Typechecking on Functions

[Uhsleep]

Taking a look at the following code:

--!strict
local TestFunc: (number, string) -> nil = function()

end

Is it intentional that I don't see any warnings/errors telling me that the assigned function doesn't have the same signature as the type I declared for the variable?

[alexmccord]

Are you using luau-analyze?

[Uhsleep]

Yea when using luau-analyze, all I get back is LocalUnused: Variable 'TestFunc' is never used; prefix with '_' to silence. No warnings about the signature being different/incorrect.

[alexmccord]

Okay. I asked because luau-analyze was separate from luau and it wasn't mentioned in there.

So, it is the case that a function of the type () -> () is compatible with (number, string) -> nil, ignoring the () vs nil that we've grown to regret. You are always allowed to pass excess amount of arguments to a function because that function doesn't make use of those excess arguments. Therefore no errors are produced.

[Uhsleep]

I see, that makes sense. Although, It's kind of inconvenient not knowing whether the function being called actually adheres to the type it should have.

In my case, I had added a parameter to my function type and was confused that the function using the type showed no errors. However from the caller's perspective the behavior is the same whether they add the new parameter and do nothing with it, or they don't add the new parameter at all. I can see why they're compatible.

Thanks for clearing this up for me. Also, what do you mean when you say luau-analyze was separate from luau?