Release 1.0.169

Allow larger preallocated capacity for smaller elements

.gitattributes

@@ -1 +0,0 @@
-test_suite/tests/expand/*.expanded.rs linguist-generated

.github/workflows/ci.yml

@@ -3,6 +3,7 @@ name: CI
 on:
   push:
   pull_request:
+  workflow_dispatch:
   schedule: [cron: "40 1 * * *"]
 
 permissions:
@@ -127,6 +128,16 @@ jobs:
       - uses: dtolnay/rust-toolchain@1.36.0
       - run: cd serde && cargo build --no-default-features --features alloc
 
+  minimal:
+    name: Minimal versions
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@nightly
+      - run: cargo generate-lockfile -Z minimal-versions
+      - run: cargo check --locked --workspace
+
   clippy:
     name: Clippy
     runs-on: ubuntu-latest
@@ -149,6 +160,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - uses: dtolnay/rust-toolchain@miri
+      - run: cargo miri setup
       - run: cd serde && cargo miri test --features derive,rc,unstable
         env:
           MIRIFLAGS: -Zmiri-strict-provenance

README.md

@@ -48,7 +48,7 @@ serde_json = "1.0"
 <p></p>
 
 ```rust
-use serde::{Serialize, Deserialize};
+use serde::{Deserialize, Serialize};
 
 #[derive(Serialize, Deserialize, Debug)]
 struct Point {

crates-io.md

@@ -16,7 +16,7 @@ You may be looking for:
 ## Serde in action
 
 ```rust
-use serde::{Serialize, Deserialize};
+use serde::{Deserialize, Serialize};
 
 #[derive(Serialize, Deserialize, Debug)]
 struct Point {

serde/.clippy.toml

@@ -1 +0,0 @@
-msrv = "1.13.0"

serde/Cargo.toml

@@ -1,9 +1,9 @@
 [package]
 name = "serde"
-version = "1.0.157" # remember to update html_root_url and serde_derive dependency
+version = "1.0.169" # remember to update html_root_url and serde_derive dependency
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
-categories = ["encoding", "no-std"]
+categories = ["encoding", "no-std", "no-std::no-alloc"]
 description = "A generic serialization/deserialization framework"
 documentation = "https://docs.rs/serde"
 homepage = "https://serde.rs"
@@ -15,7 +15,7 @@ repository = "https://github.com/serde-rs/serde"
 rust-version = "1.19"
 
 [dependencies]
-serde_derive = { version = "=1.0.157", optional = true, path = "../serde_derive" }
+serde_derive = { version = "=1.0.169", optional = true, path = "../serde_derive" }
 
 [dev-dependencies]
 serde_derive = { version = "1.0", path = "../serde_derive" }

serde/src/de/ignored_any.rs

@@ -10,13 +10,12 @@ use de::{
 /// any type, except that it does not store any information about the data that
 /// gets deserialized.
 ///
-/// ```edition2018
-/// use std::fmt;
-/// use std::marker::PhantomData;
-///
+/// ```edition2021
 /// use serde::de::{
 ///     self, Deserialize, DeserializeSeed, Deserializer, IgnoredAny, SeqAccess, Visitor,
 /// };
+/// use std::fmt;
+/// use std::marker::PhantomData;
 ///
 /// /// A seed that can be used to deserialize only the `n`th element of a sequence
 /// /// while efficiently discarding elements of any type before or after index `n`.
@@ -108,7 +107,7 @@ use de::{
 /// #     Ok(())
 /// # }
 /// ```
-#[derive(Copy, Clone, Debug, Default)]
+#[derive(Copy, Clone, Debug, Default, PartialEq)]
 pub struct IgnoredAny;
 
 impl<'de> Visitor<'de> for IgnoredAny {

serde/src/de/impls.rs

@@ -681,8 +681,8 @@ impl<'de> Visitor<'de> for CStringVisitor {
     where
         A: SeqAccess<'de>,
     {
-        let len = size_hint::cautious(seq.size_hint());
-        let mut values = Vec::with_capacity(len);
+        let capacity = size_hint::cautious::<u8>(seq.size_hint());
+        let mut values = Vec::<u8>::with_capacity(capacity);
 
         while let Some(value) = try!(seq.next_element()) {
             values.push(value);
@@ -936,7 +936,7 @@ macro_rules! seq_impl {
                         A: SeqAccess<'de>,
                     {
                         $clear(&mut self.0);
-                        $reserve(&mut self.0, size_hint::cautious($access.size_hint()));
+                        $reserve(&mut self.0, size_hint::cautious::<T>($access.size_hint()));
 
                         // FIXME: try to overwrite old values here? (Vec, VecDeque, LinkedList)
                         while let Some(value) = try!($access.next_element()) {
@@ -962,7 +962,7 @@ seq_impl!(
     BinaryHeap<T: Ord>,
     seq,
     BinaryHeap::clear,
-    BinaryHeap::with_capacity(size_hint::cautious(seq.size_hint())),
+    BinaryHeap::with_capacity(size_hint::cautious::<T>(seq.size_hint())),
     BinaryHeap::reserve,
     BinaryHeap::push
 );
@@ -992,16 +992,17 @@ seq_impl!(
     HashSet<T: Eq + Hash, S: BuildHasher + Default>,
     seq,
     HashSet::clear,
-    HashSet::with_capacity_and_hasher(size_hint::cautious(seq.size_hint()), S::default()),
+    HashSet::with_capacity_and_hasher(size_hint::cautious::<T>(seq.size_hint()), S::default()),
     HashSet::reserve,
-    HashSet::insert);
+    HashSet::insert
+);
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 seq_impl!(
     VecDeque<T>,
     seq,
     VecDeque::clear,
-    VecDeque::with_capacity(size_hint::cautious(seq.size_hint())),
+    VecDeque::with_capacity(size_hint::cautious::<T>(seq.size_hint())),
     VecDeque::reserve,
     VecDeque::push_back
 );
@@ -1035,7 +1036,8 @@ where
             where
                 A: SeqAccess<'de>,
             {
-                let mut values = Vec::with_capacity(size_hint::cautious(seq.size_hint()));
+                let capacity = size_hint::cautious::<T>(seq.size_hint());
+                let mut values = Vec::<T>::with_capacity(capacity);
 
                 while let Some(value) = try!(seq.next_element()) {
                     values.push(value);
@@ -1071,7 +1073,7 @@ where
             where
                 A: SeqAccess<'de>,
             {
-                let hint = size_hint::cautious(seq.size_hint());
+                let hint = size_hint::cautious::<T>(seq.size_hint());
                 if let Some(additional) = hint.checked_sub(self.0.len()) {
                     self.0.reserve(additional);
                 }
@@ -1409,16 +1411,14 @@ macro_rules! map_impl {
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-map_impl!(
-    BTreeMap<K: Ord, V>,
-    map,
-    BTreeMap::new());
+map_impl!(BTreeMap<K: Ord, V>, map, BTreeMap::new());
 
 #[cfg(feature = "std")]
 map_impl!(
     HashMap<K: Eq + Hash, V, S: BuildHasher + Default>,
     map,
-    HashMap::with_capacity_and_hasher(size_hint::cautious(map.size_hint()), S::default()));
+    HashMap::with_capacity_and_hasher(size_hint::cautious::<(K, V)>(map.size_hint()), S::default())
+);
 
 ////////////////////////////////////////////////////////////////////////////////
 
@@ -1451,7 +1451,7 @@ macro_rules! variant_identifier {
             $($variant),*
         }
 
-        static $variants_name: &'static [&'static str] = &[$(stringify!($variant)),*];
+        static $variants_name: &[&str] = &[$(stringify!($variant)),*];
 
         impl<'de> Deserialize<'de> for $name_kind {
             fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
@@ -1588,7 +1588,7 @@ macro_rules! parse_socket_impl {
                 if deserializer.is_human_readable() {
                     deserializer.deserialize_str(FromStrVisitor::new($expecting))
                 } else {
-                    <(_, u16)>::deserialize(deserializer).map(|(ip, port)| $new(ip, port))
+                    <(_, u16)>::deserialize(deserializer).map($new)
                 }
             }
         }
@@ -1615,12 +1615,10 @@ impl<'de> Deserialize<'de> for net::SocketAddr {
 }
 
 #[cfg(feature = "std")]
-parse_socket_impl!("IPv4 socket address" net::SocketAddrV4, net::SocketAddrV4::new);
+parse_socket_impl!("IPv4 socket address" net::SocketAddrV4, |(ip, port)| net::SocketAddrV4::new(ip, port));
 
 #[cfg(feature = "std")]
-parse_socket_impl!("IPv6 socket address" net::SocketAddrV6, |ip, port| net::SocketAddrV6::new(
-    ip, port, 0, 0
-));
+parse_socket_impl!("IPv6 socket address" net::SocketAddrV6, |(ip, port)| net::SocketAddrV6::new(ip, port, 0, 0));
 
 ////////////////////////////////////////////////////////////////////////////////
 
@@ -2099,7 +2097,7 @@ impl<'de> Deserialize<'de> for Duration {
             }
         }
 
-        const FIELDS: &'static [&'static str] = &["secs", "nanos"];
+        const FIELDS: &[&str] = &["secs", "nanos"];
         deserializer.deserialize_struct("Duration", FIELDS, DurationVisitor)
     }
 }
@@ -2241,7 +2239,7 @@ impl<'de> Deserialize<'de> for SystemTime {
             }
         }
 
-        const FIELDS: &'static [&'static str] = &["secs_since_epoch", "nanos_since_epoch"];
+        const FIELDS: &[&str] = &["secs_since_epoch", "nanos_since_epoch"];
         let duration = try!(deserializer.deserialize_struct("SystemTime", FIELDS, DurationVisitor));
         #[cfg(not(no_systemtime_checked_add))]
         let ret = UNIX_EPOCH
@@ -2259,9 +2257,9 @@ impl<'de> Deserialize<'de> for SystemTime {
 //
 //     #[derive(Deserialize)]
 //     #[serde(deny_unknown_fields)]
-//     struct Range {
-//         start: u64,
-//         end: u32,
+//     struct Range<Idx> {
+//         start: Idx,
+//         end: Idx,
 //     }
 impl<'de, Idx> Deserialize<'de> for Range<Idx>
 where
@@ -2309,7 +2307,7 @@ mod range {
 
     use de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
 
-    pub const FIELDS: &'static [&'static str] = &["start", "end"];
+    pub const FIELDS: &[&str] = &["start", "end"];
 
     // If this were outside of the serde crate, it would just use:
     //
@@ -2435,6 +2433,282 @@ mod range {
 
 ////////////////////////////////////////////////////////////////////////////////
 
+// Similar to:
+//
+//     #[derive(Deserialize)]
+//     #[serde(deny_unknown_fields)]
+//     struct RangeFrom<Idx> {
+//         start: Idx,
+//     }
+impl<'de, Idx> Deserialize<'de> for RangeFrom<Idx>
+where
+    Idx: Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let start = try!(deserializer.deserialize_struct(
+            "RangeFrom",
+            range_from::FIELDS,
+            range_from::RangeFromVisitor {
+                expecting: "struct RangeFrom",
+                phantom: PhantomData,
+            },
+        ));
+        Ok(start..)
+    }
+}
+
+mod range_from {
+    use lib::*;
+
+    use de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
+
+    pub const FIELDS: &[&str] = &["end"];
+
+    // If this were outside of the serde crate, it would just use:
+    //
+    //    #[derive(Deserialize)]
+    //    #[serde(field_identifier, rename_all = "lowercase")]
+    enum Field {
+        End,
+    }
+
+    impl<'de> Deserialize<'de> for Field {
+        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            struct FieldVisitor;
+
+            impl<'de> Visitor<'de> for FieldVisitor {
+                type Value = Field;
+
+                fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("`end`")
+                }
+
+                fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    match value {
+                        "end" => Ok(Field::End),
+                        _ => Err(Error::unknown_field(value, FIELDS)),
+                    }
+                }
+
+                fn visit_bytes<E>(self, value: &[u8]) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    match value {
+                        b"end" => Ok(Field::End),
+                        _ => {
+                            let value = ::__private::from_utf8_lossy(value);
+                            Err(Error::unknown_field(&*value, FIELDS))
+                        }
+                    }
+                }
+            }
+
+            deserializer.deserialize_identifier(FieldVisitor)
+        }
+    }
+
+    pub struct RangeFromVisitor<Idx> {
+        pub expecting: &'static str,
+        pub phantom: PhantomData<Idx>,
+    }
+
+    impl<'de, Idx> Visitor<'de> for RangeFromVisitor<Idx>
+    where
+        Idx: Deserialize<'de>,
+    {
+        type Value = Idx;
+
+        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+            formatter.write_str(self.expecting)
+        }
+
+        fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+        where
+            A: SeqAccess<'de>,
+        {
+            let end: Idx = match try!(seq.next_element()) {
+                Some(value) => value,
+                None => {
+                    return Err(Error::invalid_length(0, &self));
+                }
+            };
+            Ok(end)
+        }
+
+        fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
+        where
+            A: MapAccess<'de>,
+        {
+            let mut end: Option<Idx> = None;
+            while let Some(key) = try!(map.next_key()) {
+                match key {
+                    Field::End => {
+                        if end.is_some() {
+                            return Err(<A::Error as Error>::duplicate_field("end"));
+                        }
+                        end = Some(try!(map.next_value()));
+                    }
+                }
+            }
+            let end = match end {
+                Some(end) => end,
+                None => return Err(<A::Error as Error>::missing_field("end")),
+            };
+            Ok(end)
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Similar to:
+//
+//     #[derive(Deserialize)]
+//     #[serde(deny_unknown_fields)]
+//     struct RangeTo<Idx> {
+//         start: Idx,
+//     }
+impl<'de, Idx> Deserialize<'de> for RangeTo<Idx>
+where
+    Idx: Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let end = try!(deserializer.deserialize_struct(
+            "RangeTo",
+            range_to::FIELDS,
+            range_to::RangeToVisitor {
+                expecting: "struct RangeTo",
+                phantom: PhantomData,
+            },
+        ));
+        Ok(..end)
+    }
+}
+
+mod range_to {
+    use lib::*;
+
+    use de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
+
+    pub const FIELDS: &[&str] = &["start"];
+
+    // If this were outside of the serde crate, it would just use:
+    //
+    //    #[derive(Deserialize)]
+    //    #[serde(field_identifier, rename_all = "lowercase")]
+    enum Field {
+        Start,
+    }
+
+    impl<'de> Deserialize<'de> for Field {
+        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            struct FieldVisitor;
+
+            impl<'de> Visitor<'de> for FieldVisitor {
+                type Value = Field;
+
+                fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("`start`")
+                }
+
+                fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    match value {
+                        "start" => Ok(Field::Start),
+                        _ => Err(Error::unknown_field(value, FIELDS)),
+                    }
+                }
+
+                fn visit_bytes<E>(self, value: &[u8]) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    match value {
+                        b"start" => Ok(Field::Start),
+                        _ => {
+                            let value = ::__private::from_utf8_lossy(value);
+                            Err(Error::unknown_field(&*value, FIELDS))
+                        }
+                    }
+                }
+            }
+
+            deserializer.deserialize_identifier(FieldVisitor)
+        }
+    }
+
+    pub struct RangeToVisitor<Idx> {
+        pub expecting: &'static str,
+        pub phantom: PhantomData<Idx>,
+    }
+
+    impl<'de, Idx> Visitor<'de> for RangeToVisitor<Idx>
+    where
+        Idx: Deserialize<'de>,
+    {
+        type Value = Idx;
+
+        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+            formatter.write_str(self.expecting)
+        }
+
+        fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+        where
+            A: SeqAccess<'de>,
+        {
+            let start: Idx = match try!(seq.next_element()) {
+                Some(value) => value,
+                None => {
+                    return Err(Error::invalid_length(0, &self));
+                }
+            };
+            Ok(start)
+        }
+
+        fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
+        where
+            A: MapAccess<'de>,
+        {
+            let mut start: Option<Idx> = None;
+            while let Some(key) = try!(map.next_key()) {
+                match key {
+                    Field::Start => {
+                        if start.is_some() {
+                            return Err(<A::Error as Error>::duplicate_field("start"));
+                        }
+                        start = Some(try!(map.next_value()));
+                    }
+                }
+            }
+            let start = match start {
+                Some(start) => start,
+                None => return Err(<A::Error as Error>::missing_field("start")),
+            };
+            Ok(start)
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 #[cfg(any(not(no_ops_bound), all(feature = "std", not(no_collections_bound))))]
 impl<'de, T> Deserialize<'de> for Bound<T>
 where
@@ -2535,7 +2809,7 @@ where
             }
         }
 
-        const VARIANTS: &'static [&'static str] = &["Unbounded", "Included", "Excluded"];
+        const VARIANTS: &[&str] = &["Unbounded", "Included", "Excluded"];
 
         deserializer.deserialize_enum("Bound", VARIANTS, BoundVisitor(PhantomData))
     }
@@ -2643,7 +2917,7 @@ where
             }
         }
 
-        const VARIANTS: &'static [&'static str] = &["Ok", "Err"];
+        const VARIANTS: &[&str] = &["Ok", "Err"];
 
         deserializer.deserialize_enum("Result", VARIANTS, ResultVisitor(PhantomData))
     }
@@ -2709,7 +2983,7 @@ struct FromStrVisitor<T> {
 impl<T> FromStrVisitor<T> {
     fn new(expecting: &'static str) -> Self {
         FromStrVisitor {
-            expecting: expecting,
+            expecting,
             ty: PhantomData,
         }
     }

serde/src/de/mod.rs

@@ -162,7 +162,7 @@ macro_rules! declare_error_trait {
             ///
             /// The message should not be capitalized and should not end with a period.
             ///
-            /// ```edition2018
+            /// ```edition2021
             /// # use std::str::FromStr;
             /// #
             /// # struct IpAddr;
@@ -307,7 +307,7 @@ declare_error_trait!(Error: Sized + Debug + Display);
 /// This is used as an argument to the `invalid_type`, `invalid_value`, and
 /// `invalid_length` methods of the `Error` trait to build error messages.
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use std::fmt;
 /// #
 /// # use serde::de::{self, Unexpected, Visitor};
@@ -432,10 +432,9 @@ impl<'a> fmt::Display for Unexpected<'a> {
 /// Within the context of a `Visitor` implementation, the `Visitor` itself
 /// (`&self`) is an implementation of this trait.
 ///
-/// ```edition2018
-/// # use std::fmt;
-/// #
+/// ```edition2021
 /// # use serde::de::{self, Unexpected, Visitor};
+/// # use std::fmt;
 /// #
 /// # struct Example;
 /// #
@@ -457,7 +456,7 @@ impl<'a> fmt::Display for Unexpected<'a> {
 ///
 /// Outside of a `Visitor`, `&"..."` can be used.
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::de::{self, Unexpected};
 /// #
 /// # fn example<E>() -> Result<(), E>
@@ -465,7 +464,10 @@ impl<'a> fmt::Display for Unexpected<'a> {
 /// #     E: de::Error,
 /// # {
 /// #     let v = true;
-/// return Err(de::Error::invalid_type(Unexpected::Bool(v), &"a negative integer"));
+/// return Err(de::Error::invalid_type(
+///     Unexpected::Bool(v),
+///     &"a negative integer",
+/// ));
 /// # }
 /// ```
 pub trait Expected {
@@ -577,7 +579,7 @@ pub trait Deserialize<'de>: Sized {
 /// from the input string, but a `from_reader` function may only deserialize
 /// owned data.
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::de::{Deserialize, DeserializeOwned};
 /// # use std::io::{Read, Result};
 /// #
@@ -616,7 +618,7 @@ impl<T> DeserializeOwned for T where T: for<'de> Deserialize<'de> {}
 ///
 /// The canonical API for stateless deserialization looks like this:
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::Deserialize;
 /// #
 /// # enum Error {}
@@ -630,7 +632,7 @@ impl<T> DeserializeOwned for T where T: for<'de> Deserialize<'de> {}
 /// Adjusting an API like this to support stateful deserialization is a matter
 /// of accepting a seed as input:
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::de::DeserializeSeed;
 /// #
 /// # enum Error {}
@@ -663,12 +665,11 @@ impl<T> DeserializeOwned for T where T: for<'de> Deserialize<'de> {}
 /// into it. This requires stateful deserialization using the `DeserializeSeed`
 /// trait.
 ///
-/// ```edition2018
+/// ```edition2021
+/// use serde::de::{Deserialize, DeserializeSeed, Deserializer, SeqAccess, Visitor};
 /// use std::fmt;
 /// use std::marker::PhantomData;
 ///
-/// use serde::de::{Deserialize, DeserializeSeed, Deserializer, SeqAccess, Visitor};
-///
 /// // A DeserializeSeed implementation that uses stateful deserialization to
 /// // append array elements onto the end of an existing vector. The preexisting
 /// // state ("seed") in this case is the Vec<T>. The `deserialize` method of
@@ -709,7 +710,7 @@ impl<T> DeserializeOwned for T where T: for<'de> Deserialize<'de> {}
 ///             {
 ///                 // Decrease the number of reallocations if there are many elements
 ///                 if let Some(size_hint) = seq.size_hint() {
-///                    self.0.reserve(size_hint);
+///                     self.0.reserve(size_hint);
 ///                 }
 ///
 ///                 // Visit each element in the inner array and push it onto
@@ -1158,7 +1159,7 @@ pub trait Deserializer<'de>: Sized {
     /// human-readable one and binary formats like Postcard will prefer the
     /// compact one.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use std::ops::Add;
     /// # use std::str::FromStr;
     /// #
@@ -1249,10 +1250,9 @@ pub trait Deserializer<'de>: Sized {
 ///
 /// # Example
 ///
-/// ```edition2018
-/// # use std::fmt;
-/// #
+/// ```edition2021
 /// # use serde::de::{self, Unexpected, Visitor};
+/// # use std::fmt;
 /// #
 /// /// A visitor that deserializes a long string - a string containing at least
 /// /// some minimum number of bytes.
@@ -1290,7 +1290,7 @@ pub trait Visitor<'de>: Sized {
     /// "an integer between 0 and 64". The message should not be capitalized and
     /// should not end with a period.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use std::fmt;
     /// #
     /// # struct S {
@@ -2035,7 +2035,7 @@ pub trait VariantAccess<'de>: Sized {
     /// If the data contains a different type of variant, the following
     /// `invalid_type` error should be constructed:
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::de::{self, value, DeserializeSeed, Visitor, VariantAccess, Unexpected};
     /// #
     /// # struct X;
@@ -2075,7 +2075,7 @@ pub trait VariantAccess<'de>: Sized {
     /// If the data contains a different type of variant, the following
     /// `invalid_type` error should be constructed:
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::de::{self, value, DeserializeSeed, Visitor, VariantAccess, Unexpected};
     /// #
     /// # struct X;
@@ -2131,7 +2131,7 @@ pub trait VariantAccess<'de>: Sized {
     /// If the data contains a different type of variant, the following
     /// `invalid_type` error should be constructed:
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::de::{self, value, DeserializeSeed, Visitor, VariantAccess, Unexpected};
     /// #
     /// # struct X;
@@ -2148,11 +2148,7 @@ pub trait VariantAccess<'de>: Sized {
     /// #         T: DeserializeSeed<'de>,
     /// #     { unimplemented!() }
     /// #
-    /// fn tuple_variant<V>(
-    ///     self,
-    ///     _len: usize,
-    ///     _visitor: V,
-    /// ) -> Result<V::Value, Self::Error>
+    /// fn tuple_variant<V>(self, _len: usize, _visitor: V) -> Result<V::Value, Self::Error>
     /// where
     ///     V: Visitor<'de>,
     /// {
@@ -2178,7 +2174,7 @@ pub trait VariantAccess<'de>: Sized {
     /// If the data contains a different type of variant, the following
     /// `invalid_type` error should be constructed:
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::de::{self, value, DeserializeSeed, Visitor, VariantAccess, Unexpected};
     /// #
     /// # struct X;
@@ -2238,10 +2234,10 @@ pub trait VariantAccess<'de>: Sized {
 ///
 /// # Example
 ///
-/// ```edition2018
+/// ```edition2021
+/// use serde::de::{value, Deserialize, IntoDeserializer};
+/// use serde_derive::Deserialize;
 /// use std::str::FromStr;
-/// use serde::Deserialize;
-/// use serde::de::{value, IntoDeserializer};
 ///
 /// #[derive(Deserialize)]
 /// enum Setting {

serde/src/de/utf8.rs

@@ -31,7 +31,7 @@ pub fn encode(c: char) -> Encode {
         buf[3] = (code & 0x3F) as u8 | TAG_CONT;
         0
     };
-    Encode { buf: buf, pos: pos }
+    Encode { buf, pos }
 }
 
 pub struct Encode {

serde/src/de/value.rs

@@ -1,10 +1,10 @@
 //! Building blocks for deserializing basic values using the `IntoDeserializer`
 //! trait.
 //!
-//! ```edition2018
+//! ```edition2021
+//! use serde::de::{value, Deserialize, IntoDeserializer};
+//! use serde_derive::Deserialize;
 //! use std::str::FromStr;
-//! use serde::Deserialize;
-//! use serde::de::{value, IntoDeserializer};
 //!
 //! #[derive(Deserialize)]
 //! enum Setting {
@@ -251,7 +251,7 @@ macro_rules! primitive_deserializer {
             #[allow(missing_docs)]
             pub fn new(value: $ty) -> Self {
                 $name {
-                    value: value,
+                    value,
                     marker: PhantomData,
                 }
             }
@@ -330,7 +330,7 @@ impl<E> U32Deserializer<E> {
     #[allow(missing_docs)]
     pub fn new(value: u32) -> Self {
         U32Deserializer {
-            value: value,
+            value,
             marker: PhantomData,
         }
     }
@@ -419,7 +419,7 @@ impl<'a, E> StrDeserializer<'a, E> {
     #[allow(missing_docs)]
     pub fn new(value: &'a str) -> Self {
         StrDeserializer {
-            value: value,
+            value,
             marker: PhantomData,
         }
     }
@@ -498,7 +498,7 @@ impl<'de, E> BorrowedStrDeserializer<'de, E> {
     /// Create a new borrowed deserializer from the given string.
     pub fn new(value: &'de str) -> BorrowedStrDeserializer<'de, E> {
         BorrowedStrDeserializer {
-            value: value,
+            value,
             marker: PhantomData,
         }
     }
@@ -598,7 +598,7 @@ impl<E> StringDeserializer<E> {
     #[allow(missing_docs)]
     pub fn new(value: String) -> Self {
         StringDeserializer {
-            value: value,
+            value,
             marker: PhantomData,
         }
     }
@@ -701,7 +701,7 @@ impl<'a, E> CowStrDeserializer<'a, E> {
     #[allow(missing_docs)]
     pub fn new(value: Cow<'a, str>) -> Self {
         CowStrDeserializer {
-            value: value,
+            value,
             marker: PhantomData,
         }
     }
@@ -783,7 +783,7 @@ impl<'a, E> BytesDeserializer<'a, E> {
     /// Create a new deserializer from the given bytes.
     pub fn new(value: &'a [u8]) -> Self {
         BytesDeserializer {
-            value: value,
+            value,
             marker: PhantomData,
         }
     }
@@ -842,7 +842,7 @@ impl<'de, E> BorrowedBytesDeserializer<'de, E> {
     /// Create a new borrowed deserializer from the given borrowed bytes.
     pub fn new(value: &'de [u8]) -> Self {
         BorrowedBytesDeserializer {
-            value: value,
+            value,
             marker: PhantomData,
         }
     }
@@ -1053,7 +1053,7 @@ pub struct SeqAccessDeserializer<A> {
 impl<A> SeqAccessDeserializer<A> {
     /// Construct a new `SeqAccessDeserializer<A>`.
     pub fn new(seq: A) -> Self {
-        SeqAccessDeserializer { seq: seq }
+        SeqAccessDeserializer { seq }
     }
 }
 
@@ -1454,7 +1454,7 @@ pub struct MapAccessDeserializer<A> {
 impl<A> MapAccessDeserializer<A> {
     /// Construct a new `MapAccessDeserializer<A>`.
     pub fn new(map: A) -> Self {
-        MapAccessDeserializer { map: map }
+        MapAccessDeserializer { map }
     }
 }
 
@@ -1519,7 +1519,7 @@ pub struct EnumAccessDeserializer<A> {
 impl<A> EnumAccessDeserializer<A> {
     /// Construct a new `EnumAccessDeserializer<A>`.
     pub fn new(access: A) -> Self {
-        EnumAccessDeserializer { access: access }
+        EnumAccessDeserializer { access }
     }
 }
 
@@ -1613,7 +1613,7 @@ mod private {
     }
 
     pub fn map_as_enum<A>(map: A) -> MapAsEnum<A> {
-        MapAsEnum { map: map }
+        MapAsEnum { map }
     }
 
     impl<'de, A> VariantAccess<'de> for MapAsEnum<A>
@@ -1637,10 +1637,7 @@ mod private {
         where
             V: Visitor<'de>,
         {
-            self.map.next_value_seed(SeedTupleVariant {
-                len: len,
-                visitor: visitor,
-            })
+            self.map.next_value_seed(SeedTupleVariant { len, visitor })
         }
 
         fn struct_variant<V>(
@@ -1651,8 +1648,7 @@ mod private {
         where
             V: Visitor<'de>,
         {
-            self.map
-                .next_value_seed(SeedStructVariant { visitor: visitor })
+            self.map.next_value_seed(SeedStructVariant { visitor })
         }
     }
 

serde/src/integer128.rs

@@ -9,7 +9,7 @@
 /// or do not target platforms that lack 128-bit integers, do not need to
 /// bother with this macro and may assume support for 128-bit integers.
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::__private::doc::Error;
 /// #
 /// # struct MySerializer;
@@ -50,7 +50,7 @@
 /// When Serde is built with support for 128-bit integers, this macro expands
 /// transparently into just the input tokens.
 ///
-/// ```edition2018
+/// ```edition2021
 /// macro_rules! serde_if_integer128 {
 ///     ($($tt:tt)*) => {
 ///         $($tt)*
@@ -61,7 +61,7 @@
 /// When built without support for 128-bit integers, this macro expands to
 /// nothing.
 ///
-/// ```edition2018
+/// ```edition2021
 /// macro_rules! serde_if_integer128 {
 ///     ($($tt:tt)*) => {};
 /// }

serde/src/lib.rs

@@ -93,7 +93,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.157")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.169")]
 // 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
@@ -180,7 +180,7 @@ mod lib {
     pub use self::core::fmt::{self, Debug, Display};
     pub use self::core::marker::{self, PhantomData};
     pub use self::core::num::Wrapping;
-    pub use self::core::ops::Range;
+    pub use self::core::ops::{Range, RangeFrom, RangeTo};
     pub use self::core::option::{self, Option};
     pub use self::core::result::{self, Result};
 

serde/src/macros.rs

@@ -11,7 +11,7 @@
 /// input. This requires repetitive implementations of all the [`Deserializer`]
 /// trait methods.
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::forward_to_deserialize_any;
 /// # use serde::de::{value, Deserializer, Visitor};
 /// #
@@ -47,7 +47,7 @@
 /// methods so that they forward directly to [`Deserializer::deserialize_any`].
 /// You can choose which methods to forward.
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::forward_to_deserialize_any;
 /// # use serde::de::{value, Deserializer, Visitor};
 /// #
@@ -78,11 +78,10 @@
 /// called `V`. A different type parameter and a different lifetime can be
 /// specified explicitly if necessary.
 ///
-/// ```edition2018
-/// # use std::marker::PhantomData;
-/// #
+/// ```edition2021
 /// # use serde::forward_to_deserialize_any;
 /// # use serde::de::{value, Deserializer, Visitor};
+/// # use std::marker::PhantomData;
 /// #
 /// # struct MyDeserializer<V>(PhantomData<V>);
 /// #

serde/src/private/de.rs

@@ -474,7 +474,8 @@ mod content {
         where
             V: SeqAccess<'de>,
         {
-            let mut vec = Vec::with_capacity(size_hint::cautious(visitor.size_hint()));
+            let mut vec =
+                Vec::<Content>::with_capacity(size_hint::cautious::<Content>(visitor.size_hint()));
             while let Some(e) = try!(visitor.next_element()) {
                 vec.push(e);
             }
@@ -485,7 +486,10 @@ mod content {
         where
             V: MapAccess<'de>,
         {
-            let mut vec = Vec::with_capacity(size_hint::cautious(visitor.size_hint()));
+            let mut vec =
+                Vec::<(Content, Content)>::with_capacity(
+                    size_hint::cautious::<(Content, Content)>(visitor.size_hint()),
+                );
             while let Some(kv) = try!(visitor.next_entry()) {
                 vec.push(kv);
             }
@@ -518,7 +522,7 @@ mod content {
     impl<'de> TagOrContentVisitor<'de> {
         fn new(name: &'static str) -> Self {
             TagOrContentVisitor {
-                name: name,
+                name,
                 value: PhantomData,
             }
         }
@@ -797,51 +801,29 @@ mod content {
     /// Used by generated code to deserialize an internally tagged enum.
     ///
     /// Not public API.
-    pub struct TaggedContent<'de, T> {
-        pub tag: T,
-        pub content: Content<'de>,
-    }
-
-    /// Not public API.
-    pub struct TaggedContentVisitor<'de, T> {
+    pub struct TaggedContentVisitor<T> {
         tag_name: &'static str,
         expecting: &'static str,
-        value: PhantomData<TaggedContent<'de, T>>,
+        value: PhantomData<T>,
     }
 
-    impl<'de, T> TaggedContentVisitor<'de, T> {
+    impl<T> TaggedContentVisitor<T> {
         /// Visitor for the content of an internally tagged enum with the given
         /// tag name.
         pub fn new(name: &'static str, expecting: &'static str) -> Self {
             TaggedContentVisitor {
                 tag_name: name,
-                expecting: expecting,
+                expecting,
                 value: PhantomData,
             }
         }
     }
 
-    impl<'de, T> DeserializeSeed<'de> for TaggedContentVisitor<'de, T>
+    impl<'de, T> Visitor<'de> for TaggedContentVisitor<T>
     where
         T: Deserialize<'de>,
     {
-        type Value = TaggedContent<'de, T>;
-
-        fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
-        where
-            D: Deserializer<'de>,
-        {
-            // Internally tagged enums are only supported in self-describing
-            // formats.
-            deserializer.deserialize_any(self)
-        }
-    }
-
-    impl<'de, T> Visitor<'de> for TaggedContentVisitor<'de, T>
-    where
-        T: Deserialize<'de>,
-    {
-        type Value = TaggedContent<'de, T>;
+        type Value = (T, Content<'de>);
 
         fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
             fmt.write_str(self.expecting)
@@ -858,10 +840,7 @@ mod content {
                 }
             };
             let rest = de::value::SeqAccessDeserializer::new(seq);
-            Ok(TaggedContent {
-                tag: tag,
-                content: try!(Content::deserialize(rest)),
-            })
+            Ok((tag, try!(Content::deserialize(rest))))
         }
 
         fn visit_map<M>(self, mut map: M) -> Result<Self::Value, M::Error>
@@ -869,7 +848,10 @@ mod content {
             M: MapAccess<'de>,
         {
             let mut tag = None;
-            let mut vec = Vec::with_capacity(size_hint::cautious(map.size_hint()));
+            let mut vec = Vec::<(Content, Content)>::with_capacity(size_hint::cautious::<(
+                Content,
+                Content,
+            )>(map.size_hint()));
             while let Some(k) = try!(map.next_key_seed(TagOrContentVisitor::new(self.tag_name))) {
                 match k {
                     TagOrContent::Tag => {
@@ -886,10 +868,7 @@ mod content {
             }
             match tag {
                 None => Err(de::Error::missing_field(self.tag_name)),
-                Some(tag) => Ok(TaggedContent {
-                    tag: tag,
-                    content: Content::Map(vec),
-                }),
+                Some(tag) => Ok((tag, Content::Map(vec))),
             }
         }
     }
@@ -915,7 +894,7 @@ mod content {
         where
             D: Deserializer<'de>,
         {
-            deserializer.deserialize_str(self)
+            deserializer.deserialize_identifier(self)
         }
     }
 
@@ -926,6 +905,20 @@ mod content {
             write!(formatter, "{:?} or {:?}", self.tag, self.content)
         }
 
+        fn visit_u64<E>(self, field_index: u64) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            match field_index {
+                0 => Ok(TagOrContentField::Tag),
+                1 => Ok(TagOrContentField::Content),
+                _ => Err(de::Error::invalid_value(
+                    Unexpected::Unsigned(field_index),
+                    &self,
+                )),
+            }
+        }
+
         fn visit_str<E>(self, field: &str) -> Result<Self::Value, E>
         where
             E: de::Error,
@@ -938,6 +931,19 @@ mod content {
                 Err(de::Error::invalid_value(Unexpected::Str(field), &self))
             }
         }
+
+        fn visit_bytes<E>(self, field: &[u8]) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            if field == self.tag.as_bytes() {
+                Ok(TagOrContentField::Tag)
+            } else if field == self.content.as_bytes() {
+                Ok(TagOrContentField::Content)
+            } else {
+                Err(de::Error::invalid_value(Unexpected::Bytes(field), &self))
+            }
+        }
     }
 
     /// Used by generated code to deserialize an adjacently tagged enum when
@@ -963,7 +969,7 @@ mod content {
         where
             D: Deserializer<'de>,
         {
-            deserializer.deserialize_str(self)
+            deserializer.deserialize_identifier(self)
         }
     }
 
@@ -978,13 +984,31 @@ mod content {
             )
         }
 
+        fn visit_u64<E>(self, field_index: u64) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            match field_index {
+                0 => Ok(TagContentOtherField::Tag),
+                1 => Ok(TagContentOtherField::Content),
+                _ => Ok(TagContentOtherField::Other),
+            }
+        }
+
         fn visit_str<E>(self, field: &str) -> Result<Self::Value, E>
         where
             E: de::Error,
         {
-            if field == self.tag {
+            self.visit_bytes(field.as_bytes())
+        }
+
+        fn visit_bytes<E>(self, field: &[u8]) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            if field == self.tag.as_bytes() {
                 Ok(TagContentOtherField::Tag)
-            } else if field == self.content {
+            } else if field == self.content.as_bytes() {
                 Ok(TagContentOtherField::Content)
             } else {
                 Ok(TagContentOtherField::Other)
@@ -1457,7 +1481,7 @@ mod content {
         /// private API, don't use
         pub fn new(content: Content<'de>) -> Self {
             ContentDeserializer {
-                content: content,
+                content,
                 err: PhantomData,
             }
         }
@@ -1478,8 +1502,8 @@ mod content {
     {
         pub fn new(variant: Content<'de>, value: Option<Content<'de>>) -> EnumDeserializer<'de, E> {
             EnumDeserializer {
-                variant: variant,
-                value: value,
+                variant,
+                value,
                 err: PhantomData,
             }
         }
@@ -2135,8 +2159,8 @@ mod content {
             };
 
             visitor.visit_enum(EnumRefDeserializer {
-                variant: variant,
-                value: value,
+                variant,
+                value,
                 err: PhantomData,
             })
         }
@@ -2180,12 +2204,20 @@ mod content {
         /// private API, don't use
         pub fn new(content: &'a Content<'de>) -> Self {
             ContentRefDeserializer {
-                content: content,
+                content,
                 err: PhantomData,
             }
         }
     }
 
+    impl<'a, 'de: 'a, E> Copy for ContentRefDeserializer<'a, 'de, E> {}
+
+    impl<'a, 'de: 'a, E> Clone for ContentRefDeserializer<'a, 'de, E> {
+        fn clone(&self) -> Self {
+            *self
+        }
+    }
+
     struct EnumRefDeserializer<'a, 'de: 'a, E>
     where
         E: de::Error,
@@ -2481,8 +2513,8 @@ mod content {
         /// Not public API.
         pub fn new(type_name: &'a str, variant_name: &'a str) -> Self {
             InternallyTaggedUnitVisitor {
-                type_name: type_name,
-                variant_name: variant_name,
+                type_name,
+                variant_name,
             }
         }
     }
@@ -2526,8 +2558,8 @@ mod content {
         /// Not public API.
         pub fn new(type_name: &'a str, variant_name: &'a str) -> Self {
             UntaggedUnitVisitor {
-                type_name: type_name,
-                variant_name: variant_name,
+                type_name,
+                variant_name,
             }
         }
     }
@@ -2731,11 +2763,7 @@ where
     where
         V: Visitor<'de>,
     {
-        visitor.visit_map(FlatInternallyTaggedAccess {
-            iter: self.0.iter_mut(),
-            pending: None,
-            _marker: PhantomData,
-        })
+        self.deserialize_map(visitor)
     }
 
     fn deserialize_enum<V>(
@@ -2747,17 +2775,8 @@ where
     where
         V: Visitor<'de>,
     {
-        for item in self.0.iter_mut() {
-            // items in the vector are nulled out when used.  So we can only use
-            // an item if it's still filled in and if the field is one we care
-            // about.
-            let use_item = match *item {
-                None => false,
-                Some((ref c, _)) => c.as_str().map_or(false, |x| variants.contains(&x)),
-            };
-
-            if use_item {
-                let (key, value) = item.take().unwrap();
+        for entry in self.0 {
+            if let Some((key, value)) = flat_map_take_entry(entry, variants) {
                 return visitor.visit_enum(EnumDeserializer::new(key, Some(value)));
             }
         }
@@ -2772,7 +2791,11 @@ where
     where
         V: Visitor<'de>,
     {
-        visitor.visit_map(FlatMapAccess::new(self.0.iter()))
+        visitor.visit_map(FlatMapAccess {
+            iter: self.0.iter(),
+            pending_content: None,
+            _marker: PhantomData,
+        })
     }
 
     fn deserialize_struct<V>(
@@ -2784,7 +2807,12 @@ where
     where
         V: Visitor<'de>,
     {
-        visitor.visit_map(FlatStructAccess::new(self.0.iter_mut(), fields))
+        visitor.visit_map(FlatStructAccess {
+            iter: self.0.iter_mut(),
+            pending_content: None,
+            fields,
+            _marker: PhantomData,
+        })
     }
 
     fn deserialize_newtype_struct<V>(self, _name: &str, visitor: V) -> Result<V::Value, Self::Error>
@@ -2811,6 +2839,13 @@ where
         visitor.visit_unit()
     }
 
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_unit()
+    }
+
     forward_to_deserialize_other! {
         deserialize_bool()
         deserialize_i8()
@@ -2833,30 +2868,16 @@ where
         deserialize_tuple(usize)
         deserialize_tuple_struct(&'static str, usize)
         deserialize_identifier()
-        deserialize_ignored_any()
     }
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-pub struct FlatMapAccess<'a, 'de: 'a, E> {
+struct FlatMapAccess<'a, 'de: 'a, E> {
     iter: slice::Iter<'a, Option<(Content<'de>, Content<'de>)>>,
     pending_content: Option<&'a Content<'de>>,
     _marker: PhantomData<E>,
 }
 
-#[cfg(any(feature = "std", feature = "alloc"))]
-impl<'a, 'de, E> FlatMapAccess<'a, 'de, E> {
-    fn new(
-        iter: slice::Iter<'a, Option<(Content<'de>, Content<'de>)>>,
-    ) -> FlatMapAccess<'a, 'de, E> {
-        FlatMapAccess {
-            iter: iter,
-            pending_content: None,
-            _marker: PhantomData,
-        }
-    }
-}
-
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, 'de, E> MapAccess<'de> for FlatMapAccess<'a, 'de, E>
 where
@@ -2871,6 +2892,10 @@ where
         for item in &mut self.iter {
             // Items in the vector are nulled out when used by a struct.
             if let Some((ref key, ref content)) = *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.
                 self.pending_content = Some(content);
                 return seed.deserialize(ContentRefDeserializer::new(key)).map(Some);
             }
@@ -2890,28 +2915,13 @@ where
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-pub struct FlatStructAccess<'a, 'de: 'a, E> {
+struct FlatStructAccess<'a, 'de: 'a, E> {
     iter: slice::IterMut<'a, Option<(Content<'de>, Content<'de>)>>,
     pending_content: Option<Content<'de>>,
     fields: &'static [&'static str],
     _marker: PhantomData<E>,
 }
 
-#[cfg(any(feature = "std", feature = "alloc"))]
-impl<'a, 'de, E> FlatStructAccess<'a, 'de, E> {
-    fn new(
-        iter: slice::IterMut<'a, Option<(Content<'de>, Content<'de>)>>,
-        fields: &'static [&'static str],
-    ) -> FlatStructAccess<'a, 'de, E> {
-        FlatStructAccess {
-            iter: iter,
-            pending_content: None,
-            fields: fields,
-            _marker: PhantomData,
-        }
-    }
-}
-
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'a, 'de, E> MapAccess<'de> for FlatStructAccess<'a, 'de, E>
 where
@@ -2923,17 +2933,8 @@ where
     where
         T: DeserializeSeed<'de>,
     {
-        while let Some(item) = self.iter.next() {
-            // items in the vector are nulled out when used.  So we can only use
-            // an item if it's still filled in and if the field is one we care
-            // 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(false, |key| self.fields.contains(&key)),
-            };
-
-            if use_item {
-                let (key, content) = item.take().unwrap();
+        for entry in self.iter.by_ref() {
+            if let Some((key, content)) = flat_map_take_entry(entry, self.fields) {
                 self.pending_content = Some(content);
                 return seed.deserialize(ContentDeserializer::new(key)).map(Some);
             }
@@ -2952,44 +2953,24 @@ where
     }
 }
 
+/// Claims one key-value pair from a FlatMapDeserializer's field buffer if the
+/// field name matches any of the recognized ones.
 #[cfg(any(feature = "std", feature = "alloc"))]
-pub struct FlatInternallyTaggedAccess<'a, 'de: 'a, E> {
-    iter: slice::IterMut<'a, Option<(Content<'de>, Content<'de>)>>,
-    pending: Option<&'a Content<'de>>,
-    _marker: PhantomData<E>,
-}
+fn flat_map_take_entry<'de>(
+    entry: &mut Option<(Content<'de>, Content<'de>)>,
+    recognized: &[&str],
+) -> Option<(Content<'de>, Content<'de>)> {
+    // Entries in the FlatMapDeserializer buffer are nulled out as they get
+    // claimed for deserialization. We only use an entry if it is still present
+    // and if the field is one recognized by the current data structure.
+    let is_recognized = match entry {
+        None => false,
+        Some((k, _v)) => k.as_str().map_or(false, |name| recognized.contains(&name)),
+    };
 
-#[cfg(any(feature = "std", feature = "alloc"))]
-impl<'a, 'de, E> MapAccess<'de> for FlatInternallyTaggedAccess<'a, 'de, E>
-where
-    E: Error,
-{
-    type Error = E;
-
-    fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
-    where
-        T: DeserializeSeed<'de>,
-    {
-        for item in &mut self.iter {
-            if let Some((ref key, ref content)) = *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.
-                self.pending = Some(content);
-                return seed.deserialize(ContentRefDeserializer::new(key)).map(Some);
-            }
-        }
-        Ok(None)
-    }
-
-    fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value, Self::Error>
-    where
-        T: DeserializeSeed<'de>,
-    {
-        match self.pending.take() {
-            Some(value) => seed.deserialize(ContentRefDeserializer::new(value)),
-            None => panic!("value is missing"),
-        }
+    if is_recognized {
+        entry.take()
+    } else {
+        None
     }
 }

serde/src/private/ser.rs

@@ -27,10 +27,10 @@ where
     T: Serialize,
 {
     value.serialize(TaggedSerializer {
-        type_ident: type_ident,
-        variant_ident: variant_ident,
-        tag: tag,
-        variant_name: variant_name,
+        type_ident,
+        variant_ident,
+        tag,
+        variant_name,
         delegate: serializer,
     })
 }
@@ -350,8 +350,8 @@ mod content {
     impl<M> SerializeTupleVariantAsMapValue<M> {
         pub fn new(map: M, name: &'static str, len: usize) -> Self {
             SerializeTupleVariantAsMapValue {
-                map: map,
-                name: name,
+                map,
+                name,
                 fields: Vec::with_capacity(len),
             }
         }
@@ -390,8 +390,8 @@ mod content {
     impl<M> SerializeStructVariantAsMapValue<M> {
         pub fn new(map: M, name: &'static str, len: usize) -> Self {
             SerializeStructVariantAsMapValue {
-                map: map,
-                name: name,
+                map,
+                name,
                 fields: Vec::with_capacity(len),
             }
         }
@@ -711,7 +711,7 @@ mod content {
             len: usize,
         ) -> Result<Self::SerializeTupleStruct, E> {
             Ok(SerializeTupleStruct {
-                name: name,
+                name,
                 fields: Vec::with_capacity(len),
                 error: PhantomData,
             })
@@ -725,9 +725,9 @@ mod content {
             len: usize,
         ) -> Result<Self::SerializeTupleVariant, E> {
             Ok(SerializeTupleVariant {
-                name: name,
-                variant_index: variant_index,
-                variant: variant,
+                name,
+                variant_index,
+                variant,
                 fields: Vec::with_capacity(len),
                 error: PhantomData,
             })
@@ -747,7 +747,7 @@ mod content {
             len: usize,
         ) -> Result<Self::SerializeStruct, E> {
             Ok(SerializeStruct {
-                name: name,
+                name,
                 fields: Vec::with_capacity(len),
                 error: PhantomData,
             })
@@ -761,9 +761,9 @@ mod content {
             len: usize,
         ) -> Result<Self::SerializeStructVariant, E> {
             Ok(SerializeStructVariant {
-                name: name,
-                variant_index: variant_index,
-                variant: variant,
+                name,
+                variant_index,
+                variant,
                 fields: Vec::with_capacity(len),
                 error: PhantomData,
             })
@@ -1273,8 +1273,8 @@ where
 {
     fn new(map: &'a mut M, name: &'static str) -> FlatMapSerializeStructVariantAsMapValue<'a, M> {
         FlatMapSerializeStructVariantAsMapValue {
-            map: map,
-            name: name,
+            map,
+            name,
             fields: Vec::new(),
         }
     }

serde/src/private/size_hint.rs

@@ -8,9 +8,17 @@ where
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-#[inline]
-pub fn cautious(hint: Option<usize>) -> usize {
-    cmp::min(hint.unwrap_or(0), 4096)
+pub fn cautious<Element>(hint: Option<usize>) -> usize {
+    const MAX_PREALLOC_BYTES: usize = 1024 * 1024;
+
+    if mem::size_of::<Element>() == 0 {
+        0
+    } else {
+        cmp::min(
+            hint.unwrap_or(0),
+            MAX_PREALLOC_BYTES / mem::size_of::<Element>(),
+        )
+    }
 }
 
 fn helper(bounds: (usize, Option<usize>)) -> Option<usize> {

serde/src/ser/fmt.rs

@@ -17,8 +17,9 @@ macro_rules! fmt_primitives {
     };
 }
 
-/// ```edition2018
-/// use serde::Serialize;
+/// ```edition2021
+/// use serde::ser::Serialize;
+/// use serde_derive::Serialize;
 /// use std::fmt::{self, Display};
 ///
 /// #[derive(Serialize)]

serde/src/ser/impls.rs

@@ -257,6 +257,23 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
+impl<Idx> Serialize for RangeFrom<Idx>
+where
+    Idx: Serialize,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        use super::SerializeStruct;
+        let mut state = try!(serializer.serialize_struct("RangeFrom", 1));
+        try!(state.serialize_field("start", &self.start));
+        state.end()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 #[cfg(not(no_range_inclusive))]
 impl<Idx> Serialize for RangeInclusive<Idx>
 where
@@ -276,6 +293,23 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
+impl<Idx> Serialize for RangeTo<Idx>
+where
+    Idx: Serialize,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        use super::SerializeStruct;
+        let mut state = try!(serializer.serialize_struct("RangeTo", 1));
+        try!(state.serialize_field("end", &self.end));
+        state.end()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 #[cfg(any(not(no_ops_bound), all(feature = "std", not(no_collections_bound))))]
 impl<T> Serialize for Bound<T>
 where
@@ -713,7 +747,7 @@ impl Serialize for net::IpAddr {
 }
 
 #[cfg(feature = "std")]
-const DEC_DIGITS_LUT: &'static [u8] = b"\
+const DEC_DIGITS_LUT: &[u8] = b"\
       0001020304050607080910111213141516171819\
       2021222324252627282930313233343536373839\
       4041424344454647484950515253545556575859\

serde/src/ser/impossible.rs

@@ -15,7 +15,7 @@ use ser::{
 /// [`SerializeTuple`], [`SerializeTupleStruct`], [`SerializeTupleVariant`],
 /// [`SerializeMap`], [`SerializeStruct`], and [`SerializeStructVariant`].
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use serde::ser::{Serializer, Impossible};
 /// # use serde::__private::doc::Error;
 /// #

serde/src/ser/mod.rs

@@ -149,7 +149,7 @@ macro_rules! declare_error_trait {
             /// For example, a filesystem [`Path`] may refuse to serialize
             /// itself if it contains invalid UTF-8 data.
             ///
-            /// ```edition2018
+            /// ```edition2021
             /// # struct Path;
             /// #
             /// # impl Path {
@@ -221,7 +221,7 @@ pub trait Serialize {
     /// See the [Implementing `Serialize`] section of the manual for more
     /// information about how to implement this method.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::ser::{Serialize, SerializeStruct, Serializer};
     ///
     /// struct Person {
@@ -388,7 +388,7 @@ pub trait Serializer: Sized {
 
     /// Serialize a `bool` value.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -410,7 +410,7 @@ pub trait Serializer: Sized {
     /// reasonable implementation would be to cast the value to `i64` and
     /// forward to `serialize_i64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -432,7 +432,7 @@ pub trait Serializer: Sized {
     /// reasonable implementation would be to cast the value to `i64` and
     /// forward to `serialize_i64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -454,7 +454,7 @@ pub trait Serializer: Sized {
     /// reasonable implementation would be to cast the value to `i64` and
     /// forward to `serialize_i64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -472,7 +472,7 @@ pub trait Serializer: Sized {
 
     /// Serialize an `i64` value.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -491,7 +491,7 @@ pub trait Serializer: Sized {
     serde_if_integer128! {
         /// Serialize an `i128` value.
         ///
-        /// ```edition2018
+        /// ```edition2021
         /// # use serde::Serializer;
         /// #
         /// # serde::__private_serialize!();
@@ -520,7 +520,7 @@ pub trait Serializer: Sized {
     /// reasonable implementation would be to cast the value to `u64` and
     /// forward to `serialize_u64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -542,7 +542,7 @@ pub trait Serializer: Sized {
     /// reasonable implementation would be to cast the value to `u64` and
     /// forward to `serialize_u64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -564,7 +564,7 @@ pub trait Serializer: Sized {
     /// reasonable implementation would be to cast the value to `u64` and
     /// forward to `serialize_u64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -582,7 +582,7 @@ pub trait Serializer: Sized {
 
     /// Serialize a `u64` value.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -601,7 +601,7 @@ pub trait Serializer: Sized {
     serde_if_integer128! {
         /// Serialize a `u128` value.
         ///
-        /// ```edition2018
+        /// ```edition2021
         /// # use serde::Serializer;
         /// #
         /// # serde::__private_serialize!();
@@ -630,7 +630,7 @@ pub trait Serializer: Sized {
     /// reasonable implementation would be to cast the value to `f64` and
     /// forward to `serialize_f64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -648,7 +648,7 @@ pub trait Serializer: Sized {
 
     /// Serialize an `f64` value.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -669,7 +669,7 @@ pub trait Serializer: Sized {
     /// If the format does not support characters, it is reasonable to serialize
     /// it as a single element `str` or a `u32`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -687,7 +687,7 @@ pub trait Serializer: Sized {
 
     /// Serialize a `&str`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -711,7 +711,7 @@ pub trait Serializer: Sized {
     /// `serialize_seq`. If forwarded, the implementation looks usually just
     /// like this:
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::ser::{Serializer, SerializeSeq};
     /// # use serde::__private::doc::Error;
     /// #
@@ -740,7 +740,7 @@ pub trait Serializer: Sized {
 
     /// Serialize a [`None`] value.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::{Serialize, Serializer};
     /// #
     /// # enum Option<T> {
@@ -773,7 +773,7 @@ pub trait Serializer: Sized {
 
     /// Serialize a [`Some(T)`] value.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::{Serialize, Serializer};
     /// #
     /// # enum Option<T> {
@@ -808,7 +808,7 @@ pub trait Serializer: Sized {
 
     /// Serialize a `()` value.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde::Serializer;
     /// #
     /// # serde::__private_serialize!();
@@ -828,7 +828,7 @@ pub trait Serializer: Sized {
     ///
     /// A reasonable implementation would be to forward to `serialize_unit`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::{Serialize, Serializer};
     ///
     /// struct Nothing;
@@ -850,7 +850,7 @@ pub trait Serializer: Sized {
     /// this variant within the enum, and the `variant` is the name of the
     /// variant.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::{Serialize, Serializer};
     ///
     /// enum E {
@@ -883,7 +883,7 @@ pub trait Serializer: Sized {
     /// wrappers around the data they contain. A reasonable implementation would
     /// be to forward to `value.serialize(self)`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::{Serialize, Serializer};
     ///
     /// struct Millimeters(u8);
@@ -911,7 +911,7 @@ pub trait Serializer: Sized {
     /// this variant within the enum, and the `variant` is the name of the
     /// variant. The `value` is the data contained within this newtype variant.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::{Serialize, Serializer};
     ///
     /// enum E {
@@ -949,7 +949,7 @@ pub trait Serializer: Sized {
     /// not be computable before the sequence is iterated. Some serializers only
     /// support sequences whose length is known up front.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use std::marker::PhantomData;
     /// #
     /// # struct Vec<T>(PhantomData<T>);
@@ -962,14 +962,14 @@ pub trait Serializer: Sized {
     /// #
     /// # impl<'a, T> IntoIterator for &'a Vec<T> {
     /// #     type Item = &'a T;
-    /// #     type IntoIter = Box<Iterator<Item = &'a T>>;
+    /// #     type IntoIter = Box<dyn Iterator<Item = &'a T>>;
     /// #
     /// #     fn into_iter(self) -> Self::IntoIter {
     /// #         unimplemented!()
     /// #     }
     /// # }
     /// #
-    /// use serde::ser::{Serialize, Serializer, SerializeSeq};
+    /// use serde::ser::{Serialize, SerializeSeq, Serializer};
     ///
     /// impl<T> Serialize for Vec<T>
     /// where
@@ -994,8 +994,8 @@ pub trait Serializer: Sized {
     /// This call must be followed by zero or more calls to `serialize_element`,
     /// then a call to `end`.
     ///
-    /// ```edition2018
-    /// use serde::ser::{Serialize, Serializer, SerializeTuple};
+    /// ```edition2021
+    /// use serde::ser::{Serialize, SerializeTuple, Serializer};
     ///
     /// # mod fool {
     /// #     trait Serialize {}
@@ -1024,7 +1024,7 @@ pub trait Serializer: Sized {
     /// }
     /// ```
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::ser::{Serialize, SerializeTuple, Serializer};
     ///
     /// const VRAM_SIZE: usize = 386;
@@ -1052,7 +1052,7 @@ pub trait Serializer: Sized {
     /// The `name` is the name of the tuple struct and the `len` is the number
     /// of data fields that will be serialized.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
     ///
     /// struct Rgb(u8, u8, u8);
@@ -1084,7 +1084,7 @@ pub trait Serializer: Sized {
     /// this variant within the enum, the `variant` is the name of the variant,
     /// and the `len` is the number of data fields that will be serialized.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::ser::{Serialize, SerializeTupleVariant, Serializer};
     ///
     /// enum E {
@@ -1130,7 +1130,7 @@ pub trait Serializer: Sized {
     /// be computable before the map is iterated. Some serializers only support
     /// maps whose length is known up front.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use std::marker::PhantomData;
     /// #
     /// # struct HashMap<K, V>(PhantomData<K>, PhantomData<V>);
@@ -1143,14 +1143,14 @@ pub trait Serializer: Sized {
     /// #
     /// # impl<'a, K, V> IntoIterator for &'a HashMap<K, V> {
     /// #     type Item = (&'a K, &'a V);
-    /// #     type IntoIter = Box<Iterator<Item = (&'a K, &'a V)>>;
+    /// #     type IntoIter = Box<dyn Iterator<Item = (&'a K, &'a V)>>;
     /// #
     /// #     fn into_iter(self) -> Self::IntoIter {
     /// #         unimplemented!()
     /// #     }
     /// # }
     /// #
-    /// use serde::ser::{Serialize, Serializer, SerializeMap};
+    /// use serde::ser::{Serialize, SerializeMap, Serializer};
     ///
     /// impl<K, V> Serialize for HashMap<K, V>
     /// where
@@ -1178,7 +1178,7 @@ pub trait Serializer: Sized {
     /// The `name` is the name of the struct and the `len` is the number of
     /// data fields that will be serialized.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::ser::{Serialize, SerializeStruct, Serializer};
     ///
     /// struct Rgb {
@@ -1214,7 +1214,7 @@ pub trait Serializer: Sized {
     /// this variant within the enum, the `variant` is the name of the variant,
     /// and the `len` is the number of data fields that will be serialized.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::ser::{Serialize, SerializeStructVariant, Serializer};
     ///
     /// enum E {
@@ -1256,7 +1256,7 @@ pub trait Serializer: Sized {
     /// using [`serialize_seq`]. Implementors should not need to override this
     /// method.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::{Serialize, Serializer};
     ///
     /// struct SecretlyOneHigher {
@@ -1304,7 +1304,7 @@ pub trait Serializer: Sized {
     /// using [`serialize_map`]. Implementors should not need to override this
     /// method.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// use serde::{Serialize, Serializer};
     /// use std::collections::BTreeSet;
     ///
@@ -1355,7 +1355,7 @@ pub trait Serializer: Sized {
     /// delegates to [`serialize_str`]. Serializers are encouraged to provide a
     /// more efficient implementation if possible.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # struct DateTime;
     /// #
     /// # impl DateTime {
@@ -1370,9 +1370,7 @@ pub trait Serializer: Sized {
     ///     where
     ///         S: Serializer,
     ///     {
-    ///         serializer.collect_str(&format_args!("{:?}{:?}",
-    ///                                              self.naive_local(),
-    ///                                              self.offset()))
+    ///         serializer.collect_str(&format_args!("{:?}{:?}", self.naive_local(), self.offset()))
     ///     }
     /// }
     /// ```
@@ -1393,7 +1391,7 @@ pub trait Serializer: Sized {
     /// of this method. If no more sensible behavior is possible, the
     /// implementation is expected to return an error.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # struct DateTime;
     /// #
     /// # impl DateTime {
@@ -1408,9 +1406,7 @@ pub trait Serializer: Sized {
     ///     where
     ///         S: Serializer,
     ///     {
-    ///         serializer.collect_str(&format_args!("{:?}{:?}",
-    ///                                              self.naive_local(),
-    ///                                              self.offset()))
+    ///         serializer.collect_str(&format_args!("{:?}{:?}", self.naive_local(), self.offset()))
     ///     }
     /// }
     /// ```
@@ -1428,7 +1424,7 @@ pub trait Serializer: Sized {
     /// human-readable one and binary formats like Postcard will prefer the
     /// compact one.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use std::fmt::{self, Display};
     /// #
     /// # struct Timestamp;
@@ -1477,7 +1473,7 @@ pub trait Serializer: Sized {
 ///
 /// # Example use
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use std::marker::PhantomData;
 /// #
 /// # struct Vec<T>(PhantomData<T>);
@@ -1490,13 +1486,13 @@ pub trait Serializer: Sized {
 /// #
 /// # impl<'a, T> IntoIterator for &'a Vec<T> {
 /// #     type Item = &'a T;
-/// #     type IntoIter = Box<Iterator<Item = &'a T>>;
+/// #     type IntoIter = Box<dyn Iterator<Item = &'a T>>;
 /// #     fn into_iter(self) -> Self::IntoIter {
 /// #         unimplemented!()
 /// #     }
 /// # }
 /// #
-/// use serde::ser::{Serialize, Serializer, SerializeSeq};
+/// use serde::ser::{Serialize, SerializeSeq, Serializer};
 ///
 /// impl<T> Serialize for Vec<T>
 /// where
@@ -1541,8 +1537,8 @@ pub trait SerializeSeq {
 ///
 /// # Example use
 ///
-/// ```edition2018
-/// use serde::ser::{Serialize, Serializer, SerializeTuple};
+/// ```edition2021
+/// use serde::ser::{Serialize, SerializeTuple, Serializer};
 ///
 /// # mod fool {
 /// #     trait Serialize {}
@@ -1571,7 +1567,7 @@ pub trait SerializeSeq {
 /// }
 /// ```
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use std::marker::PhantomData;
 /// #
 /// # struct Array<T>(PhantomData<T>);
@@ -1584,13 +1580,13 @@ pub trait SerializeSeq {
 /// #
 /// # impl<'a, T> IntoIterator for &'a Array<T> {
 /// #     type Item = &'a T;
-/// #     type IntoIter = Box<Iterator<Item = &'a T>>;
+/// #     type IntoIter = Box<dyn Iterator<Item = &'a T>>;
 /// #     fn into_iter(self) -> Self::IntoIter {
 /// #         unimplemented!()
 /// #     }
 /// # }
 /// #
-/// use serde::ser::{Serialize, Serializer, SerializeTuple};
+/// use serde::ser::{Serialize, SerializeTuple, Serializer};
 ///
 /// # mod fool {
 /// #     trait Serialize {}
@@ -1641,7 +1637,7 @@ pub trait SerializeTuple {
 ///
 /// # Example use
 ///
-/// ```edition2018
+/// ```edition2021
 /// use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
 ///
 /// struct Rgb(u8, u8, u8);
@@ -1686,7 +1682,7 @@ pub trait SerializeTupleStruct {
 ///
 /// # Example use
 ///
-/// ```edition2018
+/// ```edition2021
 /// use serde::ser::{Serialize, SerializeTupleVariant, Serializer};
 ///
 /// enum E {
@@ -1744,7 +1740,7 @@ pub trait SerializeTupleVariant {
 ///
 /// # Example use
 ///
-/// ```edition2018
+/// ```edition2021
 /// # use std::marker::PhantomData;
 /// #
 /// # struct HashMap<K, V>(PhantomData<K>, PhantomData<V>);
@@ -1757,14 +1753,14 @@ pub trait SerializeTupleVariant {
 /// #
 /// # impl<'a, K, V> IntoIterator for &'a HashMap<K, V> {
 /// #     type Item = (&'a K, &'a V);
-/// #     type IntoIter = Box<Iterator<Item = (&'a K, &'a V)>>;
+/// #     type IntoIter = Box<dyn Iterator<Item = (&'a K, &'a V)>>;
 /// #
 /// #     fn into_iter(self) -> Self::IntoIter {
 /// #         unimplemented!()
 /// #     }
 /// # }
 /// #
-/// use serde::ser::{Serialize, Serializer, SerializeMap};
+/// use serde::ser::{Serialize, SerializeMap, Serializer};
 ///
 /// impl<K, V> Serialize for HashMap<K, V>
 /// where
@@ -1855,7 +1851,7 @@ pub trait SerializeMap {
 ///
 /// # Example use
 ///
-/// ```edition2018
+/// ```edition2021
 /// use serde::ser::{Serialize, SerializeStruct, Serializer};
 ///
 /// struct Rgb {
@@ -1915,7 +1911,7 @@ pub trait SerializeStruct {
 ///
 /// # Example use
 ///
-/// ```edition2018
+/// ```edition2021
 /// use serde::ser::{Serialize, SerializeStructVariant, Serializer};
 ///
 /// enum E {

serde/src/std_error.rs

@@ -9,7 +9,7 @@ use lib::{Debug, Display};
 /// generally provide their error types with a `std::error::Error` impl
 /// directly:
 ///
-/// ```edition2018
+/// ```edition2021
 /// #[derive(Debug)]
 /// struct MySerError {...}
 ///
@@ -29,7 +29,7 @@ use lib::{Debug, Display};
 /// std = ["serde/std"]
 /// ```
 ///
-/// ```edition2018
+/// ```edition2021
 /// #[cfg(feature = "std")]
 /// impl std::error::Error for MySerError {}
 /// ```
@@ -37,7 +37,7 @@ use lib::{Debug, Display};
 /// ... or else provide the std Error impl unconditionally via Serde's
 /// re-export:
 ///
-/// ```edition2018
+/// ```edition2021
 /// impl serde::ser::StdError for MySerError {}
 /// ```
 pub trait Error: Debug + Display {

serde_derive/.clippy.toml

@@ -1 +0,0 @@
-msrv = "1.31.0"

serde_derive/Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "serde_derive"
-version = "1.0.157" # remember to update html_root_url
+version = "1.0.169" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
-categories = ["no-std"]
+categories = ["no-std", "no-std::no-alloc"]
 description = "Macros 1.1 implementation of #[derive(Serialize, Deserialize)]"
 documentation = "https://serde.rs/derive.html"
 homepage = "https://serde.rs"
@@ -24,7 +24,7 @@ proc-macro = true
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = "2.0"
+syn = "2.0.24"
 
 [dev-dependencies]
 serde = { version = "1.0", path = "../serde" }

serde_derive/build.rs

@@ -1,38 +0,0 @@
-use std::env;
-use std::process::Command;
-use std::str;
-
-// 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() {
-    println!("cargo:rerun-if-changed=build.rs");
-
-    let minor = match rustc_minor_version() {
-        Some(minor) => minor,
-        None => return,
-    };
-
-    // Underscore const names stabilized in Rust 1.37:
-    // https://blog.rust-lang.org/2019/08/15/Rust-1.37.0.html#using-unnamed-const-items-for-macros
-    if minor < 37 {
-        println!("cargo:rustc-cfg=no_underscore_consts");
-    }
-
-    // The ptr::addr_of! macro stabilized in Rust 1.51:
-    // https://blog.rust-lang.org/2021/03/25/Rust-1.51.0.html#stabilized-apis
-    if minor < 51 {
-        println!("cargo:rustc-cfg=no_ptr_addr_of");
-    }
-}
-
-fn rustc_minor_version() -> Option<u32> {
-    let rustc = env::var_os("RUSTC")?;
-    let output = Command::new(rustc).arg("--version").output().ok()?;
-    let version = str::from_utf8(&output.stdout).ok()?;
-    let mut pieces = version.split('.');
-    if pieces.next() != Some("rustc 1") {
-        return None;
-    }
-    pieces.next()?.parse().ok()
-}

serde_derive/src/bound.rs

@@ -259,7 +259,7 @@ pub fn with_bound(
     };
     match &cont.data {
         Data::Enum(variants) => {
-            for variant in variants.iter() {
+            for variant in variants {
                 let relevant_fields = variant
                     .fields
                     .iter()

serde_derive/src/de.rs

@@ -15,9 +15,7 @@ use this;
 use std::collections::BTreeSet;
 use std::ptr;
 
-pub fn expand_derive_deserialize(
-    input: &mut syn::DeriveInput,
-) -> Result<TokenStream, Vec<syn::Error>> {
+pub fn expand_derive_deserialize(input: &mut syn::DeriveInput) -> syn::Result<TokenStream> {
     replace_receiver(input);
 
     let ctxt = Ctxt::new();
@@ -69,8 +67,6 @@ pub fn expand_derive_deserialize(
 
     Ok(dummy::wrap_in_const(
         cont.attrs.custom_serde_path(),
-        "DESERIALIZE",
-        ident,
         impl_block,
     ))
 }
@@ -291,10 +287,10 @@ fn deserialize_body(cont: &Container, params: &Parameters) -> Fragment {
         match &cont.data {
             Data::Enum(variants) => deserialize_enum(params, variants, &cont.attrs),
             Data::Struct(Style::Struct, fields) => {
-                deserialize_struct(None, params, fields, &cont.attrs, None, &Untagged::No)
+                deserialize_struct(params, fields, &cont.attrs, StructForm::Struct)
             }
             Data::Struct(Style::Tuple, fields) | Data::Struct(Style::Newtype, fields) => {
-                deserialize_tuple(None, params, fields, &cont.attrs, None)
+                deserialize_tuple(params, fields, &cont.attrs, TupleForm::Tuple)
             }
             Data::Struct(Style::Unit, _) => deserialize_unit_struct(params, &cont.attrs),
         }
@@ -419,6 +415,7 @@ fn deserialize_unit_struct(params: &Parameters, cattrs: &attr::Container) -> Fra
     let expecting = cattrs.expecting().unwrap_or(&expecting);
 
     quote_block! {
+        #[doc(hidden)]
         struct __Visitor;
 
         impl<'de> _serde::de::Visitor<'de> for __Visitor {
@@ -441,21 +438,34 @@ fn deserialize_unit_struct(params: &Parameters, cattrs: &attr::Container) -> Fra
     }
 }
 
+enum TupleForm<'a> {
+    Tuple,
+    /// Contains a variant name
+    ExternallyTagged(&'a syn::Ident),
+    /// Contains a variant name and an intermediate deserializer from which actual
+    /// deserialization will be performed
+    Untagged(&'a syn::Ident, TokenStream),
+}
+
 fn deserialize_tuple(
-    variant_ident: Option<&syn::Ident>,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<TokenStream>,
+    form: TupleForm,
 ) -> Fragment {
+    assert!(!cattrs.has_flatten());
+
+    let field_count = fields
+        .iter()
+        .filter(|field| !field.attrs.skip_deserializing())
+        .count();
+
     let this_type = &params.this_type;
     let this_value = &params.this_value;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
         split_with_de_lifetime(params);
     let delife = params.borrowed.de_lifetime();
 
-    assert!(!cattrs.has_flatten());
-
     // If there are getters (implying private fields), construct the local type
     // and use an `Into` conversion to get the remote type. If there are no
     // getters then construct the target type directly.
@@ -466,23 +476,27 @@ fn deserialize_tuple(
         quote!(#this_value)
     };
 
-    let is_enum = variant_ident.is_some();
-    let type_path = match variant_ident {
-        Some(variant_ident) => quote!(#construct::#variant_ident),
-        None => construct,
+    let type_path = match form {
+        TupleForm::Tuple => construct,
+        TupleForm::ExternallyTagged(variant_ident) | TupleForm::Untagged(variant_ident, _) => {
+            quote!(#construct::#variant_ident)
+        }
     };
-    let expecting = match variant_ident {
-        Some(variant_ident) => format!("tuple variant {}::{}", params.type_name(), variant_ident),
-        None => format!("tuple struct {}", params.type_name()),
+    let expecting = match form {
+        TupleForm::Tuple => format!("tuple struct {}", params.type_name()),
+        TupleForm::ExternallyTagged(variant_ident) | TupleForm::Untagged(variant_ident, _) => {
+            format!("tuple variant {}::{}", params.type_name(), variant_ident)
+        }
     };
     let expecting = cattrs.expecting().unwrap_or(&expecting);
 
     let nfields = fields.len();
 
-    let visit_newtype_struct = if !is_enum && nfields == 1 {
-        Some(deserialize_newtype_struct(&type_path, params, &fields[0]))
-    } else {
-        None
+    let visit_newtype_struct = match form {
+        TupleForm::Tuple if nfields == 1 => {
+            Some(deserialize_newtype_struct(&type_path, params, &fields[0]))
+        }
+        _ => None,
     };
 
     let visit_seq = Stmts(deserialize_seq(
@@ -495,26 +509,35 @@ fn deserialize_tuple(
             lifetime: _serde::__private::PhantomData,
         }
     };
-    let dispatch = if let Some(deserializer) = deserializer {
-        quote!(_serde::Deserializer::deserialize_tuple(#deserializer, #nfields, #visitor_expr))
-    } else if is_enum {
-        quote!(_serde::de::VariantAccess::tuple_variant(__variant, #nfields, #visitor_expr))
-    } else if nfields == 1 {
-        let type_name = cattrs.name().deserialize_name();
-        quote!(_serde::Deserializer::deserialize_newtype_struct(__deserializer, #type_name, #visitor_expr))
-    } else {
-        let type_name = cattrs.name().deserialize_name();
-        quote!(_serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #nfields, #visitor_expr))
+    let dispatch = match form {
+        TupleForm::Tuple if nfields == 1 => {
+            let type_name = cattrs.name().deserialize_name();
+            quote! {
+                _serde::Deserializer::deserialize_newtype_struct(__deserializer, #type_name, #visitor_expr)
+            }
+        }
+        TupleForm::Tuple => {
+            let type_name = cattrs.name().deserialize_name();
+            quote! {
+                _serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #field_count, #visitor_expr)
+            }
+        }
+        TupleForm::ExternallyTagged(_) => quote! {
+            _serde::de::VariantAccess::tuple_variant(__variant, #field_count, #visitor_expr)
+        },
+        TupleForm::Untagged(_, deserializer) => quote! {
+            _serde::Deserializer::deserialize_tuple(#deserializer, #field_count, #visitor_expr)
+        },
     };
 
-    let all_skipped = fields.iter().all(|field| field.attrs.skip_deserializing());
-    let visitor_var = if all_skipped {
+    let visitor_var = if field_count == 0 {
         quote!(_)
     } else {
         quote!(mut __seq)
     };
 
     quote_block! {
+        #[doc(hidden)]
         struct __Visitor #de_impl_generics #where_clause {
             marker: _serde::__private::PhantomData<#this_type #ty_generics>,
             lifetime: _serde::__private::PhantomData<&#delife ()>,
@@ -550,13 +573,18 @@ fn deserialize_tuple_in_place(
     cattrs: &attr::Container,
     deserializer: Option<TokenStream>,
 ) -> Fragment {
+    assert!(!cattrs.has_flatten());
+
+    let field_count = fields
+        .iter()
+        .filter(|field| !field.attrs.skip_deserializing())
+        .count();
+
     let this_type = &params.this_type;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
         split_with_de_lifetime(params);
     let delife = params.borrowed.de_lifetime();
 
-    assert!(!cattrs.has_flatten());
-
     let is_enum = variant_ident.is_some();
     let expecting = match variant_ident {
         Some(variant_ident) => format!("tuple variant {}::{}", params.type_name(), variant_ident),
@@ -582,19 +610,18 @@ fn deserialize_tuple_in_place(
     };
 
     let dispatch = if let Some(deserializer) = deserializer {
-        quote!(_serde::Deserializer::deserialize_tuple(#deserializer, #nfields, #visitor_expr))
+        quote!(_serde::Deserializer::deserialize_tuple(#deserializer, #field_count, #visitor_expr))
     } else if is_enum {
-        quote!(_serde::de::VariantAccess::tuple_variant(__variant, #nfields, #visitor_expr))
+        quote!(_serde::de::VariantAccess::tuple_variant(__variant, #field_count, #visitor_expr))
     } else if nfields == 1 {
         let type_name = cattrs.name().deserialize_name();
         quote!(_serde::Deserializer::deserialize_newtype_struct(__deserializer, #type_name, #visitor_expr))
     } else {
         let type_name = cattrs.name().deserialize_name();
-        quote!(_serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #nfields, #visitor_expr))
+        quote!(_serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #field_count, #visitor_expr))
     };
 
-    let all_skipped = fields.iter().all(|field| field.attrs.skip_deserializing());
-    let visitor_var = if all_skipped {
+    let visitor_var = if field_count == 0 {
         quote!(_)
     } else {
         quote!(mut __seq)
@@ -605,6 +632,7 @@ fn deserialize_tuple_in_place(
     let place_life = place_lifetime();
 
     quote_block! {
+        #[doc(hidden)]
         struct __Visitor #in_place_impl_generics #where_clause {
             place: &#place_life mut #this_type #ty_generics,
             lifetime: _serde::__private::PhantomData<&#delife ()>,
@@ -894,21 +922,24 @@ fn deserialize_newtype_struct_in_place(params: &Parameters, field: &Field) -> To
     }
 }
 
-enum Untagged {
-    Yes,
-    No,
+enum StructForm<'a> {
+    Struct,
+    /// Contains a variant name
+    ExternallyTagged(&'a syn::Ident),
+    /// Contains a variant name and an intermediate deserializer from which actual
+    /// deserialization will be performed
+    InternallyTagged(&'a syn::Ident, TokenStream),
+    /// Contains a variant name and an intermediate deserializer from which actual
+    /// deserialization will be performed
+    Untagged(&'a syn::Ident, TokenStream),
 }
 
 fn deserialize_struct(
-    variant_ident: Option<&syn::Ident>,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<TokenStream>,
-    untagged: &Untagged,
+    form: StructForm,
 ) -> Fragment {
-    let is_enum = variant_ident.is_some();
-
     let this_type = &params.this_type;
     let this_value = &params.this_value;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
@@ -925,83 +956,74 @@ fn deserialize_struct(
         quote!(#this_value)
     };
 
-    let type_path = match variant_ident {
-        Some(variant_ident) => quote!(#construct::#variant_ident),
-        None => construct,
+    let type_path = match form {
+        StructForm::Struct => construct,
+        StructForm::ExternallyTagged(variant_ident)
+        | StructForm::InternallyTagged(variant_ident, _)
+        | StructForm::Untagged(variant_ident, _) => quote!(#construct::#variant_ident),
     };
-    let expecting = match variant_ident {
-        Some(variant_ident) => format!("struct variant {}::{}", params.type_name(), variant_ident),
-        None => format!("struct {}", params.type_name()),
+    let expecting = match form {
+        StructForm::Struct => format!("struct {}", params.type_name()),
+        StructForm::ExternallyTagged(variant_ident)
+        | StructForm::InternallyTagged(variant_ident, _)
+        | StructForm::Untagged(variant_ident, _) => {
+            format!("struct variant {}::{}", params.type_name(), variant_ident)
+        }
     };
     let expecting = cattrs.expecting().unwrap_or(&expecting);
 
-    let visit_seq = Stmts(deserialize_seq(
-        &type_path, params, fields, true, cattrs, expecting,
+    let field_names_idents: Vec<_> = fields
+        .iter()
+        .enumerate()
+        // Skip fields that shouldn't be deserialized or that were flattened,
+        // so they don't appear in the storage in their literal form
+        .filter(|&(_, field)| !field.attrs.skip_deserializing() && !field.attrs.flatten())
+        .map(|(i, field)| {
+            (
+                field.attrs.name().deserialize_name(),
+                field_i(i),
+                field.attrs.aliases(),
+            )
+        })
+        .collect();
+    let field_visitor = Stmts(deserialize_generated_identifier(
+        &field_names_idents,
+        cattrs,
+        false,
+        None,
     ));
 
-    let (field_visitor, fields_stmt, visit_map) = if cattrs.has_flatten() {
-        deserialize_struct_as_map_visitor(&type_path, params, fields, cattrs)
-    } else {
-        deserialize_struct_as_struct_visitor(&type_path, params, fields, cattrs)
-    };
-    let field_visitor = Stmts(field_visitor);
-    let fields_stmt = fields_stmt.map(Stmts);
-    let visit_map = Stmts(visit_map);
-
-    let visitor_expr = quote! {
-        __Visitor {
-            marker: _serde::__private::PhantomData::<#this_type #ty_generics>,
-            lifetime: _serde::__private::PhantomData,
-        }
-    };
-    let need_seed = deserializer.is_none();
-    let dispatch = if let Some(deserializer) = deserializer {
-        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)
-        }
-    } else if cattrs.has_flatten() {
-        quote! {
-            _serde::Deserializer::deserialize_map(__deserializer, #visitor_expr)
-        }
-    } else {
-        let type_name = cattrs.name().deserialize_name();
-        quote! {
-            _serde::Deserializer::deserialize_struct(__deserializer, #type_name, FIELDS, #visitor_expr)
-        }
-    };
-
-    let all_skipped = fields.iter().all(|field| field.attrs.skip_deserializing());
-    let visitor_var = if all_skipped {
-        quote!(_)
-    } else {
-        quote!(mut __seq)
-    };
-
     // untagged struct variants do not get a visit_seq method. The same applies to
     // structs that only have a map representation.
-    let visit_seq = match *untagged {
-        Untagged::No if !cattrs.has_flatten() => Some(quote! {
-            #[inline]
-            fn visit_seq<__A>(self, #visitor_var: __A) -> _serde::__private::Result<Self::Value, __A::Error>
-            where
-                __A: _serde::de::SeqAccess<#delife>,
-            {
-                #visit_seq
-            }
-        }),
-        _ => None,
-    };
+    let visit_seq = match form {
+        StructForm::Untagged(..) => None,
+        _ if cattrs.has_flatten() => None,
+        _ => {
+            let mut_seq = if field_names_idents.is_empty() {
+                quote!(_)
+            } else {
+                quote!(mut __seq)
+            };
 
-    let visitor_seed = if need_seed && is_enum && cattrs.has_flatten() {
-        Some(quote! {
+            let visit_seq = Stmts(deserialize_seq(
+                &type_path, params, fields, true, cattrs, expecting,
+            ));
+
+            Some(quote! {
+                #[inline]
+                fn visit_seq<__A>(self, #mut_seq: __A) -> _serde::__private::Result<Self::Value, __A::Error>
+                where
+                    __A: _serde::de::SeqAccess<#delife>,
+                {
+                    #visit_seq
+                }
+            })
+        }
+    };
+    let visit_map = Stmts(deserialize_map(&type_path, params, fields, cattrs));
+
+    let visitor_seed = match form {
+        StructForm::ExternallyTagged(..) if cattrs.has_flatten() => Some(quote! {
             impl #de_impl_generics _serde::de::DeserializeSeed<#delife> for __Visitor #de_ty_generics #where_clause {
                 type Value = #this_type #ty_generics;
 
@@ -1012,14 +1034,57 @@ fn deserialize_struct(
                     _serde::Deserializer::deserialize_map(__deserializer, self)
                 }
             }
-        })
-    } else {
+        }),
+        _ => None,
+    };
+
+    let fields_stmt = if cattrs.has_flatten() {
         None
+    } else {
+        let field_names = field_names_idents
+            .iter()
+            .flat_map(|(_, _, aliases)| aliases);
+
+        Some(quote! {
+            #[doc(hidden)]
+            const FIELDS: &'static [&'static str] = &[ #(#field_names),* ];
+        })
+    };
+
+    let visitor_expr = quote! {
+        __Visitor {
+            marker: _serde::__private::PhantomData::<#this_type #ty_generics>,
+            lifetime: _serde::__private::PhantomData,
+        }
+    };
+    let dispatch = match form {
+        StructForm::Struct if cattrs.has_flatten() => quote! {
+            _serde::Deserializer::deserialize_map(__deserializer, #visitor_expr)
+        },
+        StructForm::Struct => {
+            let type_name = cattrs.name().deserialize_name();
+            quote! {
+                _serde::Deserializer::deserialize_struct(__deserializer, #type_name, FIELDS, #visitor_expr)
+            }
+        }
+        StructForm::ExternallyTagged(_) if cattrs.has_flatten() => quote! {
+            _serde::de::VariantAccess::newtype_variant_seed(__variant, #visitor_expr)
+        },
+        StructForm::ExternallyTagged(_) => quote! {
+            _serde::de::VariantAccess::struct_variant(__variant, FIELDS, #visitor_expr)
+        },
+        StructForm::InternallyTagged(_, deserializer) => quote! {
+            _serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
+        },
+        StructForm::Untagged(_, deserializer) => quote! {
+            _serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
+        },
     };
 
     quote_block! {
         #field_visitor
 
+        #[doc(hidden)]
         struct __Visitor #de_impl_generics #where_clause {
             marker: _serde::__private::PhantomData<#this_type #ty_generics>,
             lifetime: _serde::__private::PhantomData<&#delife ()>,
@@ -1132,6 +1197,7 @@ fn deserialize_struct_in_place(
     Some(quote_block! {
         #field_visitor
 
+        #[doc(hidden)]
         struct __Visitor #in_place_impl_generics #where_clause {
             place: &#place_life mut #this_type #ty_generics,
             lifetime: _serde::__private::PhantomData<&#delife ()>,
@@ -1165,6 +1231,22 @@ fn deserialize_enum(
     params: &Parameters,
     variants: &[Variant],
     cattrs: &attr::Container,
+) -> Fragment {
+    // The variants have already been checked (in ast.rs) that all untagged variants appear at the end
+    match variants.iter().position(|var| var.attrs.untagged()) {
+        Some(variant_idx) => {
+            let (tagged, untagged) = variants.split_at(variant_idx);
+            let tagged_frag = Expr(deserialize_homogeneous_enum(params, tagged, cattrs));
+            deserialize_untagged_enum_after(params, untagged, cattrs, Some(tagged_frag))
+        }
+        None => deserialize_homogeneous_enum(params, variants, cattrs),
+    }
+}
+
+fn deserialize_homogeneous_enum(
+    params: &Parameters,
+    variants: &[Variant],
+    cattrs: &attr::Container,
 ) -> Fragment {
     match cattrs.tag() {
         attr::TagType::External => deserialize_externally_tagged_enum(params, variants, cattrs),
@@ -1203,6 +1285,7 @@ fn prepare_enum_variant_enum(
     let variants_stmt = {
         let variant_names = variant_names_idents.iter().map(|(name, _, _)| name);
         quote! {
+            #[doc(hidden)]
             const VARIANTS: &'static [&'static str] = &[ #(#variant_names),* ];
         }
     };
@@ -1275,6 +1358,7 @@ fn deserialize_externally_tagged_enum(
     quote_block! {
         #variant_visitor
 
+        #[doc(hidden)]
         struct __Visitor #de_impl_generics #where_clause {
             marker: _serde::__private::PhantomData<#this_type #ty_generics>,
             lifetime: _serde::__private::PhantomData<&#delife ()>,
@@ -1329,9 +1413,7 @@ fn deserialize_internally_tagged_enum(
                 params,
                 variant,
                 cattrs,
-                quote! {
-                    _serde::__private::de::ContentDeserializer::<__D::Error>::new(__tagged.content)
-                },
+                quote!(__deserializer),
             ));
 
             quote! {
@@ -1347,11 +1429,12 @@ fn deserialize_internally_tagged_enum(
 
         #variants_stmt
 
-        let __tagged = try!(_serde::Deserializer::deserialize_any(
+        let (__tag, __content) = try!(_serde::Deserializer::deserialize_any(
             __deserializer,
             _serde::__private::de::TaggedContentVisitor::<__Field>::new(#tag, #expecting)));
+        let __deserializer = _serde::__private::de::ContentDeserializer::<__D::Error>::new(__content);
 
-        match __tagged.tag {
+        match __tag {
             #(#variant_arms)*
         }
     }
@@ -1522,6 +1605,7 @@ fn deserialize_adjacently_tagged_enum(
 
         #variants_stmt
 
+        #[doc(hidden)]
         struct __Seed #de_impl_generics #where_clause {
             field: __Field,
             marker: _serde::__private::PhantomData<#this_type #ty_generics>,
@@ -1541,6 +1625,7 @@ fn deserialize_adjacently_tagged_enum(
             }
         }
 
+        #[doc(hidden)]
         struct __Visitor #de_impl_generics #where_clause {
             marker: _serde::__private::PhantomData<#this_type #ty_generics>,
             lifetime: _serde::__private::PhantomData<&#delife ()>,
@@ -1643,6 +1728,7 @@ fn deserialize_adjacently_tagged_enum(
             }
         }
 
+        #[doc(hidden)]
         const FIELDS: &'static [&'static str] = &[#tag, #content];
         _serde::Deserializer::deserialize_struct(
             __deserializer,
@@ -1660,6 +1746,16 @@ fn deserialize_untagged_enum(
     params: &Parameters,
     variants: &[Variant],
     cattrs: &attr::Container,
+) -> Fragment {
+    let first_attempt = None;
+    deserialize_untagged_enum_after(params, variants, cattrs, first_attempt)
+}
+
+fn deserialize_untagged_enum_after(
+    params: &Parameters,
+    variants: &[Variant],
+    cattrs: &attr::Container,
+    first_attempt: Option<Expr>,
 ) -> Fragment {
     let attempts = variants
         .iter()
@@ -1669,12 +1765,10 @@ fn deserialize_untagged_enum(
                 params,
                 variant,
                 cattrs,
-                quote!(
-                    _serde::__private::de::ContentRefDeserializer::<__D::Error>::new(&__content)
-                ),
+                quote!(__deserializer),
             ))
         });
-
+    let attempts = first_attempt.into_iter().chain(attempts);
     // TODO this message could be better by saving the errors from the failed
     // attempts. The heuristic used by TOML was to count the number of fields
     // processed before an error, and use the error that happened after the
@@ -1689,6 +1783,7 @@ fn deserialize_untagged_enum(
 
     quote_block! {
         let __content = try!(<_serde::__private::de::Content as _serde::Deserialize>::deserialize(__deserializer));
+        let __deserializer = _serde::__private::de::ContentRefDeserializer::<__D::Error>::new(&__content);
 
         #(
             if let _serde::__private::Ok(__ok) = #attempts {
@@ -1730,16 +1825,17 @@ fn deserialize_externally_tagged_variant(
             &variant.fields[0],
             cattrs,
         ),
-        Style::Tuple => {
-            deserialize_tuple(Some(variant_ident), params, &variant.fields, cattrs, None)
-        }
-        Style::Struct => deserialize_struct(
-            Some(variant_ident),
+        Style::Tuple => deserialize_tuple(
             params,
             &variant.fields,
             cattrs,
-            None,
-            &Untagged::No,
+            TupleForm::ExternallyTagged(variant_ident),
+        ),
+        Style::Struct => deserialize_struct(
+            params,
+            &variant.fields,
+            cattrs,
+            StructForm::ExternallyTagged(variant_ident),
         ),
     }
 }
@@ -1779,12 +1875,10 @@ fn deserialize_internally_tagged_variant(
             &deserializer,
         ),
         Style::Struct => deserialize_struct(
-            Some(variant_ident),
             params,
             &variant.fields,
             cattrs,
-            Some(deserializer),
-            &Untagged::No,
+            StructForm::InternallyTagged(variant_ident, deserializer),
         ),
         Style::Tuple => unreachable!("checked in serde_derive_internals"),
     }
@@ -1831,19 +1925,16 @@ fn deserialize_untagged_variant(
             &deserializer,
         ),
         Style::Tuple => deserialize_tuple(
-            Some(variant_ident),
             params,
             &variant.fields,
             cattrs,
-            Some(deserializer),
+            TupleForm::Untagged(variant_ident, deserializer),
         ),
         Style::Struct => deserialize_struct(
-            Some(variant_ident),
             params,
             &variant.fields,
             cattrs,
-            Some(deserializer),
-            &Untagged::Yes,
+            StructForm::Untagged(variant_ident, deserializer),
         ),
     }
 }
@@ -1954,11 +2045,13 @@ fn deserialize_generated_identifier(
 
     quote_block! {
         #[allow(non_camel_case_types)]
+        #[doc(hidden)]
         enum __Field #lifetime {
             #(#field_idents,)*
             #ignore_variant
         }
 
+        #[doc(hidden)]
         struct __FieldVisitor;
 
         impl<'de> _serde::de::Visitor<'de> for __FieldVisitor {
@@ -2046,11 +2139,13 @@ fn deserialize_custom_identifier(
         None
     } else if is_variant {
         let variants = quote! {
+            #[doc(hidden)]
             const VARIANTS: &'static [&'static str] = &[ #(#names),* ];
         };
         Some(variants)
     } else {
         let fields = quote! {
+            #[doc(hidden)]
             const FIELDS: &'static [&'static str] = &[ #(#names),* ];
         };
         Some(fields)
@@ -2072,6 +2167,7 @@ fn deserialize_custom_identifier(
     quote_block! {
         #names_const
 
+        #[doc(hidden)]
         struct __FieldVisitor #de_impl_generics #where_clause {
             marker: _serde::__private::PhantomData<#this_type #ty_generics>,
             lifetime: _serde::__private::PhantomData<&#delife ()>,
@@ -2379,70 +2475,6 @@ fn deserialize_identifier(
     }
 }
 
-fn deserialize_struct_as_struct_visitor(
-    struct_path: &TokenStream,
-    params: &Parameters,
-    fields: &[Field],
-    cattrs: &attr::Container,
-) -> (Fragment, Option<Fragment>, Fragment) {
-    assert!(!cattrs.has_flatten());
-
-    let field_names_idents: Vec<_> = fields
-        .iter()
-        .enumerate()
-        .filter(|&(_, field)| !field.attrs.skip_deserializing())
-        .map(|(i, field)| {
-            (
-                field.attrs.name().deserialize_name(),
-                field_i(i),
-                field.attrs.aliases(),
-            )
-        })
-        .collect();
-
-    let fields_stmt = {
-        let field_names = field_names_idents
-            .iter()
-            .flat_map(|(_, _, aliases)| aliases);
-
-        quote_block! {
-            const FIELDS: &'static [&'static str] = &[ #(#field_names),* ];
-        }
-    };
-
-    let field_visitor = deserialize_generated_identifier(&field_names_idents, cattrs, false, None);
-
-    let visit_map = deserialize_map(struct_path, params, fields, cattrs);
-
-    (field_visitor, Some(fields_stmt), visit_map)
-}
-
-fn deserialize_struct_as_map_visitor(
-    struct_path: &TokenStream,
-    params: &Parameters,
-    fields: &[Field],
-    cattrs: &attr::Container,
-) -> (Fragment, Option<Fragment>, Fragment) {
-    let field_names_idents: Vec<_> = fields
-        .iter()
-        .enumerate()
-        .filter(|&(_, field)| !field.attrs.skip_deserializing() && !field.attrs.flatten())
-        .map(|(i, field)| {
-            (
-                field.attrs.name().deserialize_name(),
-                field_i(i),
-                field.attrs.aliases(),
-            )
-        })
-        .collect();
-
-    let field_visitor = deserialize_generated_identifier(&field_names_idents, cattrs, false, None);
-
-    let visit_map = deserialize_map(struct_path, params, fields, cattrs);
-
-    (field_visitor, None, visit_map)
-}
-
 fn deserialize_map(
     struct_path: &TokenStream,
     params: &Parameters,
@@ -2684,6 +2716,7 @@ fn deserialize_struct_as_struct_in_place_visitor(
     let fields_stmt = {
         let field_names = field_names_idents.iter().map(|(name, _, _)| name);
         quote_block! {
+            #[doc(hidden)]
             const FIELDS: &'static [&'static str] = &[ #(#field_names),* ];
         }
     };
@@ -2864,6 +2897,7 @@ fn wrap_deserialize_with(
     let delife = params.borrowed.de_lifetime();
 
     let wrapper = quote! {
+        #[doc(hidden)]
         struct __DeserializeWith #de_impl_generics #where_clause {
             value: #value_ty,
             phantom: _serde::__private::PhantomData<#this_type #ty_generics>,
@@ -3068,23 +3102,31 @@ struct DeTypeGenerics<'a>(&'a Parameters);
 #[cfg(feature = "deserialize_in_place")]
 struct InPlaceTypeGenerics<'a>(&'a Parameters);
 
+fn de_type_generics_to_tokens(
+    mut generics: syn::Generics,
+    borrowed: &BorrowedLifetimes,
+    tokens: &mut TokenStream,
+) {
+    if borrowed.de_lifetime_param().is_some() {
+        let def = syn::LifetimeParam {
+            attrs: Vec::new(),
+            lifetime: syn::Lifetime::new("'de", Span::call_site()),
+            colon_token: None,
+            bounds: Punctuated::new(),
+        };
+        // Prepend 'de lifetime to list of generics
+        generics.params = Some(syn::GenericParam::Lifetime(def))
+            .into_iter()
+            .chain(generics.params)
+            .collect();
+    }
+    let (_, ty_generics, _) = generics.split_for_impl();
+    ty_generics.to_tokens(tokens);
+}
+
 impl<'a> ToTokens for DeTypeGenerics<'a> {
     fn to_tokens(&self, tokens: &mut TokenStream) {
-        let mut generics = self.0.generics.clone();
-        if self.0.borrowed.de_lifetime_param().is_some() {
-            let def = syn::LifetimeParam {
-                attrs: Vec::new(),
-                lifetime: syn::Lifetime::new("'de", Span::call_site()),
-                colon_token: None,
-                bounds: Punctuated::new(),
-            };
-            generics.params = Some(syn::GenericParam::Lifetime(def))
-                .into_iter()
-                .chain(generics.params)
-                .collect();
-        }
-        let (_, ty_generics, _) = generics.split_for_impl();
-        ty_generics.to_tokens(tokens);
+        de_type_generics_to_tokens(self.0.generics.clone(), &self.0.borrowed, tokens);
     }
 }
 
@@ -3097,20 +3139,7 @@ impl<'a> ToTokens for InPlaceTypeGenerics<'a> {
             .chain(generics.params)
             .collect();
 
-        if self.0.borrowed.de_lifetime_param().is_some() {
-            let def = syn::LifetimeParam {
-                attrs: Vec::new(),
-                lifetime: syn::Lifetime::new("'de", Span::call_site()),
-                colon_token: None,
-                bounds: Punctuated::new(),
-            };
-            generics.params = Some(syn::GenericParam::Lifetime(def))
-                .into_iter()
-                .chain(generics.params)
-                .collect();
-        }
-        let (_, ty_generics, _) = generics.split_for_impl();
-        ty_generics.to_tokens(tokens);
+        de_type_generics_to_tokens(generics, &self.0.borrowed, tokens);
     }
 }
 

serde_derive/src/dummy.rs

@@ -1,23 +1,11 @@
-use proc_macro2::{Ident, TokenStream};
-use quote::format_ident;
+use proc_macro2::TokenStream;
 
 use syn;
 use try;
 
-pub fn wrap_in_const(
-    serde_path: Option<&syn::Path>,
-    trait_: &str,
-    ty: &Ident,
-    code: TokenStream,
-) -> TokenStream {
+pub fn wrap_in_const(serde_path: Option<&syn::Path>, code: TokenStream) -> TokenStream {
     let try_replacement = try::replacement();
 
-    let dummy_const = if cfg!(no_underscore_consts) {
-        format_ident!("_IMPL_{}_FOR_{}", trait_, unraw(ty))
-    } else {
-        format_ident!("_")
-    };
-
     let use_serde = match serde_path {
         Some(path) => quote! {
             use #path as _serde;
@@ -31,14 +19,10 @@ pub fn wrap_in_const(
     quote! {
         #[doc(hidden)]
         #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
-        const #dummy_const: () = {
+        const _: () = {
             #use_serde
             #try_replacement
             #code
         };
     }
 }
-
-fn unraw(ident: &Ident) -> String {
-    ident.to_string().trim_start_matches("r#").to_owned()
-}

serde_derive/src/internals/ast.rs

@@ -140,7 +140,7 @@ fn enum_from_ast<'a>(
     variants: &'a Punctuated<syn::Variant, Token![,]>,
     container_default: &attr::Default,
 ) -> Vec<Variant<'a>> {
-    variants
+    let variants: Vec<Variant> = variants
         .iter()
         .map(|variant| {
             let attrs = attr::Variant::from_ast(cx, variant);
@@ -154,7 +154,20 @@ fn enum_from_ast<'a>(
                 original: variant,
             }
         })
-        .collect()
+        .collect();
+
+    let index_of_last_tagged_variant = variants
+        .iter()
+        .rposition(|variant| !variant.attrs.untagged());
+    if let Some(index_of_last_tagged_variant) = index_of_last_tagged_variant {
+        for variant in &variants[..index_of_last_tagged_variant] {
+            if variant.attrs.untagged() {
+                cx.error_spanned_by(&variant.ident, "all variants with the #[serde(untagged)] attribute must be placed at the end of the enum");
+            }
+        }
+    }
+
+    variants
 }
 
 fn struct_from_ast<'a>(

serde_derive/src/internals/attr.rs

@@ -307,6 +307,12 @@ impl Container {
                 continue;
             }
 
+            if let syn::Meta::List(meta) = &attr.meta {
+                if meta.tokens.is_empty() {
+                    continue;
+                }
+            }
+
             if let Err(err) = attr.parse_nested_meta(|meta| {
                 if meta.path == RENAME {
                     // #[serde(rename = "foo")]
@@ -734,6 +740,7 @@ pub struct Variant {
     serialize_with: Option<syn::ExprPath>,
     deserialize_with: Option<syn::ExprPath>,
     borrow: Option<BorrowAttribute>,
+    untagged: bool,
 }
 
 struct BorrowAttribute {
@@ -756,12 +763,19 @@ impl Variant {
         let mut serialize_with = Attr::none(cx, SERIALIZE_WITH);
         let mut deserialize_with = Attr::none(cx, DESERIALIZE_WITH);
         let mut borrow = Attr::none(cx, BORROW);
+        let mut untagged = BoolAttr::none(cx, UNTAGGED);
 
         for attr in &variant.attrs {
             if attr.path() != SERDE {
                 continue;
             }
 
+            if let syn::Meta::List(meta) = &attr.meta {
+                if meta.tokens.is_empty() {
+                    continue;
+                }
+            }
+
             if let Err(err) = attr.parse_nested_meta(|meta| {
                 if meta.path == RENAME {
                     // #[serde(rename = "foo")]
@@ -867,6 +881,8 @@ impl Variant {
                             cx.error_spanned_by(variant, msg);
                         }
                     }
+                } else if meta.path == UNTAGGED {
+                    untagged.set_true(&meta.path);
                 } else {
                     let path = meta.path.to_token_stream().to_string().replace(' ', "");
                     return Err(
@@ -893,6 +909,7 @@ impl Variant {
             serialize_with: serialize_with.get(),
             deserialize_with: deserialize_with.get(),
             borrow: borrow.get(),
+            untagged: untagged.get(),
         }
     }
 
@@ -944,6 +961,10 @@ impl Variant {
     pub fn deserialize_with(&self) -> Option<&syn::ExprPath> {
         self.deserialize_with.as_ref()
     }
+
+    pub fn untagged(&self) -> bool {
+        self.untagged
+    }
 }
 
 /// Represents field attribute information
@@ -1033,6 +1054,12 @@ impl Field {
                 continue;
             }
 
+            if let syn::Meta::List(meta) = &attr.meta {
+                if meta.tokens.is_empty() {
+                    continue;
+                }
+            }
+
             if let Err(err) = attr.parse_nested_meta(|meta| {
                 if meta.path == RENAME {
                     // #[serde(rename = "foo")]
@@ -1381,21 +1408,26 @@ fn get_lit_str2(
     meta_item_name: Symbol,
     meta: &ParseNestedMeta,
 ) -> syn::Result<Option<syn::LitStr>> {
-    match meta.value()?.parse()? {
-        syn::Expr::Lit(syn::ExprLit {
-            lit: syn::Lit::Str(lit),
-            ..
-        }) => Ok(Some(lit)),
-        expr => {
-            cx.error_spanned_by(
-                expr,
-                format!(
-                    "expected serde {} attribute to be a string: `{} = \"...\"`",
-                    attr_name, meta_item_name
-                ),
-            );
-            Ok(None)
-        }
+    let expr: syn::Expr = meta.value()?.parse()?;
+    let mut value = &expr;
+    while let syn::Expr::Group(e) = value {
+        value = &e.expr;
+    }
+    if let syn::Expr::Lit(syn::ExprLit {
+        lit: syn::Lit::Str(lit),
+        ..
+    }) = value
+    {
+        Ok(Some(lit.clone()))
+    } else {
+        cx.error_spanned_by(
+            expr,
+            format!(
+                "expected serde {} attribute to be a string: `{} = \"...\"`",
+                attr_name, meta_item_name
+            ),
+        );
+        Ok(None)
     }
 }
 

serde_derive/src/internals/check.rs

@@ -3,8 +3,8 @@ use internals::attr::{Identifier, TagType};
 use internals::{ungroup, 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.
+// 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: &mut Container, derive: Derive) {
     check_remote_generic(cx, cont);
     check_getter(cx, cont);
@@ -17,18 +17,18 @@ pub fn check(cx: &Ctxt, cont: &mut Container, derive: Derive) {
     check_from_and_try_from(cx, cont);
 }
 
-/// Remote derive definition type must have either all of the generics of the
-/// remote type:
-///
-///     #[serde(remote = "Generic")]
-///     struct Generic<T> {…}
-///
-/// or none of them, i.e. defining impls for one concrete instantiation of the
-/// remote type only:
-///
-///     #[serde(remote = "Generic<T>")]
-///     struct ConcreteDef {…}
-///
+// Remote derive definition type must have either all of the generics of the
+// remote type:
+//
+//     #[serde(remote = "Generic")]
+//     struct Generic<T> {…}
+//
+// or none of them, i.e. defining impls for one concrete instantiation of the
+// remote type only:
+//
+//     #[serde(remote = "Generic<T>")]
+//     struct ConcreteDef {…}
+//
 fn check_remote_generic(cx: &Ctxt, cont: &Container) {
     if let Some(remote) = cont.attrs.remote() {
         let local_has_generic = !cont.generics.params.is_empty();
@@ -39,8 +39,8 @@ fn check_remote_generic(cx: &Ctxt, cont: &Container) {
     }
 }
 
-/// Getters are only allowed inside structs (not enums) with the `remote`
-/// attribute.
+// Getters are only allowed inside structs (not enums) with the `remote`
+// attribute.
 fn check_getter(cx: &Ctxt, cont: &Container) {
     match cont.data {
         Data::Enum(_) => {
@@ -62,7 +62,7 @@ fn check_getter(cx: &Ctxt, cont: &Container) {
     }
 }
 
-/// Flattening has some restrictions we can test.
+// Flattening has some restrictions we can test.
 fn check_flatten(cx: &Ctxt, cont: &Container) {
     match &cont.data {
         Data::Enum(variants) => {
@@ -101,18 +101,16 @@ fn check_flatten_field(cx: &Ctxt, style: Style, field: &Field) {
     }
 }
 
-/// The `other` attribute must be used at most once and it must be the last
-/// variant of an enum.
-///
-/// Inside a `variant_identifier` all variants must be unit variants. Inside a
-/// `field_identifier` all but possibly one variant must be unit variants. The
-/// last variant may be a newtype variant which is an implicit "other" case.
+// The `other` attribute must be used at most once and it must be the last
+// variant of an enum.
+//
+// Inside a `variant_identifier` all variants must be unit variants. Inside a
+// `field_identifier` all but possibly one variant must be unit variants. The
+// last variant may be a newtype variant which is an implicit "other" case.
 fn check_identifier(cx: &Ctxt, cont: &Container) {
     let variants = match &cont.data {
         Data::Enum(variants) => variants,
-        Data::Struct(_, _) => {
-            return;
-        }
+        Data::Struct(_, _) => return,
     };
 
     for (i, variant) in variants.iter().enumerate() {
@@ -189,17 +187,15 @@ fn check_identifier(cx: &Ctxt, cont: &Container) {
     }
 }
 
-/// Skip-(de)serializing attributes are not allowed on variants marked
-/// (de)serialize_with.
+// Skip-(de)serializing attributes are not allowed on variants marked
+// (de)serialize_with.
 fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
     let variants = match &cont.data {
         Data::Enum(variants) => variants,
-        Data::Struct(_, _) => {
-            return;
-        }
+        Data::Struct(_, _) => return,
     };
 
-    for variant in variants.iter() {
+    for variant in variants {
         if variant.attrs.serialize_with().is_some() {
             if variant.attrs.skip_serializing() {
                 cx.error_spanned_by(
@@ -264,10 +260,9 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
     }
 }
 
-/// The tag of an internally-tagged struct variant must not be
-/// the same as either one of its fields, as this would result in
-/// duplicate keys in the serialized output and/or ambiguity in
-/// the to-be-deserialized input.
+// The tag of an internally-tagged struct variant must not be the same as either
+// one of its fields, as this would result in duplicate keys in the serialized
+// output and/or ambiguity in the to-be-deserialized input.
 fn check_internal_tag_field_name_conflict(cx: &Ctxt, cont: &Container) {
     let variants = match &cont.data {
         Data::Enum(variants) => variants,
@@ -313,8 +308,8 @@ fn check_internal_tag_field_name_conflict(cx: &Ctxt, cont: &Container) {
     }
 }
 
-/// In the case of adjacently-tagged enums, the type and the
-/// contents tag must differ, for the same reason.
+// In the case of adjacently-tagged enums, the type and the contents tag must
+// differ, for the same reason.
 fn check_adjacent_tag_conflict(cx: &Ctxt, cont: &Container) {
     let (type_tag, content_tag) = match cont.attrs.tag() {
         TagType::Adjacent { tag, content } => (tag, content),
@@ -332,7 +327,7 @@ fn check_adjacent_tag_conflict(cx: &Ctxt, cont: &Container) {
     }
 }
 
-/// Enums and unit structs cannot be transparent.
+// Enums and unit structs cannot be transparent.
 fn check_transparent(cx: &Ctxt, cont: &mut Container, derive: Derive) {
     if !cont.attrs.transparent() {
         return;

serde_derive/src/internals/ctxt.rs

@@ -44,12 +44,19 @@ impl Ctxt {
     }
 
     /// Consume this object, producing a formatted error string if there are errors.
-    pub fn check(self) -> Result<(), Vec<syn::Error>> {
-        let errors = self.errors.borrow_mut().take().unwrap();
-        match errors.len() {
-            0 => Ok(()),
-            _ => Err(errors),
+    pub fn check(self) -> syn::Result<()> {
+        let mut errors = self.errors.borrow_mut().take().unwrap().into_iter();
+
+        let mut combined = match errors.next() {
+            Some(first) => first,
+            None => return Ok(()),
+        };
+
+        for rest in errors {
+            combined.combine(rest);
         }
+
+        Err(combined)
     }
 }
 

serde_derive/src/lib.rs

@@ -1,7 +1,7 @@
 //! This crate provides Serde's two derive macros.
 //!
-//! ```edition2018
-//! # use serde_derive::{Serialize, Deserialize};
+//! ```edition2021
+//! # use serde_derive::{Deserialize, Serialize};
 //! #
 //! #[derive(Serialize, Deserialize)]
 //! # struct S;
@@ -13,7 +13,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.157")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.169")]
 #![allow(unknown_lints, bare_trait_objects)]
 // Ignored clippy lints
 #![allow(
@@ -92,7 +92,7 @@ mod try;
 pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);
     ser::expand_derive_serialize(&mut input)
-        .unwrap_or_else(to_compile_errors)
+        .unwrap_or_else(syn::Error::into_compile_error)
         .into()
 }
 
@@ -100,11 +100,6 @@ pub fn derive_serialize(input: TokenStream) -> TokenStream {
 pub fn derive_deserialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);
     de::expand_derive_deserialize(&mut input)
-        .unwrap_or_else(to_compile_errors)
+        .unwrap_or_else(syn::Error::into_compile_error)
         .into()
 }
-
-fn to_compile_errors(errors: Vec<syn::Error>) -> proc_macro2::TokenStream {
-    let compile_errors = errors.iter().map(syn::Error::to_compile_error);
-    quote!(#(#compile_errors)*)
-}

serde_derive/src/pretend.rs

@@ -97,29 +97,14 @@ fn pretend_fields_used_struct_packed(cont: &Container, fields: &[Field]) -> Toke
 
     let members = fields.iter().map(|field| &field.member).collect::<Vec<_>>();
 
-    #[cfg(not(no_ptr_addr_of))]
-    {
-        quote! {
-            match _serde::__private::None::<&#type_ident #ty_generics> {
-                _serde::__private::Some(__v @ #type_ident { #(#members: _),* }) => {
-                    #(
-                        let _ = _serde::__private::ptr::addr_of!(__v.#members);
-                    )*
-                }
-                _ => {}
-            }
-        }
-    }
-
-    #[cfg(no_ptr_addr_of)]
-    {
-        let placeholders = (0usize..).map(|i| format_ident!("__v{}", i));
-
-        quote! {
-            match _serde::__private::None::<#type_ident #ty_generics> {
-                _serde::__private::Some(#type_ident { #(#members: #placeholders),* }) => {}
-                _ => {}
+    quote! {
+        match _serde::__private::None::<&#type_ident #ty_generics> {
+            _serde::__private::Some(__v @ #type_ident { #(#members: _),* }) => {
+                #(
+                    let _ = _serde::__private::ptr::addr_of!(__v.#members);
+                )*
             }
+            _ => {}
         }
     }
 }

serde_derive/src/ser.rs

@@ -10,9 +10,7 @@ use internals::{attr, replace_receiver, Ctxt, Derive};
 use pretend;
 use this;
 
-pub fn expand_derive_serialize(
-    input: &mut syn::DeriveInput,
-) -> Result<TokenStream, Vec<syn::Error>> {
+pub fn expand_derive_serialize(input: &mut syn::DeriveInput) -> syn::Result<TokenStream> {
     replace_receiver(input);
 
     let ctxt = Ctxt::new();
@@ -59,8 +57,6 @@ pub fn expand_derive_serialize(
 
     Ok(dummy::wrap_in_const(
         cont.attrs.custom_serde_path(),
-        "SERIALIZE",
-        ident,
         impl_block,
     ))
 }
@@ -477,17 +473,19 @@ fn serialize_variant(
             }
         };
 
-        let body = Match(match cattrs.tag() {
-            attr::TagType::External => {
+        let body = Match(match (cattrs.tag(), variant.attrs.untagged()) {
+            (attr::TagType::External, false) => {
                 serialize_externally_tagged_variant(params, variant, variant_index, cattrs)
             }
-            attr::TagType::Internal { tag } => {
+            (attr::TagType::Internal { tag }, false) => {
                 serialize_internally_tagged_variant(params, variant, cattrs, tag)
             }
-            attr::TagType::Adjacent { tag, content } => {
+            (attr::TagType::Adjacent { tag, content }, false) => {
                 serialize_adjacently_tagged_variant(params, variant, cattrs, tag, content)
             }
-            attr::TagType::None => serialize_untagged_variant(params, variant, cattrs),
+            (attr::TagType::None, _) | (_, true) => {
+                serialize_untagged_variant(params, variant, cattrs)
+            }
         });
 
         quote! {
@@ -719,6 +717,7 @@ fn serialize_adjacently_tagged_variant(
     let (wrapper_impl_generics, wrapper_ty_generics, _) = wrapper_generics.split_for_impl();
 
     quote_block! {
+        #[doc(hidden)]
         struct __AdjacentlyTagged #wrapper_generics #where_clause {
             data: (#(&'__a #fields_ty,)*),
             phantom: _serde::__private::PhantomData<#this_type #ty_generics>,
@@ -982,6 +981,7 @@ fn serialize_struct_variant_with_flatten(
             let (wrapper_impl_generics, wrapper_ty_generics, _) = wrapper_generics.split_for_impl();
 
             quote_block! {
+                #[doc(hidden)]
                 struct __EnumFlatten #wrapper_generics #where_clause {
                     data: (#(&'__a #fields_ty,)*),
                     phantom: _serde::__private::PhantomData<#this_type #ty_generics>,
@@ -1212,6 +1212,7 @@ fn wrap_serialize_with(
     });
 
     quote!({
+        #[doc(hidden)]
         struct __SerializeWith #wrapper_impl_generics #where_clause {
             values: (#(&'__a #field_tys, )*),
             phantom: _serde::__private::PhantomData<#this_type #ty_generics>,

serde_derive_internals/.clippy.toml

@@ -1 +0,0 @@
-msrv = "1.31.0"

serde_derive_internals/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive_internals"
-version = "0.26.0" # remember to update html_root_url
+version = "0.28.0" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 description = "AST representation used by Serde derive macros. Unstable."
 documentation = "https://docs.rs/serde_derive_internals"
@@ -17,7 +17,7 @@ path = "lib.rs"
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = { version = "2.0", default-features = false, features = ["derive", "parsing", "printing", "clone-impls"] }
+syn = { version = "2.0.24", default-features = false, features = ["clone-impls", "derive", "parsing", "printing"] }
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]

serde_derive_internals/lib.rs

@@ -1,4 +1,4 @@
-#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.26.0")]
+#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.28.0")]
 #![allow(unknown_lints, bare_trait_objects)]
 // Ignored clippy lints
 #![allow(

serde_test/.clippy.toml

@@ -1 +0,0 @@
-msrv = "1.13.0"

serde_test/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_test"
-version = "1.0.157" # remember to update html_root_url
+version = "1.0.169" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
 categories = ["development-tools::testing"]
@@ -18,7 +18,7 @@ rust-version = "1.19"
 serde = { version = "1.0.60", path = "../serde" }
 
 [dev-dependencies]
-serde = { version = "1.0", path = "../serde" }
+serde = { version = "1.0", path = "../serde", features = ["rc"] }
 serde_derive = { version = "1.0", path = "../serde_derive" }
 
 [lib]

serde_test/src/assert.rs

@@ -8,8 +8,8 @@ use std::fmt::Debug;
 
 /// Runs both `assert_ser_tokens` and `assert_de_tokens`.
 ///
-/// ```edition2018
-/// # use serde::{Serialize, Deserialize};
+/// ```edition2021
+/// # use serde_derive::{Deserialize, Serialize};
 /// # use serde_test::{assert_tokens, Token};
 /// #
 /// #[derive(Serialize, Deserialize, PartialEq, Debug)]
@@ -19,14 +19,17 @@ use std::fmt::Debug;
 /// }
 ///
 /// let s = S { a: 0, b: 0 };
-/// assert_tokens(&s, &[
-///     Token::Struct { name: "S", len: 2 },
-///     Token::Str("a"),
-///     Token::U8(0),
-///     Token::Str("b"),
-///     Token::U8(0),
-///     Token::StructEnd,
-/// ]);
+/// assert_tokens(
+///     &s,
+///     &[
+///         Token::Struct { name: "S", len: 2 },
+///         Token::Str("a"),
+///         Token::U8(0),
+///         Token::Str("b"),
+///         Token::U8(0),
+///         Token::StructEnd,
+///     ],
+/// );
 /// ```
 #[cfg_attr(not(no_track_caller), track_caller)]
 pub fn assert_tokens<'de, T>(value: &T, tokens: &'de [Token])
@@ -39,8 +42,8 @@ where
 
 /// Asserts that `value` serializes to the given `tokens`.
 ///
-/// ```edition2018
-/// # use serde::{Serialize, Deserialize};
+/// ```edition2021
+/// # use serde_derive::{Deserialize, Serialize};
 /// # use serde_test::{assert_ser_tokens, Token};
 /// #
 /// #[derive(Serialize, Deserialize, PartialEq, Debug)]
@@ -50,14 +53,17 @@ where
 /// }
 ///
 /// let s = S { a: 0, b: 0 };
-/// assert_ser_tokens(&s, &[
-///     Token::Struct { name: "S", len: 2 },
-///     Token::Str("a"),
-///     Token::U8(0),
-///     Token::Str("b"),
-///     Token::U8(0),
-///     Token::StructEnd,
-/// ]);
+/// assert_ser_tokens(
+///     &s,
+///     &[
+///         Token::Struct { name: "S", len: 2 },
+///         Token::Str("a"),
+///         Token::U8(0),
+///         Token::Str("b"),
+///         Token::U8(0),
+///         Token::StructEnd,
+///     ],
+/// );
 /// ```
 #[cfg_attr(not(no_track_caller), track_caller)]
 pub fn assert_ser_tokens<T: ?Sized>(value: &T, tokens: &[Token])
@@ -78,23 +84,24 @@ where
 /// Asserts that `value` serializes to the given `tokens`, and then yields
 /// `error`.
 ///
-/// ```edition2018
+/// ```edition2021
+/// use serde_derive::Serialize;
+/// use serde_test::{assert_ser_tokens_error, Token};
 /// use std::sync::{Arc, Mutex};
 /// use std::thread;
 ///
-/// use serde::Serialize;
-/// use serde_test::{assert_ser_tokens_error, Token};
-///
 /// #[derive(Serialize)]
 /// struct Example {
 ///     lock: Arc<Mutex<u32>>,
 /// }
 ///
 /// fn main() {
-///     let example = Example { lock: Arc::new(Mutex::new(0)) };
+///     let example = Example {
+///         lock: Arc::new(Mutex::new(0)),
+///     };
 ///     let lock = example.lock.clone();
 ///
-///     let _ = thread::spawn(move || {
+///     let thread = thread::spawn(move || {
 ///         // This thread will acquire the mutex first, unwrapping the result
 ///         // of `lock` because the lock has not been poisoned.
 ///         let _guard = lock.lock().unwrap();
@@ -102,10 +109,14 @@ where
 ///         // This panic while holding the lock (`_guard` is in scope) will
 ///         // poison the mutex.
 ///         panic!()
-///     }).join();
+///     });
+///     thread.join();
 ///
 ///     let expected = &[
-///         Token::Struct { name: "Example", len: 1 },
+///         Token::Struct {
+///             name: "Example",
+///             len: 1,
+///         },
 ///         Token::Str("lock"),
 ///     ];
 ///     let error = "lock poison error while serializing";
@@ -130,8 +141,8 @@ where
 
 /// Asserts that the given `tokens` deserialize into `value`.
 ///
-/// ```edition2018
-/// # use serde::{Serialize, Deserialize};
+/// ```edition2021
+/// # use serde_derive::{Deserialize, Serialize};
 /// # use serde_test::{assert_de_tokens, Token};
 /// #
 /// #[derive(Serialize, Deserialize, PartialEq, Debug)]
@@ -141,14 +152,17 @@ where
 /// }
 ///
 /// let s = S { a: 0, b: 0 };
-/// assert_de_tokens(&s, &[
-///     Token::Struct { name: "S", len: 2 },
-///     Token::Str("a"),
-///     Token::U8(0),
-///     Token::Str("b"),
-///     Token::U8(0),
-///     Token::StructEnd,
-/// ]);
+/// assert_de_tokens(
+///     &s,
+///     &[
+///         Token::Struct { name: "S", len: 2 },
+///         Token::Str("a"),
+///         Token::U8(0),
+///         Token::Str("b"),
+///         Token::U8(0),
+///         Token::StructEnd,
+///     ],
+/// );
 /// ```
 #[cfg_attr(not(no_track_caller), track_caller)]
 pub fn assert_de_tokens<'de, T>(value: &T, tokens: &'de [Token])
@@ -184,8 +198,8 @@ where
 
 /// Asserts that the given `tokens` yield `error` when deserializing.
 ///
-/// ```edition2018
-/// # use serde::{Serialize, Deserialize};
+/// ```edition2021
+/// # use serde_derive::{Deserialize, Serialize};
 /// # use serde_test::{assert_de_tokens_error, Token};
 /// #
 /// #[derive(Serialize, Deserialize, PartialEq, Debug)]

serde_test/src/configure.rs

@@ -14,7 +14,7 @@ pub struct Compact<T: ?Sized>(T);
 /// Trait to determine whether a value is represented in human-readable or
 /// compact form.
 ///
-/// ```edition2018
+/// ```edition2021
 /// use serde::{Deserialize, Deserializer, Serialize, Serializer};
 /// use serde_test::{assert_tokens, Configure, Token};
 ///

serde_test/src/de.rs

@@ -12,32 +12,29 @@ pub struct Deserializer<'de> {
     tokens: &'de [Token],
 }
 
-macro_rules! assert_next_token {
-    ($de:expr, $expected:expr) => {
-        match $de.next_token_opt() {
-            Some(token) if token == $expected => {}
-            Some(other) => panic!(
-                "expected Token::{} but deserialization wants Token::{}",
-                other, $expected
-            ),
-            None => panic!(
-                "end of tokens but deserialization wants Token::{}",
-                $expected
-            ),
-        }
-    };
+fn assert_next_token(de: &mut Deserializer, expected: Token) -> Result<(), Error> {
+    match de.next_token_opt() {
+        Some(token) if token == expected => Ok(()),
+        Some(other) => Err(de::Error::custom(format!(
+            "expected Token::{} but deserialization wants Token::{}",
+            other, expected,
+        ))),
+        None => Err(de::Error::custom(format!(
+            "end of tokens but deserialization wants Token::{}",
+            expected,
+        ))),
+    }
 }
 
-macro_rules! unexpected {
-    ($token:expr) => {
-        panic!("deserialization did not expect this token: {}", $token)
-    };
+fn unexpected(token: Token) -> Error {
+    de::Error::custom(format!(
+        "deserialization did not expect this token: {}",
+        token,
+    ))
 }
 
-macro_rules! end_of_tokens {
-    () => {
-        panic!("ran out of tokens to deserialize")
-    };
+fn end_of_tokens() -> Error {
+    de::Error::custom("ran out of tokens to deserialize")
 }
 
 impl<'de> Deserializer<'de> {
@@ -49,11 +46,8 @@ impl<'de> Deserializer<'de> {
         self.tokens.first().cloned()
     }
 
-    fn peek_token(&self) -> Token {
-        match self.peek_token_opt() {
-            Some(token) => token,
-            None => end_of_tokens!(),
-        }
+    fn peek_token(&self) -> Result<Token, Error> {
+        self.peek_token_opt().ok_or_else(end_of_tokens)
     }
 
     pub fn next_token_opt(&mut self) -> Option<Token> {
@@ -66,14 +60,10 @@ impl<'de> Deserializer<'de> {
         }
     }
 
-    fn next_token(&mut self) -> Token {
-        match self.tokens.split_first() {
-            Some((&first, rest)) => {
-                self.tokens = rest;
-                first
-            }
-            None => end_of_tokens!(),
-        }
+    fn next_token(&mut self) -> Result<Token, Error> {
+        let (&first, rest) = self.tokens.split_first().ok_or_else(end_of_tokens)?;
+        self.tokens = rest;
+        Ok(first)
     }
 
     pub fn remaining(&self) -> usize {
@@ -94,7 +84,7 @@ impl<'de> Deserializer<'de> {
             len: len,
             end: end,
         })?;
-        assert_next_token!(self, end);
+        assert_next_token(self, end)?;
         Ok(value)
     }
 
@@ -112,7 +102,7 @@ impl<'de> Deserializer<'de> {
             len: len,
             end: end,
         })?;
-        assert_next_token!(self, end);
+        assert_next_token(self, end)?;
         Ok(value)
     }
 }
@@ -129,7 +119,7 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        let token = self.next_token();
+        let token = self.next_token()?;
         match token {
             Token::Bool(v) => visitor.visit_bool(v),
             Token::I8(v) => visitor.visit_i8(v),
@@ -161,50 +151,50 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
             Token::Map { len } => self.visit_map(len, Token::MapEnd, visitor),
             Token::Struct { len, .. } => self.visit_map(Some(len), Token::StructEnd, visitor),
             Token::Enum { .. } => {
-                let variant = self.next_token();
-                let next = self.peek_token();
+                let variant = self.next_token()?;
+                let next = self.peek_token()?;
                 match (variant, next) {
                     (Token::Str(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_str(variant)
                     }
                     (Token::BorrowedStr(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_borrowed_str(variant)
                     }
                     (Token::String(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_string(variant.to_string())
                     }
                     (Token::Bytes(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_bytes(variant)
                     }
                     (Token::BorrowedBytes(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_borrowed_bytes(variant)
                     }
                     (Token::ByteBuf(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_byte_buf(variant.to_vec())
                     }
                     (Token::U8(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_u8(variant)
                     }
                     (Token::U16(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_u16(variant)
                     }
                     (Token::U32(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_u32(variant)
                     }
                     (Token::U64(variant), Token::Unit) => {
-                        self.next_token();
+                        self.next_token()?;
                         visitor.visit_u64(variant)
                     }
-                    (variant, Token::Unit) => unexpected!(variant),
+                    (variant, Token::Unit) => Err(unexpected(variant)),
                     (variant, _) => {
                         visitor.visit_map(EnumMapVisitor::new(self, variant, EnumFormat::Any))
                     }
@@ -232,9 +222,7 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
             | Token::MapEnd
             | Token::StructEnd
             | Token::TupleVariantEnd
-            | Token::StructVariantEnd => {
-                unexpected!(token);
-            }
+            | Token::StructVariantEnd => Err(unexpected(token)),
         }
     }
 
@@ -242,13 +230,13 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        match self.peek_token() {
+        match self.peek_token()? {
             Token::Unit | Token::None => {
-                self.next_token();
+                self.next_token()?;
                 visitor.visit_none()
             }
             Token::Some => {
-                self.next_token();
+                self.next_token()?;
                 visitor.visit_some(self)
             }
             _ => self.deserialize_any(visitor),
@@ -264,9 +252,9 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        match self.peek_token() {
+        match self.peek_token()? {
             Token::Enum { name: n } if name == n => {
-                self.next_token();
+                self.next_token()?;
 
                 visitor.visit_enum(DeserializerEnumVisitor { de: self })
             }
@@ -286,9 +274,9 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        match self.peek_token() {
+        match self.peek_token()? {
             Token::UnitStruct { .. } => {
-                assert_next_token!(self, Token::UnitStruct { name: name });
+                assert_next_token(self, Token::UnitStruct { name: name })?;
                 visitor.visit_unit()
             }
             _ => self.deserialize_any(visitor),
@@ -303,9 +291,9 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        match self.peek_token() {
+        match self.peek_token()? {
             Token::NewtypeStruct { .. } => {
-                assert_next_token!(self, Token::NewtypeStruct { name: name });
+                assert_next_token(self, Token::NewtypeStruct { name: name })?;
                 visitor.visit_newtype_struct(self)
             }
             _ => self.deserialize_any(visitor),
@@ -316,21 +304,21 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        match self.peek_token() {
+        match self.peek_token()? {
             Token::Unit | Token::UnitStruct { .. } => {
-                self.next_token();
+                self.next_token()?;
                 visitor.visit_unit()
             }
             Token::Seq { .. } => {
-                self.next_token();
+                self.next_token()?;
                 self.visit_seq(Some(len), Token::SeqEnd, visitor)
             }
             Token::Tuple { .. } => {
-                self.next_token();
+                self.next_token()?;
                 self.visit_seq(Some(len), Token::TupleEnd, visitor)
             }
             Token::TupleStruct { .. } => {
-                self.next_token();
+                self.next_token()?;
                 self.visit_seq(Some(len), Token::TupleStructEnd, visitor)
             }
             _ => self.deserialize_any(visitor),
@@ -346,25 +334,25 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        match self.peek_token() {
+        match self.peek_token()? {
             Token::Unit => {
-                self.next_token();
+                self.next_token()?;
                 visitor.visit_unit()
             }
             Token::UnitStruct { .. } => {
-                assert_next_token!(self, Token::UnitStruct { name: name });
+                assert_next_token(self, Token::UnitStruct { name: name })?;
                 visitor.visit_unit()
             }
             Token::Seq { .. } => {
-                self.next_token();
+                self.next_token()?;
                 self.visit_seq(Some(len), Token::SeqEnd, visitor)
             }
             Token::Tuple { .. } => {
-                self.next_token();
+                self.next_token()?;
                 self.visit_seq(Some(len), Token::TupleEnd, visitor)
             }
             Token::TupleStruct { len: n, .. } => {
-                assert_next_token!(self, Token::TupleStruct { name: name, len: n });
+                assert_next_token(self, Token::TupleStruct { name: name, len: n })?;
                 self.visit_seq(Some(len), Token::TupleStructEnd, visitor)
             }
             _ => self.deserialize_any(visitor),
@@ -380,13 +368,13 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        match self.peek_token() {
+        match self.peek_token()? {
             Token::Struct { len: n, .. } => {
-                assert_next_token!(self, Token::Struct { name: name, len: n });
+                assert_next_token(self, Token::Struct { name: name, len: n })?;
                 self.visit_map(Some(fields.len()), Token::StructEnd, visitor)
             }
             Token::Map { .. } => {
-                self.next_token();
+                self.next_token()?;
                 self.visit_map(Some(fields.len()), Token::MapEnd, visitor)
             }
             _ => self.deserialize_any(visitor),
@@ -476,7 +464,7 @@ impl<'de, 'a> EnumAccess<'de> for DeserializerEnumVisitor<'a, 'de> {
     where
         V: DeserializeSeed<'de>,
     {
-        match self.de.peek_token() {
+        match self.de.peek_token()? {
             Token::UnitVariant { variant: v, .. }
             | Token::NewtypeVariant { variant: v, .. }
             | Token::TupleVariant { variant: v, .. }
@@ -497,9 +485,9 @@ impl<'de, 'a> VariantAccess<'de> for DeserializerEnumVisitor<'a, 'de> {
     type Error = Error;
 
     fn unit_variant(self) -> Result<(), Error> {
-        match self.de.peek_token() {
+        match self.de.peek_token()? {
             Token::UnitVariant { .. } => {
-                self.de.next_token();
+                self.de.next_token()?;
                 Ok(())
             }
             _ => Deserialize::deserialize(self.de),
@@ -510,9 +498,9 @@ impl<'de, 'a> VariantAccess<'de> for DeserializerEnumVisitor<'a, 'de> {
     where
         T: DeserializeSeed<'de>,
     {
-        match self.de.peek_token() {
+        match self.de.peek_token()? {
             Token::NewtypeVariant { .. } => {
-                self.de.next_token();
+                self.de.next_token()?;
                 seed.deserialize(self.de)
             }
             _ => seed.deserialize(self.de),
@@ -523,26 +511,26 @@ impl<'de, 'a> VariantAccess<'de> for DeserializerEnumVisitor<'a, 'de> {
     where
         V: Visitor<'de>,
     {
-        match self.de.peek_token() {
+        match self.de.peek_token()? {
             Token::TupleVariant { len: enum_len, .. } => {
-                let token = self.de.next_token();
+                let token = self.de.next_token()?;
 
                 if len == enum_len {
                     self.de
                         .visit_seq(Some(len), Token::TupleVariantEnd, visitor)
                 } else {
-                    unexpected!(token);
+                    Err(unexpected(token))
                 }
             }
             Token::Seq {
                 len: Some(enum_len),
             } => {
-                let token = self.de.next_token();
+                let token = self.de.next_token()?;
 
                 if len == enum_len {
                     self.de.visit_seq(Some(len), Token::SeqEnd, visitor)
                 } else {
-                    unexpected!(token);
+                    Err(unexpected(token))
                 }
             }
             _ => de::Deserializer::deserialize_any(self.de, visitor),
@@ -557,27 +545,27 @@ impl<'de, 'a> VariantAccess<'de> for DeserializerEnumVisitor<'a, 'de> {
     where
         V: Visitor<'de>,
     {
-        match self.de.peek_token() {
+        match self.de.peek_token()? {
             Token::StructVariant { len: enum_len, .. } => {
-                let token = self.de.next_token();
+                let token = self.de.next_token()?;
 
                 if fields.len() == enum_len {
                     self.de
                         .visit_map(Some(fields.len()), Token::StructVariantEnd, visitor)
                 } else {
-                    unexpected!(token);
+                    Err(unexpected(token))
                 }
             }
             Token::Map {
                 len: Some(enum_len),
             } => {
-                let token = self.de.next_token();
+                let token = self.de.next_token()?;
 
                 if fields.len() == enum_len {
                     self.de
                         .visit_map(Some(fields.len()), Token::MapEnd, visitor)
                 } else {
-                    unexpected!(token);
+                    Err(unexpected(token))
                 }
             }
             _ => de::Deserializer::deserialize_any(self.de, visitor),
@@ -622,7 +610,7 @@ impl<'de, 'a> MapAccess<'de> for EnumMapVisitor<'a, 'de> {
                 .deserialize(BytesDeserializer { value: variant })
                 .map(Some),
             Some(Token::U32(variant)) => seed.deserialize(variant.into_deserializer()).map(Some),
-            Some(other) => unexpected!(other),
+            Some(other) => Err(unexpected(other)),
             None => Ok(None),
         }
     }
@@ -641,7 +629,7 @@ impl<'de, 'a> MapAccess<'de> for EnumMapVisitor<'a, 'de> {
                     };
                     seed.deserialize(SeqAccessDeserializer::new(visitor))?
                 };
-                assert_next_token!(self.de, Token::TupleVariantEnd);
+                assert_next_token(self.de, Token::TupleVariantEnd)?;
                 Ok(value)
             }
             EnumFormat::Map => {
@@ -653,7 +641,7 @@ impl<'de, 'a> MapAccess<'de> for EnumMapVisitor<'a, 'de> {
                     };
                     seed.deserialize(MapAccessDeserializer::new(visitor))?
                 };
-                assert_next_token!(self.de, Token::StructVariantEnd);
+                assert_next_token(self.de, Token::StructVariantEnd)?;
                 Ok(value)
             }
             EnumFormat::Any => seed.deserialize(&mut *self.de),

serde_test/src/lib.rs

@@ -20,11 +20,11 @@
 //!
 //! [`linked-hash-map`]: https://github.com/contain-rs/linked-hash-map
 //!
-//! ```edition2018
+//! ```edition2021
 //! # const IGNORE: &str = stringify! {
 //! use linked_hash_map::LinkedHashMap;
 //! # };
-//! use serde_test::{Token, assert_tokens};
+//! use serde_test::{assert_tokens, Token};
 //!
 //! # use std::fmt;
 //! # use std::marker::PhantomData;
@@ -106,10 +106,13 @@
 //! fn test_ser_de_empty() {
 //!     let map = LinkedHashMap::<char, u32>::new();
 //!
-//!     assert_tokens(&map, &[
-//!         Token::Map { len: Some(0) },
-//!         Token::MapEnd,
-//!     ]);
+//!     assert_tokens(
+//!         &map,
+//!         &[
+//!             Token::Map { len: Some(0) },
+//!             Token::MapEnd,
+//!         ],
+//!     );
 //! }
 //!
 //! #[test]
@@ -120,18 +123,19 @@
 //!     map.insert('a', 10);
 //!     map.insert('c', 30);
 //!
-//!     assert_tokens(&map, &[
-//!         Token::Map { len: Some(3) },
-//!         Token::Char('b'),
-//!         Token::I32(20),
-//!
-//!         Token::Char('a'),
-//!         Token::I32(10),
-//!
-//!         Token::Char('c'),
-//!         Token::I32(30),
-//!         Token::MapEnd,
-//!     ]);
+//!     assert_tokens(
+//!         &map,
+//!         &[
+//!             Token::Map { len: Some(3) },
+//!             Token::Char('b'),
+//!             Token::I32(20),
+//!             Token::Char('a'),
+//!             Token::I32(10),
+//!             Token::Char('c'),
+//!             Token::I32(30),
+//!             Token::MapEnd,
+//!         ],
+//!     );
 //! }
 //! #
 //! # fn main() {
@@ -140,7 +144,7 @@
 //! # }
 //! ```
 
-#![doc(html_root_url = "https://docs.rs/serde_test/1.0.157")]
+#![doc(html_root_url = "https://docs.rs/serde_test/1.0.169")]
 #![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
 // Ignored clippy lints
 #![cfg_attr(feature = "cargo-clippy", allow(float_cmp, needless_doctest_main))]
@@ -182,7 +186,3 @@ pub use assert::{
 pub use token::Token;
 
 pub use configure::{Compact, Configure, Readable};
-
-// Not public API.
-#[doc(hidden)]
-pub use de::Deserializer;

serde_test/src/ser.rs

@@ -63,14 +63,12 @@ macro_rules! assert_next_token {
     ($ser:expr, $actual:expr, $pat:pat, $guard:expr) => {
         match $ser.next_token() {
             Some($pat) if $guard => {}
-            Some(expected) => {
-                panic!("expected Token::{} but serialized as {}",
-                       expected, $actual);
-            }
-            None => {
-                panic!("expected end of tokens, but {} was serialized",
-                       $actual);
-            }
+            Some(expected) => return Err(ser::Error::custom(
+                format!("expected Token::{} but serialized as {}", expected, $actual)
+            )),
+            None => return Err(ser::Error::custom(
+                format!("expected end of tokens, but {} was serialized", $actual)
+            )),
         }
     };
 }

serde_test/src/token.rs

@@ -4,7 +4,7 @@ use std::fmt::{self, Debug, Display};
 pub enum Token {
     /// A serialized `bool`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&true, &[Token::Bool(true)]);
@@ -13,7 +13,7 @@ pub enum Token {
 
     /// A serialized `i8`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0i8, &[Token::I8(0)]);
@@ -22,7 +22,7 @@ pub enum Token {
 
     /// A serialized `i16`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0i16, &[Token::I16(0)]);
@@ -31,7 +31,7 @@ pub enum Token {
 
     /// A serialized `i32`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0i32, &[Token::I32(0)]);
@@ -40,7 +40,7 @@ pub enum Token {
 
     /// A serialized `i64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0i64, &[Token::I64(0)]);
@@ -49,7 +49,7 @@ pub enum Token {
 
     /// A serialized `u8`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0u8, &[Token::U8(0)]);
@@ -58,7 +58,7 @@ pub enum Token {
 
     /// A serialized `u16`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0u16, &[Token::U16(0)]);
@@ -67,7 +67,7 @@ pub enum Token {
 
     /// A serialized `u32`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0u32, &[Token::U32(0)]);
@@ -76,7 +76,7 @@ pub enum Token {
 
     /// A serialized `u64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0u64, &[Token::U64(0)]);
@@ -85,7 +85,7 @@ pub enum Token {
 
     /// A serialized `f32`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0f32, &[Token::F32(0.0)]);
@@ -94,7 +94,7 @@ pub enum Token {
 
     /// A serialized `f64`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&0f64, &[Token::F64(0.0)]);
@@ -103,7 +103,7 @@ pub enum Token {
 
     /// A serialized `char`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&'\n', &[Token::Char('\n')]);
@@ -112,7 +112,7 @@ pub enum Token {
 
     /// A serialized `str`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// let s = String::from("transient");
@@ -122,7 +122,7 @@ pub enum Token {
 
     /// A borrowed `str`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// let s: &str = "borrowed";
@@ -132,7 +132,7 @@ pub enum Token {
 
     /// A serialized `String`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// let s = String::from("owned");
@@ -151,7 +151,7 @@ pub enum Token {
 
     /// A serialized `Option<T>` containing none.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// let opt = None::<char>;
@@ -163,20 +163,17 @@ pub enum Token {
     ///
     /// The tokens of the value follow after this header.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// let opt = Some('c');
-    /// assert_tokens(&opt, &[
-    ///     Token::Some,
-    ///     Token::Char('c'),
-    /// ]);
+    /// assert_tokens(&opt, &[Token::Some, Token::Char('c')]);
     /// ```
     Some,
 
     /// A serialized `()`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// assert_tokens(&(), &[Token::Unit]);
@@ -185,8 +182,8 @@ pub enum Token {
 
     /// A serialized unit struct of the given name.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -200,8 +197,8 @@ pub enum Token {
 
     /// A unit variant of an enum.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -211,7 +208,13 @@ pub enum Token {
     /// }
     ///
     /// let a = E::A;
-    /// assert_tokens(&a, &[Token::UnitVariant { name: "E", variant: "A" }]);
+    /// assert_tokens(
+    ///     &a,
+    ///     &[Token::UnitVariant {
+    ///         name: "E",
+    ///         variant: "A",
+    ///     }],
+    /// );
     /// # }
     /// ```
     UnitVariant {
@@ -223,8 +226,8 @@ pub enum Token {
     ///
     /// After this header is the value contained in the newtype struct.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -232,10 +235,10 @@ pub enum Token {
     /// struct N(String);
     ///
     /// let n = N("newtype".to_owned());
-    /// assert_tokens(&n, &[
-    ///     Token::NewtypeStruct { name: "N" },
-    ///     Token::String("newtype"),
-    /// ]);
+    /// assert_tokens(
+    ///     &n,
+    ///     &[Token::NewtypeStruct { name: "N" }, Token::String("newtype")],
+    /// );
     /// # }
     /// ```
     NewtypeStruct { name: &'static str },
@@ -244,8 +247,8 @@ pub enum Token {
     ///
     /// After this header is the value contained in the newtype variant.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -255,10 +258,16 @@ pub enum Token {
     /// }
     ///
     /// let b = E::B(0);
-    /// assert_tokens(&b, &[
-    ///     Token::NewtypeVariant { name: "E", variant: "B" },
-    ///     Token::U8(0),
-    /// ]);
+    /// assert_tokens(
+    ///     &b,
+    ///     &[
+    ///         Token::NewtypeVariant {
+    ///             name: "E",
+    ///             variant: "B",
+    ///         },
+    ///         Token::U8(0),
+    ///     ],
+    /// );
     /// # }
     /// ```
     NewtypeVariant {
@@ -271,17 +280,20 @@ pub enum Token {
     /// After this header are the elements of the sequence, followed by
     /// `SeqEnd`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// let vec = vec!['a', 'b', 'c'];
-    /// assert_tokens(&vec, &[
-    ///     Token::Seq { len: Some(3) },
-    ///     Token::Char('a'),
-    ///     Token::Char('b'),
-    ///     Token::Char('c'),
-    ///     Token::SeqEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &vec,
+    ///     &[
+    ///         Token::Seq { len: Some(3) },
+    ///         Token::Char('a'),
+    ///         Token::Char('b'),
+    ///         Token::Char('c'),
+    ///         Token::SeqEnd,
+    ///     ],
+    /// );
     /// ```
     Seq { len: Option<usize> },
 
@@ -292,16 +304,19 @@ pub enum Token {
     ///
     /// After this header are the elements of the tuple, followed by `TupleEnd`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// let tuple = ('a', 100);
-    /// assert_tokens(&tuple, &[
-    ///     Token::Tuple { len: 2 },
-    ///     Token::Char('a'),
-    ///     Token::I32(100),
-    ///     Token::TupleEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &tuple,
+    ///     &[
+    ///         Token::Tuple { len: 2 },
+    ///         Token::Char('a'),
+    ///         Token::I32(100),
+    ///         Token::TupleEnd,
+    ///     ],
+    /// );
     /// ```
     Tuple { len: usize },
 
@@ -313,8 +328,8 @@ pub enum Token {
     /// After this header are the fields of the tuple struct, followed by
     /// `TupleStructEnd`.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -322,12 +337,15 @@ pub enum Token {
     /// struct T(u8, u8);
     ///
     /// let t = T(0, 0);
-    /// assert_tokens(&t, &[
-    ///     Token::TupleStruct { name: "T", len: 2 },
-    ///     Token::U8(0),
-    ///     Token::U8(0),
-    ///     Token::TupleStructEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &t,
+    ///     &[
+    ///         Token::TupleStruct { name: "T", len: 2 },
+    ///         Token::U8(0),
+    ///         Token::U8(0),
+    ///         Token::TupleStructEnd,
+    ///     ],
+    /// );
     /// # }
     /// ```
     TupleStruct { name: &'static str, len: usize },
@@ -340,8 +358,8 @@ pub enum Token {
     /// After this header are the fields of the tuple variant, followed by
     /// `TupleVariantEnd`.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -351,12 +369,19 @@ pub enum Token {
     /// }
     ///
     /// let c = E::C(0, 0);
-    /// assert_tokens(&c, &[
-    ///     Token::TupleVariant { name: "E", variant: "C", len: 2 },
-    ///     Token::U8(0),
-    ///     Token::U8(0),
-    ///     Token::TupleVariantEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &c,
+    ///     &[
+    ///         Token::TupleVariant {
+    ///             name: "E",
+    ///             variant: "C",
+    ///             len: 2,
+    ///         },
+    ///         Token::U8(0),
+    ///         Token::U8(0),
+    ///         Token::TupleVariantEnd,
+    ///     ],
+    /// );
     /// # }
     /// ```
     TupleVariant {
@@ -372,7 +397,7 @@ pub enum Token {
     ///
     /// After this header are the entries of the map, followed by `MapEnd`.
     ///
-    /// ```edition2018
+    /// ```edition2021
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// use std::collections::BTreeMap;
@@ -381,14 +406,17 @@ pub enum Token {
     /// map.insert('A', 65);
     /// map.insert('Z', 90);
     ///
-    /// assert_tokens(&map, &[
-    ///     Token::Map { len: Some(2) },
-    ///     Token::Char('A'),
-    ///     Token::I32(65),
-    ///     Token::Char('Z'),
-    ///     Token::I32(90),
-    ///     Token::MapEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &map,
+    ///     &[
+    ///         Token::Map { len: Some(2) },
+    ///         Token::Char('A'),
+    ///         Token::I32(65),
+    ///         Token::Char('Z'),
+    ///         Token::I32(90),
+    ///         Token::MapEnd,
+    ///     ],
+    /// );
     /// ```
     Map { len: Option<usize> },
 
@@ -399,8 +427,8 @@ pub enum Token {
     ///
     /// After this header are the fields of the struct, followed by `StructEnd`.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -411,14 +439,17 @@ pub enum Token {
     /// }
     ///
     /// let s = S { a: 0, b: 0 };
-    /// assert_tokens(&s, &[
-    ///     Token::Struct { name: "S", len: 2 },
-    ///     Token::Str("a"),
-    ///     Token::U8(0),
-    ///     Token::Str("b"),
-    ///     Token::U8(0),
-    ///     Token::StructEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &s,
+    ///     &[
+    ///         Token::Struct { name: "S", len: 2 },
+    ///         Token::Str("a"),
+    ///         Token::U8(0),
+    ///         Token::Str("b"),
+    ///         Token::U8(0),
+    ///         Token::StructEnd,
+    ///     ],
+    /// );
     /// # }
     /// ```
     Struct { name: &'static str, len: usize },
@@ -431,8 +462,8 @@ pub enum Token {
     /// After this header are the fields of the struct variant, followed by
     /// `StructVariantEnd`.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -442,12 +473,19 @@ pub enum Token {
     /// }
     ///
     /// let d = E::D { d: 0 };
-    /// assert_tokens(&d, &[
-    ///     Token::StructVariant { name: "E", variant: "D", len: 1 },
-    ///     Token::Str("d"),
-    ///     Token::U8(0),
-    ///     Token::StructVariantEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &d,
+    ///     &[
+    ///         Token::StructVariant {
+    ///             name: "E",
+    ///             variant: "D",
+    ///             len: 1,
+    ///         },
+    ///         Token::Str("d"),
+    ///         Token::U8(0),
+    ///         Token::StructVariantEnd,
+    ///     ],
+    /// );
     /// # }
     /// ```
     StructVariant {
@@ -461,8 +499,8 @@ pub enum Token {
 
     /// The header to an enum of the given name.
     ///
-    /// ```edition2018
-    /// # use serde::{Serialize, Deserialize};
+    /// ```edition2021
+    /// # use serde_derive::{Deserialize, Serialize};
     /// # use serde_test::{assert_tokens, Token};
     /// #
     /// # fn main() {
@@ -475,38 +513,42 @@ pub enum Token {
     /// }
     ///
     /// let a = E::A;
-    /// assert_tokens(&a, &[
-    ///     Token::Enum { name: "E" },
-    ///     Token::Str("A"),
-    ///     Token::Unit,
-    /// ]);
+    /// assert_tokens(
+    ///     &a,
+    ///     &[Token::Enum { name: "E" }, Token::Str("A"), Token::Unit],
+    /// );
     ///
     /// let b = E::B(0);
-    /// assert_tokens(&b, &[
-    ///     Token::Enum { name: "E" },
-    ///     Token::Str("B"),
-    ///     Token::U8(0),
-    /// ]);
+    /// assert_tokens(
+    ///     &b,
+    ///     &[Token::Enum { name: "E" }, Token::Str("B"), Token::U8(0)],
+    /// );
     ///
     /// let c = E::C(0, 0);
-    /// assert_tokens(&c, &[
-    ///     Token::Enum { name: "E" },
-    ///     Token::Str("C"),
-    ///     Token::Seq { len: Some(2) },
-    ///     Token::U8(0),
-    ///     Token::U8(0),
-    ///     Token::SeqEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &c,
+    ///     &[
+    ///         Token::Enum { name: "E" },
+    ///         Token::Str("C"),
+    ///         Token::Seq { len: Some(2) },
+    ///         Token::U8(0),
+    ///         Token::U8(0),
+    ///         Token::SeqEnd,
+    ///     ],
+    /// );
     ///
     /// let d = E::D { d: 0 };
-    /// assert_tokens(&d, &[
-    ///     Token::Enum { name: "E" },
-    ///     Token::Str("D"),
-    ///     Token::Map { len: Some(1) },
-    ///     Token::Str("d"),
-    ///     Token::U8(0),
-    ///     Token::MapEnd,
-    /// ]);
+    /// assert_tokens(
+    ///     &d,
+    ///     &[
+    ///         Token::Enum { name: "E" },
+    ///         Token::Str("D"),
+    ///         Token::Map { len: Some(1) },
+    ///         Token::Str("d"),
+    ///         Token::U8(0),
+    ///         Token::MapEnd,
+    ///     ],
+    /// );
     /// # }
     /// ```
     Enum { name: &'static str },

test_suite/Cargo.toml

@@ -12,7 +12,7 @@ unstable = ["serde/unstable"]
 serde = { path = "../serde" }
 
 [dev-dependencies]
-automod = "1.0"
+automod = "1.0.1"
 fnv = "1.0"
 rustversion = "1.0"
 serde = { path = "../serde", features = ["rc", "derive"] }

test_suite/no_std/src/main.rs

@@ -19,7 +19,7 @@ fn panic(_info: &core::panic::PanicInfo) -> ! {
 
 //////////////////////////////////////////////////////////////////////////////
 
-use serde::{Serialize, Deserialize};
+use serde::{Deserialize, Serialize};
 
 #[derive(Serialize, Deserialize)]
 struct Unit;

test_suite/tests/regression/issue2409.rs

@@ -0,0 +1,11 @@
+use serde::Deserialize;
+
+macro_rules! bug {
+    ($serde_path:literal) => {
+        #[derive(Deserialize)]
+        #[serde(crate = $serde_path)]
+        pub struct Struct;
+    };
+}
+
+bug!("serde");

test_suite/tests/regression/issue2415.rs

@@ -0,0 +1,5 @@
+use serde_derive::Serialize;
+
+#[derive(Serialize)]
+#[serde()]
+pub struct S;

test_suite/tests/test_annotations.rs

@@ -10,7 +10,7 @@
     clippy::uninlined_format_args,
 )]
 
-use serde::de::{self, MapAccess, Unexpected, Visitor};
+use serde::de::{self, IgnoredAny, MapAccess, Unexpected, Visitor};
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
 use std::collections::{BTreeMap, HashMap};
@@ -1533,7 +1533,7 @@ fn test_invalid_length_enum() {
             Token::TupleVariant {
                 name: "InvalidLengthEnum",
                 variant: "B",
-                len: 3,
+                len: 2,
             },
             Token::I32(1),
             Token::TupleVariantEnd,
@@ -2317,6 +2317,53 @@ fn test_internally_tagged_enum_new_type_with_unit() {
     );
 }
 
+#[test]
+fn test_adjacently_tagged_enum_bytes() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(tag = "t", content = "c")]
+    enum Data {
+        A { a: i32 },
+    }
+
+    let data = Data::A { a: 0 };
+
+    assert_tokens(
+        &data,
+        &[
+            Token::Struct {
+                name: "Data",
+                len: 2,
+            },
+            Token::Str("t"),
+            Token::Str("A"),
+            Token::Str("c"),
+            Token::Struct { name: "A", len: 1 },
+            Token::Str("a"),
+            Token::I32(0),
+            Token::StructEnd,
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &data,
+        &[
+            Token::Struct {
+                name: "Data",
+                len: 2,
+            },
+            Token::Bytes(b"t"),
+            Token::Str("A"),
+            Token::Bytes(b"c"),
+            Token::Struct { name: "A", len: 1 },
+            Token::Str("a"),
+            Token::I32(0),
+            Token::StructEnd,
+            Token::StructEnd,
+        ],
+    );
+}
+
 #[test]
 fn test_adjacently_tagged_enum_containing_flatten() {
     #[derive(Serialize, Deserialize, PartialEq, Debug)]
@@ -2395,6 +2442,162 @@ fn test_untagged_enum_containing_flatten() {
     );
 }
 
+#[test]
+fn test_partially_untagged_enum() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    enum Exp {
+        Lambda(u32, Box<Exp>),
+        #[serde(untagged)]
+        App(Box<Exp>, Box<Exp>),
+        #[serde(untagged)]
+        Var(u32),
+    }
+    use Exp::*;
+
+    let data = Lambda(0, Box::new(App(Box::new(Var(0)), Box::new(Var(0)))));
+    assert_tokens(
+        &data,
+        &[
+            Token::TupleVariant {
+                name: "Exp",
+                variant: "Lambda",
+                len: 2,
+            },
+            Token::U32(0),
+            Token::Tuple { len: 2 },
+            Token::U32(0),
+            Token::U32(0),
+            Token::TupleEnd,
+            Token::TupleVariantEnd,
+        ],
+    );
+}
+
+#[test]
+fn test_partially_untagged_enum_generic() {
+    trait Trait<T> {
+        type Assoc;
+        type Assoc2;
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    enum E<A, B, C>
+    where
+        A: Trait<C, Assoc2 = B>,
+    {
+        A(A::Assoc),
+        #[serde(untagged)]
+        B(A::Assoc2),
+    }
+
+    impl<T> Trait<T> for () {
+        type Assoc = T;
+        type Assoc2 = bool;
+    }
+
+    type MyE = E<(), bool, u32>;
+    use E::*;
+
+    assert_tokens::<MyE>(&B(true), &[Token::Bool(true)]);
+
+    assert_tokens::<MyE>(
+        &A(5),
+        &[
+            Token::NewtypeVariant {
+                name: "E",
+                variant: "A",
+            },
+            Token::U32(5),
+        ],
+    );
+}
+
+#[test]
+fn test_partially_untagged_enum_desugared() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    enum Test {
+        A(u32, u32),
+        B(u32),
+        #[serde(untagged)]
+        C(u32),
+        #[serde(untagged)]
+        D(u32, u32),
+    }
+    use Test::*;
+
+    mod desugared {
+        use super::*;
+        #[derive(Serialize, Deserialize, PartialEq, Debug)]
+        pub(super) enum Test {
+            A(u32, u32),
+            B(u32),
+        }
+    }
+    use desugared::Test as TestTagged;
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(untagged)]
+    enum TestUntagged {
+        Tagged(TestTagged),
+        C(u32),
+        D(u32, u32),
+    }
+
+    impl From<Test> for TestUntagged {
+        fn from(test: Test) -> Self {
+            match test {
+                A(x, y) => TestUntagged::Tagged(TestTagged::A(x, y)),
+                B(x) => TestUntagged::Tagged(TestTagged::B(x)),
+                C(x) => TestUntagged::C(x),
+                D(x, y) => TestUntagged::D(x, y),
+            }
+        }
+    }
+
+    fn assert_tokens_desugared(value: Test, tokens: &[Token]) {
+        assert_tokens(&value, tokens);
+        let desugared: TestUntagged = value.into();
+        assert_tokens(&desugared, tokens);
+    }
+
+    assert_tokens_desugared(
+        A(0, 1),
+        &[
+            Token::TupleVariant {
+                name: "Test",
+                variant: "A",
+                len: 2,
+            },
+            Token::U32(0),
+            Token::U32(1),
+            Token::TupleVariantEnd,
+        ],
+    );
+
+    assert_tokens_desugared(
+        B(1),
+        &[
+            Token::NewtypeVariant {
+                name: "Test",
+                variant: "B",
+            },
+            Token::U32(1),
+        ],
+    );
+
+    assert_tokens_desugared(C(2), &[Token::U32(2)]);
+
+    assert_tokens_desugared(
+        D(3, 5),
+        &[
+            Token::Tuple { len: 2 },
+            Token::U32(3),
+            Token::U32(5),
+            Token::TupleEnd,
+        ],
+    );
+}
+
 #[test]
 fn test_flatten_untagged_enum() {
     #[derive(Serialize, Deserialize, PartialEq, Debug)]
@@ -2494,6 +2697,31 @@ fn test_flatten_option() {
     );
 }
 
+#[test]
+fn test_flatten_ignored_any() {
+    #[derive(Deserialize, PartialEq, Debug)]
+    struct Outer {
+        #[serde(flatten)]
+        inner: IgnoredAny,
+    }
+
+    assert_de_tokens(
+        &Outer { inner: IgnoredAny },
+        &[Token::Map { len: None }, Token::MapEnd],
+    );
+
+    assert_de_tokens(
+        &Outer { inner: IgnoredAny },
+        &[
+            Token::Struct {
+                name: "DoNotMatter",
+                len: 0,
+            },
+            Token::StructEnd,
+        ],
+    );
+}
+
 #[test]
 fn test_transparent_struct() {
     #[derive(Serialize, Deserialize, PartialEq, Debug)]

test_suite/tests/test_borrow.rs

@@ -4,6 +4,8 @@
     clippy::used_underscore_binding
 )]
 
+use serde::de::value::{BorrowedStrDeserializer, MapDeserializer};
+use serde::de::IntoDeserializer;
 use serde::{Deserialize, Deserializer};
 use serde_test::{assert_de_tokens, assert_de_tokens_error, Token};
 
@@ -130,20 +132,22 @@ fn test_cow() {
         borrowed: Cow<'b, str>,
     }
 
-    let tokens = &[
-        Token::Struct {
-            name: "Cows",
-            len: 2,
-        },
-        Token::Str("copied"),
-        Token::BorrowedStr("copied"),
-        Token::Str("borrowed"),
-        Token::BorrowedStr("borrowed"),
-        Token::StructEnd,
-    ];
+    struct BorrowedStr(&'static str);
 
-    let mut de = serde_test::Deserializer::new(tokens);
-    let cows = Cows::deserialize(&mut de).unwrap();
+    impl<'de> IntoDeserializer<'de> for BorrowedStr {
+        type Deserializer = BorrowedStrDeserializer<'de, serde::de::value::Error>;
+
+        fn into_deserializer(self) -> Self::Deserializer {
+            BorrowedStrDeserializer::new(self.0)
+        }
+    }
+
+    let de = MapDeserializer::new(IntoIterator::into_iter([
+        ("copied", BorrowedStr("copied")),
+        ("borrowed", BorrowedStr("borrowed")),
+    ]));
+
+    let cows = Cows::deserialize(de).unwrap();
 
     match cows.copied {
         Cow::Owned(ref s) if s == "copied" => {}

test_suite/tests/test_de.rs

@@ -14,6 +14,7 @@ use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
 use std::default::Default;
 use std::ffi::{CStr, CString, OsString};
 use std::fmt::Debug;
+use std::iter;
 use std::net;
 use std::num::{
     NonZeroI128, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI8, NonZeroIsize, NonZeroU128,
@@ -33,7 +34,7 @@ use std::time::{Duration, UNIX_EPOCH};
 use std::sync::atomic::{AtomicI64, AtomicU64};
 
 use fnv::FnvHasher;
-use serde::de::DeserializeOwned;
+use serde::de::{DeserializeOwned, IntoDeserializer};
 use serde::{Deserialize, Deserializer};
 use serde_test::{assert_de_tokens, Configure, Token};
 
@@ -199,12 +200,11 @@ fn assert_de_tokens_ignore(ignorable_tokens: &[Token]) {
     ]
     .into_iter()
     .chain(ignorable_tokens.iter().copied())
-    .chain(vec![Token::MapEnd].into_iter())
+    .chain(iter::once(Token::MapEnd))
     .collect();
 
-    let mut de = serde_test::Deserializer::new(&concated_tokens);
-    let base = IgnoreBase::deserialize(&mut de).unwrap();
-    assert_eq!(base, IgnoreBase { a: 1 });
+    let expected = IgnoreBase { a: 1 };
+    assert_de_tokens(&expected, &concated_tokens);
 }
 
 //////////////////////////////////////////////////////////////////////////
@@ -2245,39 +2245,34 @@ fn test_cstr() {
 
 #[test]
 fn test_atomics() {
-    fn test<L, A, T>(load: L, val: T, token: Token)
+    fn test<L, A, T>(load: L, val: T)
     where
         L: Fn(&A, Ordering) -> T,
         A: DeserializeOwned,
-        T: PartialEq + Debug,
+        T: PartialEq + Debug + Copy + for<'de> IntoDeserializer<'de>,
     {
-        let tokens = &[token];
-        let mut de = serde_test::Deserializer::new(tokens);
-        match A::deserialize(&mut de) {
+        match A::deserialize(val.into_deserializer()) {
             Ok(v) => {
                 let loaded = load(&v, Ordering::Relaxed);
                 assert_eq!(val, loaded);
             }
             Err(e) => panic!("tokens failed to deserialize: {}", e),
-        };
-        if de.remaining() > 0 {
-            panic!("{} remaining tokens", de.remaining());
         }
     }
 
-    test(AtomicBool::load, true, Token::Bool(true));
-    test(AtomicI8::load, -127, Token::I8(-127i8));
-    test(AtomicI16::load, -510, Token::I16(-510i16));
-    test(AtomicI32::load, -131072, Token::I32(-131072i32));
-    test(AtomicIsize::load, -131072isize, Token::I32(-131072));
-    test(AtomicU8::load, 127, Token::U8(127u8));
-    test(AtomicU16::load, 510u16, Token::U16(510u16));
-    test(AtomicU32::load, 131072u32, Token::U32(131072u32));
-    test(AtomicUsize::load, 131072usize, Token::U32(131072));
+    test(AtomicBool::load, true);
+    test(AtomicI8::load, -127i8);
+    test(AtomicI16::load, -510i16);
+    test(AtomicI32::load, -131072i32);
+    test(AtomicIsize::load, -131072isize);
+    test(AtomicU8::load, 127u8);
+    test(AtomicU16::load, 510u16);
+    test(AtomicU32::load, 131072u32);
+    test(AtomicUsize::load, 131072usize);
 
     #[cfg(target_arch = "x86_64")]
     {
-        test(AtomicI64::load, -8589934592, Token::I64(-8589934592));
-        test(AtomicU64::load, 8589934592u64, Token::U64(8589934592));
+        test(AtomicI64::load, -8589934592i64);
+        test(AtomicU64::load, 8589934592u64);
     }
 }

test_suite/tests/test_macros.rs

@@ -1267,6 +1267,38 @@ fn test_adjacently_tagged_enum() {
             Token::StructEnd,
         ],
     );
+
+    // integer field keys
+    assert_de_tokens(
+        &AdjacentlyTagged::Newtype::<u8>(1),
+        &[
+            Token::Struct {
+                name: "AdjacentlyTagged",
+                len: 2,
+            },
+            Token::U64(1), // content field
+            Token::U8(1),
+            Token::U64(0), // tag field
+            Token::Str("Newtype"),
+            Token::StructEnd,
+        ],
+    );
+
+    // byte-array field keys
+    assert_de_tokens(
+        &AdjacentlyTagged::Newtype::<u8>(1),
+        &[
+            Token::Struct {
+                name: "AdjacentlyTagged",
+                len: 2,
+            },
+            Token::Bytes(b"c"),
+            Token::U8(1),
+            Token::Bytes(b"t"),
+            Token::Str("Newtype"),
+            Token::StructEnd,
+        ],
+    );
 }
 
 #[test]
@@ -1330,6 +1362,32 @@ fn test_adjacently_tagged_enum_deny_unknown_fields() {
         ],
         r#"invalid value: string "h", expected "t" or "c""#,
     );
+
+    assert_de_tokens_error::<AdjacentlyTagged>(
+        &[
+            Token::Struct {
+                name: "AdjacentlyTagged",
+                len: 2,
+            },
+            Token::U64(0), // tag field
+            Token::Str("Unit"),
+            Token::U64(3),
+        ],
+        r#"invalid value: integer `3`, expected "t" or "c""#,
+    );
+
+    assert_de_tokens_error::<AdjacentlyTagged>(
+        &[
+            Token::Struct {
+                name: "AdjacentlyTagged",
+                len: 2,
+            },
+            Token::Bytes(b"c"),
+            Token::Unit,
+            Token::Bytes(b"h"),
+        ],
+        r#"invalid value: byte array, expected "t" or "c""#,
+    );
 }
 
 #[test]

test_suite/tests/ui/enum-representation/partially_tagged_wrong_order.rs

@@ -0,0 +1,10 @@
+use serde_derive::Serialize;
+
+#[derive(Serialize)]
+enum E {
+    #[serde(untagged)]
+    A(u8),
+    B(String),
+}
+
+fn main() {}

test_suite/tests/ui/enum-representation/partially_tagged_wrong_order.stderr

@@ -0,0 +1,5 @@
+error: all variants with the #[serde(untagged)] attribute must be placed at the end of the enum
+ --> tests/ui/enum-representation/partially_tagged_wrong_order.rs:6:5
+  |
+6 |     A(u8),
+  |     ^

test_suite/tests/ui/remote/missing_field.rs

@@ -1,4 +1,4 @@
-use serde_derive::{Serialize, Deserialize};
+use serde_derive::{Deserialize, Serialize};
 
 mod remote {
     pub struct S {

test_suite/tests/ui/remote/unknown_field.rs

@@ -1,4 +1,4 @@
-use serde_derive::{Serialize, Deserialize};
+use serde_derive::{Deserialize, Serialize};
 
 mod remote {
     pub struct S {