[[DefineOwnProperty]]: Confusing note about redefinition always failing

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Documentation
Clarity
Mostly clear
Activity status
Stale
Tech stack
javascript
Domain
documentation

Research direction

Start with the proposal's [[DefineOwnProperty]] algorithm and the referenced ValidateAndApplyPropertyDescriptor steps in the Immutable ArrayBuffer specification. Compare the current note with the proposed mutable checks and value comparison. Done means the confusing note is replaced by consistent algorithm steps and the linked TypedArray behavior remains accurately specified.

Written by the indexing model from the issue text.

Description

This note in [[DefineOwnProperty]] caused confusion during code view:

NOTE: Attempting to redefine an immutable value always fails, even if the new value would be cast to the current value.

Maybe just inline ValidateAndApplyPropertyDescriptor and replace https://tc39.es/proposal-immutable-arraybuffer/#sec-typedarray-defineownproperty, steps 1.b.ii-viii with:

  1. Let mutable be true.
  2. If IsImmutableBuffer(O.[[ViewedArrayBuffer]]) is true, set mutable to false.
  3. If Desc has a [[Configurable]] field and Desc.[[Configurable]] is not mutable, return false.
  4. If Desc has an [[Enumerable]] field and Desc.[[Enumerable]] is false, return false.
  5. If IsAccessorDescriptor(Desc) is true, return false.
  6. If Desc has a [[Writable]] field and Desc.[[Writable]] is not mutable, return false.
  7. If Desc has a [[Value]] field, then
    1. If mutable is false, then
      1. Let current be TypedArrayGetElement(O, numericIndex).
      2. Assert: current is not undefined.
      3. Return SameValue(Desc.[[Value]], current).
    2. Perform ? TypedArraySetElement(O, numericIndex, Desc.[[Value]]).
  8. Return true.
Dominant language
JavaScript
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