Release 1.0.226

Remove code duplication when deriving Deserialize for adjacently tagged enums

CONTRIBUTING.md

@@ -27,11 +27,11 @@ pull request with your changes. If anything does not pass, typically it will be
 easier to iterate and fix it locally than waiting for the CI servers to run
 tests for you.
 
-##### In the [`serde`] directory
+##### In the [`serde_core`] directory
 
 ```sh
 # Test all the example code in Serde documentation
-cargo test --features derive
+cargo test
 ```
 
 ##### In the [`test_suite`] directory
@@ -43,7 +43,7 @@ cargo +nightly test --features unstable
 
 Note that this test suite currently only supports running on a nightly compiler.
 
-[`serde`]: https://github.com/serde-rs/serde/tree/master/serde
+[`serde_core`]: https://github.com/serde-rs/serde/tree/master/serde_core
 [`test_suite`]: https://github.com/serde-rs/serde/tree/master/test_suite
 
 ## Conduct

serde/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde"
-version = "1.0.222"
+version = "1.0.226"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
 categories = ["encoding", "no-std", "no-std::no-alloc"]
@@ -15,7 +15,7 @@ repository = "https://github.com/serde-rs/serde"
 rust-version = "1.56"
 
 [dependencies]
-serde_core = { version = "=1.0.222", path = "../serde_core", default-features = false, features = ["result"] }
+serde_core = { version = "=1.0.226", path = "../serde_core", default-features = false, features = ["result"] }
 serde_derive = { version = "1", optional = true, path = "../serde_derive" }
 
 [package.metadata.playground]
@@ -26,6 +26,7 @@ features = ["derive", "rc", "unstable"]
 targets = ["x86_64-unknown-linux-gnu"]
 rustdoc-args = [
     "--generate-link-to-definition",
+    "--generate-macro-expansion",
     "--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",

serde/build.rs

@@ -1,19 +1,36 @@
 use std::env;
+use std::fs;
+use std::path::PathBuf;
 use std::process::Command;
 use std::str;
 
+const PRIVATE: &str = "\
+#[doc(hidden)]
+pub mod __private$$ {
+    #[doc(hidden)]
+    pub use crate::private::*;
+}
+use serde_core::__private$$ as serde_core_private;
+";
+
 // 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 out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let patch_version = env::var("CARGO_PKG_VERSION_PATCH").unwrap();
+    let module = PRIVATE.replace("$$", &patch_version);
+    fs::write(out_dir.join("private.rs"), module).unwrap();
+
     let minor = match rustc_minor_version() {
         Some(minor) => minor,
         None => return,
     };
 
     if minor >= 77 {
+        println!("cargo:rustc-check-cfg=cfg(no_diagnostic_namespace)");
         println!("cargo:rustc-check-cfg=cfg(no_serde_derive)");
     }
 
@@ -21,6 +38,12 @@ fn main() {
     if minor < 61 {
         println!("cargo:rustc-cfg=no_serde_derive");
     }
+
+    // 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");
+    }
 }
 
 fn rustc_minor_version() -> Option<u32> {

serde/src/lib.rs

@@ -95,7 +95,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.222")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.226")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Show which crate feature enables conditionally compiled APIs in documentation.
@@ -239,8 +239,9 @@ mod integer128;
 
 // Used by generated code and doc tests. Not public API.
 #[doc(hidden)]
-#[path = "private/mod.rs"]
-pub mod __private;
+mod private;
+
+include!(concat!(env!("OUT_DIR"), "/private.rs"));
 
 // Re-export #[derive(Serialize, Deserialize)].
 //

serde/src/private/de.rs

@@ -17,7 +17,7 @@ pub use self::content::{
     UntaggedUnitVisitor,
 };
 
-pub use serde_core::__private::InPlaceSeed;
+pub use crate::serde_core_private::InPlaceSeed;
 
 /// If the missing field is of type `Option<T>` then treat is as `None`,
 /// otherwise it is an error.
@@ -28,6 +28,7 @@ where
 {
     struct MissingFieldDeserializer<E>(&'static str, PhantomData<E>);
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> Deserializer<'de> for MissingFieldDeserializer<E>
     where
         E: Error,
@@ -67,6 +68,7 @@ where
 {
     struct CowStrVisitor;
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a> Visitor<'a> for CowStrVisitor {
         type Value = Cow<'a, str>;
 
@@ -140,6 +142,7 @@ where
 {
     struct CowBytesVisitor;
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a> Visitor<'a> for CowBytesVisitor {
         type Value = Cow<'a, [u8]>;
 
@@ -213,8 +216,8 @@ mod content {
         self, Deserialize, DeserializeSeed, Deserializer, EnumAccess, Expected, IgnoredAny,
         MapAccess, SeqAccess, Unexpected, Visitor,
     };
-    use serde_core::__private::size_hint;
-    pub use serde_core::__private::Content;
+    use crate::serde_core_private::size_hint;
+    pub use crate::serde_core_private::Content;
 
     pub fn content_as_str<'a, 'de>(content: &'a Content<'de>) -> Option<&'a str> {
         match *content {
@@ -294,6 +297,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> DeserializeSeed<'de> for ContentVisitor<'de> {
         type Value = Content<'de>;
 
@@ -305,6 +309,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> Visitor<'de> for ContentVisitor<'de> {
         type Value = Content<'de>;
 
@@ -530,6 +535,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> DeserializeSeed<'de> for TagOrContentVisitor<'de> {
         type Value = TagOrContent<'de>;
 
@@ -543,6 +549,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> Visitor<'de> for TagOrContentVisitor<'de> {
         type Value = TagOrContent<'de>;
 
@@ -824,6 +831,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, T> Visitor<'de> for TaggedContentVisitor<T>
     where
         T: Deserialize<'de>,
@@ -894,6 +902,7 @@ mod content {
         pub content: &'static str,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> DeserializeSeed<'de> for TagOrContentFieldVisitor {
         type Value = TagOrContentField;
 
@@ -905,6 +914,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> Visitor<'de> for TagOrContentFieldVisitor {
         type Value = TagOrContentField;
 
@@ -971,6 +981,7 @@ mod content {
         pub content: &'static str,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> DeserializeSeed<'de> for TagContentOtherFieldVisitor {
         type Value = TagContentOtherField;
 
@@ -982,6 +993,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de> Visitor<'de> for TagContentOtherFieldVisitor {
         type Value = TagContentOtherField;
 
@@ -1104,6 +1116,7 @@ mod content {
 
     /// Used when deserializing an internally tagged enum because the content
     /// will be used exactly once.
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> Deserializer<'de> for ContentDeserializer<'de, E>
     where
         E: de::Error,
@@ -1523,6 +1536,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> Deserializer<'de> for SeqDeserializer<'de, E>
     where
         E: de::Error,
@@ -1545,6 +1559,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> SeqAccess<'de> for SeqDeserializer<'de, E>
     where
         E: de::Error,
@@ -1571,6 +1586,7 @@ mod content {
 
     struct ExpectedInSeq(usize);
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl Expected for ExpectedInSeq {
         fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
             if self.0 == 1 {
@@ -1630,6 +1646,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> Deserializer<'de> for MapDeserializer<'de, E>
     where
         E: de::Error,
@@ -1669,6 +1686,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> MapAccess<'de> for MapDeserializer<'de, E>
     where
         E: de::Error,
@@ -1723,6 +1741,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> SeqAccess<'de> for MapDeserializer<'de, E>
     where
         E: de::Error,
@@ -1749,6 +1768,7 @@ mod content {
 
     struct PairDeserializer<'de, E>(Content<'de>, Content<'de>, PhantomData<E>);
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> Deserializer<'de> for PairDeserializer<'de, E>
     where
         E: de::Error,
@@ -1800,6 +1820,7 @@ mod content {
 
     struct PairVisitor<'de, E>(Option<Content<'de>>, Option<Content<'de>>, PhantomData<E>);
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> SeqAccess<'de> for PairVisitor<'de, E>
     where
         E: de::Error,
@@ -1832,6 +1853,7 @@ mod content {
 
     struct ExpectedInMap(usize);
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl Expected for ExpectedInMap {
         fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
             if self.0 == 1 {
@@ -1864,6 +1886,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> de::EnumAccess<'de> for EnumDeserializer<'de, E>
     where
         E: de::Error,
@@ -1892,6 +1915,7 @@ mod content {
         err: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> de::VariantAccess<'de> for VariantDeserializer<'de, E>
     where
         E: de::Error,
@@ -2046,6 +2070,7 @@ mod content {
 
     /// Used when deserializing an untagged enum because the content may need
     /// to be used more than once.
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, 'a, E> Deserializer<'de> for ContentRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2424,8 +2449,10 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de: 'a, E> Copy for ContentRefDeserializer<'a, 'de, E> {}
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de: 'a, E> Clone for ContentRefDeserializer<'a, 'de, E> {
         fn clone(&self) -> Self {
             *self
@@ -2467,6 +2494,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de, E> Deserializer<'de> for SeqRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2489,6 +2517,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de, E> SeqAccess<'de> for SeqRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2563,6 +2592,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de, E> Deserializer<'de> for MapRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2602,6 +2632,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de, E> MapAccess<'de> for MapRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2656,6 +2687,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de, E> SeqAccess<'de> for MapRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2682,6 +2714,7 @@ mod content {
 
     struct PairRefDeserializer<'a, 'de, E>(&'a Content<'de>, &'a Content<'de>, PhantomData<E>);
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de, E> Deserializer<'de> for PairRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2737,6 +2770,7 @@ mod content {
         PhantomData<E>,
     );
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'a, 'de, E> SeqAccess<'de> for PairRefVisitor<'a, 'de, E>
     where
         E: de::Error,
@@ -2776,6 +2810,7 @@ mod content {
         err: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, 'a, E> de::EnumAccess<'de> for EnumRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2804,6 +2839,7 @@ mod content {
         err: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, 'a, E> de::VariantAccess<'de> for VariantRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2890,6 +2926,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, E> de::IntoDeserializer<'de, E> for ContentDeserializer<'de, E>
     where
         E: de::Error,
@@ -2901,6 +2938,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, 'a, E> de::IntoDeserializer<'de, E> for ContentRefDeserializer<'a, 'de, E>
     where
         E: de::Error,
@@ -2930,6 +2968,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, 'a> Visitor<'de> for InternallyTaggedUnitVisitor<'a> {
         type Value = ();
 
@@ -2975,6 +3014,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<'de, 'a> Visitor<'de> for UntaggedUnitVisitor<'a> {
         type Value = ();
 
@@ -3022,6 +3062,7 @@ pub trait IdentifierDeserializer<'de, E: Error> {
 
 pub struct Borrowed<'de, T: 'de + ?Sized>(pub &'de T);
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'de, E> IdentifierDeserializer<'de, E> for u64
 where
     E: Error,
@@ -3038,6 +3079,7 @@ pub struct StrDeserializer<'a, E> {
     marker: PhantomData<E>,
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'de, 'a, E> Deserializer<'de> for StrDeserializer<'a, E>
 where
     E: Error,
@@ -3063,6 +3105,7 @@ pub struct BorrowedStrDeserializer<'de, E> {
     marker: PhantomData<E>,
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'de, E> Deserializer<'de> for BorrowedStrDeserializer<'de, E>
 where
     E: Error,
@@ -3083,6 +3126,7 @@ where
     }
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, E> IdentifierDeserializer<'a, E> for &'a str
 where
     E: Error,
@@ -3097,6 +3141,7 @@ where
     }
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'de, E> IdentifierDeserializer<'de, E> for Borrowed<'de, str>
 where
     E: Error,
@@ -3111,6 +3156,7 @@ where
     }
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, E> IdentifierDeserializer<'a, E> for &'a [u8]
 where
     E: Error,
@@ -3122,6 +3168,7 @@ where
     }
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'de, E> IdentifierDeserializer<'de, E> for Borrowed<'de, [u8]>
 where
     E: Error,
@@ -3164,6 +3211,7 @@ macro_rules! forward_to_deserialize_other {
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, 'de, E> Deserializer<'de> for FlatMapDeserializer<'a, 'de, E>
 where
     E: Error,
@@ -3300,6 +3348,7 @@ struct FlatMapAccess<'a, 'de: 'a, E> {
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, 'de, E> MapAccess<'de> for FlatMapAccess<'a, 'de, E>
 where
     E: Error,
@@ -3344,6 +3393,7 @@ struct FlatStructAccess<'a, 'de: 'a, E> {
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, 'de, E> MapAccess<'de> for FlatStructAccess<'a, 'de, E>
 where
     E: Error,
@@ -3407,6 +3457,7 @@ pub struct AdjacentlyTaggedEnumVariantVisitor<F> {
     fields_enum: PhantomData<F>,
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'de, F> Visitor<'de> for AdjacentlyTaggedEnumVariantVisitor<F>
 where
     F: Deserialize<'de>,
@@ -3427,6 +3478,7 @@ where
     }
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'de, F> DeserializeSeed<'de> for AdjacentlyTaggedEnumVariantSeed<F>
 where
     F: Deserialize<'de>,

serde/src/private/mod.rs

@@ -12,7 +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 serde_core::__private::string::from_utf8_lossy;
+pub use crate::serde_core_private::string::from_utf8_lossy;
 
 #[cfg(any(feature = "alloc", feature = "std"))]
 pub use crate::lib::{ToString, Vec};

serde/src/private/ser.rs

@@ -58,6 +58,7 @@ enum Unsupported {
     Enum,
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl Display for Unsupported {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         match *self {
@@ -89,6 +90,7 @@ where
     }
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<S> Serializer for TaggedSerializer<S>
 where
     S: Serializer,
@@ -355,6 +357,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<M> ser::SerializeTupleVariant for SerializeTupleVariantAsMapValue<M>
     where
         M: ser::SerializeMap,
@@ -395,6 +398,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<M> ser::SerializeStructVariant for SerializeStructVariantAsMapValue<M>
     where
         M: ser::SerializeMap,
@@ -462,6 +466,7 @@ mod content {
         ),
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl Serialize for Content {
         fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where
@@ -554,6 +559,7 @@ mod content {
         }
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> Serializer for ContentSerializer<E>
     where
         E: ser::Error,
@@ -765,6 +771,7 @@ mod content {
         error: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> ser::SerializeSeq for SerializeSeq<E>
     where
         E: ser::Error,
@@ -791,6 +798,7 @@ mod content {
         error: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> ser::SerializeTuple for SerializeTuple<E>
     where
         E: ser::Error,
@@ -818,6 +826,7 @@ mod content {
         error: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> ser::SerializeTupleStruct for SerializeTupleStruct<E>
     where
         E: ser::Error,
@@ -847,6 +856,7 @@ mod content {
         error: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> ser::SerializeTupleVariant for SerializeTupleVariant<E>
     where
         E: ser::Error,
@@ -879,6 +889,7 @@ mod content {
         error: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> ser::SerializeMap for SerializeMap<E>
     where
         E: ser::Error,
@@ -930,6 +941,7 @@ mod content {
         error: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> ser::SerializeStruct for SerializeStruct<E>
     where
         E: ser::Error,
@@ -959,6 +971,7 @@ mod content {
         error: PhantomData<E>,
     }
 
+    #[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
     impl<E> ser::SerializeStructVariant for SerializeStructVariant<E>
     where
         E: ser::Error,
@@ -1003,6 +1016,7 @@ where
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, M> Serializer for FlatMapSerializer<'a, M>
 where
     M: SerializeMap + 'a,
@@ -1184,6 +1198,7 @@ where
 pub struct FlatMapSerializeMap<'a, M: 'a>(&'a mut M);
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, M> ser::SerializeMap for FlatMapSerializeMap<'a, M>
 where
     M: SerializeMap + 'a,
@@ -1222,6 +1237,7 @@ where
 pub struct FlatMapSerializeStruct<'a, M: 'a>(&'a mut M);
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, M> ser::SerializeStruct for FlatMapSerializeStruct<'a, M>
 where
     M: SerializeMap + 'a,
@@ -1263,6 +1279,7 @@ where
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, M> ser::SerializeTupleVariant for FlatMapSerializeTupleVariantAsMapValue<'a, M>
 where
     M: SerializeMap + 'a,
@@ -1309,6 +1326,7 @@ where
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, M> ser::SerializeStructVariant for FlatMapSerializeStructVariantAsMapValue<'a, M>
 where
     M: SerializeMap + 'a,
@@ -1339,6 +1357,7 @@ pub struct AdjacentlyTaggedEnumVariant {
     pub variant_name: &'static str,
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl Serialize for AdjacentlyTaggedEnumVariant {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -1352,6 +1371,7 @@ impl Serialize for AdjacentlyTaggedEnumVariant {
 // that is not recognized.
 pub struct CannotSerializeVariant<T>(pub T);
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<T> Display for CannotSerializeVariant<T>
 where
     T: Debug,

serde_core/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_core"
-version = "1.0.222"
+version = "1.0.226"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
 categories = ["encoding", "no-std", "no-std::no-alloc"]
@@ -25,6 +25,7 @@ features = ["rc", "result", "unstable"]
 targets = ["x86_64-unknown-linux-gnu"]
 rustdoc-args = [
     "--generate-link-to-definition",
+    "--generate-macro-expansion",
     "--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",
@@ -36,7 +37,7 @@ rustdoc-args = [
 # 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 = "=1.0.222", path = "../serde_derive" }
+serde_derive = { version = "=1.0.226", path = "../serde_derive" }
 
 
 ### FEATURES #################################################################

serde_core/build.rs

@@ -1,13 +1,28 @@
 use std::env;
+use std::fs;
+use std::path::PathBuf;
 use std::process::Command;
 use std::str;
 
+const PRIVATE: &str = "\
+#[doc(hidden)]
+pub mod __private$$ {
+    #[doc(hidden)]
+    pub use crate::private::*;
+}
+";
+
 // 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 out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let patch_version = env::var("CARGO_PKG_VERSION_PATCH").unwrap();
+    let module = PRIVATE.replace("$$", &patch_version);
+    fs::write(out_dir.join("private.rs"), module).unwrap();
+
     let minor = match rustc_minor_version() {
         Some(minor) => minor,
         None => return,

serde_core/src/lib.rs

@@ -35,7 +35,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.222")]
+#![doc(html_root_url = "https://docs.rs/serde_core/1.0.226")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Show which crate feature enables conditionally compiled APIs in documentation.
@@ -252,9 +252,18 @@ 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;
+mod private;
+
+// Used by declarative macro generated code. Not public API.
+#[doc(hidden)]
+pub mod __private {
+    #[doc(hidden)]
+    pub use crate::private::doc;
+    #[doc(hidden)]
+    pub use core::result::Result;
+}
+
+include!(concat!(env!("OUT_DIR"), "/private.rs"));
 
 #[cfg(all(not(feature = "std"), no_core_error))]
 mod std_error;

serde_core/src/private/doc.rs

@@ -8,6 +8,7 @@ use crate::ser;
 #[derive(Debug)]
 pub struct Error;
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl ser::Error for Error {
     fn custom<T>(_: T) -> Self
     where
@@ -18,12 +19,14 @@ impl ser::Error for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl error::Error for Error {
     fn description(&self) -> &str {
         unimplemented!()
     }
 }
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl Display for Error {
     fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
         unimplemented!()

serde_core/src/private/seed.rs

@@ -5,6 +5,7 @@ use crate::de::{Deserialize, DeserializeSeed, Deserializer};
 /// Wraps a mutable reference and calls deserialize_in_place on it.
 pub struct InPlaceSeed<'a, T: 'a>(pub &'a mut T);
 
+#[cfg_attr(not(no_diagnostic_namespace), diagnostic::do_not_recommend)]
 impl<'a, 'de, T> DeserializeSeed<'de> for InPlaceSeed<'a, T>
 where
     T: Deserialize<'de>,

serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.222"
+version = "1.0.226"
 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)]"
@@ -34,6 +34,7 @@ serde = { version = "1", path = "../serde" }
 targets = ["x86_64-unknown-linux-gnu"]
 rustdoc-args = [
     "--generate-link-to-definition",
+    "--generate-macro-expansion",
     "--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",

serde_derive/src/deprecated.rs

@@ -0,0 +1,56 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+
+pub fn allow_deprecated(input: &syn::DeriveInput) -> Option<TokenStream> {
+    if should_allow_deprecated(input) {
+        Some(quote! { #[allow(deprecated)] })
+    } else {
+        None
+    }
+}
+
+/// Determine if an `#[allow(deprecated)]` should be added to the derived impl.
+///
+/// This should happen if the derive input or an enum variant it contains has
+/// one of:
+///   - `#[deprecated]`
+///   - `#[allow(deprecated)]`
+fn should_allow_deprecated(input: &syn::DeriveInput) -> bool {
+    if contains_deprecated(&input.attrs) {
+        return true;
+    }
+    if let syn::Data::Enum(data_enum) = &input.data {
+        for variant in &data_enum.variants {
+            if contains_deprecated(&variant.attrs) {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+/// Check whether the given attributes contains one of:
+///   - `#[deprecated]`
+///   - `#[allow(deprecated)]`
+fn contains_deprecated(attrs: &[syn::Attribute]) -> bool {
+    for attr in attrs {
+        if attr.path().is_ident("deprecated") {
+            return true;
+        }
+        if let syn::Meta::List(meta_list) = &attr.meta {
+            if meta_list.path.is_ident("allow") {
+                let mut allow_deprecated = false;
+                let _ = meta_list.parse_nested_meta(|meta| {
+                    if meta.path.is_ident("deprecated") {
+                        allow_deprecated = true;
+                    }
+                    Ok(())
+                });
+                if allow_deprecated {
+                    return true;
+                }
+            }
+        }
+    }
+    false
+}

serde_derive/src/internals/ast.rs

@@ -1,6 +1,7 @@
 //! A Serde ast, parsed from the Syn ast and ready to generate Rust code.
 
 use crate::internals::{attr, check, Ctxt, Derive};
+use proc_macro2::Ident;
 use syn::punctuated::Punctuated;
 use syn::Token;
 
@@ -62,13 +63,17 @@ impl<'a> Container<'a> {
         cx: &Ctxt,
         item: &'a syn::DeriveInput,
         derive: Derive,
+        private: &Ident,
     ) -> Option<Container<'a>> {
         let attrs = attr::Container::from_ast(cx, item);
 
         let mut data = match &item.data {
-            syn::Data::Enum(data) => Data::Enum(enum_from_ast(cx, &data.variants, attrs.default())),
+            syn::Data::Enum(data) => {
+                Data::Enum(enum_from_ast(cx, &data.variants, attrs.default(), private))
+            }
             syn::Data::Struct(data) => {
-                let (style, fields) = struct_from_ast(cx, &data.fields, None, attrs.default());
+                let (style, fields) =
+                    struct_from_ast(cx, &data.fields, None, attrs.default(), private);
                 Data::Struct(style, fields)
             }
             syn::Data::Union(_) => {
@@ -129,13 +134,19 @@ fn enum_from_ast<'a>(
     cx: &Ctxt,
     variants: &'a Punctuated<syn::Variant, Token![,]>,
     container_default: &attr::Default,
+    private: &Ident,
 ) -> Vec<Variant<'a>> {
     let variants: Vec<Variant> = variants
         .iter()
         .map(|variant| {
             let attrs = attr::Variant::from_ast(cx, variant);
-            let (style, fields) =
-                struct_from_ast(cx, &variant.fields, Some(&attrs), container_default);
+            let (style, fields) = struct_from_ast(
+                cx,
+                &variant.fields,
+                Some(&attrs),
+                container_default,
+                private,
+            );
             Variant {
                 ident: variant.ident.clone(),
                 attrs,
@@ -165,19 +176,20 @@ fn struct_from_ast<'a>(
     fields: &'a syn::Fields,
     attrs: Option<&attr::Variant>,
     container_default: &attr::Default,
+    private: &Ident,
 ) -> (Style, Vec<Field<'a>>) {
     match fields {
         syn::Fields::Named(fields) => (
             Style::Struct,
-            fields_from_ast(cx, &fields.named, attrs, container_default),
+            fields_from_ast(cx, &fields.named, attrs, container_default, private),
         ),
         syn::Fields::Unnamed(fields) if fields.unnamed.len() == 1 => (
             Style::Newtype,
-            fields_from_ast(cx, &fields.unnamed, attrs, container_default),
+            fields_from_ast(cx, &fields.unnamed, attrs, container_default, private),
         ),
         syn::Fields::Unnamed(fields) => (
             Style::Tuple,
-            fields_from_ast(cx, &fields.unnamed, attrs, container_default),
+            fields_from_ast(cx, &fields.unnamed, attrs, container_default, private),
         ),
         syn::Fields::Unit => (Style::Unit, Vec::new()),
     }
@@ -188,6 +200,7 @@ fn fields_from_ast<'a>(
     fields: &'a Punctuated<syn::Field, Token![,]>,
     attrs: Option<&attr::Variant>,
     container_default: &attr::Default,
+    private: &Ident,
 ) -> Vec<Field<'a>> {
     fields
         .iter()
@@ -197,7 +210,7 @@ fn fields_from_ast<'a>(
                 Some(ident) => syn::Member::Named(ident.clone()),
                 None => syn::Member::Unnamed(i.into()),
             },
-            attrs: attr::Field::from_ast(cx, i, field, attrs, container_default),
+            attrs: attr::Field::from_ast(cx, i, field, attrs, container_default, private),
             ty: &field.ty,
             original: field,
         })

serde_derive/src/internals/attr.rs

@@ -3,14 +3,13 @@ use crate::internals::symbol::*;
 use crate::internals::{ungroup, Ctxt};
 use proc_macro2::{Spacing, Span, TokenStream, TokenTree};
 use quote::ToTokens;
-use std::borrow::Cow;
 use std::collections::BTreeSet;
 use std::iter::FromIterator;
 use syn::meta::ParseNestedMeta;
 use syn::parse::ParseStream;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
-use syn::{parse_quote, token, Ident, Lifetime, Token};
+use syn::{token, Ident, Lifetime, Token};
 
 // This module handles parsing of `#[serde(...)]` attributes. The entrypoints
 // are `attr::Container::from_ast`, `attr::Variant::from_ast`, and
@@ -609,11 +608,6 @@ impl Container {
         self.serde_path.as_ref()
     }
 
-    pub fn serde_path(&self) -> Cow<syn::Path> {
-        self.custom_serde_path()
-            .map_or_else(|| Cow::Owned(parse_quote!(_serde)), Cow::Borrowed)
-    }
-
     /// Error message generated when type can't be deserialized.
     /// If `None`, default message will be used
     pub fn expecting(&self) -> Option<&str> {
@@ -1024,6 +1018,7 @@ impl Field {
         field: &syn::Field,
         attrs: Option<&Variant>,
         container_default: &Default,
+        private: &Ident,
     ) -> Self {
         let mut ser_name = Attr::none(cx, RENAME);
         let mut de_name = Attr::none(cx, RENAME);
@@ -1217,7 +1212,7 @@ impl Field {
                 };
                 let span = Span::call_site();
                 path.segments.push(Ident::new("_serde", span).into());
-                path.segments.push(Ident::new("__private", span).into());
+                path.segments.push(private.clone().into());
                 path.segments.push(Ident::new("de", span).into());
                 path.segments
                     .push(Ident::new("borrow_cow_str", span).into());
@@ -1234,7 +1229,7 @@ impl Field {
                 };
                 let span = Span::call_site();
                 path.segments.push(Ident::new("_serde", span).into());
-                path.segments.push(Ident::new("__private", span).into());
+                path.segments.push(private.clone().into());
                 path.segments.push(Ident::new("de", span).into());
                 path.segments
                     .push(Ident::new("borrow_cow_bytes", span).into());

serde_derive/src/lib.rs

@@ -13,7 +13,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.222")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.226")]
 #![cfg_attr(not(check_cfg), allow(unexpected_cfgs))]
 // Ignored clippy lints
 #![allow(
@@ -75,6 +75,8 @@ extern crate proc_macro;
 mod internals;
 
 use proc_macro::TokenStream;
+use proc_macro2::{Ident, Span};
+use quote::{ToTokens, TokenStreamExt as _};
 use syn::parse_macro_input;
 use syn::DeriveInput;
 
@@ -84,11 +86,30 @@ mod bound;
 mod fragment;
 
 mod de;
+mod deprecated;
 mod dummy;
 mod pretend;
 mod ser;
 mod this;
 
+#[allow(non_camel_case_types)]
+struct private;
+
+impl private {
+    fn ident(&self) -> Ident {
+        Ident::new(
+            concat!("__private", env!("CARGO_PKG_VERSION_PATCH")),
+            Span::call_site(),
+        )
+    }
+}
+
+impl ToTokens for private {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        tokens.append(self.ident());
+    }
+}
+
 #[proc_macro_derive(Serialize, attributes(serde))]
 pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);

serde_derive/src/pretend.rs

@@ -1,4 +1,5 @@
 use crate::internals::ast::{Container, Data, Field, Style, Variant};
+use crate::private;
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
 
@@ -83,8 +84,8 @@ fn pretend_fields_used_struct(cont: &Container, fields: &[Field]) -> TokenStream
     let placeholders = (0usize..).map(|i| format_ident!("__v{}", i));
 
     quote! {
-        match _serde::__private::None::<&#type_ident #ty_generics> {
-            _serde::__private::Some(#type_ident { #(#members: #placeholders),* }) => {}
+        match _serde::#private::None::<&#type_ident #ty_generics> {
+            _serde::#private::Some(#type_ident { #(#members: #placeholders),* }) => {}
             _ => {}
         }
     }
@@ -96,11 +97,12 @@ fn pretend_fields_used_struct_packed(cont: &Container, fields: &[Field]) -> Toke
 
     let members = fields.iter().map(|field| &field.member).collect::<Vec<_>>();
 
+    let private2 = private;
     quote! {
-        match _serde::__private::None::<&#type_ident #ty_generics> {
-            _serde::__private::Some(__v @ #type_ident { #(#members: _),* }) => {
+        match _serde::#private::None::<&#type_ident #ty_generics> {
+            _serde::#private::Some(__v @ #type_ident { #(#members: _),* }) => {
                 #(
-                    let _ = _serde::__private::ptr::addr_of!(__v.#members);
+                    let _ = _serde::#private2::ptr::addr_of!(__v.#members);
                 )*
             }
             _ => {}
@@ -125,10 +127,11 @@ fn pretend_fields_used_enum(cont: &Container, variants: &[Variant]) -> TokenStre
         })
         .collect::<Vec<_>>();
 
+    let private2 = private;
     quote! {
-        match _serde::__private::None::<&#type_ident #ty_generics> {
+        match _serde::#private::None::<&#type_ident #ty_generics> {
             #(
-                _serde::__private::Some(#patterns) => {}
+                _serde::#private2::Some(#patterns) => {}
             )*
             _ => {}
         }
@@ -172,8 +175,8 @@ fn pretend_variants_used(cont: &Container) -> TokenStream {
         };
 
         quote! {
-            match _serde::__private::None {
-                _serde::__private::Some((#(#placeholders,)*)) => {
+            match _serde::#private::None {
+                _serde::#private::Some((#(#placeholders,)*)) => {
                     let _ = #type_ident::#variant_ident #turbofish #pat;
                 }
                 _ => {}

serde_derive/src/ser.rs

@@ -1,8 +1,9 @@
+use crate::deprecated::allow_deprecated;
 use crate::fragment::{Fragment, Match, Stmts};
 use crate::internals::ast::{Container, Data, Field, Style, Variant};
 use crate::internals::name::Name;
 use crate::internals::{attr, replace_receiver, Ctxt, Derive};
-use crate::{bound, dummy, pretend, this};
+use crate::{bound, dummy, pretend, private, this};
 use proc_macro2::{Span, TokenStream};
 use quote::{quote, quote_spanned};
 use syn::spanned::Spanned;
@@ -12,7 +13,7 @@ pub fn expand_derive_serialize(input: &mut syn::DeriveInput) -> syn::Result<Toke
     replace_receiver(input);
 
     let ctxt = Ctxt::new();
-    let cont = match Container::from_ast(&ctxt, input, Derive::Serialize) {
+    let cont = match Container::from_ast(&ctxt, input, Derive::Serialize, &private.ident()) {
         Some(cont) => cont,
         None => return Err(ctxt.check().unwrap_err()),
     };
@@ -23,17 +24,18 @@ pub fn expand_derive_serialize(input: &mut syn::DeriveInput) -> syn::Result<Toke
     let params = Parameters::new(&cont);
     let (impl_generics, ty_generics, where_clause) = params.generics.split_for_impl();
     let body = Stmts(serialize_body(&cont, &params));
-    let serde = cont.attrs.serde_path();
+    let allow_deprecated = allow_deprecated(input);
 
     let impl_block = if let Some(remote) = cont.attrs.remote() {
         let vis = &input.vis;
         let used = pretend::pretend_used(&cont, params.is_packed);
         quote! {
             #[automatically_derived]
+            #allow_deprecated
             impl #impl_generics #ident #ty_generics #where_clause {
-                #vis fn serialize<__S>(__self: &#remote #ty_generics, __serializer: __S) -> #serde::__private::Result<__S::Ok, __S::Error>
+                #vis fn serialize<__S>(__self: &#remote #ty_generics, __serializer: __S) -> _serde::#private::Result<__S::Ok, __S::Error>
                 where
-                    __S: #serde::Serializer,
+                    __S: _serde::Serializer,
                 {
                     #used
                     #body
@@ -43,10 +45,11 @@ pub fn expand_derive_serialize(input: &mut syn::DeriveInput) -> syn::Result<Toke
     } else {
         quote! {
             #[automatically_derived]
-            impl #impl_generics #serde::Serialize for #ident #ty_generics #where_clause {
-                fn serialize<__S>(&self, __serializer: __S) -> #serde::__private::Result<__S::Ok, __S::Error>
+            #allow_deprecated
+            impl #impl_generics _serde::Serialize for #ident #ty_generics #where_clause {
+                fn serialize<__S>(&self, __serializer: __S) -> _serde::#private::Result<__S::Ok, __S::Error>
                 where
-                    __S: #serde::Serializer,
+                    __S: _serde::Serializer,
                 {
                     #body
                 }
@@ -212,7 +215,7 @@ fn serialize_into(params: &Parameters, type_into: &syn::Type) -> Fragment {
     let self_var = &params.self_var;
     quote_block! {
         _serde::Serialize::serialize(
-            &_serde::__private::Into::<#type_into>::into(_serde::__private::Clone::clone(#self_var)),
+            &_serde::#private::Into::<#type_into>::into(_serde::#private::Clone::clone(#self_var)),
             __serializer)
     }
 }
@@ -382,7 +385,7 @@ fn serialize_struct_as_map(
     let let_mut = mut_if(serialized_fields.peek().is_some() || tag_field_exists);
 
     quote_block! {
-        let #let_mut __serde_state = _serde::Serializer::serialize_map(__serializer, _serde::__private::None)?;
+        let #let_mut __serde_state = _serde::Serializer::serialize_map(__serializer, _serde::#private::None)?;
         #tag_field
         #(#serialize_fields)*
         _serde::ser::SerializeMap::end(__serde_state)
@@ -404,7 +407,7 @@ fn serialize_enum(params: &Parameters, variants: &[Variant], cattrs: &attr::Cont
 
     if cattrs.remote().is_some() && cattrs.non_exhaustive() {
         arms.push(quote! {
-            ref unrecognized => _serde::__private::Err(_serde::ser::Error::custom(_serde::__private::ser::CannotSerializeVariant(unrecognized))),
+            ref unrecognized => _serde::#private::Err(_serde::ser::Error::custom(_serde::#private::ser::CannotSerializeVariant(unrecognized))),
         });
     }
 
@@ -431,7 +434,7 @@ fn serialize_variant(
             variant_ident
         );
         let skipped_err = quote! {
-            _serde::__private::Err(_serde::ser::Error::custom(#skipped_msg))
+            _serde::#private::Err(_serde::ser::Error::custom(#skipped_msg))
         };
         let fields_pat = match variant.style {
             Style::Unit => quote!(),
@@ -585,7 +588,7 @@ fn serialize_internally_tagged_variant(
     if let Some(path) = variant.attrs.serialize_with() {
         let ser = wrap_serialize_variant_with(params, path, variant);
         return quote_expr! {
-            _serde::__private::ser::serialize_tagged_newtype(
+            _serde::#private::ser::serialize_tagged_newtype(
                 __serializer,
                 #enum_ident_str,
                 #variant_ident_str,
@@ -614,7 +617,7 @@ fn serialize_internally_tagged_variant(
             }
 
             let span = field.original.span();
-            let func = quote_spanned!(span=> _serde::__private::ser::serialize_tagged_newtype);
+            let func = quote_spanned!(span=> _serde::#private::ser::serialize_tagged_newtype);
             quote_expr! {
                 #func(
                     __serializer,
@@ -648,7 +651,7 @@ fn serialize_adjacently_tagged_variant(
     let type_name = cattrs.name().serialize_name();
     let variant_name = variant.attrs.name().serialize_name();
     let serialize_variant = quote! {
-        &_serde::__private::ser::AdjacentlyTaggedEnumVariant {
+        &_serde::#private::ser::AdjacentlyTaggedEnumVariant {
             enum_name: #type_name,
             variant_index: #variant_index,
             variant_name: #variant_name,
@@ -731,12 +734,12 @@ fn serialize_adjacently_tagged_variant(
         #[doc(hidden)]
         struct __AdjacentlyTagged #wrapper_generics #where_clause {
             data: (#(&'__a #fields_ty,)*),
-            phantom: _serde::__private::PhantomData<#this_type #ty_generics>,
+            phantom: _serde::#private::PhantomData<#this_type #ty_generics>,
         }
 
         #[automatically_derived]
         impl #wrapper_impl_generics _serde::Serialize for __AdjacentlyTagged #wrapper_ty_generics #where_clause {
-            fn serialize<__S>(&self, __serializer: __S) -> _serde::__private::Result<__S::Ok, __S::Error>
+            fn serialize<__S>(&self, __serializer: __S) -> _serde::#private::Result<__S::Ok, __S::Error>
             where
                 __S: _serde::Serializer,
             {
@@ -754,7 +757,7 @@ fn serialize_adjacently_tagged_variant(
         _serde::ser::SerializeStruct::serialize_field(
             &mut __struct, #content, &__AdjacentlyTagged {
                 data: (#(#fields_ident,)*),
-                phantom: _serde::__private::PhantomData::<#this_type #ty_generics>,
+                phantom: _serde::#private::PhantomData::<#this_type #ty_generics>,
             })?;
         _serde::ser::SerializeStruct::end(__struct)
     }
@@ -996,19 +999,19 @@ fn serialize_struct_variant_with_flatten(
                 #[doc(hidden)]
                 struct __EnumFlatten #wrapper_generics #where_clause {
                     data: (#(&'__a #fields_ty,)*),
-                    phantom: _serde::__private::PhantomData<#this_type #ty_generics>,
+                    phantom: _serde::#private::PhantomData<#this_type #ty_generics>,
                 }
 
                 #[automatically_derived]
                 impl #wrapper_impl_generics _serde::Serialize for __EnumFlatten #wrapper_ty_generics #where_clause {
-                    fn serialize<__S>(&self, __serializer: __S) -> _serde::__private::Result<__S::Ok, __S::Error>
+                    fn serialize<__S>(&self, __serializer: __S) -> _serde::#private::Result<__S::Ok, __S::Error>
                     where
                         __S: _serde::Serializer,
                     {
                         let (#(#members,)*) = self.data;
                         let #let_mut __serde_state = _serde::Serializer::serialize_map(
                             __serializer,
-                            _serde::__private::None)?;
+                            _serde::#private::None)?;
                         #(#serialize_fields)*
                         _serde::ser::SerializeMap::end(__serde_state)
                     }
@@ -1021,7 +1024,7 @@ fn serialize_struct_variant_with_flatten(
                     #variant_name,
                     &__EnumFlatten {
                         data: (#(#members,)*),
-                        phantom: _serde::__private::PhantomData::<#this_type #ty_generics>,
+                        phantom: _serde::#private::PhantomData::<#this_type #ty_generics>,
                     })
             }
         }
@@ -1029,7 +1032,7 @@ fn serialize_struct_variant_with_flatten(
             quote_block! {
                 let #let_mut __serde_state = _serde::Serializer::serialize_map(
                     __serializer,
-                    _serde::__private::None)?;
+                    _serde::#private::None)?;
                 _serde::ser::SerializeMap::serialize_entry(
                     &mut __serde_state,
                     #tag,
@@ -1043,7 +1046,7 @@ fn serialize_struct_variant_with_flatten(
             quote_block! {
                 let #let_mut __serde_state = _serde::Serializer::serialize_map(
                     __serializer,
-                    _serde::__private::None)?;
+                    _serde::#private::None)?;
                 #(#serialize_fields)*
                 _serde::ser::SerializeMap::end(__serde_state)
             }
@@ -1132,7 +1135,7 @@ fn serialize_struct_visitor(
             let ser = if field.attrs.flatten() {
                 let func = quote_spanned!(span=> _serde::Serialize::serialize);
                 quote! {
-                    #func(&#field_expr, _serde::__private::ser::FlatMapSerializer(&mut __serde_state))?;
+                    #func(&#field_expr, _serde::#private::ser::FlatMapSerializer(&mut __serde_state))?;
                 }
             } else {
                 let func = struct_trait.serialize_field(span);
@@ -1239,12 +1242,12 @@ fn wrap_serialize_with(
         #[doc(hidden)]
         struct __SerializeWith #wrapper_impl_generics #where_clause {
             values: (#(&'__a #field_tys, )*),
-            phantom: _serde::__private::PhantomData<#this_type #ty_generics>,
+            phantom: _serde::#private::PhantomData<#this_type #ty_generics>,
         }
 
         #[automatically_derived]
         impl #wrapper_impl_generics _serde::Serialize for __SerializeWith #wrapper_ty_generics #where_clause {
-            fn serialize<__S>(&#self_var, #serializer_var: __S) -> _serde::__private::Result<__S::Ok, __S::Error>
+            fn serialize<__S>(&#self_var, #serializer_var: __S) -> _serde::#private::Result<__S::Ok, __S::Error>
             where
                 __S: _serde::Serializer,
             {
@@ -1254,7 +1257,7 @@ fn wrap_serialize_with(
 
         __SerializeWith {
             values: (#(#field_exprs, )*),
-            phantom: _serde::__private::PhantomData::<#this_type #ty_generics>,
+            phantom: _serde::#private::PhantomData::<#this_type #ty_generics>,
         }
     })
 }
@@ -1290,11 +1293,11 @@ fn get_member(params: &Parameters, field: &Field, member: &Member) -> TokenStrea
                 quote!(&#self_var.#member)
             };
             let ty = field.ty;
-            quote!(_serde::__private::ser::constrain::<#ty>(#inner))
+            quote!(_serde::#private::ser::constrain::<#ty>(#inner))
         }
         (true, Some(getter)) => {
             let ty = field.ty;
-            quote!(_serde::__private::ser::constrain::<#ty>(&#getter(#self_var)))
+            quote!(_serde::#private::ser::constrain::<#ty>(&#getter(#self_var)))
         }
         (false, Some(_)) => {
             unreachable!("getter is only allowed for remote impls");

serde_derive_internals/Cargo.toml

@@ -24,6 +24,7 @@ syn = { workspace = true, features = ["clone-impls", "derive", "parsing", "print
 targets = ["x86_64-unknown-linux-gnu"]
 rustdoc-args = [
     "--generate-link-to-definition",
+    "--generate-macro-expansion",
     "--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",

test_suite/tests/test_annotations.rs

@@ -2697,23 +2697,42 @@ mod flatten {
 
             #[test]
             fn newtype() {
+                let value = Flatten {
+                    data: Enum::Newtype(HashMap::from_iter([("key".into(), "value".into())])),
+                    extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
+                };
                 assert_tokens(
-                    &Flatten {
-                        data: Enum::Newtype(HashMap::from_iter([("key".into(), "value".into())])),
-                        extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
-                    },
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // data
                         Token::Str("Newtype"), // variant
                         Token::Map { len: Some(1) },
                         Token::Str("key"),
                         Token::Str("value"),
                         Token::MapEnd,
+                        // extra
                         Token::Str("extra_key"),
                         Token::Str("extra value"),
                         Token::MapEnd,
                     ],
                 );
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // extra
+                        Token::Str("extra_key"),
+                        Token::Str("extra value"),
+                        // data
+                        Token::Str("Newtype"), // variant
+                        Token::Map { len: Some(1) },
+                        Token::Str("key"),
+                        Token::Str("value"),
+                        Token::MapEnd,
+                        Token::MapEnd,
+                    ],
+                );
             }
 
             // Reaches crate::private::de::content::VariantDeserializer::tuple_variant
@@ -2721,23 +2740,42 @@ mod flatten {
             // via FlatMapDeserializer::deserialize_enum
             #[test]
             fn tuple() {
+                let value = Flatten {
+                    data: Enum::Tuple(0, 42),
+                    extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
+                };
                 assert_tokens(
-                    &Flatten {
-                        data: Enum::Tuple(0, 42),
-                        extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
-                    },
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // data
                         Token::Str("Tuple"), // variant
                         Token::Seq { len: Some(2) },
                         Token::U32(0),
                         Token::U32(42),
                         Token::SeqEnd,
+                        // extra
                         Token::Str("extra_key"),
                         Token::Str("extra value"),
                         Token::MapEnd,
                     ],
                 );
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // extra
+                        Token::Str("extra_key"),
+                        Token::Str("extra value"),
+                        // data
+                        Token::Str("Tuple"), // variant
+                        Token::Seq { len: Some(2) },
+                        Token::U32(0),
+                        Token::U32(42),
+                        Token::SeqEnd,
+                        Token::MapEnd,
+                    ],
+                );
             }
 
             // Reaches crate::private::de::content::VariantDeserializer::struct_variant
@@ -2745,26 +2783,45 @@ mod flatten {
             // via FlatMapDeserializer::deserialize_enum
             #[test]
             fn struct_from_seq() {
-                assert_de_tokens(
-                    &Flatten {
-                        data: Enum::Struct {
-                            index: 0,
-                            value: 42,
-                        },
-                        extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
+                let value = Flatten {
+                    data: Enum::Struct {
+                        index: 0,
+                        value: 42,
                     },
+                    extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
+                };
+                assert_de_tokens(
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // data
                         Token::Str("Struct"), // variant
                         Token::Seq { len: Some(2) },
                         Token::U32(0),  // index
                         Token::U32(42), // value
                         Token::SeqEnd,
+                        // extra
                         Token::Str("extra_key"),
                         Token::Str("extra value"),
                         Token::MapEnd,
                     ],
                 );
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // extra
+                        Token::Str("extra_key"),
+                        Token::Str("extra value"),
+                        // data
+                        Token::Str("Struct"), // variant
+                        Token::Seq { len: Some(2) },
+                        Token::U32(0),  // index
+                        Token::U32(42), // value
+                        Token::SeqEnd,
+                        Token::MapEnd,
+                    ],
+                );
             }
 
             // Reaches crate::private::de::content::VariantDeserializer::struct_variant
@@ -2772,16 +2829,18 @@ mod flatten {
             // via FlatMapDeserializer::deserialize_enum
             #[test]
             fn struct_from_map() {
-                assert_tokens(
-                    &Flatten {
-                        data: Enum::Struct {
-                            index: 0,
-                            value: 42,
-                        },
-                        extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
+                let value = Flatten {
+                    data: Enum::Struct {
+                        index: 0,
+                        value: 42,
                     },
+                    extra: HashMap::from_iter([("extra_key".into(), "extra value".into())]),
+                };
+                assert_tokens(
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // data
                         Token::Str("Struct"), // variant
                         Token::Struct {
                             len: 2,
@@ -2792,11 +2851,33 @@ mod flatten {
                         Token::Str("value"),
                         Token::U32(42),
                         Token::StructEnd,
+                        // extra
                         Token::Str("extra_key"),
                         Token::Str("extra value"),
                         Token::MapEnd,
                     ],
                 );
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // extra
+                        Token::Str("extra_key"),
+                        Token::Str("extra value"),
+                        // data
+                        Token::Str("Struct"), // variant
+                        Token::Struct {
+                            len: 2,
+                            name: "Struct",
+                        },
+                        Token::Str("index"),
+                        Token::U32(0),
+                        Token::Str("value"),
+                        Token::U32(42),
+                        Token::StructEnd,
+                        Token::MapEnd,
+                    ],
+                );
             }
         }
 
@@ -2817,6 +2898,7 @@ mod flatten {
             #[derive(Debug, PartialEq, Serialize, Deserialize)]
             #[serde(tag = "tag", content = "content")]
             enum Enum {
+                Unit,
                 Newtype(NewtypeVariant),
                 Struct { index: u32, value: u32 },
             }
@@ -2827,24 +2909,357 @@ mod flatten {
             }
 
             #[test]
-            fn struct_() {
+            fn unit() {
+                let value = Flatten {
+                    outer: 42,
+                    data: NewtypeWrapper(Enum::Unit),
+                };
+                // Field order: outer, [tag]
                 assert_tokens(
-                    &Flatten {
-                        outer: 42,
-                        data: NewtypeWrapper(Enum::Struct {
-                            index: 0,
-                            value: 42,
-                        }),
-                    },
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // outer
                         Token::Str("outer"),
                         Token::U32(42),
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        // content missing
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [tag], outer
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        // content missing
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: outer, [tag, content]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        // content
+                        Token::Str("content"),
+                        Token::Unit,
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: outer, [content, tag]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // content
+                        Token::Str("content"),
+                        Token::Unit,
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [tag, content], outer
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        // content
+                        Token::Str("content"),
+                        Token::Unit,
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [content, tag], outer
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // content
+                        Token::Str("content"),
+                        Token::Unit,
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [tag], outer, [content]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // content
+                        Token::Str("content"),
+                        Token::Unit,
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [content], outer, [tag]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // content
+                        Token::Str("content"),
+                        Token::Unit,
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Unit",
+                        },
+                        Token::MapEnd,
+                    ],
+                );
+            }
+
+            #[test]
+            fn newtype() {
+                let value = Flatten {
+                    outer: 42,
+                    data: NewtypeWrapper(Enum::Newtype(NewtypeVariant { value: 23 })),
+                };
+                // Field order: outer, [tag, content]
+                assert_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Newtype",
+                        },
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 1,
+                            name: "NewtypeVariant",
+                        },
+                        Token::Str("value"),
+                        Token::U32(23),
+                        Token::StructEnd,
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: outer, [content, tag]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 1,
+                            name: "NewtypeVariant",
+                        },
+                        Token::Str("value"),
+                        Token::U32(23),
+                        Token::StructEnd,
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Newtype",
+                        },
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [tag, content], outer
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Newtype",
+                        },
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 1,
+                            name: "NewtypeVariant",
+                        },
+                        Token::Str("value"),
+                        Token::U32(23),
+                        Token::StructEnd,
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [content, tag], outer
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 1,
+                            name: "NewtypeVariant",
+                        },
+                        Token::Str("value"),
+                        Token::U32(23),
+                        Token::StructEnd,
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Newtype",
+                        },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [tag], outer, [content]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Newtype",
+                        },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 1,
+                            name: "NewtypeVariant",
+                        },
+                        Token::Str("value"),
+                        Token::U32(23),
+                        Token::StructEnd,
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [content], outer, [tag]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 1,
+                            name: "NewtypeVariant",
+                        },
+                        Token::Str("value"),
+                        Token::U32(23),
+                        Token::StructEnd,
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Newtype",
+                        },
+                        Token::MapEnd,
+                    ],
+                );
+            }
+
+            #[test]
+            fn struct_() {
+                let value = Flatten {
+                    outer: 42,
+                    data: NewtypeWrapper(Enum::Struct {
+                        index: 0,
+                        value: 42,
+                    }),
+                };
+                // Field order: outer, [tag, content]
+                assert_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // tag
                         Token::Str("tag"),
                         Token::UnitVariant {
                             name: "Enum",
                             variant: "Struct",
                         },
+                        // content
                         Token::Str("content"),
                         Token::Struct {
                             len: 2,
@@ -2858,32 +3273,143 @@ mod flatten {
                         Token::MapEnd,
                     ],
                 );
-            }
-
-            #[test]
-            fn newtype() {
-                assert_tokens(
-                    &Flatten {
-                        outer: 42,
-                        data: NewtypeWrapper(Enum::Newtype(NewtypeVariant { value: 23 })),
-                    },
+                // Field order: outer, [content, tag]
+                assert_de_tokens(
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // outer
                         Token::Str("outer"),
                         Token::U32(42),
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 2,
+                            name: "Struct",
+                        },
+                        Token::Str("index"),
+                        Token::U32(0),
+                        Token::Str("value"),
+                        Token::U32(42),
+                        Token::StructEnd,
+                        // tag
                         Token::Str("tag"),
                         Token::UnitVariant {
                             name: "Enum",
-                            variant: "Newtype",
+                            variant: "Struct",
                         },
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [tag, content], outer
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Struct",
+                        },
+                        // content
                         Token::Str("content"),
                         Token::Struct {
-                            len: 1,
-                            name: "NewtypeVariant",
+                            len: 2,
+                            name: "Struct",
                         },
+                        Token::Str("index"),
+                        Token::U32(0),
                         Token::Str("value"),
-                        Token::U32(23),
+                        Token::U32(42),
                         Token::StructEnd,
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [content, tag], outer
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 2,
+                            name: "Struct",
+                        },
+                        Token::Str("index"),
+                        Token::U32(0),
+                        Token::Str("value"),
+                        Token::U32(42),
+                        Token::StructEnd,
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Struct",
+                        },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [tag], outer, [content]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Struct",
+                        },
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 2,
+                            name: "Struct",
+                        },
+                        Token::Str("index"),
+                        Token::U32(0),
+                        Token::Str("value"),
+                        Token::U32(42),
+                        Token::StructEnd,
+                        Token::MapEnd,
+                    ],
+                );
+                // Field order: [content], outer, [tag]
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // content
+                        Token::Str("content"),
+                        Token::Struct {
+                            len: 2,
+                            name: "Struct",
+                        },
+                        Token::Str("index"),
+                        Token::U32(0),
+                        Token::Str("value"),
+                        Token::U32(42),
+                        Token::StructEnd,
+                        // outer
+                        Token::Str("outer"),
+                        Token::U32(42),
+                        // tag
+                        Token::Str("tag"),
+                        Token::UnitVariant {
+                            name: "Enum",
+                            variant: "Struct",
+                        },
                         Token::MapEnd,
                     ],
                 );
@@ -2917,17 +3443,20 @@ mod flatten {
                     D { d: i32 },
                 }
 
+                let value = Flatten {
+                    x: X::B { b: 1 },
+                    y: Y::D { d: 2 },
+                };
                 assert_tokens(
-                    &Flatten {
-                        x: X::B { b: 1 },
-                        y: Y::D { d: 2 },
-                    },
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // x
                         Token::Str("typeX"),
                         Token::Str("B"),
                         Token::Str("b"),
                         Token::I32(1),
+                        // y
                         Token::Str("typeY"),
                         Token::Str("D"),
                         Token::Str("d"),
@@ -2935,11 +3464,28 @@ mod flatten {
                         Token::MapEnd,
                     ],
                 );
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // y
+                        Token::Str("typeY"),
+                        Token::Str("D"),
+                        Token::Str("d"),
+                        Token::I32(2),
+                        // x
+                        Token::Str("typeX"),
+                        Token::Str("B"),
+                        Token::Str("b"),
+                        Token::I32(1),
+                        Token::MapEnd,
+                    ],
+                );
             }
 
             #[test]
             fn unit_enum_with_unknown_fields() {
-                #[derive(Debug, PartialEq, Deserialize)]
+                #[derive(Debug, PartialEq, Serialize, Deserialize)]
                 struct Flatten {
                     #[serde(flatten)]
                     x: X,
@@ -2947,31 +3493,49 @@ mod flatten {
                     y: Y,
                 }
 
-                #[derive(Debug, PartialEq, Deserialize)]
+                #[derive(Debug, PartialEq, Serialize, Deserialize)]
                 #[serde(tag = "typeX")]
                 enum X {
                     A,
                 }
 
-                #[derive(Debug, PartialEq, Deserialize)]
+                #[derive(Debug, PartialEq, Serialize, Deserialize)]
                 #[serde(tag = "typeY")]
                 enum Y {
                     B { c: u32 },
                 }
 
-                assert_de_tokens(
-                    &Flatten {
-                        x: X::A,
-                        y: Y::B { c: 0 },
-                    },
+                let value = Flatten {
+                    x: X::A,
+                    y: Y::B { c: 0 },
+                };
+                assert_tokens(
+                    &value,
                     &[
                         Token::Map { len: None },
+                        // x
                         Token::Str("typeX"),
                         Token::Str("A"),
+                        // y
                         Token::Str("typeY"),
                         Token::Str("B"),
                         Token::Str("c"),
-                        Token::I32(0),
+                        Token::U32(0),
+                        Token::MapEnd,
+                    ],
+                );
+                assert_de_tokens(
+                    &value,
+                    &[
+                        Token::Map { len: None },
+                        // y
+                        Token::Str("typeY"),
+                        Token::Str("B"),
+                        Token::Str("c"),
+                        Token::U32(0),
+                        // x
+                        Token::Str("typeX"),
+                        Token::Str("A"),
                         Token::MapEnd,
                     ],
                 );

test_suite/tests/test_deprecated.rs

@@ -0,0 +1,30 @@
+#![deny(deprecated)]
+#![allow(dead_code)]
+
+use serde_derive::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize)]
+#[deprecated]
+enum DeprecatedEnum {
+    A,
+    B,
+}
+
+#[derive(Serialize, Deserialize)]
+#[deprecated]
+struct DeprecatedStruct {
+    a: bool,
+}
+
+#[derive(Serialize, Deserialize)]
+enum DeprecatedVariant {
+    A,
+    #[deprecated]
+    B,
+}
+
+#[derive(Serialize, Deserialize)]
+struct DeprecatedField {
+    #[deprecated]
+    a: bool,
+}

test_suite/tests/ui/deprecated/deprecated_de_with.rs

@@ -0,0 +1,20 @@
+#![deny(deprecated)]
+
+use serde::Deserializer;
+use serde_derive::Deserialize;
+
+#[derive(Deserialize)]
+pub struct Struct {
+    #[serde(deserialize_with = "deprecated_with")]
+    pub field: i32,
+}
+
+#[deprecated]
+fn deprecated_with<'de, D>(_deserializer: D) -> Result<i32, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    unimplemented!()
+}
+
+fn main() {}

test_suite/tests/ui/deprecated/deprecated_de_with.stderr

@@ -0,0 +1,11 @@
+error: use of deprecated function `deprecated_with`
+ --> tests/ui/deprecated/deprecated_de_with.rs:8:32
+  |
+8 |     #[serde(deserialize_with = "deprecated_with")]
+  |                                ^^^^^^^^^^^^^^^^^
+  |
+note: the lint level is defined here
+ --> tests/ui/deprecated/deprecated_de_with.rs:1:9
+  |
+1 | #![deny(deprecated)]
+  |         ^^^^^^^^^^

test_suite/tests/ui/deprecated/deprecated_ser_with.rs

@@ -0,0 +1,20 @@
+#![deny(deprecated)]
+
+use serde::Serializer;
+use serde_derive::Serialize;
+
+#[derive(Serialize)]
+pub struct Struct {
+    #[serde(serialize_with = "deprecated_with")]
+    pub field: i32,
+}
+
+#[deprecated]
+fn deprecated_with<S>(_field: &i32, _serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    unimplemented!()
+}
+
+fn main() {}

test_suite/tests/ui/deprecated/deprecated_ser_with.stderr

@@ -0,0 +1,11 @@
+error: use of deprecated function `deprecated_with`
+ --> tests/ui/deprecated/deprecated_ser_with.rs:8:30
+  |
+8 |     #[serde(serialize_with = "deprecated_with")]
+  |                              ^^^^^^^^^^^^^^^^^
+  |
+note: the lint level is defined here
+ --> tests/ui/deprecated/deprecated_ser_with.rs:1:9
+  |
+1 | #![deny(deprecated)]
+  |         ^^^^^^^^^^

test_suite/tests/ui/with/incorrect_type.stderr

@@ -6,10 +6,7 @@ error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
 15 | struct W(#[serde(with = "w")] u8, u8);
    |                         --- required by a bound introduced by this call
    |
-   = help: the following other types implement trait `Serializer`:
-             &mut Formatter<'a>
-             FlatMapSerializer<'a, M>
-             _::_serde::__private::ser::content::ContentSerializer<E>
+   = help: the trait `Serializer` is implemented for `&mut Formatter<'a>`
 note: required by a bound in `w::serialize`
   --> tests/ui/with/incorrect_type.rs:9:28
    |
@@ -36,10 +33,7 @@ error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
 15 | struct W(#[serde(with = "w")] u8, u8);
    |                         ^^^ the trait `Serializer` is not implemented for `&u8`
    |
-   = help: the following other types implement trait `Serializer`:
-             &mut Formatter<'a>
-             FlatMapSerializer<'a, M>
-             _::_serde::__private::ser::content::ContentSerializer<E>
+   = help: the trait `Serializer` is implemented for `&mut Formatter<'a>`
 
 error[E0308]: `?` operator has incompatible types
   --> tests/ui/with/incorrect_type.rs:15:25
@@ -57,10 +51,7 @@ error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
 18 | struct S(#[serde(serialize_with = "w::serialize")] u8, u8);
    |                                   -------------- required by a bound introduced by this call
    |
-   = help: the following other types implement trait `Serializer`:
-             &mut Formatter<'a>
-             FlatMapSerializer<'a, M>
-             _::_serde::__private::ser::content::ContentSerializer<E>
+   = help: the trait `Serializer` is implemented for `&mut Formatter<'a>`
 note: required by a bound in `w::serialize`
   --> tests/ui/with/incorrect_type.rs:9:28
    |
@@ -87,10 +78,7 @@ error[E0277]: the trait bound `&u8: serde::Serializer` is not satisfied
 18 | struct S(#[serde(serialize_with = "w::serialize")] u8, u8);
    |                                   ^^^^^^^^^^^^^^ the trait `Serializer` is not implemented for `&u8`
    |
-   = help: the following other types implement trait `Serializer`:
-             &mut Formatter<'a>
-             FlatMapSerializer<'a, M>
-             _::_serde::__private::ser::content::ContentSerializer<E>
+   = help: the trait `Serializer` is implemented for `&mut Formatter<'a>`
 
 error[E0308]: `?` operator has incompatible types
   --> tests/ui/with/incorrect_type.rs:21:37