[scanner] fix bug with reporting invalid numeric separator

Bug: v8:9603
Change-Id: I7a36c97feedaccf81509aae579f1594a0e7b1019
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1743527Reviewed-by: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Commit-Queue: Joshua Litt <joshualitt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63129}

src/parsing/scanner.cc

@@ -635,6 +635,11 @@ bool Scanner::ScanDecimalDigits(bool allow_numeric_separator) {
   while (IsDecimalDigit(c0_)) {
     AddLiteralCharAdvance();
   }
+  if (c0_ == '_') {
+    ReportScannerError(Location(source_pos(), source_pos() + 1),
+                       MessageTemplate::kInvalidOrUnexpectedToken);
+    return false;
+  }
   return true;
 }
 

test/message/regress/fail/regress-9603.js

+// Copyright 2019 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+let x = 09_9.0;

test/message/regress/fail/regress-9603.out

+# Copyright 2019 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+*%(basename)s:5: SyntaxError: Invalid or unexpected token
+let x = 09_9.0;
+          ^
+SyntaxError: Invalid or unexpected token