Auto merge of #142289 - fmease:maybe-perf-gen-args, r=<try>

[perf] Tweak `GenericArgs`-related functions

Author: rust-bors[bot]

compiler/rustc_middle/src/ty/context.rs

@@ -263,6 +263,15 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         }
     }
 
+    fn own_args_for_alias(
+        self,
+        def_id: DefId,
+        args: ty::GenericArgsRef<'tcx>,
+    ) -> &'tcx [ty::GenericArg<'tcx>] {
+        assert_matches!(self.def_kind(def_id), DefKind::AssocTy | DefKind::AssocConst);
+        &args[self.generics_of(def_id).parent_count..]
+    }
+
     fn trait_ref_and_own_args_for_alias(
         self,
         def_id: DefId,

compiler/rustc_type_ir/src/interner.rs

@@ -176,6 +176,12 @@ pub trait Interner:
 
     fn alias_term_kind(self, alias: ty::AliasTerm<Self>) -> ty::AliasTermKind;
 
+    fn own_args_for_alias(
+        self,
+        def_id: Self::DefId,
+        args: Self::GenericArgs,
+    ) -> Self::GenericArgsSlice;
+
     fn trait_ref_and_own_args_for_alias(
         self,
         def_id: Self::DefId,

compiler/rustc_type_ir/src/predicate.rs

@@ -664,14 +664,6 @@ impl<I: Interner> AliasTerm<I> {
         interner.parent(self.def_id)
     }
 
-    /// Extracts the underlying trait reference and own args from this projection.
-    /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
-    /// then this function would return a `T: StreamingIterator` trait reference and
-    /// `['a]` as the own args.
-    pub fn trait_ref_and_own_args(self, interner: I) -> (TraitRef<I>, I::GenericArgsSlice) {
-        interner.trait_ref_and_own_args_for_alias(self.def_id, self.args)
-    }
-
     /// Extracts the underlying trait reference from this projection.
     /// For example, if this is a projection of `<T as Iterator>::Item`,
     /// then this function would return a `T: Iterator` trait reference.
@@ -687,7 +679,15 @@ impl<I: Interner> AliasTerm<I> {
     /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
     /// then this function would return the slice `['a]` as the own args.
     pub fn own_args(self, interner: I) -> I::GenericArgsSlice {
-        self.trait_ref_and_own_args(interner).1
+        interner.own_args_for_alias(self.def_id, self.args)
+    }
+
+    /// Extracts the underlying trait reference and own args from this projection.
+    /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
+    /// then this function would return a `T: StreamingIterator` trait reference and
+    /// `['a]` as the own args.
+    pub fn trait_ref_and_own_args(self, interner: I) -> (TraitRef<I>, I::GenericArgsSlice) {
+        interner.trait_ref_and_own_args_for_alias(self.def_id, self.args)
     }
 }