Avoid emitting 'Function'

[DanielRosenwasser]

While 'Function' is very general, it's problematic in some ways because it's not assignable back to types with more general call signatures like (...args: any[]) => any.

You can probably take some inspiration from how dts-gen determines arity for function to improve things here.

[urish]

That's a good point, thank you Daniel!

Another thought I had - perhaps creating a Proxy object and wrapping the function with this Proxy will allow to actually detect the argument types in runtime?

The dts-gen solution sounds easier to start with though.

[kaminskypavel]

@DanielRosenwasser great suggestion, i'll have a stab at it

[DanielRosenwasser]

Just as a heads up, dts-gen uses a package called dts-dom which is also another handy utility you can use for building up declarations. 😃