Revert "rustdoc: list matching impls on type aliases"

This reverts commit 19edb3c.

Author: notriddle

src/librustdoc/html/render/mod.rs

@@ -54,7 +54,6 @@ 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},
@@ -63,7 +62,6 @@ 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;
@@ -1155,40 +1153,8 @@ fn render_assoc_items_inner(
     info!("Documenting associated items of {:?}", containing_item.name);
     let shared = Rc::clone(&cx.shared);
     let cache = &shared.cache;
-    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();
+    let Some(v) = cache.impls.get(&it) else { return };
+    let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
     if !non_trait.is_empty() {
         let mut tmp_buf = Buffer::html();
         let (render_mode, id, class_html) = match what {
@@ -1217,9 +1183,6 @@ 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,
@@ -1265,10 +1228,8 @@ 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()
-            .filter(|t| saw_impls.insert(t.def_id()))
-            .partition(|t| t.inner_impl().kind.is_blanket());
+        let (blanket_impl, concrete): (Vec<&Impl>, _) =
+            concrete.into_iter().partition(|t| t.inner_impl().kind.is_blanket());
 
         render_all_impls(w, cx, containing_item, &concrete, &synthetic, &blanket_impl);
     }