Scanner: remove PushBack calls when we're going to return ILLEGAL.

test/cctest/test-parsing.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4235 matching lines @@
       "for(const x = 4, y of [1,2,3]) {}",
       "for(const x = 1, y = 2 in []) {}",
       "for(const x,y in []) {}",
       "for(const x = 1, y = 2 of []) {}",
       "for(const x,y of []) {}",
       NULL};
   static const ParserFlag always_flags[] = {kAllowHarmonyScoping};
   RunParserSyncTest(context_data, data, kError, NULL, 0, always_flags,
                     arraysize(always_flags));
 }
+
+
+TEST(InvalidUnicodeEscapes) {
+  const char* context_data[][2] = {{"", ""},
+                                   {"'use strict';", ""},
+                                   {NULL, NULL}};
+  const char* data[] = {
+    "var foob\\u123r = 0;",
+    "var \\u123roo = 0;",
+    "\"foob\\u123rr\"",
+    "/regex/g\\u123r",
+    NULL};
+  RunParserSyncTest(context_data, data, kError);
+}