diff options
Diffstat (limited to 'compiler/deSugar/Check.hs')
| -rw-r--r-- | compiler/deSugar/Check.hs | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/compiler/deSugar/Check.hs b/compiler/deSugar/Check.hs index 2b1995cdd5..b0155d3e2f 100644 --- a/compiler/deSugar/Check.hs +++ b/compiler/deSugar/Check.hs @@ -27,6 +27,7 @@ import Id import ConLike import Name import FamInstEnv +import TysPrim (tYPETyCon) import TysWiredIn import TyCon import SrcLoc @@ -440,6 +441,19 @@ inhabitationCandidates fam_insts ty (_:_) -> do var <- liftD $ mkPmId (toTcType core_ty) let va = build_tm (PmVar var) dcs return $ Right [(va, mkIdEq var, emptyBag)] + + -- TYPE (which is the underlying kind behind Type, among others) + -- is conceptually an empty datatype, so one would expect this code + -- (from #14086) to compile without warnings: + -- + -- f :: Type -> Int + -- f x = case x of {} + -- + -- However, since TYPE is a primitive builtin type, not an actual + -- datatype, we must convince the coverage checker of this fact by + -- adding a special case here. + | tc == tYPETyCon -> pure (Right []) + | isClosedAlgType core_ty -> liftD $ do var <- mkPmId (toTcType core_ty) -- it would be wrong to unify x alts <- mapM (mkOneConFull var . RealDataCon) (tyConDataCons tc) |