[esnext] implement frontend changes for async/await proposal

test/cctest/test-parsing.cc

Index: test/cctest/test-parsing.cc
diff --git a/test/cctest/test-parsing.cc b/test/cctest/test-parsing.cc
index 5095710a67b84df2b27a79737537965b664206c2..37d0062c51aad054c53a412a3ef17d5704ac3a65 100644
--- a/test/cctest/test-parsing.cc
+++ b/test/cctest/test-parsing.cc
@@ -1508,7 +1508,8 @@ enum ParserFlag {
   kAllowHarmonyFunctionSent,
   kAllowHarmonyRestrictiveDeclarations,
   kAllowHarmonyExponentiationOperator,
-  kAllowHarmonyForIn
+  kAllowHarmonyForIn,
+  kAllowHarmonyAsyncAwait
 };
 
 enum ParserSyncTestResult {
@@ -1529,6 +1530,8 @@ void SetParserFlags(i::ParserBase<Traits>* parser,
   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));
 }
 
 
@@ -7441,6 +7444,94 @@ TEST(ExponentiationOperatorErrors) {
                     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] = {