diff options
Diffstat (limited to 'compiler/GHC/Tc/Deriv/Generics.hs')
| -rw-r--r-- | compiler/GHC/Tc/Deriv/Generics.hs | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/compiler/GHC/Tc/Deriv/Generics.hs b/compiler/GHC/Tc/Deriv/Generics.hs index b47d6cd632..d35bac99a4 100644 --- a/compiler/GHC/Tc/Deriv/Generics.hs +++ b/compiler/GHC/Tc/Deriv/Generics.hs @@ -21,7 +21,7 @@ module GHC.Tc.Deriv.Generics ) where -import GHC.Prelude +import GHC.Prelude hiding (head, init, last, tail) import GHC.Hs import GHC.Core.Type @@ -62,6 +62,9 @@ import Language.Haskell.Syntax.Basic (FieldLabelString(..)) import Control.Monad (mplus) import Data.List (zip4, partition) +import qualified Data.List as Partial (last) +import Data.List.NonEmpty (nonEmpty) +import qualified Data.List.NonEmpty as NE import Data.Maybe (isJust) {- @@ -291,9 +294,9 @@ canDoGenerics1 dit@(DerivInstTys{dit_rep_tc = rep_tc}) = , ft_var = caseVar, ft_co_var = caseVar -- (component_0,component_1,...,component_n) - , ft_tup = \_ components -> if any _ccdg1_hasParam (init components) - then bmbad con - else foldr bmplus bmzero components + , ft_tup = \_ components -> case nonEmpty components of + Just components' | any _ccdg1_hasParam (NE.init components') -> bmbad con + _ -> foldr bmplus bmzero components -- (dom -> rng), where the head of ty is not a tuple tycon , ft_fun = \dom rng -> -- cf #8516 @@ -344,7 +347,7 @@ gk2gkDC Gen1 dc tc_args = Gen1_DC $ assert (isTyVarTy last_dc_inst_univ) where dc_inst_univs = dataConInstUnivs dc tc_args last_dc_inst_univ = assert (not (null dc_inst_univs)) $ - last dc_inst_univs + Partial.last dc_inst_univs -- Bindings for the Generic instance |