 @@ impl<'a> Container<'a> {
             Data::Enum(ref mut variants) => for variant in variants {
                 variant.attrs.rename_by_rule(attrs.rename_all());
                 for field in &mut variant.fields {
+                    if field.attrs.flatten() {
+                        has_flatten = true;
+                    }
                     field.attrs.rename_by_rule(variant.attrs.rename_all());
                 }
             },
@@ -83,13 +86,13 @@ impl<'a> Container<'a> {
             attrs.mark_has_flatten();
         }
 
-        let item = Container {
-            ident: item.ident,
+        let mut item = Container {
+            ident: item.ident.clone(),
             attrs: attrs,
             data: data,
             generics: &item.generics,
         };
-        check::check(cx, &item);
+        check::check(cx, &mut item, derive);
         item
     }
 }
@@ -121,7 +124,7 @@ fn enum_from_ast<'a>(
             let (style, fields) =
                 struct_from_ast(cx, &variant.fields, Some(&attrs), container_default);
             Variant {
-                ident: variant.ident,
+                ident: variant.ident.clone(),
                 attrs: attrs,
                 style: style,
                 fields: fields,
@@ -163,7 +166,10 @@ fn fields_from_ast<'a>(
         .iter()
         .enumerate()
         .map(|(i, field)| Field {
-            ident: field.ident,
+            member: match field.ident {
+                Some(ref ident) => syn::Member::Named(ident.clone()),
+                None => syn::Member::Unnamed(i.into()),
+            },
             attrs: attr::Field::from_ast(cx, i, field, attrs, container_default),
             ty: &field.ty,
             original: field,

serde_derive/src/internals/attr.rs

@@ -6,16 +6,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use Ctxt;
+use internals::Ctxt;
+use proc_macro2::{Group, Span, TokenStream, TokenTree};
+use std::collections::BTreeSet;
+use std::str::FromStr;
 use syn;
+use syn::punctuated::Punctuated;
+use syn::synom::{ParseError, Synom};
 use syn::Ident;
 use syn::Meta::{List, NameValue, Word};
 use syn::NestedMeta::{Literal, Meta};
-use syn::punctuated::Punctuated;
-use syn::synom::{Synom, ParseError};
-use std::collections::BTreeSet;
-use std::str::FromStr;
-use proc_macro2::{Span, TokenStream, TokenNode, TokenTree};
 
 // This module handles parsing of `#[serde(...)]` attributes. The entrypoints
 // are `attr::Container::from_ast`, `attr::Variant::from_ast`, and
@@ -25,7 +25,7 @@ use proc_macro2::{Span, TokenStream, TokenNode, TokenTree};
 // user will see errors simultaneously for all bad attributes in the crate
 // rather than just the first.
 
-pub use case::RenameRule;
+pub use internals::case::RenameRule;
 
 #[derive(Copy, Clone)]
 struct Attr<'c, T> {
@@ -105,6 +105,7 @@ impl Name {
 /// Represents container (e.g. struct) attribute information
 pub struct Container {
     name: Name,
+    transparent: bool,
     deny_unknown_fields: bool,
     default: Default,
     rename_all: RenameRule,
@@ -167,6 +168,7 @@ pub enum Identifier {
 }
 
 impl Identifier {
+    #[cfg(feature = "deserialize_in_place")]
     pub fn is_some(self) -> bool {
         match self {
             Identifier::No => false,
@@ -180,6 +182,7 @@ impl Container {
     pub fn from_ast(cx: &Ctxt, item: &syn::DeriveInput) -> Self {
         let mut ser_name = Attr::none(cx, "rename");
         let mut de_name = Attr::none(cx, "rename");
+        let mut transparent = BoolAttr::none(cx, "transparent");
         let mut deny_unknown_fields = BoolAttr::none(cx, "deny_unknown_fields");
         let mut default = Attr::none(cx, "default");
         let mut rename_all = Attr::none(cx, "rename_all");
@@ -199,7 +202,7 @@ impl Container {
                 match meta_item {
                     // Parse `#[serde(rename = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             ser_name.set(s.value());
                             de_name.set(s.value());
                         }
@@ -215,7 +218,7 @@ impl Container {
 
                     // Parse `#[serde(rename_all = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename_all" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match RenameRule::from_str(&s.value()) {
                                 Ok(rename_rule) => rename_all.set(rename_rule),
                                 Err(()) => cx.error(format!(
@@ -227,14 +230,22 @@ impl Container {
                         }
                     }
 
+                    // Parse `#[serde(transparent)]`
+                    Meta(Word(ref word)) if word == "transparent" => {
+                        transparent.set_true();
+                    }
+
                     // Parse `#[serde(deny_unknown_fields)]`
-                    Meta(Word(word)) if word == "deny_unknown_fields" => {
+                    Meta(Word(ref word)) if word == "deny_unknown_fields" => {
                         deny_unknown_fields.set_true();
                     }
 
                     // Parse `#[serde(default)]`
-                    Meta(Word(word)) if word == "default" => match item.data {
-                        syn::Data::Struct(syn::DataStruct { fields: syn::Fields::Named(_), .. }) => {
+                    Meta(Word(ref word)) if word == "default" => match item.data {
+                        syn::Data::Struct(syn::DataStruct {
+                            fields: syn::Fields::Named(_),
+                            ..
+                        }) => {
                             default.set(Default::Default);
                         }
                         _ => cx.error(
@@ -245,9 +256,12 @@ impl Container {
 
                     // Parse `#[serde(default = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "default" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             match item.data {
-                                syn::Data::Struct(syn::DataStruct { fields: syn::Fields::Named(_), .. }) => {
+                                syn::Data::Struct(syn::DataStruct {
+                                    fields: syn::Fields::Named(_),
+                                    ..
+                                }) => {
                                     default.set(Default::Path(path));
                                 }
                                 _ => cx.error(
@@ -261,7 +275,7 @@ impl Container {
                     // Parse `#[serde(bound = "D: Serialize")]`
                     Meta(NameValue(ref m)) if m.ident == "bound" => {
                         if let Ok(where_predicates) =
-                            parse_lit_into_where(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit)
+                            parse_lit_into_where(cx, &m.ident, &m.ident, &m.lit)
                         {
                             ser_bound.set(where_predicates.clone());
                             de_bound.set(where_predicates);
@@ -277,7 +291,7 @@ impl Container {
                     }
 
                     // Parse `#[serde(untagged)]`
-                    Meta(Word(word)) if word == "untagged" => match item.data {
+                    Meta(Word(ref word)) if word == "untagged" => match item.data {
                         syn::Data::Enum(_) => {
                             untagged.set_true();
                         }
@@ -288,7 +302,7 @@ impl Container {
 
                     // Parse `#[serde(tag = "type")]`
                     Meta(NameValue(ref m)) if m.ident == "tag" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match item.data {
                                 syn::Data::Enum(_) => {
                                     internal_tag.set(s.value());
@@ -302,7 +316,7 @@ impl Container {
 
                     // Parse `#[serde(content = "c")]`
                     Meta(NameValue(ref m)) if m.ident == "content" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match item.data {
                                 syn::Data::Enum(_) => {
                                     content.set(s.value());
@@ -317,32 +331,36 @@ impl Container {
 
                     // Parse `#[serde(from = "Type")]
                     Meta(NameValue(ref m)) if m.ident == "from" => {
-                        if let Ok(from_ty) = parse_lit_into_ty(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(from_ty) = parse_lit_into_ty(cx, &m.ident, &m.lit) {
                             type_from.set_opt(Some(from_ty));
                         }
                     }
 
                     // Parse `#[serde(into = "Type")]
                     Meta(NameValue(ref m)) if m.ident == "into" => {
-                        if let Ok(into_ty) = parse_lit_into_ty(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(into_ty) = parse_lit_into_ty(cx, &m.ident, &m.lit) {
                             type_into.set_opt(Some(into_ty));
                         }
                     }
 
                     // Parse `#[serde(remote = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "remote" => {
-                        if let Ok(path) = parse_lit_into_path(cx, m.ident.as_ref(), &m.lit) {
-                            remote.set(path);
+                        if let Ok(path) = parse_lit_into_path(cx, &m.ident, &m.lit) {
+                            if is_primitive_path(&path, "Self") {
+                                remote.set(item.ident.clone().into());
+                            } else {
+                                remote.set(path);
+                            }
                         }
                     }
 
                     // Parse `#[serde(field_identifier)]`
-                    Meta(Word(word)) if word == "field_identifier" => {
+                    Meta(Word(ref word)) if word == "field_identifier" => {
                         field_identifier.set_true();
                     }
 
                     // Parse `#[serde(variant_identifier)]`
-                    Meta(Word(word)) if word == "variant_identifier" => {
+                    Meta(Word(ref word)) if word == "variant_identifier" => {
                         variant_identifier.set_true();
                     }
 
@@ -365,6 +383,7 @@ impl Container {
                 serialize: ser_name.get().unwrap_or_else(|| item.ident.to_string()),
                 deserialize: de_name.get().unwrap_or_else(|| item.ident.to_string()),
             },
+            transparent: transparent.get(),
             deny_unknown_fields: deny_unknown_fields.get(),
             default: default.get().unwrap_or(Default::None),
             rename_all: rename_all.get().unwrap_or(RenameRule::None),
@@ -387,6 +406,10 @@ impl Container {
         &self.rename_all
     }
 
+    pub fn transparent(&self) -> bool {
+        self.transparent
+    }
+
     pub fn deny_unknown_fields(&self) -> bool {
         self.deny_unknown_fields
     }
@@ -499,13 +522,11 @@ fn decide_identifier(
         }
         (&syn::Data::Enum(_), true, false) => Identifier::Field,
         (&syn::Data::Enum(_), false, true) => Identifier::Variant,
-        (&syn::Data::Struct(_), true, false)
-        | (&syn::Data::Union(_), true, false) => {
+        (&syn::Data::Struct(_), true, false) | (&syn::Data::Union(_), true, false) => {
             cx.error("`field_identifier` can only be used on an enum");
             Identifier::No
         }
-        (&syn::Data::Struct(_), false, true)
-        | (&syn::Data::Union(_), false, true) => {
+        (&syn::Data::Struct(_), false, true) | (&syn::Data::Union(_), false, true) => {
             cx.error("`variant_identifier` can only be used on an enum");
             Identifier::No
         }
@@ -518,6 +539,8 @@ pub struct Variant {
     ser_renamed: bool,
     de_renamed: bool,
     rename_all: RenameRule,
+    ser_bound: Option<Vec<syn::WherePredicate>>,
+    de_bound: Option<Vec<syn::WherePredicate>>,
     skip_deserializing: bool,
     skip_serializing: bool,
     other: bool,
@@ -533,6 +556,8 @@ impl Variant {
         let mut skip_deserializing = BoolAttr::none(cx, "skip_deserializing");
         let mut skip_serializing = BoolAttr::none(cx, "skip_serializing");
         let mut rename_all = Attr::none(cx, "rename_all");
+        let mut ser_bound = Attr::none(cx, "bound");
+        let mut de_bound = Attr::none(cx, "bound");
         let mut other = BoolAttr::none(cx, "other");
         let mut serialize_with = Attr::none(cx, "serialize_with");
         let mut deserialize_with = Attr::none(cx, "deserialize_with");
@@ -543,7 +568,7 @@ impl Variant {
                 match meta_item {
                     // Parse `#[serde(rename = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             ser_name.set(s.value());
                             de_name.set(s.value());
                         }
@@ -559,7 +584,7 @@ impl Variant {
 
                     // Parse `#[serde(rename_all = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename_all" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match RenameRule::from_str(&s.value()) {
                                 Ok(rename_rule) => rename_all.set(rename_rule),
                                 Err(()) => cx.error(format!(
@@ -571,43 +596,73 @@ impl Variant {
                         }
                     }
 
+                    // Parse `#[serde(skip)]`
+                    Meta(Word(ref word)) if word == "skip" => {
+                        skip_serializing.set_true();
+                        skip_deserializing.set_true();
+                    }
+
                     // Parse `#[serde(skip_deserializing)]`
-                    Meta(Word(word)) if word == "skip_deserializing" => {
+                    Meta(Word(ref word)) if word == "skip_deserializing" => {
                         skip_deserializing.set_true();
                     }
 
                     // Parse `#[serde(skip_serializing)]`
-                    Meta(Word(word)) if word == "skip_serializing" => {
+                    Meta(Word(ref word)) if word == "skip_serializing" => {
                         skip_serializing.set_true();
                     }
 
                     // Parse `#[serde(other)]`
-                    Meta(Word(word)) if word == "other" => {
+                    Meta(Word(ref word)) if word == "other" => {
                         other.set_true();
                     }
 
+                    // Parse `#[serde(bound = "D: Serialize")]`
+                    Meta(NameValue(ref m)) if m.ident == "bound" => {
+                        if let Ok(where_predicates) =
+                            parse_lit_into_where(cx, &m.ident, &m.ident, &m.lit)
+                        {
+                            ser_bound.set(where_predicates.clone());
+                            de_bound.set(where_predicates);
+                        }
+                    }
+
+                    // Parse `#[serde(bound(serialize = "D: Serialize", deserialize = "D: Deserialize"))]`
+                    Meta(List(ref m)) if m.ident == "bound" => {
+                        if let Ok((ser, de)) = get_where_predicates(cx, &m.nested) {
+                            ser_bound.set_opt(ser);
+                            de_bound.set_opt(de);
+                        }
+                    }
+
                     // Parse `#[serde(with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             let mut ser_path = path.clone();
-                            ser_path.path.segments.push(Ident::new("serialize", Span::call_site()).into());
+                            ser_path
+                                .path
+                                .segments
+                                .push(Ident::new("serialize", Span::call_site()).into());
                             serialize_with.set(ser_path);
                             let mut de_path = path;
-                            de_path.path.segments.push(Ident::new("deserialize", Span::call_site()).into());
+                            de_path
+                                .path
+                                .segments
+                                .push(Ident::new("deserialize", Span::call_site()).into());
                             deserialize_with.set(de_path);
                         }
                     }
 
                     // Parse `#[serde(serialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "serialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             serialize_with.set(path);
                         }
                     }
 
                     // Parse `#[serde(deserialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "deserialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             deserialize_with.set(path);
                         }
                     }
@@ -648,6 +703,8 @@ impl Variant {
             ser_renamed: ser_renamed,
             de_renamed: de_renamed,
             rename_all: rename_all.get().unwrap_or(RenameRule::None),
+            ser_bound: ser_bound.get(),
+            de_bound: de_bound.get(),
             skip_deserializing: skip_deserializing.get(),
             skip_serializing: skip_serializing.get(),
             other: other.get(),
@@ -674,6 +731,14 @@ impl Variant {
         &self.rename_all
     }
 
+    pub fn ser_bound(&self) -> Option<&[syn::WherePredicate]> {
+        self.ser_bound.as_ref().map(|vec| &vec[..])
+    }
+
+    pub fn de_bound(&self) -> Option<&[syn::WherePredicate]> {
+        self.de_bound.as_ref().map(|vec| &vec[..])
+    }
+
     pub fn skip_deserializing(&self) -> bool {
         self.skip_deserializing
     }
@@ -711,6 +776,7 @@ pub struct Field {
     borrowed_lifetimes: BTreeSet<syn::Lifetime>,
     getter: Option<syn::ExprPath>,
     flatten: bool,
+    transparent: bool,
 }
 
 /// Represents the default to use for a field when deserializing.
@@ -723,6 +789,15 @@ pub enum Default {
     Path(syn::ExprPath),
 }
 
+impl Default {
+    pub fn is_none(&self) -> bool {
+        match *self {
+            Default::None => true,
+            Default::Default | Default::Path(_) => false,
+        }
+    }
+}
+
 impl Field {
     /// Extract out the `#[serde(...)]` attributes from a struct field.
     pub fn from_ast(
@@ -752,9 +827,7 @@ impl Field {
         };
 
         let variant_borrow = attrs
-            .map(|variant| &variant.borrow)
-            .unwrap_or(&None)
-            .as_ref()
+            .and_then(|variant| variant.borrow.as_ref())
             .map(|borrow| vec![Meta(borrow.clone())]);
 
         for meta_items in field
@@ -767,7 +840,7 @@ impl Field {
                 match meta_item {
                     // Parse `#[serde(rename = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             ser_name.set(s.value());
                             de_name.set(s.value());
                         }
@@ -782,62 +855,68 @@ impl Field {
                     }
 
                     // Parse `#[serde(default)]`
-                    Meta(Word(word)) if word == "default" => {
+                    Meta(Word(ref word)) if word == "default" => {
                         default.set(Default::Default);
                     }
 
                     // Parse `#[serde(default = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "default" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             default.set(Default::Path(path));
                         }
                     }
 
                     // Parse `#[serde(skip_serializing)]`
-                    Meta(Word(word)) if word == "skip_serializing" => {
+                    Meta(Word(ref word)) if word == "skip_serializing" => {
                         skip_serializing.set_true();
                     }
 
                     // Parse `#[serde(skip_deserializing)]`
-                    Meta(Word(word)) if word == "skip_deserializing" => {
+                    Meta(Word(ref word)) if word == "skip_deserializing" => {
                         skip_deserializing.set_true();
                     }
 
                     // Parse `#[serde(skip)]`
-                    Meta(Word(word)) if word == "skip" => {
+                    Meta(Word(ref word)) if word == "skip" => {
                         skip_serializing.set_true();
                         skip_deserializing.set_true();
                     }
 
                     // Parse `#[serde(skip_serializing_if = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "skip_serializing_if" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             skip_serializing_if.set(path);
                         }
                     }
 
                     // Parse `#[serde(serialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "serialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             serialize_with.set(path);
                         }
                     }
 
                     // Parse `#[serde(deserialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "deserialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             deserialize_with.set(path);
                         }
                     }
 
                     // Parse `#[serde(with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             let mut ser_path = path.clone();
-                            ser_path.path.segments.push(Ident::new("serialize", Span::call_site()).into());
+                            ser_path
+                                .path
+                                .segments
+                                .push(Ident::new("serialize", Span::call_site()).into());
                             serialize_with.set(ser_path);
                             let mut de_path = path;
-                            de_path.path.segments.push(Ident::new("deserialize", Span::call_site()).into());
+                            de_path
+                                .path
+                                .segments
+                                .push(Ident::new("deserialize", Span::call_site()).into());
                             deserialize_with.set(de_path);
                         }
                     }
@@ -845,7 +924,7 @@ impl Field {
                     // Parse `#[serde(bound = "D: Serialize")]`
                     Meta(NameValue(ref m)) if m.ident == "bound" => {
                         if let Ok(where_predicates) =
-                            parse_lit_into_where(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit)
+                            parse_lit_into_where(cx, &m.ident, &m.ident, &m.lit)
                         {
                             ser_bound.set(where_predicates.clone());
                             de_bound.set(where_predicates);
@@ -861,7 +940,7 @@ impl Field {
                     }
 
                     // Parse `#[serde(borrow)]`
-                    Meta(Word(word)) if word == "borrow" => {
+                    Meta(Word(ref word)) if word == "borrow" => {
                         if let Ok(borrowable) = borrowable_lifetimes(cx, &ident, &field.ty) {
                             borrowed_lifetimes.set(borrowable);
                         }
@@ -869,7 +948,7 @@ impl Field {
 
                     // Parse `#[serde(borrow = "'a + 'b")]`
                     Meta(NameValue(ref m)) if m.ident == "borrow" => {
-                        if let Ok(lifetimes) = parse_lit_into_lifetimes(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(lifetimes) = parse_lit_into_lifetimes(cx, &m.ident, &m.lit) {
                             if let Ok(borrowable) = borrowable_lifetimes(cx, &ident, &field.ty) {
                                 for lifetime in &lifetimes {
                                     if !borrowable.contains(lifetime) {
@@ -886,13 +965,13 @@ impl Field {
 
                     // Parse `#[serde(getter = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "getter" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             getter.set(path);
                         }
                     }
 
                     // Parse `#[serde(flatten)]`
-                    Meta(Word(word)) if word == "flatten" => {
+                    Meta(Word(ref word)) if word == "flatten" => {
                         flatten.set_true();
                     }
 
@@ -935,10 +1014,14 @@ impl Field {
                     leading_colon: None,
                     segments: Punctuated::new(),
                 };
-                path.segments.push(Ident::new("_serde", Span::def_site()).into());
-                path.segments.push(Ident::new("private", Span::def_site()).into());
-                path.segments.push(Ident::new("de", Span::def_site()).into());
-                path.segments.push(Ident::new("borrow_cow_str", Span::def_site()).into());
+                path.segments
+                    .push(Ident::new("_serde", Span::call_site()).into());
+                path.segments
+                    .push(Ident::new("private", Span::call_site()).into());
+                path.segments
+                    .push(Ident::new("de", Span::call_site()).into());
+                path.segments
+                    .push(Ident::new("borrow_cow_str", Span::call_site()).into());
                 let expr = syn::ExprPath {
                     attrs: Vec::new(),
                     qself: None,
@@ -950,10 +1033,14 @@ impl Field {
                     leading_colon: None,
                     segments: Punctuated::new(),
                 };
-                path.segments.push(Ident::new("_serde", Span::def_site()).into());
-                path.segments.push(Ident::new("private", Span::def_site()).into());
-                path.segments.push(Ident::new("de", Span::def_site()).into());
-                path.segments.push(Ident::new("borrow_cow_bytes", Span::def_site()).into());
+                path.segments
+                    .push(Ident::new("_serde", Span::call_site()).into());
+                path.segments
+                    .push(Ident::new("private", Span::call_site()).into());
+                path.segments
+                    .push(Ident::new("de", Span::call_site()).into());
+                path.segments
+                    .push(Ident::new("borrow_cow_bytes", Span::call_site()).into());
                 let expr = syn::ExprPath {
                     attrs: Vec::new(),
                     qself: None,
@@ -961,7 +1048,7 @@ impl Field {
                 };
                 deserialize_with.set_if_none(expr);
             }
-        } else if is_rptr(&field.ty, is_str) || is_rptr(&field.ty, is_slice_u8) {
+        } else if is_implicitly_borrowed(&field.ty) {
             // Types &str and &[u8] are always implicitly borrowed. No need for
             // a #[serde(borrow)].
             collect_lifetimes(&field.ty, &mut borrowed_lifetimes);
@@ -989,6 +1076,7 @@ impl Field {
             borrowed_lifetimes: borrowed_lifetimes,
             getter: getter.get(),
             flatten: flatten.get(),
+            transparent: false,
         }
     }
 
@@ -1048,6 +1136,14 @@ impl Field {
     pub fn flatten(&self) -> bool {
         self.flatten
     }
+
+    pub fn transparent(&self) -> bool {
+        self.transparent
+    }
+
+    pub fn mark_transparent(&mut self) {
+        self.transparent = true;
+    }
 }
 
 type SerAndDe<T> = (Option<T>, Option<T>);
@@ -1060,21 +1156,22 @@ fn get_ser_and_de<'a, T, F>(
 ) -> Result<SerAndDe<T>, ()>
 where
     T: 'a,
-    F: Fn(&Ctxt, &str, &str, &'a syn::Lit) -> Result<T, ()>,
+    F: Fn(&Ctxt, &Ident, &Ident, &'a syn::Lit) -> Result<T, ()>,
 {
     let mut ser_meta = Attr::none(cx, attr_name);
     let mut de_meta = Attr::none(cx, attr_name);
+    let attr_name = Ident::new(attr_name, Span::call_site());
 
     for meta in metas {
         match *meta {
             Meta(NameValue(ref meta)) if meta.ident == "serialize" => {
-                if let Ok(v) = f(cx, attr_name, meta.ident.as_ref(), &meta.lit) {
+                if let Ok(v) = f(cx, &attr_name, &meta.ident, &meta.lit) {
                     ser_meta.set(v);
                 }
             }
 
             Meta(NameValue(ref meta)) if meta.ident == "deserialize" => {
-                if let Ok(v) = f(cx, attr_name, meta.ident.as_ref(), &meta.lit) {
+                if let Ok(v) = f(cx, &attr_name, &meta.ident, &meta.lit) {
                     de_meta.set(v);
                 }
             }
@@ -1093,7 +1190,10 @@ where
     Ok((ser_meta.get(), de_meta.get()))
 }
 
-fn get_renames<'a>(cx: &Ctxt, items: &'a Punctuated<syn::NestedMeta, Token![,]>) -> Result<SerAndDe<&'a syn::LitStr>, ()> {
+fn get_renames<'a>(
+    cx: &Ctxt,
+    items: &'a Punctuated<syn::NestedMeta, Token![,]>,
+) -> Result<SerAndDe<&'a syn::LitStr>, ()> {
     get_ser_and_de(cx, "rename", items, get_lit_str)
 }
 
@@ -1120,8 +1220,8 @@ pub fn get_serde_meta_items(attr: &syn::Attribute) -> Option<Vec<syn::NestedMeta
 
 fn get_lit_str<'a>(
     cx: &Ctxt,
-    attr_name: &str,
-    meta_item_name: &str,
+    attr_name: &Ident,
+    meta_item_name: &Ident,
     lit: &'a syn::Lit,
 ) -> Result<&'a syn::LitStr, ()> {
     if let syn::Lit::Str(ref lit) = *lit {
@@ -1135,20 +1235,26 @@ fn get_lit_str<'a>(
     }
 }
 
-fn parse_lit_into_path(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn::Path, ()> {
+fn parse_lit_into_path(cx: &Ctxt, attr_name: &Ident, lit: &syn::Lit) -> Result<syn::Path, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
-    parse_lit_str(string).map_err(|_| cx.error(format!("failed to parse path: {:?}", string.value())))
+    parse_lit_str(string)
+        .map_err(|_| cx.error(format!("failed to parse path: {:?}", string.value())))
 }
 
-fn parse_lit_into_expr_path(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn::ExprPath, ()> {
+fn parse_lit_into_expr_path(
+    cx: &Ctxt,
+    attr_name: &Ident,
+    lit: &syn::Lit,
+) -> Result<syn::ExprPath, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
-    parse_lit_str(string).map_err(|_| cx.error(format!("failed to parse path: {:?}", string.value())))
+    parse_lit_str(string)
+        .map_err(|_| cx.error(format!("failed to parse path: {:?}", string.value())))
 }
 
 fn parse_lit_into_where(
     cx: &Ctxt,
-    attr_name: &str,
-    meta_item_name: &str,
+    attr_name: &Ident,
+    meta_item_name: &Ident,
     lit: &syn::Lit,
 ) -> Result<Vec<syn::WherePredicate>, ()> {
     let string = try!(get_lit_str(cx, attr_name, meta_item_name, lit));
@@ -1156,20 +1262,21 @@ fn parse_lit_into_where(
         return Ok(Vec::new());
     }
 
-    let where_string = syn::LitStr::new(&format!("where {}", string.value()), string.span);
+    let where_string = syn::LitStr::new(&format!("where {}", string.value()), string.span());
 
     parse_lit_str::<syn::WhereClause>(&where_string)
         .map(|wh| wh.predicates.into_iter().collect())
         .map_err(|err| cx.error(err))
 }
 
-fn parse_lit_into_ty(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn::Type, ()> {
+fn parse_lit_into_ty(cx: &Ctxt, attr_name: &Ident, lit: &syn::Lit) -> Result<syn::Type, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
 
     parse_lit_str(string).map_err(|_| {
         cx.error(format!(
             "failed to parse type: {} = {:?}",
-            attr_name, string.value()
+            attr_name,
+            string.value()
         ))
     })
 }
@@ -1178,7 +1285,7 @@ fn parse_lit_into_ty(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn::
 // lifetimes separated by `+`.
 fn parse_lit_into_lifetimes(
     cx: &Ctxt,
-    attr_name: &str,
+    attr_name: &Ident,
     lit: &syn::Lit,
 ) -> Result<BTreeSet<syn::Lifetime>, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
@@ -1199,17 +1306,28 @@ fn parse_lit_into_lifetimes(
     if let Ok(BorrowedLifetimes(lifetimes)) = parse_lit_str(string) {
         let mut set = BTreeSet::new();
         for lifetime in lifetimes {
-            if !set.insert(lifetime) {
+            if !set.insert(lifetime.clone()) {
                 cx.error(format!("duplicate borrowed lifetime `{}`", lifetime));
             }
         }
         return Ok(set);
     }
 
-    cx.error(format!("failed to parse borrowed lifetimes: {:?}", string.value()));
+    cx.error(format!(
+        "failed to parse borrowed lifetimes: {:?}",
+        string.value()
+    ));
     Err(())
 }
 
+fn is_implicitly_borrowed(ty: &syn::Type) -> bool {
+    is_implicitly_borrowed_reference(ty) || is_option(ty, is_implicitly_borrowed_reference)
+}
+
+fn is_implicitly_borrowed_reference(ty: &syn::Type) -> bool {
+    is_reference(ty, is_str) || is_reference(ty, is_slice_u8)
+}
+
 // Whether the type looks like it might be `std::borrow::Cow<T>` where elem="T".
 // This can have false negatives and false positives.
 //
@@ -1251,14 +1369,35 @@ fn is_cow(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
             return false;
         }
     };
-    seg.ident == "Cow"
-        && args.len() == 2
-        && match (&args[0], &args[1]) {
-            (&syn::GenericArgument::Lifetime(_), &syn::GenericArgument::Type(ref arg)) => {
-                elem(arg)
-            }
-            _ => false,
+    seg.ident == "Cow" && args.len() == 2 && match (&args[0], &args[1]) {
+        (&syn::GenericArgument::Lifetime(_), &syn::GenericArgument::Type(ref arg)) => elem(arg),
+        _ => false,
+    }
+}
+
+fn is_option(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
+    let path = match *ty {
+        syn::Type::Path(ref ty) => &ty.path,
+        _ => {
+            return false;
         }
+    };
+    let seg = match path.segments.last() {
+        Some(seg) => seg.into_value(),
+        None => {
+            return false;
+        }
+    };
+    let args = match seg.arguments {
+        syn::PathArguments::AngleBracketed(ref bracketed) => &bracketed.args,
+        _ => {
+            return false;
+        }
+    };
+    seg.ident == "Option" && args.len() == 1 && match args[0] {
+        syn::GenericArgument::Type(ref arg) => elem(arg),
+        _ => false,
+    }
 }
 
 // Whether the type looks like it might be `&T` where elem="T". This can have
@@ -1281,39 +1420,38 @@ fn is_cow(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
 //     struct S<'a> {
 //         r: &'a str,
 //     }
-fn is_rptr(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
+fn is_reference(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
     match *ty {
-        syn::Type::Reference(ref ty) => {
-            ty.mutability.is_none() && elem(&ty.elem)
-        }
+        syn::Type::Reference(ref ty) => ty.mutability.is_none() && elem(&ty.elem),
         _ => false,
     }
 }
 
 fn is_str(ty: &syn::Type) -> bool {
-    is_primitive_path(ty, "str")
+    is_primitive_type(ty, "str")
 }
 
 fn is_slice_u8(ty: &syn::Type) -> bool {
     match *ty {
-        syn::Type::Slice(ref ty) => is_primitive_path(&ty.elem, "u8"),
+        syn::Type::Slice(ref ty) => is_primitive_type(&ty.elem, "u8"),
         _ => false,
     }
 }
 
-fn is_primitive_path(ty: &syn::Type, primitive: &str) -> bool {
+fn is_primitive_type(ty: &syn::Type, primitive: &str) -> bool {
     match *ty {
-        syn::Type::Path(ref ty) => {
-            ty.qself.is_none()
-                && ty.path.leading_colon.is_none()
-                && ty.path.segments.len() == 1
-                && ty.path.segments[0].ident == primitive
-                && ty.path.segments[0].arguments.is_empty()
-        }
+        syn::Type::Path(ref ty) => ty.qself.is_none() && is_primitive_path(&ty.path, primitive),
         _ => false,
     }
 }
 
+fn is_primitive_path(path: &syn::Path, primitive: &str) -> bool {
+    path.leading_colon.is_none()
+        && path.segments.len() == 1
+        && path.segments[0].ident == primitive
+        && path.segments[0].arguments.is_empty()
+}
+
 // All lifetimes that this type could borrow from a Deserializer.
 //
 // For example a type `S<'a, 'b>` could borrow `'a` and `'b`. On the other hand
@@ -1403,21 +1541,20 @@ where
 
 fn spanned_tokens(s: &syn::LitStr) -> Result<TokenStream, ParseError> {
     let stream = try!(syn::parse_str(&s.value()));
-    Ok(respan_token_stream(stream, s.span))
+    Ok(respan_token_stream(stream, s.span()))
 }
 
 fn respan_token_stream(stream: TokenStream, span: Span) -> TokenStream {
-    stream.into_iter().map(|token| respan_token_tree(token, span)).collect()
+    stream
+        .into_iter()
+        .map(|token| respan_token_tree(token, span))
+        .collect()
 }
 
-fn respan_token_tree(token: TokenTree, span: Span) -> TokenTree {
-    TokenTree {
-        span: span,
-        kind: match token.kind {
-            TokenNode::Group(delimiter, nested) => {
-                TokenNode::Group(delimiter, respan_token_stream(nested, span))
-            }
-            other => other,
-        },
+fn respan_token_tree(mut token: TokenTree, span: Span) -> TokenTree {
+    if let TokenTree::Group(ref mut g) = token {
+        *g = Group::new(g.delimiter(), respan_token_stream(g.stream().clone(), span));
     }
+    token.set_span(span);
+    token
 }

serde_derive/src/internals/case.rs

@@ -7,7 +7,7 @@
 // except according to those terms.
 
 // See https://users.rust-lang.org/t/psa-dealing-with-warning-unused-import-std-ascii-asciiext-in-today-s-nightly/13726
-#[allow(unused_imports)]
+#[allow(deprecated, unused_imports)]
 use std::ascii::AsciiExt;
 
 use std::str::FromStr;
@@ -113,14 +113,7 @@ impl FromStr for RenameRule {
 fn rename_variants() {
     for &(original, lower, upper, camel, snake, screaming, kebab, screaming_kebab) in &[
         (
-            "Outcome",
-            "outcome",
-            "OUTCOME",
-            "outcome",
-            "outcome",
-            "OUTCOME",
-            "outcome",
-            "OUTCOME",
+            "Outcome", "outcome", "OUTCOME", "outcome", "outcome", "OUTCOME", "outcome", "OUTCOME",
         ),
         (
             "VeryTasty",
@@ -154,13 +147,7 @@ fn rename_variants() {
 fn rename_fields() {
     for &(original, upper, pascal, camel, screaming, kebab, screaming_kebab) in &[
         (
-            "outcome",
-            "OUTCOME",
-            "Outcome",
-            "outcome",
-            "OUTCOME",
-            "outcome",
-            "OUTCOME",
+            "outcome", "OUTCOME", "Outcome", "outcome", "OUTCOME", "outcome", "OUTCOME",
         ),
         (
             "very_tasty",

serde_derive/src/internals/check.rs

@@ -6,19 +6,21 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use ast::{Data, Container, Style};
-use attr::{Identifier, EnumTag};
-use Ctxt;
+use internals::ast::{Container, Data, Field, Style};
+use internals::attr::{EnumTag, Identifier};
+use internals::{Ctxt, Derive};
+use syn::{Member, Type};
 
 /// Cross-cutting checks that require looking at more than a single attrs
 /// object. Simpler checks should happen when parsing and building the attrs.
-pub fn check(cx: &Ctxt, cont: &Container) {
+pub fn check(cx: &Ctxt, cont: &mut Container, derive: Derive) {
     check_getter(cx, cont);
     check_flatten(cx, cont);
     check_identifier(cx, cont);
     check_variant_skip_attrs(cx, cont);
     check_internal_tag_field_name_conflict(cx, cont);
     check_adjacent_tag_conflict(cx, cont);
+    check_transparent(cx, cont, derive);
 }
 
 /// Getters are only allowed inside structs (not enums) with the `remote`
@@ -44,32 +46,49 @@ fn check_getter(cx: &Ctxt, cont: &Container) {
 /// Flattening has some restrictions we can test.
 fn check_flatten(cx: &Ctxt, cont: &Container) {
     match cont.data {
-        Data::Enum(_) => {
-            debug_assert!(!cont.attrs.has_flatten());
-        }
-        Data::Struct(_, _) => {
-            for field in cont.data.all_fields() {
-                if !field.attrs.flatten() {
-                    continue;
-                }
-                if field.attrs.skip_serializing() {
-                    cx.error(
-                        "#[serde(flatten] can not be combined with \
-                         #[serde(skip_serializing)]"
-                    );
-                } else if field.attrs.skip_serializing_if().is_some() {
-                    cx.error(
-                        "#[serde(flatten] can not be combined with \
-                         #[serde(skip_serializing_if = \"...\")]"
-                    );
-                } else if field.attrs.skip_deserializing() {
-                    cx.error(
-                        "#[serde(flatten] can not be combined with \
-                         #[serde(skip_deserializing)]"
-                    );
+        Data::Enum(ref variants) => {
+            for variant in variants {
+                for field in &variant.fields {
+                    check_flatten_field(cx, variant.style, field);
                 }
             }
         }
+        Data::Struct(style, ref fields) => {
+            for field in fields {
+                check_flatten_field(cx, style, field);
+            }
+        }
+    }
+}
+
+fn check_flatten_field(cx: &Ctxt, style: Style, field: &Field) {
+    if !field.attrs.flatten() {
+        return;
+    }
+    match style {
+        Style::Tuple => {
+            cx.error("#[serde(flatten)] cannot be used on tuple structs");
+        }
+        Style::Newtype => {
+            cx.error("#[serde(flatten)] cannot be used on newtype structs");
+        }
+        _ => {}
+    }
+    if field.attrs.skip_serializing() {
+        cx.error(
+            "#[serde(flatten] can not be combined with \
+             #[serde(skip_serializing)]",
+        );
+    } else if field.attrs.skip_serializing_if().is_some() {
+        cx.error(
+            "#[serde(flatten] can not be combined with \
+             #[serde(skip_serializing_if = \"...\")]",
+        );
+    } else if field.attrs.skip_deserializing() {
+        cx.error(
+            "#[serde(flatten] can not be combined with \
+             #[serde(skip_deserializing)]",
+        );
     }
 }
 
@@ -154,17 +173,14 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
                 ));
             }
 
-            for (i, field) in variant.fields.iter().enumerate() {
-                let ident = field
-                    .ident
-                    .as_ref()
-                    .map_or_else(|| format!("{}", i), |ident| format!("`{}`", ident));
+            for field in &variant.fields {
+                let member = member_message(&field.member);
 
                 if field.attrs.skip_serializing() {
                     cx.error(format!(
                         "variant `{}` cannot have both #[serde(serialize_with)] and \
                          a field {} marked with #[serde(skip_serializing)]",
-                        variant.ident, ident
+                        variant.ident, member
                     ));
                 }
 
@@ -172,7 +188,7 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
                     cx.error(format!(
                         "variant `{}` cannot have both #[serde(serialize_with)] and \
                          a field {} marked with #[serde(skip_serializing_if)]",
-                        variant.ident, ident
+                        variant.ident, member
                     ));
                 }
             }
@@ -187,17 +203,14 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
                 ));
             }
 
-            for (i, field) in variant.fields.iter().enumerate() {
+            for field in &variant.fields {
                 if field.attrs.skip_deserializing() {
-                    let ident = field
-                        .ident
-                        .as_ref()
-                        .map_or_else(|| format!("{}", i), |ident| format!("`{}`", ident));
+                    let member = member_message(&field.member);
 
                     cx.error(format!(
                         "variant `{}` cannot have both #[serde(deserialize_with)] \
                          and a field {} marked with #[serde(skip_deserializing)]",
-                        variant.ident, ident
+                        variant.ident, member
                     ));
                 }
             }
@@ -209,10 +222,7 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
 /// the same as either one of its fields, as this would result in
 /// duplicate keys in the serialized output and/or ambiguity in
 /// the to-be-deserialized input.
-fn check_internal_tag_field_name_conflict(
-    cx: &Ctxt,
-    cont: &Container,
-) {
+fn check_internal_tag_field_name_conflict(cx: &Ctxt, cont: &Container) {
     let variants = match cont.data {
         Data::Enum(ref variants) => variants,
         Data::Struct(_, _) => return,
@@ -224,10 +234,7 @@ fn check_internal_tag_field_name_conflict(
     };
 
     let diagnose_conflict = || {
-        let message = format!(
-            "variant field name `{}` conflicts with internal tag",
-            tag
-        );
+        let message = format!("variant field name `{}` conflicts with internal tag", tag);
         cx.error(message);
     };
 
@@ -246,8 +253,8 @@ fn check_internal_tag_field_name_conflict(
                         return;
                     }
                 }
-            },
-            Style::Unit | Style::Newtype | Style::Tuple => {},
+            }
+            Style::Unit | Style::Newtype | Style::Tuple => {}
         }
     }
 }
@@ -256,7 +263,10 @@ fn check_internal_tag_field_name_conflict(
 /// contents tag must differ, for the same reason.
 fn check_adjacent_tag_conflict(cx: &Ctxt, cont: &Container) {
     let (type_tag, content_tag) = match *cont.attrs.tag() {
-        EnumTag::Adjacent { ref tag, ref content } => (tag, content),
+        EnumTag::Adjacent {
+            ref tag,
+            ref content,
+        } => (tag, content),
         EnumTag::Internal { .. } | EnumTag::External | EnumTag::None => return,
     };
 
@@ -268,3 +278,78 @@ fn check_adjacent_tag_conflict(cx: &Ctxt, cont: &Container) {
         cx.error(message);
     }
 }
+
+/// Enums and unit structs cannot be transparent.
+fn check_transparent(cx: &Ctxt, cont: &mut Container, derive: Derive) {
+    if !cont.attrs.transparent() {
+        return;
+    }
+
+    if cont.attrs.type_from().is_some() {
+        cx.error("#[serde(transparent)] is not allowed with #[serde(from = \"...\")]");
+    }
+
+    if cont.attrs.type_into().is_some() {
+        cx.error("#[serde(transparent)] is not allowed with #[serde(into = \"...\")]");
+    }
+
+    let fields = match cont.data {
+        Data::Enum(_) => {
+            cx.error("#[serde(transparent)] is not allowed on an enum");
+            return;
+        }
+        Data::Struct(Style::Unit, _) => {
+            cx.error("#[serde(transparent)] is not allowed on a unit struct");
+            return;
+        }
+        Data::Struct(_, ref mut fields) => fields,
+    };
+
+    let mut transparent_field = None;
+
+    for field in fields {
+        if allow_transparent(field, derive) {
+            if transparent_field.is_some() {
+                cx.error(
+                    "#[serde(transparent)] requires struct to have at most one transparent field",
+                );
+                return;
+            }
+            transparent_field = Some(field);
+        }
+    }
+
+    match transparent_field {
+        Some(transparent_field) => transparent_field.attrs.mark_transparent(),
+        None => match derive {
+            Derive::Serialize => {
+                cx.error("#[serde(transparent)] requires at least one field that is not skipped");
+            }
+            Derive::Deserialize => {
+                cx.error("#[serde(transparent)] requires at least one field that is neither skipped nor has a default");
+            }
+        },
+    }
+}
+
+fn member_message(member: &Member) -> String {
+    match *member {
+        Member::Named(ref ident) => format!("`{}`", ident),
+        Member::Unnamed(ref i) => i.index.to_string(),
+    }
+}
+
+fn allow_transparent(field: &Field, derive: Derive) -> bool {
+    if let Type::Path(ref ty) = *field.ty {
+        if let Some(seg) = ty.path.segments.last() {
+            if seg.into_value().ident == "PhantomData" {
+                return false;
+            }
+        }
+    }
+
+    match derive {
+        Derive::Serialize => !field.attrs.skip_serializing(),
+        Derive::Deserialize => !field.attrs.skip_deserializing() && field.attrs.default().is_none(),
+    }
+}

serde_derive/src/internals/ctxt.rs

@@ -6,8 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::fmt::Display;
 use std::cell::RefCell;
+use std::fmt::Display;
 use std::thread;
 
 #[derive(Default)]

serde_derive/src/internals/mod.rs

@@ -0,0 +1,22 @@
+// Copyright 2017 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub mod ast;
+pub mod attr;
+
+mod ctxt;
+pub use self::ctxt::Ctxt;
+
+mod case;
+mod check;
+
+#[derive(Copy, Clone)]
+pub enum Derive {
+    Serialize,
+    Deserialize,
+}

serde_derive/src/lib.rs

@@ -22,9 +22,24 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.34")]
-#![cfg_attr(feature = "cargo-clippy", allow(enum_variant_names, redundant_field_names,
-                                            too_many_arguments, used_underscore_binding))]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.67")]
+#![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
+// Whitelisted clippy lints
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(
+        enum_variant_names, redundant_field_names, too_many_arguments, used_underscore_binding,
+        cyclomatic_complexity, needless_pass_by_value
+    )
+)]
+// Whitelisted clippy_pedantic lints
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(
+        items_after_statements, doc_markdown, stutter, similar_names, use_self, single_match_else,
+        enum_glob_use, match_same_arms, filter_map, cast_possible_truncation, indexing_slicing,
+    )
+)]
 // The `quote!` macro requires deep recursion.
 #![recursion_limit = "512"]
 
@@ -33,11 +48,11 @@ extern crate quote;
 #[macro_use]
 extern crate syn;
 
-extern crate serde_derive_internals as internals;
-
 extern crate proc_macro;
 extern crate proc_macro2;
 
+mod internals;
+
 use proc_macro::TokenStream;
 use syn::DeriveInput;
 
@@ -46,23 +61,29 @@ mod bound;
 #[macro_use]
 mod fragment;
 
-mod ser;
 mod de;
+mod pretend;
+mod ser;
+mod try;
 
 #[proc_macro_derive(Serialize, attributes(serde))]
 pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let input: DeriveInput = syn::parse(input).unwrap();
-    match ser::expand_derive_serialize(&input) {
-        Ok(expanded) => expanded.into(),
-        Err(msg) => panic!(msg),
-    }
+    ser::expand_derive_serialize(&input)
+        .unwrap_or_else(compile_error)
+        .into()
 }
 
 #[proc_macro_derive(Deserialize, attributes(serde))]
 pub fn derive_deserialize(input: TokenStream) -> TokenStream {
     let input: DeriveInput = syn::parse(input).unwrap();
-    match de::expand_derive_deserialize(&input) {
-        Ok(expanded) => expanded.into(),
-        Err(msg) => panic!(msg),
+    de::expand_derive_deserialize(&input)
+        .unwrap_or_else(compile_error)
+        .into()
+}
+
+fn compile_error(message: String) -> proc_macro2::TokenStream {
+    quote! {
+        compile_error!(#message);
     }
 }

serde_derive/src/pretend.rs

@@ -0,0 +1,140 @@
+use proc_macro2::{Span, TokenStream};
+use syn::Ident;
+
+use internals::ast::{Container, Data, Field, Style};
+
+// Suppress dead_code warnings that would otherwise appear when using a remote
+// derive. Other than this pretend code, a struct annotated with remote derive
+// never has its fields referenced and an enum annotated with remote derive
+// never has its variants constructed.
+//
+//     warning: field is never used: `i`
+//      --> src/main.rs:4:20
+//       |
+//     4 | struct StructDef { i: i32 }
+//       |                    ^^^^^^
+//
+//     warning: variant is never constructed: `V`
+//      --> src/main.rs:8:16
+//       |
+//     8 | enum EnumDef { V }
+//       |                ^
+//
+pub fn pretend_used(cont: &Container) -> TokenStream {
+    let pretend_fields = pretend_fields_used(cont);
+    let pretend_variants = pretend_variants_used(cont);
+
+    quote! {
+        #pretend_fields
+        #pretend_variants
+    }
+}
+
+// For structs with named fields, expands to:
+//
+//     match None::<T> {
+//         Some(T { a: ref __v0, b: ref __v1 }) => {}
+//         _ => {}
+//     }
+//
+// For enums, expands to the following but only including struct variants:
+//
+//     match None::<T> {
+//         Some(T::A { a: ref __v0 }) => {}
+//         Some(T::B { b: ref __v0 }) => {}
+//         _ => {}
+//     }
+//
+// The `ref` is important in case the user has written a Drop impl on their
+// type. Rust does not allow destructuring a struct or enum that has a Drop
+// impl.
+fn pretend_fields_used(cont: &Container) -> TokenStream {
+    let type_ident = &cont.ident;
+    let (_, ty_generics, _) = cont.generics.split_for_impl();
+
+    let patterns = match cont.data {
+        Data::Enum(ref variants) => variants
+            .iter()
+            .filter_map(|variant| match variant.style {
+                Style::Struct => {
+                    let variant_ident = &variant.ident;
+                    let pat = struct_pattern(&variant.fields);
+                    Some(quote!(#type_ident::#variant_ident #pat))
+                }
+                _ => None,
+            })
+            .collect::<Vec<_>>(),
+        Data::Struct(Style::Struct, ref fields) => {
+            let pat = struct_pattern(fields);
+            vec![quote!(#type_ident #pat)]
+        }
+        Data::Struct(_, _) => {
+            return quote!();
+        }
+    };
+
+    quote! {
+        match _serde::export::None::<#type_ident #ty_generics> {
+            #(
+                _serde::export::Some(#patterns) => {}
+            )*
+            _ => {}
+        }
+    }
+}
+
+// Expands to one of these per enum variant:
+//
+//     match None {
+//         Some((__v0, __v1,)) => {
+//             let _ = E::V { a: __v0, b: __v1 };
+//         }
+//         _ => {}
+//     }
+//
+fn pretend_variants_used(cont: &Container) -> TokenStream {
+    let variants = match cont.data {
+        Data::Enum(ref variants) => variants,
+        Data::Struct(_, _) => {
+            return quote!();
+        }
+    };
+
+    let type_ident = &cont.ident;
+    let (_, ty_generics, _) = cont.generics.split_for_impl();
+    let turbofish = ty_generics.as_turbofish();
+
+    let cases = variants.iter().map(|variant| {
+        let variant_ident = &variant.ident;
+        let placeholders = &(0..variant.fields.len())
+            .map(|i| Ident::new(&format!("__v{}", i), Span::call_site()))
+            .collect::<Vec<_>>();
+
+        let pat = match variant.style {
+            Style::Struct => {
+                let members = variant.fields.iter().map(|field| &field.member);
+                quote!({ #(#members: #placeholders),* })
+            }
+            Style::Tuple | Style::Newtype => quote!(( #(#placeholders),* )),
+            Style::Unit => quote!(),
+        };
+
+        quote! {
+            match _serde::export::None {
+                _serde::export::Some((#(#placeholders,)*)) => {
+                    let _ = #type_ident::#variant_ident #turbofish #pat;
+                }
+                _ => {}
+            }
+        }
+    });
+
+    quote!(#(#cases)*)
+}
+
+fn struct_pattern(fields: &[Field]) -> TokenStream {
+    let members = fields.iter().map(|field| &field.member);
+    let placeholders =
+        (0..fields.len()).map(|i| Ident::new(&format!("__v{}", i), Span::call_site()));
+    quote!({ #(#members: ref #placeholders),* })
+}

serde_derive/src/ser.rs

@@ -6,38 +6,39 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use syn::{self, Ident, Index, Member};
+use proc_macro2::{Span, TokenStream};
 use syn::spanned::Spanned;
-use quote::Tokens;
-use proc_macro2::Span;
+use syn::{self, Ident, Index, Member};
 
 use bound;
 use fragment::{Fragment, Match, Stmts};
-use internals::ast::{Data, Container, Field, Style, Variant};
-use internals::{attr, Ctxt};
+use internals::ast::{Container, Data, Field, Style, Variant};
+use internals::{attr, Ctxt, Derive};
+use pretend;
+use try;
 
-use std::u32;
-
-pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<Tokens, String> {
+pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<TokenStream, String> {
     let ctxt = Ctxt::new();
-    let cont = Container::from_ast(&ctxt, input);
+    let cont = Container::from_ast(&ctxt, input, Derive::Serialize);
     precondition(&ctxt, &cont);
     try!(ctxt.check());
 
     let ident = &cont.ident;
     let params = Parameters::new(&cont);
     let (impl_generics, ty_generics, where_clause) = params.generics.split_for_impl();
-    let dummy_const = Ident::new(&format!("_IMPL_SERIALIZE_FOR_{}", ident), Span::def_site());
+    let dummy_const = Ident::new(&format!("_IMPL_SERIALIZE_FOR_{}", ident), Span::call_site());
     let body = Stmts(serialize_body(&cont, &params));
 
     let impl_block = if let Some(remote) = cont.attrs.remote() {
         let vis = &input.vis;
-        let fun = quote_spanned!(Span::call_site()=> serialize);
+        let used = pretend::pretend_used(&cont);
         quote! {
             impl #impl_generics #ident #ty_generics #where_clause {
-                #vis fn #fun<__S>(__self: &#remote #ty_generics, __serializer: __S) -> _serde::export::Result<__S::Ok, __S::Error>
-                    where __S: _serde::Serializer
+                #vis fn serialize<__S>(__self: &#remote #ty_generics, __serializer: __S) -> _serde::export::Result<__S::Ok, __S::Error>
+                where
+                    __S: _serde::Serializer,
                 {
+                    #used
                     #body
                 }
             }
@@ -47,7 +48,8 @@ pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<Tokens, Strin
             #[automatically_derived]
             impl #impl_generics _serde::Serialize for #ident #ty_generics #where_clause {
                 fn serialize<__S>(&self, __serializer: __S) -> _serde::export::Result<__S::Ok, __S::Error>
-                    where __S: _serde::Serializer
+                where
+                    __S: _serde::Serializer,
                 {
                     #body
                 }
@@ -55,10 +57,12 @@ pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<Tokens, Strin
         }
     };
 
+    let try_replacement = try::replacement();
     let generated = quote! {
         #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
         const #dummy_const: () = {
             extern crate serde as _serde;
+            #try_replacement
             #impl_block
         };
     };
@@ -98,14 +102,14 @@ impl Parameters {
     fn new(cont: &Container) -> Self {
         let is_remote = cont.attrs.remote().is_some();
         let self_var = if is_remote {
-            Ident::new("__self", Span::def_site())
+            Ident::new("__self", Span::call_site())
         } else {
-            Ident::new("self", Span::def_site())
+            Ident::new("self", Span::call_site())
         };
 
         let this = match cont.attrs.remote() {
             Some(remote) => remote.clone(),
-            None => cont.ident.into(),
+            None => cont.ident.clone().into(),
         };
 
         let generics = build_generics(cont);
@@ -120,8 +124,8 @@ impl Parameters {
 
     /// Type name to use in error messages and `&'static str` arguments to
     /// various Serializer methods.
-    fn type_name(&self) -> &str {
-        self.this.segments.last().unwrap().value().ident.as_ref()
+    fn type_name(&self) -> String {
+        self.this.segments.last().unwrap().value().ident.to_string()
     }
 }
 
@@ -133,6 +137,9 @@ fn build_generics(cont: &Container) -> syn::Generics {
     let generics =
         bound::with_where_predicates_from_fields(cont, &generics, attr::Field::ser_bound);
 
+    let generics =
+        bound::with_where_predicates_from_variants(cont, &generics, attr::Variant::ser_bound);
+
     match cont.attrs.ser_bound() {
         Some(predicates) => bound::with_where_predicates(&generics, predicates),
         None => bound::with_bound(
@@ -145,31 +152,31 @@ fn build_generics(cont: &Container) -> syn::Generics {
 }
 
 // Fields with a `skip_serializing` or `serialize_with` attribute, or which
-// belong to a variant with a `serialize_with` attribute, are not serialized by
-// us so we do not generate a bound. Fields with a `bound` attribute specify
-// their own bound so we do not generate one. All other fields may need a `T:
-// Serialize` bound where T is the type of the field.
+// belong to a variant with a 'skip_serializing` or `serialize_with` attribute,
+// are not serialized by us so we do not generate a bound. Fields with a `bound`
+// attribute specify their own bound so we do not generate one. All other fields
+// may need a `T: Serialize` bound where T is the type of the field.
 fn needs_serialize_bound(field: &attr::Field, variant: Option<&attr::Variant>) -> bool {
     !field.skip_serializing() && field.serialize_with().is_none() && field.ser_bound().is_none()
-        && variant.map_or(true, |variant| variant.serialize_with().is_none())
+        && variant.map_or(true, |variant| {
+            !variant.skip_serializing()
+                && variant.serialize_with().is_none()
+                && variant.ser_bound().is_none()
+        })
 }
 
 fn serialize_body(cont: &Container, params: &Parameters) -> Fragment {
-    if let Some(type_into) = cont.attrs.type_into() {
+    if cont.attrs.transparent() {
+        serialize_transparent(cont, params)
+    } else if let Some(type_into) = cont.attrs.type_into() {
         serialize_into(params, type_into)
     } else {
         match cont.data {
             Data::Enum(ref variants) => serialize_enum(params, variants, &cont.attrs),
             Data::Struct(Style::Struct, ref fields) => {
-                if fields.iter().any(|field| field.ident.is_none()) {
-                    panic!("struct has unnamed fields");
-                }
                 serialize_struct(params, fields, &cont.attrs)
             }
             Data::Struct(Style::Tuple, ref fields) => {
-                if fields.iter().any(|field| field.ident.is_some()) {
-                    panic!("tuple struct has named fields");
-                }
                 serialize_tuple_struct(params, fields, &cont.attrs)
             }
             Data::Struct(Style::Newtype, ref fields) => {
@@ -180,6 +187,26 @@ fn serialize_body(cont: &Container, params: &Parameters) -> Fragment {
     }
 }
 
+fn serialize_transparent(cont: &Container, params: &Parameters) -> Fragment {
+    let fields = match cont.data {
+        Data::Struct(_, ref fields) => fields,
+        Data::Enum(_) => unreachable!(),
+    };
+
+    let self_var = &params.self_var;
+    let transparent_field = fields.iter().find(|f| f.attrs.transparent()).unwrap();
+    let member = &transparent_field.member;
+
+    let path = match transparent_field.attrs.serialize_with() {
+        Some(path) => quote!(#path),
+        None => quote!(_serde::Serialize::serialize),
+    };
+
+    quote_block! {
+        #path(&#self_var.#member, __serializer)
+    }
+}
+
 fn serialize_into(params: &Parameters, type_into: &syn::Type) -> Fragment {
     let self_var = &params.self_var;
     quote_block! {
@@ -204,15 +231,19 @@ fn serialize_newtype_struct(
 ) -> Fragment {
     let type_name = cattrs.name().serialize_name();
 
-    let mut field_expr = get_member(params, field, &Member::Unnamed(Index {
-        index: 0,
-        span: Span::call_site(),
-    }));
+    let mut field_expr = get_member(
+        params,
+        field,
+        &Member::Unnamed(Index {
+            index: 0,
+            span: Span::call_site(),
+        }),
+    );
     if let Some(path) = field.attrs.serialize_with() {
         field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
     }
 
-    let span = Span::def_site().located_at(field.original.span());
+    let span = field.original.span();
     let func = quote_spanned!(span=> _serde::Serializer::serialize_newtype_struct);
     quote_expr! {
         #func(__serializer, #type_name, #field_expr)
@@ -224,16 +255,32 @@ fn serialize_tuple_struct(
     fields: &[Field],
     cattrs: &attr::Container,
 ) -> Fragment {
-    let serialize_stmts = serialize_tuple_struct_visitor(
-        fields,
-        params,
-        false,
-        &TupleTrait::SerializeTupleStruct,
-    );
+    let serialize_stmts =
+        serialize_tuple_struct_visitor(fields, params, false, &TupleTrait::SerializeTupleStruct);
 
     let type_name = cattrs.name().serialize_name();
-    let len = serialize_stmts.len();
-    let let_mut = mut_if(len > 0);
+
+    let mut serialized_fields = fields
+        .iter()
+        .enumerate()
+        .filter(|&(_, ref field)| !field.attrs.skip_serializing())
+        .peekable();
+
+    let let_mut = mut_if(serialized_fields.peek().is_some());
+
+    let len = serialized_fields
+        .map(|(i, field)| match field.attrs.skip_serializing_if() {
+            None => quote!(1),
+            Some(path) => {
+                let index = syn::Index {
+                    index: i as u32,
+                    span: Span::call_site(),
+                };
+                let field_expr = get_member(params, field, &Member::Unnamed(index));
+                quote!(if #path(#field_expr) { 0 } else { 1 })
+            }
+        })
+        .fold(quote!(0), |sum, expr| quote!(#sum + #expr));
 
     quote_block! {
         let #let_mut __serde_state = try!(_serde::Serializer::serialize_tuple_struct(__serializer, #type_name, #len));
@@ -243,7 +290,7 @@ fn serialize_tuple_struct(
 }
 
 fn serialize_struct(params: &Parameters, fields: &[Field], cattrs: &attr::Container) -> Fragment {
-    assert!(fields.len() as u64 <= u64::from(u32::MAX));
+    assert!(fields.len() as u64 <= u64::from(u32::max_value()));
 
     if cattrs.has_flatten() {
         serialize_struct_as_map(params, fields, cattrs)
@@ -252,13 +299,13 @@ fn serialize_struct(params: &Parameters, fields: &[Field], cattrs: &attr::Contai
     }
 }
 
-fn serialize_struct_as_struct(params: &Parameters, fields: &[Field], cattrs: &attr::Container) -> Fragment {
-    let serialize_fields = serialize_struct_visitor(
-        fields,
-        params,
-        false,
-        &StructTrait::SerializeStruct,
-    );
+fn serialize_struct_as_struct(
+    params: &Parameters,
+    fields: &[Field],
+    cattrs: &attr::Container,
+) -> Fragment {
+    let serialize_fields =
+        serialize_struct_visitor(fields, params, false, &StructTrait::SerializeStruct);
 
     let type_name = cattrs.name().serialize_name();
 
@@ -273,8 +320,7 @@ fn serialize_struct_as_struct(params: &Parameters, fields: &[Field], cattrs: &at
         .map(|field| match field.attrs.skip_serializing_if() {
             None => quote!(1),
             Some(path) => {
-                let ident = field.ident.expect("struct has unnamed fields");
-                let field_expr = get_member(params, field, &Member::Named(ident));
+                let field_expr = get_member(params, field, &field.member);
                 quote!(if #path(#field_expr) { 0 } else { 1 })
             }
         })
@@ -287,13 +333,13 @@ fn serialize_struct_as_struct(params: &Parameters, fields: &[Field], cattrs: &at
     }
 }
 
-fn serialize_struct_as_map(params: &Parameters, fields: &[Field], cattrs: &attr::Container) -> Fragment {
-    let serialize_fields = serialize_struct_visitor(
-        fields,
-        params,
-        false,
-        &StructTrait::SerializeMap,
-    );
+fn serialize_struct_as_map(
+    params: &Parameters,
+    fields: &[Field],
+    cattrs: &attr::Container,
+) -> Fragment {
+    let serialize_fields =
+        serialize_struct_visitor(fields, params, false, &StructTrait::SerializeMap);
 
     let mut serialized_fields = fields
         .iter()
@@ -309,8 +355,7 @@ fn serialize_struct_as_map(params: &Parameters, fields: &[Field], cattrs: &attr:
             .map(|field| match field.attrs.skip_serializing_if() {
                 None => quote!(1),
                 Some(path) => {
-                    let ident = field.ident.expect("struct has unnamed fields");
-                    let field_expr = get_member(params, field, &Member::Named(ident));
+                    let field_expr = get_member(params, field, &field.member);
                     quote!(if #path(#field_expr) { 0 } else { 1 })
                 }
             })
@@ -326,7 +371,7 @@ fn serialize_struct_as_map(params: &Parameters, fields: &[Field], cattrs: &attr:
 }
 
 fn serialize_enum(params: &Parameters, variants: &[Variant], cattrs: &attr::Container) -> Fragment {
-    assert!(variants.len() as u64 <= u64::from(u32::MAX));
+    assert!(variants.len() as u64 <= u64::from(u32::max_value()));
 
     let self_var = &params.self_var;
 
@@ -350,9 +395,9 @@ fn serialize_variant(
     variant: &Variant,
     variant_index: u32,
     cattrs: &attr::Container,
-) -> Tokens {
+) -> TokenStream {
     let this = &params.this;
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     if variant.attrs.skip_serializing() {
         let skipped_msg = format!(
@@ -385,19 +430,16 @@ fn serialize_variant(
                 }
             }
             Style::Tuple => {
-                let field_names =
-                    (0..variant.fields.len()).map(|i| Ident::new(&format!("__field{}", i), Span::def_site()));
+                let field_names = (0..variant.fields.len())
+                    .map(|i| Ident::new(&format!("__field{}", i), Span::call_site()));
                 quote! {
                     #this::#variant_ident(#(ref #field_names),*)
                 }
             }
             Style::Struct => {
-                let fields = variant
-                    .fields
-                    .iter()
-                    .map(|f| f.ident.expect("struct variant has unnamed fields"));
+                let members = variant.fields.iter().map(|f| &f.member);
                 quote! {
-                    #this::#variant_ident { #(ref #fields),* }
+                    #this::#variant_ident { #(ref #members),* }
                 }
             }
         };
@@ -503,7 +545,7 @@ fn serialize_internally_tagged_variant(
     let variant_name = variant.attrs.name().serialize_name();
 
     let enum_ident_str = params.type_name();
-    let variant_ident_str = variant.ident.as_ref();
+    let variant_ident_str = variant.ident.to_string();
 
     if let Some(path) = variant.attrs.serialize_with() {
         let ser = wrap_serialize_variant_with(params, path, variant);
@@ -594,9 +636,15 @@ fn serialize_adjacently_tagged_variant(
                     field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
                 }
 
-                quote_expr! {
-                    _serde::Serialize::serialize(#field_expr, __serializer)
-                }
+                return quote_block! {
+                    let mut __struct = try!(_serde::Serializer::serialize_struct(
+                        __serializer, #type_name, 2));
+                    try!(_serde::ser::SerializeStruct::serialize_field(
+                        &mut __struct, #tag, #variant_name));
+                    try!(_serde::ser::SerializeStruct::serialize_field(
+                        &mut __struct, #content, #field_expr));
+                    _serde::ser::SerializeStruct::end(__struct)
+                };
             }
             Style::Tuple => {
                 serialize_tuple_variant(TupleVariant::Untagged, params, &variant.fields)
@@ -619,20 +667,16 @@ fn serialize_adjacently_tagged_variant(
                 unreachable!()
             }
         }
-        Style::Newtype => vec![Ident::new("__field0", Span::def_site())],
+        Style::Newtype => vec![Member::Named(Ident::new("__field0", Span::call_site()))],
         Style::Tuple => (0..variant.fields.len())
-            .map(|i| Ident::new(&format!("__field{}", i), Span::def_site()))
-            .collect(),
-        Style::Struct => variant
-            .fields
-            .iter()
-            .map(|f| f.ident.expect("struct variant has unnamed fields"))
+            .map(|i| Member::Named(Ident::new(&format!("__field{}", i), Span::call_site())))
             .collect(),
+        Style::Struct => variant.fields.iter().map(|f| f.member.clone()).collect(),
     };
 
     let (_, ty_generics, where_clause) = params.generics.split_for_impl();
 
-    let wrapper_generics = if let Style::Unit = variant.style {
+    let wrapper_generics = if fields_ident.is_empty() {
         params.generics.clone()
     } else {
         bound::with_lifetime_bound(&params.generics, "'__a")
@@ -647,7 +691,8 @@ fn serialize_adjacently_tagged_variant(
 
         impl #wrapper_impl_generics _serde::Serialize for __AdjacentlyTagged #wrapper_ty_generics #where_clause {
             fn serialize<__S>(&self, __serializer: __S) -> _serde::export::Result<__S::Ok, __S::Error>
-                where __S: _serde::Serializer
+            where
+                __S: _serde::Serializer,
             {
                 let (#(#fields_ident,)*) = self.data;
                 #inner
@@ -725,8 +770,23 @@ fn serialize_tuple_variant(
 
     let serialize_stmts = serialize_tuple_struct_visitor(fields, params, true, &tuple_trait);
 
-    let len = serialize_stmts.len();
-    let let_mut = mut_if(len > 0);
+    let mut serialized_fields = fields
+        .iter()
+        .enumerate()
+        .filter(|&(_, ref field)| !field.attrs.skip_serializing())
+        .peekable();
+
+    let let_mut = mut_if(serialized_fields.peek().is_some());
+
+    let len = serialized_fields
+        .map(|(i, field)| match field.attrs.skip_serializing_if() {
+            None => quote!(1),
+            Some(path) => {
+                let field_expr = Ident::new(&format!("__field{}", i), Span::call_site());
+                quote!(if #path(#field_expr) { 0 } else { 1 })
+            }
+        })
+        .fold(quote!(0), |sum, expr| quote!(#sum + #expr));
 
     match context {
         TupleVariant::ExternallyTagged {
@@ -775,13 +835,15 @@ fn serialize_struct_variant<'a>(
     fields: &[Field],
     name: &str,
 ) -> Fragment {
+    if fields.iter().any(|field| field.attrs.flatten()) {
+        return serialize_struct_variant_with_flatten(context, params, fields, name);
+    }
+
     let struct_trait = match context {
-        StructVariant::ExternallyTagged { .. } => (
-            StructTrait::SerializeStructVariant
-        ),
-        StructVariant::InternallyTagged { .. } | StructVariant::Untagged => (
-            StructTrait::SerializeStruct
-        ),
+        StructVariant::ExternallyTagged { .. } => (StructTrait::SerializeStructVariant),
+        StructVariant::InternallyTagged { .. } | StructVariant::Untagged => {
+            (StructTrait::SerializeStruct)
+        }
     };
 
     let serialize_fields = serialize_struct_visitor(fields, params, true, &struct_trait);
@@ -795,10 +857,10 @@ fn serialize_struct_variant<'a>(
 
     let len = serialized_fields
         .map(|field| {
-            let ident = field.ident.expect("struct has unnamed fields");
+            let member = &field.member;
 
             match field.attrs.skip_serializing_if() {
-                Some(path) => quote!(if #path(#ident) { 0 } else { 1 }),
+                Some(path) => quote!(if #path(#member) { 0 } else { 1 }),
                 None => quote!(1),
             }
         })
@@ -851,24 +913,115 @@ fn serialize_struct_variant<'a>(
     }
 }
 
+fn serialize_struct_variant_with_flatten<'a>(
+    context: StructVariant<'a>,
+    params: &Parameters,
+    fields: &[Field],
+    name: &str,
+) -> Fragment {
+    let struct_trait = StructTrait::SerializeMap;
+    let serialize_fields = serialize_struct_visitor(fields, params, true, &struct_trait);
+
+    let mut serialized_fields = fields
+        .iter()
+        .filter(|&field| !field.attrs.skip_serializing())
+        .peekable();
+
+    let let_mut = mut_if(serialized_fields.peek().is_some());
+
+    match context {
+        StructVariant::ExternallyTagged {
+            variant_index,
+            variant_name,
+        } => {
+            let this = &params.this;
+            let fields_ty = fields.iter().map(|f| &f.ty);
+            let members = &fields.iter().map(|f| &f.member).collect::<Vec<_>>();
+
+            let (_, ty_generics, where_clause) = params.generics.split_for_impl();
+            let wrapper_generics = bound::with_lifetime_bound(&params.generics, "'__a");
+            let (wrapper_impl_generics, wrapper_ty_generics, _) = wrapper_generics.split_for_impl();
+
+            quote_block! {
+                struct __EnumFlatten #wrapper_generics #where_clause {
+                    data: (#(&'__a #fields_ty,)*),
+                    phantom: _serde::export::PhantomData<#this #ty_generics>,
+                }
+
+                impl #wrapper_impl_generics _serde::Serialize for __EnumFlatten #wrapper_ty_generics #where_clause {
+                    fn serialize<__S>(&self, __serializer: __S) -> _serde::export::Result<__S::Ok, __S::Error>
+                    where
+                        __S: _serde::Serializer,
+                    {
+                        let (#(#members,)*) = self.data;
+                        let #let_mut __serde_state = try!(_serde::Serializer::serialize_map(
+                            __serializer,
+                            _serde::export::None));
+                        #(#serialize_fields)*
+                        _serde::ser::SerializeMap::end(__serde_state)
+                    }
+                }
+
+                _serde::Serializer::serialize_newtype_variant(
+                    __serializer,
+                    #name,
+                    #variant_index,
+                    #variant_name,
+                    &__EnumFlatten {
+                        data: (#(#members,)*),
+                        phantom: _serde::export::PhantomData::<#this #ty_generics>,
+                    })
+            }
+        }
+        StructVariant::InternallyTagged { tag, variant_name } => {
+            quote_block! {
+                let #let_mut __serde_state = try!(_serde::Serializer::serialize_map(
+                    __serializer,
+                    _serde::export::None));
+                try!(_serde::ser::SerializeMap::serialize_entry(
+                    &mut __serde_state,
+                    #tag,
+                    #variant_name,
+                ));
+                #(#serialize_fields)*
+                _serde::ser::SerializeMap::end(__serde_state)
+            }
+        }
+        StructVariant::Untagged => {
+            quote_block! {
+                let #let_mut __serde_state = try!(_serde::Serializer::serialize_map(
+                    __serializer,
+                    _serde::export::None));
+                #(#serialize_fields)*
+                _serde::ser::SerializeMap::end(__serde_state)
+            }
+        }
+    }
+}
+
 fn serialize_tuple_struct_visitor(
     fields: &[Field],
     params: &Parameters,
     is_enum: bool,
     tuple_trait: &TupleTrait,
-) -> Vec<Tokens> {
+) -> Vec<TokenStream> {
     fields
         .iter()
         .enumerate()
+        .filter(|&(_, ref field)| !field.attrs.skip_serializing())
         .map(|(i, field)| {
             let mut field_expr = if is_enum {
-                let id = Ident::new(&format!("__field{}", i), Span::def_site());
+                let id = Ident::new(&format!("__field{}", i), Span::call_site());
                 quote!(#id)
             } else {
-                get_member(params, field, &Member::Unnamed(Index {
-                    index: i as u32,
-                    span: Span::call_site(),
-                }))
+                get_member(
+                    params,
+                    field,
+                    &Member::Unnamed(Index {
+                        index: i as u32,
+                        span: Span::call_site(),
+                    }),
+                )
             };
 
             let skip = field
@@ -880,7 +1033,7 @@ fn serialize_tuple_struct_visitor(
                 field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
             }
 
-            let span = Span::def_site().located_at(field.original.span());
+            let span = field.original.span();
             let func = tuple_trait.serialize_element(span);
             let ser = quote! {
                 try!(#func(&mut __serde_state, #field_expr));
@@ -899,17 +1052,17 @@ fn serialize_struct_visitor(
     params: &Parameters,
     is_enum: bool,
     struct_trait: &StructTrait,
-) -> Vec<Tokens> {
+) -> Vec<TokenStream> {
     fields
         .iter()
         .filter(|&field| !field.attrs.skip_serializing())
         .map(|field| {
-            let field_ident = field.ident.expect("struct has unnamed field");
+            let member = &field.member;
 
             let mut field_expr = if is_enum {
-                quote!(#field_ident)
+                quote!(#member)
             } else {
-                get_member(params, field, &Member::Named(field_ident))
+                get_member(params, field, &member)
             };
 
             let key_expr = field.attrs.name().serialize_name();
@@ -923,7 +1076,7 @@ fn serialize_struct_visitor(
                 field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
             }
 
-            let span = Span::def_site().located_at(field.original.span());
+            let span = field.original.span();
             let ser = if field.attrs.flatten() {
                 quote! {
                     try!(_serde::Serialize::serialize(&#field_expr, _serde::private::ser::FlatMapSerializer(&mut __serde_state)));
@@ -963,8 +1116,8 @@ fn wrap_serialize_field_with(
     params: &Parameters,
     field_ty: &syn::Type,
     serialize_with: &syn::ExprPath,
-    field_expr: &Tokens,
-) -> Tokens {
+    field_expr: &TokenStream,
+) -> TokenStream {
     wrap_serialize_with(params, serialize_with, &[field_ty], &[quote!(#field_expr)])
 }
 
@@ -972,16 +1125,18 @@ fn wrap_serialize_variant_with(
     params: &Parameters,
     serialize_with: &syn::ExprPath,
     variant: &Variant,
-) -> Tokens {
+) -> TokenStream {
     let field_tys: Vec<_> = variant.fields.iter().map(|field| field.ty).collect();
     let field_exprs: Vec<_> = variant
         .fields
         .iter()
-        .enumerate()
-        .map(|(i, field)| {
-            let id = field
-                .ident
-                .unwrap_or_else(|| Ident::new(&format!("__field{}", i), Span::def_site()));
+        .map(|field| {
+            let id = match field.member {
+                Member::Named(ref ident) => ident.clone(),
+                Member::Unnamed(ref member) => {
+                    Ident::new(&format!("__field{}", member.index), Span::call_site())
+                }
+            };
             quote!(#id)
         })
         .collect();
@@ -997,8 +1152,8 @@ fn wrap_serialize_with(
     params: &Parameters,
     serialize_with: &syn::ExprPath,
     field_tys: &[&syn::Type],
-    field_exprs: &[Tokens],
-) -> Tokens {
+    field_exprs: &[TokenStream],
+) -> TokenStream {
     let this = &params.this;
     let (_, ty_generics, where_clause) = params.generics.split_for_impl();
 
@@ -1009,10 +1164,12 @@ fn wrap_serialize_with(
     };
     let (wrapper_impl_generics, wrapper_ty_generics, _) = wrapper_generics.split_for_impl();
 
-    let field_access = (0..field_exprs.len()).map(|n| Member::Unnamed(Index {
-        index: n as u32,
-        span: Span::call_site(),
-    }));
+    let field_access = (0..field_exprs.len()).map(|n| {
+        Member::Unnamed(Index {
+            index: n as u32,
+            span: Span::call_site(),
+        })
+    });
 
     quote!({
         struct __SerializeWith #wrapper_impl_generics #where_clause {
@@ -1022,7 +1179,8 @@ fn wrap_serialize_with(
 
         impl #wrapper_impl_generics _serde::Serialize for __SerializeWith #wrapper_ty_generics #where_clause {
             fn serialize<__S>(&self, __s: __S) -> _serde::export::Result<__S::Ok, __S::Error>
-                where __S: _serde::Serializer
+            where
+                __S: _serde::Serializer,
             {
                 #serialize_with(#(self.values.#field_access, )* __s)
             }
@@ -1041,7 +1199,7 @@ fn wrap_serialize_with(
 //     _serde::ser::SerializeStruct::end(__serde_state)
 //
 // where we want to omit the `mut` to avoid a warning.
-fn mut_if(is_mut: bool) -> Option<Tokens> {
+fn mut_if(is_mut: bool) -> Option<TokenStream> {
     if is_mut {
         Some(quote!(mut))
     } else {
@@ -1049,14 +1207,12 @@ fn mut_if(is_mut: bool) -> Option<Tokens> {
     }
 }
 
-fn get_member(params: &Parameters, field: &Field, member: &Member) -> Tokens {
+fn get_member(params: &Parameters, field: &Field, member: &Member) -> TokenStream {
     let self_var = &params.self_var;
     match (params.is_remote, field.attrs.getter()) {
-        (false, None) => {
-            quote_spanned!(Span::call_site()=> &#self_var.#member)
-        }
+        (false, None) => quote!(&#self_var.#member),
         (true, None) => {
-            let inner = quote_spanned!(Span::call_site()=> &#self_var.#member);
+            let inner = quote!(&#self_var.#member);
             let ty = field.ty;
             quote!(_serde::private::ser::constrain::<#ty>(#inner))
         }
@@ -1077,7 +1233,7 @@ enum StructTrait {
 }
 
 impl StructTrait {
-    fn serialize_field(&self, span: Span) -> Tokens {
+    fn serialize_field(&self, span: Span) -> TokenStream {
         match *self {
             StructTrait::SerializeMap => {
                 quote_spanned!(span=> _serde::ser::SerializeMap::serialize_entry)
@@ -1091,15 +1247,15 @@ impl StructTrait {
         }
     }
 
-    fn skip_field(&self, span: Span) -> Option<Tokens> {
+    fn skip_field(&self, span: Span) -> Option<TokenStream> {
         match *self {
             StructTrait::SerializeMap => None,
-            StructTrait::SerializeStruct => Some({
-                quote_spanned!(span=> _serde::ser::SerializeStruct::skip_field)
-            }),
-            StructTrait::SerializeStructVariant => Some({
-                quote_spanned!(span=> _serde::ser::SerializeStructVariant::skip_field)
-            })
+            StructTrait::SerializeStruct => {
+                Some(quote_spanned!(span=> _serde::ser::SerializeStruct::skip_field))
+            }
+            StructTrait::SerializeStructVariant => {
+                Some(quote_spanned!(span=> _serde::ser::SerializeStructVariant::skip_field))
+            }
         }
     }
 }
@@ -1111,7 +1267,7 @@ enum TupleTrait {
 }
 
 impl TupleTrait {
-    fn serialize_element(&self, span: Span) -> Tokens {
+    fn serialize_element(&self, span: Span) -> TokenStream {
         match *self {
             TupleTrait::SerializeTuple => {
                 quote_spanned!(span=> _serde::ser::SerializeTuple::serialize_element)

serde_derive/src/try.rs

@@ -0,0 +1,24 @@
+use proc_macro2::{Punct, Spacing, TokenStream};
+
+// None of our generated code requires the `From::from` error conversion
+// performed by the standard library's `try!` macro. With this simplified macro
+// we see a significant improvement in type checking and borrow checking time of
+// the generated code and a slight improvement in binary size.
+pub fn replacement() -> TokenStream {
+    // Cannot pass `$expr` to `quote!` prior to Rust 1.17.0 so interpolate it.
+    let dollar = Punct::new('$', Spacing::Alone);
+
+    quote! {
+        #[allow(unused_macros)]
+        macro_rules! try {
+            (#dollar __expr:expr) => {
+                match #dollar __expr {
+                    _serde::export::Ok(__val) => __val,
+                    _serde::export::Err(__err) => {
+                        return _serde::export::Err(__err);
+                    }
+                }
+            }
+        }
+    }
+}

serde_derive_internals/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive_internals"
-version = "0.22.0" # remember to update html_root_url
+version = "0.23.1" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "AST representation used by Serde derive macros. Unstable."
@@ -8,12 +8,15 @@ homepage = "https://serde.rs"
 repository = "https://github.com/serde-rs/serde"
 documentation = "https://docs.serde.rs/serde_derive_internals/"
 keywords = ["serde", "serialization"]
-readme = "README.md"
-include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
+readme = "crates-io.md"
+include = ["Cargo.toml", "lib.rs", "src/**/*.rs", "crates-io.md", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
+
+[lib]
+path = "lib.rs"
 
 [dependencies]
-proc-macro2 = "0.2"
-syn = { version = "0.12", default-features = false, features = ["derive", "parsing", "clone-impls"] }
+proc-macro2 = "0.4"
+syn = { version = "0.14", default-features = false, features = ["derive", "parsing", "clone-impls"] }
 
 [badges]
 travis-ci = { repository = "serde-rs/serde" }

serde_derive_internals/crates-io.md

@@ -0,0 +1 @@
+../crates-io.md

serde_derive_internals/lib.rs

@@ -6,20 +6,18 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.22.0")]
-#![cfg_attr(feature = "cargo-clippy", allow(cyclomatic_complexity, doc_markdown, match_same_arms,
-                                            redundant_field_names))]
+#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.23.1")]
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(cyclomatic_complexity, doc_markdown, match_same_arms, redundant_field_names)
+)]
 
 #[macro_use]
 extern crate syn;
 
 extern crate proc_macro2;
 
-pub mod ast;
-pub mod attr;
+#[path = "src/mod.rs"]
+mod internals;
 
-mod ctxt;
-pub use ctxt::Ctxt;
-
-mod case;
-mod check;
+pub use internals::*;

serde_derive_internals/src

@@ -0,0 +1 @@
+../serde_derive/src/internals/

serde_test/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_test"
-version = "1.0.34" # remember to update html_root_url
+version = "1.0.67" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Token De/Serializer for testing De/Serialize implementations"
@@ -8,14 +8,14 @@ homepage = "https://serde.rs"
 repository = "https://github.com/serde-rs/serde"
 documentation = "https://docs.serde.rs/serde_test/"
 keywords = ["serde", "serialization"]
-readme = "README.md"
-include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
+readme = "crates-io.md"
+include = ["Cargo.toml", "src/**/*.rs", "crates-io.md", "README.md", "LICENSE-APACHE", "LICENSE-MIT"]
 
 [dependencies]
-serde = { version = "1.0.16", path = "../serde" }
+serde = { version = "1.0.60", path = "../serde" }
 
 [dev-dependencies]
-serde = { version = "1.0.16", path = "../serde", features = ["rc"] }
+serde = { version = "1.0", path = "../serde", features = ["rc"] }
 serde_derive = { version = "1.0", path = "../serde_derive" }
 
 [badges]

serde_test/crates-io.md

@@ -0,0 +1 @@
+../crates-io.md

serde_test/src/de.rs

@@ -6,9 +6,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use serde::de::{self, Deserialize, DeserializeSeed, EnumAccess, IntoDeserializer, MapAccess,
-                SeqAccess, VariantAccess, Visitor};
 use serde::de::value::{MapAccessDeserializer, SeqAccessDeserializer};
+use serde::de::{
+    self, Deserialize, DeserializeSeed, EnumAccess, IntoDeserializer, MapAccess, SeqAccess,
+    VariantAccess, Visitor,
+};
 
 use error::Error;
 use token::Token;
@@ -22,28 +24,28 @@ macro_rules! assert_next_token {
     ($de:expr, $expected:expr) => {
         match $de.next_token_opt() {
             Some(token) if token == $expected => {}
-            Some(other) => {
-                panic!("expected Token::{} but deserialization wants Token::{}",
-                       other, $expected)
-            }
-            None => {
-                panic!("end of tokens but deserialization wants Token::{}",
-                       $expected)
-            }
+            Some(other) => panic!(
+                "expected Token::{} but deserialization wants Token::{}",
+                other, $expected
+            ),
+            None => panic!(
+                "end of tokens but deserialization wants Token::{}",
+                $expected
+            ),
         }
-    }
+    };
 }
 
 macro_rules! unexpected {
     ($token:expr) => {
         panic!("deserialization did not expect this token: {}", $token)
-    }
+    };
 }
 
 macro_rules! end_of_tokens {
     () => {
         panic!("ran out of tokens to deserialize")
-    }
+    };
 }
 
 impl<'de> Deserializer<'de> {
@@ -127,8 +129,8 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     type Error = Error;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf unit seq map identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf unit seq map identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Error>
@@ -597,7 +599,8 @@ impl<'de, 'a> MapAccess<'de> for EnumMapVisitor<'a, 'de> {
     {
         match self.variant.take() {
             Some(Token::Str(variant)) => seed.deserialize(variant.into_deserializer()).map(Some),
-            Some(Token::Bytes(variant)) => seed.deserialize(BytesDeserializer { value: variant })
+            Some(Token::Bytes(variant)) => seed
+                .deserialize(BytesDeserializer { value: variant })
                 .map(Some),
             Some(Token::U32(variant)) => seed.deserialize(variant.into_deserializer()).map(Some),
             Some(other) => unexpected!(other),
@@ -654,8 +657,8 @@ impl<'de> de::Deserializer<'de> for BytesDeserializer {
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
-        map struct enum identifier ignored_any
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
     }
 }

serde_test/src/lib.rs

@@ -68,11 +68,13 @@
 //! # }
 //! #
 //! # impl<K, V> Serialize for LinkedHashMap<K, V>
-//! #     where K: Serialize,
-//! #           V: Serialize
+//! # where
+//! #     K: Serialize,
+//! #     V: Serialize,
 //! # {
 //! #     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-//! #         where S: Serializer
+//! #     where
+//! #         S: Serializer,
 //! #     {
 //! #         let mut map = serializer.serialize_map(Some(self.0.len()))?;
 //! #         for &(ref k, ref v) in &self.0 {
@@ -85,8 +87,9 @@
 //! # struct LinkedHashMapVisitor<K, V>(PhantomData<(K, V)>);
 //! #
 //! # impl<'de, K, V> Visitor<'de> for LinkedHashMapVisitor<K, V>
-//! #     where K: Deserialize<'de>,
-//! #           V: Deserialize<'de>
+//! # where
+//! #     K: Deserialize<'de>,
+//! #     V: Deserialize<'de>,
 //! # {
 //! #     type Value = LinkedHashMap<K, V>;
 //! #
@@ -95,7 +98,8 @@
 //! #     }
 //! #
 //! #     fn visit_map<M>(self, mut access: M) -> Result<Self::Value, M::Error>
-//! #         where M: MapAccess<'de>
+//! #     where
+//! #         M: MapAccess<'de>,
 //! #     {
 //! #         let mut map = LinkedHashMap::new();
 //! #         while let Some((key, value)) = access.next_entry()? {
@@ -106,11 +110,13 @@
 //! # }
 //! #
 //! # impl<'de, K, V> Deserialize<'de> for LinkedHashMap<K, V>
-//! #     where K: Deserialize<'de>,
-//! #           V: Deserialize<'de>
+//! # where
+//! #     K: Deserialize<'de>,
+//! #     V: Deserialize<'de>,
 //! # {
 //! #     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-//! #         where D: Deserializer<'de>
+//! #     where
+//! #         D: Deserializer<'de>,
 //! #     {
 //! #         deserializer.deserialize_map(LinkedHashMapVisitor(PhantomData))
 //! #     }
@@ -155,29 +161,35 @@
 //! # }
 //! ```
 
-#![doc(html_root_url = "https://docs.rs/serde_test/1.0.34")]
+#![doc(html_root_url = "https://docs.rs/serde_test/1.0.67")]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
 #![cfg_attr(feature = "cargo-clippy", allow(float_cmp))]
 // Whitelisted clippy_pedantic lints
-#![cfg_attr(feature = "cargo-clippy",
-            allow(empty_line_after_outer_attr, missing_docs_in_private_items,
-                  redundant_field_names, stutter, use_debug, use_self))]
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(
+        empty_line_after_outer_attr, missing_docs_in_private_items, redundant_field_names, stutter,
+        use_debug, use_self
+    )
+)]
 
 #[macro_use]
 extern crate serde;
 
-mod ser;
 mod de;
 mod error;
+mod ser;
 
+mod assert;
 mod configure;
 mod token;
-mod assert;
 
+pub use assert::{
+    assert_de_tokens, assert_de_tokens_error, assert_ser_tokens, assert_ser_tokens_error,
+    assert_tokens,
+};
 pub use token::Token;
-pub use assert::{assert_de_tokens, assert_de_tokens_error, assert_ser_tokens,
-                 assert_ser_tokens_error, assert_tokens};
 
 pub use configure::{Compact, Configure, Readable};
 

serde_test/src/ser.rs

@@ -45,7 +45,7 @@ macro_rules! assert_next_token {
     ($ser:expr, $expected:ident($v:expr)) => {
         assert_next_token!(
             $ser,
-            format_args!("{}({:?})", stringify!($expected), $v),
+            format_args!(concat!(stringify!($expected), "({:?})"), $v),
             Token::$expected(v),
             v == $v
         );
@@ -56,13 +56,13 @@ macro_rules! assert_next_token {
             use std::fmt::Write;
             let mut buffer = String::new();
             $(
-                write!(&mut buffer, "{}: {:?}, ", stringify!($k), $k).unwrap();
+                write!(&mut buffer, concat!(stringify!($k), ": {:?}, "), $k).unwrap();
             )*
             buffer
         };
         assert_next_token!(
             $ser,
-            format_args!("{} {{ {}}}", stringify!($expected), field_format()),
+            format_args!(concat!(stringify!($expected), " {{ {}}}"), field_format()),
             Token::$expected { $($k),* },
             ($($k,)*) == compare
         );

test_suite/Cargo.toml

@@ -9,7 +9,7 @@ unstable = ["serde/unstable", "compiletest_rs"]
 
 [dev-dependencies]
 fnv = "1.0"
-proc-macro2 = "0.2"
+proc-macro2 = "0.4"
 rustc-serialize = "0.3.16"
 serde = { path = "../serde", features = ["rc"] }
 serde_derive = { path = "../serde_derive", features = ["deserialize_in_place"] }

test_suite/no_std/src/main.rs

@@ -6,11 +6,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(lang_items, start, compiler_builtins_lib)]
+#![feature(lang_items, start, panic_implementation)]
 #![no_std]
 
 extern crate libc;
-extern crate compiler_builtins;
 
 #[start]
 fn start(_argc: isize, _argv: *const *const u8) -> isize {
@@ -19,19 +18,12 @@ fn start(_argc: isize, _argv: *const *const u8) -> isize {
 
 #[lang = "eh_personality"]
 #[no_mangle]
-pub extern fn rust_eh_personality() {}
+pub extern "C" fn rust_eh_personality() {}
 
-#[lang = "eh_unwind_resume"]
-#[no_mangle]
-pub extern fn rust_eh_unwind_resume() {}
-
-#[lang = "panic_fmt"]
-#[no_mangle]
-pub extern fn rust_begin_panic(_msg: core::fmt::Arguments,
-                               _file: &'static str,
-                               _line: u32) -> ! {
+#[panic_implementation]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
     unsafe {
-        libc::abort()
+        libc::abort();
     }
 }
 
@@ -50,7 +42,9 @@ struct Newtype(u8);
 struct Tuple(u8, u8);
 
 #[derive(Serialize, Deserialize)]
-struct Struct { f: u8 }
+struct Struct {
+    f: u8,
+}
 
 #[derive(Serialize, Deserialize)]
 enum Enum {

test_suite/tests/bytes/mod.rs

@@ -0,0 +1,58 @@
+use serde::de::{Deserializer, Error, SeqAccess, Visitor};
+use std::fmt;
+
+pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<u8>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    deserializer.deserialize_byte_buf(ByteBufVisitor)
+}
+
+struct ByteBufVisitor;
+
+impl<'de> Visitor<'de> for ByteBufVisitor {
+    type Value = Vec<u8>;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("byte array")
+    }
+
+    fn visit_seq<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+    where
+        V: SeqAccess<'de>,
+    {
+        let mut values = Vec::new();
+        while let Some(value) = try!(visitor.next_element()) {
+            values.push(value);
+        }
+        Ok(values)
+    }
+
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(v.to_vec())
+    }
+
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(v)
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(v.as_bytes().to_vec())
+    }
+
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(v.into_bytes())
+    }
+}

test_suite/tests/compile-fail/borrow/bad_lifetimes.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 struct Test<'a> {
-    #[serde(borrow = "zzz")] //~^^ HELP: failed to parse borrowed lifetimes: "zzz"
+    #[serde(borrow = "zzz")]
+    //~^^^ ERROR: failed to parse borrowed lifetimes: "zzz"
     s: &'a str,
 }
 

test_suite/tests/compile-fail/borrow/duplicate_lifetime.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 struct Test<'a> {
-    #[serde(borrow = "'a + 'a")] //~^^ HELP: duplicate borrowed lifetime `'a`
+    #[serde(borrow = "'a + 'a")]
+    //~^^^ ERROR: duplicate borrowed lifetime `'a`
     s: &'a str,
 }
 

test_suite/tests/compile-fail/borrow/duplicate_variant.rs

@@ -12,10 +12,11 @@ extern crate serde_derive;
 #[derive(Deserialize)]
 struct Str<'a>(&'a str);
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 enum Test<'a> {
-    #[serde(borrow)] //~^^ HELP: duplicate serde attribute `borrow`
-    S(#[serde(borrow)] Str<'a>)
+    #[serde(borrow)]
+    //~^^^ ERROR: duplicate serde attribute `borrow`
+    S(#[serde(borrow)] Str<'a>),
 }
 
 fn main() {}

test_suite/tests/compile-fail/borrow/empty_lifetimes.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 struct Test<'a> {
-    #[serde(borrow = "")] //~^^ HELP: at least one lifetime must be borrowed
+    #[serde(borrow = "")]
+    //~^^^ ERROR: at least one lifetime must be borrowed
     s: &'a str,
 }
 

test_suite/tests/compile-fail/borrow/no_lifetimes.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 struct Test {
-    #[serde(borrow)] //~^^ HELP: field `s` has no lifetimes to borrow
+    #[serde(borrow)]
+    //~^^^ ERROR: field `s` has no lifetimes to borrow
     s: String,
 }
 

test_suite/tests/compile-fail/borrow/struct_variant.rs

@@ -12,10 +12,11 @@ extern crate serde_derive;
 #[derive(Deserialize)]
 struct Str<'a>(&'a str);
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 enum Test<'a> {
-    #[serde(borrow)] //~^^ HELP: #[serde(borrow)] may only be used on newtype variants
-    S { s: Str<'a> }
+    #[serde(borrow)]
+    //~^^^ ERROR: #[serde(borrow)] may only be used on newtype variants
+    S { s: Str<'a> },
 }
 
 fn main() {}

test_suite/tests/compile-fail/borrow/wrong_lifetime.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 struct Test<'a> {
-    #[serde(borrow = "'b")] //~^^ HELP: field `s` does not have lifetime 'b
+    #[serde(borrow = "'b")]
+    //~^^^ ERROR: field `s` does not have lifetime 'b
     s: &'a str,
 }
 

test_suite/tests/compile-fail/conflict/adjacent-tag.rs

@@ -9,9 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 #[serde(tag = "conflict", content = "conflict")]
-//~^^ HELP: enum tags `conflict` for type and content conflict with each other
+//~^^ ERROR: enum tags `conflict` for type and content conflict with each other
 enum E {
     A,
     B,

test_suite/tests/compile-fail/conflict/flatten-newtype-struct.rs

@@ -0,0 +1,16 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct Foo(#[serde(flatten)] HashMap<String, String>);
+//~^^ ERROR: #[serde(flatten)] cannot be used on newtype structs
+
+fn main() {}

test_suite/tests/compile-fail/conflict/flatten-skip-deserializing.rs

@@ -9,16 +9,16 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
-//~^ HELP: #[serde(flatten] can not be combined with #[serde(skip_deserializing)]
+#[derive(Deserialize)]
 struct Foo {
     #[serde(flatten, skip_deserializing)]
+    //~^^^ ERROR: #[serde(flatten] can not be combined with #[serde(skip_deserializing)]
     other: Other,
 }
 
 #[derive(Deserialize)]
 struct Other {
-    x: u32
+    x: u32,
 }
 
 fn main() {}

test_suite/tests/compile-fail/conflict/flatten-skip-serializing-if.rs

@@ -9,16 +9,16 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-//~^ HELP: #[serde(flatten] can not be combined with #[serde(skip_serializing_if = "...")]
+#[derive(Serialize)]
 struct Foo {
-    #[serde(flatten, skip_serializing_if="Option::is_none")]
+    #[serde(flatten, skip_serializing_if = "Option::is_none")]
+    //~^^^ ERROR: #[serde(flatten] can not be combined with #[serde(skip_serializing_if = "...")]
     other: Option<Other>,
 }
 
 #[derive(Serialize)]
 struct Other {
-    x: u32
+    x: u32,
 }
 
 fn main() {}

test_suite/tests/compile-fail/conflict/flatten-skip-serializing.rs

@@ -9,16 +9,16 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-//~^ HELP: #[serde(flatten] can not be combined with #[serde(skip_serializing)]
+#[derive(Serialize)]
 struct Foo {
     #[serde(flatten, skip_serializing)]
+    //~^^^ ERROR: #[serde(flatten] can not be combined with #[serde(skip_serializing)]
     other: Other,
 }
 
 #[derive(Serialize)]
 struct Other {
-    x: u32
+    x: u32,
 }
 
 fn main() {}

test_suite/tests/compile-fail/conflict/flatten-tuple-struct.rs

@@ -0,0 +1,16 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct Foo(u32, #[serde(flatten)] HashMap<String, String>);
+//~^^ ERROR: #[serde(flatten)] cannot be used on tuple structs
+
+fn main() {}

test_suite/tests/compile-fail/conflict/internal-tag.rs

@@ -9,9 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 #[serde(tag = "conflict")]
-//~^^ HELP: variant field name `conflict` conflicts with internal tag
+//~^^ ERROR: variant field name `conflict` conflicts with internal tag
 enum E {
     A {
         #[serde(rename = "conflict")]

test_suite/tests/compile-fail/default-attribute/enum.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
-#[serde(default)] //~^ HELP: #[serde(default)] can only be used on structs
+#[derive(Deserialize)]
+#[serde(default)]
+//~^^ ERROR: #[serde(default)] can only be used on structs
 enum E {
     S { f: u8 },
 }

test_suite/tests/compile-fail/default-attribute/nameless_struct_fields.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
-#[serde(default)] //~^ HELP: #[serde(default)] can only be used on structs
+#[derive(Deserialize)]
+#[serde(default)]
+//~^^ ERROR: #[serde(default)] can only be used on structs
 struct T(u8, u8);
 
-fn main() { }
+fn main() {}

test_suite/tests/compile-fail/duplicate-attribute/rename-and-ser.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(rename="x", serialize="y")] //~^^ HELP: unknown serde field attribute `serialize`
+    #[serde(rename = "x", serialize = "y")]
+    //~^^^ ERROR: unknown serde field attribute `serialize`
     x: (),
 }
 

test_suite/tests/compile-fail/duplicate-attribute/rename-rename-de.rs

@@ -9,10 +9,11 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(rename="x")]
-    #[serde(rename(deserialize="y"))] //~^^^ HELP: duplicate serde attribute `rename`
+    #[serde(rename = "x")]
+    #[serde(rename(deserialize = "y"))]
+    //~^^^^ ERROR: duplicate serde attribute `rename`
     x: (),
 }
 

test_suite/tests/compile-fail/duplicate-attribute/rename-ser-rename-ser.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(rename(serialize="x"), rename(serialize="y"))] //~^^ HELP: duplicate serde attribute `rename`
+    #[serde(rename(serialize = "x"), rename(serialize = "y"))]
+    //~^^^ ERROR: duplicate serde attribute `rename`
     x: (),
 }
 

test_suite/tests/compile-fail/duplicate-attribute/rename-ser-rename.rs

@@ -9,10 +9,11 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(rename(serialize="x"))]
-    #[serde(rename="y")] //~^^^ HELP: duplicate serde attribute `rename`
+    #[serde(rename(serialize = "x"))]
+    #[serde(rename = "y")]
+    //~^^^^ ERROR: duplicate serde attribute `rename`
     x: (),
 }
 

test_suite/tests/compile-fail/duplicate-attribute/rename-ser-ser.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(rename(serialize="x", serialize="y"))] //~^^ HELP: duplicate serde attribute `rename`
+    #[serde(rename(serialize = "x", serialize = "y"))]
+    //~^^^ ERROR: duplicate serde attribute `rename`
     x: (),
 }
 

test_suite/tests/compile-fail/duplicate-attribute/two-rename-ser.rs

@@ -9,10 +9,11 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(rename(serialize="x"))]
-    #[serde(rename(serialize="y"))] //~^^^ HELP: duplicate serde attribute `rename`
+    #[serde(rename(serialize = "x"))]
+    #[serde(rename(serialize = "y"))]
+    //~^^^^ ERROR: duplicate serde attribute `rename`
     x: (),
 }
 

test_suite/tests/compile-fail/duplicate-attribute/with-and-serialize-with.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(with = "w", serialize_with = "s")] //~^^ HELP: duplicate serde attribute `serialize_with`
+    #[serde(with = "w", serialize_with = "s")]
+    //~^^^ ERROR: duplicate serde attribute `serialize_with`
     x: (),
 }
 

test_suite/tests/compile-fail/enum-representation/internal-tuple-variant.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-#[serde(tag = "type")] //~^ HELP: #[serde(tag = "...")] cannot be used with tuple variants
+#[derive(Serialize)]
+#[serde(tag = "type")]
+//~^^ ERROR: #[serde(tag = "...")] cannot be used with tuple variants
 enum E {
     Tuple(u8, u8),
 }

test_suite/tests/compile-fail/enum-representation/internally-tagged-struct.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-#[serde(tag = "type")] //~^ HELP: #[serde(tag = "...")] can only be used on enums
+#[derive(Serialize)]
+#[serde(tag = "type")]
+//~^^ ERROR: #[serde(tag = "...")] can only be used on enums
 struct S;
 
 fn main() {}

test_suite/tests/compile-fail/enum-representation/untagged-and-internal.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 #[serde(untagged)]
-#[serde(tag = "type")] //~^^ HELP: enum cannot be both untagged and internally tagged
+#[serde(tag = "type")]
+//~^^^ ERROR: enum cannot be both untagged and internally tagged
 enum E {
     A(u8),
     B(String),

test_suite/tests/compile-fail/enum-representation/untagged-struct.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-#[serde(untagged)] //~^ HELP: #[serde(untagged)] can only be used on enums
+#[derive(Serialize)]
+#[serde(untagged)]
+//~^^ ERROR: #[serde(untagged)] can only be used on enums
 struct S;
 
 fn main() {}

test_suite/tests/compile-fail/identifier/both.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
-#[serde(field_identifier, variant_identifier)] //~^ HELP: `field_identifier` and `variant_identifier` cannot both be set
+#[derive(Deserialize)]
+#[serde(field_identifier, variant_identifier)]
+//~^^ ERROR: `field_identifier` and `variant_identifier` cannot both be set
 enum F {
     A,
     B,

test_suite/tests/compile-fail/identifier/field_struct.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 #[serde(field_identifier)]
-struct S; //~^^ HELP: `field_identifier` can only be used on an enum
+//~^^ ERROR: `field_identifier` can only be used on an enum
+struct S;
 
 fn main() {}

test_suite/tests/compile-fail/identifier/field_tuple.rs

@@ -9,11 +9,12 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 #[serde(field_identifier)]
 enum F {
     A,
-    B(u8, u8), //~^^^^ HELP: field_identifier may only contain unit variants
+    B(u8, u8),
+    //~^^^^^ ERROR: field_identifier may only contain unit variants
 }
 
 fn main() {}

test_suite/tests/compile-fail/identifier/newtype_not_last.rs

@@ -9,11 +9,12 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 #[serde(field_identifier)]
 enum F {
     A,
-    Other(String), //~^^^^ HELP: `Other` must be the last variant
+    Other(String),
+    //~^^^^^ ERROR: `Other` must be the last variant
     B,
 }
 

test_suite/tests/compile-fail/identifier/not_identifier.rs

@@ -9,10 +9,11 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 enum F {
     A,
-    #[serde(other)] //~^^^ HELP: #[serde(other)] may only be used inside a field_identifier
+    #[serde(other)]
+    //~^^^^ ERROR: #[serde(other)] may only be used inside a field_identifier
     B,
 }
 

test_suite/tests/compile-fail/identifier/not_unit.rs

@@ -9,11 +9,12 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 #[serde(field_identifier)]
 enum F {
     A,
-    #[serde(other)] //~^^^^ HELP: #[serde(other)] must be on a unit variant
+    #[serde(other)]
+    //~^^^^^ ERROR: #[serde(other)] must be on a unit variant
     Other(u8, u8),
 }
 

test_suite/tests/compile-fail/identifier/other_not_last.rs

@@ -9,11 +9,12 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 #[serde(field_identifier)]
 enum F {
     A,
-    #[serde(other)] //~^^^^ HELP: #[serde(other)] must be the last variant
+    #[serde(other)]
+    //~^^^^^ ERROR: #[serde(other)] must be the last variant
     Other,
     B,
 }

test_suite/tests/compile-fail/identifier/serialize.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-#[serde(field_identifier)] //~^ HELP: field identifiers cannot be serialized
+#[derive(Serialize)]
+#[serde(field_identifier)]
+//~^^ ERROR: field identifiers cannot be serialized
 enum F {
     A,
     B,

test_suite/tests/compile-fail/identifier/variant_struct.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 #[serde(variant_identifier)]
-struct S; //~^^ HELP: `variant_identifier` can only be used on an enum
+//~^^ ERROR: `variant_identifier` can only be used on an enum
+struct S;
 
 fn main() {}

test_suite/tests/compile-fail/identifier/variant_tuple.rs

@@ -9,11 +9,12 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Deserialize)]
 #[serde(variant_identifier)]
 enum F {
     A,
-    B(u8, u8), //~^^^^ HELP: variant_identifier may only contain unit variants
+    B(u8, u8),
+    //~^^^^^ ERROR: variant_identifier may only contain unit variants
 }
 
 fn main() {}

test_suite/tests/compile-fail/precondition/deserialize_de_lifetime.rs

@@ -0,0 +1,16 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+struct S<'de> {
+    //~^^ ERROR: cannot deserialize when there is a lifetime parameter called 'de
+    s: &'de str,
+}

test_suite/tests/compile-fail/precondition/deserialize_dst.rs

@@ -0,0 +1,17 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+struct S {
+    string: String,
+    slice: [u8],
+    //~^^^^ ERROR: cannot deserialize a dynamically sized struct
+}

test_suite/tests/compile-fail/remote/bad_getter.rs

@@ -15,10 +15,11 @@ mod remote {
     }
 }
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 #[serde(remote = "remote::S")]
 struct S {
-    #[serde(getter = "~~~")] //~^^^ HELP: failed to parse path: "~~~"
+    #[serde(getter = "~~~")]
+    //~^^^^ ERROR: failed to parse path: "~~~"
     a: u8,
 }
 

test_suite/tests/compile-fail/remote/bad_remote.rs

@@ -15,8 +15,9 @@ mod remote {
     }
 }
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-#[serde(remote = "~~~")] //~^ HELP: failed to parse path: "~~~"
+#[derive(Serialize)]
+#[serde(remote = "~~~")]
+//~^^ ERROR: failed to parse path: "~~~"
 struct S {
     a: u8,
 }

test_suite/tests/compile-fail/remote/enum_getter.rs

@@ -11,17 +11,18 @@ extern crate serde_derive;
 
 mod remote {
     pub enum E {
-        A { a: u8 }
+        A { a: u8 },
     }
 }
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 #[serde(remote = "remote::E")]
 pub enum E {
     A {
-        #[serde(getter = "get_a")] //~^^^^ HELP: #[serde(getter = "...")] is not allowed in an enum
+        #[serde(getter = "get_a")]
+        //~^^^^^ ERROR: #[serde(getter = "...")] is not allowed in an enum
         a: u8,
-    }
+    },
 }
 
 fn main() {}

test_suite/tests/compile-fail/remote/missing_field.rs

@@ -19,7 +19,8 @@ mod remote {
 #[derive(Serialize, Deserialize)]
 #[serde(remote = "remote::S")]
 struct S {
-    a: u8, //~^^^ ERROR: missing field `b` in initializer of `remote::S`
+    a: u8,
+    //~^^^^ ERROR: missing field `b` in initializer of `remote::S`
 }
 
 fn main() {}

test_suite/tests/compile-fail/remote/nonremote_getter.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[derive(Serialize)]
 struct S {
-    #[serde(getter = "S::get")] //~^^ HELP: #[serde(getter = "...")] can only be used in structs that have #[serde(remote = "...")]
+    #[serde(getter = "S::get")]
+    //~^^^ ERROR: #[serde(getter = "...")] can only be used in structs that have #[serde(remote = "...")]
     a: u8,
 }
 

test_suite/tests/compile-fail/remote/unknown_field.rs

@@ -19,7 +19,8 @@ mod remote {
 #[serde(remote = "remote::S")]
 struct S {
     //~^^^ ERROR: struct `remote::S` has no field named `b`
-    b: u8, //~^^^^ ERROR: no field `b` on type `&remote::S`
+    b: u8,
+    //~^^^^^ ERROR: no field `b` on type `&remote::S`
 }
 
 fn main() {}