On Mon, Mar 25, 2019 at 6:24 PM Anthony Clayden <
anthony_clay...@clear.net.nz> wrote:
>...
>
Errk. pasted the wrong example. The code that works is
class F a b | a -> b
instance F Int Bool
class D a where { op :: (F a b) => a -> b }
instance (TypeCast Bool b') => D Int
heh heh. I've got to record this for posterity. I've never known an example
before.
Some code that compiles in Hugs and works fine; but GHC (8.6.4) can't
typecheck so rejects.
It's an example in the 2011 'System F with Type Equality Coercions',
section 2.3 discussing FunDeps; and used to justify
