Fix type checking of imported data instances

Mon Sep 18 19:48:41 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Fix type checking of imported data instances
  Mon Sep 11 20:06:51 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * Fix type checking of imported data instances
    - When reading a data/newtype instance from an interface, the data constructors
      have their own universals that do not necessarily match up with their tycon's
      type parameters.  (Whereas when type checking source, they are always the
      same.)
    - Hence, we need to be careful when building the wrapper signature of imported
      data constructors from data/newtype instances, and rename the type variables
      in the instance types appropriately.

diff --git a/compiler/basicTypes/MkId.lhs b/compiler/basicTypes/MkId.lhs
index 54bbae9..3e54813 100644 (file)
--- a/compiler/basicTypes/MkId.lhs
+++ b/compiler/basicTypes/MkId.lhs
@@ -47,7 +47,8 @@ import TysPrim                ( openAlphaTyVars, alphaTyVar, alphaTy,
 import TysWiredIn      ( charTy, mkListTy )
 import PrelRules       ( primOpRules )
 import Type            ( TyThing(..), mkForAllTy, tyVarsOfTypes, 
-                         newTyConInstRhs, mkTopTvSubst, substTyVar, substTy )
+                         newTyConInstRhs, mkTopTvSubst, substTyVar, substTy,
+                         substTys, zipTopTvSubst )
 import TcGadt           ( gadtRefine, refineType, emptyRefinement )
 import HsBinds          ( ExprCoFn(..), isIdCoercion )
 import Coercion         ( mkSymCoercion, mkUnsafeCoercion, isEqPred )
@@ -60,7 +61,8 @@ import TcType         ( Type, ThetaType, mkDictTy, mkPredTys, mkPredTy,
 import CoreUtils       ( exprType, dataConOrigInstPat, mkCoerce )
 import CoreUnfold      ( mkTopUnfolding, mkCompulsoryUnfolding )
 import Literal         ( nullAddrLit, mkStringLit )
-import TyCon           ( TyCon, isNewTyCon, tyConDataCons, FieldLabel,
+import TyCon           ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
+                         FieldLabel,
                           tyConStupidTheta, isProductTyCon, isDataTyCon,
                           isRecursiveTyCon, isFamInstTyCon,
                           tyConFamInst_maybe, tyConFamilyCoercion_maybe,
@@ -240,6 +242,12 @@ mkDataConIds wrap_name wkr_name data_con
        -- extra constraints where necessary.
     wrap_tvs = (univ_tvs `minusList` map fst eq_spec) ++ ex_tvs
     subst         = mkTopTvSubst eq_spec
+    famSubst      = ASSERT( length (tyConTyVars tycon  ) ==  
+                            length (mkTyVarTys univ_tvs)   )
+                    zipTopTvSubst (tyConTyVars tycon) (mkTyVarTys univ_tvs)
+                    -- substitution mapping the type constructor's type
+                    -- arguments to the universals of the data constructor
+                    -- (crucial when type checking interfaces)
     dict_tys       = mkPredTys theta
     result_ty_args = map (substTyVar subst) univ_tvs
     result_ty      = case tyConFamInst_maybe tycon of
@@ -248,7 +256,9 @@ mkDataConIds wrap_name wkr_name data_con
                         -- family instance constructor
                       Just (familyTyCon, 
                             instTys)     -> 
-                        mkTyConApp familyTyCon (map (substTy subst) instTys)
+                        mkTyConApp familyTyCon ( substTys subst 
+                                               . substTys famSubst 
+                                               $ instTys)
     wrap_ty        = mkForAllTys wrap_tvs $ mkFunTys dict_tys $
                     mkFunTys orig_arg_tys $ result_ty
        -- NB: watch out here if you allow user-written equality 

diff --git a/compiler/types/TyCon.lhs b/compiler/types/TyCon.lhs
index 31cb19b..b359660 100644 (file)
--- a/compiler/types/TyCon.lhs
+++ b/compiler/types/TyCon.lhs
@@ -101,6 +101,8 @@ data TyCon
        tyConTyVars :: [TyVar],         -- Scopes over (a) the algTcStupidTheta
                                        --             (b) the cached types in
                                        --                 algTyConRhs.NewTyCon
+                                       --             (c) the family instance
+                                       --                 types if present
                                        -- But not over the data constructors
 
         tyConArgPoss :: Maybe [Int],    -- for associated families: for each