BigInt stringify order of steps

test/built-ins/JSON/stringify/bigint-order.js

@@ -0,0 +1,42 @@
+// Copyright (C) 2017 Robin Templeton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: BigInt stringify order of steps
+esid: sec-serializejsonproperty
+info: >
+  Runtime Semantics: SerializeJSONProperty ( key, holder )
+
+  2. If Type(value) is Object or BigInt, then
+    a. Let toJSON be ? GetGetV(value, "toJSON").
+    b. If IsCallable(toJSON) is true, then
+      i. Set value to ? Call(toJSON, value, « key »).
+  3. If ReplacerFunction is not undefined, then
+    a. Set value to ? Call(ReplacerFunction, holder, « key, value »).
+  4. If Type(value) is Object, then
+    [...]
+    d. Else if value has a [[BigIntData]] internal slot, then
+      i. Set value to value.[[BigIntData]].
+  [...]
+  10. If Type(value) is BigInt, throw a TypeError exception
+features: [BigInt, arrow-function]
+---*/
+
+let step;
+
+function replacer(x, k, v)
+{
+  assert.sameValue(step++, 1);
+  assert.sameValue(v, 1n);
+  return x;
+}
+
+BigInt.prototype.toJSON = function () { assert.sameValue(step++, 0); return 1n; };
+
+step = 0;
+assert.throws(TypeError, () => JSON.stringify(0n, (k, v) => replacer(2n, k, v)));
+assert.sameValue(step, 2);
+
+step = 0;
+assert.throws(TypeError, () => JSON.stringify(0n, (k, v) => replacer(Object(2n), k, v)));
+assert.sameValue(step, 2);