[experiment] Use new solver in MIR validator subtyping checks

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -387,7 +387,14 @@ pub(super) fn mir_assign_valid_types<'tcx>(
     // all normal lifetimes are erased, higher-ranked types with their
     // late-bound lifetimes are still around and can lead to type
     // differences.
-    if util::relate_types(tcx, param_env, Variance::Covariant, src.ty, dest.ty) {
+    if util::relate_types(
+        tcx,
+        param_env,
+        Variance::Covariant,
+        src.ty,
+        dest.ty,
+        tcx.next_trait_solver_globally(),
+    ) {
         // Make sure the layout is equal, too -- just to be safe. Miri really
         // needs layout equality. For performance reason we skip this check when
         // the types are equal. Equal types *can* have different layouts when

compiler/rustc_const_eval/src/transform/validate.rs

@@ -634,7 +634,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             Variance::Covariant
         };
 
-        crate::util::relate_types(self.tcx, self.param_env, variance, src, dest)
+        crate::util::relate_types(self.tcx, self.param_env, variance, src, dest, true)
     }
 }
 
@@ -792,6 +792,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     Variance::Covariant,
                     ty,
                     place_ref.ty(&self.body.local_decls, self.tcx).ty,
+                    true,
                 ) {
                     self.fail(
                         location,

compiler/rustc_const_eval/src/util/compare_types.rs

@@ -17,15 +17,16 @@ pub fn is_equal_up_to_subtyping<'tcx>(
     param_env: ParamEnv<'tcx>,
     src: Ty<'tcx>,
     dest: Ty<'tcx>,
+    next_trait_solver: bool,
 ) -> bool {
     // Fast path.
     if src == dest {
         return true;
     }
 
     // Check for subtyping in either direction.
-    relate_types(tcx, param_env, Variance::Covariant, src, dest)
-        || relate_types(tcx, param_env, Variance::Covariant, dest, src)
+    relate_types(tcx, param_env, Variance::Covariant, src, dest, next_trait_solver)
+        || relate_types(tcx, param_env, Variance::Covariant, dest, src, next_trait_solver)
 }
 
 /// Returns whether `src` is a subtype of `dest`, i.e. `src <: dest`.
@@ -42,13 +43,17 @@ pub fn relate_types<'tcx>(
     variance: Variance,
     src: Ty<'tcx>,
     dest: Ty<'tcx>,
+    next_trait_solver: bool,
 ) -> bool {
     if src == dest {
         return true;
     }
 
-    let mut builder =
-        tcx.infer_ctxt().ignoring_regions().with_opaque_type_inference(DefiningAnchor::Bubble);
+    let mut builder = tcx
+        .infer_ctxt()
+        .ignoring_regions()
+        .with_next_trait_solver(next_trait_solver)
+        .with_opaque_type_inference(DefiningAnchor::Bubble);
     let infcx = builder.build();
     let ocx = ObligationCtxt::new(&infcx);
     let cause = ObligationCause::dummy();

compiler/rustc_mir_transform/src/inline.rs

@@ -220,6 +220,7 @@ impl<'tcx> Inliner<'tcx> {
             ty::Variance::Covariant,
             output_type,
             destination_ty,
+            true,
         ) {
             trace!(?output_type, ?destination_ty);
             return Err("failed to normalize return type");
@@ -256,6 +257,7 @@ impl<'tcx> Inliner<'tcx> {
                     ty::Variance::Covariant,
                     input_type,
                     arg_ty,
+                    true,
                 ) {
                     trace!(?arg_ty, ?input_type);
                     return Err("failed to normalize tuple argument type");
@@ -271,6 +273,7 @@ impl<'tcx> Inliner<'tcx> {
                     ty::Variance::Covariant,
                     input_type,
                     arg_ty,
+                    true,
                 ) {
                     trace!(?arg_ty, ?input_type);
                     return Err("failed to normalize argument type");