[parser] Make pattern DCHECK dependent on !has_error

Bug: chromium:926036
Change-Id: Ibc8d3ffc3f9411fa33c0ed6326cb6b19a7d8dd05
Reviewed-on: https://chromium-review.googlesource.com/c/1442635Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59162}

src/parsing/parser.cc

@@ -1853,7 +1853,7 @@ void Parser::DesugarBindingInForEachStatement(ForInfo* for_info,
       for_info->parsing_result.declarations[0];
   Variable* temp = NewTemporary(ast_value_factory()->dot_for_string());
   ScopedPtrList<Statement> each_initialization_statements(pointer_buffer());
-  DCHECK_NOT_NULL(decl.pattern);
+  DCHECK_IMPLIES(!has_error(), decl.pattern != nullptr);
   decl.initializer = factory()->NewVariableProxy(temp, for_info->position);
   InitializeVariables(&each_initialization_statements, NORMAL_VARIABLE, &decl);
 

test/mjsunit/regress/regress-926036.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.
+
+assertThrows("async() => { for await (var a ;;) {} }", SyntaxError);