test: adding async optional chaining tests (#2337)

* test: adding async optional chaining tests

* Update test/language/expressions/optional-chaining/member-expression-async-identifier.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/optional-chain-async-square-brackets.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/member-expression-async-this.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/optional-chain-async-optional-chain-square-brackets.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/optional-chain-async-optional-chain-square-brackets.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/optional-chain-async-square-brackets.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/optional-chain-async-square-brackets.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/optional-chain-async-optional-chain-square-brackets.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* Update test/language/expressions/optional-chaining/member-expression-async-identifier.js

Co-Authored-By: Leo Balter <leonardo.balter@gmail.com>

* chore: update tests based on code review

* chore: address code review

test/language/expressions/optional-chaining/member-expression-async-identifier.js

@@ -0,0 +1,32 @@
+// Copyright 2019 Google, Inc.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: prod-OptionalExpression
+description: >
+  optional chain on member expression in async context
+info: |
+  Left-Hand-Side Expressions
+    OptionalExpression
+      MemberExpression [PrimaryExpression identifier] OptionalChain
+features: [optional-chaining]
+flags: [async]
+---*/
+
+const a = undefined;
+const c = {d: Promise.resolve(11)};
+async function checkAssertions() {
+  assert.sameValue(await a?.b, undefined);
+  assert.sameValue(await c?.d, 11);
+  
+  Promise.prototype.x = 42;
+  var res = await Promise.resolve(undefined)?.x;
+  assert.sameValue(res, 42, 'await unwraps the evaluation of the whole optional chaining expression #1');
+
+  Promise.prototype.y = 43;
+  var res = await Promise.reject(undefined)?.y;
+  assert.sameValue(res, 43, 'await unwraps the evaluation of the whole optional chaining expression #2');
+  
+  c.e = Promise.resolve(39);
+  assert.sameValue(await c?.e, 39, 'await unwraps the promise given after the evaluation of the OCE');
+}
+checkAssertions().then($DONE, $DONE);

test/language/expressions/optional-chaining/member-expression-async-literal.js

@@ -0,0 +1,19 @@
+// Copyright 2019 Google, Inc.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: prod-OptionalExpression
+description: >
+  optional chain on member expression in async context
+info: |
+  Left-Hand-Side Expressions
+    OptionalExpression:
+      MemberExpression [PrimaryExpression literal] OptionalChain
+features: [optional-chaining]
+flags: [async]
+---*/
+
+async function checkAssertions() {
+  assert.sameValue(await "hello"?.[0], 'h');
+  assert.sameValue(await null?.a, undefined);
+}
+checkAssertions().then($DONE, $DONE);

test/language/expressions/optional-chaining/member-expression-async-this.js

@@ -0,0 +1,20 @@
+// Copyright 2019 Google, Inc.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: prod-OptionalExpression
+description: >
+  optional chain on member expression in async context
+info: |
+  Left-Hand-Side Expressions
+    OptionalExpression:
+      MemberExpression [PrimaryExpression this] OptionalChain
+features: [optional-chaining]
+flags: [async]
+---*/
+
+async function thisFn() {
+  return await this?.a
+}
+thisFn.call({a: Promise.resolve(33)}).then(function(arg) {
+  assert.sameValue(33, arg);
+}).then($DONE, $DONE);

test/language/expressions/optional-chaining/optional-chain-async-optional-chain-square-brackets.js

@@ -0,0 +1,28 @@
+// Copyright 2019 Google, Inc.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: prod-OptionalExpression
+description: >
+  optional chain expansions in an async context
+info: |
+  Left-Hand-Side Expressions
+    OptionalExpression
+      MemberExpression [PrimaryExpression Identifier] OptionalChain
+        OptionalChain OptionalChain ?.[Expression]
+features: [optional-chaining]
+flags: [async]
+---*/
+
+async function checkAssertions() {
+  assert.sameValue(await {a: [11]}?.a[0], 11);
+  const b = {c: [22, 33]};
+  assert.sameValue(b?.c[await Promise.resolve(1)], 33);
+  function e(val) {
+    return val;
+  }
+  assert.sameValue({d: e}?.d(await Promise.resolve([44, 55]))[1], 55);
+  assert.sameValue(undefined?.arr[
+    await Promise.reject(new Error('unreachable'))
+  ], undefined);
+}
+checkAssertions().then($DONE, $DONE);

test/language/expressions/optional-chaining/optional-chain-async-square-brackets.js

@@ -0,0 +1,24 @@
+// Copyright 2019 Google, Inc.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: prod-OptionalExpression
+description: >
+  optional chain expansions in an async context
+info: |
+  Left-Hand-Side Expressions
+    OptionalExpression
+      MemberExpression [PrimaryExpression Identifier] OptionalChain
+        OptionalChain ?.[Expression]
+features: [optional-chaining]
+flags: [async]
+---*/
+
+async function checkAssertions() {
+  assert.sameValue(await [11]?.[0], 11);
+  assert.sameValue([22, 33]?.[await Promise.resolve(1)], 33);
+  assert.sameValue([44, await Promise.resolve(55)]?.[1], 55);
+  assert.sameValue(undefined?.[
+    await Promise.reject(new Error('unreachable'))
+  ], undefined);
+}
+checkAssertions().then($DONE, $DONE);