Update src/librustc_mir/interpret/terminator.rs

Co-Authored-By: NRalf Jung <post@ralfj.de>

src/librustc_mir/interpret/terminator.rs

@@ -451,6 +451,7 @@ fn eval_fn_call(
 
     /// Evaluate a const function where all arguments (if any) are zero-sized types.
     /// The evaluation is memoized thanks to the query system.
+    // FIXME: Consider moving this to `const_eval.rs`.
     pub (crate) fn eval_const_fn_call(
         &mut self,
         gid: GlobalId<'tcx>,