[JS:Engine] Implement the Optional Chaining operator (?.)

1 files changed, 29 insertions, 0 deletions

diff --git a/js/src/tests/test262/language/optional-chaining/optional-call-preserves-this.js b/js/src/tests/test262/language/optional-chaining/optional-call-preserves-this.js
new file mode 100644
index 000000000..dbaf92c3b
--- /dev/null
+++ b/js/src/tests/test262/language/optional-chaining/optional-call-preserves-this.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2019 Sony Interactive Entertainment Inc. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-optional-chaining-chain-evaluation
+description: >
+  optional call must preserve this context, as with a non-optional call
+info: |
+  OptionalChain : ?. Arguments
+    1. Let thisChain be this OptionalChain.
+    2. Let tailCall be IsInTailPosition(thisChain).
+    3. Return ? EvaluateCall(baseValue, baseReference, Arguments, tailCall).
+features: [optional-chaining]
+---*/
+
+const a = {
+    b() { return this._b; },
+    _b: { c: 42 }
+};
+
+assert.sameValue(a?.b().c, 42);
+assert.sameValue((a?.b)().c, 42);
+
+assert.sameValue(a.b?.().c, 42);
+assert.sameValue((a.b)?.().c, 42);
+
+assert.sameValue(a?.b?.().c, 42);
+assert.sameValue((a?.b)?.().c, 42);
+
+reportCompare(0, 0);