Release 1.0.221

Merge pull request #2975 from dtolnay/integer128
Deprecate serde_if_integer128 macro
2026-04-23 03:38:00 +00:00 · 2025-09-13 17:25:20 -07:00 · 2025-09-13 17:25:14 -07:00 · 2025-09-13 17:19:10 -07:00 · 2025-09-13 17:12:58 -07:00 · 2025-09-13 17:12:51 -07:00
73 changed files with 2038 additions and 874 deletions
@@ -55,7 +55,7 @@ jobs:
      - run: cd test_suite/no_std && cargo build

  nightly:
-    name: Rust nightly ${{matrix.os == 'windows' && '(windows)' || ''}}
+    name: Rust nightly${{matrix.os == 'windows' && ' (windows)' || ''}}
    runs-on: ${{matrix.os}}-latest
    strategy:
      fail-fast: false
@@ -70,7 +70,7 @@ jobs:
      - run: cd serde && cargo build --no-default-features --features alloc
      - run: cd serde && cargo build --no-default-features --features rc,alloc
      - run: cd serde && cargo build --no-default-features --features unstable
-      - run: cd serde && cargo test --features derive,rc,unstable
+      - run: cd serde_core && cargo test --features rc,unstable
      - run: cd test_suite/no_std && cargo build
        if: matrix.os != 'windows'
      - run: cd serde_derive && cargo check --tests
@@ -84,7 +84,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        rust: [1.31.0, 1.34.0]
+        rust: [1.56.0, 1.60.0]
    timeout-minutes: 45
    steps:
      - uses: actions/checkout@v4
@@ -94,6 +94,7 @@ jobs:
      - run: sed -i '/"test_suite"/d' Cargo.toml
      - run: cd serde && cargo build --features rc
      - run: cd serde && cargo build --no-default-features
+      - run: cd serde && cargo build --no-default-features --features alloc
      - run: cd serde && cargo build

  derive:
@@ -111,16 +112,6 @@ jobs:
      - run: cd serde && cargo check
      - run: cd serde_derive && cargo check

-  alloc:
-    name: Rust 1.36.0
-    runs-on: ubuntu-latest
-    timeout-minutes: 45
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@1.36.0
-      - run: sed -i '/"test_suite"/d' Cargo.toml
-      - run: cd serde && cargo build --no-default-features --features alloc
-
  minimal:
    name: Minimal versions
    runs-on: ubuntu-latest
@@ -154,6 +145,7 @@ jobs:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@clippy
      - run: cd serde && cargo clippy --features rc,unstable -- -Dclippy::all -Dclippy::pedantic
+      - run: cd serde_core && cargo clippy --features rc,unstable -- -Dclippy::all -Dclippy::pedantic
      - run: cd serde_derive && cargo clippy -- -Dclippy::all -Dclippy::pedantic
      - run: cd serde_derive_internals && cargo clippy -- -Dclippy::all -Dclippy::pedantic
      - run: cd test_suite && cargo clippy --tests --features unstable -- -Dclippy::all -Dclippy::pedantic
@@ -166,8 +158,10 @@ jobs:
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@miri
+        with:
+          toolchain: nightly-2025-05-16  # https://github.com/rust-lang/miri/issues/4323
      - run: cargo miri setup
-      - run: cd serde && cargo miri test --features derive,rc,unstable
+      - run: cd serde_core && cargo miri test --features rc,unstable
        env:
          MIRIFLAGS: -Zmiri-strict-provenance
      - run: cd test_suite && cargo miri test --features unstable
@@ -1,13 +1,16 @@
 [workspace]
 members = [
    "serde",
+    "serde_core",
    "serde_derive",
    "serde_derive_internals",
    "test_suite",
 ]
+resolver = "2"

 [patch.crates-io]
 serde = { path = "serde" }
+serde_core = { path = "serde_core" }

 [workspace.dependencies]
 proc-macro2 = { version = "1.0.74", default-features = false }
@@ -1,4 +1,4 @@
-# Serde &emsp; [![Build Status]][actions] [![Latest Version]][crates.io] [![serde msrv]][Rust 1.31] [![serde_derive msrv]][Rust 1.61]
+# Serde &emsp; [![Build Status]][actions] [![Latest Version]][crates.io] [![serde msrv]][Rust 1.56] [![serde_derive msrv]][Rust 1.61]

 [Build Status]: https://img.shields.io/github/actions/workflow/status/serde-rs/serde/ci.yml?branch=master
 [actions]: https://github.com/serde-rs/serde/actions?query=branch%3Amaster
@@ -6,7 +6,7 @@
 [crates.io]: https://crates.io/crates/serde
 [serde msrv]: https://img.shields.io/crates/msrv/serde.svg?label=serde%20msrv&color=lightgray
 [serde_derive msrv]: https://img.shields.io/crates/msrv/serde_derive.svg?label=serde_derive%20msrv&color=lightgray
-[Rust 1.31]: https://blog.rust-lang.org/2018/12/06/Rust-1.31-and-rust-2018.html
+[Rust 1.56]: https://blog.rust-lang.org/2021/10/21/Rust-1.56.0.html
 [Rust 1.61]: https://blog.rust-lang.org/2022/05/19/Rust-1.61.0.html

 **Serde is a framework for *ser*ializing and *de*serializing Rust data structures efficiently and generically.**
@@ -15,7 +15,7 @@

 You may be looking for:

- [An overview of Serde](https://serde.rs/)
+- [An overview of Serde](https://serde.rs)
 - [Data formats supported by Serde](https://serde.rs/#data-formats)
 - [Setting up `#[derive(Serialize, Deserialize)]`](https://serde.rs/derive.html)
 - [Examples](https://serde.rs/examples.html)
@@ -27,7 +27,7 @@ You may be looking for:
 <details>
 <summary>
 Click to show Cargo.toml.
-<a href="https://play.rust-lang.org/?edition=2018&gist=72755f28f99afc95e01d63174b28c1f5" target="_blank">Run this code in the playground.</a>
+<a href="https://play.rust-lang.org/?edition=2021&gist=72755f28f99afc95e01d63174b28c1f5" target="_blank">Run this code in the playground.</a>
 </summary>

 ```toml
@@ -6,7 +6,7 @@

 You may be looking for:

- [An overview of Serde](https://serde.rs/)
+- [An overview of Serde](https://serde.rs)
 - [Data formats supported by Serde](https://serde.rs/#data-formats)
 - [Setting up `#[derive(Serialize, Deserialize)]`](https://serde.rs/derive.html)
 - [Examples](https://serde.rs/examples.html)
@@ -1,25 +1,23 @@
 [package]
 name = "serde"
-version = "1.0.218"
+version = "1.0.221"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
 categories = ["encoding", "no-std", "no-std::no-alloc"]
 description = "A generic serialization/deserialization framework"
 documentation = "https://docs.rs/serde"
-edition = "2018"
+edition = "2021"
 homepage = "https://serde.rs"
 keywords = ["serde", "serialization", "no_std"]
 license = "MIT OR Apache-2.0"
 readme = "crates-io.md"
 repository = "https://github.com/serde-rs/serde"
-rust-version = "1.31"
+rust-version = "1.56"

 [dependencies]
+serde_core = { version = "=1.0.221", path = "../serde_core", default-features = false, features = ["result"] }
 serde_derive = { version = "1", optional = true, path = "../serde_derive" }

-[dev-dependencies]
-serde_derive = { version = "1", path = "../serde_derive" }
-
 [package.metadata.playground]
 features = ["derive", "rc"]

@@ -33,14 +31,6 @@ rustdoc-args = [
    "--extern-html-root-url=std=https://doc.rust-lang.org",
 ]

-# This cfg cannot be enabled, but it still forces Cargo to keep serde_derive's
-# version in lockstep with serde's, even if someone depends on the two crates
-# separately with serde's "derive" feature disabled. Every serde_derive release
-# is compatible with exactly one serde release because the generated code
-# involves nonpublic APIs which are not bound by semver.
-[target.'cfg(any())'.dependencies]
-serde_derive = { version = "=1.0.218", path = "../serde_derive" }
-

 ### FEATURES #################################################################

@@ -52,20 +42,20 @@ derive = ["serde_derive"]

 # Provide impls for common standard library types like Vec<T> and HashMap<K, V>.
 # Requires a dependency on the Rust standard library.
-std = []
+std = ["serde_core/std"]

 # Provide impls for types that require unstable functionality. For tracking and
 # discussion of unstable functionality please refer to this issue:
 #
 #    https://github.com/serde-rs/serde/issues/812
-unstable = []
+unstable = ["serde_core/unstable"]

 # Provide impls for types in the Rust core allocation and collections library
 # including String, Box<T>, Vec<T>, and Cow<T>. This is a subset of std but may
 # be enabled without depending on all of std.
-alloc = []
+alloc = ["serde_core/alloc"]

 # Opt into impls for Rc<T> and Arc<T>. Serializing and deserializing these types
 # does not preserve identity and may result in multiple copies of the same data.
 # Be sure that this is what you want before enabling this feature.
-rc = []
+rc = ["serde_core/rc"]
@@ -14,97 +14,13 @@ fn main() {
    };

    if minor >= 77 {
-        println!("cargo:rustc-check-cfg=cfg(no_core_cstr)");
-        println!("cargo:rustc-check-cfg=cfg(no_core_error)");
-        println!("cargo:rustc-check-cfg=cfg(no_core_net)");
-        println!("cargo:rustc-check-cfg=cfg(no_core_num_saturating)");
-        println!("cargo:rustc-check-cfg=cfg(no_core_try_from)");
-        println!("cargo:rustc-check-cfg=cfg(no_diagnostic_namespace)");
-        println!("cargo:rustc-check-cfg=cfg(no_float_copysign)");
-        println!("cargo:rustc-check-cfg=cfg(no_num_nonzero_signed)");
-        println!("cargo:rustc-check-cfg=cfg(no_relaxed_trait_bounds)");
        println!("cargo:rustc-check-cfg=cfg(no_serde_derive)");
-        println!("cargo:rustc-check-cfg=cfg(no_std_atomic)");
-        println!("cargo:rustc-check-cfg=cfg(no_std_atomic64)");
-        println!("cargo:rustc-check-cfg=cfg(no_systemtime_checked_add)");
-        println!("cargo:rustc-check-cfg=cfg(no_target_has_atomic)");
-    }
-
-    let target = env::var("TARGET").unwrap();
-    let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
-
-    // TryFrom, Atomic types, non-zero signed integers, and SystemTime::checked_add
-    // stabilized in Rust 1.34:
-    // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#tryfrom-and-tryinto
-    // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#library-stabilizations
-    if minor < 34 {
-        println!("cargo:rustc-cfg=no_core_try_from");
-        println!("cargo:rustc-cfg=no_num_nonzero_signed");
-        println!("cargo:rustc-cfg=no_systemtime_checked_add");
-        println!("cargo:rustc-cfg=no_relaxed_trait_bounds");
-    }
-
-    // f32::copysign and f64::copysign stabilized in Rust 1.35.
-    // https://blog.rust-lang.org/2019/05/23/Rust-1.35.0.html#copy-the-sign-of-a-floating-point-number-onto-another
-    if minor < 35 {
-        println!("cargo:rustc-cfg=no_float_copysign");
-    }
-
-    // Support for #[cfg(target_has_atomic = "...")] stabilized in Rust 1.60.
-    if minor < 60 {
-        println!("cargo:rustc-cfg=no_target_has_atomic");
-        // Allowlist of archs that support std::sync::atomic module. This is
-        // based on rustc's compiler/rustc_target/src/spec/*.rs.
-        let has_atomic64 = target.starts_with("x86_64")
-            || target.starts_with("i686")
-            || target.starts_with("aarch64")
-            || target.starts_with("powerpc64")
-            || target.starts_with("sparc64")
-            || target.starts_with("mips64el")
-            || target.starts_with("riscv64");
-        let has_atomic32 = has_atomic64 || emscripten;
-        if minor < 34 || !has_atomic64 {
-            println!("cargo:rustc-cfg=no_std_atomic64");
-        }
-        if minor < 34 || !has_atomic32 {
-            println!("cargo:rustc-cfg=no_std_atomic");
-        }
    }

    // Current minimum supported version of serde_derive crate is Rust 1.61.
    if minor < 61 {
        println!("cargo:rustc-cfg=no_serde_derive");
    }
-
-    // Support for core::ffi::CStr and alloc::ffi::CString stabilized in Rust 1.64.
-    // https://blog.rust-lang.org/2022/09/22/Rust-1.64.0.html#c-compatible-ffi-types-in-core-and-alloc
-    if minor < 64 {
-        println!("cargo:rustc-cfg=no_core_cstr");
-    }
-
-    // Support for core::num::Saturating and std::num::Saturating stabilized in Rust 1.74
-    // https://blog.rust-lang.org/2023/11/16/Rust-1.74.0.html#stabilized-apis
-    if minor < 74 {
-        println!("cargo:rustc-cfg=no_core_num_saturating");
-    }
-
-    // Support for core::net stabilized in Rust 1.77.
-    // https://blog.rust-lang.org/2024/03/21/Rust-1.77.0.html
-    if minor < 77 {
-        println!("cargo:rustc-cfg=no_core_net");
-    }
-
-    // Support for the `#[diagnostic]` tool attribute namespace
-    // https://blog.rust-lang.org/2024/05/02/Rust-1.78.0.html#diagnostic-attributes
-    if minor < 78 {
-        println!("cargo:rustc-cfg=no_diagnostic_namespace");
-    }
-
-    // The Error trait became available in core in 1.81.
-    // https://blog.rust-lang.org/2024/09/05/Rust-1.81.0.html#coreerrorerror
-    if minor < 81 {
-        println!("cargo:rustc-cfg=no_core_error");
-    }
 }

 fn rustc_minor_version() -> Option<u32> {
@@ -1,6 +1,11 @@
-// No longer used. Old versions of serde used this macro for supporting targets
-// that did not yet have 128-bit integer support.
 #[macro_export]
+#[deprecated = "
+This macro has no effect on any version of Serde released in the past 2 years.
+It was used long ago in crates that needed to support Rustc older than 1.26.0,
+or Emscripten targets older than 1.40.0, which did not yet have 128-bit integer
+support. These days Serde requires a Rust compiler newer than that so 128-bit
+integers are always supported.
+"]
 #[doc(hidden)]
 macro_rules! serde_if_integer128 {
    ($($tt:tt)*) => {
@@ -9,7 +9,7 @@
 //! these two groups interact with each other, allowing any supported data
 //! structure to be serialized and deserialized using any supported data format.
 //!
-//! See the Serde website <https://serde.rs/> for additional documentation and
+//! See the Serde website <https://serde.rs> for additional documentation and
 //! usage examples.
 //!
 //! ## Design
@@ -95,7 +95,7 @@
 ////////////////////////////////////////////////////////////////////////////////

 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.218")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.221")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Show which crate feature enables conditionally compiled APIs in documentation.
@@ -106,7 +106,12 @@
 //
 //    https://github.com/serde-rs/serde/issues/812
 #![cfg_attr(feature = "unstable", feature(never_type))]
-#![allow(unknown_lints, bare_trait_objects, deprecated)]
+#![allow(
+    unknown_lints,
+    bare_trait_objects,
+    deprecated,
+    mismatched_lifetime_syntaxes
+)]
 // Ignored clippy and clippy_pedantic lints
 #![allow(
    // clippy bug: https://github.com/rust-lang/rust-clippy/issues/5704
@@ -144,6 +149,7 @@
    clippy::too_many_lines,
    // preference
    clippy::doc_markdown,
+    clippy::elidable_lifetime_names,
    clippy::needless_lifetimes,
    clippy::unseparated_literal_suffix,
    // false positive
@@ -174,25 +180,18 @@ mod lib {
    }

    pub use self::core::{f32, f64};
-    pub use self::core::{i16, i32, i64, i8, isize};
-    pub use self::core::{iter, num, ptr, str};
-    pub use self::core::{u16, u32, u64, u8, usize};
+    pub use self::core::{ptr, str};

    #[cfg(any(feature = "std", feature = "alloc"))]
-    pub use self::core::{cmp, mem, slice};
+    pub use self::core::slice;

-    pub use self::core::cell::{Cell, RefCell};
    pub use self::core::clone;
-    pub use self::core::cmp::Reverse;
    pub use self::core::convert;
    pub use self::core::default;
    pub use self::core::fmt::{self, Debug, Display, Write as FmtWrite};
    pub use self::core::marker::{self, PhantomData};
-    pub use self::core::num::Wrapping;
-    pub use self::core::ops::{Bound, Range, RangeFrom, RangeInclusive, RangeTo};
    pub use self::core::option;
    pub use self::core::result;
-    pub use self::core::time::Duration;

    #[cfg(all(feature = "alloc", not(feature = "std")))]
    pub use alloc::borrow::{Cow, ToOwned};
@@ -213,84 +212,13 @@ mod lib {
    pub use alloc::boxed::Box;
    #[cfg(feature = "std")]
    pub use std::boxed::Box;
-
-    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
-    pub use alloc::rc::{Rc, Weak as RcWeak};
-    #[cfg(all(feature = "rc", feature = "std"))]
-    pub use std::rc::{Rc, Weak as RcWeak};
-
-    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
-    pub use alloc::sync::{Arc, Weak as ArcWeak};
-    #[cfg(all(feature = "rc", feature = "std"))]
-    pub use std::sync::{Arc, Weak as ArcWeak};
-
-    #[cfg(all(feature = "alloc", not(feature = "std")))]
-    pub use alloc::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
-    #[cfg(feature = "std")]
-    pub use std::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
-
-    #[cfg(all(not(no_core_cstr), not(feature = "std")))]
-    pub use self::core::ffi::CStr;
-    #[cfg(feature = "std")]
-    pub use std::ffi::CStr;
-
-    #[cfg(all(not(no_core_cstr), feature = "alloc", not(feature = "std")))]
-    pub use alloc::ffi::CString;
-    #[cfg(feature = "std")]
-    pub use std::ffi::CString;
-
-    #[cfg(all(not(no_core_net), not(feature = "std")))]
-    pub use self::core::net;
-    #[cfg(feature = "std")]
-    pub use std::net;
-
-    #[cfg(feature = "std")]
-    pub use std::error;
-
-    #[cfg(feature = "std")]
-    pub use std::collections::{HashMap, HashSet};
-    #[cfg(feature = "std")]
-    pub use std::ffi::{OsStr, OsString};
-    #[cfg(feature = "std")]
-    pub use std::hash::{BuildHasher, Hash};
-    #[cfg(feature = "std")]
-    pub use std::io::Write;
-    #[cfg(feature = "std")]
-    pub use std::path::{Path, PathBuf};
-    #[cfg(feature = "std")]
-    pub use std::sync::{Mutex, RwLock};
-    #[cfg(feature = "std")]
-    pub use std::time::{SystemTime, UNIX_EPOCH};
-
-    #[cfg(all(feature = "std", no_target_has_atomic, not(no_std_atomic)))]
-    pub use std::sync::atomic::{
-        AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU8,
-        AtomicUsize, Ordering,
-    };
-    #[cfg(all(feature = "std", no_target_has_atomic, not(no_std_atomic64)))]
-    pub use std::sync::atomic::{AtomicI64, AtomicU64};
-
-    #[cfg(all(feature = "std", not(no_target_has_atomic)))]
-    pub use std::sync::atomic::Ordering;
-    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "8"))]
-    pub use std::sync::atomic::{AtomicBool, AtomicI8, AtomicU8};
-    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "16"))]
-    pub use std::sync::atomic::{AtomicI16, AtomicU16};
-    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "32"))]
-    pub use std::sync::atomic::{AtomicI32, AtomicU32};
-    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "64"))]
-    pub use std::sync::atomic::{AtomicI64, AtomicU64};
-    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "ptr"))]
-    pub use std::sync::atomic::{AtomicIsize, AtomicUsize};
-
-    #[cfg(not(no_core_num_saturating))]
-    pub use self::core::num::Saturating;
 }

 // None of this crate's error handling needs the `From::from` error conversion
 // performed implicitly by the `?` operator or the standard library's `try!`
 // macro. This simplified macro gives a 5.5% improvement in compile time
 // compared to standard `try!`, and 9% improvement compared to `?`.
+#[cfg(not(no_serde_derive))]
 macro_rules! tri {
    ($expr:expr) => {
        match $expr {
@@ -302,33 +230,18 @@ macro_rules! tri {

 ////////////////////////////////////////////////////////////////////////////////

-#[macro_use]
-mod macros;
+pub use serde_core::{
+    de, forward_to_deserialize_any, ser, Deserialize, Deserializer, Serialize, Serializer,
+};

 #[macro_use]
 mod integer128;

-pub mod de;
-pub mod ser;
-
-mod format;
-
-#[doc(inline)]
-pub use crate::de::{Deserialize, Deserializer};
-#[doc(inline)]
-pub use crate::ser::{Serialize, Serializer};
-
 // Used by generated code and doc tests. Not public API.
 #[doc(hidden)]
 #[path = "private/mod.rs"]
 pub mod __private;

-#[path = "de/seed.rs"]
-mod seed;
-
-#[cfg(all(not(feature = "std"), no_core_error))]
-mod std_error;
-
 // Re-export #[derive(Serialize, Deserialize)].
 //
 // The reason re-exporting is not enabled by default is that disabling it would
@@ -342,7 +255,8 @@ extern crate serde_derive;
 #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
 pub use serde_derive::{Deserialize, Serialize};

-#[cfg(all(not(no_serde_derive), any(feature = "std", feature = "alloc")))]
-mod actually_private {
-    pub struct T;
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __require_serde_not_serde_core {
+    () => {};
 }
@@ -3,11 +3,8 @@ pub mod de;
 #[cfg(not(no_serde_derive))]
 pub mod ser;

-// FIXME: #[cfg(doctest)] once https://github.com/rust-lang/rust/issues/67295 is fixed.
-pub mod doc;
-
 pub use crate::lib::clone::Clone;
-pub use crate::lib::convert::{From, Into};
+pub use crate::lib::convert::{From, Into, TryFrom};
 pub use crate::lib::default::Default;
 pub use crate::lib::fmt::{self, Formatter};
 pub use crate::lib::marker::PhantomData;
@@ -15,34 +12,7 @@ pub use crate::lib::option::Option::{self, None, Some};
 pub use crate::lib::ptr;
 pub use crate::lib::result::Result::{self, Err, Ok};

-pub use self::string::from_utf8_lossy;
+pub use serde_core::__private::string::from_utf8_lossy;

 #[cfg(any(feature = "alloc", feature = "std"))]
 pub use crate::lib::{ToString, Vec};
-
-#[cfg(not(no_core_try_from))]
-pub use crate::lib::convert::TryFrom;
-
-mod string {
-    use crate::lib::*;
-
-    #[cfg(any(feature = "std", feature = "alloc"))]
-    pub fn from_utf8_lossy(bytes: &[u8]) -> Cow<str> {
-        String::from_utf8_lossy(bytes)
-    }
-
-    // The generated code calls this like:
-    //
-    //     let value = &_serde::__private::from_utf8_lossy(bytes);
-    //     Err(_serde::de::Error::unknown_variant(value, VARIANTS))
-    //
-    // so it is okay for the return type to be different from the std case as long
-    // as the above works.
-    #[cfg(not(any(feature = "std", feature = "alloc")))]
-    pub fn from_utf8_lossy(bytes: &[u8]) -> &str {
-        // Three unicode replacement characters if it fails. They look like a
-        // white-on-black question mark. The user will recognize it as invalid
-        // UTF-8.
-        str::from_utf8(bytes).unwrap_or("\u{fffd}\u{fffd}\u{fffd}")
-    }
-}
@@ -0,0 +1,69 @@
+[package]
+name = "serde_core"
+version = "1.0.221"
+authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
+build = "build.rs"
+categories = ["encoding", "no-std", "no-std::no-alloc"]
+description = "Serde traits only, with no support for derive -- use the `serde` crate instead"
+documentation = "https://docs.rs/serde_core"
+edition = "2021"
+homepage = "https://serde.rs"
+keywords = ["serde", "serialization", "no_std"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/serde-rs/serde"
+rust-version = "1.56"
+
+[dev-dependencies]
+serde = { version = "1", path = "../serde" }
+serde_derive = { version = "1", path = "../serde_derive" }
+
+[package.metadata.playground]
+features = ["rc", "result"]
+
+[package.metadata.docs.rs]
+features = ["rc", "result", "unstable"]
+targets = ["x86_64-unknown-linux-gnu"]
+rustdoc-args = [
+    "--generate-link-to-definition",
+    "--extern-html-root-url=core=https://doc.rust-lang.org",
+    "--extern-html-root-url=alloc=https://doc.rust-lang.org",
+    "--extern-html-root-url=std=https://doc.rust-lang.org",
+]
+
+# This cfg cannot be enabled, but it still forces Cargo to keep serde_derive's
+# version in lockstep with serde's, even if someone depends on the two crates
+# separately with serde's "derive" feature disabled. Every serde_derive release
+# is compatible with exactly one serde release because the generated code
+# involves nonpublic APIs which are not bound by semver.
+[target.'cfg(any())'.dependencies]
+serde_derive = { version = "=1.0.221", path = "../serde_derive" }
+
+
+### FEATURES #################################################################
+
+[features]
+default = ["std", "result"]
+
+# Provide impls for common standard library types like Vec<T> and HashMap<K, V>.
+# Requires a dependency on the Rust standard library.
+std = []
+
+# Provide impls for types that require unstable functionality. For tracking and
+# discussion of unstable functionality please refer to this issue:
+#
+#    https://github.com/serde-rs/serde/issues/812
+unstable = []
+
+# Provide impls for types in the Rust core allocation and collections library
+# including String, Box<T>, Vec<T>, and Cow<T>. This is a subset of std but may
+# be enabled without depending on all of std.
+alloc = []
+
+# Opt into impls for Rc<T> and Arc<T>. Serializing and deserializing these types
+# does not preserve identity and may result in multiple copies of the same data.
+# Be sure that this is what you want before enabling this feature.
+rc = []
+
+# Provide impls for Result<T, E>. Convenient in some contexts but can lead to
+# confusion if ? or unwrap are used incautiously.
+result = []
@@ -0,0 +1 @@
+../LICENSE-APACHE
@@ -0,0 +1 @@
+../LICENSE-MIT
@@ -0,0 +1,28 @@
+The `serde_core` crate contains Serde's trait definitions with **no support for
+#\[derive()\]**.
+
+In crates that derive an implementation of `Serialize` or `Deserialize`, you
+must depend on the [`serde`] crate, not `serde_core`.
+
+[`serde`]: https://crates.io/crates/serde
+
+In crates that handwrite implementations of Serde traits, or only use them as
+trait bounds, depending on `serde_core` is permitted. But `serde` re-exports all
+of these traits and can be used for this use case too. If in doubt, disregard
+`serde_core` and always use `serde`.
+
+Crates that depend on `serde_core` instead of `serde` are able to compile in
+parallel with `serde_derive` even when `serde`'s "derive" feature is turned on,
+as shown in the following build timings.
+
+<br>
+
+| When `serde_json` depends on `serde` |
+|---|
+| <img src="https://github.com/user-attachments/assets/78dc179c-6ab1-4059-928c-1474b0d9d0bb"> |
+
+<br>
+
+| When `serde_json` depends on `serde_core` |
+|---|
+| <img src="https://github.com/user-attachments/assets/6b6cff5e-3e45-4ac7-9db1-d99ee8b9f5f7"> |
@@ -0,0 +1,97 @@
+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,
+    };
+
+    if minor >= 77 {
+        println!("cargo:rustc-check-cfg=cfg(no_core_cstr)");
+        println!("cargo:rustc-check-cfg=cfg(no_core_error)");
+        println!("cargo:rustc-check-cfg=cfg(no_core_net)");
+        println!("cargo:rustc-check-cfg=cfg(no_core_num_saturating)");
+        println!("cargo:rustc-check-cfg=cfg(no_diagnostic_namespace)");
+        println!("cargo:rustc-check-cfg=cfg(no_serde_derive)");
+        println!("cargo:rustc-check-cfg=cfg(no_std_atomic)");
+        println!("cargo:rustc-check-cfg=cfg(no_std_atomic64)");
+        println!("cargo:rustc-check-cfg=cfg(no_target_has_atomic)");
+    }
+
+    let target = env::var("TARGET").unwrap();
+    let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
+
+    // Support for #[cfg(target_has_atomic = "...")] stabilized in Rust 1.60.
+    if minor < 60 {
+        println!("cargo:rustc-cfg=no_target_has_atomic");
+        // Allowlist of archs that support std::sync::atomic module. This is
+        // based on rustc's compiler/rustc_target/src/spec/*.rs.
+        let has_atomic64 = target.starts_with("x86_64")
+            || target.starts_with("i686")
+            || target.starts_with("aarch64")
+            || target.starts_with("powerpc64")
+            || target.starts_with("sparc64")
+            || target.starts_with("mips64el")
+            || target.starts_with("riscv64");
+        let has_atomic32 = has_atomic64 || emscripten;
+        if minor < 34 || !has_atomic64 {
+            println!("cargo:rustc-cfg=no_std_atomic64");
+        }
+        if minor < 34 || !has_atomic32 {
+            println!("cargo:rustc-cfg=no_std_atomic");
+        }
+    }
+
+    // Current minimum supported version of serde_derive crate is Rust 1.61.
+    if minor < 61 {
+        println!("cargo:rustc-cfg=no_serde_derive");
+    }
+
+    // Support for core::ffi::CStr and alloc::ffi::CString stabilized in Rust 1.64.
+    // https://blog.rust-lang.org/2022/09/22/Rust-1.64.0.html#c-compatible-ffi-types-in-core-and-alloc
+    if minor < 64 {
+        println!("cargo:rustc-cfg=no_core_cstr");
+    }
+
+    // Support for core::num::Saturating and std::num::Saturating stabilized in Rust 1.74
+    // https://blog.rust-lang.org/2023/11/16/Rust-1.74.0.html#stabilized-apis
+    if minor < 74 {
+        println!("cargo:rustc-cfg=no_core_num_saturating");
+    }
+
+    // Support for core::net stabilized in Rust 1.77.
+    // https://blog.rust-lang.org/2024/03/21/Rust-1.77.0.html
+    if minor < 77 {
+        println!("cargo:rustc-cfg=no_core_net");
+    }
+
+    // Support for the `#[diagnostic]` tool attribute namespace
+    // https://blog.rust-lang.org/2024/05/02/Rust-1.78.0.html#diagnostic-attributes
+    if minor < 78 {
+        println!("cargo:rustc-cfg=no_diagnostic_namespace");
+    }
+
+    // The Error trait became available in core in 1.81.
+    // https://blog.rust-lang.org/2024/09/05/Rust-1.81.0.html#coreerrorerror
+    if minor < 81 {
+        println!("cargo:rustc-cfg=no_core_error");
+    }
+}
+
+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()
+}
@@ -4,11 +4,10 @@ use crate::de::{
    Deserialize, Deserializer, EnumAccess, Error, MapAccess, SeqAccess, Unexpected, VariantAccess,
    Visitor,
 };
-
-use crate::seed::InPlaceSeed;
+use crate::private::{self, InPlaceSeed};

 #[cfg(any(feature = "std", feature = "alloc"))]
-use crate::de::size_hint;
+use crate::private::size_hint;

 ////////////////////////////////////////////////////////////////////////////////

@@ -80,10 +79,9 @@ impl<'de> Deserialize<'de> for bool {
 ////////////////////////////////////////////////////////////////////////////////

 macro_rules! impl_deserialize_num {
-    ($primitive:ident, $nonzero:ident $(cfg($($cfg:tt)*))*, $deserialize:ident $($method:ident!($($val:ident : $visit:ident)*);)*) => {
+    ($primitive:ident, $nonzero:ident, $deserialize:ident $($method:ident!($($val:ident : $visit:ident)*);)*) => {
        impl_deserialize_num!($primitive, $deserialize $($method!($($val : $visit)*);)*);

-        $(#[cfg($($cfg)*)])*
        impl<'de> Deserialize<'de> for num::$nonzero {
            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
            where
@@ -228,12 +226,12 @@ macro_rules! num_as_copysign_self {
        where
            E: Error,
        {
-            #[cfg(any(no_float_copysign, not(feature = "std")))]
+            #[cfg(not(feature = "std"))]
            {
                Ok(v as Self::Value)
            }

-            #[cfg(all(not(no_float_copysign), feature = "std"))]
+            #[cfg(feature = "std")]
            {
                // Preserve sign of NaN. The `as` produces a nondeterministic sign.
                let sign = if v.is_sign_positive() { 1.0 } else { -1.0 };
@@ -250,13 +248,8 @@ macro_rules! int_to_int {
        where
            E: Error,
        {
-            if Self::Value::min_value() as i64 <= v as i64
-                && v as i64 <= Self::Value::max_value() as i64
-            {
-                Ok(v as Self::Value)
-            } else {
-                Err(Error::invalid_value(Unexpected::Signed(v as i64), &self))
-            }
+            Self::Value::try_from(v as i64)
+                .map_err(|_| Error::invalid_value(Unexpected::Signed(v as i64), &self))
        }
    };

@@ -265,10 +258,8 @@ macro_rules! int_to_int {
        where
            E: Error,
        {
-            if $primitive::min_value() as i64 <= v as i64
-                && v as i64 <= $primitive::max_value() as i64
-            {
-                if let Some(nonzero) = Self::Value::new(v as $primitive) {
+            if let Ok(v) = $primitive::try_from(v as i64) {
+                if let Some(nonzero) = Self::Value::new(v) {
                    return Ok(nonzero);
                }
            }
@@ -299,11 +290,13 @@ macro_rules! int_to_uint {
        where
            E: Error,
        {
-            if 0 <= v && v as u64 <= Self::Value::max_value() as u64 {
-                Ok(v as Self::Value)
-            } else {
-                Err(Error::invalid_value(Unexpected::Signed(v as i64), &self))
+            if 0 <= v {
+                #[allow(irrefutable_let_patterns)]
+                if let Ok(v) = Self::Value::try_from(v as u64) {
+                    return Ok(v as Self::Value);
+                }
            }
+            Err(Error::invalid_value(Unexpected::Signed(v as i64), &self))
        }
    };

@@ -312,9 +305,12 @@ macro_rules! int_to_uint {
        where
            E: Error,
        {
-            if 0 < v && v as u64 <= $primitive::max_value() as u64 {
-                if let Some(nonzero) = Self::Value::new(v as $primitive) {
-                    return Ok(nonzero);
+            if 0 < v {
+                #[allow(irrefutable_let_patterns)]
+                if let Ok(v) = $primitive::try_from(v as u64) {
+                    if let Some(nonzero) = Self::Value::new(v) {
+                        return Ok(nonzero);
+                    }
                }
            }
            Err(Error::invalid_value(Unexpected::Signed(v as i64), &self))
@@ -344,11 +340,8 @@ macro_rules! uint_to_self {
        where
            E: Error,
        {
-            if v as u64 <= Self::Value::max_value() as u64 {
-                Ok(v as Self::Value)
-            } else {
-                Err(Error::invalid_value(Unexpected::Unsigned(v as u64), &self))
-            }
+            Self::Value::try_from(v as u64)
+                .map_err(|_| Error::invalid_value(Unexpected::Unsigned(v as u64), &self))
        }
    };

@@ -357,8 +350,8 @@ macro_rules! uint_to_self {
        where
            E: Error,
        {
-            if v as u64 <= $primitive::max_value() as u64 {
-                if let Some(nonzero) = Self::Value::new(v as $primitive) {
+            if let Ok(v) = $primitive::try_from(v as u64) {
+                if let Some(nonzero) = Self::Value::new(v) {
                    return Ok(nonzero);
                }
            }
@@ -371,7 +364,7 @@ macro_rules! uint_to_self {
        where
            E: Error,
        {
-            if v as u64 <= $primitive::MAX as u64 {
+            if let Ok(v) = $primitive::try_from(v as u64) {
                Ok(Saturating(v as $primitive))
            } else {
                Ok(Saturating($primitive::MAX))
@@ -381,14 +374,14 @@ macro_rules! uint_to_self {
 }

 impl_deserialize_num! {
-    i8, NonZeroI8 cfg(not(no_num_nonzero_signed)), deserialize_i8
+    i8, NonZeroI8, deserialize_i8
    num_self!(i8:visit_i8);
    int_to_int!(i16:visit_i16 i32:visit_i32 i64:visit_i64);
    uint_to_self!(u8:visit_u8 u16:visit_u16 u32:visit_u32 u64:visit_u64);
 }

 impl_deserialize_num! {
-    i16, NonZeroI16 cfg(not(no_num_nonzero_signed)), deserialize_i16
+    i16, NonZeroI16, deserialize_i16
    num_self!(i16:visit_i16);
    num_as_self!(i8:visit_i8);
    int_to_int!(i32:visit_i32 i64:visit_i64);
@@ -396,7 +389,7 @@ impl_deserialize_num! {
 }

 impl_deserialize_num! {
-    i32, NonZeroI32 cfg(not(no_num_nonzero_signed)), deserialize_i32
+    i32, NonZeroI32, deserialize_i32
    num_self!(i32:visit_i32);
    num_as_self!(i8:visit_i8 i16:visit_i16);
    int_to_int!(i64:visit_i64);
@@ -404,14 +397,14 @@ impl_deserialize_num! {
 }

 impl_deserialize_num! {
-    i64, NonZeroI64 cfg(not(no_num_nonzero_signed)), deserialize_i64
+    i64, NonZeroI64, deserialize_i64
    num_self!(i64:visit_i64);
    num_as_self!(i8:visit_i8 i16:visit_i16 i32:visit_i32);
    uint_to_self!(u8:visit_u8 u16:visit_u16 u32:visit_u32 u64:visit_u64);
 }

 impl_deserialize_num! {
-    isize, NonZeroIsize cfg(not(no_num_nonzero_signed)), deserialize_i64
+    isize, NonZeroIsize, deserialize_i64
    num_as_self!(i8:visit_i8 i16:visit_i16);
    int_to_int!(i32:visit_i32 i64:visit_i64);
    uint_to_self!(u8:visit_u8 u16:visit_u16 u32:visit_u32 u64:visit_u64);
@@ -476,9 +469,7 @@ macro_rules! num_128 {
        where
            E: Error,
        {
-            if v as i128 >= Self::Value::min_value() as i128
-                && v as u128 <= Self::Value::max_value() as u128
-            {
+            if v as i128 >= Self::Value::MIN as i128 && v as u128 <= Self::Value::MAX as u128 {
                Ok(v as Self::Value)
            } else {
                Err(Error::invalid_value(
@@ -494,9 +485,7 @@ macro_rules! num_128 {
        where
            E: Error,
        {
-            if v as i128 >= $primitive::min_value() as i128
-                && v as u128 <= $primitive::max_value() as u128
-            {
+            if v as i128 >= $primitive::MIN as i128 && v as u128 <= $primitive::MAX as u128 {
                if let Some(nonzero) = Self::Value::new(v as $primitive) {
                    Ok(nonzero)
                } else {
@@ -528,7 +517,7 @@ macro_rules! num_128 {
 }

 impl_deserialize_num! {
-    i128, NonZeroI128 cfg(not(no_num_nonzero_signed)), deserialize_i128
+    i128, NonZeroI128, deserialize_i128
    num_self!(i128:visit_i128);
    num_as_self!(i8:visit_i8 i16:visit_i16 i32:visit_i32 i64:visit_i64);
    num_as_self!(u8:visit_u8 u16:visit_u16 u32:visit_u32 u64:visit_u64);
@@ -2184,7 +2173,7 @@ impl<'de> Deserialize<'de> for Duration {
                            b"secs" => Ok(Field::Secs),
                            b"nanos" => Ok(Field::Nanos),
                            _ => {
-                                let value = crate::__private::from_utf8_lossy(value);
+                                let value = private::string::from_utf8_lossy(value);
                                Err(Error::unknown_field(&*value, FIELDS))
                            }
                        }
@@ -2415,13 +2404,9 @@ impl<'de> Deserialize<'de> for SystemTime {

        const FIELDS: &[&str] = &["secs_since_epoch", "nanos_since_epoch"];
        let duration = tri!(deserializer.deserialize_struct("SystemTime", FIELDS, DurationVisitor));
-        #[cfg(not(no_systemtime_checked_add))]
-        let ret = UNIX_EPOCH
+        UNIX_EPOCH
            .checked_add(duration)
-            .ok_or_else(|| D::Error::custom("overflow deserializing SystemTime"));
-        #[cfg(no_systemtime_checked_add)]
-        let ret = Ok(UNIX_EPOCH + duration);
-        ret
+            .ok_or_else(|| D::Error::custom("overflow deserializing SystemTime"))
    }
 }

@@ -2479,6 +2464,7 @@ mod range {
    use crate::lib::*;

    use crate::de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
+    use crate::private;

    pub const FIELDS: &[&str] = &["start", "end"];

@@ -2524,7 +2510,7 @@ mod range {
                        b"start" => Ok(Field::Start),
                        b"end" => Ok(Field::End),
                        _ => {
-                            let value = crate::__private::from_utf8_lossy(value);
+                            let value = private::string::from_utf8_lossy(value);
                            Err(Error::unknown_field(&*value, FIELDS))
                        }
                    }
@@ -2637,6 +2623,7 @@ mod range_from {
    use crate::lib::*;

    use crate::de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
+    use crate::private;

    pub const FIELDS: &[&str] = &["start"];

@@ -2679,7 +2666,7 @@ mod range_from {
                    match value {
                        b"start" => Ok(Field::Start),
                        _ => {
-                            let value = crate::__private::from_utf8_lossy(value);
+                            let value = private::string::from_utf8_lossy(value);
                            Err(Error::unknown_field(&*value, FIELDS))
                        }
                    }
@@ -2775,6 +2762,7 @@ mod range_to {
    use crate::lib::*;

    use crate::de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
+    use crate::private;

    pub const FIELDS: &[&str] = &["end"];

@@ -2817,7 +2805,7 @@ mod range_to {
                    match value {
                        b"end" => Ok(Field::End),
                        _ => {
-                            let value = crate::__private::from_utf8_lossy(value);
+                            let value = private::string::from_utf8_lossy(value);
                            Err(Error::unknown_field(&*value, FIELDS))
                        }
                    }
@@ -2989,6 +2977,8 @@ where

 ////////////////////////////////////////////////////////////////////////////////

+#[cfg(feature = "result")]
+#[cfg_attr(docsrs, doc(cfg(feature = "result")))]
 impl<'de, T, E> Deserialize<'de> for Result<T, E>
 where
    T: Deserialize<'de>,
@@ -120,10 +120,9 @@ pub mod value;

 mod ignored_any;
 mod impls;
-pub(crate) mod size_hint;

 pub use self::ignored_any::IgnoredAny;
-
+pub use crate::private::InPlaceSeed;
 #[cfg(all(not(feature = "std"), no_core_error))]
 #[doc(no_inline)]
 pub use crate::std_error::Error as StdError;
@@ -158,6 +157,12 @@ macro_rules! declare_error_trait {
        /// type appropriate for a basic JSON data format.
        ///
        /// [example data format]: https://serde.rs/data-format.html
+        #[cfg_attr(
+            not(no_diagnostic_namespace),
+            diagnostic::on_unimplemented(
+                message = "the trait bound `{Self}: serde::de::Error` is not satisfied",
+            )
+        )]
        pub trait Error: Sized $(+ $($supertrait)::+)* {
            /// Raised when there is general error when deserializing a type.
            ///
@@ -206,7 +211,7 @@ macro_rules! declare_error_trait {
            /// containing an integer, the unexpected type is the integer and the
            /// expected type is the string.
            #[cold]
-            fn invalid_type(unexp: Unexpected, exp: &Expected) -> Self {
+            fn invalid_type(unexp: Unexpected, exp: &dyn Expected) -> Self {
                Error::custom(format_args!("invalid type: {}, expected {}", unexp, exp))
            }

@@ -224,7 +229,7 @@ macro_rules! declare_error_trait {
            /// that is not valid UTF-8, the unexpected value is the bytes and the
            /// expected value is a string.
            #[cold]
-            fn invalid_value(unexp: Unexpected, exp: &Expected) -> Self {
+            fn invalid_value(unexp: Unexpected, exp: &dyn Expected) -> Self {
                Error::custom(format_args!("invalid value: {}, expected {}", unexp, exp))
            }

@@ -238,7 +243,7 @@ macro_rules! declare_error_trait {
            /// expected. For example `exp` might say that a tuple of size 6 was
            /// expected.
            #[cold]
-            fn invalid_length(len: usize, exp: &Expected) -> Self {
+            fn invalid_length(len: usize, exp: &dyn Expected) -> Self {
                Error::custom(format_args!("invalid length {}, expected {}", len, exp))
            }

@@ -471,6 +476,12 @@ impl<'a> fmt::Display for Unexpected<'a> {
 /// ));
 /// # }
 /// ```
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::Expected` is not satisfied",
+    )
+)]
 pub trait Expected {
    /// Format an explanation of what data was being expected. Same signature as
    /// the `Display` and `Debug` traits.
@@ -492,7 +503,7 @@ impl Expected for &str {
    }
 }

-impl Display for Expected + '_ {
+impl Display for dyn Expected + '_ {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        Expected::fmt(self, formatter)
    }
@@ -534,6 +545,9 @@ impl Display for Expected + '_ {
 #[cfg_attr(
    not(no_diagnostic_namespace),
    diagnostic::on_unimplemented(
+        // Prevents `serde_core::de::Deserialize` appearing in the error message
+        // in projects with no direct dependency on serde_core.
+        message = "the trait bound `{Self}: serde::Deserialize<'de>` is not satisfied",
        note = "for local types consider adding `#[derive(serde::Deserialize)]` to your `{Self}` type",
        note = "for types from other crates check whether the crate offers a `serde` feature flag",
    )
@@ -610,6 +624,12 @@ pub trait Deserialize<'de>: Sized {
 /// lifetimes].
 ///
 /// [Understanding deserializer lifetimes]: https://serde.rs/lifetimes.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::DeserializeOwned` is not satisfied",
+    )
+)]
 pub trait DeserializeOwned: for<'de> Deserialize<'de> {}
 impl<T> DeserializeOwned for T where T: for<'de> Deserialize<'de> {}

@@ -775,6 +795,12 @@ impl<T> DeserializeOwned for T where T: for<'de> Deserialize<'de> {}
 /// #     Ok(())
 /// # }
 /// ```
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::DeserializeSeed<'de>` is not satisfied",
+    )
+)]
 pub trait DeserializeSeed<'de>: Sized {
    /// The type produced by using this seed.
    type Value;
@@ -911,6 +937,12 @@ where
 /// a basic JSON `Deserializer`.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::Deserializer<'de>` is not satisfied",
+    )
+)]
 pub trait Deserializer<'de>: Sized {
    /// The error type that can be returned if some error occurs during
    /// deserialization.
@@ -1226,13 +1258,9 @@ pub trait Deserializer<'de>: Sized {
    // Not public API.
    #[cfg(all(not(no_serde_derive), any(feature = "std", feature = "alloc")))]
    #[doc(hidden)]
-    fn __deserialize_content<V>(
-        self,
-        _: crate::actually_private::T,
-        visitor: V,
-    ) -> Result<crate::__private::de::Content<'de>, Self::Error>
+    fn __deserialize_content_v1<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
-        V: Visitor<'de, Value = crate::__private::de::Content<'de>>,
+        V: Visitor<'de, Value = crate::private::Content<'de>>,
    {
        self.deserialize_any(visitor)
    }
@@ -1281,6 +1309,12 @@ pub trait Deserializer<'de>: Sized {
 ///     }
 /// }
 /// ```
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::Visitor<'de>` is not satisfied",
+    )
+)]
 pub trait Visitor<'de>: Sized {
    /// The value produced by this visitor.
    type Value;
@@ -1707,6 +1741,12 @@ pub trait Visitor<'de>: Sized {
 /// implementation of `SeqAccess` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::SeqAccess<'de>` is not satisfied",
+    )
+)]
 pub trait SeqAccess<'de> {
    /// The error type that can be returned if some error occurs during
    /// deserialization.
@@ -1789,6 +1829,12 @@ where
 /// implementation of `MapAccess` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::MapAccess<'de>` is not satisfied",
+    )
+)]
 pub trait MapAccess<'de> {
    /// The error type that can be returned if some error occurs during
    /// deserialization.
@@ -1981,6 +2027,12 @@ where
 /// implementation of `EnumAccess` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::EnumAccess<'de>` is not satisfied",
+    )
+)]
 pub trait EnumAccess<'de>: Sized {
    /// The error type that can be returned if some error occurs during
    /// deserialization.
@@ -2028,6 +2080,12 @@ pub trait EnumAccess<'de>: Sized {
 /// implementation of `VariantAccess` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::de::VariantAccess<'de>` is not satisfied",
+    )
+)]
 pub trait VariantAccess<'de>: Sized {
    /// The error type that can be returned if some error occurs during
    /// deserialization. Must match the error type of our `EnumAccess`.
@@ -24,7 +24,8 @@
 use crate::lib::*;

 use self::private::{First, Second};
-use crate::de::{self, size_hint, Deserializer, Expected, IntoDeserializer, SeqAccess, Visitor};
+use crate::de::{self, Deserializer, Expected, IntoDeserializer, SeqAccess, Visitor};
+use crate::private::size_hint;
 use crate::ser;

 ////////////////////////////////////////////////////////////////////////////////
@@ -0,0 +1,270 @@
+//! Serde is a framework for ***ser***ializing and ***de***serializing Rust data
+//! structures efficiently and generically.
+//!
+//! The `serde_core` crate contains Serde's trait definitions with **no support
+//! for #\[derive()\]**.
+//!
+//! In crates that derive an implementation of `Serialize` or `Deserialize`, you
+//! must depend on the [`serde`] crate, not `serde_core`.
+//!
+//! [`serde`]: https://crates.io/crates/serde
+//!
+//! In crates that handwrite implementations of Serde traits, or only use them
+//! as trait bounds, depending on `serde_core` is permitted. But `serde`
+//! re-exports all of these traits and can be used for this use case too. If in
+//! doubt, disregard `serde_core` and always use `serde`.
+//!
+//! Crates that depend on `serde_core` instead of `serde` are able to compile in
+//! parallel with `serde_derive` even when `serde`'s "derive" feature is turned on,
+//! as shown in the following build timings.
+//!
+//! <br>
+//!
+//! <table>
+//! <tr><td align="center">When <code>serde_json</code> depends on <code>serde</code></td></tr>
+//! <tr><td><img src="https://github.com/user-attachments/assets/78dc179c-6ab1-4059-928c-1474b0d9d0bb"></td></tr>
+//! </table>
+//!
+//! <br>
+//!
+//! <table>
+//! <tr><td align="center">When <code>serde_json</code> depends on <code>serde_core</code></td></tr>
+//! <tr><td><img src="https://github.com/user-attachments/assets/6b6cff5e-3e45-4ac7-9db1-d99ee8b9f5f7"></td></tr>
+//! </table>
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Serde types in rustdoc of other crates get linked to here.
+#![doc(html_root_url = "https://docs.rs/serde/1.0.221")]
+// Support using Serde without the standard library!
+#![cfg_attr(not(feature = "std"), no_std)]
+// Show which crate feature enables conditionally compiled APIs in documentation.
+#![cfg_attr(docsrs, feature(doc_cfg, rustdoc_internals))]
+#![cfg_attr(docsrs, allow(internal_features))]
+// Unstable functionality only if the user asks for it. For tracking and
+// discussion of these features please refer to this issue:
+//
+//    https://github.com/serde-rs/serde/issues/812
+#![cfg_attr(feature = "unstable", feature(never_type))]
+#![allow(unknown_lints, bare_trait_objects, deprecated)]
+// Ignored clippy and clippy_pedantic lints
+#![allow(
+    // clippy bug: https://github.com/rust-lang/rust-clippy/issues/5704
+    clippy::unnested_or_patterns,
+    // clippy bug: https://github.com/rust-lang/rust-clippy/issues/7768
+    clippy::semicolon_if_nothing_returned,
+    // not available in our oldest supported compiler
+    clippy::empty_enum,
+    clippy::type_repetition_in_bounds, // https://github.com/rust-lang/rust-clippy/issues/8772
+    // integer and float ser/de requires these sorts of casts
+    clippy::cast_possible_truncation,
+    clippy::cast_possible_wrap,
+    clippy::cast_precision_loss,
+    clippy::cast_sign_loss,
+    // things are often more readable this way
+    clippy::cast_lossless,
+    clippy::module_name_repetitions,
+    clippy::single_match_else,
+    clippy::type_complexity,
+    clippy::use_self,
+    clippy::zero_prefixed_literal,
+    // correctly used
+    clippy::derive_partial_eq_without_eq,
+    clippy::enum_glob_use,
+    clippy::explicit_auto_deref,
+    clippy::incompatible_msrv,
+    clippy::let_underscore_untyped,
+    clippy::map_err_ignore,
+    clippy::new_without_default,
+    clippy::result_unit_err,
+    clippy::wildcard_imports,
+    // not practical
+    clippy::needless_pass_by_value,
+    clippy::similar_names,
+    clippy::too_many_lines,
+    // preference
+    clippy::doc_markdown,
+    clippy::elidable_lifetime_names,
+    clippy::needless_lifetimes,
+    clippy::unseparated_literal_suffix,
+    // false positive
+    clippy::needless_doctest_main,
+    // noisy
+    clippy::missing_errors_doc,
+    clippy::must_use_candidate,
+)]
+// Restrictions
+#![deny(clippy::question_mark_used)]
+// Rustc lints.
+#![deny(missing_docs, unused_imports)]
+
+////////////////////////////////////////////////////////////////////////////////
+
+#[cfg(feature = "alloc")]
+extern crate alloc;
+
+/// A facade around all the types we need from the `std`, `core`, and `alloc`
+/// crates. This avoids elaborate import wrangling having to happen in every
+/// module.
+mod lib {
+    mod core {
+        #[cfg(not(feature = "std"))]
+        pub use core::*;
+        #[cfg(feature = "std")]
+        pub use std::*;
+    }
+
+    pub use self::core::{f32, f64};
+    pub use self::core::{iter, num, str};
+
+    #[cfg(any(feature = "std", feature = "alloc"))]
+    pub use self::core::{cmp, mem};
+
+    pub use self::core::cell::{Cell, RefCell};
+    pub use self::core::cmp::Reverse;
+    pub use self::core::fmt::{self, Debug, Display, Write as FmtWrite};
+    pub use self::core::marker::PhantomData;
+    pub use self::core::num::Wrapping;
+    pub use self::core::ops::{Bound, Range, RangeFrom, RangeInclusive, RangeTo};
+    pub use self::core::result;
+    pub use self::core::time::Duration;
+
+    #[cfg(all(feature = "alloc", not(feature = "std")))]
+    pub use alloc::borrow::{Cow, ToOwned};
+    #[cfg(feature = "std")]
+    pub use std::borrow::{Cow, ToOwned};
+
+    #[cfg(all(feature = "alloc", not(feature = "std")))]
+    pub use alloc::string::{String, ToString};
+    #[cfg(feature = "std")]
+    pub use std::string::{String, ToString};
+
+    #[cfg(all(feature = "alloc", not(feature = "std")))]
+    pub use alloc::vec::Vec;
+    #[cfg(feature = "std")]
+    pub use std::vec::Vec;
+
+    #[cfg(all(feature = "alloc", not(feature = "std")))]
+    pub use alloc::boxed::Box;
+    #[cfg(feature = "std")]
+    pub use std::boxed::Box;
+
+    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
+    pub use alloc::rc::{Rc, Weak as RcWeak};
+    #[cfg(all(feature = "rc", feature = "std"))]
+    pub use std::rc::{Rc, Weak as RcWeak};
+
+    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
+    pub use alloc::sync::{Arc, Weak as ArcWeak};
+    #[cfg(all(feature = "rc", feature = "std"))]
+    pub use std::sync::{Arc, Weak as ArcWeak};
+
+    #[cfg(all(feature = "alloc", not(feature = "std")))]
+    pub use alloc::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
+    #[cfg(feature = "std")]
+    pub use std::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
+
+    #[cfg(all(not(no_core_cstr), not(feature = "std")))]
+    pub use self::core::ffi::CStr;
+    #[cfg(feature = "std")]
+    pub use std::ffi::CStr;
+
+    #[cfg(all(not(no_core_cstr), feature = "alloc", not(feature = "std")))]
+    pub use alloc::ffi::CString;
+    #[cfg(feature = "std")]
+    pub use std::ffi::CString;
+
+    #[cfg(all(not(no_core_net), not(feature = "std")))]
+    pub use self::core::net;
+    #[cfg(feature = "std")]
+    pub use std::net;
+
+    #[cfg(feature = "std")]
+    pub use std::error;
+
+    #[cfg(feature = "std")]
+    pub use std::collections::{HashMap, HashSet};
+    #[cfg(feature = "std")]
+    pub use std::ffi::{OsStr, OsString};
+    #[cfg(feature = "std")]
+    pub use std::hash::{BuildHasher, Hash};
+    #[cfg(feature = "std")]
+    pub use std::io::Write;
+    #[cfg(feature = "std")]
+    pub use std::path::{Path, PathBuf};
+    #[cfg(feature = "std")]
+    pub use std::sync::{Mutex, RwLock};
+    #[cfg(feature = "std")]
+    pub use std::time::{SystemTime, UNIX_EPOCH};
+
+    #[cfg(all(feature = "std", no_target_has_atomic, not(no_std_atomic)))]
+    pub use std::sync::atomic::{
+        AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU8,
+        AtomicUsize, Ordering,
+    };
+    #[cfg(all(feature = "std", no_target_has_atomic, not(no_std_atomic64)))]
+    pub use std::sync::atomic::{AtomicI64, AtomicU64};
+
+    #[cfg(all(feature = "std", not(no_target_has_atomic)))]
+    pub use std::sync::atomic::Ordering;
+    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "8"))]
+    pub use std::sync::atomic::{AtomicBool, AtomicI8, AtomicU8};
+    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "16"))]
+    pub use std::sync::atomic::{AtomicI16, AtomicU16};
+    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "32"))]
+    pub use std::sync::atomic::{AtomicI32, AtomicU32};
+    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "64"))]
+    pub use std::sync::atomic::{AtomicI64, AtomicU64};
+    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "ptr"))]
+    pub use std::sync::atomic::{AtomicIsize, AtomicUsize};
+
+    #[cfg(not(no_core_num_saturating))]
+    pub use self::core::num::Saturating;
+}
+
+// None of this crate's error handling needs the `From::from` error conversion
+// performed implicitly by the `?` operator or the standard library's `try!`
+// macro. This simplified macro gives a 5.5% improvement in compile time
+// compared to standard `try!`, and 9% improvement compared to `?`.
+macro_rules! tri {
+    ($expr:expr) => {
+        match $expr {
+            Ok(val) => val,
+            Err(err) => return Err(err),
+        }
+    };
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+#[macro_use]
+mod macros;
+
+pub mod de;
+pub mod ser;
+
+mod format;
+
+#[doc(inline)]
+pub use crate::de::{Deserialize, Deserializer};
+#[doc(inline)]
+pub use crate::ser::{Serialize, Serializer};
+
+// Used by generated code. Not public API.
+#[doc(hidden)]
+#[path = "private/mod.rs"]
+pub mod __private;
+use self::__private as private;
+
+#[cfg(all(not(feature = "std"), no_core_error))]
+mod std_error;
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __require_serde_not_serde_core {
+    () => {
+        ::core::compile_error!(
+            "Serde derive requires a dependency on the serde crate, not serde_core"
+        );
+    };
+}
@@ -1,7 +1,6 @@
 // Super explicit first paragraph because this shows up at the top level and
 // trips up people who are just looking for basic Serialize / Deserialize
 // documentation.
-//
 /// Helper macro when implementing the `Deserializer` part of a new data format
 /// for Serde.
 ///
@@ -0,0 +1,264 @@
+use crate::de::{self, Deserialize, Deserializer, EnumAccess, MapAccess, SeqAccess, Visitor};
+use crate::lib::*;
+use crate::private::size_hint;
+
+// Used from generated code to buffer the contents of the Deserializer when
+// deserializing untagged enums and internally tagged enums.
+//
+// Not public API. Use serde-value instead.
+//
+// Obsoleted by format-specific buffer types (https://github.com/serde-rs/serde/pull/2912).
+#[derive(Clone)]
+#[doc(hidden)]
+pub enum Content<'de> {
+    Bool(bool),
+
+    U8(u8),
+    U16(u16),
+    U32(u32),
+    U64(u64),
+
+    I8(i8),
+    I16(i16),
+    I32(i32),
+    I64(i64),
+
+    F32(f32),
+    F64(f64),
+
+    Char(char),
+    String(String),
+    Str(&'de str),
+    ByteBuf(Vec<u8>),
+    Bytes(&'de [u8]),
+
+    None,
+    Some(Box<Content<'de>>),
+
+    Unit,
+    Newtype(Box<Content<'de>>),
+    Seq(Vec<Content<'de>>),
+    Map(Vec<(Content<'de>, Content<'de>)>),
+}
+
+impl<'de> Deserialize<'de> for Content<'de> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        // Untagged and internally tagged enums are only supported in
+        // self-describing formats.
+        let visitor = ContentVisitor { value: PhantomData };
+        deserializer.__deserialize_content_v1(visitor)
+    }
+}
+
+#[doc(hidden)]
+pub struct ContentVisitor<'de> {
+    value: PhantomData<Content<'de>>,
+}
+
+impl<'de> ContentVisitor<'de> {
+    pub fn new() -> Self {
+        ContentVisitor { value: PhantomData }
+    }
+}
+
+impl<'de> Visitor<'de> for ContentVisitor<'de> {
+    type Value = Content<'de>;
+
+    fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.write_str("any value")
+    }
+
+    fn visit_bool<F>(self, value: bool) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::Bool(value))
+    }
+
+    fn visit_i8<F>(self, value: i8) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::I8(value))
+    }
+
+    fn visit_i16<F>(self, value: i16) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::I16(value))
+    }
+
+    fn visit_i32<F>(self, value: i32) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::I32(value))
+    }
+
+    fn visit_i64<F>(self, value: i64) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::I64(value))
+    }
+
+    fn visit_u8<F>(self, value: u8) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::U8(value))
+    }
+
+    fn visit_u16<F>(self, value: u16) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::U16(value))
+    }
+
+    fn visit_u32<F>(self, value: u32) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::U32(value))
+    }
+
+    fn visit_u64<F>(self, value: u64) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::U64(value))
+    }
+
+    fn visit_f32<F>(self, value: f32) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::F32(value))
+    }
+
+    fn visit_f64<F>(self, value: f64) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::F64(value))
+    }
+
+    fn visit_char<F>(self, value: char) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::Char(value))
+    }
+
+    fn visit_str<F>(self, value: &str) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::String(value.into()))
+    }
+
+    fn visit_borrowed_str<F>(self, value: &'de str) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::Str(value))
+    }
+
+    fn visit_string<F>(self, value: String) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::String(value))
+    }
+
+    fn visit_bytes<F>(self, value: &[u8]) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::ByteBuf(value.into()))
+    }
+
+    fn visit_borrowed_bytes<F>(self, value: &'de [u8]) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::Bytes(value))
+    }
+
+    fn visit_byte_buf<F>(self, value: Vec<u8>) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::ByteBuf(value))
+    }
+
+    fn visit_unit<F>(self) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::Unit)
+    }
+
+    fn visit_none<F>(self) -> Result<Self::Value, F>
+    where
+        F: de::Error,
+    {
+        Ok(Content::None)
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let v = tri!(Deserialize::deserialize(deserializer));
+        Ok(Content::Some(Box::new(v)))
+    }
+
+    fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let v = tri!(Deserialize::deserialize(deserializer));
+        Ok(Content::Newtype(Box::new(v)))
+    }
+
+    fn visit_seq<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+    where
+        V: SeqAccess<'de>,
+    {
+        let mut vec =
+            Vec::<Content>::with_capacity(size_hint::cautious::<Content>(visitor.size_hint()));
+        while let Some(e) = tri!(visitor.next_element()) {
+            vec.push(e);
+        }
+        Ok(Content::Seq(vec))
+    }
+
+    fn visit_map<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+    where
+        V: MapAccess<'de>,
+    {
+        let mut vec = Vec::<(Content, Content)>::with_capacity(size_hint::cautious::<(
+            Content,
+            Content,
+        )>(visitor.size_hint()));
+        while let Some(kv) = tri!(visitor.next_entry()) {
+            vec.push(kv);
+        }
+        Ok(Content::Map(vec))
+    }
+
+    fn visit_enum<V>(self, _visitor: V) -> Result<Self::Value, V::Error>
+    where
+        V: EnumAccess<'de>,
+    {
+        Err(de::Error::custom(
+            "untagged and internally tagged enums do not support enum input",
+        ))
+    }
+}
@@ -0,0 +1,21 @@
+#[cfg(all(not(no_serde_derive), any(feature = "std", feature = "alloc")))]
+mod content;
+mod seed;
+
+// FIXME: #[cfg(doctest)] once https://github.com/rust-lang/rust/issues/67295 is fixed.
+#[doc(hidden)]
+pub mod doc;
+
+#[doc(hidden)]
+pub mod size_hint;
+
+#[doc(hidden)]
+pub mod string;
+
+#[cfg(all(not(no_serde_derive), any(feature = "std", feature = "alloc")))]
+#[doc(hidden)]
+pub use self::content::{Content, ContentVisitor};
+#[doc(hidden)]
+pub use self::seed::InPlaceSeed;
+#[doc(hidden)]
+pub use crate::lib::result::Result;
@@ -1,3 +1,4 @@
+#[cfg(any(feature = "std", feature = "alloc"))]
 use crate::lib::*;

 pub fn from_bounds<I>(iter: &I) -> Option<usize>
@@ -0,0 +1,23 @@
+use crate::lib::*;
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[doc(hidden)]
+pub fn from_utf8_lossy(bytes: &[u8]) -> Cow<'_, str> {
+    String::from_utf8_lossy(bytes)
+}
+
+// The generated code calls this like:
+//
+//     let value = &_serde::__private::from_utf8_lossy(bytes);
+//     Err(_serde::de::Error::unknown_variant(value, VARIANTS))
+//
+// so it is okay for the return type to be different from the std case as long
+// as the above works.
+#[cfg(not(any(feature = "std", feature = "alloc")))]
+#[doc(hidden)]
+pub fn from_utf8_lossy(bytes: &[u8]) -> &str {
+    // Three unicode replacement characters if it fails. They look like a
+    // white-on-black question mark. The user will recognize it as invalid
+    // UTF-8.
+    str::from_utf8(bytes).unwrap_or("\u{fffd}\u{fffd}\u{fffd}")
+}
@@ -185,11 +185,10 @@ where
    }
 }

-#[cfg(not(no_relaxed_trait_bounds))]
 macro_rules! seq_impl {
    (
        $(#[$attr:meta])*
-        $ty:ident <T $(: $tbound1:ident $(+ $tbound2:ident)*)* $(, $typaram:ident : $bound:ident)*>
+        $ty:ident <T $(, $typaram:ident : $bound:ident)*>
    ) => {
        $(#[$attr])*
        impl<T $(, $typaram)*> Serialize for $ty<T $(, $typaram)*>
@@ -207,45 +206,22 @@ macro_rules! seq_impl {
    }
 }

-#[cfg(no_relaxed_trait_bounds)]
-macro_rules! seq_impl {
-    (
-        $(#[$attr:meta])*
-        $ty:ident <T $(: $tbound1:ident $(+ $tbound2:ident)*)* $(, $typaram:ident : $bound:ident)*>
-    ) => {
-        $(#[$attr])*
-        impl<T $(, $typaram)*> Serialize for $ty<T $(, $typaram)*>
-        where
-            T: Serialize $(+ $tbound1 $(+ $tbound2)*)*,
-            $($typaram: $bound,)*
-        {
-            #[inline]
-            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-            where
-                S: Serializer,
-            {
-                serializer.collect_seq(self)
-            }
-        }
-    }
+seq_impl! {
+    #[cfg(any(feature = "std", feature = "alloc"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+    BinaryHeap<T>
 }

 seq_impl! {
    #[cfg(any(feature = "std", feature = "alloc"))]
    #[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
-    BinaryHeap<T: Ord>
-}
-
-seq_impl! {
-    #[cfg(any(feature = "std", feature = "alloc"))]
-    #[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
-    BTreeSet<T: Ord>
+    BTreeSet<T>
 }

 seq_impl! {
    #[cfg(feature = "std")]
    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
-    HashSet<T: Eq + Hash, H: BuildHasher>
+    HashSet<T, H: BuildHasher>
 }

 seq_impl! {
@@ -445,7 +421,6 @@ tuple_impls! {

 ////////////////////////////////////////////////////////////////////////////////

-#[cfg(not(no_relaxed_trait_bounds))]
 macro_rules! map_impl {
    (
        $(#[$attr:meta])*
@@ -468,30 +443,6 @@ macro_rules! map_impl {
    }
 }

-#[cfg(no_relaxed_trait_bounds)]
-macro_rules! map_impl {
-    (
-        $(#[$attr:meta])*
-        $ty:ident <K $(: $kbound1:ident $(+ $kbound2:ident)*)*, V $(, $typaram:ident : $bound:ident)*>
-    ) => {
-        $(#[$attr])*
-        impl<K, V $(, $typaram)*> Serialize for $ty<K, V $(, $typaram)*>
-        where
-            K: Serialize $(+ $kbound1 $(+ $kbound2)*)*,
-            V: Serialize,
-            $($typaram: $bound,)*
-        {
-            #[inline]
-            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-            where
-                S: Serializer,
-            {
-                serializer.collect_map(self)
-            }
-        }
-    }
-}
-
 map_impl! {
    #[cfg(any(feature = "std", feature = "alloc"))]
    #[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
@@ -631,16 +582,6 @@ macro_rules! nonzero_integers {
    }
 }

-nonzero_integers! {
-    NonZeroU8,
-    NonZeroU16,
-    NonZeroU32,
-    NonZeroU64,
-    NonZeroU128,
-    NonZeroUsize,
-}
-
-#[cfg(not(no_num_nonzero_signed))]
 nonzero_integers! {
    NonZeroI8,
    NonZeroI16,
@@ -648,6 +589,12 @@ nonzero_integers! {
    NonZeroI64,
    NonZeroI128,
    NonZeroIsize,
+    NonZeroU8,
+    NonZeroU16,
+    NonZeroU32,
+    NonZeroU64,
+    NonZeroU128,
+    NonZeroUsize,
 }

 impl<T> Serialize for Cell<T>
@@ -713,6 +660,8 @@ where

 ////////////////////////////////////////////////////////////////////////////////

+#[cfg(feature = "result")]
+#[cfg_attr(docsrs, doc(cfg(feature = "result")))]
 impl<T, E> Serialize for Result<T, E>
 where
    T: Serialize,
@@ -17,7 +17,7 @@ use crate::ser::{
 ///
 /// ```edition2021
 /// # use serde::ser::{Serializer, Impossible};
-/// # use serde::__private::doc::Error;
+/// # use serde_core::__private::doc::Error;
 /// #
 /// # struct MySerializer;
 /// #
@@ -41,7 +41,7 @@ use crate::ser::{
 ///     }
 ///
 ///     /* other Serializer methods */
-/// #     serde::__serialize_unimplemented! {
+/// #     serde_core::__serialize_unimplemented! {
 /// #         bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str bytes none some
 /// #         unit unit_struct unit_variant newtype_struct newtype_variant
 /// #         tuple tuple_struct tuple_variant map struct struct_variant
@@ -139,6 +139,12 @@ macro_rules! declare_error_trait {
        /// type appropriate for a basic JSON data format.
        ///
        /// [example data format]: https://serde.rs/data-format.html
+        #[cfg_attr(
+            not(no_diagnostic_namespace),
+            diagnostic::on_unimplemented(
+                message = "the trait bound `{Self}: serde::ser::Error` is not satisfied",
+            )
+        )]
        pub trait Error: Sized $(+ $($supertrait)::+)* {
            /// Used when a [`Serialize`] implementation encounters any error
            /// while serializing a type.
@@ -218,6 +224,9 @@ declare_error_trait!(Error: Sized + Debug + Display);
 #[cfg_attr(
    not(no_diagnostic_namespace),
    diagnostic::on_unimplemented(
+        // Prevents `serde_core::ser::Serialize` appearing in the error message
+        // in projects with no direct dependency on serde_core.
+        message = "the trait bound `{Self}: serde::Serialize` is not satisfied",
        note = "for local types consider adding `#[derive(serde::Serialize)]` to your `{Self}` type",
        note = "for types from other crates check whether the crate offers a `serde` feature flag",
    )
@@ -337,6 +346,12 @@ pub trait Serialize {
 /// a basic JSON `Serializer`.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::Serializer` is not satisfied",
+    )
+)]
 pub trait Serializer: Sized {
    /// The output type produced by this `Serializer` during successful
    /// serialization. Most serializers that produce text or binary output
@@ -398,7 +413,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for bool {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -420,7 +435,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for i8 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -442,7 +457,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for i16 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -464,7 +479,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for i32 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -482,7 +497,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for i64 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -500,7 +515,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for i128 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -527,7 +542,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for u8 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -549,7 +564,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for u16 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -571,7 +586,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for u32 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -589,7 +604,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for u64 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -607,7 +622,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for u128 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -634,7 +649,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for f32 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -652,7 +667,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for f64 {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -673,7 +688,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for char {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -691,7 +706,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for str {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -714,7 +729,7 @@ pub trait Serializer: Sized {
    ///
    /// ```edition2021
    /// # use serde::ser::{Serializer, SerializeSeq};
-    /// # use serde::__private::doc::Error;
+    /// # use serde_core::__private::doc::Error;
    /// #
    /// # struct MySerializer;
    /// #
@@ -730,7 +745,7 @@ pub trait Serializer: Sized {
    ///     seq.end()
    /// }
    /// #
-    /// #     serde::__serialize_unimplemented! {
+    /// #     serde_core::__serialize_unimplemented! {
    /// #         bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str none some
    /// #         unit unit_struct unit_variant newtype_struct newtype_variant
    /// #         seq tuple tuple_struct tuple_variant map struct struct_variant
@@ -812,7 +827,7 @@ pub trait Serializer: Sized {
    /// ```edition2021
    /// # use serde::Serializer;
    /// #
-    /// # serde::__private_serialize!();
+    /// # serde_core::__private_serialize!();
    /// #
    /// impl Serialize for () {
    ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -1494,6 +1509,12 @@ pub trait Serializer: Sized {
 /// implementation of `SerializeSeq` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::ser::SerializeSeq` is not satisfied",
+    )
+)]
 pub trait SerializeSeq {
    /// Must match the `Ok` type of our `Serializer`.
    type Ok;
@@ -1594,6 +1615,12 @@ pub trait SerializeSeq {
 /// implementation of `SerializeTuple` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::ser::SerializeTuple` is not satisfied",
+    )
+)]
 pub trait SerializeTuple {
    /// Must match the `Ok` type of our `Serializer`.
    type Ok;
@@ -1639,6 +1666,12 @@ pub trait SerializeTuple {
 /// implementation of `SerializeTupleStruct` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::ser::SerializeTupleStruct` is not satisfied",
+    )
+)]
 pub trait SerializeTupleStruct {
    /// Must match the `Ok` type of our `Serializer`.
    type Ok;
@@ -1697,6 +1730,12 @@ pub trait SerializeTupleStruct {
 /// implementation of `SerializeTupleVariant` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::ser::SerializeTupleVariant` is not satisfied",
+    )
+)]
 pub trait SerializeTupleVariant {
    /// Must match the `Ok` type of our `Serializer`.
    type Ok;
@@ -1763,6 +1802,12 @@ pub trait SerializeTupleVariant {
 /// implementation of `SerializeMap` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::ser::SerializeMap` is not satisfied",
+    )
+)]
 pub trait SerializeMap {
    /// Must match the `Ok` type of our `Serializer`.
    type Ok;
@@ -1853,6 +1898,12 @@ pub trait SerializeMap {
 /// implementation of `SerializeStruct` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::ser::SerializeStruct` is not satisfied",
+    )
+)]
 pub trait SerializeStruct {
    /// Must match the `Ok` type of our `Serializer`.
    type Ok;
@@ -1917,6 +1968,12 @@ pub trait SerializeStruct {
 /// implementation of `SerializeStructVariant` for a basic JSON data format.
 ///
 /// [example data format]: https://serde.rs/data-format.html
+#[cfg_attr(
+    not(no_diagnostic_namespace),
+    diagnostic::on_unimplemented(
+        message = "the trait bound `{Self}: serde::ser::SerializeStructVariant` is not satisfied",
+    )
+)]
 pub trait SerializeStructVariant {
    /// Must match the `Ok` type of our `Serializer`.
    type Ok;
@@ -42,7 +42,7 @@ use crate::lib::{Debug, Display};
 /// ```
 pub trait Error: Debug + Display {
    /// The underlying cause of this error, if any.
-    fn source(&self) -> Option<&(Error + 'static)> {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
        None
    }
 }
@@ -1,11 +1,11 @@
 [package]
 name = "serde_derive"
-version = "1.0.218"
+version = "1.0.221"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 categories = ["no-std", "no-std::no-alloc"]
 description = "Macros 1.1 implementation of #[derive(Serialize, Deserialize)]"
 documentation = "https://serde.rs/derive.html"
-edition = "2015"
+edition = "2021"
 exclude = ["build.rs"]
 homepage = "https://serde.rs"
 keywords = ["serde", "serialization", "no_std", "derive"]
@@ -37,4 +37,5 @@ rustdoc-args = [
    "--extern-html-root-url=core=https://doc.rust-lang.org",
    "--extern-html-root-url=alloc=https://doc.rust-lang.org",
    "--extern-html-root-url=std=https://doc.rust-lang.org",
+    "--extern-html-root-url=proc_macro=https://doc.rust-lang.org",
 ]
@@ -2662,7 +2662,7 @@ fn deserialize_map(
            if let _serde::__private::Some(_serde::__private::Some((__key, _))) =
                __collect.into_iter().filter(_serde::__private::Option::is_some).next()
            {
-                if let _serde::__private::Some(__key) = __key.as_str() {
+                if let _serde::__private::Some(__key) = _serde::__private::de::content_as_str(&__key) {
                    return _serde::__private::Err(
                        _serde::de::Error::custom(format_args!("unknown field `{}`", &__key)));
                } else {
@@ -14,9 +14,17 @@ pub fn wrap_in_const(serde_path: Option<&syn::Path>, code: TokenStream) -> Token

    quote! {
        #[doc(hidden)]
-        #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
+        #[allow(
+            non_upper_case_globals,
+            unused_attributes,
+            unused_qualifications,
+            clippy::absolute_paths,
+        )]
        const _: () = {
            #use_serde
+
+            _serde::__require_serde_not_serde_core!();
+
            #code
        };
    }
@@ -2,7 +2,6 @@ use crate::internals::respan::respan;
 use proc_macro2::Span;
 use quote::ToTokens;
 use std::mem;
-use syn::punctuated::Punctuated;
 use syn::{
    parse_quote, Data, DeriveInput, Expr, ExprPath, GenericArgument, GenericParam, Generics, Macro,
    Path, PathArguments, QSelf, ReturnType, Token, Type, TypeParamBound, TypePath, WherePredicate,
@@ -49,7 +48,7 @@ impl ReplaceReceiver<'_> {

        path.leading_colon = Some(**path.segments.pairs().next().unwrap().punct().unwrap());

-        let segments = mem::replace(&mut path.segments, Punctuated::new());
+        let segments = mem::take(&mut path.segments);
        path.segments = segments.into_pairs().skip(1).collect();
    }

@@ -13,7 +13,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html

-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.218")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.221")]
 #![cfg_attr(not(check_cfg), allow(unexpected_cfgs))]
 // Ignored clippy lints
 #![allow(
@@ -41,6 +41,7 @@
    clippy::cast_possible_truncation,
    clippy::checked_conversions,
    clippy::doc_markdown,
+    clippy::elidable_lifetime_names,
    clippy::enum_glob_use,
    clippy::indexing_slicing,
    clippy::items_after_statements,
@@ -63,6 +64,7 @@
    clippy::wildcard_imports
 )]
 #![cfg_attr(all(test, exhaustive), feature(non_exhaustive_omitted_patterns_lint))]
+#![allow(unknown_lints, mismatched_lifetime_syntaxes)]

 extern crate proc_macro2;
 extern crate quote;
@@ -150,7 +150,7 @@ fn build_generics(cont: &Container) -> syn::Generics {
 }

 // Fields with a `skip_serializing` or `serialize_with` attribute, or which
-// belong to a variant with a 'skip_serializing` or `serialize_with` attribute,
+// belong to a variant with a `skip_serializing` or `serialize_with` attribute,
 // are not serialized by us so we do not generate a bound. Fields with a `bound`
 // attribute specify their own bound so we do not generate one. All other fields
 // may need a `T: Serialize` bound where T is the type of the field.
@@ -4,7 +4,7 @@ version = "0.29.1"
 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"
-edition = "2015"
+edition = "2021"
 exclude = ["build.rs"]
 homepage = "https://serde.rs"
 keywords = ["serde", "serialization"]
@@ -27,4 +27,5 @@ rustdoc-args = [
    "--extern-html-root-url=core=https://doc.rust-lang.org",
    "--extern-html-root-url=alloc=https://doc.rust-lang.org",
    "--extern-html-root-url=std=https://doc.rust-lang.org",
+    "--extern-html-root-url=proc_macro=https://doc.rust-lang.org",
 ]
@@ -21,6 +21,7 @@
 // Ignored clippy_pedantic lints
 #![allow(
    clippy::doc_markdown,
+    clippy::elidable_lifetime_names,
    clippy::enum_glob_use,
    clippy::items_after_statements,
    clippy::let_underscore_untyped,
@@ -40,6 +41,7 @@
    clippy::unused_self,
    clippy::wildcard_imports
 )]
+#![allow(unknown_lints, mismatched_lifetime_syntaxes)]

 extern crate proc_macro2;
 extern crate quote;
@@ -2,7 +2,7 @@
 name = "serde_test_suite"
 version = "0.0.0"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
-edition = "2018"
+edition = "2021"
 publish = false

 [features]
@@ -13,9 +13,9 @@ serde = { path = "../serde" }

 [dev-dependencies]
 automod = "1.0.1"
-foldhash = "0.1"
+foldhash = "0.2"
 rustversion = "1.0"
 serde = { path = "../serde", features = ["rc"] }
 serde_derive = { path = "../serde_derive", features = ["deserialize_in_place"] }
 serde_test = "1.0.176"
-trybuild = { version = "1.0.97", features = ["diff"] }
+trybuild = { version = "1.0.108", features = ["diff"] }
@@ -2,7 +2,7 @@
 name = "serde_derive_tests_no_std"
 version = "0.0.0"
 authors = ["David Tolnay <dtolnay@gmail.com>"]
-edition = "2018"
+edition = "2021"
 publish = false

 [dependencies]
@@ -1,3 +1,5 @@
+#![allow(dead_code)]
+
 use serde_derive::Deserialize;

 #[derive(Deserialize)]
@@ -1,3 +1,5 @@
+#![allow(dead_code)]
+
 use serde_derive::Deserialize;

 macro_rules! bug {
@@ -2,4 +2,5 @@ use serde_derive::Serialize;

 #[derive(Serialize)]
 #[serde()]
+#[allow(dead_code)]
 pub struct S;
@@ -1,4 +1,4 @@
-#![allow(clippy::trivially_copy_pass_by_ref)]
+#![allow(clippy::trivially_copy_pass_by_ref, dead_code)]

 use serde_derive::{Deserialize, Serialize};

@@ -1,4 +1,4 @@
-#![allow(clippy::trivially_copy_pass_by_ref)]
+#![allow(clippy::trivially_copy_pass_by_ref, dead_code)]

 use serde_derive::Deserialize;

@@ -1,7 +1,10 @@
 #![allow(
    clippy::derive_partial_eq_without_eq,
    clippy::items_after_statements,
-    clippy::used_underscore_binding
+    clippy::used_underscore_binding,
+    // We use lots of declarations inside function bodies to avoid conflicts,
+    // but they aren't used. We just want to make sure they compile.
+    dead_code,
 )]

 use serde::de::value::{BorrowedStrDeserializer, MapDeserializer};
@@ -18,7 +18,10 @@
    clippy::ptr_arg,
    clippy::too_many_lines,
    clippy::trivially_copy_pass_by_ref,
-    clippy::type_repetition_in_bounds
+    clippy::type_repetition_in_bounds,
+    // We use lots of declarations inside function bodies to avoid conflicts,
+    // but they aren't used. We just want to make sure they compile.
+    dead_code,
 )]
 #![deny(clippy::collection_is_never_read)]

@@ -689,6 +692,7 @@ fn test_gen() {

    #[derive(Serialize, Deserialize)]
    #[serde(untagged)]
+    #[allow(dead_code)]
    pub enum UntaggedNewtypeVariantWith {
        Newtype(
            #[serde(serialize_with = "ser_x")]
@@ -699,6 +703,7 @@ fn test_gen() {

    #[derive(Serialize, Deserialize)]
    #[serde(transparent)]
+    #[allow(dead_code)]
    pub struct TransparentWith {
        #[serde(serialize_with = "ser_x")]
        #[serde(deserialize_with = "de_x")]
@@ -707,6 +712,7 @@ fn test_gen() {

    #[derive(Deserialize)]
    #[serde(untagged)]
+    #[allow(dead_code)]
    pub enum UntaggedWithBorrow<'a> {
        Single(
            #[serde(borrow)]
@@ -805,6 +811,8 @@ fn test_gen() {
        pub vec: Vec<Self>,
    }

+    assert_ser::<Struct>();
+
    #[derive(Deserialize)]
    #[serde(bound(deserialize = "[&'de str; N]: Copy"))]
    pub struct GenericUnitStruct<const N: usize>;
@@ -1,4 +1,4 @@
-#![allow(clippy::redundant_field_names)]
+#![allow(clippy::redundant_field_names, dead_code)]

 use serde_derive::{Deserialize, Serialize};

@@ -1,4 +1,4 @@
-#![allow(clippy::used_underscore_binding)]
+#![allow(clippy::used_underscore_binding, dead_code)]

 use serde_derive::{Deserialize, Serialize};

@@ -1,4 +1,5 @@
 #![allow(
+    clippy::elidable_lifetime_names,
    clippy::extra_unused_type_parameters,
    clippy::needless_lifetimes,
    clippy::type_repetition_in_bounds
@@ -7,18 +7,18 @@ error[E0425]: cannot find value `__FAIL__` in this scope
 warning: unreachable pattern
  --> tests/ui/conflict/alias-enum.rs:13:9
   |
-8  |         #[serde(alias = "a", alias = "b", alias = "c")]
+ 8 |         #[serde(alias = "a", alias = "b", alias = "c")]
   |                                      --- matches all the relevant values
 ...
 13 |         b: (),
   |         ^ no value can reach this
   |
-   = note: `#[warn(unreachable_patterns)]` on by default
+   = note: `#[warn(unreachable_patterns)]` (part of `#[warn(unused)]`) on by default

 warning: unreachable pattern
  --> tests/ui/conflict/alias-enum.rs:12:25
   |
-8  |         #[serde(alias = "a", alias = "b", alias = "c")]
+ 8 |         #[serde(alias = "a", alias = "b", alias = "c")]
   |                                                   --- matches all the relevant values
 ...
 12 |         #[serde(alias = "c")]
@@ -7,13 +7,13 @@ error[E0425]: cannot find value `__FAIL__` in this scope
 warning: unreachable pattern
  --> tests/ui/conflict/alias.rs:10:5
   |
-5  |     #[serde(alias = "a", alias = "b", alias = "c")]
+ 5 |     #[serde(alias = "a", alias = "b", alias = "c")]
   |                                  --- matches all the relevant values
 ...
 10 |     b: (),
   |     ^ no value can reach this
   |
-   = note: `#[warn(unreachable_patterns)]` on by default
+   = note: `#[warn(unreachable_patterns)]` (part of `#[warn(unused)]`) on by default

 warning: unreachable pattern
 --> tests/ui/conflict/alias.rs:9:21
@@ -1,11 +1,11 @@
 error: variant field name `conflict` conflicts with internal tag
  --> tests/ui/conflict/internal-tag-alias.rs:4:1
   |
-4  | / #[serde(tag = "conflict")]
-5  | | enum E {
-6  | |     A {
-7  | |         #[serde(alias = "conflict")]
-8  | |         x: (),
-9  | |     },
+ 4 | / #[serde(tag = "conflict")]
+ 5 | | enum E {
+ 6 | |     A {
+ 7 | |         #[serde(alias = "conflict")]
+ 8 | |         x: (),
+ 9 | |     },
 10 | | }
   | |_^
@@ -1,11 +1,11 @@
 error: variant field name `conflict` conflicts with internal tag
  --> tests/ui/conflict/internal-tag.rs:4:1
   |
-4  | / #[serde(tag = "conflict")]
-5  | | enum E {
-6  | |     A {
-7  | |         #[serde(rename = "conflict")]
-8  | |         x: (),
-9  | |     },
+ 4 | / #[serde(tag = "conflict")]
+ 5 | | enum E {
+ 6 | |     A {
+ 7 | |         #[serde(rename = "conflict")]
+ 8 | |         x: (),
+ 9 | |     },
 10 | | }
   | |_^
@@ -1,7 +1,7 @@
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_adjacently_tagged.rs:10:33
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `i8`
@@ -13,7 +13,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_adjacently_tagged.rs:12:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `u8`
@@ -25,7 +25,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_adjacently_tagged.rs:15:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `i8`
@@ -13,7 +13,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_externally_tagged.rs:11:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `u8`
@@ -25,7 +25,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_externally_tagged.rs:14:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `i8`
@@ -1,7 +1,7 @@
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_internally_tagged.rs:12:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `u8`
@@ -13,7 +13,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_internally_tagged.rs:15:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `i8`
@@ -1,7 +1,7 @@
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_untagged.rs:10:33
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `i8`
@@ -13,7 +13,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_untagged.rs:12:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `u8`
@@ -25,7 +25,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_enum_untagged.rs:15:27
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `i8`
@@ -2,10 +2,7 @@ error[E0308]: mismatched types
 --> tests/ui/default-attribute/incorrect_type_newtype.rs:6:19
  |
 6 | #[serde(default = "main")]
-  |                   ^^^^^^
-  |                   |
-  |                   expected `Newtype`, found `()`
-  |                   expected due to this
+  |                   ^^^^^^ expected `Newtype`, found `()`

 error[E0308]: `match` arms have incompatible types
 --> tests/ui/default-attribute/incorrect_type_newtype.rs:7:34
@@ -2,10 +2,7 @@ error[E0308]: mismatched types
 --> tests/ui/default-attribute/incorrect_type_struct.rs:6:19
  |
 6 | #[serde(default = "main")]
-  |                   ^^^^^^
-  |                   |
-  |                   expected `Struct`, found `()`
-  |                   expected due to this
+  |                   ^^^^^^ expected `Struct`, found `()`

 error[E0308]: `match` arms have incompatible types
 --> tests/ui/default-attribute/incorrect_type_struct.rs:8:23
@@ -22,7 +19,7 @@ error[E0308]: `match` arms have incompatible types
 error[E0308]: `match` arms have incompatible types
  --> tests/ui/default-attribute/incorrect_type_struct.rs:11:23
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          -----------
   |          |
   |          this is found to be of type `i8`
@@ -51,7 +48,7 @@ error[E0308]: mismatched types
 error[E0308]: mismatched types
  --> tests/ui/default-attribute/incorrect_type_struct.rs:11:23
   |
-5  | #[derive(Deserialize)]
+ 5 | #[derive(Deserialize)]
   |          ----------- expected due to the type of this binding
 ...
 11 |     #[serde(default = "main")]
@@ -2,10 +2,7 @@ error[E0308]: mismatched types
 --> tests/ui/default-attribute/incorrect_type_tuple.rs:6:19
  |
 6 | #[serde(default = "main")]
-  |                   ^^^^^^
-  |                   |
-  |                   expected `Tuple`, found `()`
-  |                   expected due to this
+  |                   ^^^^^^ expected `Tuple`, found `()`

 error[E0308]: `match` arms have incompatible types
 --> tests/ui/default-attribute/incorrect_type_tuple.rs:7:36
@@ -1,11 +1,11 @@
 error: #[serde(transparent)] requires at least one field that is neither skipped nor has a default
  --> tests/ui/transparent/de_at_least_one.rs:4:1
   |
-4  | / #[serde(transparent)]
-5  | | struct S {
-6  | |     #[serde(skip)]
-7  | |     a: u8,
-8  | |     #[serde(default)]
-9  | |     b: u8,
+ 4 | / #[serde(transparent)]
+ 5 | | struct S {
+ 6 | |     #[serde(skip)]
+ 7 | |     a: u8,
+ 8 | |     #[serde(default)]
+ 9 | |     b: u8,
 10 | | }
   | |_^
@@ -0,0 +1,6 @@
+struct MyStruct;
+
+fn main() {
+    serde_test::assert_ser_tokens(&MyStruct, &[]);
+    serde_test::assert_de_tokens(&MyStruct, &[]);
+}
@@ -0,0 +1,113 @@
+error[E0277]: the trait bound `MyStruct: serde::Serialize` is not satisfied
+ --> tests/ui/unimplemented/required_by_dependency.rs:4:35
+  |
+4 |     serde_test::assert_ser_tokens(&MyStruct, &[]);
+  |     ----------------------------- ^^^^^^^^^ unsatisfied trait bound
+  |     |
+  |     required by a bound introduced by this call
+  |
+help: the trait `serde_core::ser::Serialize` is not implemented for `MyStruct`
+ --> tests/ui/unimplemented/required_by_dependency.rs:1:1
+  |
+1 | struct MyStruct;
+  | ^^^^^^^^^^^^^^^
+  = note: for local types consider adding `#[derive(serde::Serialize)]` to your `MyStruct` type
+  = note: for types from other crates check whether the crate offers a `serde` feature flag
+  = help: the following other types implement trait `serde_core::ser::Serialize`:
+            &'a T
+            &'a mut T
+            ()
+            (T,)
+            (T0, T1)
+            (T0, T1, T2)
+            (T0, T1, T2, T3)
+            (T0, T1, T2, T3, T4)
+          and $N others
+note: required by a bound in `assert_ser_tokens`
+ --> $CARGO/serde_test-$VERSION/src/assert.rs
+  |
+  | pub fn assert_ser_tokens<T>(value: &T, tokens: &[Token])
+  |        ----------------- required by a bound in this function
+  | where
+  |     T: ?Sized + Serialize,
+  |                 ^^^^^^^^^ required by this bound in `assert_ser_tokens`
+
+error[E0277]: the trait bound `MyStruct: serde::Deserialize<'de>` is not satisfied
+ --> tests/ui/unimplemented/required_by_dependency.rs:5:34
+  |
+5 |     serde_test::assert_de_tokens(&MyStruct, &[]);
+  |     ---------------------------- ^^^^^^^^^ unsatisfied trait bound
+  |     |
+  |     required by a bound introduced by this call
+  |
+help: the trait `serde_core::de::Deserialize<'_>` is not implemented for `MyStruct`
+ --> tests/ui/unimplemented/required_by_dependency.rs:1:1
+  |
+1 | struct MyStruct;
+  | ^^^^^^^^^^^^^^^
+  = note: for local types consider adding `#[derive(serde::Deserialize)]` to your `MyStruct` type
+  = note: for types from other crates check whether the crate offers a `serde` feature flag
+  = help: the following other types implement trait `serde_core::de::Deserialize<'de>`:
+            &'a Path
+            &'a [u8]
+            &'a str
+            ()
+            (T,)
+            (T0, T1)
+            (T0, T1, T2)
+            (T0, T1, T2, T3)
+          and $N others
+note: required by a bound in `assert_de_tokens`
+ --> $CARGO/serde_test-$VERSION/src/assert.rs
+  |
+  | pub fn assert_de_tokens<'de, T>(value: &T, tokens: &'de [Token])
+  |        ---------------- required by a bound in this function
+  | where
+  |     T: Deserialize<'de> + PartialEq + Debug,
+  |        ^^^^^^^^^^^^^^^^ required by this bound in `assert_de_tokens`
+
+error[E0277]: can't compare `MyStruct` with `MyStruct`
+ --> tests/ui/unimplemented/required_by_dependency.rs:5:34
+  |
+5 |     serde_test::assert_de_tokens(&MyStruct, &[]);
+  |     ---------------------------- ^^^^^^^^^ no implementation for `MyStruct == MyStruct`
+  |     |
+  |     required by a bound introduced by this call
+  |
+  = help: the trait `PartialEq` is not implemented for `MyStruct`
+note: required by a bound in `assert_de_tokens`
+ --> $CARGO/serde_test-$VERSION/src/assert.rs
+  |
+  | pub fn assert_de_tokens<'de, T>(value: &T, tokens: &'de [Token])
+  |        ---------------- required by a bound in this function
+  | where
+  |     T: Deserialize<'de> + PartialEq + Debug,
+  |                           ^^^^^^^^^ required by this bound in `assert_de_tokens`
+help: consider annotating `MyStruct` with `#[derive(PartialEq)]`
+  |
+  1 + #[derive(PartialEq)]
+  2 | struct MyStruct;
+    |
+
+error[E0277]: `MyStruct` doesn't implement `Debug`
+ --> tests/ui/unimplemented/required_by_dependency.rs:5:34
+  |
+5 |     serde_test::assert_de_tokens(&MyStruct, &[]);
+  |     ---------------------------- ^^^^^^^^^ the trait `Debug` is not implemented for `MyStruct`
+  |     |
+  |     required by a bound introduced by this call
+  |
+  = note: add `#[derive(Debug)]` to `MyStruct` or manually `impl Debug for MyStruct`
+note: required by a bound in `assert_de_tokens`
+ --> $CARGO/serde_test-$VERSION/src/assert.rs
+  |
+  | pub fn assert_de_tokens<'de, T>(value: &T, tokens: &'de [Token])
+  |        ---------------- required by a bound in this function
+  | where
+  |     T: Deserialize<'de> + PartialEq + Debug,
+  |                                       ^^^^^ required by this bound in `assert_de_tokens`
+help: consider annotating `MyStruct` with `#[derive(Debug)]`
+  |
+  1 + #[derive(Debug)]
+  2 | struct MyStruct;
+    |
@@ -1,11 +1,16 @@
-error[E0277]: the trait bound `MyStruct: Serialize` is not satisfied
-  --> tests/ui/on_unimplemented.rs:21:15
+error[E0277]: the trait bound `MyStruct: serde::Serialize` is not satisfied
+  --> tests/ui/unimplemented/required_locally.rs:21:15
   |
 21 |     to_string(&MyStruct);
-   |     --------- ^^^^^^^^^ the trait `Serialize` is not implemented for `MyStruct`
+   |     --------- ^^^^^^^^^ unsatisfied trait bound
   |     |
   |     required by a bound introduced by this call
   |
+help: the trait `Serialize` is not implemented for `MyStruct`
+  --> tests/ui/unimplemented/required_locally.rs:18:1
+   |
+18 | struct MyStruct;
+   | ^^^^^^^^^^^^^^^
   = note: for local types consider adding `#[derive(serde::Serialize)]` to your `MyStruct` type
   = note: for types from other crates check whether the crate offers a `serde` feature flag
   = help: the following other types implement trait `Serialize`:
@@ -19,20 +24,25 @@ error[E0277]: the trait bound `MyStruct: Serialize` is not satisfied
             (T0, T1, T2, T3, T4)
           and $N others
 note: required by a bound in `to_string`
-  --> tests/ui/on_unimplemented.rs:6:8
+  --> tests/ui/unimplemented/required_locally.rs:6:8
   |
-4  | fn to_string<T>(_: &T) -> String
+ 4 | fn to_string<T>(_: &T) -> String
   |    --------- required by a bound in this function
-5  | where
-6  |     T: Serialize,
+ 5 | where
+ 6 |     T: Serialize,
   |        ^^^^^^^^^ required by this bound in `to_string`

-error[E0277]: the trait bound `MyStruct: Deserialize<'_>` is not satisfied
-  --> tests/ui/on_unimplemented.rs:22:23
+error[E0277]: the trait bound `MyStruct: serde::Deserialize<'de>` is not satisfied
+  --> tests/ui/unimplemented/required_locally.rs:22:23
   |
 22 |     let _: MyStruct = from_str("");
-   |                       ^^^^^^^^^^^^ the trait `Deserialize<'_>` is not implemented for `MyStruct`
+   |                       ^^^^^^^^^^^^ unsatisfied trait bound
   |
+help: the trait `Deserialize<'_>` is not implemented for `MyStruct`
+  --> tests/ui/unimplemented/required_locally.rs:18:1
+   |
+18 | struct MyStruct;
+   | ^^^^^^^^^^^^^^^
   = note: for local types consider adding `#[derive(serde::Deserialize)]` to your `MyStruct` type
   = note: for types from other crates check whether the crate offers a `serde` feature flag
   = help: the following other types implement trait `Deserialize<'de>`:
@@ -46,7 +56,7 @@ error[E0277]: the trait bound `MyStruct: Deserialize<'_>` is not satisfied
             (T0, T1, T2, T3)
           and $N others
 note: required by a bound in `from_str`
-  --> tests/ui/on_unimplemented.rs:13:8
+  --> tests/ui/unimplemented/required_locally.rs:13:8
   |
 11 | fn from_str<'de, T>(_: &'de str) -> T
   |    -------- required by a bound in this function
@@ -1,10 +1,10 @@
 error: variant `Struct` cannot have both #[serde(deserialize_with)] and a field `f1` marked with #[serde(skip_deserializing)]
  --> tests/ui/with-variant/skip_de_struct_field.rs:5:5
   |
-5  | /     #[serde(deserialize_with = "deserialize_some_other_variant")]
-6  | |     Struct {
-7  | |         #[serde(skip_deserializing)]
-8  | |         f1: String,
-9  | |         f2: u8,
+ 5 | /     #[serde(deserialize_with = "deserialize_some_other_variant")]
+ 6 | |     Struct {
+ 7 | |         #[serde(skip_deserializing)]
+ 8 | |         f1: String,
+ 9 | |         f2: u8,
 10 | |     },
   | |_____^
@@ -1,10 +1,10 @@
 error: variant `Struct` cannot have both #[serde(serialize_with)] and a field `f1` marked with #[serde(skip_serializing)]
  --> tests/ui/with-variant/skip_ser_struct_field.rs:5:5
   |
-5  | /     #[serde(serialize_with = "serialize_some_other_variant")]
-6  | |     Struct {
-7  | |         #[serde(skip_serializing)]
-8  | |         f1: String,
-9  | |         f2: u8,
+ 5 | /     #[serde(serialize_with = "serialize_some_other_variant")]
+ 6 | |     Struct {
+ 7 | |         #[serde(skip_serializing)]
+ 8 | |         f1: String,
+ 9 | |         f2: u8,
 10 | |     },
   | |_____^
@@ -1,10 +1,10 @@
 error: variant `Struct` cannot have both #[serde(serialize_with)] and a field `f1` marked with #[serde(skip_serializing_if)]
  --> tests/ui/with-variant/skip_ser_struct_field_if.rs:5:5
   |
-5  | /     #[serde(serialize_with = "serialize_some_newtype_variant")]
-6  | |     Struct {
-7  | |         #[serde(skip_serializing_if = "always")]
-8  | |         f1: String,
-9  | |         f2: u8,
+ 5 | /     #[serde(serialize_with = "serialize_some_newtype_variant")]
+ 6 | |     Struct {
+ 7 | |         #[serde(skip_serializing_if = "always")]
+ 8 | |         f1: String,
+ 9 | |         f2: u8,
 10 | |     },
   | |_____^
@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `&u8: Serializer` is not satisfied
+error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
  --> tests/ui/with/incorrect_type.rs:14:10
   |
 14 | #[derive(Serialize, Deserialize)]
@@ -13,7 +13,7 @@ error[E0277]: the trait bound `&u8: Serializer` is not satisfied
 note: required by a bound in `w::serialize`
  --> tests/ui/with/incorrect_type.rs:9:28
   |
-9  |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
+ 9 |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
   |                            ^^^^^^^^^^ required by this bound in `serialize`

 error[E0061]: this function takes 1 argument but 2 arguments were supplied
@@ -27,10 +27,10 @@ error[E0061]: this function takes 1 argument but 2 arguments were supplied
 note: function defined here
  --> tests/ui/with/incorrect_type.rs:9:12
   |
-9  |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
+ 9 |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
   |            ^^^^^^^^^

-error[E0277]: the trait bound `&u8: Serializer` is not satisfied
+error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
  --> tests/ui/with/incorrect_type.rs:15:25
   |
 15 | struct W(#[serde(with = "w")] u8, u8);
@@ -49,7 +49,7 @@ error[E0308]: `?` operator has incompatible types
   |
   = note: `?` operator cannot convert from `()` to `u8`

-error[E0277]: the trait bound `&u8: Serializer` is not satisfied
+error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
  --> tests/ui/with/incorrect_type.rs:17:10
   |
 17 | #[derive(Serialize, Deserialize)]
@@ -64,7 +64,7 @@ error[E0277]: the trait bound `&u8: Serializer` is not satisfied
 note: required by a bound in `w::serialize`
  --> tests/ui/with/incorrect_type.rs:9:28
   |
-9  |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
+ 9 |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
   |                            ^^^^^^^^^^ required by this bound in `serialize`

 error[E0061]: this function takes 1 argument but 2 arguments were supplied
@@ -78,10 +78,10 @@ error[E0061]: this function takes 1 argument but 2 arguments were supplied
 note: function defined here
  --> tests/ui/with/incorrect_type.rs:9:12
   |
-9  |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
+ 9 |     pub fn serialize<T, S: Serializer>(_: S) -> Result<S::Ok, S::Error> {
   |            ^^^^^^^^^

-error[E0277]: the trait bound `&u8: Serializer` is not satisfied
+error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
  --> tests/ui/with/incorrect_type.rs:18:35
   |
 18 | struct S(#[serde(serialize_with = "w::serialize")] u8, u8);