Unable to instantiate data members of kind Nat in backpack signatures.
This is in context with backpack signatures and their instantiation with concrete implementation. Consider the signature Abstract which contains a
data NatType of kind Nat.
{- skipped relevant language extensions -}
signature Abstract where
import GHC.TypeLits
data NatType :: Nat -- comment this out
Concrete implementations are unable to instantiate this abstract class during linking
module Concrete where
type NatType = 42This is neither working with explicit .bkp files nor actual cabal package. I have isolated a minimum example into a repository a cabal packages as well as a single bkp file. The urls above also have the associated ghc log messages.
The version of ghc I have tested with is 8.4.1
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.4.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |