Do not elaborate implicit supertrait associated type bounds into dyn trait's existential predicates

Author: compiler-errors

compiler/rustc_middle/src/ty/sty.rs

@@ -1025,6 +1025,10 @@ impl<'tcx> rustc_type_ir::inherent::Ty<TyCtxt<'tcx>> for Ty<'tcx> {
     fn has_unsafe_fields(self) -> bool {
         Ty::has_unsafe_fields(self)
     }
+
+    fn is_self_param(self) -> bool {
+        self.is_param(0)
+    }
 }
 
 /// Type utilities

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -725,6 +725,15 @@ where
                     assumption.upcast(cx),
                 ));
             }
+
+            for assumption in elaborate::implied_supertrait_projections(cx, principal) {
+                candidates.extend(G::probe_and_consider_object_bound_candidate(
+                    self,
+                    CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
+                    goal,
+                    assumption.with_self_ty(cx, self_ty).upcast(cx),
+                ));
+            }
         }
     }