Looks like a bug. I think the `coercionXX = Coercion` should work.
Richard
On Dec 5, 2015, at 9:58 PM, David Feuer
If I have
{-# LANGUAGE PolyKinds, TypeFamilies #-} import Data.Type.Coercion
type family X :: k
and I want
coercionXX :: Coercion X X,
the obvious thing,
coercionXX = Coercion,
doesn't work:
Couldn't match representation of type ‘X’ with that of ‘X’ NB: ‘X’ is a type function, and may not be injective Relevant role signatures: type role X nominal Relevant bindings include coercionXX :: Coercion X X (bound at Fold.hs:167:1) In the expression: Coercion In an equation for ‘coercionXX’: coercionXX = Coercion
However, if I write
coercionXX = x where x = Coercion,
that does work! What gives? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe