[immutable-arraybuffer] ArrayBuffer.prototype.sliceToImmutable

[gibson042]

Ref #4509

New ArrayBuffer.prototype properties

• ArrayBuffer.prototype.sliceToImmutable
  • verifyPrimordialCallableProperty(ArrayBuffer.prototype, "sliceToImmutable", "sliceToImmutable", 2);
  • brand-checking (throws TypeError unless receiver is an ArrayBuffer and not a SharedArrayBuffer), before resolving bounds
  • throws TypeError if receiver is detached, before resolving bounds
  • resolves bounds after passing the preceding checks—first start, clamping negative values to [0, len - 1] and positive values to [0, len], then end, defaulting to len and clamping negative values to [0, len - 1] and positive values to [0, len] (and capturing len before coercing either start or end)
  • throws TypeError if receiver was detached by bounds resolution, after bounds resolution
  • throws RangeError if length < specified upper bound, after passing the second detachment check and even if length was ≥ specified upper bound until bounds resolution
  • returns an immutable ArrayBuffer with the correct length and contents (both unaffected by subsequent changes to the original receiver, including detachment)

[ptomato]

Minor comments, feel free to merge when resolved

[ptomato]

Suggested change

assert.sameValue(typeof fn, "function", "Method must exist.");

I think this is sufficiently implied by the immutable-arraybuffer feature flag.

[ptomato]

Ditto

[ptomato]

This will break on implementations without Symbol or BigInt, I think you probably want if (!badReceivers[i]) continue;

[ptomato]

Already implied by feature flag.

[ptomato]

Minor suggestion, add something to these assertion messages to distinguish which assertion is failing (byte length, contents, or immutability) (Same for below)