Type family bug?
Simon Peyton Jones
simonpj at microsoft.com
Thu Jan 19 10:02:21 UTC 2017
Richard
This works
type family F (a :: k)
type instance F Maybe = Char
But this does not. Surely it should?
type family F (a :: k) where -- = r | r -> a where
F Maybe = Char
The latter is rejected with
Foo.hs:6:5: error:
* Expecting one more argument to `Maybe'
Expected kind `k', but `Maybe' has kind `* -> *'
* In the first argument of `F', namely `Maybe'
In the type family declaration for `F'
If you agree I'll open a ticket.
Simon
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