Expression Int{} should be an error

[eschnett]

Int is not a type constructor, hence defining additional type parameters doesn't make sense.

[StefanKarpinski]

One can argue that concrete types as zero-parameter type constructors.

[eschnett]

Yes, though that's similar to arguing that scalars are 0d arrays, or that constants are functions that don't take arguments. I don't think it's a good thing. For example, Julia does make a distinction between Tuple and Tuple{}, so the empty curlies are not always a no-op.

I wrote up some thoughts about this a few weeks ago https://eschnett.github.io/julia/2016/06/23/some-thoughts-on-generic-programming-in-julia.

[JeffBezanson]

I think this can be handled in #8974. It will only be valid to do type application with UnionAll types (plus Tuple and Union as special cases), whereas now the meaning of A{} is fuzzier.

[JeffBezanson]

closed by #18457