Checker loses the Array subclass element type for a union of canonical string keys #3623

class Child<T> extends Array<T> {}
function read(child: Child<number>, key: '0' | '1') {
    const wrong: string = child[key];
}

TypeScript 6.0.3 with --ignoreConfig --strict --target ES2022 --noEmit reports TS2322 on wrong because both keys address numeric elements. SharpTS accepts the assignment with --no-tsconfig --strict --noEmit.

#3599 tracks a single canonical string key and also covers union receivers. This reproduction uses a union of keys and a single receiver.