[parser] unify metaproperty parsing and require unescaped property name

test/message/function-sent-escaped.js

Index: test/message/function-sent-escaped.js
diff --git a/test/message/arrow-invalid-rest-2.js b/test/message/function-sent-escaped.js
similarity index 60%
copy from test/message/arrow-invalid-rest-2.js
copy to test/message/function-sent-escaped.js
index 3517803d30256b09e78a1aa1f43817e733dc060e..aa17258f854a96a65617feb572389464677a81ce 100644
--- a/test/message/arrow-invalid-rest-2.js
+++ b/test/message/function-sent-escaped.js
@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-//
+// Flags: --harmony-function-sent
 
-var f = (a, ...x = 10) => x;
-f(1, 2, 3, 4, 5);
+function* f() {
+  return function.s\u0065nt;
+}
+for (var i of f()) print(i);