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• I have searched for related issues and found none that match my proposal.
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Relevant Package

typescript-estree

My proposal is suitable for this project

• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Description

Continuing from #6404 (comment): we've been talking off-and-on for ages now about adding a thin layer of caching around TypeScript's type checking APIs.

do we want to do a weakmap memo on these? Eg

function memoize<TNode, TRet>(fn: (node: TNode) => TRet): (node: TNode) => TRet {
  const cache = new WeakMap<TNode, TRet>();

  return (node) => {
    const cachedRet = cache.get(node);
    if (cachedRet) {
      return cachedRet;
    }

    const newRet = fn(node);
    cachedRet = cache.set(node, newRet);
    return newRet;
  };
}

That would allow us to enforce that if two rules request the exact same node then we'll 100% use a fast path.

Doing a quick look at the implementation of getTypeAtLocation - it doesn't do any fast caching, so it does do a bunch of work.

IDK if this sort of thing would actually save any real time though - would be worth a test. Maybe we can file an issue to look at this later?

Additional Info

This'll require performance testing. Does it actually speed things up? Does it cause out-of-memory issues on our repo? Let's find out!

Strong candidate for including in the v6 betas. I'd like to get real world user testing to make sure this doesn't explode anybody.