Rollup merge of rust-lang#115201 - notriddle:notriddle/type-alias-impl-list, r=GuillaumeGomez

rustdoc: list matching impls on type aliases

Fixes rust-lang#32077

Fixes rust-lang#99952

Remake of rust-lang#112429

Partially reverts rust-lang#112543, but keeps the test case.

This version of the PR avoids the infinite loop by structurally matching types instead of using full unification. This version does not support type alias trait bounds, but the compiler does not enforce those anyway (rust-lang#21903).

r? `@GuillaumeGomez`

CC `@lcnr`

Author: GuillaumeGomez

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
+        //
+        // FIXME(lazy_type_alias): Once the feature is complete or stable, rewrite this to use type unification.
+        // Be aware of `tests/rustdoc/issue-112515-impl-ty-alias.rs` which might regress.
+        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
+    }
+}