#include "HsVersions.h"
import HsSyn
-import HsTypes
import HscTypes
import BuildTyCl
import TcUnify
import Var
import VarSet
import Name
-import OccName
import Outputable
import Maybes
-import Monad
import Unify
import Util
import SrcLoc
import BasicTypes
import Bag
+import Control.Monad
import Data.List
-import Control.Monad ( mplus )
\end{code}
; checkValidTypeInst t_typats t_rhs
-- (4) construct representation tycon
- ; rep_tc_name <- newFamInstTyConName tc_name loc
+ ; rep_tc_name <- newFamInstTyConName tc_name t_typats loc
; buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
(typeKind t_rhs) (Just (family, t_typats))
}}
newtypeConError tc_name (length k_cons)
-- (4) construct representation tycon
- ; rep_tc_name <- newFamInstTyConName tc_name loc
+ ; rep_tc_name <- newFamInstTyConName tc_name t_typats loc
; let ex_ok = True -- Existentials ok for type families!
; fixM (\ rep_tycon -> do
{ let orig_res_ty = mkTyConApp fam_tycon t_typats
; idx_tys <- doptM Opt_TypeFamilies
; checkTc idx_tys $ badFamInstDecl tc_name
- -- Check for no type indices
- ; checkTc (not (null tvs)) (noIndexTypes tc_name)
-
; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) kind Nothing
; return [ATyCon tycon]
}
; idx_tys <- doptM Opt_TypeFamilies
; checkTc idx_tys $ badFamInstDecl tc_name
- -- Check for no type indices
- ; checkTc (not (null tvs)) (noIndexTypes tc_name)
-
; tycon <- buildAlgTyCon tc_name final_tvs []
mkOpenDataTyConRhs Recursive False True Nothing
; return [ATyCon tycon]
-- Add catch-all default case unless the case is exhaustive
-- We do this explicitly so that we get a nice error message that
-- mentions this particular record selector
- deflt | length cons_w_field == length all_cons = []
+ deflt | not (any is_unused all_cons) = []
| otherwise = [mkSimpleMatch [nlWildPat]
(nlHsApp (nlHsVar (getName rEC_SEL_ERROR_ID))
(nlHsLit msg_lit))]
- unit_rhs = L loc $ ExplicitTuple [] Boxed
+ -- Do not add a default case unless there are unmatched
+ -- constructors. We must take account of GADTs, else we
+ -- get overlap warning messages from the pattern-match checker
+ is_unused con = not (con `elem` cons_w_field
+ || dataConCannotMatch inst_tys con)
+ inst_tys = tyConAppArgs data_ty
+
+ unit_rhs = mkLHsTupleExpr []
msg_lit = HsStringPrim $ mkFastString $
occNameString (getOccName sel_name)
quotes (ppr tc_name)
, nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
-noIndexTypes :: Name -> SDoc
-noIndexTypes tc_name
- = ptext (sLit "Type family constructor") <+> quotes (ppr tc_name)
- <+> ptext (sLit "must have at least one type index parameter")
-
badFamInstDecl :: Outputable a => a -> SDoc
badFamInstDecl tc_name
= vcat [ ptext (sLit "Illegal family instance for") <+>