TypedArrays: type thisArg correctly and other issues

[NaridaL]

For example, UInt8Array.find

// currently:
find(
 predicate: (value: number, index: number, obj: Array<number>) => boolean, 
 thisArg?: any): number | undefined;
// better:
find<Z = undefined>(
 predicate: (this: Z, value: number, index: number, obj: this) => boolean,
 thisArg?: Z): number | undefined;

All the variants have the same issues. It seems like it would be a good idea to refactor them to:

interface TypedArray<ArrType> {
// find etc
}
interface UInt8Array extends TypedArray<UInt8Array> {}
interface UInt16Array extends TypedArray<UInt16Array> {}
// etc

[mhegazy]

We have explicitly removed the this types from arrays in #16223 #18116. you can still add the overloads locally if you so chose.

[NaridaL]

OK. Note that the callback parameter obj is currently wrong, it's Array<number>, when it should be this.

Would the refactoring with TypedArray help from a performance standpoint?

[mhegazy]

I do not think you need this, you jsut need Int32Array or Int64Array, etc.. a PR would be appreciated.

[NaridaL]

this would be more accurate in the unlikely case that you subclass a typed array.

[mhegazy]

yes, but will turn all these types into generic types. this costs more in terms of memory and in execution. and since this is the standard library everyone pays for the cost even if they never subclass typed arrays.