diff options
Diffstat (limited to 'compiler/GHC/Tc/Validity.hs')
| -rw-r--r-- | compiler/GHC/Tc/Validity.hs | 20 |
1 files changed, 7 insertions, 13 deletions
diff --git a/compiler/GHC/Tc/Validity.hs b/compiler/GHC/Tc/Validity.hs index 5072b8eeff..15168ddd2f 100644 --- a/compiler/GHC/Tc/Validity.hs +++ b/compiler/GHC/Tc/Validity.hs @@ -1734,15 +1734,12 @@ synonyms, by matching on TyConApp directly. -} checkValidInstance :: UserTypeCtxt -> LHsSigType GhcRn -> Type -> TcM () -checkValidInstance ctxt hs_type ty - | not is_tc_app - = failWithTc (TcRnNoClassInstHead tau) - - | isNothing mb_cls - = failWithTc (TcRnIllegalClassInst (tyConFlavour tc)) - - | otherwise - = do { setSrcSpanA head_loc $ +checkValidInstance ctxt hs_type ty = case tau of + -- See Note [Instances and constraint synonyms] + TyConApp tc inst_tys -> case tyConClass_maybe tc of + Nothing -> failWithTc (TcRnIllegalClassInst (tyConFlavour tc)) + Just clas -> do + { setSrcSpanA head_loc $ checkValidInstHead ctxt clas inst_tys ; traceTc "checkValidInstance {" (ppr ty) @@ -1775,12 +1772,9 @@ checkValidInstance ctxt hs_type ty ; traceTc "End checkValidInstance }" empty ; return () } + _ -> failWithTc (TcRnNoClassInstHead tau) where (_tvs, theta, tau) = tcSplitSigmaTy ty - is_tc_app = case tau of { TyConApp {} -> True; _ -> False } - TyConApp tc inst_tys = tau -- See Note [Instances and constraint synonyms] - mb_cls = tyConClass_maybe tc - Just clas = mb_cls -- The location of the "head" of the instance head_loc = getLoc (getLHsInstDeclHead hs_type) |