TypedArray.prototype.set needs non-trivial changes

[marjakh]

In SetTypedArrayFromArrayLike ( https://tc39.es/ecma262/#sec-settypedarrayfromarraylike ), step 15.b can resize the target buffer. Step 15.e. checks for IsDetachedBuffer(targetBuffer); this needs to turn into an "out of bounds" check.

But in addition, I think it should re-get the target buffer length and compare it to the index it's setting, since SetValueInBuffer which it calls doesn't do any checking.

To do this, we need to keep track of the target index, not only the byte index. -> These changes are non-trivial and should be part of this proposal.

[marjakh]

Clarification: This is only relevant in the case of length-tracking TAs which don't go out of bounds, so the TA won't be out of bounds but we'll still need to restrict the data we're setting.

[syg]

Steps 15.b, 15.c, and 15.d all can call user code, so, seems right. Will work on this today.

[ljharb]

Closed with #87. Also, the proposal has reached stage 4.