Release 1.0.62

Implement Copy for value deserializers of primitive types

.github/ISSUE_TEMPLATE/2-suggestion.md

@@ -1,5 +1,5 @@
 ---
-name: Feature request
+name: Suggestion
 about: Share how Serde could support your use case better
 
 ---

.github/ISSUE_TEMPLATE/5-other.md

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

serde/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde"
-version = "1.0.46" # remember to update html_root_url
+version = "1.0.62" # 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"
@@ -10,7 +10,8 @@ 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"]
+include = ["Cargo.toml", "build.rs", "src/**/*.rs", "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 +1,67 @@
+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");
+    }
+
+    // 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,
+    };
+
+    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/src/de/from_primitive.rs

@@ -39,12 +39,10 @@ macro_rules! uint_to {
 }
 
 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>;
@@ -54,10 +52,6 @@ pub trait FromPrimitive: Sized {
 macro_rules! impl_from_primitive_for_int {
     ($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!($t, n)
@@ -75,10 +69,6 @@ macro_rules! impl_from_primitive_for_int {
                 int_to_int!($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)
             }
@@ -101,10 +91,6 @@ macro_rules! impl_from_primitive_for_int {
 macro_rules! impl_from_primitive_for_uint {
     ($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!($t, n)
@@ -122,10 +108,6 @@ macro_rules! impl_from_primitive_for_uint {
                 int_to_uint!($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)
             }
@@ -148,10 +130,6 @@ macro_rules! impl_from_primitive_for_uint {
 macro_rules! impl_from_primitive_for_float {
     ($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)
@@ -169,10 +147,6 @@ macro_rules! impl_from_primitive_for_float {
                 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)
             }
@@ -204,3 +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/impls.rs

@@ -32,7 +32,7 @@ impl<'de> Visitor<'de> for UnitVisitor {
         formatter.write_str("unit")
     }
 
-    fn visit_unit<E>(self) -> Result<(), E>
+    fn visit_unit<E>(self) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -41,7 +41,7 @@ impl<'de> Visitor<'de> for UnitVisitor {
 }
 
 impl<'de> Deserialize<'de> for () {
-    fn deserialize<D>(deserializer: D) -> Result<(), D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -60,7 +60,7 @@ impl<'de> Visitor<'de> for BoolVisitor {
         formatter.write_str("a boolean")
     }
 
-    fn visit_bool<E>(self, v: bool) -> Result<bool, E>
+    fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -69,7 +69,7 @@ impl<'de> Visitor<'de> for BoolVisitor {
 }
 
 impl<'de> Deserialize<'de> for bool {
-    fn deserialize<D>(deserializer: D) -> Result<bool, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -110,7 +110,7 @@ macro_rules! impl_deserialize_num {
     ($ty:ident, $method:ident, $($visit:ident),*) => {
         impl<'de> Deserialize<'de> for $ty {
             #[inline]
-            fn deserialize<D>(deserializer: D) -> Result<$ty, D::Error>
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
             where
                 D: Deserializer<'de>,
             {
@@ -166,6 +166,92 @@ impl_deserialize_num!(usize, deserialize_u64, integer);
 impl_deserialize_num!(f32, deserialize_f32, integer, float);
 impl_deserialize_num!(f64, deserialize_f64, integer, float);
 
+serde_if_integer128! {
+    impl<'de> Deserialize<'de> for i128 {
+        #[inline]
+        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            struct PrimitiveVisitor;
+
+            impl<'de> Visitor<'de> for PrimitiveVisitor {
+                type Value = i128;
+
+                fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("i128")
+                }
+
+                impl_deserialize_num!(integer i128);
+
+                #[inline]
+                fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    Ok(v)
+                }
+
+                #[inline]
+                fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    if v <= i128::max_value() as u128 {
+                        Ok(v as i128)
+                    } else {
+                        Err(Error::invalid_value(Unexpected::Other("u128"), &self))
+                    }
+                }
+            }
+
+            deserializer.deserialize_i128(PrimitiveVisitor)
+        }
+    }
+
+    impl<'de> Deserialize<'de> for u128 {
+        #[inline]
+        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            struct PrimitiveVisitor;
+
+            impl<'de> Visitor<'de> for PrimitiveVisitor {
+                type Value = u128;
+
+                fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("u128")
+                }
+
+                impl_deserialize_num!(integer u128);
+
+                #[inline]
+                fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    if v >= 0 {
+                        Ok(v as u128)
+                    } else {
+                        Err(Error::invalid_value(Unexpected::Other("i128"), &self))
+                    }
+                }
+
+                #[inline]
+                fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    Ok(v)
+                }
+            }
+
+            deserializer.deserialize_u128(PrimitiveVisitor)
+        }
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 struct CharVisitor;
@@ -178,7 +264,7 @@ impl<'de> Visitor<'de> for CharVisitor {
     }
 
     #[inline]
-    fn visit_char<E>(self, v: char) -> Result<char, E>
+    fn visit_char<E>(self, v: char) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -186,7 +272,7 @@ impl<'de> Visitor<'de> for CharVisitor {
     }
 
     #[inline]
-    fn visit_str<E>(self, v: &str) -> Result<char, E>
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -200,7 +286,7 @@ impl<'de> Visitor<'de> for CharVisitor {
 
 impl<'de> Deserialize<'de> for char {
     #[inline]
-    fn deserialize<D>(deserializer: D) -> Result<char, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -223,21 +309,21 @@ impl<'de> Visitor<'de> for StringVisitor {
         formatter.write_str("a string")
     }
 
-    fn visit_str<E>(self, v: &str) -> Result<String, E>
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
     where
         E: Error,
     {
         Ok(v.to_owned())
     }
 
-    fn visit_string<E>(self, v: String) -> Result<String, E>
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
     where
         E: Error,
     {
         Ok(v)
     }
 
-    fn visit_bytes<E>(self, v: &[u8]) -> Result<String, E>
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -247,7 +333,7 @@ impl<'de> Visitor<'de> for StringVisitor {
         }
     }
 
-    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<String, E>
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -269,7 +355,7 @@ impl<'a, 'de> Visitor<'de> for StringInPlaceVisitor<'a> {
         formatter.write_str("a string")
     }
 
-    fn visit_str<E>(self, v: &str) -> Result<(), E>
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -278,7 +364,7 @@ impl<'a, 'de> Visitor<'de> for StringInPlaceVisitor<'a> {
         Ok(())
     }
 
-    fn visit_string<E>(self, v: String) -> Result<(), E>
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -286,7 +372,7 @@ impl<'a, 'de> Visitor<'de> for StringInPlaceVisitor<'a> {
         Ok(())
     }
 
-    fn visit_bytes<E>(self, v: &[u8]) -> Result<(), E>
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -300,7 +386,7 @@ impl<'a, 'de> Visitor<'de> for StringInPlaceVisitor<'a> {
         }
     }
 
-    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<(), E>
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -319,7 +405,7 @@ impl<'a, 'de> Visitor<'de> for StringInPlaceVisitor<'a> {
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'de> Deserialize<'de> for String {
-    fn deserialize<D>(deserializer: D) -> Result<String, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -417,7 +503,7 @@ impl<'de> Visitor<'de> for CStringVisitor {
         formatter.write_str("byte array")
     }
 
-    fn visit_seq<A>(self, mut seq: A) -> Result<CString, A::Error>
+    fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
     where
         A: SeqAccess<'de>,
     {
@@ -431,28 +517,28 @@ impl<'de> Visitor<'de> for CStringVisitor {
         CString::new(values).map_err(Error::custom)
     }
 
-    fn visit_bytes<E>(self, v: &[u8]) -> Result<CString, E>
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
     where
         E: Error,
     {
         CString::new(v).map_err(Error::custom)
     }
 
-    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<CString, E>
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
     where
         E: Error,
     {
         CString::new(v).map_err(Error::custom)
     }
 
-    fn visit_str<E>(self, v: &str) -> Result<CString, E>
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
     where
         E: Error,
     {
         CString::new(v).map_err(Error::custom)
     }
 
-    fn visit_string<E>(self, v: String) -> Result<CString, E>
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -462,7 +548,7 @@ impl<'de> Visitor<'de> for CStringVisitor {
 
 #[cfg(feature = "std")]
 impl<'de> Deserialize<'de> for CString {
-    fn deserialize<D>(deserializer: D) -> Result<CString, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -487,7 +573,7 @@ macro_rules! forwarded_impl {
     }
 }
 
-#[cfg(all(feature = "std", feature = "unstable"))]
+#[cfg(all(feature = "std", de_boxed_c_str))]
 forwarded_impl!((), Box<CStr>, CString::into_boxed_c_str);
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -507,7 +593,7 @@ where
     }
 
     #[inline]
-    fn visit_unit<E>(self) -> Result<Option<T>, E>
+    fn visit_unit<E>(self) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -515,7 +601,7 @@ where
     }
 
     #[inline]
-    fn visit_none<E>(self) -> Result<Option<T>, E>
+    fn visit_none<E>(self) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -523,19 +609,27 @@ where
     }
 
     #[inline]
-    fn visit_some<D>(self, deserializer: D) -> Result<Option<T>, D::Error>
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
     where
         D: Deserializer<'de>,
     {
         T::deserialize(deserializer).map(Some)
     }
+
+    #[doc(hidden)]
+    fn __private_visit_untagged_option<D>(self, deserializer: D) -> Result<Self::Value, ()>
+    where
+        D: Deserializer<'de>,
+    {
+        Ok(T::deserialize(deserializer).ok())
+    }
 }
 
 impl<'de, T> Deserialize<'de> for Option<T>
 where
     T: Deserialize<'de>,
 {
-    fn deserialize<D>(deserializer: D) -> Result<Option<T>, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -565,7 +659,7 @@ impl<'de, T: ?Sized> Visitor<'de> for PhantomDataVisitor<T> {
     }
 
     #[inline]
-    fn visit_unit<E>(self) -> Result<PhantomData<T>, E>
+    fn visit_unit<E>(self) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -574,7 +668,7 @@ impl<'de, T: ?Sized> Visitor<'de> for PhantomDataVisitor<T> {
 }
 
 impl<'de, T: ?Sized> Deserialize<'de> for PhantomData<T> {
-    fn deserialize<D>(deserializer: D) -> Result<PhantomData<T>, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -659,7 +753,7 @@ macro_rules! seq_impl {
                     }
 
                     #[inline]
-                    fn visit_seq<A>(mut self, mut $access: A) -> Result<(), A::Error>
+                    fn visit_seq<A>(mut self, mut $access: A) -> Result<Self::Value, A::Error>
                     where
                         A: SeqAccess<'de>,
                     {
@@ -771,7 +865,7 @@ impl<'de, T> Visitor<'de> for ArrayVisitor<[T; 0]> {
     }
 
     #[inline]
-    fn visit_seq<A>(self, _: A) -> Result<[T; 0], A::Error>
+    fn visit_seq<A>(self, _: A) -> Result<Self::Value, A::Error>
     where
         A: SeqAccess<'de>,
     {
@@ -781,7 +875,7 @@ impl<'de, T> Visitor<'de> for ArrayVisitor<[T; 0]> {
 
 // Does not require T: Deserialize<'de>.
 impl<'de, T> Deserialize<'de> for [T; 0] {
-    fn deserialize<D>(deserializer: D) -> Result<[T; 0], D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -803,7 +897,7 @@ macro_rules! array_impls {
                 }
 
                 #[inline]
-                fn visit_seq<A>(self, mut seq: A) -> Result<[T; $len], A::Error>
+                fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
                 where
                     A: SeqAccess<'de>,
                 {
@@ -829,7 +923,7 @@ macro_rules! array_impls {
                 }
 
                 #[inline]
-                fn visit_seq<A>(self, mut seq: A) -> Result<(), A::Error>
+                fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
                 where
                     A: SeqAccess<'de>,
                 {
@@ -851,7 +945,7 @@ macro_rules! array_impls {
             where
                 T: Deserialize<'de>,
             {
-                fn deserialize<D>(deserializer: D) -> Result<[T; $len], D::Error>
+                fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
                 where
                     D: Deserializer<'de>,
                 {
@@ -911,7 +1005,7 @@ macro_rules! tuple_impls {
         $(
             impl<'de, $($name: Deserialize<'de>),+> Deserialize<'de> for ($($name,)+) {
                 #[inline]
-                fn deserialize<D>(deserializer: D) -> Result<($($name,)+), D::Error>
+                fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
                 where
                     D: Deserializer<'de>,
                 {
@@ -928,7 +1022,7 @@ macro_rules! tuple_impls {
 
                         #[inline]
                         #[allow(non_snake_case)]
-                        fn visit_seq<A>(self, mut seq: A) -> Result<($($name,)+), A::Error>
+                        fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
                         where
                             A: SeqAccess<'de>,
                         {
@@ -962,7 +1056,7 @@ macro_rules! tuple_impls {
 
                         #[inline]
                         #[allow(non_snake_case)]
-                        fn visit_seq<A>(self, mut seq:                                                                      A) -> Result<(), A::Error>
+                        fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
                         where
                             A: SeqAccess<'de>,
                         {
@@ -1331,14 +1425,14 @@ impl<'de> Visitor<'de> for PathBufVisitor {
         formatter.write_str("path string")
     }
 
-    fn visit_str<E>(self, v: &str) -> Result<PathBuf, E>
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
     where
         E: Error,
     {
         Ok(From::from(v))
     }
 
-    fn visit_string<E>(self, v: String) -> Result<PathBuf, E>
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
     where
         E: Error,
     {
@@ -1348,7 +1442,7 @@ impl<'de> Visitor<'de> for PathBufVisitor {
 
 #[cfg(feature = "std")]
 impl<'de> Deserialize<'de> for PathBuf {
-    fn deserialize<D>(deserializer: D) -> Result<PathBuf, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -1381,7 +1475,7 @@ impl<'de> Visitor<'de> for OsStringVisitor {
     }
 
     #[cfg(unix)]
-    fn visit_enum<A>(self, data: A) -> Result<OsString, A::Error>
+    fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
     where
         A: EnumAccess<'de>,
     {
@@ -1396,14 +1490,15 @@ impl<'de> Visitor<'de> for OsStringVisitor {
     }
 
     #[cfg(windows)]
-    fn visit_enum<A>(self, data: A) -> Result<OsString, A::Error>
+    fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
     where
         A: EnumAccess<'de>,
     {
         use std::os::windows::ffi::OsStringExt;
 
         match try!(data.variant()) {
-            (OsStringKind::Windows, v) => v.newtype_variant::<Vec<u16>>()
+            (OsStringKind::Windows, v) => v
+                .newtype_variant::<Vec<u16>>()
                 .map(|vec| OsString::from_wide(&vec)),
             (OsStringKind::Unix, _) => Err(Error::custom(
                 "cannot deserialize Unix OS string on Windows",
@@ -1414,7 +1509,7 @@ impl<'de> Visitor<'de> for OsStringVisitor {
 
 #[cfg(all(feature = "std", any(unix, windows)))]
 impl<'de> Deserialize<'de> for OsString {
-    fn deserialize<D>(deserializer: D) -> Result<OsString, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -1433,7 +1528,7 @@ forwarded_impl!((T), Box<[T]>, Vec::into_boxed_slice);
 #[cfg(any(feature = "std", feature = "alloc"))]
 forwarded_impl!((), Box<str>, String::into_boxed_str);
 
-#[cfg(all(not(feature = "unstable"), feature = "rc", any(feature = "std", feature = "alloc")))]
+#[cfg(all(not(de_rc_dst), feature = "rc", any(feature = "std", feature = "alloc")))]
 forwarded_impl! {
     /// This impl requires the [`"rc"`] Cargo feature of Serde.
     ///
@@ -1445,7 +1540,7 @@ forwarded_impl! {
     (T), Arc<T>, Arc::new
 }
 
-#[cfg(all(not(feature = "unstable"), feature = "rc", any(feature = "std", feature = "alloc")))]
+#[cfg(all(not(de_rc_dst), feature = "rc", any(feature = "std", feature = "alloc")))]
 forwarded_impl! {
     /// This impl requires the [`"rc"`] Cargo feature of Serde.
     ///
@@ -1464,7 +1559,7 @@ where
     T::Owned: Deserialize<'de>,
 {
     #[inline]
-    fn deserialize<D>(deserializer: D) -> Result<Cow<'a, T>, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -1474,7 +1569,45 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(all(feature = "unstable", feature = "rc", any(feature = "std", feature = "alloc")))]
+/// This impl requires the [`"rc"`] Cargo feature of Serde. The resulting
+/// `Weak<T>` has a reference count of 0 and cannot be upgraded.
+///
+/// [`"rc"`]: https://serde.rs/feature-flags.html#-features-rc
+#[cfg(all(feature = "rc", any(feature = "std", feature = "alloc")))]
+impl<'de, T: ?Sized> Deserialize<'de> for RcWeak<T>
+where
+    T: Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        try!(Option::<T>::deserialize(deserializer));
+        Ok(RcWeak::new())
+    }
+}
+
+/// This impl requires the [`"rc"`] Cargo feature of Serde. The resulting
+/// `Weak<T>` has a reference count of 0 and cannot be upgraded.
+///
+/// [`"rc"`]: https://serde.rs/feature-flags.html#-features-rc
+#[cfg(all(feature = "rc", any(feature = "std", feature = "alloc")))]
+impl<'de, T: ?Sized> Deserialize<'de> for ArcWeak<T>
+where
+    T: Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        try!(Option::<T>::deserialize(deserializer));
+        Ok(ArcWeak::new())
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+#[cfg(all(de_rc_dst, feature = "rc", any(feature = "std", feature = "alloc")))]
 macro_rules! box_forwarded_impl {
     (
         $(#[doc = $doc:tt])*
@@ -1495,7 +1628,7 @@ macro_rules! box_forwarded_impl {
     };
 }
 
-#[cfg(all(feature = "unstable", feature = "rc", any(feature = "std", feature = "alloc")))]
+#[cfg(all(de_rc_dst, feature = "rc", any(feature = "std", feature = "alloc")))]
 box_forwarded_impl! {
     /// This impl requires the [`"rc"`] Cargo feature of Serde.
     ///
@@ -1507,7 +1640,7 @@ box_forwarded_impl! {
     Rc
 }
 
-#[cfg(all(feature = "unstable", feature = "rc", any(feature = "std", feature = "alloc")))]
+#[cfg(all(de_rc_dst, feature = "rc", any(feature = "std", feature = "alloc")))]
 box_forwarded_impl! {
     /// This impl requires the [`"rc"`] Cargo feature of Serde.
     ///
@@ -1525,7 +1658,7 @@ impl<'de, T> Deserialize<'de> for Cell<T>
 where
     T: Deserialize<'de> + Copy,
 {
-    fn deserialize<D>(deserializer: D) -> Result<Cell<T>, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -1567,7 +1700,7 @@ impl<'de> Deserialize<'de> for Duration {
         };
 
         impl<'de> Deserialize<'de> for Field {
-            fn deserialize<D>(deserializer: D) -> Result<Field, D::Error>
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
             where
                 D: Deserializer<'de>,
             {
@@ -1580,7 +1713,7 @@ impl<'de> Deserialize<'de> for Duration {
                         formatter.write_str("`secs` or `nanos`")
                     }
 
-                    fn visit_str<E>(self, value: &str) -> Result<Field, E>
+                    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -1591,7 +1724,7 @@ impl<'de> Deserialize<'de> for Duration {
                         }
                     }
 
-                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Field, E>
+                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -1619,7 +1752,7 @@ impl<'de> Deserialize<'de> for Duration {
                 formatter.write_str("struct Duration")
             }
 
-            fn visit_seq<A>(self, mut seq: A) -> Result<Duration, A::Error>
+            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
             where
                 A: SeqAccess<'de>,
             {
@@ -1638,7 +1771,7 @@ impl<'de> Deserialize<'de> for Duration {
                 Ok(Duration::new(secs, nanos))
             }
 
-            fn visit_map<A>(self, mut map: A) -> Result<Duration, A::Error>
+            fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
             where
                 A: MapAccess<'de>,
             {
@@ -1692,7 +1825,7 @@ impl<'de> Deserialize<'de> for SystemTime {
         };
 
         impl<'de> Deserialize<'de> for Field {
-            fn deserialize<D>(deserializer: D) -> Result<Field, D::Error>
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
             where
                 D: Deserializer<'de>,
             {
@@ -1705,7 +1838,7 @@ impl<'de> Deserialize<'de> for SystemTime {
                         formatter.write_str("`secs_since_epoch` or `nanos_since_epoch`")
                     }
 
-                    fn visit_str<E>(self, value: &str) -> Result<Field, E>
+                    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -1716,7 +1849,7 @@ impl<'de> Deserialize<'de> for SystemTime {
                         }
                     }
 
-                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Field, E>
+                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -1744,7 +1877,7 @@ impl<'de> Deserialize<'de> for SystemTime {
                 formatter.write_str("struct SystemTime")
             }
 
-            fn visit_seq<A>(self, mut seq: A) -> Result<Duration, A::Error>
+            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
             where
                 A: SeqAccess<'de>,
             {
@@ -1763,7 +1896,7 @@ impl<'de> Deserialize<'de> for SystemTime {
                 Ok(Duration::new(secs, nanos))
             }
 
-            fn visit_map<A>(self, mut map: A) -> Result<Duration, A::Error>
+            fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
             where
                 A: MapAccess<'de>,
             {
@@ -1836,7 +1969,7 @@ where
         };
 
         impl<'de> Deserialize<'de> for Field {
-            fn deserialize<D>(deserializer: D) -> Result<Field, D::Error>
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
             where
                 D: Deserializer<'de>,
             {
@@ -1849,7 +1982,7 @@ where
                         formatter.write_str("`start` or `end`")
                     }
 
-                    fn visit_str<E>(self, value: &str) -> Result<Field, E>
+                    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -1860,7 +1993,7 @@ where
                         }
                     }
 
-                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Field, E>
+                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -1893,7 +2026,7 @@ where
                 formatter.write_str("struct Range")
             }
 
-            fn visit_seq<A>(self, mut seq: A) -> Result<ops::Range<Idx>, A::Error>
+            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
             where
                 A: SeqAccess<'de>,
             {
@@ -1912,7 +2045,7 @@ where
                 Ok(start..end)
             }
 
-            fn visit_map<A>(self, mut map: A) -> Result<ops::Range<Idx>, A::Error>
+            fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
             where
                 A: MapAccess<'de>,
             {
@@ -1959,35 +2092,17 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "unstable")]
-#[allow(deprecated)]
-impl<'de, T> Deserialize<'de> for NonZero<T>
-where
-    T: Deserialize<'de> + Zeroable,
-{
-    fn deserialize<D>(deserializer: D) -> Result<NonZero<T>, D::Error>
-    where
-        D: Deserializer<'de>,
-    {
-        let value = try!(Deserialize::deserialize(deserializer));
-        match NonZero::new(value) {
-            Some(nonzero) => Ok(nonzero),
-            None => Err(Error::custom("expected a non-zero value")),
-        }
-    }
-}
-
 macro_rules! nonzero_integers {
-    ( $( $T: ty, )+ ) => {
+    ( $( $T: ident, )+ ) => {
         $(
-            #[cfg(feature = "unstable")]
-            impl<'de> Deserialize<'de> for $T {
-                fn deserialize<D>(deserializer: D) -> Result<$T, D::Error>
+            #[cfg(num_nonzero)]
+            impl<'de> Deserialize<'de> for num::$T {
+                fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
                 where
                     D: Deserializer<'de>,
                 {
                     let value = try!(Deserialize::deserialize(deserializer));
-                    match <$T>::new(value) {
+                    match <num::$T>::new(value) {
                         Some(nonzero) => Ok(nonzero),
                         None => Err(Error::custom("expected a non-zero value")),
                     }
@@ -2014,7 +2129,7 @@ where
     T: Deserialize<'de>,
     E: Deserialize<'de>,
 {
-    fn deserialize<D>(deserializer: D) -> Result<Result<T, E>, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
@@ -2029,7 +2144,7 @@ where
 
         impl<'de> Deserialize<'de> for Field {
             #[inline]
-            fn deserialize<D>(deserializer: D) -> Result<Field, D::Error>
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
             where
                 D: Deserializer<'de>,
             {
@@ -2042,7 +2157,7 @@ where
                         formatter.write_str("`Ok` or `Err`")
                     }
 
-                    fn visit_u32<E>(self, value: u32) -> Result<Field, E>
+                    fn visit_u32<E>(self, value: u32) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -2056,7 +2171,7 @@ where
                         }
                     }
 
-                    fn visit_str<E>(self, value: &str) -> Result<Field, E>
+                    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -2067,7 +2182,7 @@ where
                         }
                     }
 
-                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Field, E>
+                    fn visit_bytes<E>(self, value: &[u8]) -> Result<Self::Value, E>
                     where
                         E: Error,
                     {
@@ -2101,7 +2216,7 @@ where
                 formatter.write_str("enum Result")
             }
 
-            fn visit_enum<A>(self, data: A) -> Result<Result<T, E>, A::Error>
+            fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
             where
                 A: EnumAccess<'de>,
             {
@@ -2125,7 +2240,7 @@ impl<'de, T> Deserialize<'de> for Wrapping<T>
 where
     T: Deserialize<'de>,
 {
-    fn deserialize<D>(deserializer: D) -> Result<Wrapping<T>, D::Error>
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {

serde/src/de/mod.rs

@@ -52,8 +52,8 @@
 //!
 //!  - **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**:
@@ -84,7 +84,6 @@
 //!    - LinkedList\<T\>
 //!    - VecDeque\<T\>
 //!    - Vec\<T\>
-//!    - EnumSet\<T\> (unstable)
 //!  - **Zero-copy types**:
 //!    - &str
 //!    - &[u8]
@@ -98,8 +97,7 @@
 //!    - Path
 //!    - PathBuf
 //!    - Range\<T\>
-//!    - NonZero\<T\> (unstable, deprecated)
-//!    - num::NonZero* (unstable)
+//!    - num::NonZero*
 //!  - **Net types**:
 //!    - IpAddr
 //!    - Ipv4Addr
@@ -506,6 +504,14 @@ 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.
     ///
@@ -570,6 +576,14 @@ pub trait Deserialize<'de>: Sized {
 ///     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
@@ -620,6 +634,14 @@ 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
@@ -759,7 +781,7 @@ where
 /// 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
+/// 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.
 ///
@@ -769,10 +791,10 @@ 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**
@@ -843,6 +865,14 @@ 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.
+///
+/// # 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
 pub trait Deserializer<'de>: Sized {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -886,6 +916,20 @@ 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
@@ -906,6 +950,20 @@ 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
@@ -1132,24 +1190,22 @@ pub trait Deserializer<'de>: Sized {
     fn is_human_readable(&self) -> bool {
         true
     }
-
-    // Not public API.
-    #[doc(hidden)]
-    fn private_deserialize_internally_tagged_enum<V>(
-        self,
-        visitor: V,
-    ) -> Result<V::Value, Self::Error>
-    where
-        V: Visitor<'de>,
-    {
-        self.deserialize_any(visitor)
-    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 /// 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;
 /// #
@@ -1264,6 +1320,20 @@ 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`].
@@ -1310,6 +1380,20 @@ 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`].
@@ -1541,6 +1625,15 @@ 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(())
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1549,6 +1642,14 @@ 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
 pub trait SeqAccess<'de> {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -1616,6 +1717,14 @@ 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
 pub trait MapAccess<'de> {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -1793,6 +1902,14 @@ 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
 pub trait EnumAccess<'de>: Sized {
     /// The error type that can be returned if some error occurs during
     /// deserialization.
@@ -1825,6 +1942,14 @@ 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
 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`.
@@ -2028,6 +2153,16 @@ 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

@@ -44,6 +44,22 @@ use ser;
 
 ////////////////////////////////////////////////////////////////////////////////
 
+// 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
+            }
+        }
+    };
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 /// A minimal representation of all possible errors that can occur using the
 /// `IntoDeserializer` trait.
 #[derive(Clone, Debug, PartialEq)]
@@ -124,11 +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,
@@ -136,9 +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>
@@ -162,12 +180,14 @@ 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,
@@ -189,9 +209,9 @@ 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>
@@ -218,13 +238,20 @@ 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,
@@ -246,9 +273,9 @@ 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>
@@ -291,12 +318,14 @@ 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,
@@ -339,9 +368,9 @@ 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
     }
 }
 
@@ -364,12 +393,14 @@ 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> {
@@ -408,9 +439,9 @@ 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
     }
 }
 
@@ -433,12 +464,22 @@ 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
@@ -483,9 +524,9 @@ 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
     }
 }
 
@@ -509,12 +550,22 @@ 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
@@ -562,9 +613,9 @@ 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
     }
 }
 
@@ -588,12 +639,14 @@ 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> {
@@ -618,9 +671,9 @@ 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
     }
 }
 
@@ -688,9 +741,9 @@ 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 +856,9 @@ 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
     }
 }
 
@@ -917,9 +970,9 @@ 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
     }
 }
 
@@ -1059,9 +1112,9 @@ 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>
@@ -1207,9 +1260,9 @@ 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/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

@@ -79,14 +79,14 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.46")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.62")]
 // 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))]
 #![cfg_attr(feature = "alloc", feature(alloc))]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
@@ -130,9 +130,6 @@
 #[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.
@@ -144,7 +141,7 @@ mod lib {
         pub use std::*;
     }
 
-    pub use self::core::{cmp, iter, mem, ops, slice, str};
+    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};
@@ -179,14 +176,14 @@ mod lib {
     pub use std::boxed::Box;
 
     #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
-    pub use alloc::rc::Rc;
+    pub use alloc::rc::{Rc, Weak as RcWeak};
     #[cfg(all(feature = "rc", feature = "std"))]
-    pub use std::rc::Rc;
+    pub use std::rc::{Rc, Weak as RcWeak};
 
     #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
-    pub use alloc::arc::Arc;
+    pub use alloc::arc::{Arc, Weak as ArcWeak};
     #[cfg(all(feature = "rc", feature = "std"))]
-    pub use std::sync::Arc;
+    pub use std::sync::{Arc, Weak as ArcWeak};
 
     #[cfg(all(feature = "alloc", not(feature = "std")))]
     pub use alloc::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
@@ -212,13 +209,6 @@ mod lib {
     pub use std::sync::{Mutex, RwLock};
     #[cfg(feature = "std")]
     pub use std::time::{Duration, SystemTime, UNIX_EPOCH};
-
-    #[cfg(feature = "unstable")]
-    #[allow(deprecated)]
-    pub use core::nonzero::{NonZero, Zeroable};
-
-    #[cfg(feature = "unstable")]
-    pub use core::num::{NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize};
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -226,6 +216,9 @@ mod lib {
 #[macro_use]
 mod macros;
 
+#[macro_use]
+mod integer128;
+
 pub mod de;
 pub mod ser;
 

serde/src/macros.rs

@@ -46,8 +46,8 @@
 /// }
 /// #
 /// #     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
 /// #     }
 /// # }
@@ -80,8 +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
 ///     }
 /// }
@@ -116,9 +116,9 @@
 /// #
 /// 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
 /// }
 /// # }
 /// #
@@ -174,6 +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, $v>()}
     };
@@ -186,6 +191,11 @@ macro_rules! forward_to_deserialize_any_helper {
     (u64<$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/de.rs

@@ -50,9 +50,9 @@ where
         }
 
         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
         }
     }
 
@@ -276,6 +276,8 @@ mod content {
             match *self {
                 Content::Str(x) => Some(x),
                 Content::String(ref x) => Some(x),
+                Content::Bytes(x) => str::from_utf8(x).ok(),
+                Content::ByteBuf(ref x) => str::from_utf8(x).ok(),
                 _ => None,
             }
         }
@@ -1423,6 +1425,8 @@ mod content {
             match self.content {
                 Content::String(v) => visitor.visit_string(v),
                 Content::Str(v) => visitor.visit_borrowed_str(v),
+                Content::ByteBuf(v) => visitor.visit_byte_buf(v),
+                Content::Bytes(v) => visitor.visit_borrowed_bytes(v),
                 _ => Err(self.invalid_type(&visitor)),
             }
         }
@@ -1614,8 +1618,8 @@ mod content {
         }
 
         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
         }
     }
@@ -1712,8 +1716,8 @@ mod content {
         }
 
         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
         }
     }
@@ -2123,6 +2127,8 @@ mod content {
             match *self.content {
                 Content::String(ref v) => visitor.visit_str(v),
                 Content::Str(v) => visitor.visit_borrowed_str(v),
+                Content::ByteBuf(ref v) => visitor.visit_bytes(v),
+                Content::Bytes(v) => visitor.visit_borrowed_bytes(v),
                 _ => Err(self.invalid_type(&visitor)),
             }
         }
@@ -2300,8 +2306,8 @@ mod content {
         }
 
         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
         }
     }
@@ -2317,7 +2323,8 @@ mod content {
             T: de::DeserializeSeed<'de>,
         {
             match self.iter.next() {
-                Some(value) => seed.deserialize(ContentRefDeserializer::new(value))
+                Some(value) => seed
+                    .deserialize(ContentRefDeserializer::new(value))
                     .map(Some),
                 None => Ok(None),
             }
@@ -2399,8 +2406,8 @@ mod content {
         }
 
         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
         }
     }
@@ -2571,9 +2578,9 @@ 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
     }
 }
 
@@ -2610,9 +2617,9 @@ 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
     }
 }
 
@@ -2640,6 +2647,30 @@ pub struct FlatMapDeserializer<'a, 'de: 'a, E>(
     pub PhantomData<E>,
 );
 
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'a, 'de, E> FlatMapDeserializer<'a, 'de, E>
+where
+    E: Error,
+{
+    fn deserialize_other<V>() -> Result<V, E> {
+        Err(Error::custom("can only flatten structs and maps"))
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+macro_rules! forward_to_deserialize_other {
+    ($($func:ident ( $($arg:ty),* ))*) => {
+        $(
+            fn $func<V>(self, $(_: $arg,)* _visitor: V) -> Result<V::Value, Self::Error>
+            where
+                V: Visitor<'de>,
+            {
+                Self::deserialize_other()
+            }
+        )*
+    }
+}
+
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, 'de, E> Deserializer<'de> for FlatMapDeserializer<'a, 'de, E>
 where
@@ -2647,11 +2678,15 @@ where
 {
     type Error = E;
 
-    fn deserialize_any<V>(self, _: V) -> Result<V::Value, Self::Error>
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
     where
         V: Visitor<'de>,
     {
-        Err(Error::custom("can only flatten structs and maps"))
+        visitor.visit_map(FlatInternallyTaggedAccess {
+            iter: self.0.iter_mut(),
+            pending: None,
+            _marker: PhantomData,
+        })
     }
 
     fn deserialize_enum<V>(
@@ -2710,24 +2745,40 @@ where
         visitor.visit_newtype_struct(self)
     }
 
-    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 seq tuple tuple_struct identifier
-        ignored_any
-    }
-
-    fn private_deserialize_internally_tagged_enum<V>(
-        self,
-        visitor: V,
-    ) -> Result<V::Value, Self::Error>
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
     where
         V: Visitor<'de>,
     {
-        visitor.visit_map(FlatInternallyTaggedAccess {
-            iter: self.0.iter_mut(),
-            pending: None,
-            _marker: PhantomData,
-        })
+        match visitor.__private_visit_untagged_option(self) {
+            Ok(value) => Ok(value),
+            Err(()) => Self::deserialize_other(),
+        }
+    }
+
+    forward_to_deserialize_other! {
+        deserialize_bool()
+        deserialize_i8()
+        deserialize_i16()
+        deserialize_i32()
+        deserialize_i64()
+        deserialize_u8()
+        deserialize_u16()
+        deserialize_u32()
+        deserialize_u64()
+        deserialize_f32()
+        deserialize_f64()
+        deserialize_char()
+        deserialize_str()
+        deserialize_string()
+        deserialize_bytes()
+        deserialize_byte_buf()
+        deserialize_unit()
+        deserialize_unit_struct(&'static str)
+        deserialize_seq()
+        deserialize_tuple(usize)
+        deserialize_tuple_struct(&'static str, usize)
+        deserialize_identifier()
+        deserialize_ignored_any()
     }
 }
 
@@ -2771,14 +2822,13 @@ where
             // about.  In case we do not know which fields we want, we take them all.
             let use_item = match *item {
                 None => false,
-                Some((ref c, _)) => {
-                    c.as_str()
-                        .map_or(self.fields.is_none(), |key| match self.fields {
-                            None => true,
-                            Some(fields) if fields.contains(&key) => true,
-                            _ => false,
-                        })
-                }
+                Some((ref c, _)) => c.as_str().map_or(self.fields.is_none(), |key| {
+                    match self.fields {
+                        None => true,
+                        Some(fields) if fields.contains(&key) => true,
+                        _ => false,
+                    }
+                }),
             };
 
             if use_item {
@@ -2819,16 +2869,18 @@ where
     where
         T: DeserializeSeed<'de>,
     {
-        while let Some(item) = self.iter.next() {
-            // Do not take(), instead borrow this entry. The internally tagged
-            // enum does its own buffering so we can't tell whether this entry
-            // is going to be consumed. Borrowing here leaves the entry
-            // available for later flattened fields.
-            let (ref key, ref content) = *item.as_ref().unwrap();
-            self.pending = Some(content);
-            return seed.deserialize(ContentRefDeserializer::new(key)).map(Some);
+        match self.iter.next() {
+            Some(item) => {
+                // Do not take(), instead borrow this entry. The internally tagged
+                // enum does its own buffering so we can't tell whether this entry
+                // is going to be consumed. Borrowing here leaves the entry
+                // available for later flattened fields.
+                let (ref key, ref content) = *item.as_ref().unwrap();
+                self.pending = Some(content);
+                seed.deserialize(ContentRefDeserializer::new(key)).map(Some)
+            }
+            None => Ok(None),
         }
-        Ok(None)
     }
 
     fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value, Self::Error>

serde/src/private/ser.rs

@@ -947,7 +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()));
@@ -1122,14 +1123,14 @@ where
     }
 
     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> {

serde/src/ser/impls.rs

@@ -44,6 +44,11 @@ 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 {
@@ -374,25 +379,45 @@ deref_impl!(<'a, T: ?Sized> Serialize for Cow<'a, T> where T: Serialize + ToOwne
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "unstable")]
-#[allow(deprecated)]
-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(feature = "unstable")]
-            impl Serialize for $T {
+            #[cfg(num_nonzero)]
+            impl Serialize for num::$T {
                 fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
                 where
                     S: Serializer,
@@ -515,7 +540,8 @@ 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()));

serde/src/ser/mod.rs

@@ -48,8 +48,8 @@
 //!
 //!  - **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
@@ -81,7 +81,6 @@
 //!    - LinkedList\<T\>
 //!    - VecDeque\<T\>
 //!    - Vec\<T\>
-//!    - EnumSet\<T\> (unstable)
 //!  - **FFI types**:
 //!    - CStr
 //!    - CString
@@ -93,8 +92,7 @@
 //!    - Path
 //!    - PathBuf
 //!    - Range\<T\>
-//!    - NonZero\<T\> (unstable, deprecated)
-//!    - num::NonZero* (unstable)
+//!    - num::NonZero*
 //!  - **Net types**:
 //!    - IpAddr
 //!    - Ipv4Addr
@@ -247,7 +245,7 @@ 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
+/// 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.
 ///
@@ -256,10 +254,10 @@ pub trait Serialize {
 ///
 /// 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**
@@ -494,6 +492,37 @@ 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
@@ -598,6 +627,37 @@ 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

serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.46" # remember to update html_root_url
+version = "1.0.62" # 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)]"
@@ -23,9 +23,9 @@ name = "serde_derive"
 proc-macro = true
 
 [dependencies]
-proc-macro2 = "0.3"
-quote = "0.5.2"
-syn = { version = "0.13", 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/src/bound.rs

@@ -55,7 +55,8 @@ pub fn with_where_predicates_from_fields(
     generics: &syn::Generics,
     from_field: fn(&attr::Field) -> Option<&[syn::WherePredicate]>,
 ) -> syn::Generics {
-    let predicates = cont.data
+    let predicates = cont
+        .data
         .all_fields()
         .flat_map(|field| from_field(&field.attrs))
         .flat_map(|predicates| predicates.to_vec());
@@ -65,6 +66,28 @@ pub fn with_where_predicates_from_fields(
     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
+}
+
 // Puts the given bound on any generic type parameters that are used in fields
 // for which filter returns true.
 //
@@ -117,9 +140,9 @@ pub fn with_bound(
                 }
             }
             if path.leading_colon.is_none() && path.segments.len() == 1 {
-                let id = path.segments[0].ident;
-                if self.all_type_params.contains(&id) {
-                    self.relevant_type_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);
@@ -134,7 +157,10 @@ pub fn with_bound(
         fn visit_macro(&mut self, _mac: &'ast syn::Macro) {}
     }
 
-    let all_type_params = generics.type_params().map(|param| param.ident).collect();
+    let all_type_params = generics
+        .type_params()
+        .map(|param| param.ident.clone())
+        .collect();
 
     let mut visitor = FindTyParams {
         all_type_params: all_type_params,
@@ -162,7 +188,7 @@ pub fn with_bound(
     let associated_type_usage = visitor.associated_type_usage;
     let new_predicates = generics
         .type_params()
-        .map(|param| param.ident)
+        .map(|param| param.ident.clone())
         .filter(|id| relevant_type_params.contains(id))
         .map(|id| syn::TypePath {
             qself: None,
@@ -224,7 +250,7 @@ pub fn with_lifetime_bound(generics: &syn::Generics, lifetime: &str) -> syn::Gen
     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(),
     };
@@ -234,10 +260,12 @@ pub fn with_lifetime_bound(generics: &syn::Generics, lifetime: &str) -> syn::Gen
         .chain(generics.params.iter().cloned().map(|mut param| {
             match param {
                 syn::GenericParam::Lifetime(ref mut param) => {
-                    param.bounds.push(bound);
+                    param.bounds.push(bound.clone());
                 }
                 syn::GenericParam::Type(ref mut param) => {
-                    param.bounds.push(syn::TypeParamBound::Lifetime(bound));
+                    param
+                        .bounds
+                        .push(syn::TypeParamBound::Lifetime(bound.clone()));
                 }
                 syn::GenericParam::Const(_) => {}
             }
@@ -257,23 +285,24 @@ fn type_of_item(cont: &Container) -> syn::Type {
         path: syn::Path {
             leading_colon: None,
             segments: vec![syn::PathSegment {
-                ident: cont.ident,
+                ident: cont.ident.clone(),
                 arguments: syn::PathArguments::AngleBracketed(
                     syn::AngleBracketedGenericArguments {
                         colon2_token: None,
                         lt_token: Default::default(),
-                        args: cont.generics
+                        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(),
+                                        path: param.ident.clone().into(),
                                     }))
                                 }
                                 syn::GenericParam::Lifetime(ref param) => {
-                                    syn::GenericArgument::Lifetime(param.lifetime)
+                                    syn::GenericArgument::Lifetime(param.lifetime.clone())
                                 }
                                 syn::GenericParam::Const(_) => {
                                     panic!("Serde does not support const generics yet");

serde_derive/src/de.rs

@@ -6,8 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use proc_macro2::{Literal, Span};
-use quote::{ToTokens, Tokens};
+use proc_macro2::{Literal, Span, TokenStream};
+use quote::ToTokens;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::{self, Ident, Index, Member};
@@ -15,18 +15,19 @@ use syn::{self, Ident, Index, Member};
 use bound;
 use fragment::{Expr, Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
-use internals::{self, attr};
+use internals::{attr, Ctxt, Derive};
 use pretend;
 use try;
 
 use std::collections::BTreeSet;
 
-pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<Tokens, String> {
-    let ctxt = internals::Ctxt::new();
-    let cont = Container::from_ast(&ctxt, input);
+pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<TokenStream, String> {
+    let ctxt = Ctxt::new();
+    let cont = Container::from_ast(&ctxt, input, Derive::Deserialize);
+    precondition(&ctxt, &cont);
     try!(ctxt.check());
 
-    let ident = cont.ident;
+    let ident = &cont.ident;
     let params = Parameters::new(&cont);
     let (de_impl_generics, _, ty_generics, where_clause) = split_with_de_lifetime(&params);
     let dummy_const = Ident::new(
@@ -80,6 +81,32 @@ pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<Tokens, Str
     Ok(generated)
 }
 
+fn precondition(cx: &Ctxt, cont: &Container) {
+    precondition_sized(cx, cont);
+    precondition_no_de_lifetime(cx, cont);
+}
+
+fn precondition_sized(cx: &Ctxt, cont: &Container) {
+    if let Data::Struct(_, ref fields) = cont.data {
+        if let Some(last) = fields.last() {
+            if let syn::Type::Slice(_) = *last.ty {
+                cx.error("cannot deserialize a dynamically sized struct");
+            }
+        }
+    }
+}
+
+fn precondition_no_de_lifetime(cx: &Ctxt, cont: &Container) {
+    if let BorrowedLifetimes::Borrowed(_) = borrowed_lifetimes(cont) {
+        for param in cont.generics.lifetimes() {
+            if param.lifetime.to_string() == "'de" {
+                cx.error("cannot deserialize when there is a lifetime parameter called 'de");
+                return;
+            }
+        }
+    }
+}
+
 struct Parameters {
     /// Name of the type the `derive` is on.
     local: syn::Ident,
@@ -103,10 +130,10 @@ struct Parameters {
 
 impl Parameters {
     fn new(cont: &Container) -> Self {
-        let local = cont.ident;
+        let local = cont.ident.clone();
         let this = match cont.attrs.remote() {
             Some(remote) => remote.clone(),
-            None => cont.ident.into(),
+            None => cont.ident.clone().into(),
         };
         let borrowed = borrowed_lifetimes(cont);
         let generics = build_generics(cont, &borrowed);
@@ -123,8 +150,8 @@ impl Parameters {
 
     /// Type name to use in error messages and `&'static str` arguments to
     /// various Deserializer 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()
     }
 }
 
@@ -136,6 +163,9 @@ fn build_generics(cont: &Container, borrowed: &BorrowedLifetimes) -> syn::Generi
 
     let generics = bound::with_where_predicates_from_fields(cont, &generics, attr::Field::de_bound);
 
+    let generics =
+        bound::with_where_predicates_from_variants(cont, &generics, attr::Variant::de_bound);
+
     match cont.attrs.de_bound() {
         Some(predicates) => bound::with_where_predicates(&generics, predicates),
         None => {
@@ -164,13 +194,19 @@ fn build_generics(cont: &Container, borrowed: &BorrowedLifetimes) -> syn::Generi
     }
 }
 
-// Fields with a `skip_deserializing` or `deserialize_with` attribute are not
-// deserialized 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: Deserialize` bound where T is the type of the field.
+// Fields with a `skip_deserializing` or `deserialize_with` attribute, or which
+// belong to a variant with a `skip_deserializing` or `deserialize_with`
+// attribute, are not deserialized 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: Deserialize` bound where T is the type of the
+// field.
 fn needs_deserialize_bound(field: &attr::Field, variant: Option<&attr::Variant>) -> bool {
     !field.skip_deserializing() && field.deserialize_with().is_none() && field.de_bound().is_none()
-        && variant.map_or(true, |variant| variant.deserialize_with().is_none())
+        && variant.map_or(true, |variant| {
+            !variant.skip_deserializing()
+                && variant.deserialize_with().is_none()
+                && variant.de_bound().is_none()
+        })
 }
 
 // Fields with a `default` attribute (not `default=...`), and fields with a
@@ -233,21 +269,17 @@ fn borrowed_lifetimes(cont: &Container) -> BorrowedLifetimes {
 }
 
 fn deserialize_body(cont: &Container, params: &Parameters) -> Fragment {
-    if let Some(type_from) = cont.attrs.type_from() {
+    if cont.attrs.transparent() {
+        deserialize_transparent(cont, params)
+    } else if let Some(type_from) = cont.attrs.type_from() {
         deserialize_from(type_from)
     } else if let attr::Identifier::No = cont.attrs.identifier() {
         match cont.data {
             Data::Enum(ref variants) => deserialize_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");
-                }
                 deserialize_struct(None, params, fields, &cont.attrs, None, &Untagged::No)
             }
             Data::Struct(Style::Tuple, ref fields) | Data::Struct(Style::Newtype, ref fields) => {
-                if fields.iter().any(|field| field.ident.is_some()) {
-                    panic!("tuple struct has named fields");
-                }
                 deserialize_tuple(None, params, fields, &cont.attrs, None)
             }
             Data::Struct(Style::Unit, _) => deserialize_unit_struct(params, &cont.attrs),
@@ -268,8 +300,11 @@ fn deserialize_in_place_body(cont: &Container, params: &Parameters) -> Option<St
     // deserialize_in_place for remote derives.
     assert!(!params.has_getter);
 
-    if cont.attrs.type_from().is_some() || cont.attrs.identifier().is_some()
-        || cont.data
+    if cont.attrs.transparent()
+        || cont.attrs.type_from().is_some()
+        || cont.attrs.identifier().is_some()
+        || cont
+            .data
             .all_fields()
             .all(|f| f.attrs.deserialize_with().is_some())
     {
@@ -313,6 +348,41 @@ fn deserialize_in_place_body(_cont: &Container, _params: &Parameters) -> Option<
     None
 }
 
+fn deserialize_transparent(cont: &Container, params: &Parameters) -> Fragment {
+    let fields = match cont.data {
+        Data::Struct(_, ref fields) => fields,
+        Data::Enum(_) => unreachable!(),
+    };
+
+    let this = &params.this;
+    let transparent_field = fields.iter().find(|f| f.attrs.transparent()).unwrap();
+
+    let path = match transparent_field.attrs.deserialize_with() {
+        Some(path) => quote!(#path),
+        None => quote!(_serde::Deserialize::deserialize),
+    };
+
+    let assign = fields.iter().map(|field| {
+        let member = &field.member;
+        if field as *const Field == transparent_field as *const Field {
+            quote!(#member: __transparent)
+        } else {
+            let value = match *field.attrs.default() {
+                attr::Default::Default => quote!(_serde::export::Default::default()),
+                attr::Default::Path(ref path) => quote!(#path()),
+                attr::Default::None => quote!(_serde::export::PhantomData),
+            };
+            quote!(#member: #value)
+        }
+    });
+
+    quote_block! {
+        _serde::export::Result::map(
+            #path(__deserializer),
+            |__transparent| #this { #(#assign),* })
+    }
+}
+
 fn deserialize_from(type_from: &syn::Type) -> Fragment {
     quote_block! {
         _serde::export::Result::map(
@@ -351,11 +421,11 @@ fn deserialize_unit_struct(params: &Parameters, cattrs: &attr::Container) -> Fra
 }
 
 fn deserialize_tuple(
-    variant_ident: Option<syn::Ident>,
+    variant_ident: Option<&syn::Ident>,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
 ) -> Fragment {
     let this = &params.this;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
@@ -368,7 +438,7 @@ fn deserialize_tuple(
     // and use an `Into` conversion to get the remote type. If there are no
     // getters then construct the target type directly.
     let construct = if params.has_getter {
-        let local = params.local;
+        let local = &params.local;
         quote!(#local)
     } else {
         quote!(#this)
@@ -376,7 +446,7 @@ fn deserialize_tuple(
 
     let is_enum = variant_ident.is_some();
     let type_path = match variant_ident {
-        Some(variant_ident) => quote!(#construct::#variant_ident),
+        Some(ref variant_ident) => quote!(#construct::#variant_ident),
         None => construct,
     };
     let expecting = match variant_ident {
@@ -392,7 +462,9 @@ fn deserialize_tuple(
         None
     };
 
-    let visit_seq = Stmts(deserialize_seq(&type_path, params, fields, false, cattrs));
+    let visit_seq = Stmts(deserialize_seq(
+        &type_path, params, fields, false, cattrs, &expecting,
+    ));
 
     let visitor_expr = quote! {
         __Visitor {
@@ -453,7 +525,7 @@ fn deserialize_tuple_in_place(
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
 ) -> Fragment {
     let this = &params.this;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
@@ -476,7 +548,7 @@ fn deserialize_tuple_in_place(
         None
     };
 
-    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs));
+    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, &expecting));
 
     let visitor_expr = quote! {
         __Visitor {
@@ -537,23 +609,26 @@ fn deserialize_tuple_in_place(
 }
 
 fn deserialize_seq(
-    type_path: &Tokens,
+    type_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     is_struct: bool,
     cattrs: &attr::Container,
+    expecting: &str,
 ) -> Fragment {
     let vars = (0..fields.len()).map(field_i as fn(_) -> _);
 
-    // XXX: do we need an error for flattening here?
-
     let deserialized_count = fields
         .iter()
         .filter(|field| !field.attrs.skip_deserializing())
         .count();
-    let expecting = format!("tuple of {} elements", deserialized_count);
+    let expecting = if deserialized_count == 1 {
+        format!("{} with 1 element", expecting)
+    } else {
+        format!("{} with {} elements", expecting, deserialized_count)
+    };
 
-    let mut index_in_seq = 0usize;
+    let mut index_in_seq = 0_usize;
     let let_values = vars.clone().zip(fields).map(|(var, field)| {
         if field.attrs.skip_deserializing() {
             let default = Expr(expr_is_missing(field, cattrs));
@@ -593,7 +668,7 @@ fn deserialize_seq(
     });
 
     let mut result = if is_struct {
-        let names = fields.iter().map(|f| &f.ident);
+        let names = fields.iter().map(|f| &f.member);
         quote! {
             #type_path { #( #names: #vars ),* }
         }
@@ -636,69 +711,60 @@ fn deserialize_seq_in_place(
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
+    expecting: &str,
 ) -> Fragment {
-    let vars = (0..fields.len()).map(field_i as fn(_) -> _);
-
-    // XXX: do we need an error for flattening here?
-
     let deserialized_count = fields
         .iter()
         .filter(|field| !field.attrs.skip_deserializing())
         .count();
-    let expecting = format!("tuple of {} elements", deserialized_count);
+    let expecting = if deserialized_count == 1 {
+        format!("{} with 1 element", expecting)
+    } else {
+        format!("{} with {} elements", expecting, deserialized_count)
+    };
 
     let mut index_in_seq = 0usize;
-    let write_values = vars.clone()
-        .zip(fields)
-        .enumerate()
-        .map(|(field_index, (_, field))| {
-            // If there's no field name, assume we're a tuple-struct and use a numeric index
-            let field_name = field.ident.map(Member::Named).unwrap_or_else(|| {
-                Member::Unnamed(Index {
-                    index: field_index as u32,
-                    span: Span::call_site(),
-                })
-            });
+    let write_values = fields.iter().map(|field| {
+        let member = &field.member;
 
-            if field.attrs.skip_deserializing() {
-                let default = Expr(expr_is_missing(field, cattrs));
-                quote! {
-                    self.place.#field_name = #default;
-                }
-            } else {
-                let return_invalid_length = quote! {
-                    return _serde::export::Err(_serde::de::Error::invalid_length(#index_in_seq, &#expecting));
-                };
-                let write = match field.attrs.deserialize_with() {
-                    None => {
-                        quote! {
-                            if let _serde::export::None = try!(_serde::de::SeqAccess::next_element_seed(&mut __seq,
-                                _serde::private::de::InPlaceSeed(&mut self.place.#field_name)))
-                            {
-                                #return_invalid_length
-                            }
+        if field.attrs.skip_deserializing() {
+            let default = Expr(expr_is_missing(field, cattrs));
+            quote! {
+                self.place.#member = #default;
+            }
+        } else {
+            let return_invalid_length = quote! {
+                return _serde::export::Err(_serde::de::Error::invalid_length(#index_in_seq, &#expecting));
+            };
+            let write = match field.attrs.deserialize_with() {
+                None => {
+                    quote! {
+                        if let _serde::export::None = try!(_serde::de::SeqAccess::next_element_seed(&mut __seq,
+                            _serde::private::de::InPlaceSeed(&mut self.place.#member)))
+                        {
+                            #return_invalid_length
                         }
                     }
-                    Some(path) => {
-                        let (wrapper, wrapper_ty) =
-                            wrap_deserialize_field_with(params, field.ty, path);
-                        quote!({
+                }
+                Some(path) => {
+                    let (wrapper, wrapper_ty) = wrap_deserialize_field_with(params, field.ty, path);
+                    quote!({
                             #wrapper
                             match try!(_serde::de::SeqAccess::next_element::<#wrapper_ty>(&mut __seq)) {
                                 _serde::export::Some(__wrap) => {
-                                    self.place.#field_name = __wrap.value;
+                                    self.place.#member = __wrap.value;
                                 }
                                 _serde::export::None => {
                                     #return_invalid_length
                                 }
                             }
                         })
-                    }
-                };
-                index_in_seq += 1;
-                write
-            }
-        });
+                }
+            };
+            index_in_seq += 1;
+            write
+        }
+    });
 
     let this = &params.this;
     let (_, ty_generics, _) = params.generics.split_for_impl();
@@ -723,7 +789,11 @@ fn deserialize_seq_in_place(
     }
 }
 
-fn deserialize_newtype_struct(type_path: &Tokens, params: &Parameters, field: &Field) -> Tokens {
+fn deserialize_newtype_struct(
+    type_path: &TokenStream,
+    params: &Parameters,
+    field: &Field,
+) -> TokenStream {
     let delife = params.borrowed.de_lifetime();
     let field_ty = field.ty;
 
@@ -761,7 +831,7 @@ fn deserialize_newtype_struct(type_path: &Tokens, params: &Parameters, field: &F
 }
 
 #[cfg(feature = "deserialize_in_place")]
-fn deserialize_newtype_struct_in_place(params: &Parameters, field: &Field) -> Tokens {
+fn deserialize_newtype_struct_in_place(params: &Parameters, field: &Field) -> TokenStream {
     // We do not generate deserialize_in_place if every field has a deserialize_with.
     assert!(field.attrs.deserialize_with().is_none());
 
@@ -784,11 +854,11 @@ enum Untagged {
 }
 
 fn deserialize_struct(
-    variant_ident: Option<syn::Ident>,
+    variant_ident: Option<&syn::Ident>,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
     untagged: &Untagged,
 ) -> Fragment {
     let is_enum = variant_ident.is_some();
@@ -802,14 +872,14 @@ fn deserialize_struct(
     // and use an `Into` conversion to get the remote type. If there are no
     // getters then construct the target type directly.
     let construct = if params.has_getter {
-        let local = params.local;
+        let local = &params.local;
         quote!(#local)
     } else {
         quote!(#this)
     };
 
     let type_path = match variant_ident {
-        Some(variant_ident) => quote!(#construct::#variant_ident),
+        Some(ref variant_ident) => quote!(#construct::#variant_ident),
         None => construct,
     };
     let expecting = match variant_ident {
@@ -817,7 +887,9 @@ fn deserialize_struct(
         None => format!("struct {}", params.type_name()),
     };
 
-    let visit_seq = Stmts(deserialize_seq(&type_path, params, fields, true, cattrs));
+    let visit_seq = Stmts(deserialize_seq(
+        &type_path, params, fields, true, cattrs, &expecting,
+    ));
 
     let (field_visitor, fields_stmt, visit_map) = if cattrs.has_flatten() {
         deserialize_struct_as_map_visitor(&type_path, params, fields, cattrs)
@@ -838,6 +910,10 @@ fn deserialize_struct(
         quote! {
             _serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
         }
+    } else if is_enum && cattrs.has_flatten() {
+        quote! {
+            _serde::de::VariantAccess::newtype_variant_seed(__variant, #visitor_expr)
+        }
     } else if is_enum {
         quote! {
             _serde::de::VariantAccess::struct_variant(__variant, FIELDS, #visitor_expr)
@@ -875,6 +951,23 @@ fn deserialize_struct(
         _ => None,
     };
 
+    let visitor_seed = if is_enum && cattrs.has_flatten() {
+        Some(quote! {
+            impl #de_impl_generics _serde::de::DeserializeSeed<#delife> for __Visitor #de_ty_generics #where_clause {
+                type Value = #this #ty_generics;
+
+                fn deserialize<__D>(self, __deserializer: __D) -> _serde::export::Result<Self::Value, __D::Error>
+                where
+                    __D: _serde::Deserializer<'de>,
+                {
+                    _serde::Deserializer::deserialize_map(__deserializer, self)
+                }
+            }
+        })
+    } else {
+        None
+    };
+
     quote_block! {
         #field_visitor
 
@@ -901,6 +994,8 @@ fn deserialize_struct(
             }
         }
 
+        #visitor_seed
+
         #fields_stmt
 
         #dispatch
@@ -913,7 +1008,7 @@ fn deserialize_struct_in_place(
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
 ) -> Option<Fragment> {
     let is_enum = variant_ident.is_some();
 
@@ -933,7 +1028,7 @@ fn deserialize_struct_in_place(
         None => format!("struct {}", params.type_name()),
     };
 
-    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs));
+    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, &expecting));
 
     let (field_visitor, fields_stmt, visit_map) =
         deserialize_struct_as_struct_in_place_visitor(params, fields, cattrs);
@@ -1193,7 +1288,7 @@ fn deserialize_internally_tagged_enum(
 
         #variants_stmt
 
-        let __tagged = try!(_serde::Deserializer::private_deserialize_internally_tagged_enum(
+        let __tagged = try!(_serde::Deserializer::deserialize_any(
             __deserializer,
             _serde::private::de::TaggedContentVisitor::<__Field>::new(#tag)));
 
@@ -1298,7 +1393,7 @@ fn deserialize_adjacently_tagged_enum(
             .filter(|&(_, variant)| !variant.attrs.skip_deserializing() && is_unit(variant))
             .map(|(i, variant)| {
                 let variant_index = field_i(i);
-                let variant_ident = variant.ident;
+                let variant_ident = &variant.ident;
                 quote! {
                     __Field::#variant_index => _serde::export::Ok(#this::#variant_ident),
                 }
@@ -1359,6 +1454,21 @@ fn deserialize_adjacently_tagged_enum(
         }
     };
 
+    let finish_content_then_tag = if variant_arms.is_empty() {
+        quote! {
+            match try!(_serde::de::MapAccess::next_value::<__Field>(&mut __map)) {}
+        }
+    } else {
+        quote! {
+            let __ret = try!(match try!(_serde::de::MapAccess::next_value(&mut __map)) {
+                // Deserialize the buffered content now that we know the variant.
+                #(#variant_arms)*
+            });
+            // Visit remaining keys, looking for duplicates.
+            #visit_remaining_keys
+        }
+    };
+
     quote_block! {
         #variant_visitor
 
@@ -1435,13 +1545,7 @@ fn deserialize_adjacently_tagged_enum(
                             // Second key is the tag.
                             _serde::export::Some(_serde::private::de::TagOrContentField::Tag) => {
                                 let __deserializer = _serde::private::de::ContentDeserializer::<__A::Error>::new(__content);
-                                // Parse the tag.
-                                let __ret = try!(match try!(_serde::de::MapAccess::next_value(&mut __map)) {
-                                    // Deserialize the buffered content now that we know the variant.
-                                    #(#variant_arms)*
-                                });
-                                // Visit remaining keys, looking for duplicates.
-                                #visit_remaining_keys
+                                #finish_content_then_tag
                             }
                             // Second key is a duplicate of the content.
                             _serde::export::Some(_serde::private::de::TagOrContentField::Content) => {
@@ -1553,7 +1657,7 @@ fn deserialize_externally_tagged_variant(
         };
     }
 
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     match variant.style {
         Style::Unit => {
@@ -1584,19 +1688,19 @@ fn deserialize_internally_tagged_variant(
     params: &Parameters,
     variant: &Variant,
     cattrs: &attr::Container,
-    deserializer: Tokens,
+    deserializer: TokenStream,
 ) -> Fragment {
     if variant.attrs.deserialize_with().is_some() {
         return deserialize_untagged_variant(params, variant, cattrs, deserializer);
     }
 
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     match variant.style {
         Style::Unit => {
             let this = &params.this;
             let type_name = params.type_name();
-            let variant_name = variant.ident.as_ref();
+            let variant_name = variant.ident.to_string();
             quote_block! {
                 try!(_serde::Deserializer::deserialize_any(#deserializer, _serde::private::de::InternallyTaggedUnitVisitor::new(#type_name, #variant_name)));
                 _serde::export::Ok(#this::#variant_ident)
@@ -1624,7 +1728,7 @@ fn deserialize_untagged_variant(
     params: &Parameters,
     variant: &Variant,
     cattrs: &attr::Container,
-    deserializer: Tokens,
+    deserializer: TokenStream,
 ) -> Fragment {
     if let Some(path) = variant.attrs.deserialize_with() {
         let (wrapper, wrapper_ty, unwrap_fn) = wrap_deserialize_variant_with(params, variant, path);
@@ -1635,13 +1739,13 @@ fn deserialize_untagged_variant(
         };
     }
 
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     match variant.style {
         Style::Unit => {
             let this = &params.this;
             let type_name = params.type_name();
-            let variant_name = variant.ident.as_ref();
+            let variant_name = variant.ident.to_string();
             quote_expr! {
                 match _serde::Deserializer::deserialize_any(
                     #deserializer,
@@ -1677,7 +1781,7 @@ fn deserialize_untagged_variant(
 }
 
 fn deserialize_externally_tagged_newtype_variant(
-    variant_ident: syn::Ident,
+    variant_ident: &syn::Ident,
     params: &Parameters,
     field: &Field,
 ) -> Fragment {
@@ -1704,10 +1808,10 @@ fn deserialize_externally_tagged_newtype_variant(
 }
 
 fn deserialize_untagged_newtype_variant(
-    variant_ident: syn::Ident,
+    variant_ident: &syn::Ident,
     params: &Parameters,
     field: &Field,
-    deserializer: &Tokens,
+    deserializer: &TokenStream,
 ) -> Fragment {
     let this = &params.this;
     let field_ty = field.ty;
@@ -1721,10 +1825,8 @@ fn deserialize_untagged_newtype_variant(
         }
         Some(path) => {
             quote_block! {
-                let __value: #field_ty = _serde::export::Result::map(
-                    #path(#deserializer),
-                    #this::#variant_ident);
-                __value
+                let __value: _serde::export::Result<#field_ty, _> = #path(#deserializer);
+                _serde::export::Result::map(__value, #this::#variant_ident)
             }
         }
     }
@@ -1738,7 +1840,7 @@ fn deserialize_generated_identifier(
     let this = quote!(__Field);
     let field_idents: &Vec<_> = &fields.iter().map(|&(_, ref ident)| ident).collect();
 
-    let (ignore_variant, fallthrough) = if cattrs.has_flatten() {
+    let (ignore_variant, fallthrough) = if !is_variant && cattrs.has_flatten() {
         let ignore_variant = quote!(__other(_serde::private::de::Content<'de>),);
         let fallthrough = quote!(_serde::export::Ok(__Field::__other(__value)));
         (Some(ignore_variant), Some(fallthrough))
@@ -1755,10 +1857,10 @@ fn deserialize_generated_identifier(
         fields,
         is_variant,
         fallthrough,
-        cattrs.has_flatten(),
+        !is_variant && cattrs.has_flatten(),
     ));
 
-    let lifetime = if cattrs.has_flatten() {
+    let lifetime = if !is_variant && cattrs.has_flatten() {
         Some(quote!(<'de>))
     } else {
         None
@@ -1806,7 +1908,7 @@ fn deserialize_custom_identifier(
     let this = quote!(#this);
 
     let (ordinary, fallthrough) = if let Some(last) = variants.last() {
-        let last_ident = last.ident;
+        let last_ident = &last.ident;
         if last.attrs.other() {
             let ordinary = &variants[..variants.len() - 1];
             let fallthrough = quote!(_serde::export::Ok(#this::#last_ident));
@@ -1829,7 +1931,12 @@ fn deserialize_custom_identifier(
 
     let names_idents: Vec<_> = ordinary
         .iter()
-        .map(|variant| (variant.attrs.name().deserialize_name(), variant.ident))
+        .map(|variant| {
+            (
+                variant.attrs.name().deserialize_name(),
+                variant.ident.clone(),
+            )
+        })
         .collect();
 
     let names = names_idents.iter().map(|&(ref name, _)| name);
@@ -1882,10 +1989,10 @@ fn deserialize_custom_identifier(
 }
 
 fn deserialize_identifier(
-    this: &Tokens,
+    this: &TokenStream,
     fields: &[(String, Ident)],
     is_variant: bool,
-    fallthrough: Option<Tokens>,
+    fallthrough: Option<TokenStream>,
     collect_other_fields: bool,
 ) -> Fragment {
     let field_strs = fields.iter().map(|&(ref name, _)| name);
@@ -1923,9 +2030,7 @@ fn deserialize_identifier(
         value_as_borrowed_str_content,
         value_as_bytes_content,
         value_as_borrowed_bytes_content,
-    ) = if !collect_other_fields {
-        (None, None, None, None)
-    } else {
+    ) = if collect_other_fields {
         (
             Some(quote! {
                 let __value = _serde::private::de::Content::String(__value.to_string());
@@ -1940,6 +2045,8 @@ fn deserialize_identifier(
                 let __value = _serde::private::de::Content::Bytes(__value);
             }),
         )
+    } else {
+        (None, None, None, None)
     };
 
     let fallthrough_arm = if let Some(fallthrough) = fallthrough {
@@ -1954,7 +2061,7 @@ fn deserialize_identifier(
         }
     };
 
-    let variant_indices = 0u64..;
+    let variant_indices = 0_u64..;
     let fallthrough_msg = format!("{} index 0 <= i < {}", index_expecting, fields.len());
     let visit_other = if collect_other_fields {
         quote! {
@@ -2139,7 +2246,7 @@ fn deserialize_identifier(
 }
 
 fn deserialize_struct_as_struct_visitor(
-    struct_path: &Tokens,
+    struct_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
@@ -2168,7 +2275,7 @@ fn deserialize_struct_as_struct_visitor(
 }
 
 fn deserialize_struct_as_map_visitor(
-    struct_path: &Tokens,
+    struct_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
@@ -2188,7 +2295,7 @@ fn deserialize_struct_as_map_visitor(
 }
 
 fn deserialize_map(
-    struct_path: &Tokens,
+    struct_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
@@ -2343,12 +2450,12 @@ fn deserialize_map(
     };
 
     let result = fields_names.iter().map(|&(field, ref name)| {
-        let ident = field.ident.expect("struct contains unnamed fields");
+        let member = &field.member;
         if field.attrs.skip_deserializing() {
             let value = Expr(expr_is_missing(field, cattrs));
-            quote!(#ident: #value)
+            quote!(#member: #value)
         } else {
-            quote!(#ident: #name)
+            quote!(#member: #name)
         }
     });
 
@@ -2453,19 +2560,19 @@ fn deserialize_map_in_place(
         .filter(|&&(field, _)| !field.attrs.skip_deserializing())
         .map(|&(field, ref name)| {
             let deser_name = field.attrs.name().deserialize_name();
-            let field_name = field.ident;
+            let member = &field.member;
 
             let visit = match field.attrs.deserialize_with() {
                 None => {
                     quote! {
-                        try!(_serde::de::MapAccess::next_value_seed(&mut __map, _serde::private::de::InPlaceSeed(&mut self.place.#field_name)))
+                        try!(_serde::de::MapAccess::next_value_seed(&mut __map, _serde::private::de::InPlaceSeed(&mut self.place.#member)))
                     }
                 }
                 Some(path) => {
                     let (wrapper, wrapper_ty) = wrap_deserialize_field_with(params, field.ty, path);
                     quote!({
                         #wrapper
-                        self.place.#field_name = try!(_serde::de::MapAccess::next_value::<#wrapper_ty>(&mut __map)).value
+                        self.place.#member = try!(_serde::de::MapAccess::next_value::<#wrapper_ty>(&mut __map)).value
                     })
                 }
             };
@@ -2516,13 +2623,10 @@ fn deserialize_map_in_place(
         .map(|&(field, ref name)| {
             let missing_expr = expr_is_missing(field, cattrs);
             // If missing_expr unconditionally returns an error, don't try
-            // to assign its value to self.place. Maybe this could be handled
-            // more elegantly.
-            if missing_expr
-                .as_ref()
-                .into_tokens()
-                .to_string()
-                .starts_with("return ")
+            // to assign its value to self.place.
+            if field.attrs.default().is_none()
+                && cattrs.default().is_none()
+                && field.attrs.deserialize_with().is_some()
             {
                 let missing_expr = Stmts(missing_expr);
                 quote! {
@@ -2531,11 +2635,11 @@ fn deserialize_map_in_place(
                     }
                 }
             } else {
-                let field_name = field.ident;
+                let member = &field.member;
                 let missing_expr = Expr(missing_expr);
                 quote! {
                     if !#name {
-                        self.place.#field_name = #missing_expr;
+                        self.place.#member = #missing_expr;
                     };
                 }
             }
@@ -2579,9 +2683,9 @@ fn field_i(i: usize) -> Ident {
 /// in a trait to prevent it from accessing the internal `Deserialize` state.
 fn wrap_deserialize_with(
     params: &Parameters,
-    value_ty: &Tokens,
+    value_ty: &TokenStream,
     deserialize_with: &syn::ExprPath,
-) -> (Tokens, Tokens) {
+) -> (TokenStream, TokenStream) {
     let this = &params.this;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
         split_with_de_lifetime(params);
@@ -2617,7 +2721,7 @@ fn wrap_deserialize_field_with(
     params: &Parameters,
     field_ty: &syn::Type,
     deserialize_with: &syn::ExprPath,
-) -> (Tokens, Tokens) {
+) -> (TokenStream, TokenStream) {
     wrap_deserialize_with(params, &quote!(#field_ty), deserialize_with)
 }
 
@@ -2625,9 +2729,9 @@ fn wrap_deserialize_variant_with(
     params: &Parameters,
     variant: &Variant,
     deserialize_with: &syn::ExprPath,
-) -> (Tokens, Tokens, Tokens) {
+) -> (TokenStream, TokenStream, TokenStream) {
     let this = &params.this;
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     let field_tys = variant.fields.iter().map(|field| field.ty);
     let (wrapper, wrapper_ty) =
@@ -2641,18 +2745,15 @@ fn wrap_deserialize_variant_with(
     });
     let unwrap_fn = match variant.style {
         Style::Struct if variant.fields.len() == 1 => {
-            let field_ident = variant.fields[0].ident.unwrap();
+            let member = &variant.fields[0].member;
             quote! {
-                |__wrap| #this::#variant_ident { #field_ident: __wrap.value }
+                |__wrap| #this::#variant_ident { #member: __wrap.value }
             }
         }
         Style::Struct => {
-            let field_idents = variant
-                .fields
-                .iter()
-                .map(|field| field.ident.as_ref().unwrap());
+            let members = variant.fields.iter().map(|field| &field.member);
             quote! {
-                |__wrap| #this::#variant_ident { #(#field_idents: __wrap.value.#field_access),* }
+                |__wrap| #this::#variant_ident { #(#members: __wrap.value.#field_access),* }
             }
         }
         Style::Tuple => quote! {
@@ -2682,8 +2783,8 @@ fn expr_is_missing(field: &Field, cattrs: &attr::Container) -> Fragment {
 
     match *cattrs.default() {
         attr::Default::Default | attr::Default::Path(_) => {
-            let ident = field.ident;
-            return quote_expr!(__default.#ident);
+            let member = &field.member;
+            return quote_expr!(__default.#member);
         }
         attr::Default::None => { /* below */ }
     }
@@ -2710,7 +2811,7 @@ struct DeImplGenerics<'a>(&'a Parameters);
 struct InPlaceImplGenerics<'a>(&'a Parameters);
 
 impl<'a> ToTokens for DeImplGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let mut generics = self.0.generics.clone();
         if let Some(de_lifetime) = self.0.borrowed.de_lifetime_def() {
             generics.params = Some(syn::GenericParam::Lifetime(de_lifetime))
@@ -2725,7 +2826,7 @@ impl<'a> ToTokens for DeImplGenerics<'a> {
 
 #[cfg(feature = "deserialize_in_place")]
 impl<'a> ToTokens for InPlaceImplGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let place_lifetime = place_lifetime();
         let mut generics = self.0.generics.clone();
 
@@ -2733,12 +2834,12 @@ impl<'a> ToTokens for InPlaceImplGenerics<'a> {
         for param in &mut generics.params {
             match *param {
                 syn::GenericParam::Lifetime(ref mut param) => {
-                    param.bounds.push(place_lifetime.lifetime);
+                    param.bounds.push(place_lifetime.lifetime.clone());
                 }
                 syn::GenericParam::Type(ref mut param) => {
-                    param
-                        .bounds
-                        .push(syn::TypeParamBound::Lifetime(place_lifetime.lifetime));
+                    param.bounds.push(syn::TypeParamBound::Lifetime(
+                        place_lifetime.lifetime.clone(),
+                    ));
                 }
                 syn::GenericParam::Const(_) => {}
             }
@@ -2770,7 +2871,7 @@ struct DeTypeGenerics<'a>(&'a Parameters);
 struct InPlaceTypeGenerics<'a>(&'a Parameters);
 
 impl<'a> ToTokens for DeTypeGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let mut generics = self.0.generics.clone();
         if self.0.borrowed.de_lifetime_def().is_some() {
             let def = syn::LifetimeDef {
@@ -2791,7 +2892,7 @@ impl<'a> ToTokens for DeTypeGenerics<'a> {
 
 #[cfg(feature = "deserialize_in_place")]
 impl<'a> ToTokens for InPlaceTypeGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let mut generics = self.0.generics.clone();
         generics.params = Some(syn::GenericParam::Lifetime(place_lifetime()))
             .into_iter()

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

@@ -8,7 +8,7 @@
 
 use internals::attr;
 use internals::check;
-use internals::Ctxt;
+use internals::{Ctxt, Derive};
 use syn;
 use syn::punctuated::Punctuated;
 
@@ -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 {
@@ -86,13 +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
     }
 }
@@ -124,7 +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,
@@ -166,7 +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

@@ -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,
@@ -181,6 +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");
@@ -200,7 +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());
                         }
@@ -216,7 +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!(
@@ -228,13 +230,18 @@ 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 {
+                    Meta(Word(ref word)) if word == "default" => match item.data {
                         syn::Data::Struct(syn::DataStruct {
                             fields: syn::Fields::Named(_),
                             ..
@@ -249,7 +256,7 @@ 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(_),
@@ -268,7 +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);
@@ -284,7 +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();
                         }
@@ -295,7 +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());
@@ -309,7 +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());
@@ -324,23 +331,23 @@ 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) {
+                        if let Ok(path) = parse_lit_into_path(cx, &m.ident, &m.lit) {
                             if is_primitive_path(&path, "Self") {
-                                remote.set(item.ident.into());
+                                remote.set(item.ident.clone().into());
                             } else {
                                 remote.set(path);
                             }
@@ -348,12 +355,12 @@ impl Container {
                     }
 
                     // 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();
                     }
 
@@ -376,6 +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),
@@ -398,6 +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
     }
@@ -527,6 +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,
@@ -542,6 +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");
@@ -552,7 +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());
                         }
@@ -568,7 +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!(
@@ -580,24 +596,48 @@ 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
@@ -615,14 +655,14 @@ impl Variant {
 
                     // 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);
                         }
                     }
@@ -663,6 +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(),
@@ -689,6 +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
     }
@@ -726,6 +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.
@@ -738,6 +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(
@@ -767,9 +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
@@ -782,7 +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());
                         }
@@ -797,57 +855,57 @@ 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
@@ -866,7 +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);
@@ -882,7 +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);
                         }
@@ -890,9 +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) {
@@ -909,13 +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();
                     }
 
@@ -992,7 +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);
@@ -1020,6 +1076,7 @@ impl Field {
             borrowed_lifetimes: borrowed_lifetimes,
             getter: getter.get(),
             flatten: flatten.get(),
+            transparent: false,
         }
     }
 
@@ -1079,6 +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>);
@@ -1091,21 +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);
                 }
             }
@@ -1154,8 +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 {
@@ -1169,7 +1235,7 @@ 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())))
@@ -1177,7 +1243,7 @@ fn parse_lit_into_path(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn
 
 fn parse_lit_into_expr_path(
     cx: &Ctxt,
-    attr_name: &str,
+    attr_name: &Ident,
     lit: &syn::Lit,
 ) -> Result<syn::ExprPath, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
@@ -1187,8 +1253,8 @@ fn parse_lit_into_expr_path(
 
 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));
@@ -1203,7 +1269,7 @@ fn parse_lit_into_where(
         .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(|_| {
@@ -1219,7 +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));
@@ -1240,7 +1306,7 @@ 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));
             }
         }
@@ -1254,6 +1320,14 @@ fn parse_lit_into_lifetimes(
     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.
 //
@@ -1301,6 +1375,31 @@ fn is_cow(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
     }
 }
 
+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
 // false negatives and false positives.
 //
@@ -1321,7 +1420,7 @@ 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),
         _ => false,
@@ -1347,7 +1446,9 @@ fn is_primitive_type(ty: &syn::Type, primitive: &str) -> bool {
 }
 
 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.leading_colon.is_none()
+        && path.segments.len() == 1
+        && path.segments[0].ident == primitive
         && path.segments[0].arguments.is_empty()
 }
 

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 internals::ast::{Container, Data, Style};
+use internals::ast::{Container, Data, Field, Style};
 use internals::attr::{EnumTag, Identifier};
-use internals::Ctxt;
+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`
@@ -44,43 +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(_) => {
-            if cont.attrs.has_flatten() {
-                cx.error("#[serde(flatten)] cannot be used within enums");
-            }
-        }
-        Data::Struct(style, _) => {
-            for field in cont.data.all_fields() {
-                if !field.attrs.flatten() {
-                    continue;
-                }
-                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)]",
-                    );
+        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)]",
+        );
     }
 }
 
@@ -165,17 +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
                     ));
                 }
 
@@ -183,7 +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
                     ));
                 }
             }
@@ -198,17 +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
                     ));
                 }
             }
@@ -276,3 +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/mod.rs

@@ -14,3 +14,9 @@ pub use self::ctxt::Ctxt;
 
 mod case;
 mod check;
+
+#[derive(Copy, Clone)]
+pub enum Derive {
+    Serialize,
+    Deserialize,
+}

serde_derive/src/lib.rs

@@ -22,10 +22,23 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.46")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.62")]
+#![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)
+    allow(
+        enum_variant_names, redundant_field_names, too_many_arguments, used_underscore_binding,
+        cyclomatic_complexity
+    )
+)]
+// 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
+    )
 )]
 // The `quote!` macro requires deep recursion.
 #![recursion_limit = "512"]

serde_derive/src/pretend.rs

@@ -1,5 +1,4 @@
-use proc_macro2::Span;
-use quote::Tokens;
+use proc_macro2::{Span, TokenStream};
 use syn::Ident;
 
 use internals::ast::{Container, Data, Field, Style};
@@ -21,7 +20,7 @@ use internals::ast::{Container, Data, Field, Style};
 //     8 | enum EnumDef { V }
 //       |                ^
 //
-pub fn pretend_used(cont: &Container) -> Tokens {
+pub fn pretend_used(cont: &Container) -> TokenStream {
     let pretend_fields = pretend_fields_used(cont);
     let pretend_variants = pretend_variants_used(cont);
 
@@ -49,8 +48,8 @@ pub fn pretend_used(cont: &Container) -> Tokens {
 // 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) -> Tokens {
-    let type_ident = cont.ident;
+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 {
@@ -58,7 +57,7 @@ fn pretend_fields_used(cont: &Container) -> Tokens {
             .iter()
             .filter_map(|variant| match variant.style {
                 Style::Struct => {
-                    let variant_ident = variant.ident;
+                    let variant_ident = &variant.ident;
                     let pat = struct_pattern(&variant.fields);
                     Some(quote!(#type_ident::#variant_ident #pat))
                 }
@@ -93,7 +92,7 @@ fn pretend_fields_used(cont: &Container) -> Tokens {
 //         _ => {}
 //     }
 //
-fn pretend_variants_used(cont: &Container) -> Tokens {
+fn pretend_variants_used(cont: &Container) -> TokenStream {
     let variants = match cont.data {
         Data::Enum(ref variants) => variants,
         Data::Struct(_, _) => {
@@ -101,20 +100,20 @@ fn pretend_variants_used(cont: &Container) -> Tokens {
         }
     };
 
-    let type_ident = cont.ident;
+    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 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 names = variant.fields.iter().map(|field| field.ident);
-                quote!({ #(#names: #placeholders),* })
+                let members = variant.fields.iter().map(|field| &field.member);
+                quote!({ #(#members: #placeholders),* })
             }
             Style::Tuple | Style::Newtype => quote!(( #(#placeholders),* )),
             Style::Unit => quote!(),
@@ -133,9 +132,9 @@ fn pretend_variants_used(cont: &Container) -> Tokens {
     quote!(#(#cases)*)
 }
 
-fn struct_pattern(fields: &[Field]) -> Tokens {
-    let names = fields.iter().map(|field| field.ident);
+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!({ #(#names: ref #placeholders),* })
+    quote!({ #(#members: ref #placeholders),* })
 }

serde_derive/src/ser.rs

@@ -6,27 +6,24 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use proc_macro2::Span;
-use quote::Tokens;
+use proc_macro2::{Span, TokenStream};
 use syn::spanned::Spanned;
 use syn::{self, Ident, Index, Member};
 
 use bound;
 use fragment::{Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
-use internals::{attr, Ctxt};
+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 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::call_site());
@@ -112,7 +109,7 @@ impl Parameters {
 
         let this = match cont.attrs.remote() {
             Some(remote) => remote.clone(),
-            None => cont.ident.into(),
+            None => cont.ident.clone().into(),
         };
 
         let generics = build_generics(cont);
@@ -127,8 +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()
     }
 }
 
@@ -140,6 +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(
@@ -152,31 +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) => {
@@ -187,8 +187,28 @@ 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;
+    let self_var = &params.self_var;
     quote_block! {
         _serde::Serialize::serialize(
             &_serde::export::Into::<#type_into>::into(_serde::export::Clone::clone(#self_var)),
@@ -239,8 +259,28 @@ fn serialize_tuple_struct(
         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));
@@ -250,7 +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)
@@ -280,8 +320,7 @@ fn serialize_struct_as_struct(
         .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 })
             }
         })
@@ -316,8 +355,7 @@ fn serialize_struct_as_map(
             .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 })
                 }
             })
@@ -333,9 +371,9 @@ fn serialize_struct_as_map(
 }
 
 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;
+    let self_var = &params.self_var;
 
     let arms: Vec<_> = variants
         .iter()
@@ -357,9 +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!(
@@ -399,12 +437,9 @@ fn serialize_variant(
                 }
             }
             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),* }
                 }
             }
         };
@@ -510,7 +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);
@@ -632,20 +667,16 @@ fn serialize_adjacently_tagged_variant(
                 unreachable!()
             }
         }
-        Style::Newtype => vec![Ident::new("__field0", Span::call_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::call_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")
@@ -739,8 +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 {
@@ -789,6 +835,10 @@ 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 => {
@@ -807,10 +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),
             }
         })
@@ -863,15 +913,102 @@ 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::call_site());
@@ -915,17 +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();
@@ -979,8 +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)])
 }
 
@@ -988,16 +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::call_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();
@@ -1013,8 +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();
 
@@ -1060,7 +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 {
@@ -1068,8 +1207,8 @@ fn mut_if(is_mut: bool) -> Option<Tokens> {
     }
 }
 
-fn get_member(params: &Parameters, field: &Field, member: &Member) -> Tokens {
-    let self_var = params.self_var;
+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!(&#self_var.#member),
         (true, None) => {
@@ -1094,7 +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)
@@ -1108,7 +1247,7 @@ 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 => {
@@ -1128,7 +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

@@ -1,13 +1,12 @@
-use proc_macro2::{Op, Spacing};
-use quote::Tokens;
+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() -> Tokens {
+pub fn replacement() -> TokenStream {
     // Cannot pass `$expr` to `quote!` prior to Rust 1.17.0 so interpolate it.
-    let dollar = Op::new('$', Spacing::Alone);
+    let dollar = Punct::new('$', Spacing::Alone);
 
     quote! {
         #[allow(unused_macros)]

serde_derive_internals/Cargo.toml

@@ -15,8 +15,8 @@ include = ["Cargo.toml", "lib.rs", "src/**/*.rs", "README.md", "LICENSE-APACHE",
 path = "lib.rs"
 
 [dependencies]
-proc-macro2 = "0.3"
-syn = { version = "0.13", 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_test/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_test"
-version = "1.0.46" # remember to update html_root_url
+version = "1.0.62" # 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"
@@ -12,10 +12,10 @@ readme = "README.md"
 include = ["Cargo.toml", "src/**/*.rs", "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/src/de.rs

@@ -129,8 +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>
@@ -599,7 +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),
@@ -656,8 +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

@@ -161,7 +161,7 @@
 //! # }
 //! ```
 
-#![doc(html_root_url = "https://docs.rs/serde_test/1.0.46")]
+#![doc(html_root_url = "https://docs.rs/serde_test/1.0.62")]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
 #![cfg_attr(feature = "cargo-clippy", allow(float_cmp))]

test_suite/Cargo.toml

@@ -9,7 +9,7 @@ unstable = ["serde/unstable", "compiletest_rs"]
 
 [dev-dependencies]
 fnv = "1.0"
-proc-macro2 = "0.3"
+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/tests/compile-fail/precondition/deserialize_de_lifetime.rs

@@ -0,0 +1,15 @@
+// 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)] //~ ERROR: proc-macro derive panicked
+struct S<'de> {
+    s: &'de str, //~^^ HELP: cannot deserialize when there is a lifetime parameter called 'de
+}

test_suite/tests/compile-fail/precondition/deserialize_dst.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)] //~ ERROR: proc-macro derive panicked
+struct S {
+    string: String,
+    slice: [u8], //~^^^ HELP: cannot deserialize a dynamically sized struct
+}

test_suite/tests/compile-fail/transparent/at_most_one.rs

@@ -10,12 +10,11 @@
 extern crate serde_derive;
 
 #[derive(Serialize)] //~ ERROR: proc-macro derive panicked
-//~^ HELP: #[serde(flatten)] cannot be used within enums
-enum Foo {
-    A {
-        #[serde(flatten)]
-        fields: HashMap<String, String>,
-    }
+#[serde(transparent)]
+struct S {
+    //~^^^ HELP: #[serde(transparent)] requires struct to have at most one transparent field
+    a: u8,
+    b: u8,
 }
 
 fn main() {}

test_suite/tests/compile-fail/transparent/de_at_least_one.rs

@@ -0,0 +1,22 @@
+// 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)] //~ ERROR: proc-macro derive panicked
+#[serde(transparent)]
+struct S {
+    //~^^^ HELP: #[serde(transparent)] requires at least one field that is neither skipped nor has a default
+    #[serde(skip)]
+    a: u8,
+    #[serde(default)]
+    b: u8,
+}
+
+fn main() {}

test_suite/tests/compile-fail/transparent/ser_at_least_one.rs

@@ -0,0 +1,20 @@
+// 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)] //~ ERROR: proc-macro derive panicked
+#[serde(transparent)]
+struct S {
+    //~^^^ HELP: #[serde(transparent)] requires at least one field that is not skipped
+    #[serde(skip)]
+    a: u8,
+}
+
+fn main() {}

test_suite/tests/test_annotations.rs

@@ -15,6 +15,7 @@ extern crate serde;
 use self::serde::de::{self, Unexpected};
 use self::serde::{Deserialize, Deserializer, Serialize, Serializer};
 use std::collections::HashMap;
+use std::marker::PhantomData;
 
 extern crate serde_test;
 use self::serde_test::{
@@ -657,6 +658,44 @@ fn test_skip_serializing_struct() {
     );
 }
 
+#[derive(Debug, PartialEq, Serialize)]
+struct SkipSerializingTupleStruct<'a, B, C>(
+    &'a i8,
+    #[serde(skip_serializing)] B,
+    #[serde(skip_serializing_if = "ShouldSkip::should_skip")] C,
+)
+where
+    C: ShouldSkip;
+
+#[test]
+fn test_skip_serializing_tuple_struct() {
+    let a = 1;
+    assert_ser_tokens(
+        &SkipSerializingTupleStruct(&a, 2, 3),
+        &[
+            Token::TupleStruct {
+                name: "SkipSerializingTupleStruct",
+                len: 2,
+            },
+            Token::I8(1),
+            Token::I32(3),
+            Token::TupleStructEnd,
+        ],
+    );
+
+    assert_ser_tokens(
+        &SkipSerializingTupleStruct(&a, 2, 123),
+        &[
+            Token::TupleStruct {
+                name: "SkipSerializingTupleStruct",
+                len: 1,
+            },
+            Token::I8(1),
+            Token::TupleStructEnd,
+        ],
+    );
+}
+
 #[derive(Debug, PartialEq, Serialize, Deserialize)]
 struct SkipStruct<B> {
     a: i8,
@@ -705,6 +744,11 @@ where
         #[serde(skip_serializing_if = "ShouldSkip::should_skip")]
         c: C,
     },
+    Tuple(
+        &'a i8,
+        #[serde(skip_serializing)] B,
+        #[serde(skip_serializing_if = "ShouldSkip::should_skip")] C,
+    ),
 }
 
 #[test]
@@ -743,6 +787,33 @@ fn test_skip_serializing_enum() {
             Token::StructVariantEnd,
         ],
     );
+
+    assert_ser_tokens(
+        &SkipSerializingEnum::Tuple(&a, 2, 3),
+        &[
+            Token::TupleVariant {
+                name: "SkipSerializingEnum",
+                variant: "Tuple",
+                len: 2,
+            },
+            Token::I8(1),
+            Token::I32(3),
+            Token::TupleVariantEnd,
+        ],
+    );
+
+    assert_ser_tokens(
+        &SkipSerializingEnum::Tuple(&a, 2, 123),
+        &[
+            Token::TupleVariant {
+                name: "SkipSerializingEnum",
+                variant: "Tuple",
+                len: 1,
+            },
+            Token::I8(1),
+            Token::TupleVariantEnd,
+        ],
+    );
 }
 
 #[derive(Debug, PartialEq)]
@@ -1230,7 +1301,7 @@ fn test_invalid_length_enum() {
             Token::I32(1),
             Token::TupleVariantEnd,
         ],
-        "invalid length 1, expected tuple of 3 elements",
+        "invalid length 1, expected tuple variant InvalidLengthEnum::A with 3 elements",
     );
     assert_de_tokens_error::<InvalidLengthEnum>(
         &[
@@ -1242,7 +1313,7 @@ fn test_invalid_length_enum() {
             Token::I32(1),
             Token::TupleVariantEnd,
         ],
-        "invalid length 1, expected tuple of 2 elements",
+        "invalid length 1, expected tuple variant InvalidLengthEnum::B with 2 elements",
     );
 }
 
@@ -1839,3 +1910,293 @@ fn test_flatten_internally_tagged() {
         ],
     );
 }
+
+#[test]
+fn test_externally_tagged_enum_containing_flatten() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    enum Data {
+        A {
+            a: i32,
+            #[serde(flatten)]
+            flat: Flat,
+        },
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Flat {
+        b: i32,
+    }
+
+    let data = Data::A {
+        a: 0,
+        flat: Flat { b: 0 },
+    };
+
+    assert_tokens(
+        &data,
+        &[
+            Token::NewtypeVariant {
+                name: "Data",
+                variant: "A",
+            },
+            Token::Map { len: None },
+            Token::Str("a"),
+            Token::I32(0),
+            Token::Str("b"),
+            Token::I32(0),
+            Token::MapEnd,
+        ],
+    );
+}
+
+#[test]
+fn test_internally_tagged_enum_containing_flatten() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(tag = "t")]
+    enum Data {
+        A {
+            a: i32,
+            #[serde(flatten)]
+            flat: Flat,
+        },
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Flat {
+        b: i32,
+    }
+
+    let data = Data::A {
+        a: 0,
+        flat: Flat { b: 0 },
+    };
+
+    assert_tokens(
+        &data,
+        &[
+            Token::Map { len: None },
+            Token::Str("t"),
+            Token::Str("A"),
+            Token::Str("a"),
+            Token::I32(0),
+            Token::Str("b"),
+            Token::I32(0),
+            Token::MapEnd,
+        ],
+    );
+}
+
+#[test]
+fn test_adjacently_tagged_enum_containing_flatten() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(tag = "t", content = "c")]
+    enum Data {
+        A {
+            a: i32,
+            #[serde(flatten)]
+            flat: Flat,
+        },
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Flat {
+        b: i32,
+    }
+
+    let data = Data::A {
+        a: 0,
+        flat: Flat { b: 0 },
+    };
+
+    assert_tokens(
+        &data,
+        &[
+            Token::Struct {
+                name: "Data",
+                len: 2,
+            },
+            Token::Str("t"),
+            Token::Str("A"),
+            Token::Str("c"),
+            Token::Map { len: None },
+            Token::Str("a"),
+            Token::I32(0),
+            Token::Str("b"),
+            Token::I32(0),
+            Token::MapEnd,
+            Token::StructEnd,
+        ],
+    );
+}
+
+#[test]
+fn test_untagged_enum_containing_flatten() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(untagged)]
+    enum Data {
+        A {
+            a: i32,
+            #[serde(flatten)]
+            flat: Flat,
+        },
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Flat {
+        b: i32,
+    }
+
+    let data = Data::A {
+        a: 0,
+        flat: Flat { b: 0 },
+    };
+
+    assert_tokens(
+        &data,
+        &[
+            Token::Map { len: None },
+            Token::Str("a"),
+            Token::I32(0),
+            Token::Str("b"),
+            Token::I32(0),
+            Token::MapEnd,
+        ],
+    );
+}
+
+#[test]
+fn test_flatten_untagged_enum() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Outer {
+        #[serde(flatten)]
+        inner: Inner,
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(untagged)]
+    enum Inner {
+        Variant { a: i32 },
+    }
+
+    let data = Outer {
+        inner: Inner::Variant { a: 0 },
+    };
+
+    assert_tokens(
+        &data,
+        &[
+            Token::Map { len: None },
+            Token::Str("a"),
+            Token::I32(0),
+            Token::MapEnd,
+        ],
+    );
+}
+
+#[test]
+fn test_flatten_option() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Outer {
+        #[serde(flatten)]
+        inner1: Option<Inner1>,
+        #[serde(flatten)]
+        inner2: Option<Inner2>,
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Inner1 {
+        inner1: i32,
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Inner2 {
+        inner2: i32,
+    }
+
+    assert_tokens(
+        &Outer {
+            inner1: Some(Inner1 { inner1: 1 }),
+            inner2: Some(Inner2 { inner2: 2 }),
+        },
+        &[
+            Token::Map { len: None },
+            Token::Str("inner1"),
+            Token::I32(1),
+            Token::Str("inner2"),
+            Token::I32(2),
+            Token::MapEnd,
+        ],
+    );
+
+    assert_tokens(
+        &Outer {
+            inner1: Some(Inner1 { inner1: 1 }),
+            inner2: None,
+        },
+        &[
+            Token::Map { len: None },
+            Token::Str("inner1"),
+            Token::I32(1),
+            Token::MapEnd,
+        ],
+    );
+
+    assert_tokens(
+        &Outer {
+            inner1: None,
+            inner2: Some(Inner2 { inner2: 2 }),
+        },
+        &[
+            Token::Map { len: None },
+            Token::Str("inner2"),
+            Token::I32(2),
+            Token::MapEnd,
+        ],
+    );
+
+    assert_tokens(
+        &Outer {
+            inner1: None,
+            inner2: None,
+        },
+        &[Token::Map { len: None }, Token::MapEnd],
+    );
+}
+
+#[test]
+fn test_transparent_struct() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(transparent)]
+    struct Transparent {
+        #[serde(skip)]
+        a: bool,
+        b: u32,
+        #[serde(skip)]
+        c: bool,
+        d: PhantomData<()>,
+    }
+
+    assert_tokens(
+        &Transparent {
+            a: false,
+            b: 1,
+            c: false,
+            d: PhantomData,
+        },
+        &[Token::U32(1)],
+    );
+}
+
+#[test]
+fn test_transparent_tuple_struct() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(transparent)]
+    struct Transparent(
+        #[serde(skip)] bool,
+        u32,
+        #[serde(skip)] bool,
+        PhantomData<()>,
+    );
+
+    assert_tokens(&Transparent(false, 1, false, PhantomData), &[Token::U32(1)]);
+}

test_suite/tests/test_de.rs

@@ -17,15 +17,15 @@ use std::ffi::{CString, OsString};
 use std::net;
 use std::num::Wrapping;
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
-use std::sync::Arc;
+use std::rc::{Rc, Weak as RcWeak};
+use std::sync::{Arc, Weak as ArcWeak};
 use std::time::{Duration, UNIX_EPOCH};
 
 #[cfg(feature = "unstable")]
 use std::ffi::CStr;
 
 extern crate serde;
-use serde::Deserialize;
+use serde::{Deserialize, Deserializer};
 
 extern crate fnv;
 use self::fnv::FnvHasher;
@@ -182,6 +182,27 @@ macro_rules! declare_error_tests {
     }
 }
 
+#[derive(Debug)]
+struct SkipPartialEq<T>(T);
+
+impl<'de, T> Deserialize<'de> for SkipPartialEq<T>
+where
+    T: Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        T::deserialize(deserializer).map(SkipPartialEq)
+    }
+}
+
+impl<T> PartialEq for SkipPartialEq<T> {
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
 fn assert_de_tokens_ignore(ignorable_tokens: &[Token]) {
     #[derive(PartialEq, Debug, Deserialize)]
     struct IgnoreBase {
@@ -238,6 +259,27 @@ declare_tests! {
         0f32 => &[Token::F32(0.)],
         0f64 => &[Token::F64(0.)],
     }
+    test_small_int_to_128 {
+        1i128 => &[Token::I8(1)],
+        1i128 => &[Token::I16(1)],
+        1i128 => &[Token::I32(1)],
+        1i128 => &[Token::I64(1)],
+
+        1i128 => &[Token::U8(1)],
+        1i128 => &[Token::U16(1)],
+        1i128 => &[Token::U32(1)],
+        1i128 => &[Token::U64(1)],
+
+        1u128 => &[Token::I8(1)],
+        1u128 => &[Token::I16(1)],
+        1u128 => &[Token::I32(1)],
+        1u128 => &[Token::I64(1)],
+
+        1u128 => &[Token::U8(1)],
+        1u128 => &[Token::U16(1)],
+        1u128 => &[Token::U32(1)],
+        1u128 => &[Token::U64(1)],
+    }
     test_char {
         'a' => &[Token::Char('a')],
         'a' => &[Token::Str("a")],
@@ -788,11 +830,33 @@ declare_tests! {
             Token::Bool(true),
         ],
     }
+    test_rc_weak_some {
+        SkipPartialEq(RcWeak::<bool>::new()) => &[
+            Token::Some,
+            Token::Bool(true),
+        ],
+    }
+    test_rc_weak_none {
+        SkipPartialEq(RcWeak::<bool>::new()) => &[
+            Token::None,
+        ],
+    }
     test_arc {
         Arc::new(true) => &[
             Token::Bool(true),
         ],
     }
+    test_arc_weak_some {
+        SkipPartialEq(ArcWeak::<bool>::new()) => &[
+            Token::Some,
+            Token::Bool(true),
+        ],
+    }
+    test_arc_weak_none {
+        SkipPartialEq(ArcWeak::<bool>::new()) => &[
+            Token::None,
+        ],
+    }
     test_wrapping {
         Wrapping(1usize) => &[
             Token::U32(1),

test_suite/tests/test_gen.rs

@@ -216,6 +216,42 @@ fn test_gen() {
     }
     assert::<WithTraits2<X, X>>();
 
+    #[derive(Serialize, Deserialize)]
+    #[serde(bound = "D: SerializeWith + DeserializeWith")]
+    enum VariantWithTraits1<D, E> {
+        #[serde(
+            serialize_with = "SerializeWith::serialize_with",
+            deserialize_with = "DeserializeWith::deserialize_with"
+        )]
+        D(D),
+        #[serde(
+            serialize_with = "SerializeWith::serialize_with",
+            deserialize_with = "DeserializeWith::deserialize_with",
+            bound = "E: SerializeWith + DeserializeWith"
+        )]
+        E(E),
+    }
+    assert::<VariantWithTraits1<X, X>>();
+
+    #[derive(Serialize, Deserialize)]
+    #[serde(bound(serialize = "D: SerializeWith", deserialize = "D: DeserializeWith"))]
+    enum VariantWithTraits2<D, E> {
+        #[serde(
+            serialize_with = "SerializeWith::serialize_with",
+            deserialize_with = "DeserializeWith::deserialize_with"
+        )]
+        D(D),
+        #[serde(
+            serialize_with = "SerializeWith::serialize_with", bound(serialize = "E: SerializeWith")
+        )]
+        #[serde(
+            deserialize_with = "DeserializeWith::deserialize_with",
+            bound(deserialize = "E: DeserializeWith")
+        )]
+        E(E),
+    }
+    assert::<VariantWithTraits2<X, X>>();
+
     #[derive(Serialize, Deserialize)]
     struct CowStr<'a>(Cow<'a, str>);
     assert::<CowStr>();
@@ -567,6 +603,64 @@ fn test_gen() {
     }
 
     assert::<AssocDeriveMulti<i32, NoSerdeImpl>>();
+
+    #[derive(Serialize)]
+    #[serde(tag = "t", content = "c")]
+    enum EmptyAdjacentlyTagged {
+        #[allow(dead_code)]
+        Struct {},
+        #[allow(dead_code)]
+        Tuple(),
+    }
+
+    assert_ser::<EmptyAdjacentlyTagged>();
+
+    mod restricted {
+        mod inner {
+            #[derive(Serialize, Deserialize)]
+            struct Restricted {
+                pub(super) a: usize,
+                pub(in super::inner) b: usize,
+            }
+        }
+    }
+
+    #[derive(Deserialize)]
+    #[serde(tag = "t", content = "c")]
+    enum AdjacentlyTaggedVoid {}
+
+    #[derive(Serialize, Deserialize)]
+    enum SkippedVariant<T> {
+        #[serde(skip)]
+        #[allow(dead_code)]
+        T(T),
+        Unit,
+    }
+
+    assert::<SkippedVariant<X>>();
+
+    #[derive(Deserialize)]
+    struct ImpliciltyBorrowedOption<'a> {
+        option: std::option::Option<&'a str>,
+    }
+
+    #[derive(Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum UntaggedNewtypeVariantWith {
+        Newtype(
+            #[serde(serialize_with = "ser_x")]
+            #[serde(deserialize_with = "de_x")]
+            X,
+        ),
+    }
+
+    #[derive(Serialize, Deserialize)]
+    #[serde(transparent)]
+    struct TransparentWith {
+        #[serde(serialize_with = "ser_x")]
+        #[serde(deserialize_with = "de_x")]
+        x: X,
+    }
 }
 
 //////////////////////////////////////////////////////////////////////////

test_suite/tests/test_ser.rs

@@ -11,11 +11,12 @@ extern crate serde_derive;
 
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
 use std::ffi::CString;
+use std::mem;
 use std::net;
 use std::num::Wrapping;
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
-use std::sync::Arc;
+use std::rc::{Rc, Weak as RcWeak};
+use std::sync::{Arc, Weak as ArcWeak};
 use std::time::{Duration, UNIX_EPOCH};
 
 #[cfg(unix)]
@@ -398,11 +399,41 @@ declare_tests! {
             Token::Bool(true),
         ],
     }
+    test_rc_weak_some {
+        {
+            let rc = Rc::new(true);
+            mem::forget(rc.clone());
+            Rc::downgrade(&rc)
+        } => &[
+            Token::Some,
+            Token::Bool(true),
+        ],
+    }
+    test_rc_weak_none {
+        RcWeak::<bool>::new() => &[
+            Token::None,
+        ],
+    }
     test_arc {
         Arc::new(true) => &[
             Token::Bool(true),
         ],
     }
+    test_arc_weak_some {
+        {
+            let arc = Arc::new(true);
+            mem::forget(arc.clone());
+            Arc::downgrade(&arc)
+        } => &[
+            Token::Some,
+            Token::Bool(true),
+        ],
+    }
+    test_arc_weak_none {
+        ArcWeak::<bool>::new() => &[
+            Token::None,
+        ],
+    }
     test_wrapping {
         Wrapping(1usize) => &[
             Token::U64(1),
@@ -555,3 +586,10 @@ fn test_enum_skipped() {
         "the enum variant Enum::SkippedMap cannot be serialized",
     );
 }
+
+#[test]
+fn test_integer128() {
+    assert_ser_tokens_error(&1i128, &[], "i128 is not supported");
+
+    assert_ser_tokens_error(&1u128, &[], "u128 is not supported");
+}

test_suite/tests/test_value.rs

@@ -25,3 +25,21 @@ fn test_u32_to_enum() {
     let e: E = E::deserialize(deserializer).unwrap();
     assert_eq!(E::B, e);
 }
+
+#[test]
+fn test_integer128() {
+    let de_u128 = IntoDeserializer::<value::Error>::into_deserializer(1u128);
+    let de_i128 = IntoDeserializer::<value::Error>::into_deserializer(1i128);
+
+    // u128 to u128
+    assert_eq!(1u128, u128::deserialize(de_u128).unwrap());
+
+    // u128 to i128
+    assert_eq!(1i128, i128::deserialize(de_u128).unwrap());
+
+    // i128 to u128
+    assert_eq!(1u128, u128::deserialize(de_i128).unwrap());
+
+    // i128 to i128
+    assert_eq!(1i128, i128::deserialize(de_i128).unwrap());
+}