rustdoc: list matching impls on type aliases

library/core/src/ptr/mut_ptr.rs

@@ -109,7 +109,7 @@ impl<T: ?Sized> *mut T {
     /// with [`cast_mut`] on `*const T` and may have documentation value if used instead of implicit
     /// coercion.
     ///
-    /// [`cast_mut`]: #method.cast_mut
+    /// [`cast_mut`]: pointer::cast_mut
     #[stable(feature = "ptr_const_cast", since = "1.65.0")]
     #[rustc_const_stable(feature = "ptr_const_cast", since = "1.65.0")]
     #[rustc_diagnostic_item = "ptr_cast_const"]
@@ -121,7 +121,7 @@ impl<T: ?Sized> *mut T {
     /// Casts a pointer to its raw bits.
     ///
     /// This is equivalent to `as usize`, but is more specific to enhance readability.
-    /// The inverse method is [`from_bits`](#method.from_bits-1).
+    /// The inverse method is [`from_bits`](pointer#method.from_bits-1).
     ///
     /// In particular, `*p as usize` and `p as usize` will both compile for
     /// pointers to numeric types but do very different things, so using this
@@ -157,7 +157,7 @@ impl<T: ?Sized> *mut T {
     /// Creates a pointer from its raw bits.
     ///
     /// This is equivalent to `as *mut T`, but is more specific to enhance readability.
-    /// The inverse method is [`to_bits`](#method.to_bits-1).
+    /// The inverse method is [`to_bits`](pointer#method.to_bits-1).
     ///
     /// # Examples
     ///
@@ -307,7 +307,7 @@ impl<T: ?Sized> *mut T {
     ///
     /// For the mutable counterpart see [`as_mut`].
     ///
-    /// [`as_uninit_ref`]: #method.as_uninit_ref-1
+    /// [`as_uninit_ref`]: pointer#method.as_uninit_ref-1
     /// [`as_mut`]: #method.as_mut
     ///
     /// # Safety
@@ -373,7 +373,7 @@ impl<T: ?Sized> *mut T {
     ///
     /// For the mutable counterpart see [`as_uninit_mut`].
     ///
-    /// [`as_ref`]: #method.as_ref-1
+    /// [`as_ref`]: pointer#method.as_ref-1
     /// [`as_uninit_mut`]: #method.as_uninit_mut
     ///
     /// # Safety
@@ -628,7 +628,7 @@ impl<T: ?Sized> *mut T {
     /// For the shared counterpart see [`as_ref`].
     ///
     /// [`as_uninit_mut`]: #method.as_uninit_mut
-    /// [`as_ref`]: #method.as_ref-1
+    /// [`as_ref`]: pointer#method.as_ref-1
     ///
     /// # Safety
     ///
@@ -693,7 +693,7 @@ impl<T: ?Sized> *mut T {
     /// For the shared counterpart see [`as_uninit_ref`].
     ///
     /// [`as_mut`]: #method.as_mut
-    /// [`as_uninit_ref`]: #method.as_uninit_ref-1
+    /// [`as_uninit_ref`]: pointer#method.as_uninit_ref-1
     ///
     /// # Safety
     ///
@@ -783,7 +783,7 @@ impl<T: ?Sized> *mut T {
     ///
     /// This function is the inverse of [`offset`].
     ///
-    /// [`offset`]: #method.offset-1
+    /// [`offset`]: pointer#method.offset-1
     ///
     /// # Safety
     ///
@@ -2064,7 +2064,7 @@ impl<T> *mut [T] {
     ///
     /// For the mutable counterpart see [`as_uninit_slice_mut`].
     ///
-    /// [`as_ref`]: #method.as_ref-1
+    /// [`as_ref`]: pointer#method.as_ref-1
     /// [`as_uninit_slice_mut`]: #method.as_uninit_slice_mut
     ///
     /// # Safety

src/librustdoc/html/render/mod.rs

@@ -54,6 +54,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def_id::{DefId, DefIdSet};
 use rustc_hir::Mutability;
 use rustc_middle::middle::stability;
+use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
 use rustc_middle::ty::TyCtxt;
 use rustc_span::{
     symbol::{sym, Symbol},
@@ -62,6 +63,7 @@ use rustc_span::{
 use serde::ser::{SerializeMap, SerializeSeq};
 use serde::{Serialize, Serializer};
 
+use crate::clean::types::TypeAliasItem;
 use crate::clean::{self, ItemId, RenderedLink, SelfTy};
 use crate::error::Error;
 use crate::formats::cache::Cache;
@@ -1139,8 +1141,40 @@ fn render_assoc_items_inner(
     info!("Documenting associated items of {:?}", containing_item.name);
     let shared = Rc::clone(&cx.shared);
     let cache = &shared.cache;
-    let Some(v) = cache.impls.get(&it) else { return };
-    let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
+    let tcx = cx.tcx();
+    let av = if let TypeAliasItem(ait) = &*containing_item.kind &&
+        let aliased_clean_type = ait.item_type.as_ref().unwrap_or(&ait.type_) &&
+        let Some(aliased_type_defid) = aliased_clean_type.def_id(cache) &&
+        let Some(mut av) = cache.impls.get(&aliased_type_defid).cloned() &&
+        let Some(alias_def_id) = containing_item.item_id.as_def_id()
+    {
+        // This branch of the compiler compares types structually, but does
+        // not check trait bounds. That's probably fine, since type aliases
+        // don't normally constrain on them anyway.
+        // https://github.com/rust-lang/rust/issues/21903
+        //
+        // If that changes, then this will need to check them with type
+        // unification.
+        let aliased_ty = tcx.type_of(alias_def_id).skip_binder();
+        let reject_cx = DeepRejectCtxt {
+            treat_obligation_params: TreatParams::AsCandidateKey,
+        };
+        av.retain(|impl_| {
+            if let Some(impl_def_id) = impl_.impl_item.item_id.as_def_id() {
+                reject_cx.types_may_unify(aliased_ty, tcx.type_of(impl_def_id).skip_binder())
+            } else {
+                false
+            }
+        });
+        av
+    } else {
+        Vec::new()
+    };
+    let blank = Vec::new();
+    let v = cache.impls.get(&it).unwrap_or(&blank);
+    let (non_trait, traits): (Vec<_>, _) =
+        v.iter().chain(&av[..]).partition(|i| i.inner_impl().trait_.is_none());
+    let mut saw_impls = FxHashSet::default();
     if !non_trait.is_empty() {
         let mut tmp_buf = Buffer::html();
         let (render_mode, id, class_html) = match what {
@@ -1169,6 +1203,9 @@ fn render_assoc_items_inner(
         };
         let mut impls_buf = Buffer::html();
         for i in &non_trait {
+            if !saw_impls.insert(i.def_id()) {
+                continue;
+            }
             render_impl(
                 &mut impls_buf,
                 cx,
@@ -1214,8 +1251,10 @@ fn render_assoc_items_inner(
 
         let (synthetic, concrete): (Vec<&Impl>, Vec<&Impl>) =
             traits.into_iter().partition(|t| t.inner_impl().kind.is_auto());
-        let (blanket_impl, concrete): (Vec<&Impl>, _) =
-            concrete.into_iter().partition(|t| t.inner_impl().kind.is_blanket());
+        let (blanket_impl, concrete): (Vec<&Impl>, _) = concrete
+            .into_iter()
+            .filter(|t| saw_impls.insert(t.def_id()))
+            .partition(|t| t.inner_impl().kind.is_blanket());
 
         render_all_impls(w, cx, containing_item, &concrete, &synthetic, &blanket_impl);
     }

tests/rustdoc/issue-32077-type-alias-impls.rs

@@ -0,0 +1,59 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/32077>.
+
+#![crate_name = "foo"]
+
+pub struct GenericStruct<T>(T);
+
+impl<T> GenericStruct<T> {
+    pub fn on_gen(arg: T) {}
+}
+
+impl GenericStruct<u32> {
+    pub fn on_u32(arg: u32) {}
+}
+
+pub trait Foo {}
+pub trait Bar {}
+
+impl<T> Foo for GenericStruct<T> {}
+impl Bar for GenericStruct<u32> {}
+
+// @has 'foo/type.TypedefStruct.html'
+// We check that we have the implementation of the type alias itself.
+// @has - '//*[@id="impl-TypedefStruct"]/h3' 'impl TypedefStruct'
+// @has - '//*[@id="method.on_alias"]/h4' 'pub fn on_alias()'
+// @has - '//*[@id="impl-GenericStruct%3CT%3E"]/h3' 'impl<T> GenericStruct<T>'
+// @has - '//*[@id="method.on_gen"]/h4' 'pub fn on_gen(arg: T)'
+// @has - '//*[@id="impl-Foo-for-GenericStruct%3CT%3E"]/h3' 'impl<T> Foo for GenericStruct<T>'
+// This trait implementation doesn't match the type alias parameters so shouldn't appear in docs.
+// @!has - '//h3' 'impl Bar for GenericStruct<u32> {}'
+// Same goes for the `Deref` impl.
+// @!has - '//h2' 'Methods from Deref<Target = u32>'
+pub type TypedefStruct = GenericStruct<u8>;
+
+impl TypedefStruct {
+    pub fn on_alias() {}
+}
+
+impl std::ops::Deref for GenericStruct<u32> {
+    type Target = u32;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+pub struct Wrap<T>(GenericStruct<T>);
+
+// @has 'foo/type.Alias.html'
+// @has - '//h2' 'Methods from Deref<Target = u32>'
+// @has - '//*[@id="impl-Deref-for-Wrap%3CT%3E"]/h3' 'impl<T> Deref for Wrap<T>'
+pub type Alias = Wrap<u32>;
+
+impl<T> std::ops::Deref for Wrap<T> {
+    type Target = GenericStruct<T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}