Make a "shortcut" API around TypeScript for node types

[JoshuaKGoldberg]

Discussed in #6013

^{Originally posted by JoshuaKGoldberg November 7, 2022}

Suggestion

We write code like this very frequently:

const parserServices = util.getParserServices(context);
const checker = parserServices.program.getTypeChecker();
const tsNode = parserServices.esTreeNodeToTSNodeMap.get(node);
const type = checker.getTypeAtLocation(node);

It's a little burdensome.

@bradzacher and I were chatting in a pairing about how it might be convenient to make a wrapper around this, for convenience. Vague first draft:

declare const typeUtils: {
  [K in keyof ts.TypeChecker]:
    (services: ParserServices, node: TSESTree.Node) => ReturnType<ts.TypeChecker[K]>;
};

const type = typeUtils.getTypeAtLocation(parserServices, node);

We'd probably want to export this as a publicly available & documented API, so it's not confusing to consumers why our source code doesn't look like examples.

One downside would be that we're obfuscating how to use TypeScript APIs. I hate to add to complexity of understanding these already hard-to-understand things...

---

We ended up with #6013 (comment): putting the types right on the parser services.

I would say we could probably go one step further and just offer all of this off of the parser serivces!

For example:

type ParserServices = {
  getTypeAtLocation(node: TSESTree.Node): ReturnType<ts.TypeChecker['getTypeAtLocation']>;
};

const parserServices = util.getParserServices(context);

parserServices.getTypeAtLocation(node);

That would make it even more straight-forward for people to use the tooling!

[JoshuaKGoldberg]

Merged in #6404. This'll be part of the v6 release.