From e5731d6fa786c3d551ecfa74becb7bc985178c07 Mon Sep 17 00:00:00 2001
From: Richard Gibson <richard.gibson@gmail.com>
Date: Mon, 28 Jul 2025 18:40:29 -0400
Subject: [PATCH] [TypedArray.prototype.copyWithin] Refactor
 coerced-target-start-end-shrink.js

---
 .../coerced-target-start-end-shrink.js        | 83 ++++++++-----------
 1 file changed, 35 insertions(+), 48 deletions(-)

diff --git a/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js b/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js
index 65270444ad..c58cd1d353 100644
--- a/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js
+++ b/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js
@@ -9,72 +9,59 @@ includes: [compareArray.js, resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
+const fillWithIndexes = (ta, length) => {
+  for (let i = 0; i < length; ++i) {
+    ta[i] = MayNeedBigInt(ta, i);
+  }
+  return ta;
+};
+
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
-  const evil = {
-    valueOf: () => {
-      rab.resize(2 * ctor.BYTES_PER_ELEMENT);
-      return 2;
-    }
+  const evil = () => {
+    rab.resize(2 * ctor.BYTES_PER_ELEMENT);
+    return 2;
   };
   assert.throws(TypeError, () => {
-    fixedLength.copyWithin(evil, 0, 1);
+    fixedLength.copyWithin({ valueOf: evil }, 0, 1, ctor.name + " evil target.");
   });
   rab.resize(4 * ctor.BYTES_PER_ELEMENT);
   assert.throws(TypeError, () => {
-    fixedLength.copyWithin(0, evil, 3);
+    fixedLength.copyWithin(0, { valueOf: evil }, 3, ctor.name + " evil start.");
   });
   rab.resize(4 * ctor.BYTES_PER_ELEMENT);
   assert.throws(TypeError, () => {
-    fixedLength.copyWithin(0, 1, evil);
+    fixedLength.copyWithin(0, 1, { valueOf: evil }, ctor.name + " evil end.");
   });
 }
+
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
-  const lengthTracking = new ctor(rab);
-  for (let i = 0; i < 4; ++i) {
-    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
-  }
-  // [0, 1, 2, 3]
-  //        ^
-  //        target
-  // ^
-  // start
-  const evil = {
-    valueOf: () => {
-      rab.resize(3 * ctor.BYTES_PER_ELEMENT);
-      return 2;
-    }
+  const lengthTracking = fillWithIndexes(new ctor(rab), 4);
+  // [0, 1, 2,] 3]
+  //        <=--> dest
+  //  <=-> src
+  const evil = () => {
+    rab.resize(3 * ctor.BYTES_PER_ELEMENT);
+    return 2;
   };
-  lengthTracking.copyWithin(evil, 0);
-  assert.compareArray(ToNumbers(lengthTracking), [
-    0,
-    1,
-    0
-  ]);
+  lengthTracking.copyWithin({ valueOf: evil }, 0);
+  assert.compareArray(ToNumbers(lengthTracking), [0, 1, 0],
+    ctor.name + " truncated copy forward.");
 }
+
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
-  const lengthTracking = new ctor(rab);
-  for (let i = 0; i < 4; ++i) {
-    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
-  }
-  // [0, 1, 2, 3]
-  //        ^
-  //        start
-  // ^
-  // target
-  const evil = {
-    valueOf: () => {
-      rab.resize(3 * ctor.BYTES_PER_ELEMENT);
-      return 2;
-    }
+  const lengthTracking = fillWithIndexes(new ctor(rab), 4);
+  // [0, 1, 2,] 3]
+  //        <=--> src
+  //  <=-> dest
+  const evil = () => {
+    rab.resize(3 * ctor.BYTES_PER_ELEMENT);
+    return 2;
   };
-  lengthTracking.copyWithin(0, evil);
-  assert.compareArray(ToNumbers(lengthTracking), [
-    2,
-    1,
-    2
-  ]);
+  lengthTracking.copyWithin(0, { valueOf: evil });
+  assert.compareArray(ToNumbers(lengthTracking), [2, 1, 2],
+    ctor.name + " truncated copy backward.");
 }