T10715.hs:9:13: error:
• Couldn't match representation of type ‘a’ with that of ‘X a’
‘a’ is a rigid type variable bound by
the type signature for:
doCoerce :: forall a. Coercible a (X a) => a -> X a
at T10715.hs:9:13-41
Inaccessible code in
the type signature for:
doCoerce :: Coercible a (X a) => a -> X a
• In the ambiguity check for ‘doCoerce’
To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
In the type signature: doCoerce :: Coercible a (X a) => a -> X a