querySelector return type could be more specific for single-element selectors

[jelbourn]

The return types for querySelector and querySelectorAll (in the lib.es6.d.ts) could provide more specific return type information when the selector a single element selector for a known element type.

I.e., right now the types are

interface NodeSelector {
    querySelector(selectors: string): Element;
    querySelectorAll(selectors: string): NodeListOf<Element>;
}

But it could be expanded in the style of getElementsByTagName:

interface NodeSelector {
    querySelector(selectors: "a"): HTMLAnchorElement;
    querySelector(selectors: "abbr"): HTMLPhraseElement;
    ...
    querySelector(selectors: string): Element;
}

It's a minor convenience, but does eliminate the occasional typecast.

[DanielRosenwasser]

I don't think this is totally unreasonable. @mhegazy @zhengbli any thoughts on this?

[mhegazy]

PRs welcomed. here is some instructions on submitting lib.d.ts PRs: https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md#contributing-libdts-fixes

[thw0rted]

I'm a vanilla Javascript user but I benefit from this in VS Intellisense. So, I don't know TS well enough to answer my question: would it be possible to implement this with regex or partial-string matching, such that querySelector("a.someClass") also returns a more specific class (i.e. HTMLAnchorElement)? It's the same operating theory, right? I don't think it's possible for querySelector to return a non-Anchor for the selector example I gave, is it?

[kitsonk]

Pattern matching of overloads is #165 and it being applied to querySelector() would be different than this closed issue, which has been resolved.

[thw0rted]

OK, I think that fills in the blanks of the Typescript syntax I was missing. I asked on StackOverflow about good ways to handle this in the short term, and I'm happy enough with the answer, but returning a more specific type (eventually) would make for better code.