Add some invariant checking for refinements

[ghc-hetmet.git] / compiler / typecheck / TcGadt.lhs

diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs
index deac1eb..75d5c54 100644 (file)
--- a/compiler/typecheck/TcGadt.lhs
+++ b/compiler/typecheck/TcGadt.lhs
@@ -18,23 +18,25 @@ module TcGadt (
 
 import HsSyn   ( ExprCoFn(..), idCoercion, isIdCoercion )
 import Coercion        ( Coercion, mkSymCoercion, mkTransCoercion, mkUnsafeCoercion,
-                 mkLeftCoercion, mkRightCoercion,
-                 splitCoercionKind, decomposeCo )
+                 mkLeftCoercion, mkRightCoercion, mkCoKind, coercionKindPredTy,
+                 splitCoercionKind, decomposeCo, coercionKind )
 import TcType  ( TvSubst(..), TvSubstEnv, substTy, mkTvSubst, 
                  substTyVar, zipTopTvSubst, typeKind,
                  eqKind, isSubKind, repSplitAppTy_maybe,
-                 tcView
+                 tcView, tcGetTyVar_maybe
                )
-import Type    ( Type, tyVarsOfType, tyVarsOfTypes )
+import Type    ( Type, tyVarsOfType, tyVarsOfTypes, tcEqType, mkTyVarTy )
 import TypeRep ( Type(..), PredType(..) )
 import DataCon ( DataCon, dataConUnivTyVars, dataConEqSpec )
-import Var     ( CoVar, TyVar, tyVarKind )
+import Var     ( CoVar, TyVar, tyVarKind, varUnique )
 import VarEnv
 import VarSet
 import ErrUtils                ( Message )
 import Maybes          ( MaybeErr(..), isJust )
 import Control.Monad   ( foldM )
 import Outputable
+import Unique          ( Unique )
+import UniqFM          ( ufmToList )
 
 #include "HsVersions.h"
 \end{code}
@@ -59,6 +61,7 @@ instance Outputable Refinement where
 emptyRefinement :: Refinement
 emptyRefinement = (Reft emptyInScopeSet emptyVarEnv)
 
+
 refineType :: Refinement -> Type -> (ExprCoFn, Type)
 -- Apply the refinement to the type.
 -- If (refineType r ty) = (co, ty')
@@ -140,7 +143,9 @@ gadtRefine (Reft in_scope env1)
 -- That is, the kinds of the co_vars are a
 -- fixed point of the  incoming refinement
 
-  = initUM (tryToBind tv_set) $
+  = ASSERT2( not $ any (`elemVarEnv` env1) (varSetElems $ tyVarsOfTypes $ map tyVarKind co_vars),
+            ppr env1 $$ ppr co_vars $$ ppr (map tyVarKind co_vars) )
+    initUM (tryToBind tv_set) $
     do {       -- Run the unifier, starting with an empty env
        ; env2 <- foldM do_one emptyInternalReft co_vars
 
@@ -148,7 +153,9 @@ gadtRefine (Reft in_scope env1)
                -- non-idempotent substitution
        ; let tmp_env = env1 `plusVarEnv` env2
               out_env = fixTvCoEnv in_scope' tmp_env
-       ; return (Reft in_scope' out_env) }
+       ; WARN( not (null (badReftElts tmp_env)), ppr (badReftElts tmp_env) $$ ppr tmp_env )
+         WARN( not (null (badReftElts out_env)), ppr (badReftElts out_env) $$ ppr out_env )
+         return (Reft in_scope' out_env) }
   where
     tv_set = mkVarSet ex_tvs
     in_scope' = foldr extend in_scope co_vars
@@ -201,14 +208,14 @@ fixTvCoEnv in_scope env
   where
     fixpt         = mapVarEnv step env
 
-    step (co, ty) = (co', ty')
+    step (co, ty) = (co1, ty')
       -- Apply fixpt one step:
       -- Use refineType to get a substituted type, ty', and a coercion, co_fn,
       -- which justifies the substitution.  If the coercion is not the identity
       -- then use transitivity with the original coercion
       where
         (co_fn, ty') = refineType (Reft in_scope fixpt) ty
-        co' | ExprCoFn co'' <- co_fn = mkTransCoercion co co''
+        co1 | ExprCoFn co'' <- co_fn = mkTransCoercion co co''
             | otherwise              = ASSERT( isIdCoercion co_fn ) co 
 
 -----------------------------
@@ -237,6 +244,8 @@ dataConCanMatch con tys
 tryToBind :: TyVarSet -> TyVar -> BindFlag
 tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe
                    | otherwise              = AvoidMe
+
+
 \end{code}
 
 
@@ -252,6 +261,19 @@ type InternalReft = TyVarEnv (Coercion, Type)
 -- INVARIANT:   a->(co,ty)   then   co :: (a:=:ty)
 -- Not necessarily idemopotent
 
+badReftElts :: InternalReft -> [(Unique, (Coercion,Type))]
+-- Return the BAD elements of the refinement
+-- Should be empty; used in asserions only
+badReftElts env
+  = filter (not . ok) (ufmToList env)
+  where
+    ok :: (Unique, (Coercion, Type)) -> Bool
+    ok (u, (co, ty)) | Just tv <- tcGetTyVar_maybe ty1
+                    = varUnique tv == u && ty `tcEqType` ty2 
+                    | otherwise = False
+       where
+         (ty1,ty2) = coercionKind co
+
 emptyInternalReft :: InternalReft
 emptyInternalReft = emptyVarEnv
 
@@ -364,8 +386,8 @@ uUnrefined :: InternalReft        -- An existing substitution to extend
            -> UM InternalReft
 
 -- We know that tv1 isn't refined
--- PRE-CONDITION: in the call (uUnrefined r co tv ty ty'), we know that
---     co :: tv:=:ty
+-- PRE-CONDITION: in the call (uUnrefined r co tv1 ty2 ty2'), we know that
+--     co :: tv1:=:ty2
 
 uUnrefined subst co tv1 ty2 ty2'
   | Just ty2'' <- tcView ty2'
@@ -379,7 +401,7 @@ uUnrefined subst co tv1 ty2 (TyVarTy tv2)
   = return subst
 
     -- Check to see whether tv2 is refined
-  | Just (co',ty') <- lookupVarEnv subst tv2
+  | Just (co',ty') <- lookupVarEnv subst tv2   -- co' :: tv2:=:ty'
   = uUnrefined subst (mkTransCoercion co co') tv1 ty' ty'
 
   -- So both are unrefined; next, see if the kinds force the direction
@@ -409,9 +431,12 @@ uUnrefined subst co tv1 ty2 (TyVarTy tv2)
     ty1 = TyVarTy tv1
     k1 = tyVarKind tv1
     k2 = tyVarKind tv2
-    bind swap tv ty = return (extendVarEnv subst tv (co',ty))
+    bind swap tv ty = 
+        ASSERT2( (coercionKindPredTy co1 `tcEqType` mkCoKind (mkTyVarTy tv) ty)
+               , (text "Refinement invariant failure: co = " <+> ppr co  <+> ppr (coercionKindPredTy co) $$ text "subst = " <+> ppr tv <+> ppr (mkCoKind (mkTyVarTy tv) ty)))
+        return (extendVarEnv subst tv (co1,ty))
       where
-        co' = if swap then mkSymCoercion co else co
+        co1 = if swap then mkSymCoercion co else co
 
 uUnrefined subst co tv1 ty2 ty2'       -- ty2 is not a type variable
   | tv1 `elemVarSet` substTvSet subst (tyVarsOfType ty2')
@@ -435,7 +460,9 @@ substTvSet subst tvs
                Just (_,ty) -> substTvSet subst (tyVarsOfType ty)
 
 bindTv subst co tv ty  -- ty is not a type variable
-  = do { b <- tvBindFlag tv
+  = ASSERT2( (coercionKindPredTy co `tcEqType` mkCoKind (mkTyVarTy tv) ty), 
+          (text "Refinement invariant failure: co = " <+> ppr co  <+> ppr (coercionKindPredTy co) $$ text "subst = " <+> ppr tv <+> ppr (mkCoKind (mkTyVarTy tv) ty))  )
+    do  { b <- tvBindFlag tv
        ; case b of
            Skolem   -> failWith (misMatch (TyVarTy tv) ty)
            WildCard -> return subst