This is a problem that I only have when the -rectypes option is activated.

$./ocaml -rectypes
         Objective Caml version 3.08.3

# type 'a t='a;;
type 'a t = 'a

# type cycle='a t as 'a;;
The type abbreviation cycle is cyclic

agreed.

# let (x : 'a t as 'a)=0;;
Fatal error: exception Stack_overflow

Shouldn't it detect the cyclic abbreviation in this case too ?

J