Check has_typeck_tables before calling typeck_tables_of

src/librustc_mir/const_eval/eval_queries.rs

@@ -288,7 +288,10 @@ pub fn const_eval_raw_provider<'tcx>(
     let cid = key.value;
     let def_id = cid.instance.def.def_id();
 
-    if def_id.is_local() && tcx.typeck_tables_of(def_id).tainted_by_errors {
+    if def_id.is_local()
+        && tcx.has_typeck_tables(def_id)
+        && tcx.typeck_tables_of(def_id).tainted_by_errors
+    {
         return Err(ErrorHandled::Reported);
     }
 

src/test/ui/consts/issue-68684.rs

@@ -0,0 +1,15 @@
+// check-pass
+
+enum _Enum {
+    A(),
+}
+
+type _E = _Enum;
+
+const fn _a() -> _Enum {
+    _E::A()
+}
+
+const _A: _Enum = _a();
+
+fn main() {}