Try to fix problem

Author: fee1-dead

compiler/rustc_mir/src/borrow_check/type_check/mod.rs

@@ -1085,11 +1085,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         span_mirbug!(
                             self,
                             user_annotation,
-                            "bad user type AscribeUserType({:?}, {:?} {:?}): {:?}",
+                            "bad user type AscribeUserType({:?}, {:?} {:?}, type_of={:?}): {:?}",
                             inferred_ty,
                             def_id,
                             user_substs,
-                            terr
+                            self.tcx().type_of(def_id),
+                            terr,
                         );
                     }
                 }

compiler/rustc_traits/src/type_op.rs

@@ -6,7 +6,9 @@ use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::TraitEngineExt as _;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::subst::{GenericArg, Subst, UserSelfTy, UserSubsts};
-use rustc_middle::ty::{self, FnSig, Lift, PolyFnSig, Ty, TyCtxt, TypeFoldable, Variance};
+use rustc_middle::ty::{
+    self, FnSig, Lift, PolyFnSig, PredicateKind, Ty, TyCtxt, TypeFoldable, Variance,
+};
 use rustc_middle::ty::{ParamEnv, ParamEnvAnd, Predicate, ToPredicate};
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
@@ -85,7 +87,16 @@ impl AscribeUserTypeCx<'me, 'tcx> {
         Ok(())
     }
 
-    fn prove_predicate(&mut self, predicate: Predicate<'tcx>) {
+    fn prove_predicate(&mut self, mut predicate: Predicate<'tcx>) {
+        if let PredicateKind::Trait(mut tr) = predicate.kind().skip_binder() {
+            if let hir::Constness::Const = tr.constness {
+                // FIXME check if we actually want to prove const predicates inside AscribeUserType
+                tr.constness = hir::Constness::NotConst;
+                predicate =
+                    predicate.kind().rebind(PredicateKind::Trait(tr)).to_predicate(self.tcx());
+            }
+        }
+
         self.fulfill_cx.register_predicate_obligation(
             self.infcx,
             Obligation::new(ObligationCause::dummy(), self.param_env, predicate),
@@ -126,6 +137,7 @@ impl AscribeUserTypeCx<'me, 'tcx> {
         // outlives" error messages.
         let instantiated_predicates =
             self.tcx().predicates_of(def_id).instantiate(self.tcx(), substs);
+        debug!(?instantiated_predicates.predicates);
         for instantiated_predicate in instantiated_predicates.predicates {
             let instantiated_predicate = self.normalize(instantiated_predicate);
             self.prove_predicate(instantiated_predicate);