[esnext] implement frontend changes for async/await proposal

test/cctest/test-parsing.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1490 matching lines @@
   data.Dispose();
   return i::MessageTemplate::FormatMessage(isolate, message, arg_object);
 }
 
 enum ParserFlag {
   kAllowLazy,
   kAllowNatives,
   kAllowHarmonyFunctionSent,
   kAllowHarmonyRestrictiveDeclarations,
   kAllowHarmonyExponentiationOperator,
-  kAllowHarmonyForIn
+  kAllowHarmonyForIn,
+  kAllowHarmonyAsyncAwait
 };
 
 enum ParserSyncTestResult {
   kSuccessOrError,
   kSuccess,
   kError
 };
 
 template <typename Traits>
 void SetParserFlags(i::ParserBase<Traits>* parser,
                     i::EnumSet<ParserFlag> flags) {
   parser->set_allow_lazy(flags.Contains(kAllowLazy));
   parser->set_allow_natives(flags.Contains(kAllowNatives));
   parser->set_allow_harmony_function_sent(
       flags.Contains(kAllowHarmonyFunctionSent));
   parser->set_allow_harmony_restrictive_declarations(
       flags.Contains(kAllowHarmonyRestrictiveDeclarations));
   parser->set_allow_harmony_exponentiation_operator(
       flags.Contains(kAllowHarmonyExponentiationOperator));
   parser->set_allow_harmony_for_in(flags.Contains(kAllowHarmonyForIn));
+  parser->set_allow_harmony_async_await(
+      flags.Contains(kAllowHarmonyAsyncAwait));
 }
 
 
 void TestParserSyncWithFlags(i::Handle<i::String> source,
                              i::EnumSet<ParserFlag> flags,
                              ParserSyncTestResult result,
                              bool is_module = false,
                              bool test_preparser = true) {
   i::Isolate* isolate = CcTest::i_isolate();
   i::Factory* factory = isolate->factory();
@@ skipping 5892 matching lines @@
     NULL
   };
   // clang-format on
 
   static const ParserFlag always_flags[] = {
       kAllowHarmonyExponentiationOperator};
   RunParserSyncTest(context_data, error_data, kError, NULL, 0, always_flags,
                     arraysize(always_flags));
 }
 
+TEST(AsyncAwait) {
+  // clang-format off
+  const char* context_data[][2] = {
+    { "'use strict';", "" },
+    { "", "" },
+    { NULL, NULL }
+  };
+
+  const char* data[] = {
+    "var asyncFn = async function() { await 1; };",
+    "var asyncFn = async function withName() { await 1; };",
+    "var asyncFn = async () => await 'test';",
+    "var asyncFn = async x => await x + 'test';",
+    "async function asyncFn() { await 1; }",
+    "var O = { async method() { await 1; } }",
+    "var O = { async ['meth' + 'od']() { await 1; } }",
+    "var O = { async 'method'() { await 1; } }",
+    "var O = { async 0() { await 1; } }",

[Dan Ehrenberg, 2016/05/05 01:14:40]

Maybe some tests which check that
- async is a contextual keyword and can be used as a normal variable, including
inside an async function
- await is completely usable as an identifier outside of an async function,
e.g., 'async function await() {}' is legal (when not enclosed in another async
function).
- A non-async function inside of an async function regains the ability to use
await as an identifier

[caitp (gmail), 2016/05/05 01:36:57]

Acknowledged --- Sounds good.

+    NULL
+  };
+  // clang-format on
+
+  static const ParserFlag always_flags[] = {kAllowHarmonyAsyncAwait};
+  RunParserSyncTest(context_data, data, kSuccess, NULL, 0, always_flags,
+                    arraysize(always_flags));
+}
+
+TEST(AsyncAwaitErrors) {
+  // clang-format off
+  const char* context_data[][2] = {
+    { "'use strict';", "" },
+    { "", "" },
+    { NULL, NULL }
+  };
+
+  const char* strict_context_data[][2] = {
+    { "'use strict';", "" },
+    { NULL, NULL }
+  };
+
+  const char* error_data[] = {
+    "var asyncFn = async function() { var await = 1; };",
+    "var asyncFn = async function() { var { await } = 1; };",
+    "var asyncFn = async function() { var [ await ] = 1; };",
+    "var asyncFn = async function await() {};",
+    "var asyncFn = async () => var await = 'test';",
+    "var asyncFn = async await => await + 'test';",
+    "var asyncFn = async function(await) {};",
+    "var asyncFn = async function() { return async (await) => {}; }",
+    "var asyncFn = async (await) => 'test';",
+    "var asyncFn = async x => { var await = 1; }",
+    "var asyncFn = async x => { var { await } = 1; }",
+    "var asyncFn = async x => { var [ await ] = 1; }",
+    "async function f(await) {}",
+    "async function f() { var await = 1; }",
+    "async function f() { var { await } = 1; }",
+    "async function f() { var [ await ] = 1; }",
+
+    "var O = { async method(a, a) {} }",
+    "var O = { async ['meth' + 'od'](a, a) {} }",
+    "var O = { async 'method'(a, a) {} }",
+    "var O = { async 0(a, a) {} }",
+
+    "async function f() { var O = { async [await](a, a) {} } }",

[Dan Ehrenberg, 2016/05/05 01:14:40]

- async generators and constructors are a syntax error.
- await; is a syntax error inside an async function (unlike yield)
- await as an identifier is disallowed in computed property names in class
declarations inside async functions
- async (x = await y) => z, and async function (x = await y) { } -- await is
banned in formal parameters not based on banning the identifier but based on
parsing only AwaitExpressions and banning those.

[caitp (gmail), 2016/05/05 21:49:36]

Added a bunch of these

+    NULL
+  };
+
+  const char* strict_error_data[] = {
+    "var O = { async method(eval) {} }",
+    "var O = { async ['meth' + 'od'](eval) {} }",
+    "var O = { async 'method'(eval) {} }",
+    "var O = { async 0(eval) {} }",
+
+    "var O = { async method(arguments) {} }",
+    "var O = { async ['meth' + 'od'](arguments) {} }",
+    "var O = { async 'method'(arguments) {} }",
+    "var O = { async 0(arguments) {} }",

[Dan Ehrenberg, 2016/05/05 01:14:40]

- async(a, a) => a (For this one in particular, I'm not sure if the code handles
it. Ditto other things that are banned in strict mode parameters of arrow
functions.)

[caitp (gmail), 2016/05/05 21:49:36]

Duplicate parameters in async arrow functions behave like regular arrow
functions --- they throw in Parser, but not in the PreParser (this is a
long-standing TODO of Andy's, I believe). We probably can't fix this in a
trivial patch without killing performance, which nobody wants to do.

I've added tests for these, but they're temporarily commented out with a TODO
(though I'm fairly sure async methods will behave correctly).

+    NULL
+  };
+  // clang-format on
+
+  static const ParserFlag always_flags[] = {kAllowHarmonyAsyncAwait};
+  RunParserSyncTest(context_data, error_data, kError, NULL, 0, always_flags,
+                    arraysize(always_flags));
+  RunParserSyncTest(strict_context_data, strict_error_data, kError, NULL, 0,
+                    always_flags, arraysize(always_flags));
+}
+
 TEST(RestrictiveForInErrors) {
   // clang-format off
   const char* context_data[][2] = {
     { "'use strict'", "" },
     { "", "" },
     { NULL, NULL }
   };
   const char* error_data[] = {
     "for (var x = 0 in {});",
     "for (const x = 0 in {});",
     "for (let x = 0 in {});",
     NULL
   };
   // clang-format on
 
   static const ParserFlag always_flags[] = {kAllowHarmonyForIn};
   RunParserSyncTest(context_data, error_data, kError, nullptr, 0, always_flags,
                     arraysize(always_flags));
 }