WARNING: file compiler/stgSyn/CoreToStg.hs, line 250: $fCategoryConstraint:- True False
Tried to debug unrelated build failure of constraints-0.4.1.3 and found this in today's ghc-HEAD:
$ inplace/bin/ghc-stage2 -fforce-recomp -c C.hs -O0
WARNING: file compiler/stgSyn/CoreToStg.hs, line 250
$fCategoryConstraint:- True False{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE GADTs #-}
module C () where
import Control.Category
import GHC.Types (Constraint)
data Dict :: Constraint -> * where
Dict :: a => Dict a
infixr 9 :-
newtype a :- b = Sub (a => Dict b)
instance Category (:-) where
id = refl
(.) = trans
infixl 1 \\
(\\) :: a => (b => r) -> (a :- b) -> r
r \\ Sub Dict = r
trans :: (b :- c) -> (a :- b) -> a :- c
trans f g = Sub (Dict \\ f \\ g)
refl :: a :- a
refl = Sub Dict
{-
$ inplace/bin/ghc-stage2 -fforce-recomp -c C.hs -O0
WARNING: file compiler/stgSyn/CoreToStg.hs, line 250
$fCategoryConstraint:- True False
-}Original file it was factored out is: https://github.com/ekmett/constraints/blob/c550b7653e88d58882873d11f05538d783313a05/src/Data/Constraint.hs
Might be a result of D1889
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | osa1 |
| Operating system | |
| Architecture |