import DataCon
import PrelNames
import BasicTypes hiding (SuccessFlag(..))
+import DynFlags ( DynFlag( Opt_GADTs ) )
import SrcLoc
import ErrUtils
import Util
-- 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
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))