Design and handle first class types

[CohenArthur]

• allow creating types on the fly in function arguments

func foo(a: int | bool) {}
func foo(a: type_function("a", int)) {}
func foo(a: type Foo(int, bool)) {}
func foo(a: type IntOrBool = int | bool)) {}

this will require changes to the name resolution, as function arguments will no longer be usage points but also possibly declarations.

we will need to formalize it so that it integrates nicely with the kind system. in Haskell syntax, all types of a function's argument will need to be of kind *

[CohenArthur]

Add following syntax?

type Nothing;

type Maybe[T] =
    | Nothing
    | T;

[CohenArthur]

Add following syntax?

type Maybe[T] =
    | type Nothing
    | type Some(T);