Remap elaborated obligation constness

Author: fee1-dead

compiler/rustc_infer/src/traits/util.rs

@@ -145,7 +145,12 @@ impl<'tcx> Elaborator<'tcx> {
                 // Get predicates declared on the trait.
                 let predicates = tcx.super_predicates_of(data.def_id());
 
-                let obligations = predicates.predicates.iter().map(|&(pred, _)| {
+                let obligations = predicates.predicates.iter().map(|&(mut pred, _)| {
+                    // when parent predicate is non-const, elaborate it to non-const predicates.
+                    if data.constness == ty::BoundConstness::NotConst {
+                        pred = pred.without_const(tcx);
+                    }
+
                     predicate_obligation(
                         pred.subst_supertrait(tcx, &bound_predicate.rebind(data.trait_ref)),
                         obligation.param_env,