GHC.Prim does not export Constraint
This code from the effect-monad library worked in ghc-7.10, but fails with ghc-8.0.1-rc1:
{-# LANGUAGE TypeFamilies, ConstraintKinds, PolyKinds #-}
module Control.Effect.Cond where
import GHC.Prim
class Cond (m :: k -> * -> *) where
type AltInv m (s :: k) (t :: k) :: ConstraintIt seems one now needs to import Constraint from GHC.Exts.
This should be mentioned in the migration guide (https://ghc.haskell.org/trac/ghc/wiki/Migration/8.0), together with any other breaking changes there might be from the kind equalities patch (67465497).
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.0.1-rc1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | highest |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |