Only prefer Sized candidates, and only if they certainly hold

1 files changed, 5 insertions, 2 deletions

diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index 749f3c31bf8..aa2ee756bc5 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -95,8 +95,11 @@ pub type EvaluationCache<'tcx, ENV> = Cache<(ENV, ty::PolyTraitPredicate<'tcx>),
 /// parameter environment.
 #[derive(PartialEq, Eq, Debug, Clone, TypeVisitable)]
 pub enum SelectionCandidate<'tcx> {
-    /// UwU
-    SizedCandidate,
+    /// A built-in implementation for the `Sized` trait. This is preferred
+    /// over all other candidates.
+    SizedCandidate {
+        has_nested: bool,
+    },
 
     /// A builtin implementation for some specific traits, used in cases
     /// where we cannot rely an ordinary library implementations.