Add test case for BigInt in LiteralPropertyName

test/language/expressions/object/literal-property-name-bigint.js

@@ -0,0 +1,18 @@
+// Copyright (C) 2019 Toru Nagashima. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+description: >
+    BigInt in LiteralPropertyName must be valid and the property name must be
+    the string representation of the numeric value.
+esid: sec-object-initializer-runtime-semantics-evaluation
+info: |
+    LiteralPropertyName: NumericLiteral
+        1. Let _nbr_ be the NumericValue of |NumericLiteral|.
+        1. Return ! ToString(_nbr_).
+features: [BigInt]
+---*/
+
+var obj = { 999999999999999999n: true };
+
+assert.sameValue(obj["999999999999999999"], true,
+    "the property name must be the string representation of the numeric value.");