Stall computing instance for drop shim until it has no unsubstituted …

…const params

compiler/rustc_ty_utils/src/instance.rs

@@ -7,7 +7,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::traits::{BuiltinImplSource, CodegenObligationError};
 use rustc_middle::ty::util::AsyncDropGlueMorphology;
 use rustc_middle::ty::GenericArgsRef;
-use rustc_middle::ty::{self, Instance, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, Instance, TyCtxt, TypeFlags, TypeVisitableExt};
 use rustc_span::sym;
 use rustc_trait_selection::traits;
 use rustc_type_ir::ClosureKind;
@@ -53,6 +53,15 @@ fn resolve_instance<'tcx>(
                     _ => return Ok(None),
                 }
 
+                // FIXME(#127030): `ConstParamHasTy` has bad interactions with
+                // the drop shim builder, which does not evaluate predicates in
+                // the correct param-env for types being dropped. Stall resolving
+                // the MIR for this instance until all of its const params are
+                // substituted.
+                if ty.has_type_flags(TypeFlags::HAS_CT_PARAM) {
+                    return Ok(None);
+                }
+
                 ty::InstanceKind::DropGlue(def_id, Some(ty))
             } else {
                 debug!(" => trivial drop glue");

tests/ui/const-generics/polymorphic-drop-shim.rs

@@ -1,8 +1,5 @@
 //@ compile-flags: -Zinline-mir=yes --crate-type=lib
-
-//@ known-bug: unknown
-//@ build-fail
-//@ failure-status: 101
+//@ build-pass
 
 use std::mem::ManuallyDrop;