rustdoc: extend `#[doc(tuple_variadic)]` to fn pointers

The attribute is also renamed `fake_variadic`.

21 files changed, 61 insertions, 42 deletions

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index ad0e0384acf..e7004ff4bc5 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -402,8 +402,8 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     gate_feature_post!(self, rustdoc_internals, attr.span, msg);
                 }
 
-                if nested_meta.has_name(sym::tuple_variadic) {
-                    let msg = "`#[doc(tuple_variadic)]` is meant for internal use only";
+                if nested_meta.has_name(sym::fake_variadic) {
+                    let msg = "`#[doc(fake_variadic)]` is meant for internal use only";
                     gate_feature_post!(self, rustdoc_internals, attr.span, msg);
                 }
             }
diff --git a/compiler/rustc_error_messages/locales/en-US/passes.ftl b/compiler/rustc_error_messages/locales/en-US/passes.ftl
index e4c9a4dad7b..04c67cf8ff7 100644
--- a/compiler/rustc_error_messages/locales/en-US/passes.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/passes.ftl
@@ -81,8 +81,8 @@ passes-doc-keyword-not-mod = `#[doc(keyword = "...")]` should be used on modules
 
 passes-doc-keyword-invalid-ident = `{$doc_keyword}` is not a valid identifier
 
-passes-doc-tuple-variadic-not-first =
-    `#[doc(tuple_variadic)]` must be used on the first of a set of tuple trait impls with varying arity
+passes-doc-fake-variadic-not-valid =
+    `#[doc(fake_variadic)]` must be used on the first of a set of tuple or fn pointer trait impls with varying arity
 
 passes-doc-keyword-only-impl = `#[doc(keyword = "...")]` should be used on impl blocks
 
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index d96e7d3efe8..f88997f884a 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -706,14 +706,20 @@ impl CheckAttrVisitor<'_> {
         true
     }
 
-    fn check_doc_tuple_variadic(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
+    fn check_doc_fake_variadic(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
         match self.tcx.hir().find(hir_id).and_then(|node| match node {
             hir::Node::Item(item) => Some(&item.kind),
             _ => None,
         }) {
             Some(ItemKind::Impl(ref i)) => {
-                if !matches!(&i.self_ty.kind, hir::TyKind::Tup([_])) {
-                    self.tcx.sess.emit_err(errors::DocTupleVariadicNotFirst { span: meta.span() });
+                let is_valid = matches!(&i.self_ty.kind, hir::TyKind::Tup([_]))
+                    || if let hir::TyKind::BareFn(bare_fn_ty) = &i.self_ty.kind {
+                        bare_fn_ty.decl.inputs.len() == 1
+                    } else {
+                        false
+                    };
+                if !is_valid {
+                    self.tcx.sess.emit_err(errors::DocFakeVariadicNotValid { span: meta.span() });
                     return false;
                 }
             }
@@ -887,9 +893,9 @@ impl CheckAttrVisitor<'_> {
                             is_valid = false
                         }
 
-                        sym::tuple_variadic
-                            if !self.check_attr_not_crate_level(meta, hir_id, "tuple_variadic")
-                                || !self.check_doc_tuple_variadic(meta, hir_id) =>
+                        sym::fake_variadic
+                            if !self.check_attr_not_crate_level(meta, hir_id, "fake_variadic")
+                                || !self.check_doc_fake_variadic(meta, hir_id) =>
                         {
                             is_valid = false
                         }
@@ -939,7 +945,7 @@ impl CheckAttrVisitor<'_> {
                         | sym::notable_trait
                         | sym::passes
                         | sym::plugins
-                        | sym::tuple_variadic => {}
+                        | sym::fake_variadic => {}
 
                         sym::test => {
                             if !self.check_test_attr(meta, hir_id) {
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index f8e8720ab54..fcd1e9363b1 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -212,8 +212,8 @@ pub struct DocKeywordInvalidIdent {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(passes::doc_tuple_variadic_not_first)]
-pub struct DocTupleVariadicNotFirst {
+#[error(passes::doc_fake_variadic_not_valid)]
+pub struct DocFakeVariadicNotValid {
     #[primary_span]
     pub span: Span,
 }
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index d5e65c0b442..924bc2b6bce 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -685,6 +685,7 @@ symbols! {
         fabsf32,
         fabsf64,
         fadd_fast,
+        fake_variadic,
         fdiv_fast,
         feature,
         fence,
@@ -1460,7 +1461,6 @@ symbols! {
         tuple,
         tuple_from_req,
         tuple_indexing,
-        tuple_variadic,
         two_phase,
         ty,
         type_alias_enum_variants,
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index 6c3bb7229e5..372141e0933 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -2562,7 +2562,7 @@ macro_rules! tuple {
 
 macro_rules! maybe_tuple_doc {
     ($a:ident @ #[$meta:meta] $item:item) => {
-        #[doc(tuple_variadic)]
+        #[cfg_attr(not(bootstrap), doc(fake_variadic))]
         #[doc = "This trait is implemented for tuples up to twelve items long."]
         #[$meta]
         $item
diff --git a/library/core/src/hash/mod.rs b/library/core/src/hash/mod.rs
index cf428e0b1cf..5974562aced 100644
--- a/library/core/src/hash/mod.rs
+++ b/library/core/src/hash/mod.rs
@@ -900,7 +900,7 @@ mod impls {
 
     macro_rules! maybe_tuple_doc {
         ($a:ident @ #[$meta:meta] $item:item) => {
-            #[doc(tuple_variadic)]
+            #[cfg_attr(not(bootstrap), doc(fake_variadic))]
             #[doc = "This trait is implemented for tuples up to twelve items long."]
             #[$meta]
             $item
diff --git a/library/core/src/primitive_docs.rs b/library/core/src/primitive_docs.rs
index 401c8159988..4f08b562685 100644
--- a/library/core/src/primitive_docs.rs
+++ b/library/core/src/primitive_docs.rs
@@ -996,7 +996,7 @@ impl<T> (T,) {}
 // Fake impl that's only really used for docs.
 #[cfg(doc)]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[doc(tuple_variadic)]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
 /// This trait is implemented on arbitrary-length tuples.
 impl<T: Clone> Clone for (T,) {
     fn clone(&self) -> Self {
@@ -1007,7 +1007,7 @@ impl<T: Clone> Clone for (T,) {
 // Fake impl that's only really used for docs.
 #[cfg(doc)]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[doc(tuple_variadic)]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
 /// This trait is implemented on arbitrary-length tuples.
 impl<T: Copy> Copy for (T,) {
     // empty
diff --git a/library/core/src/tuple.rs b/library/core/src/tuple.rs
index b664b0bb866..d189e6400f1 100644
--- a/library/core/src/tuple.rs
+++ b/library/core/src/tuple.rs
@@ -107,7 +107,7 @@ macro_rules! tuple_impls {
 // Otherwise, it hides the docs entirely.
 macro_rules! maybe_tuple_doc {
     ($a:ident @ #[$meta:meta] $item:item) => {
-        #[doc(tuple_variadic)]
+        #[cfg_attr(not(bootstrap), doc(fake_variadic))]
         #[doc = "This trait is implemented for tuples up to twelve items long."]
         #[$meta]
         $item
diff --git a/library/std/src/primitive_docs.rs b/library/std/src/primitive_docs.rs
index 401c8159988..4f08b562685 100644
--- a/library/std/src/primitive_docs.rs
+++ b/library/std/src/primitive_docs.rs
@@ -996,7 +996,7 @@ impl<T> (T,) {}
 // Fake impl that's only really used for docs.
 #[cfg(doc)]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[doc(tuple_variadic)]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
 /// This trait is implemented on arbitrary-length tuples.
 impl<T: Clone> Clone for (T,) {
     fn clone(&self) -> Self {
@@ -1007,7 +1007,7 @@ impl<T: Clone> Clone for (T,) {
 // Fake impl that's only really used for docs.
 #[cfg(doc)]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[doc(tuple_variadic)]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
 /// This trait is implemented on arbitrary-length tuples.
 impl<T: Copy> Copy for (T,) {
     // empty
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 23af7d2ef1e..ce10ca9aa3d 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -506,8 +506,8 @@ pub(crate) fn build_impl(
             for_,
             items: trait_items,
             polarity,
-            kind: if utils::has_doc_flag(tcx, did, sym::tuple_variadic) {
-                ImplKind::TupleVaradic
+            kind: if utils::has_doc_flag(tcx, did, sym::fake_variadic) {
+                ImplKind::FakeVaradic
             } else {
                 ImplKind::Normal
             },
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index d6260b8ca06..a5c5d1ac182 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -2005,8 +2005,8 @@ fn clean_impl<'tcx>(
             for_,
             items,
             polarity: tcx.impl_polarity(def_id),
-            kind: if utils::has_doc_flag(tcx, def_id.to_def_id(), sym::tuple_variadic) {
-                ImplKind::TupleVaradic
+            kind: if utils::has_doc_flag(tcx, def_id.to_def_id(), sym::fake_variadic) {
+                ImplKind::FakeVaradic
             } else {
                 ImplKind::Normal
             },
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index d29ba2dedaf..5ddf7ea8a85 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -2394,7 +2394,7 @@ impl Impl {
 pub(crate) enum ImplKind {
     Normal,
     Auto,
-    TupleVaradic,
+    FakeVaradic,
     Blanket(Box<Type>),
 }
 
@@ -2407,8 +2407,8 @@ impl ImplKind {
         matches!(self, ImplKind::Blanket(_))
     }
 
-    pub(crate) fn is_tuple_variadic(&self) -> bool {
-        matches!(self, ImplKind::TupleVaradic)
+    pub(crate) fn is_fake_variadic(&self) -> bool {
+        matches!(self, ImplKind::FakeVaradic)
     }
 
     pub(crate) fn as_blanket_ty(&self) -> Option<&Type> {
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 9f46ab54d3e..291e6bc2fe4 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -1165,10 +1165,23 @@ impl clean::Impl {
 
             if let clean::Type::Tuple(types) = &self.for_ &&
                 let [clean::Type::Generic(name)] = &types[..] &&
-                (self.kind.is_tuple_variadic() || self.kind.is_auto()) {
+                (self.kind.is_fake_variadic() || self.kind.is_auto()) {
                 // Hardcoded anchor library/core/src/primitive_docs.rs
                 // Link should match `# Trait implementations`
                 primitive_link_fragment(f, PrimitiveType::Tuple, &format!("({name}₁, {name}₂, …, {name}ₙ)"), "#trait-implementations-1", cx)?;
+            } else if let clean::Type::BareFunction(bare_fn) = &self.for_ &&
+                let [clean::Argument { type_: clean::Type::Generic(name), .. }] = &bare_fn.decl.inputs.values[..] &&
+                (self.kind.is_fake_variadic() || self.kind.is_auto()) {
+                // Hardcoded anchor library/core/src/primitive_docs.rs
+                // Link should match `# Trait implementations`
+                primitive_link_fragment(f, PrimitiveType::Tuple, &format!("fn ({name}₁, {name}₂, …, {name}ₙ)"), "#trait-implementations-1", cx)?;
+                // Not implemented.
+                assert!(!bare_fn.decl.c_variadic);
+                // Write output.
+                if let clean::FnRetTy::Return(ty) = &bare_fn.decl.output {
+                    write!(f, " -> ")?;
+                    fmt_type(ty, f, use_absolute, cx)?;
+                }
             } else if let Some(ty) = self.kind.as_blanket_ty() {
                 fmt_type(ty, f, use_absolute, cx)?;
             } else {
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index 2598b9b0b28..9000ab472d9 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -574,7 +574,7 @@ impl FromWithTcx<clean::Impl> for Impl {
         let trait_ = trait_.map(|path| clean::Type::Path { path }.into_tcx(tcx));
         // FIXME: use something like ImplKind in JSON?
         let (synthetic, blanket_impl) = match kind {
-            clean::ImplKind::Normal | clean::ImplKind::TupleVaradic => (false, None),
+            clean::ImplKind::Normal | clean::ImplKind::FakeVaradic => (false, None),
             clean::ImplKind::Auto => (true, None),
             clean::ImplKind::Blanket(ty) => (false, Some(*ty)),
         };
diff --git a/src/test/rustdoc-ui/tuple-variadic-check.rs b/src/test/rustdoc-ui/tuple-variadic-check.rs
index 11ce2dbe280..505de53481f 100644
--- a/src/test/rustdoc-ui/tuple-variadic-check.rs
+++ b/src/test/rustdoc-ui/tuple-variadic-check.rs
@@ -3,13 +3,13 @@
 trait Mine {}
 
 // This one is fine
-#[doc(tuple_variadic)]
+#[doc(fake_variadic)]
 impl<T> Mine for (T,) {}
 
 trait Mine2 {}
 
 // This one is not
-#[doc(tuple_variadic)] //~ ERROR
+#[doc(fake_variadic)] //~ ERROR
 impl<T, U> Mine for (T,U) {}
 
 fn main() {}
diff --git a/src/test/rustdoc-ui/tuple-variadic-check.stderr b/src/test/rustdoc-ui/tuple-variadic-check.stderr
index 358d06d6a42..d127fb858d1 100644
--- a/src/test/rustdoc-ui/tuple-variadic-check.stderr
+++ b/src/test/rustdoc-ui/tuple-variadic-check.stderr
@@ -1,8 +1,8 @@
-error: `#[doc(tuple_variadic)]` must be used on the first of a set of tuple trait impls with varying arity
+error: `#[doc(fake_variadic)]` must be used on the first of a set of tuple or fn pointer trait impls with varying arity
   --> $DIR/tuple-variadic-check.rs:12:7
    |
-LL | #[doc(tuple_variadic)]
-   |       ^^^^^^^^^^^^^^
+LL | #[doc(fake_variadic)]
+   |       ^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/rustdoc/primitive-tuple-auto-trait.rs b/src/test/rustdoc/primitive-tuple-auto-trait.rs
index 71b0b077009..a2fbbf078d5 100644
--- a/src/test/rustdoc/primitive-tuple-auto-trait.rs
+++ b/src/test/rustdoc/primitive-tuple-auto-trait.rs
@@ -16,7 +16,7 @@
 // @has - '//h2[@id="trait-implementations-1"]' 'Trait implementations'
 /// # Trait implementations
 ///
-/// This header is hard-coded in the HTML format linking for `#[doc(tuple_variadics)]`.
+/// This header is hard-coded in the HTML format linking for `#[doc(fake_variadics)]`.
 /// To make sure it gets linked correctly, we need to make sure the hardcoded anchor
 /// in the code matches what rustdoc generates for the header.
 mod tuple_prim {}
diff --git a/src/test/rustdoc/primitive-tuple-variadic.rs b/src/test/rustdoc/primitive-tuple-variadic.rs
index 4fd6254f674..db7cfd60c71 100644
--- a/src/test/rustdoc/primitive-tuple-variadic.rs
+++ b/src/test/rustdoc/primitive-tuple-variadic.rs
@@ -7,12 +7,12 @@ pub trait Foo {}
 
 // @has foo/trait.Foo.html
 // @has - '//section[@id="impl-Foo-for-(T%2C)"]/h3' 'impl<T> Foo for (T₁, T₂, …, Tₙ)'
-#[doc(tuple_variadic)]
+#[doc(fake_variadic)]
 impl<T> Foo for (T,) {}
 
 pub trait Bar {}
 
 // @has foo/trait.Bar.html
 // @has - '//section[@id="impl-Bar-for-(U%2C)"]/h3' 'impl<U: Foo> Bar for (U₁, U₂, …, Uₙ)'
-#[doc(tuple_variadic)]
+#[doc(fake_variadic)]
 impl<U: Foo> Bar for (U,) {}
diff --git a/src/test/ui/feature-gates/feature-gate-rustdoc_internals.rs b/src/test/ui/feature-gates/feature-gate-rustdoc_internals.rs
index 6a144412d07..58306a4cfc9 100644
--- a/src/test/ui/feature-gates/feature-gate-rustdoc_internals.rs
+++ b/src/test/ui/feature-gates/feature-gate-rustdoc_internals.rs
@@ -4,7 +4,7 @@ mod foo {}
 
 trait Mine {}
 
-#[doc(tuple_variadic)]  //~ ERROR: `#[doc(tuple_variadic)]` is meant for internal use only
+#[doc(fake_variadic)]  //~ ERROR: `#[doc(fake_variadic)]` is meant for internal use only
 impl<T> Mine for (T,) {}
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-rustdoc_internals.stderr b/src/test/ui/feature-gates/feature-gate-rustdoc_internals.stderr
index 9fe08afd4f0..c4272a2c04c 100644
--- a/src/test/ui/feature-gates/feature-gate-rustdoc_internals.stderr
+++ b/src/test/ui/feature-gates/feature-gate-rustdoc_internals.stderr
@@ -7,11 +7,11 @@ LL | #[doc(keyword = "match")]
    = note: see issue #90418 <https://github.com/rust-lang/rust/issues/90418> for more information
    = help: add `#![feature(rustdoc_internals)]` to the crate attributes to enable
 
-error[E0658]: `#[doc(tuple_variadic)]` is meant for internal use only
+error[E0658]: `#[doc(fake_variadic)]` is meant for internal use only
   --> $DIR/feature-gate-rustdoc_internals.rs:7:1
    |
-LL | #[doc(tuple_variadic)]
-   | ^^^^^^^^^^^^^^^^^^^^^^
+LL | #[doc(fake_variadic)]
+   | ^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #90418 <https://github.com/rust-lang/rust/issues/90418> for more information
    = help: add `#![feature(rustdoc_internals)]` to the crate attributes to enable