Foldable cannot be derived by GND due to redundant contexts
If GND is enabled, and roles don't permit a Foldable
instance to be derived, it won't fall back on DeriveFoldable
; instead it just produces an error. I think ideally I'd want to use a pragma to state explicitly that I want to use DeriveFoldable
-style deriving for this specific instance, but an implicit fallback would be acceptable.
{-# LANGUAGE
-- GeneralizedNewtypeDeriving,
DeriveFoldable #-}
module Derive where
import qualified Data.IntMap as M
newtype UniqFM ele = UFM {unUFM :: M.IntMap ele}
deriving (Foldable)
Trac metadata
Trac field | Value |
---|---|
Version | 7.9 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |