Looping in validtypeargs pass

[lnsolar]

class Subtype[S, T] where (S < T) {}

type Copyable[Slf] = {
  copy(self: Slf) : Slf
} & (Slf < Copyable[Slf])

class C {
  copy(self: C): C
}

let x : Subtype[C, Copyable[C]]

Checking that Subtype[C, Copyable[C]] is a valid type instantiation results in looping.

[mjp41]

I have created a branch with this example on:
regression_652
This can be used to debug and test alternatives to the implementation.