What version of the GHC code are you looking at? The parser is currently stored in compiler/parser/Parser.y.pp (note the pp) and doesn’t have these lines. As far as I know, there is no way to refer to OpenKind from source.
You’re absolutely right about the type of `undefined`. `undefined` (and `error`) have magical types. GHC knows that GHC.Err defines an `undefined` symbol and gives it its type by fiat. There is no way (I believe) to reproduce this behavior.
If you have -fprint-explicit-foralls and -fprint-explicit-kinds enabled, quantified variables of kind * are not given kinds in the output. So, the lack of a kind annotation tells you that `a`’s kind is *. Any other kind (assuming these flags) would be printed.
I hope this helps!
Richard
On Apr 15, 2014, at 7:39 PM, Conal Elliott
I see ‘#’ for unlifted and ‘?’ for open kinds in compiler/parser/Parser.y: akind :: { IfaceKind } : '*' { ifaceLiftedTypeKind } | '#' { ifaceUnliftedTypeKind } | '?' { ifaceOpenTypeKind } | '(' kind ')' { $2 }
kind :: { IfaceKind } : akind { $1 } | akind '->' kind { ifaceArrow $1 $3 } However, I don’t know how to get GHC to accept ‘#’ or ‘?’ in a kind annotation. Are these kinds really available to source programs.
I see that undefined has an open-kinded type:
*Main> :i undefined undefined :: forall (a :: OpenKind). a -- Defined in ‘GHC.Err’ Looking in the GHC.Err source, I just see the following:
undefined :: a undefined = error "Prelude.undefined" However, if I try similarly,
q :: a q = error "q" I don’t see a similar type:
*X> :i q q :: forall a. a -- Defined at ../test/X.hs:12:1
I don't know what kind 'a' has here, nor how to find out.
-- Conal _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users