Use equality when relating formal and expected type in arg checking

1 files changed, 4 insertions, 5 deletions

diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index eebb0217990..16d65726128 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -292,21 +292,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             let coerce_error =
                 self.coerce(provided_arg, checked_ty, coerced_ty, AllowTwoPhase::Yes, None).err();
-
             if coerce_error.is_some() {
                 return Compatibility::Incompatible(coerce_error);
             }
 
-            // 3. Check if the formal type is a supertype of the checked one
-            //    and register any such obligations for future type checks
-            let supertype_error = self.at(&self.misc(provided_arg.span), self.param_env).sup(
+            // 3. Check if the formal type is actually equal to the checked one
+            //    and register any such obligations for future type checks.
+            let formal_ty_error = self.at(&self.misc(provided_arg.span), self.param_env).eq(
                 DefineOpaqueTypes::Yes,
                 formal_input_ty,
                 coerced_ty,
             );
 
             // If neither check failed, the types are compatible
-            match supertype_error {
+            match formal_ty_error {
                 Ok(InferOk { obligations, value: () }) => {
                     self.register_predicates(obligations);
                     Compatibility::Compatible