Resolve consts in OpportunisticTypeResolver

src/librustc/infer/resolve.rs

 use super::{InferCtxt, FixupError, FixupResult, Span, type_variable::TypeVariableOrigin};
 use crate::mir::interpret::ConstValue;
-use crate::ty::{self, Ty, TyCtxt, TypeFoldable, InferConst};
+use crate::ty::{self, Ty, Const, TyCtxt, TypeFoldable, InferConst, TypeFlags};
 use crate::ty::fold::{TypeFolder, TypeVisitor};
 
 ///////////////////////////////////////////////////////////////////////////
@@ -31,8 +31,17 @@ fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
         if !t.has_infer_types() {
             t // micro-optimize -- if there is nothing in this type that this fold affects...
         } else {
-            let t0 = self.infcx.shallow_resolve(t);
-            t0.super_fold_with(self)
+            let t = self.infcx.shallow_resolve(t);
+            t.super_fold_with(self)
+        }
+    }
+
+    fn fold_const(&mut self, ct: &'tcx Const<'tcx>) -> &'tcx Const<'tcx> {
+        if !ct.has_type_flags(TypeFlags::HAS_CT_INFER) {
+            ct // micro-optimize -- if there is nothing in this const that this fold affects...
+        } else {
+            let ct = self.infcx.shallow_resolve(ct);
+            ct.super_fold_with(self)
         }
     }
 }

src/librustc/traits/codegen/mod.rs

@@ -157,7 +157,7 @@ fn drain_fulfillment_cx_or_panic<T>(&self,
         let result = self.tcx.erase_regions(&result);
 
         self.tcx.lift_to_global(&result).unwrap_or_else(||
-            bug!("Uninferred types/regions in `{:?}`", result)
+            bug!("Uninferred types/regions/consts in `{:?}`", result)
         )
     }
 }