Generics

[xuhuanzy]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @xuhuanzy, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an enhancement in the handling of generic types within the code analysis system. The primary change involves refining how rest parameters are processed when their generic type is instantiated as a tuple. Previously, the system might not have correctly expanded the elements of such a tuple into individual parameters, potentially leading to incorrect type checking. The updated logic now ensures that these tuple types are properly unfolded, allowing for accurate validation of function calls against generic definitions that utilize tuple-instantiated rest parameters.

Highlights

• Generic Rest Parameter Expansion: Implemented logic to correctly expand tuple types when they are used to instantiate generic rest parameters in function definitions. This ensures that a generic rest parameter like ...: A where A is instantiated as [Type1, Type2] is correctly interpreted as ...: Type1, Type2.
• New Test Case for Tuple Generics: Added test_issue_738 to validate the correct handling of generic rest parameters instantiated with tuple types, specifically checking for parameter type mismatches.

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[gemini-code-assist]

Code Review

This pull request aims to improve handling of generic variadic parameters, particularly when they resolve to a tuple type. The implementation has a critical logic flaw that can lead to parameters being dropped during type instantiation, which I've provided a fix for. Additionally, the new test case has an inverted assertion that would cause it to fail on correct code. I've included a suggestion to correct the test's logic.

[Aetherall]

Hi @xuhuanzy, sorry to bother, I wondered if this PR was allowing to infer the content of generic types captured in parameter ?

Something along the lines of

---@generic T
---@param future Future<T> 
---@return T
---@async
function await(future)
  return future:wait()
end

--- somewhere in uv coroutine context
local result = await fetchUser() --- Future<User>
---    ^ User

Anyway I am so gratetful to start a lua project in this times where this project make it really close to type systems I am used to working with ! Really a great future for embedded scripting <3

[xuhuanzy]

@Aetherall This PR is not needed. It already supported capturing generic parameters before this PR. This PR provides advanced usage, such as conditional types, mapped types, etc.

[xuhuanzy]

Awesome ! Won't this alias definition be simplified by the checker though ? will it work with

---@alias Future<T> { wait: fun () -> T }

[Aetherall]

I must be using incorrect version or settings, thanks for the confirmation ! Mapped types will allow me to remove a really big chunk of annotations in my project ahah many thanks for this PR