[immutable-arraybuffer] TypedArray internal operations

[gibson042]

Ref #4509

%TypedArray% instance operations

• [[GetOwnProperty]]

  • property descriptors for in-bounds indexes of a typed array backed by an immutable ArrayBuffer are reported as writable false, enumerable true, configurable false

• [[DefineOwnProperty]]

  • attempts to redefine own properties for in-bounds indexes of a typed array backed by an immutable ArrayBuffer are validated against descriptors for immutable properties
    • presence of writable: true, enumerable: false, configurable: true, get, and/or set results in rejection
    • presence of value with any value that is not treated as identical to the current value by Object.is results in rejection (e.g., value: -0 and value: "0" are rejected when the current value is 0)
    • all other property descriptors (e.g., any subset of { writable: false, enumerable: true, configurable: false, value: $currentValue }) are accepted but do not result in observable changes

• [[Set]]

  • any attempt to set the value for a property whose name is a canonical numeric index string (including non-index values such as "-0", "1.5", "590295810358705700000", "5e-324", "1.7976931348623157e+308", "Infinity", and "NaN") on a typed array backed by an immutable ArrayBuffer is rejected, even if the new value is identical to the current value
  • likewise for attempts on a receiver having such a typed array in its prototype chain when the [[Set]] makes it to the typed array

Most of the changes just relax filters applied to testWithTypedArrayConstructors and similar harness/testTypedArray.js exports such that immutable ArrayBuffers are no longer excluded.

[iamstolis]

Note that verifyProperty() is based on various assumptions that don't work for typed arrays. For example, isWritable(new Uint8Array(8), "0") is false (incorrectly) and isWritable(new BigInt64Array(8), "0") even results in SyntaxError: Cannot convert unlikelyValue to a BigInt.

The current version of the test seems to be lucky to pass despite the usage of verifyProperty(), but it is probably better to avoid it (for typed arrays). Note that, for example, index-prop-desc.js that is kind of mutable version of this test avoids verifyProperty() for the mentioned reasons.

[gibson042]

I just fixed verifyProperty to work with TypedArray input.

[iamstolis]

Other tests in the same directory do not test BigInt typed arrays i.e. use testWithTypedArrayConstructors instead of testWithAllTypedArrayConstructors (and contain a variant with testWithBigIntTypedArrayConstructors in BigInt sub-directory).

[gibson042]

Right, in the long term I'll be removing the "bigint" sub-directories to make the testing more consolidated.

[ptomato]

Needs a non-trivial rebase.

[gibson042]

Needs a non-trivial rebase.

Done.