Don't use instantiate_and_normalize_erasing_regions or eval

Author: estebank

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -374,20 +374,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                                 Some(v) => v.clone(),
                                 None => match variant.fields[n].value {
                                     Some(def) => {
-                                        let value =
-                                            this.tcx.instantiate_and_normalize_erasing_regions(
-                                                args,
-                                                this.infcx.typing_env(this.param_env),
-                                                Const::from_unevaluated(this.tcx, def),
-                                            );
-                                        let value = match value.eval(
-                                            this.tcx,
-                                            this.infcx.typing_env(this.param_env),
-                                            expr_span,
-                                        ) {
-                                            Ok(val) => Const::Val(val, value.ty()),
-                                            Err(_) => value,
-                                        };
+                                        let value = Const::from_unevaluated(this.tcx, def)
+                                            .instantiate(this.tcx, args);
                                         this.literal_operand(expr_span, value)
                                     }
                                     None => {