[parser] Fix: disallow "export default ()".

BUG=chromium:797581

Change-Id: I08f880a907f122480a014763975ecc07e2c49f7d
Reviewed-on: https://chromium-review.googlesource.com/856937Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50471}

src/parsing/parser.cc

@@ -1299,6 +1299,7 @@ Statement* Parser::ParseExportDefault(bool* ok) {
       int pos = position();
       ExpressionClassifier classifier(this);
       Expression* value = ParseAssignmentExpression(true, CHECK_OK);
+      ValidateExpression(CHECK_OK);
       SetFunctionName(value, ast_value_factory()->default_string());
 
       const AstRawString* local_name =

test/mjsunit/mjsunit.status

@@ -31,6 +31,7 @@
   # tested standalone.
   'modules-skip*': [SKIP],
   'harmony/modules-skip*': [SKIP],
+  'regress/modules-skip*': [SKIP],
 
   # All tests in the bug directory are expected to fail.
   'bugs/*': [FAIL],

test/mjsunit/regress/modules-skip-regress-797581-1.js

+// Copyright 2018 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.
+
+export default ()

test/mjsunit/regress/modules-skip-regress-797581-2.js

+// Copyright 2018 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.
+
+export default (...)

test/mjsunit/regress/modules-skip-regress-797581-3.js

+// Copyright 2018 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.
+
+export default (a, ...b)

test/mjsunit/regress/modules-skip-regress-797581-4.js

+// Copyright 2018 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.
+
+export default 1, 2;

test/mjsunit/regress/modules-skip-regress-797581-5.js

+// Copyright 2018 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;
+export default x = 0;

test/mjsunit/regress/regress-797581.js

+// Copyright 2018 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.
+
+// Flags: --allow-natives-syntax --harmony-dynamic-import
+
+function TryToLoadModule(filename, expect_error, token) {
+  let caught_error;
+
+  function SetError(e) {
+    caught_error = e;
+  }
+
+  import(filename).catch(SetError);
+  %RunMicrotasks();
+
+  if (expect_error) {
+    assertTrue(caught_error instanceof SyntaxError);
+    assertEquals("Unexpected token " + token, caught_error.message);
+  } else {
+    assertEquals(undefined, caught_error);
+  }
+}
+
+TryToLoadModule("modules-skip-regress-797581-1.js", true, ")");
+TryToLoadModule("modules-skip-regress-797581-2.js", true, ")");
+TryToLoadModule("modules-skip-regress-797581-3.js", true, "...");
+TryToLoadModule("modules-skip-regress-797581-4.js", true, ",");
+TryToLoadModule("modules-skip-regress-797581-5.js", false);