import TcUnify
import TcHsType
import TysWiredIn
-import Type
import Coercion
import StaticFlags
import TyCon
import DataCon
import PrelNames
import BasicTypes hiding (SuccessFlag(..))
+import DynFlags ( DynFlag( Opt_GADTs ) )
import SrcLoc
import ErrUtils
import Util
-import Maybes
import Outputable
import FastString
-import Monad
+import Control.Monad
\end{code}
tcPatBndr (PS { pat_ctxt = LetPat lookup_sig }) bndr_name pat_ty
| Just mono_ty <- lookup_sig bndr_name
= do { mono_name <- newLocalName bndr_name
- ; boxyUnify mono_ty pat_ty
+ ; _ <- boxyUnify mono_ty pat_ty
; return (Id.mkLocalId mono_name mono_ty) }
| otherwise
return ty'
else do -- OpenTypeKind, so constrain it
{ ty2 <- newFlexiTyVarTy argTypeKind
- ; unifyType ty' ty2
+ ; _ <- unifyType ty' ty2
; return ty' }}
where
msg = pp_this <+> ptext (sLit "cannot be bound to an unboxed tuple")
-- getLIE/extendLIEs: see Note [Hopping the LIE in lazy patterns]
-- Check no existentials
- ; if (null pat_tvs) then return ()
- else lazyPatErr lpat pat_tvs
+ ; unless (null pat_tvs) $ lazyPatErr lpat pat_tvs
+
+ -- Check there are no unlifted types under the lazy pattern
+ ; when (any (isUnLiftedType . idType) $ collectPatBinders pat') $
+ lazyUnliftedPatErr lpat
-- Check that the pattern has a lifted type
; pat_tv <- newBoxyTyVar liftedTypeKind
- ; boxyUnify pat_ty (mkTyVarTy pat_tv)
+ ; _ <- boxyUnify pat_ty (mkTyVarTy pat_tv)
; return (LazyPat pat', [], res) }
unwrap_ty res_pat
-- Add the stupid theta
- ; addDataConStupidTheta data_con ctxt_res_tys
+ ; setSrcSpan con_span $ addDataConStupidTheta data_con ctxt_res_tys
; ex_tvs' <- tcInstSkolTyVars skol_info ex_tvs
-- Get location from monad, not from ex_tvs
pstate' | no_equalities = pstate
| otherwise = pstate { pat_eqs = True }
+ ; gadts_on <- doptM Opt_GADTs
+ ; checkTc (no_equalities || gadts_on)
+ (ptext (sLit "A pattern match on a GADT requires -XGADTs"))
+ -- Trac #2905 decided that a *pattern-match* of a GADT
+ -- should require the GADT language flag
+
; unless no_equalities $ checkTc (isRigidTy pat_ty) $
nonRigidMatch (pat_ctxt pstate) data_con
hang (ptext (sLit "A lazy (~) pattern cannot match existential or GADT data constructors"))
2 (vcat (map pprSkolTvBinding tvs))
+lazyUnliftedPatErr :: OutputableBndr name => Pat name -> TcM ()
+lazyUnliftedPatErr pat
+ = failWithTc $
+ hang (ptext (sLit "A lazy (~) pattern cannot contain unlifted types"))
+ 2 (ppr pat)
+
nonRigidMatch :: PatCtxt -> DataCon -> SDoc
nonRigidMatch ctxt con
= hang (ptext (sLit "GADT pattern match in non-rigid context for") <+> quotes (ppr con))