Fix scoped type variables for expression type signatures

[ghc-hetmet.git] / compiler / basicTypes / DataCon.lhs

diff --git a/compiler/basicTypes/DataCon.lhs b/compiler/basicTypes/DataCon.lhs
index 0b0dead..3450602 100644 (file)
--- a/compiler/basicTypes/DataCon.lhs
+++ b/compiler/basicTypes/DataCon.lhs
@@ -33,22 +33,21 @@ import Type         ( Type, ThetaType,
                          substTyWith, substTyVar, mkTopTvSubst, 
                          mkForAllTys, mkFunTys, mkTyConApp, mkTyVarTy, mkTyVarTys, 
                          splitTyConApp_maybe, newTyConInstRhs, 
-                         mkPredTys, isStrictPred, pprType, mkPredTy
+                         mkPredTys, isStrictPred, pprType
                        )
 import Coercion                ( isEqPred, mkEqPred )
 import TyCon           ( TyCon, FieldLabel, tyConDataCons, 
                          isProductTyCon, isTupleTyCon, isUnboxedTupleTyCon,
-                          isNewTyCon, isRecursiveTyCon )
+                          isNewTyCon, isClosedNewTyCon, isRecursiveTyCon,
+                          tyConFamInst_maybe )
 import Class           ( Class, classTyCon )
-import Name            ( Name, NamedThing(..), nameUnique, mkSysTvName, mkSystemName )
-+ import Var           ( TyVar, CoVar, Id, mkTyVar, tyVarKind, setVarUnique,
-+                           mkCoVar )
+import Name            ( Name, NamedThing(..), nameUnique )
+import Var             ( TyVar, Id )
 import BasicTypes      ( Arity, StrictnessMark(..) )
 import Outputable
 import Unique          ( Unique, Uniquable(..) )
 import ListSetOps      ( assoc, minusList )
 import Util            ( zipEqual, zipWithEqual )
-import List            ( partition )
 import Maybes           ( expectJust )
 import FastString
 \end{code}
@@ -444,22 +443,29 @@ mkDataCon name declared_infix
          eq_spec theta
          orig_arg_tys tycon
          stupid_theta ids
+-- Warning: mkDataCon is not a good place to check invariants. 
+-- If the programmer writes the wrong result type in the decl, thus:
+--     data T a where { MkT :: S }
+-- then it's possible that the univ_tvs may hit an assertion failure
+-- if you pull on univ_tvs.  This case is checked by checkValidDataCon,
+-- so the error is detected properly... it's just that asaertions here
+-- are a little dodgy.
+
   = ASSERT( not (any isEqPred theta) )
        -- We don't currently allow any equality predicates on
        -- a data constructor (apart from the GADT ones in eq_spec)
     con
   where
     is_vanilla = null ex_tvs && null eq_spec && null theta
-    con = ASSERT( is_vanilla || not (isNewTyCon tycon) )
-               -- Invariant: newtypes have a vanilla data-con
-         MkData {dcName = name, dcUnique = nameUnique name, 
+    con = MkData {dcName = name, dcUnique = nameUnique name, 
                  dcVanilla = is_vanilla, dcInfix = declared_infix,
                  dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, 
                  dcEqSpec = eq_spec, 
                  dcStupidTheta = stupid_theta, dcTheta = theta,
                  dcOrigArgTys = orig_arg_tys, dcTyCon = tycon, 
                  dcRepArgTys = rep_arg_tys,
-                 dcStrictMarks = arg_stricts, dcRepStrictness = rep_arg_stricts,
+                 dcStrictMarks = arg_stricts, 
+                 dcRepStrictness = rep_arg_stricts,
                  dcFields = fields, dcTag = tag, dcRepType = ty,
                  dcIds = ids }
 
@@ -606,6 +612,8 @@ dataConUserType :: DataCon -> Type
 --     T :: forall a. a -> T [a]
 -- rather than
 --     T :: forall b. forall a. (a=[b]) => a -> T b
+-- NB: If the constructor is part of a data instance, the result type
+-- mentions the family tycon, not the internal one.
 dataConUserType  (MkData { dcUnivTyVars = univ_tvs, 
                           dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
                           dcTheta = theta, dcOrigArgTys = arg_tys,
@@ -613,7 +621,9 @@ dataConUserType  (MkData { dcUnivTyVars = univ_tvs,
   = mkForAllTys ((univ_tvs `minusList` map fst eq_spec) ++ ex_tvs) $
     mkFunTys (mkPredTys theta) $
     mkFunTys arg_tys $
-    mkTyConApp tycon (map (substTyVar subst) univ_tvs)
+    case tyConFamInst_maybe tycon of
+      Nothing             -> mkTyConApp tycon (map (substTyVar subst) univ_tvs)
+      Just (ftc, insttys) -> mkTyConApp ftc insttys        -- data instance
   where
     subst = mkTopTvSubst eq_spec
 
@@ -722,9 +732,10 @@ splitProductType str ty
 deepSplitProductType_maybe ty
   = do { (res@(tycon, tycon_args, _, _)) <- splitProductType_maybe ty
        ; let {result 
-             | isNewTyCon tycon && not (isRecursiveTyCon tycon)
+             | isClosedNewTyCon tycon && not (isRecursiveTyCon tycon)
              = deepSplitProductType_maybe (newTyConInstRhs tycon tycon_args)
-             | isNewTyCon tycon = Nothing  -- cannot unbox through recursive newtypes
+             | isNewTyCon tycon = Nothing  -- cannot unbox through recursive
+                                          -- newtypes nor through families
              | otherwise = Just res}
        ; result
        }
@@ -746,6 +757,6 @@ computeRep stricts tys
     unbox MarkedStrict    ty = [(MarkedStrict,    ty)]
     unbox MarkedUnboxed   ty = zipEqual "computeRep" (dataConRepStrictness arg_dc) arg_tys
                                where
-                                 (tycon, tycon_args, arg_dc, arg_tys) 
+                                 (_tycon, _tycon_args, arg_dc, arg_tys) 
                                      = deepSplitProductType "unbox_strict_arg_ty" ty
 \end{code}