code cleanup with err.emit_unless

Author: chenyukang

compiler/rustc_hir_typeck/src/expr.rs

@@ -1096,11 +1096,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // If the assignment expression itself is ill-formed, don't
             // bother emitting another error
-            let reported = if lhs_ty.references_error() || rhs_ty.references_error() {
-                err.delay_as_bug()
-            } else {
-                err.emit()
-            };
+            let reported = err.emit_unless(lhs_ty.references_error() || rhs_ty.references_error());
             return self.tcx.ty_error_with_guaranteed(reported);
         }
 

compiler/rustc_middle/src/ty/context.rs

@@ -1310,7 +1310,7 @@ impl<'tcx> TyCtxt<'tcx> {
         ty: Ty<'tcx>,
         reported: ErrorGuaranteed,
     ) -> Const<'tcx> {
-        self.mk_const(ty::ConstS { kind: ty::ConstKind::Error(reported), ty })
+        self.mk_const(ty::ConstKind::Error(reported), ty)
     }
 
     /// Like [TyCtxt::ty_error] but for constants.