Hi all

If I have a happy parser for an AST that is polymorphic, is there any way to put constraints on the individual rules?

e.g. if I have

data Foo a = Foo String a

and a rule something like

foo :: { (Show a) => Foo a }

foo : otherrule { Foo (show $1) $1 }

Because of the way the tables are constructed in happy, the Show constraint is not attached to the point where the rule RHS is applied.

Is this simply impossible?

Alan