[Ur] show t

[Gergely Buday]

Hi,

I wanted to express that an argument is show-able by a proper  t ->
string function. It seems that I had success with the function show_
but not with the main function. Why does this simple code leads to a
too difficult unification problem?

- Gergely

$ cat bar.ur
fun show_ [t] (arg : show t) =
    return <xml>{[arg]}</xml>

fun main () = show_ "Hello World!"
$ urweb bar
/home/user/local/sandbox/bar.ur:4:14-4:19: Substitution in constructor
is blocked by a too-deep unification variable
Replacement:  <UNIF:O::Type>
       Body:
((Basis.show UNBOUND_REL0) ->
  <UNIF:B::Type -> Type>
   (Basis.xml <UNIF:E::{Unit}> <UNIF:F::{Type}> ([])))