There seems to be a bug in the way constraint are handled:
type 'a exp=[
| `Add of 'e * 'e
| `Mul of 'e * 'e
]
constraint 'a = <exp:'e;..>

type 'a exp2=[
| 'a exp
| `Sub of 'e * 'e
| `Mul of 'e * 'e
]
constraint 'a = <exp2:'e;..>;;

doesn't type correctly but seems perfectly legal to me... Am I missing
anything here?

Till