[es7] Implement async functions parsing

test/mjsunit/harmony/async-await-functions.js

+// Copyright 2015 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: --harmony-async-await --allow-natives-syntax
+
+function TestAsyncFunctionParsing() {
+  async function a() {}
+  var b = async function() {};
+  var c = async function c() {};
+  function x() {
+    return async function() {};
+  }
+
+  assertEquals(String(a), 'async function a() {}');
+  assertEquals(String(b), 'async function () {}');
+  assertEquals(String(c), 'async function c() {}');
+  assertEquals(String(x()), 'async function () {}');
+
+  assertTrue(%FunctionIsAsync(a));
+  assertTrue(%FunctionIsAsync(b));
+  assertTrue(%FunctionIsAsync(c));
+  assertTrue(%FunctionIsAsync(x()));
+  assertFalse(%FunctionIsAsync(x));
+}
+TestAsyncFunctionParsing();
+
+
+function TestAsyncGeneratorError() {
+  assertThrows("async function* foo() {}", SyntaxError);
+}
+TestAsyncGeneratorError();
+
+
+function TestStrictModeAsyncFunctionParsing() {
+  'use strict';
+
+  async function a2() {}
+  var b2 = async function() {};
+
+  assertTrue(%FunctionIsAsync(a2));
+  assertTrue(%FunctionIsAsync(b2));
+}
+TestStrictModeAsyncFunctionParsing();
+
+
+function TestAsyncFunctionInFunction() {
+  function a() {
+    async function b() {}
+    async function c() {}
+    var d = async function() {}, e = async function() {};
+    return [a, b, async function() {}];
+  }
+
+  function* b() {
+    yield async function a() {};
+    yield async function b() {};
+    return async function c() {};
+  }
+
+  var g = b();
+  assertTrue(%FunctionIsAsync(g.next().value));
+  assertTrue(%FunctionIsAsync(g.next().value));
+  assertTrue(%FunctionIsAsync(g.next().value));
+}
+TestAsyncFunctionInFunction();
+
+
+function TestAsyncKeywordLineTerminator() {
+  // async identifier followed by a function
+  // keyword on the next line
+  var async = 10;
+  var b = async
+  function foo() {
+    return 15;
+  }
+
+  assertEquals(b, 10);
+  assertFalse(%FunctionIsAsync(foo));
+}
+TestAsyncKeywordLineTerminator();