Variadic type parameters

[Frityet]

Right now, using functions with generics is quite awkward in teal, where you cant have any number of function params or returns, you must either take in the entire function as a type or deal with only 1 param/return:

local function my_cool_func<TRet, TArg>(x: function(TArg): TRet, y: TArg): TRet
    --some cool invocation magic
end

where it would fail if you tried to call it with something like:

local function add(x: integer, y: integer): integer
    return x + y
end

local val = my_cool_func(add, 1, 2)

In order to make this work, you could do something like:

local function my_cool_func<TFn>(x: TFn, ...args: any): any
   --some cool invocation magic
end

but now almost all type info is lost.

It would be cool if it would be possible to do "varadict generics", allowing for patterns such as:

local function my_cool_function<TRet, ...TArg>(x: function(TArg...): TRet, ...args: TArg...): TRet
   --even safer invocation magic
end

[hishamhm]

I was pretty sure there was an open ticket about this already, but I couldn't find it.

I have tried implementing this before and failed (that was before interfaces and the GenericType refactor). It's definitely something I would like to have, but it's really tricky to get the semantics and the implementation right!