19 Nov 2012 15:18
Promoted types accepted without language extensions
Sean Leather <leather <at> cs.uu.nl>
2012-11-19 14:18:54 GMT
2012-11-19 14:18:54 GMT
We discovered that GHC and GHCi (7.4.1) accept promoted types without specifying language extensions (and even when specifying -XHaskell98).
For example, promoted lists are accepted:
Prelude> type T = [Int,Char]
Prelude> :i T
type T = (:) * Int ((:) * Char ([] *))
-- Defined at <interactive>:2:6
Also, promoted datatypes:
> data N = Z
> type T = 'Z
I'm guessing you can't use these types anywhere (since they are not kind *), so they won't be very useful, but it seems like this should be disallowed.
Regards,
Sean
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