[parser] Fix parse errors for async arrow function edge cases

New test262 tests bring up a couple cases with async arrow functions
that V8 didn't seem to handle properly; this patch makes those cases
errors:
- async (...x,) => y -- Rest parameter must be last formal parameter
- async (...x = z) => y -- No default value for rest parameter
- async (...x, y) => z -- Rest parameter must be last formal parameter

Bug: v8:4483, v8:5051
Change-Id: I024d9ba0c854e8e5e75283df2ee53127b1be090d
Reviewed-on: https://chromium-review.googlesource.com/496057
Commit-Queue: Daniel Ehrenberg <littledan@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Caitlin Potter <caitp@igalia.com>
Cr-Commit-Position: refs/heads/master@{#45116}

src/messages.h

@@ -608,6 +608,8 @@ class ErrorUtils : public AllStatic {
   T(ArgStringTerminatesParametersEarly,                                        \
     "Arg string terminates parameters early")                                  \
   T(UnexpectedEndOfArgString, "Unexpected end of arg string")                  \
+  T(RestDefaultInitializer,                                                    \
+    "Rest parameter may not have a default initializer")                       \
   T(RuntimeWrongNumArgs, "Runtime function given wrong number of arguments")   \
   T(SuperNotCalled,                                                            \
     "Must call super constructor in derived class before accessing 'this' or " \

src/parsing/parser-base.h

@@ -1972,6 +1972,11 @@ ParserBase<Impl>::ParseExpressionCoverGrammar(bool accept_IN, bool* ok) {
       int ellipsis_pos = position();
       int pattern_pos = peek_position();
       ExpressionT pattern = ParsePrimaryExpression(CHECK_OK);
+      if (peek() == Token::ASSIGN) {
+        ReportMessage(MessageTemplate::kRestDefaultInitializer);
+        *ok = false;
+        return result;
+      }
       ValidateBindingPattern(CHECK_OK);
       right = factory()->NewSpread(pattern, ellipsis_pos, pattern_pos);
     } else {
@@ -2715,6 +2720,10 @@ typename ParserBase<Impl>::ExpressionListT ParserBase<Impl>::ParseArguments(
         spread_arg.beg_pos = start_pos;
         spread_arg.end_pos = peek_position();
       }
+      if (argument->IsAssignment()) {
+        classifier()->RecordAsyncArrowFormalParametersError(
+            scanner()->location(), MessageTemplate::kRestDefaultInitializer);
+      }
       argument = factory()->NewSpread(argument, start_pos, expr_pos);
     }
     result->Add(argument, zone_);
@@ -2727,6 +2736,10 @@ typename ParserBase<Impl>::ExpressionListT ParserBase<Impl>::ParseArguments(
     done = (peek() != Token::COMMA);
     if (!done) {
       Next();
+      if (argument->IsSpread()) {
+        classifier()->RecordAsyncArrowFormalParametersError(
+            scanner()->location(), MessageTemplate::kParamAfterRest);
+      }
       if (allow_harmony_trailing_commas() && peek() == Token::RPAREN) {
         // allow trailing comma
         done = true;
@@ -3657,7 +3670,12 @@ void ParserBase<Impl>::ParseFormalParameter(FormalParametersT* parameters,
   }
 
   ExpressionT initializer = impl()->EmptyExpression();
-  if (!is_rest && Check(Token::ASSIGN)) {
+  if (Check(Token::ASSIGN)) {
+    if (is_rest) {
+      ReportMessage(MessageTemplate::kRestDefaultInitializer);
+      *ok = false;
+      return;
+    }
     ExpressionClassifier init_classifier(this);
     initializer = ParseAssignmentExpression(true, CHECK_OK_CUSTOM(Void));
     impl()->RewriteNonPattern(CHECK_OK_CUSTOM(Void));

test/cctest/test-parsing.cc

@@ -4262,6 +4262,7 @@ TEST(ErrorsArrowFunctions) {
     "(c, a.b) => {}",
     "(a['b'], c) => {}",
     "(c, a['b']) => {}",
+    "(...a = b) => b",
 
     // crbug.com/582626
     "(...rest - a) => b",
@@ -8989,6 +8990,10 @@ TEST(AsyncAwaitErrors) {
     // v8:5148 assert that errors are still thrown for calls that may have been
     // async functions
     "async({ foo33 = 1 })",
+
+    "async(...a = b) => b",
+    "async(...a,) => b",
+    "async(...a, b) => b",
     NULL
   };
 

test/message/arrow-invalid-rest-2.out

-*%(basename)s:7: SyntaxError: Unexpected token =
+*%(basename)s:7: SyntaxError: Rest parameter may not have a default initializer
 var f = (a, ...x = 10) => x;
-                 ^
-SyntaxError: Unexpected token =
+               ^
+SyntaxError: Rest parameter may not have a default initializer

test/message/arrow-invalid-rest.out

-*%(basename)s:7: SyntaxError: Unexpected token =
+*%(basename)s:7: SyntaxError: Rest parameter may not have a default initializer
 var f = (...x = 10) => x;
-              ^
-SyntaxError: Unexpected token =
+            ^
+SyntaxError: Rest parameter may not have a default initializer

test/message/async-arrow-invalid-rest-2.js

+// Copyright 2016 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.
+//
+//
+
+var f = async (a, ...x = 10) => x;
+f(1, 2, 3, 4, 5);

test/message/async-arrow-invalid-rest-2.out

+*%(basename)s:7: SyntaxError: Rest parameter may not have a default initializer
+var f = async (a, ...x = 10) => x;
+                         ^^
+SyntaxError: Rest parameter may not have a default initializer

test/message/async-arrow-invalid-rest.js

+// Copyright 2016 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.
+//
+//
+
+var f = async (...x = 10) => x;
+f(1, 2, 3, 4, 5);

test/message/async-arrow-invalid-rest.out

+*%(basename)s:7: SyntaxError: Rest parameter may not have a default initializer
+var f = async (...x = 10) => x;
+                      ^^
+SyntaxError: Rest parameter may not have a default initializer

test/message/async-arrow-param-after-rest.js

+// Copyright 2017 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.
+//
+//
+
+async (...x, y) => 10

test/message/async-arrow-param-after-rest.out

+*%(basename)s:7: SyntaxError: Rest parameter must be last formal parameter
+async (...x, y) => 10
+           ^
+SyntaxError: Rest parameter must be last formal parameter
+

test/message/function-param-after-rest.js

+// Copyright 2017 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.
+//
+//
+
+function f(...x, y) { }

test/message/function-param-after-rest.out

+*%(basename)s:7: SyntaxError: Rest parameter must be last formal parameter
+function f(...x, y) { }
+               ^
+SyntaxError: Rest parameter must be last formal parameter
+