Release 1.0.166

error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
       --> test_suite/tests/test_de.rs:202:12
        |
    202 |     .chain(vec![Token::MapEnd].into_iter())
        |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `vec![Token::MapEnd]`
        |
    note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
       --> /home/david/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:522:12
        |
    522 |         U: IntoIterator<Item = Self::Item>,
        |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_conversion
        = note: `-D clippy::useless-conversion` implied by `-D clippy::all`

.github/workflows/ci.yml

@@ -3,6 +3,7 @@ name: CI
 on:
   push:
   pull_request:
+  workflow_dispatch:
   schedule: [cron: "40 1 * * *"]
 
 permissions:
@@ -149,6 +150,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - uses: dtolnay/rust-toolchain@miri
+      - run: cargo miri setup
       - run: cd serde && cargo miri test --features derive,rc,unstable
         env:
           MIRIFLAGS: -Zmiri-strict-provenance

serde/.clippy.toml

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

serde/Cargo.toml

@@ -1,9 +1,9 @@
 [package]
 name = "serde"
-version = "1.0.163" # remember to update html_root_url and serde_derive dependency
+version = "1.0.166" # remember to update html_root_url and serde_derive dependency
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
-categories = ["encoding", "no-std"]
+categories = ["encoding", "no-std", "no-std::no-alloc"]
 description = "A generic serialization/deserialization framework"
 documentation = "https://docs.rs/serde"
 homepage = "https://serde.rs"
@@ -15,7 +15,7 @@ repository = "https://github.com/serde-rs/serde"
 rust-version = "1.19"
 
 [dependencies]
-serde_derive = { version = "=1.0.163", optional = true, path = "../serde_derive" }
+serde_derive = { version = "=1.0.166", optional = true, path = "../serde_derive" }
 
 [dev-dependencies]
 serde_derive = { version = "1.0", path = "../serde_derive" }

serde/src/de/impls.rs

@@ -1587,7 +1587,7 @@ macro_rules! parse_socket_impl {
                 if deserializer.is_human_readable() {
                     deserializer.deserialize_str(FromStrVisitor::new($expecting))
                 } else {
-                    <(_, u16)>::deserialize(deserializer).map(|(ip, port)| $new(ip, port))
+                    <(_, u16)>::deserialize(deserializer).map($new)
                 }
             }
         }
@@ -1614,12 +1614,10 @@ impl<'de> Deserialize<'de> for net::SocketAddr {
 }
 
 #[cfg(feature = "std")]
-parse_socket_impl!("IPv4 socket address" net::SocketAddrV4, net::SocketAddrV4::new);
+parse_socket_impl!("IPv4 socket address" net::SocketAddrV4, |(ip, port)| net::SocketAddrV4::new(ip, port));
 
 #[cfg(feature = "std")]
-parse_socket_impl!("IPv6 socket address" net::SocketAddrV6, |ip, port| net::SocketAddrV6::new(
-    ip, port, 0, 0
-));
+parse_socket_impl!("IPv6 socket address" net::SocketAddrV6, |(ip, port)| net::SocketAddrV6::new(ip, port, 0, 0));
 
 ////////////////////////////////////////////////////////////////////////////////
 
@@ -2098,7 +2096,7 @@ impl<'de> Deserialize<'de> for Duration {
             }
         }
 
-        const FIELDS: &'static [&'static str] = &["secs", "nanos"];
+        const FIELDS: &[&str] = &["secs", "nanos"];
         deserializer.deserialize_struct("Duration", FIELDS, DurationVisitor)
     }
 }
@@ -2240,7 +2238,7 @@ impl<'de> Deserialize<'de> for SystemTime {
             }
         }
 
-        const FIELDS: &'static [&'static str] = &["secs_since_epoch", "nanos_since_epoch"];
+        const FIELDS: &[&str] = &["secs_since_epoch", "nanos_since_epoch"];
         let duration = try!(deserializer.deserialize_struct("SystemTime", FIELDS, DurationVisitor));
         #[cfg(not(no_systemtime_checked_add))]
         let ret = UNIX_EPOCH
@@ -2308,7 +2306,7 @@ mod range {
 
     use de::{Deserialize, Deserializer, Error, MapAccess, SeqAccess, Visitor};
 
-    pub const FIELDS: &'static [&'static str] = &["start", "end"];
+    pub const FIELDS: &[&str] = &["start", "end"];
 
     // If this were outside of the serde crate, it would just use:
     //
@@ -2534,7 +2532,7 @@ where
             }
         }
 
-        const VARIANTS: &'static [&'static str] = &["Unbounded", "Included", "Excluded"];
+        const VARIANTS: &[&str] = &["Unbounded", "Included", "Excluded"];
 
         deserializer.deserialize_enum("Bound", VARIANTS, BoundVisitor(PhantomData))
     }
@@ -2642,7 +2640,7 @@ where
             }
         }
 
-        const VARIANTS: &'static [&'static str] = &["Ok", "Err"];
+        const VARIANTS: &[&str] = &["Ok", "Err"];
 
         deserializer.deserialize_enum("Result", VARIANTS, ResultVisitor(PhantomData))
     }
@@ -2708,7 +2706,7 @@ struct FromStrVisitor<T> {
 impl<T> FromStrVisitor<T> {
     fn new(expecting: &'static str) -> Self {
         FromStrVisitor {
-            expecting: expecting,
+            expecting,
             ty: PhantomData,
         }
     }

serde/src/de/utf8.rs

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

serde/src/de/value.rs

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

serde/src/lib.rs

@@ -93,7 +93,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.163")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.166")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Unstable functionality only if the user asks for it. For tracking and

serde/src/private/de.rs

@@ -518,7 +518,7 @@ mod content {
     impl<'de> TagOrContentVisitor<'de> {
         fn new(name: &'static str) -> Self {
             TagOrContentVisitor {
-                name: name,
+                name,
                 value: PhantomData,
             }
         }
@@ -815,7 +815,7 @@ mod content {
         pub fn new(name: &'static str, expecting: &'static str) -> Self {
             TaggedContentVisitor {
                 tag_name: name,
-                expecting: expecting,
+                expecting,
                 value: PhantomData,
             }
         }
@@ -859,7 +859,7 @@ mod content {
             };
             let rest = de::value::SeqAccessDeserializer::new(seq);
             Ok(TaggedContent {
-                tag: tag,
+                tag,
                 content: try!(Content::deserialize(rest)),
             })
         }
@@ -887,7 +887,7 @@ mod content {
             match tag {
                 None => Err(de::Error::missing_field(self.tag_name)),
                 Some(tag) => Ok(TaggedContent {
-                    tag: tag,
+                    tag,
                     content: Content::Map(vec),
                 }),
             }
@@ -1464,7 +1464,7 @@ mod content {
         /// private API, don't use
         pub fn new(content: Content<'de>) -> Self {
             ContentDeserializer {
-                content: content,
+                content,
                 err: PhantomData,
             }
         }
@@ -1485,8 +1485,8 @@ mod content {
     {
         pub fn new(variant: Content<'de>, value: Option<Content<'de>>) -> EnumDeserializer<'de, E> {
             EnumDeserializer {
-                variant: variant,
-                value: value,
+                variant,
+                value,
                 err: PhantomData,
             }
         }
@@ -2142,8 +2142,8 @@ mod content {
             };
 
             visitor.visit_enum(EnumRefDeserializer {
-                variant: variant,
-                value: value,
+                variant,
+                value,
                 err: PhantomData,
             })
         }
@@ -2187,12 +2187,20 @@ mod content {
         /// private API, don't use
         pub fn new(content: &'a Content<'de>) -> Self {
             ContentRefDeserializer {
-                content: content,
+                content,
                 err: PhantomData,
             }
         }
     }
 
+    impl<'a, 'de: 'a, E> Copy for ContentRefDeserializer<'a, 'de, E> {}
+
+    impl<'a, 'de: 'a, E> Clone for ContentRefDeserializer<'a, 'de, E> {
+        fn clone(&self) -> Self {
+            *self
+        }
+    }
+
     struct EnumRefDeserializer<'a, 'de: 'a, E>
     where
         E: de::Error,
@@ -2488,8 +2496,8 @@ mod content {
         /// Not public API.
         pub fn new(type_name: &'a str, variant_name: &'a str) -> Self {
             InternallyTaggedUnitVisitor {
-                type_name: type_name,
-                variant_name: variant_name,
+                type_name,
+                variant_name,
             }
         }
     }
@@ -2533,8 +2541,8 @@ mod content {
         /// Not public API.
         pub fn new(type_name: &'a str, variant_name: &'a str) -> Self {
             UntaggedUnitVisitor {
-                type_name: type_name,
-                variant_name: variant_name,
+                type_name,
+                variant_name,
             }
         }
     }
@@ -2750,7 +2758,7 @@ where
     where
         V: Visitor<'de>,
     {
-        for entry in self.0.iter_mut() {
+        for entry in self.0 {
             if let Some((key, value)) = flat_map_take_entry(entry, variants) {
                 return visitor.visit_enum(EnumDeserializer::new(key, Some(value)));
             }
@@ -2785,7 +2793,7 @@ where
         visitor.visit_map(FlatStructAccess {
             iter: self.0.iter_mut(),
             pending_content: None,
-            fields: fields,
+            fields,
             _marker: PhantomData,
         })
     }

serde/src/private/ser.rs

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

serde/src/ser/impls.rs

@@ -713,7 +713,7 @@ impl Serialize for net::IpAddr {
 }
 
 #[cfg(feature = "std")]
-const DEC_DIGITS_LUT: &'static [u8] = b"\
+const DEC_DIGITS_LUT: &[u8] = b"\
       0001020304050607080910111213141516171819\
       2021222324252627282930313233343536373839\
       4041424344454647484950515253545556575859\

serde_derive/.clippy.toml

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

serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.163" # remember to update html_root_url
+version = "1.0.166" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 categories = ["no-std"]
 description = "Macros 1.1 implementation of #[derive(Serialize, Deserialize)]"
@@ -24,7 +24,7 @@ proc-macro = true
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = "2.0.3"
+syn = "2.0.21"
 
 [dev-dependencies]
 serde = { version = "1.0", path = "../serde" }

serde_derive/src/bound.rs

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

serde_derive/src/de.rs

@@ -15,9 +15,7 @@ use this;
 use std::collections::BTreeSet;
 use std::ptr;
 
-pub fn expand_derive_deserialize(
-    input: &mut syn::DeriveInput,
-) -> Result<TokenStream, Vec<syn::Error>> {
+pub fn expand_derive_deserialize(input: &mut syn::DeriveInput) -> syn::Result<TokenStream> {
     replace_receiver(input);
 
     let ctxt = Ctxt::new();
@@ -447,14 +445,19 @@ fn deserialize_tuple(
     cattrs: &attr::Container,
     deserializer: Option<TokenStream>,
 ) -> Fragment {
+    assert!(!cattrs.has_flatten());
+
+    let field_count = fields
+        .iter()
+        .filter(|field| !field.attrs.skip_deserializing())
+        .count();
+
     let this_type = &params.this_type;
     let this_value = &params.this_value;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
         split_with_de_lifetime(params);
     let delife = params.borrowed.de_lifetime();
 
-    assert!(!cattrs.has_flatten());
-
     // If there are getters (implying private fields), construct the local type
     // and use an `Into` conversion to get the remote type. If there are no
     // getters then construct the target type directly.
@@ -495,19 +498,18 @@ fn deserialize_tuple(
         }
     };
     let dispatch = if let Some(deserializer) = deserializer {
-        quote!(_serde::Deserializer::deserialize_tuple(#deserializer, #nfields, #visitor_expr))
+        quote!(_serde::Deserializer::deserialize_tuple(#deserializer, #field_count, #visitor_expr))
     } else if is_enum {
-        quote!(_serde::de::VariantAccess::tuple_variant(__variant, #nfields, #visitor_expr))
+        quote!(_serde::de::VariantAccess::tuple_variant(__variant, #field_count, #visitor_expr))
     } else if nfields == 1 {
         let type_name = cattrs.name().deserialize_name();
         quote!(_serde::Deserializer::deserialize_newtype_struct(__deserializer, #type_name, #visitor_expr))
     } else {
         let type_name = cattrs.name().deserialize_name();
-        quote!(_serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #nfields, #visitor_expr))
+        quote!(_serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #field_count, #visitor_expr))
     };
 
-    let all_skipped = fields.iter().all(|field| field.attrs.skip_deserializing());
-    let visitor_var = if all_skipped {
+    let visitor_var = if field_count == 0 {
         quote!(_)
     } else {
         quote!(mut __seq)
@@ -550,13 +552,18 @@ fn deserialize_tuple_in_place(
     cattrs: &attr::Container,
     deserializer: Option<TokenStream>,
 ) -> Fragment {
+    assert!(!cattrs.has_flatten());
+
+    let field_count = fields
+        .iter()
+        .filter(|field| !field.attrs.skip_deserializing())
+        .count();
+
     let this_type = &params.this_type;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
         split_with_de_lifetime(params);
     let delife = params.borrowed.de_lifetime();
 
-    assert!(!cattrs.has_flatten());
-
     let is_enum = variant_ident.is_some();
     let expecting = match variant_ident {
         Some(variant_ident) => format!("tuple variant {}::{}", params.type_name(), variant_ident),
@@ -582,19 +589,18 @@ fn deserialize_tuple_in_place(
     };
 
     let dispatch = if let Some(deserializer) = deserializer {
-        quote!(_serde::Deserializer::deserialize_tuple(#deserializer, #nfields, #visitor_expr))
+        quote!(_serde::Deserializer::deserialize_tuple(#deserializer, #field_count, #visitor_expr))
     } else if is_enum {
-        quote!(_serde::de::VariantAccess::tuple_variant(__variant, #nfields, #visitor_expr))
+        quote!(_serde::de::VariantAccess::tuple_variant(__variant, #field_count, #visitor_expr))
     } else if nfields == 1 {
         let type_name = cattrs.name().deserialize_name();
         quote!(_serde::Deserializer::deserialize_newtype_struct(__deserializer, #type_name, #visitor_expr))
     } else {
         let type_name = cattrs.name().deserialize_name();
-        quote!(_serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #nfields, #visitor_expr))
+        quote!(_serde::Deserializer::deserialize_tuple_struct(__deserializer, #type_name, #field_count, #visitor_expr))
     };
 
-    let all_skipped = fields.iter().all(|field| field.attrs.skip_deserializing());
-    let visitor_var = if all_skipped {
+    let visitor_var = if field_count == 0 {
         quote!(_)
     } else {
         quote!(mut __seq)
@@ -1168,6 +1174,22 @@ fn deserialize_enum(
     params: &Parameters,
     variants: &[Variant],
     cattrs: &attr::Container,
+) -> Fragment {
+    // The variants have already been checked (in ast.rs) that all untagged variants appear at the end
+    match variants.iter().position(|var| var.attrs.untagged()) {
+        Some(variant_idx) => {
+            let (tagged, untagged) = variants.split_at(variant_idx);
+            let tagged_frag = Expr(deserialize_homogeneous_enum(params, tagged, cattrs));
+            deserialize_untagged_enum_after(params, untagged, cattrs, Some(tagged_frag))
+        }
+        None => deserialize_homogeneous_enum(params, variants, cattrs),
+    }
+}
+
+fn deserialize_homogeneous_enum(
+    params: &Parameters,
+    variants: &[Variant],
+    cattrs: &attr::Container,
 ) -> Fragment {
     match cattrs.tag() {
         attr::TagType::External => deserialize_externally_tagged_enum(params, variants, cattrs),
@@ -1668,6 +1690,16 @@ fn deserialize_untagged_enum(
     params: &Parameters,
     variants: &[Variant],
     cattrs: &attr::Container,
+) -> Fragment {
+    let first_attempt = None;
+    deserialize_untagged_enum_after(params, variants, cattrs, first_attempt)
+}
+
+fn deserialize_untagged_enum_after(
+    params: &Parameters,
+    variants: &[Variant],
+    cattrs: &attr::Container,
+    first_attempt: Option<Expr>,
 ) -> Fragment {
     let attempts = variants
         .iter()
@@ -1677,12 +1709,10 @@ fn deserialize_untagged_enum(
                 params,
                 variant,
                 cattrs,
-                quote!(
-                    _serde::__private::de::ContentRefDeserializer::<__D::Error>::new(&__content)
-                ),
+                quote!(__deserializer),
             ))
         });
-
+    let attempts = first_attempt.into_iter().chain(attempts);
     // TODO this message could be better by saving the errors from the failed
     // attempts. The heuristic used by TOML was to count the number of fields
     // processed before an error, and use the error that happened after the
@@ -1697,6 +1727,7 @@ fn deserialize_untagged_enum(
 
     quote_block! {
         let __content = try!(<_serde::__private::de::Content as _serde::Deserialize>::deserialize(__deserializer));
+        let __deserializer = _serde::__private::de::ContentRefDeserializer::<__D::Error>::new(&__content);
 
         #(
             if let _serde::__private::Ok(__ok) = #attempts {

serde_derive/src/internals/ast.rs

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

serde_derive/src/internals/attr.rs

@@ -740,6 +740,7 @@ pub struct Variant {
     serialize_with: Option<syn::ExprPath>,
     deserialize_with: Option<syn::ExprPath>,
     borrow: Option<BorrowAttribute>,
+    untagged: bool,
 }
 
 struct BorrowAttribute {
@@ -762,6 +763,7 @@ impl Variant {
         let mut serialize_with = Attr::none(cx, SERIALIZE_WITH);
         let mut deserialize_with = Attr::none(cx, DESERIALIZE_WITH);
         let mut borrow = Attr::none(cx, BORROW);
+        let mut untagged = BoolAttr::none(cx, UNTAGGED);
 
         for attr in &variant.attrs {
             if attr.path() != SERDE {
@@ -879,6 +881,8 @@ impl Variant {
                             cx.error_spanned_by(variant, msg);
                         }
                     }
+                } else if meta.path == UNTAGGED {
+                    untagged.set_true(&meta.path);
                 } else {
                     let path = meta.path.to_token_stream().to_string().replace(' ', "");
                     return Err(
@@ -905,6 +909,7 @@ impl Variant {
             serialize_with: serialize_with.get(),
             deserialize_with: deserialize_with.get(),
             borrow: borrow.get(),
+            untagged: untagged.get(),
         }
     }
 
@@ -956,6 +961,10 @@ impl Variant {
     pub fn deserialize_with(&self) -> Option<&syn::ExprPath> {
         self.deserialize_with.as_ref()
     }
+
+    pub fn untagged(&self) -> bool {
+        self.untagged
+    }
 }
 
 /// Represents field attribute information

serde_derive/src/internals/check.rs

@@ -110,9 +110,7 @@ fn check_flatten_field(cx: &Ctxt, style: Style, field: &Field) {
 fn check_identifier(cx: &Ctxt, cont: &Container) {
     let variants = match &cont.data {
         Data::Enum(variants) => variants,
-        Data::Struct(_, _) => {
-            return;
-        }
+        Data::Struct(_, _) => return,
     };
 
     for (i, variant) in variants.iter().enumerate() {
@@ -194,12 +192,10 @@ fn check_identifier(cx: &Ctxt, cont: &Container) {
 fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
     let variants = match &cont.data {
         Data::Enum(variants) => variants,
-        Data::Struct(_, _) => {
-            return;
-        }
+        Data::Struct(_, _) => return,
     };
 
-    for variant in variants.iter() {
+    for variant in variants {
         if variant.attrs.serialize_with().is_some() {
             if variant.attrs.skip_serializing() {
                 cx.error_spanned_by(

serde_derive/src/internals/ctxt.rs

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

serde_derive/src/lib.rs

@@ -13,7 +13,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.163")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.166")]
 #![allow(unknown_lints, bare_trait_objects)]
 // Ignored clippy lints
 #![allow(
@@ -92,7 +92,7 @@ mod try;
 pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);
     ser::expand_derive_serialize(&mut input)
-        .unwrap_or_else(to_compile_errors)
+        .unwrap_or_else(syn::Error::into_compile_error)
         .into()
 }
 
@@ -100,11 +100,6 @@ pub fn derive_serialize(input: TokenStream) -> TokenStream {
 pub fn derive_deserialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);
     de::expand_derive_deserialize(&mut input)
-        .unwrap_or_else(to_compile_errors)
+        .unwrap_or_else(syn::Error::into_compile_error)
         .into()
 }
-
-fn to_compile_errors(errors: Vec<syn::Error>) -> proc_macro2::TokenStream {
-    let compile_errors = errors.iter().map(syn::Error::to_compile_error);
-    quote!(#(#compile_errors)*)
-}

serde_derive/src/ser.rs

@@ -10,9 +10,7 @@ use internals::{attr, replace_receiver, Ctxt, Derive};
 use pretend;
 use this;
 
-pub fn expand_derive_serialize(
-    input: &mut syn::DeriveInput,
-) -> Result<TokenStream, Vec<syn::Error>> {
+pub fn expand_derive_serialize(input: &mut syn::DeriveInput) -> syn::Result<TokenStream> {
     replace_receiver(input);
 
     let ctxt = Ctxt::new();
@@ -475,17 +473,19 @@ fn serialize_variant(
             }
         };
 
-        let body = Match(match cattrs.tag() {
-            attr::TagType::External => {
+        let body = Match(match (cattrs.tag(), variant.attrs.untagged()) {
+            (attr::TagType::External, false) => {
                 serialize_externally_tagged_variant(params, variant, variant_index, cattrs)
             }
-            attr::TagType::Internal { tag } => {
+            (attr::TagType::Internal { tag }, false) => {
                 serialize_internally_tagged_variant(params, variant, cattrs, tag)
             }
-            attr::TagType::Adjacent { tag, content } => {
+            (attr::TagType::Adjacent { tag, content }, false) => {
                 serialize_adjacently_tagged_variant(params, variant, cattrs, tag, content)
             }
-            attr::TagType::None => serialize_untagged_variant(params, variant, cattrs),
+            (attr::TagType::None, _) | (_, true) => {
+                serialize_untagged_variant(params, variant, cattrs)
+            }
         });
 
         quote! {

serde_derive_internals/.clippy.toml

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

serde_derive_internals/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive_internals"
-version = "0.27.0" # remember to update html_root_url
+version = "0.28.0" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 description = "AST representation used by Serde derive macros. Unstable."
 documentation = "https://docs.rs/serde_derive_internals"
@@ -17,7 +17,7 @@ path = "lib.rs"
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = { version = "2.0", default-features = false, features = ["derive", "parsing", "printing", "clone-impls"] }
+syn = { version = "2.0.21", default-features = false, features = ["derive", "parsing", "printing", "clone-impls"] }
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]

serde_derive_internals/lib.rs

@@ -1,4 +1,4 @@
-#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.27.0")]
+#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.28.0")]
 #![allow(unknown_lints, bare_trait_objects)]
 // Ignored clippy lints
 #![allow(

serde_test/.clippy.toml

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

serde_test/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_test"
-version = "1.0.163" # remember to update html_root_url
+version = "1.0.166" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
 categories = ["development-tools::testing"]

serde_test/src/lib.rs

@@ -140,7 +140,7 @@
 //! # }
 //! ```
 
-#![doc(html_root_url = "https://docs.rs/serde_test/1.0.163")]
+#![doc(html_root_url = "https://docs.rs/serde_test/1.0.166")]
 #![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
 // Ignored clippy lints
 #![cfg_attr(feature = "cargo-clippy", allow(float_cmp, needless_doctest_main))]

test_suite/tests/test_annotations.rs

@@ -1533,7 +1533,7 @@ fn test_invalid_length_enum() {
             Token::TupleVariant {
                 name: "InvalidLengthEnum",
                 variant: "B",
-                len: 3,
+                len: 2,
             },
             Token::I32(1),
             Token::TupleVariantEnd,
@@ -2442,6 +2442,162 @@ fn test_untagged_enum_containing_flatten() {
     );
 }
 
+#[test]
+fn test_partially_untagged_enum() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    enum Exp {
+        Lambda(u32, Box<Exp>),
+        #[serde(untagged)]
+        App(Box<Exp>, Box<Exp>),
+        #[serde(untagged)]
+        Var(u32),
+    }
+    use Exp::*;
+
+    let data = Lambda(0, Box::new(App(Box::new(Var(0)), Box::new(Var(0)))));
+    assert_tokens(
+        &data,
+        &[
+            Token::TupleVariant {
+                name: "Exp",
+                variant: "Lambda",
+                len: 2,
+            },
+            Token::U32(0),
+            Token::Tuple { len: 2 },
+            Token::U32(0),
+            Token::U32(0),
+            Token::TupleEnd,
+            Token::TupleVariantEnd,
+        ],
+    );
+}
+
+#[test]
+fn test_partially_untagged_enum_generic() {
+    trait Trait<T> {
+        type Assoc;
+        type Assoc2;
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    enum E<A, B, C>
+    where
+        A: Trait<C, Assoc2 = B>,
+    {
+        A(A::Assoc),
+        #[serde(untagged)]
+        B(A::Assoc2),
+    }
+
+    impl<T> Trait<T> for () {
+        type Assoc = T;
+        type Assoc2 = bool;
+    }
+
+    type MyE = E<(), bool, u32>;
+    use E::*;
+
+    assert_tokens::<MyE>(&B(true), &[Token::Bool(true)]);
+
+    assert_tokens::<MyE>(
+        &A(5),
+        &[
+            Token::NewtypeVariant {
+                name: "E",
+                variant: "A",
+            },
+            Token::U32(5),
+        ],
+    );
+}
+
+#[test]
+fn test_partially_untagged_enum_desugared() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    enum Test {
+        A(u32, u32),
+        B(u32),
+        #[serde(untagged)]
+        C(u32),
+        #[serde(untagged)]
+        D(u32, u32),
+    }
+    use Test::*;
+
+    mod desugared {
+        use super::*;
+        #[derive(Serialize, Deserialize, PartialEq, Debug)]
+        pub(super) enum Test {
+            A(u32, u32),
+            B(u32),
+        }
+    }
+    use desugared::Test as TestTagged;
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(untagged)]
+    enum TestUntagged {
+        Tagged(TestTagged),
+        C(u32),
+        D(u32, u32),
+    }
+
+    impl From<Test> for TestUntagged {
+        fn from(test: Test) -> Self {
+            match test {
+                A(x, y) => TestUntagged::Tagged(TestTagged::A(x, y)),
+                B(x) => TestUntagged::Tagged(TestTagged::B(x)),
+                C(x) => TestUntagged::C(x),
+                D(x, y) => TestUntagged::D(x, y),
+            }
+        }
+    }
+
+    fn assert_tokens_desugared(value: Test, tokens: &[Token]) {
+        assert_tokens(&value, tokens);
+        let desugared: TestUntagged = value.into();
+        assert_tokens(&desugared, tokens);
+    }
+
+    assert_tokens_desugared(
+        A(0, 1),
+        &[
+            Token::TupleVariant {
+                name: "Test",
+                variant: "A",
+                len: 2,
+            },
+            Token::U32(0),
+            Token::U32(1),
+            Token::TupleVariantEnd,
+        ],
+    );
+
+    assert_tokens_desugared(
+        B(1),
+        &[
+            Token::NewtypeVariant {
+                name: "Test",
+                variant: "B",
+            },
+            Token::U32(1),
+        ],
+    );
+
+    assert_tokens_desugared(C(2), &[Token::U32(2)]);
+
+    assert_tokens_desugared(
+        D(3, 5),
+        &[
+            Token::Tuple { len: 2 },
+            Token::U32(3),
+            Token::U32(5),
+            Token::TupleEnd,
+        ],
+    );
+}
+
 #[test]
 fn test_flatten_untagged_enum() {
     #[derive(Serialize, Deserialize, PartialEq, Debug)]

test_suite/tests/test_de.rs

@@ -14,6 +14,7 @@ use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
 use std::default::Default;
 use std::ffi::{CStr, CString, OsString};
 use std::fmt::Debug;
+use std::iter;
 use std::net;
 use std::num::{
     NonZeroI128, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI8, NonZeroIsize, NonZeroU128,
@@ -199,7 +200,7 @@ fn assert_de_tokens_ignore(ignorable_tokens: &[Token]) {
     ]
     .into_iter()
     .chain(ignorable_tokens.iter().copied())
-    .chain(vec![Token::MapEnd].into_iter())
+    .chain(iter::once(Token::MapEnd))
     .collect();
 
     let expected = IgnoreBase { a: 1 };

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

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

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

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