GHC rejects typeclass with associated type
In GHC 7.8.4, the following code is legal:
{-# LANGUAGE TypeFamilies, FlexibleContexts #-}
class FiniteGrid g where
type Size s
size :: g -> Size g
maxPossibleDistance :: g -> Int
But with GHC 7.10.1, it no longer compiles. The error message is:
The associated type ‘Size’
mentions none of the type or kind variables of the class ‘FiniteGrid g’
In the class declaration for ‘FiniteGrid’
I didn't see any mention of this in the migration guide, but perhaps there's another pragma I need to enable. I thought this might be related to #10020 (closed), but that bug is apparently fixed in GHC 7.10.1.
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |
Edited by mhwombat