Fix parsing of awaitable expressions with nested functions

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 41932)
+++ runtime/vm/parser.cc	(working copy)
@@ -9188,7 +9188,7 @@
                                     bool consume_cascades,
                                     SequenceNode** await_preamble) {
   TRACE_PARSER("ParseAwaitableExpr");
-  parsed_function()->reset_have_seen_await();
+  BoolScope saved_seen_await(&parsed_function()->have_seen_await_expr_, false);
   AstNode* expr = ParseExpr(require_compiletime_const, consume_cascades);
   if (parsed_function()->have_seen_await()) {
     // Make sure we do not reuse the scope to avoid creating contexts that we
@@ -9206,7 +9206,6 @@
     } else {
       *await_preamble = preamble;
     }
-    parsed_function()->reset_have_seen_await();
     return result;
   }
   return expr;