[Feature]: support type inference for function parameters

[eyalroth]

🚀 Feature Proposal

This is identical to #13267, which was implemented in https://github.com/jestjs/jest/releases/tag/v29.1.0 (#13268), but was soon reverted in https://github.com/jestjs/jest/releases/tag/v29.1.2.

So in fact, the feature remains unimplemented.

Motivation

Faster detection of broken function signatures + allow IDEs to auto rename the test parameters when renaming the original function parameters.

Example

No response

Pitch

Seeing that this feature request was opened here in the past, I assume it fits here still.

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[SimenB]

PR very much welcome - as noted in #13339 there are some regression tests added, so hopefully we won't have the same problems.

[eyalroth]

@SimenB Hey :) I started working on a PR in draft mode.

Before completing it, I wanted to know if that's the right direction.

I also had two specific questions about the PR:

1. I added an import type from jest-mock to jest-types package.
   Should I change something in the dependencies?

2. The type-checking of "examples and tests" (yarn typecheck:tests) fails on a few cases:
   a) In throwMatcher.test.ts, mockedMatch is defined with jest.fn and a no-args function, causing later expect to fail since it passes an argument to toHaveBeenCalledWith.
   b) In Farm.test.ts the same is happening with computeWorkerKey.
   c) In BaseWorkerPool.test.ts the type of the argument given to expect(Worker).toHaveBeenNthCalledWith() does not exactly match the type of the mock argument (WorkerOptions).

These failures seems to me like the expected behavior of this new feature, meaning that it's likely to introduce breaking changes to existing code. What are your thoughts on this?

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[SimenB]

https://github.com/jestjs/jest/releases/tag/v30.0.0-alpha.6