Auto merge of #91406 - matthiaskrgr:rollup-a2whn8m, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - #91294 (Visit type in process_projection_elem.)
 - #91340 (Bump compiler_builtins to 0.1.55 to bring in fixes for targets lackin…)
 - #91366 (Only show notable traits if both types are the same)
 - #91397 (Emit a warning on generic parameters with doc comments)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

12 files changed, 92 insertions, 65 deletions

diff --git a/Cargo.lock b/Cargo.lock
index b2536c5cda1..2233162be3b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -678,9 +678,9 @@ dependencies = [
 
 [[package]]
 name = "compiler_builtins"
-version = "0.1.53"
+version = "0.1.55"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2467ff455350a4df7d02f1ed1449d0279605a763de5d586dcf6aa7d732508bcb"
+checksum = "c9ac60765140c97aaf531dae151a287646b0805ec725805da9e2a3ee31cd501c"
 dependencies = [
  "cc",
  "rustc-std-workspace-core",
diff --git a/compiler/rustc_borrowck/src/renumber.rs b/compiler/rustc_borrowck/src/renumber.rs
index 20567610f65..4b6cab24cdb 100644
--- a/compiler/rustc_borrowck/src/renumber.rs
+++ b/compiler/rustc_borrowck/src/renumber.rs
@@ -1,7 +1,7 @@
 use rustc_index::vec::IndexVec;
 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
 use rustc_middle::mir::visit::{MutVisitor, TyContext};
-use rustc_middle::mir::{Body, Location, PlaceElem, Promoted};
+use rustc_middle::mir::{Body, Location, Promoted};
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
 
@@ -62,22 +62,6 @@ impl<'a, 'tcx> MutVisitor<'tcx> for NllVisitor<'a, 'tcx> {
         debug!(?ty);
     }
 
-    fn process_projection_elem(
-        &mut self,
-        elem: PlaceElem<'tcx>,
-        _: Location,
-    ) -> Option<PlaceElem<'tcx>> {
-        if let PlaceElem::Field(field, ty) = elem {
-            let new_ty = self.renumber_regions(ty);
-
-            if new_ty != ty {
-                return Some(PlaceElem::Field(field, new_ty));
-            }
-        }
-
-        None
-    }
-
     #[instrument(skip(self), level = "debug")]
     fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, location: Location) {
         *substs = self.renumber_regions(*substs);
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index f36b9c82fac..077d3e1c820 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1079,6 +1079,10 @@ impl EarlyLintPass for UnusedDocComment {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
     }
+
+    fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
+        warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
+    }
 }
 
 declare_lint! {
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index fda7ebe1a49..4c23ab49fa2 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -1004,8 +1004,12 @@ macro_rules! visit_place_fns {
 
                     if new_local == local { None } else { Some(PlaceElem::Index(new_local)) }
                 }
+                PlaceElem::Field(field, ty) => {
+                    let mut new_ty = ty;
+                    self.visit_ty(&mut new_ty, TyContext::Location(location));
+                    if ty != new_ty { Some(PlaceElem::Field(field, new_ty)) } else { None }
+                }
                 PlaceElem::Deref
-                | PlaceElem::Field(..)
                 | PlaceElem::ConstantIndex { .. }
                 | PlaceElem::Subslice { .. }
                 | PlaceElem::Downcast(..) => None,
diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs
index 790d9243fba..c45946a9e2a 100644
--- a/compiler/rustc_mir_transform/src/dest_prop.rs
+++ b/compiler/rustc_mir_transform/src/dest_prop.rs
@@ -316,28 +316,6 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'tcx> {
         }
     }
 
-    fn process_projection_elem(
-        &mut self,
-        elem: PlaceElem<'tcx>,
-        _: Location,
-    ) -> Option<PlaceElem<'tcx>> {
-        match elem {
-            PlaceElem::Index(local) => {
-                if let Some(replacement) = self.replacements.for_src(local) {
-                    bug!(
-                        "cannot replace {:?} with {:?} in index projection {:?}",
-                        local,
-                        replacement,
-                        elem,
-                    );
-                } else {
-                    None
-                }
-            }
-            _ => None,
-        }
-    }
-
     fn visit_place(&mut self, place: &mut Place<'tcx>, context: PlaceContext, location: Location) {
         if let Some(replacement) = self.replacements.for_src(place.local) {
             // Rebase `place`s projections onto `replacement`'s.
diff --git a/compiler/rustc_mir_transform/src/reveal_all.rs b/compiler/rustc_mir_transform/src/reveal_all.rs
index 6c423a2bb57..3bcb71b64f4 100644
--- a/compiler/rustc_mir_transform/src/reveal_all.rs
+++ b/compiler/rustc_mir_transform/src/reveal_all.rs
@@ -35,24 +35,4 @@ impl<'tcx> MutVisitor<'tcx> for RevealAllVisitor<'tcx> {
     fn visit_ty(&mut self, ty: &mut Ty<'tcx>, _: TyContext) {
         *ty = self.tcx.normalize_erasing_regions(self.param_env, ty);
     }
-
-    #[inline]
-    fn process_projection_elem(
-        &mut self,
-        elem: PlaceElem<'tcx>,
-        _: Location,
-    ) -> Option<PlaceElem<'tcx>> {
-        match elem {
-            PlaceElem::Field(field, ty) => {
-                let new_ty = self.tcx.normalize_erasing_regions(self.param_env, ty);
-                if ty != new_ty { Some(PlaceElem::Field(field, new_ty)) } else { None }
-            }
-            // None of those contain a Ty.
-            PlaceElem::Index(..)
-            | PlaceElem::Deref
-            | PlaceElem::ConstantIndex { .. }
-            | PlaceElem::Subslice { .. }
-            | PlaceElem::Downcast(..) => None,
-        }
-    }
 }
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index b43445f2eed..f7111748321 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -16,7 +16,7 @@ panic_unwind = { path = "../panic_unwind", optional = true }
 panic_abort = { path = "../panic_abort" }
 core = { path = "../core" }
 libc = { version = "0.2.108", default-features = false, features = ['rustc-dep-of-std'] }
-compiler_builtins = { version = "0.1.53" }
+compiler_builtins = { version = "0.1.55" }
 profiler_builtins = { path = "../profiler_builtins", optional = true }
 unwind = { path = "../unwind" }
 hashbrown = { version = "0.11", default-features = false, features = ['rustc-dep-of-std'] }
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 37acf68defd..11dd140504a 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1468,6 +1468,45 @@ crate enum Type {
 rustc_data_structures::static_assert_size!(Type, 72);
 
 impl Type {
+    /// When comparing types for equality, it can help to ignore `&` wrapping.
+    crate fn without_borrowed_ref(&self) -> &Type {
+        let mut result = self;
+        while let Type::BorrowedRef { type_, .. } = result {
+            result = &*type_;
+        }
+        result
+    }
+
+    /// Check if two types are "potentially the same".
+    /// This is different from `Eq`, because it knows that things like
+    /// `Placeholder` are possible matches for everything.
+    crate fn is_same(&self, other: &Self, cache: &Cache) -> bool {
+        match (self, other) {
+            // Recursive cases.
+            (Type::Tuple(a), Type::Tuple(b)) => {
+                a.len() == b.len() && a.iter().zip(b).all(|(a, b)| a.is_same(&b, cache))
+            }
+            (Type::Slice(a), Type::Slice(b)) => a.is_same(&b, cache),
+            (Type::Array(a, al), Type::Array(b, bl)) => al == bl && a.is_same(&b, cache),
+            (Type::RawPointer(mutability, type_), Type::RawPointer(b_mutability, b_type_)) => {
+                mutability == b_mutability && type_.is_same(&b_type_, cache)
+            }
+            (
+                Type::BorrowedRef { mutability, type_, .. },
+                Type::BorrowedRef { mutability: b_mutability, type_: b_type_, .. },
+            ) => mutability == b_mutability && type_.is_same(&b_type_, cache),
+            // Placeholders and generics are equal to all other types.
+            (Type::Infer, _) | (_, Type::Infer) => true,
+            (Type::Generic(_), _) | (_, Type::Generic(_)) => true,
+            // Other cases, such as primitives, just use recursion.
+            (a, b) => a
+                .def_id(cache)
+                .and_then(|a| Some((a, b.def_id(cache)?)))
+                .map(|(a, b)| a == b)
+                .unwrap_or(false),
+        }
+    }
+
     crate fn primitive_type(&self) -> Option<PrimitiveType> {
         match *self {
             Primitive(p) | BorrowedRef { type_: box Primitive(p), .. } => Some(p),
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index 08022d526fe..8bf7d0416dd 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -1235,10 +1235,17 @@ fn should_render_item(item: &clean::Item, deref_mut_: bool, tcx: TyCtxt<'_>) ->
 fn notable_traits_decl(decl: &clean::FnDecl, cx: &Context<'_>) -> String {
     let mut out = Buffer::html();
 
-    if let Some(did) = decl.output.as_return().and_then(|t| t.def_id(cx.cache())) {
+    if let Some((did, ty)) = decl.output.as_return().and_then(|t| Some((t.def_id(cx.cache())?, t)))
+    {
         if let Some(impls) = cx.cache().impls.get(&did) {
             for i in impls {
                 let impl_ = i.inner_impl();
+                if !impl_.for_.without_borrowed_ref().is_same(ty.without_borrowed_ref(), cx.cache())
+                {
+                    // Two different types might have the same did,
+                    // without actually being the same.
+                    continue;
+                }
                 if let Some(trait_) = &impl_.trait_ {
                     let trait_did = trait_.def_id();
 
diff --git a/src/test/rustdoc/doc-notable_trait-slice.rs b/src/test/rustdoc/doc-notable_trait-slice.rs
new file mode 100644
index 00000000000..b0d41402721
--- /dev/null
+++ b/src/test/rustdoc/doc-notable_trait-slice.rs
@@ -0,0 +1,20 @@
+#![feature(doc_notable_trait)]
+
+#[doc(notable_trait)]
+pub trait SomeTrait {}
+
+pub struct SomeStruct;
+pub struct OtherStruct;
+impl SomeTrait for &[SomeStruct] {}
+
+// @has doc_notable_trait_slice/fn.bare_fn_matches.html
+// @has - '//code[@class="content"]' 'impl SomeTrait for &[SomeStruct]'
+pub fn bare_fn_matches() -> &'static [SomeStruct] {
+    &[]
+}
+
+// @has doc_notable_trait_slice/fn.bare_fn_no_matches.html
+// @!has - '//code[@class="content"]' 'impl SomeTrait for &[SomeStruct]'
+pub fn bare_fn_no_matches() -> &'static [OtherStruct] {
+    &[]
+}
diff --git a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
index fd9baf8c6b9..258f9e4831f 100644
--- a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
+++ b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
@@ -26,4 +26,7 @@ fn doc_comment_on_expr(num: u8) -> bool {
     num == 3
 }
 
+fn doc_comment_on_generic<#[doc = "x"] T>(val: T) {}
+//~^ ERROR: unused doc comment
+
 fn main() {}
diff --git a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
index 403367017c6..3ce1df71a2e 100644
--- a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
+++ b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
@@ -41,6 +41,14 @@ LL |     num == 3
    |
    = help: use `//` for a plain comment
 
+error: unused doc comment
+  --> $DIR/unused-doc-comments-edge-cases.rs:29:27
+   |
+LL | fn doc_comment_on_generic<#[doc = "x"] T>(val: T) {}
+   |                           ^^^^^^^^^^^^ - rustdoc does not generate documentation for generic parameters
+   |
+   = help: use `//` for a plain comment
+
 error[E0308]: mismatched types
   --> $DIR/unused-doc-comments-edge-cases.rs:14:9
    |
@@ -55,7 +63,7 @@ help: you might have meant to return this value
 LL |         return true;
    |         ++++++     +
 
-error: aborting due to 5 previous errors
+error: aborting due to 6 previous errors
 
 Some errors have detailed explanations: E0308, E0658.
 For more information about an error, try `rustc --explain E0308`.