Test "length" [[Value]] coercion order in ArraySetLength

test/built-ins/Array/length/define-own-prop-length-coercion-order-set.js

@@ -0,0 +1,43 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: André Bargull
+esid: sec-arraysetlength
+description: >
+  [[Value]] is coerced to number before current descriptor's [[Writable]] check.
+info: |
+  ArraySetLength ( A, Desc )
+
+  [...]
+  3. Let newLen be ? ToUint32(Desc.[[Value]]).
+  4. Let numberLen be ? ToNumber(Desc.[[Value]]).
+  [...]
+  7. Let oldLenDesc be OrdinaryGetOwnProperty(A, "length").
+  [...]
+  12. If oldLenDesc.[[Writable]] is false, return false.
+features: [Symbol, Symbol.toPrimitive, Reflect, Reflect.set]
+includes: [compareArray.js]
+---*/
+
+var array = [1, 2, 3];
+var hints = [];
+var length = {};
+length[Symbol.toPrimitive] = function(hint) {
+  hints.push(hint);
+  Object.defineProperty(array, "length", {writable: false});
+  return 0;
+};
+
+assert.throws(TypeError, function() {
+  "use strict";
+  array.length = length;
+});
+assert.compareArray(hints, ["number", "number"]);
+
+
+array = [1, 2, 3];
+hints = [];
+
+assert(!Reflect.set(array, "length", length));
+assert.compareArray(hints, ["number", "number"]);

test/built-ins/Array/length/define-own-prop-length-coercion-order.js

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+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: André Bargull
+esid: sec-arraysetlength
+description: >
+  [[Value]] is coerced to number before descriptor validation.
+info: |
+  ArraySetLength ( A, Desc )
+
+  [...]
+  3. Let newLen be ? ToUint32(Desc.[[Value]]).
+  4. Let numberLen be ? ToNumber(Desc.[[Value]]).
+  [...]
+  7. Let oldLenDesc be OrdinaryGetOwnProperty(A, "length").
+  [...]
+  11. If newLen ≥ oldLen, then
+    a. Return OrdinaryDefineOwnProperty(A, "length", newLenDesc).
+
+  OrdinaryDefineOwnProperty ( O, P, Desc )
+
+  [...]
+  3. Return ValidateAndApplyPropertyDescriptor(O, P, extensible, Desc, current).
+
+  ValidateAndApplyPropertyDescriptor ( O, P, extensible, Desc, current )
+
+  [...]
+  7. Else if IsDataDescriptor(current) and IsDataDescriptor(Desc) are both true, then
+    a. If current.[[Configurable]] is false and current.[[Writable]] is false, then
+      i. If Desc.[[Writable]] is present and Desc.[[Writable]] is true, return false.
+features: [Reflect]
+---*/
+
+var array = [1, 2];
+var valueOfCalls = 0;
+var length = {
+  valueOf: function() {
+    valueOfCalls += 1;
+    if (valueOfCalls !== 1) {
+      // skip first coercion at step 3
+      Object.defineProperty(array, "length", {writable: false});
+    }
+    return array.length;
+  },
+};
+
+assert.throws(TypeError, function() {
+  Object.defineProperty(array, "length", {value: length, writable: true});
+});
+assert.sameValue(valueOfCalls, 2);
+
+
+array = [1, 2];
+valueOfCalls = 0;
+
+assert(!Reflect.defineProperty(array, "length", {value: length, writable: true}));
+assert.sameValue(valueOfCalls, 2);