Add Symbol.isConcatSpreadable get order test

test/built-ins/Array/prototype/concat/is-concat-spreadable-get-order.js

@@ -0,0 +1,65 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-array.prototype.concat
+description: >
+  Symbol.isConcatSpreadable should be looked up once for `this value` and
+  once for each argument, after ArraySpeciesCreate routine.
+info: |
+  Array.prototype.concat ( ...arguments )
+
+  1. Let O be ? ToObject(this value).
+  2. Let A be ? ArraySpeciesCreate(O, 0).
+  [...]
+  5. Repeat, while items is not empty
+    a. Remove the first element from items and let E be the value of the element.
+    b. Let spreadable be ? IsConcatSpreadable(E).
+    [...]
+
+  ArraySpeciesCreate ( originalArray, length )
+
+  [...]
+  5. Let C be ? Get(originalArray, "constructor").
+  [...]
+
+  Runtime Semantics: IsConcatSpreadable ( O )
+
+  1. If Type(O) is not Object, return false.
+  2. Let spreadable be ? Get(O, @@isConcatSpreadable).
+  [...]
+includes: [compareArray.js]
+features: [Symbol.isConcatSpreadable]
+---*/
+
+var calls = [];
+var descConstructor = {
+  get: function() {
+    calls.push("constructor");
+    return Array;
+  },
+  configurable: true,
+};
+var descSpreadable = {
+  get: function() {
+    calls.push("isConcatSpreadable");
+  },
+  configurable: true,
+};
+
+var arr1 = [];
+Object.defineProperty(arr1, "constructor", descConstructor);
+Object.defineProperty(arr1, Symbol.isConcatSpreadable, descSpreadable);
+
+assert.compareArray(arr1.concat(1), [1]);
+assert.compareArray(calls, ["constructor", "isConcatSpreadable"]);
+
+calls = [];
+
+var arr2 = [];
+var arg = {};
+Object.defineProperty(arr2, "constructor", descConstructor);
+Object.defineProperty(arg, Symbol.isConcatSpreadable, descSpreadable);
+
+assert.compareArray(arr2.concat(arg), [arg]);
+assert.compareArray(calls, ["constructor", "isConcatSpreadable"]);