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  • Glasgow Haskell Compiler
  • GHCGHC
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  • #15138
Closed
Open
Created May 10, 2018 by Piyush P Kurur@ppkReporter

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 = 42

This 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
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