Use a query rather than recomputing the tail repeatedly

3 files changed, 11 insertions, 37 deletions

diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index a1df27ac788..40d0028db86 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1026,6 +1026,13 @@ rustc_queries! {
         separate_provide_extern
     }
 
+    /// Given an `impl_def_id`, return true if the self type is guaranteed to be unsized due
+    /// to either being one of the built-in unsized types (str/slice/dyn) or to be a struct
+    /// whose tail is one of those types.
+    query impl_self_is_guaranteed_unsized(impl_def_id: DefId) -> bool {
+        desc { |tcx| "computing whether `{}` has a guaranteed unsized self type", tcx.def_path_str(impl_def_id) }
+    }
+
     /// Maps a `DefId` of a type to a list of its inherent impls.
     /// Contains implementations of methods that are inherent to a type.
     /// Methods in these implementations don't need to be exported.
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 162ca1f4af8..abf6cbbcd87 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -437,6 +437,10 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         )
     }
 
+    fn impl_self_is_guaranteed_unsized(self, impl_def_id: DefId) -> bool {
+        self.impl_self_is_guaranteed_unsized(impl_def_id)
+    }
+
     fn has_target_features(self, def_id: DefId) -> bool {
         !self.codegen_fn_attrs(def_id).target_features.is_empty()
     }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index fb15ab8d848..27ee363f1c1 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -2029,43 +2029,6 @@ impl<'tcx> Ty<'tcx> {
     pub fn is_known_rigid(self) -> bool {
         self.kind().is_known_rigid()
     }
-
-    /// Returns true if the type is guaranteed to be one of the three built-in unsized types:
-    /// `dyn Trait`/`[T]`/`str`. This function is *raw* because it does not compute the struct
-    /// tail of the type, so you are responsible for doing that yourself.
-    // NOTE: Keep this in sync with `rustc_type_ir`'s copy.
-    pub fn is_guaranteed_unsized_raw(self) -> bool {
-        match self.kind() {
-            Dynamic(_, _, ty::Dyn) | ty::Slice(_) | ty::Str => true,
-            Bool
-            | Char
-            | Int(_)
-            | Uint(_)
-            | Float(_)
-            | Adt(_, _)
-            | Foreign(_)
-            | Array(_, _)
-            | Pat(_, _)
-            | RawPtr(_, _)
-            | Ref(_, _, _)
-            | FnDef(_, _)
-            | FnPtr(_, _)
-            | UnsafeBinder(_)
-            | Closure(_, _)
-            | CoroutineClosure(_, _)
-            | Coroutine(_, _)
-            | CoroutineWitness(_, _)
-            | Never
-            | Tuple(_)
-            | Alias(_, _)
-            | Param(_)
-            | Bound(_, _)
-            | Placeholder(_)
-            | Infer(_)
-            | Error(_)
-            | Dynamic(_, _, ty::DynStar) => false,
-        }
-    }
 }
 
 impl<'tcx> rustc_type_ir::inherent::Tys<TyCtxt<'tcx>> for &'tcx ty::List<Ty<'tcx>> {