Store a SrcSpan instead of a SrcLoc inside a Name

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

diff --git a/compiler/typecheck/TcMType.lhs b/compiler/typecheck/TcMType.lhs
index 23c3381..6e72536 100644 (file)
--- a/compiler/typecheck/TcMType.lhs
+++ b/compiler/typecheck/TcMType.lhs
@@ -1,9 +1,12 @@
 %
 %

+% (c) The University of Glasgow 2006

 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %

-\section{Monadic type operations}

 
 

-This module contains monadic operations over types that contain mutable type variables
+Monadic type operations
+
+This module contains monadic operations over types that contain
+mutable type variables

 
 \begin{code}
 module TcMType (
 
 \begin{code}
 module TcMType (

@@ -44,9 +47,10 @@ module TcMType (
   --------------------------------
   -- Zonking
   zonkType, zonkTcPredType, 
   --------------------------------
   -- Zonking
   zonkType, zonkTcPredType, 

-  zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV, zonkQuantifiedTyVar,
+  zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV, 
+  zonkQuantifiedTyVar, zonkQuantifiedTyVars,

   zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType,
   zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType,

-  zonkTcKindToKind, zonkTcKind,
+  zonkTcKindToKind, zonkTcKind, zonkTopTyVar,

 
   readKindVar, writeKindVar
 
 
   readKindVar, writeKindVar
 

@@ -54,60 +58,31 @@ module TcMType (
 
 #include "HsVersions.h"
 
 
 #include "HsVersions.h"
 

-

 -- friends:
 -- friends:

-import TypeRep         ( Type(..), PredType(..),  -- Friend; can see representation
-                         ThetaType
-                       ) 
-import TcType          ( TcType, TcThetaType, TcTauType, TcPredType,
-                         TcTyVarSet, TcKind, TcTyVar, TcTyVarDetails(..), 
-                         MetaDetails(..), SkolemInfo(..), BoxInfo(..), 
-                         BoxyTyVar, BoxyType, UserTypeCtxt(..), kindVarRef,
-                         mkKindVar, isMetaTyVar, isSigTyVar, metaTvRef,
-                         tcCmpPred, isClassPred, tcGetTyVar,
-                         tcSplitPhiTy, tcSplitPredTy_maybe,
-                         tcSplitAppTy_maybe,  
-                         tcValidInstHeadTy, tcSplitForAllTys,
-                         tcIsTyVarTy, tcSplitSigmaTy, 
-                         isUnLiftedType, isIPPred, 
-                         typeKind, isSkolemTyVar,
-                         mkAppTy, mkTyVarTy, mkTyVarTys, 
-                         tyVarsOfPred, getClassPredTys_maybe,
-                         tyVarsOfType, tyVarsOfTypes, tcView,
-                         pprPred, pprTheta, pprClassPred )
-import Type            ( Kind, KindVar, 
-                         isLiftedTypeKind, isSubArgTypeKind, isSubOpenTypeKind,
-                         liftedTypeKind, defaultKind
-                       )
-import Type            ( TvSubst, zipTopTvSubst, substTy )
-import Coercion                ( mkCoKind )
-import Class           ( Class, classArity, className )
-import TyCon           ( TyCon, isSynTyCon, isUnboxedTupleTyCon, 
-                         tyConArity, tyConName )
-import Var             ( TyVar, tyVarKind, tyVarName, isTcTyVar, 
-                         mkTyVar, mkTcTyVar, tcTyVarDetails,
-                         CoVar, mkCoVar )
-
-       -- Assertions
-#ifdef DEBUG
-import TcType          ( isFlexi, isBoxyTyVar, isImmutableTyVar )
-import Type            ( isSubKind )
-#endif
+import TypeRep
+import TcType
+import Type
+import Coercion
+import Class
+import TyCon
+import Var

 
 -- others:
 import TcRnMonad          -- TcType, amongst others
 
 -- others:
 import TcRnMonad          -- TcType, amongst others

-import FunDeps         ( grow, checkInstCoverage )
-import Name            ( Name, setNameUnique, mkSysTvName )
+import FunDeps
+import Name

 import VarSet
 import VarSet

-import DynFlags                ( dopt, DynFlag(..) )
-import Util            ( nOfThem, isSingleton, notNull )
-import ListSetOps      ( removeDups )
-import UniqSupply      ( uniqsFromSupply )
+import ErrUtils
+import DynFlags
+import Util
+import Maybes
+import ListSetOps
+import UniqSupply
+import SrcLoc

 import Outputable
 
 import Outputable
 

-import Control.Monad   ( when )
+import Control.Monad   ( when, unless )

 import Data.List       ( (\\) )
 import Data.List       ( (\\) )

-

 \end{code}
 
 
 \end{code}
 
 

@@ -186,19 +161,30 @@ tcSkolSigTyVars :: SkolemInfo -> [TyVar] -> [TcTyVar]
 tcSkolSigTyVars info tyvars = [ mkSkolTyVar (tyVarName tv) (tyVarKind tv) info
                              | tv <- tyvars ]
 
 tcSkolSigTyVars info tyvars = [ mkSkolTyVar (tyVarName tv) (tyVarKind tv) info
                              | tv <- tyvars ]
 

-tcInstSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
--- Instantiate a type with fresh skolem constants
-tcInstSkolType info ty = tcInstType (tcInstSkolTyVars info) ty
-
-tcInstSkolTyVar :: SkolemInfo -> TyVar -> TcM TcTyVar
-tcInstSkolTyVar info tyvar
+tcInstSkolTyVar :: SkolemInfo -> Maybe SrcSpan -> TyVar -> TcM TcTyVar
+-- Instantiate the tyvar, using 
+--     * the occ-name and kind of the supplied tyvar, 
+--     * the unique from the monad,
+--     * the location either from the tyvar (mb_loc = Nothing)
+--       or from mb_loc (Just loc)
+tcInstSkolTyVar info mb_loc tyvar

   = do { uniq <- newUnique
   = do { uniq <- newUnique

-       ; let name = setNameUnique (tyVarName tyvar) uniq
-             kind = tyVarKind tyvar
-       ; return (mkSkolTyVar name kind info) }
+       ; let old_name = tyVarName tyvar
+             kind     = tyVarKind tyvar
+             loc      = mb_loc `orElse` getSrcSpan old_name
+             new_name = mkInternalName uniq (nameOccName old_name) loc
+       ; return (mkSkolTyVar new_name kind info) }

 
 tcInstSkolTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]
 
 tcInstSkolTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]

-tcInstSkolTyVars info tyvars = mapM (tcInstSkolTyVar info) tyvars
+-- Get the location from the monad
+tcInstSkolTyVars info tyvars 
+  = do         { span <- getSrcSpanM
+       ; mapM (tcInstSkolTyVar info (Just span)) tyvars }
+
+tcInstSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
+-- Instantiate a type with fresh skolem constants
+-- Binding location comes from the monad
+tcInstSkolType info ty = tcInstType (tcInstSkolTyVars info) ty

 \end{code}
 
 
 \end{code}
 
 

@@ -301,9 +287,14 @@ tcInstTyVars tyvars
 %************************************************************************
 
 \begin{code}
 %************************************************************************
 
 \begin{code}

-tcInstSigTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]
--- Instantiate with meta SigTvs
-tcInstSigTyVars skol_info tyvars 
+tcInstSigTyVars :: Bool -> SkolemInfo -> [TyVar] -> TcM [TcTyVar]
+-- Instantiate with skolems or meta SigTvs; depending on use_skols
+-- Always take location info from the supplied tyvars
+tcInstSigTyVars use_skols skol_info tyvars 
+  | use_skols
+  = mapM (tcInstSkolTyVar skol_info Nothing) tyvars
+
+  | otherwise

   = mapM (instMetaTyVar (SigTv skol_info)) tyvars
 
 zonkSigTyVar :: TcTyVar -> TcM TcTyVar
   = mapM (instMetaTyVar (SigTv skol_info)) tyvars
 
 zonkSigTyVar :: TcTyVar -> TcM TcTyVar

@@ -368,7 +359,8 @@ data LookupTyVarResult      -- The result of a lookupTcTyVar call
 
 lookupTcTyVar :: TcTyVar -> TcM LookupTyVarResult
 lookupTcTyVar tyvar 
 
 lookupTcTyVar :: TcTyVar -> TcM LookupTyVarResult
 lookupTcTyVar tyvar 

-  = case details of
+  = ASSERT2( isTcTyVar tyvar, ppr tyvar )
+    case details of

       SkolemTv _   -> return (DoneTv details)
       MetaTv _ ref -> do { meta_details <- readMutVar ref
                         ; case meta_details of
       SkolemTv _   -> return (DoneTv details)
       MetaTv _ ref -> do { meta_details <- readMutVar ref
                         ; case meta_details of

@@ -430,7 +422,7 @@ zonkTcTyVarsAndFV tyvars = mappM zonkTcTyVar tyvars `thenM` \ tys ->
                           returnM (tyVarsOfTypes tys)
 
 zonkTcTyVar :: TcTyVar -> TcM TcType
                           returnM (tyVarsOfTypes tys)
 
 zonkTcTyVar :: TcTyVar -> TcM TcType

-zonkTcTyVar tyvar = ASSERT( isTcTyVar tyvar )
+zonkTcTyVar tyvar = ASSERT2( isTcTyVar tyvar, ppr tyvar)

                    zonk_tc_tyvar (\ tv -> returnM (TyVarTy tv)) tyvar
 \end{code}
 
                    zonk_tc_tyvar (\ tv -> returnM (TyVarTy tv)) tyvar
 \end{code}
 

@@ -468,17 +460,48 @@ zonkTcPredType (EqPred t1 t2)
                     are used at the end of type checking
 
 \begin{code}
                     are used at the end of type checking
 
 \begin{code}

+zonkTopTyVar :: TcTyVar -> TcM TcTyVar
+-- zonkTopTyVar is used, at the top level, on any un-instantiated meta type variables
+-- to default the kind of ? and ?? etc to *.  This is important to ensure that
+-- instance declarations match.  For example consider
+--     instance Show (a->b)
+--     foo x = show (\_ -> True)
+-- Then we'll get a constraint (Show (p ->q)) where p has argTypeKind (printed ??), 
+-- and that won't match the typeKind (*) in the instance decl.
+--
+-- Because we are at top level, no further constraints are going to affect these
+-- type variables, so it's time to do it by hand.  However we aren't ready
+-- to default them fully to () or whatever, because the type-class defaulting
+-- rules have yet to run.
+
+zonkTopTyVar tv
+  | k `eqKind` default_k = return tv
+  | otherwise
+  = do { tv' <- newFlexiTyVar default_k
+       ; writeMetaTyVar tv (mkTyVarTy tv') 
+       ; return tv' }
+  where
+    k = tyVarKind tv
+    default_k = defaultKind k
+
+zonkQuantifiedTyVars :: [TcTyVar] -> TcM [TyVar]
+zonkQuantifiedTyVars = mappM zonkQuantifiedTyVar
+

 zonkQuantifiedTyVar :: TcTyVar -> TcM TyVar
 -- zonkQuantifiedTyVar is applied to the a TcTyVar when quantifying over it.
 zonkQuantifiedTyVar :: TcTyVar -> TcM TyVar
 -- zonkQuantifiedTyVar is applied to the a TcTyVar when quantifying over it.

--- It might be a meta TyVar, in which case we freeze it into an ordinary TyVar.
--- When we do this, we also default the kind -- see notes with Kind.defaultKind
+--
+-- The quantified type variables often include meta type variables
+-- we want to freeze them into ordinary type variables, and
+-- default their kind (e.g. from OpenTypeKind to TypeKind)
+--                     -- see notes with Kind.defaultKind

 -- The meta tyvar is updated to point to the new regular TyVar.  Now any 
 -- bound occurences of the original type variable will get zonked to 
 -- the immutable version.
 --
 -- We leave skolem TyVars alone; they are immutable.
 zonkQuantifiedTyVar tv
 -- The meta tyvar is updated to point to the new regular TyVar.  Now any 
 -- bound occurences of the original type variable will get zonked to 
 -- the immutable version.
 --
 -- We leave skolem TyVars alone; they are immutable.
 zonkQuantifiedTyVar tv

-  | isSkolemTyVar tv = return tv
+  | ASSERT( isTcTyVar tv ) 
+    isSkolemTyVar tv = return tv

        -- It might be a skolem type variable, 
        -- for example from a user type signature
 
        -- It might be a skolem type variable, 
        -- for example from a user type signature
 

@@ -687,7 +710,6 @@ checkValidType ctxt ty
                 ConArgCtxt _   -> Rank 1       -- We are given the type of the entire
                                                -- constructor, hence rank 1
                 ForSigCtxt _   -> Rank 1
                 ConArgCtxt _   -> Rank 1       -- We are given the type of the entire
                                                -- constructor, hence rank 1
                 ForSigCtxt _   -> Rank 1

-                RuleSigCtxt _  -> Rank 1

                 SpecInstCtxt   -> Rank 1
 
        actual_kind = typeKind ty
                 SpecInstCtxt   -> Rank 1
 
        actual_kind = typeKind ty

@@ -804,12 +826,15 @@ check_tau_type rank ubx_tup ty@(TyConApp tc tys)
                --      type Foo a = Tree [a]
                --      f :: Foo a b -> ...
        ; case tcView ty of
                --      type Foo a = Tree [a]
                --      f :: Foo a b -> ...
        ; case tcView ty of

-            Just ty' -> check_tau_type rank ubx_tup ty'        -- Check expansion
-            Nothing  -> failWithTc arity_msg
+            Just ty' -> check_tau_type rank ubx_tup ty' -- Check expansion
+            Nothing -> unless (isOpenTyCon tc           -- No expansion if open
+                               && tyConArity tc <= length tys) $
+                         failWithTc arity_msg

 
        ; gla_exts <- doptM Opt_GlasgowExts
 
        ; gla_exts <- doptM Opt_GlasgowExts

-       ; if gla_exts then
-       -- If -fglasgow-exts then don't check the type arguments
+       ; if gla_exts && not (isOpenTyCon tc) then
+       -- If -fglasgow-exts then don't check the type arguments of 
+       -- *closed* synonyms.

        -- This allows us to instantiate a synonym defn with a 
        -- for-all type, or with a partially-applied type synonym.
        --      e.g.   type T a b = a
        -- This allows us to instantiate a synonym defn with a 
        -- for-all type, or with a partially-applied type synonym.
        --      e.g.   type T a b = a

@@ -902,14 +927,14 @@ check_valid_theta ctxt theta
 
 -------------------------
 check_pred_ty dflags ctxt pred@(ClassP cls tys)
 
 -------------------------
 check_pred_ty dflags ctxt pred@(ClassP cls tys)

-  =    -- Class predicates are valid in all contexts
-    checkTc (arity == n_tys) arity_err         `thenM_`
-
-       -- Check the form of the argument types
-    mappM_ check_arg_type tys                          `thenM_`
-    checkTc (check_class_pred_tys dflags ctxt tys)
-           (predTyVarErr pred $$ how_to_allow)
-
+  = do {       -- Class predicates are valid in all contexts
+       ; checkTc (arity == n_tys) arity_err
+
+               -- Check the form of the argument types
+       ; mappM_ check_arg_type tys
+       ; checkTc (check_class_pred_tys dflags ctxt tys)
+                (predTyVarErr pred $$ how_to_allow)
+       }

   where
     class_name = className cls
     arity      = classArity cls
   where
     class_name = className cls
     arity      = classArity cls

@@ -917,10 +942,23 @@ check_pred_ty dflags ctxt pred@(ClassP cls tys)
     arity_err  = arityErr "Class" class_name arity n_tys
     how_to_allow = parens (ptext SLIT("Use -fglasgow-exts to permit this"))
 
     arity_err  = arityErr "Class" class_name arity n_tys
     how_to_allow = parens (ptext SLIT("Use -fglasgow-exts to permit this"))
 

+check_pred_ty dflags ctxt pred@(EqPred ty1 ty2)
+  = do {       -- Equational constraints are valid in all contexts if indexed
+               -- types are permitted
+       ; checkTc (dopt Opt_IndexedTypes dflags) (eqPredTyErr pred)
+
+               -- Check the form of the argument types
+       ; check_eq_arg_type ty1
+       ; check_eq_arg_type ty2
+       }
+  where 
+    check_eq_arg_type = check_poly_type (Rank 0) UT_NotOk
+

 check_pred_ty dflags SigmaCtxt (IParam _ ty) = check_arg_type ty
 check_pred_ty dflags SigmaCtxt (IParam _ ty) = check_arg_type ty

-       -- Implicit parameters only allows in type
+       -- Implicit parameters only allowed in type

        -- signatures; not in instance decls, superclasses etc
        -- signatures; not in instance decls, superclasses etc

-       -- The reason for not allowing implicit params in instances is a bit subtle
+       -- The reason for not allowing implicit params in instances is a bit
+       -- subtle.

        -- If we allowed        instance (?x::Int, Eq a) => Foo [a] where ...
        -- then when we saw (e :: (?x::Int) => t) it would be unclear how to 
        -- discharge all the potential usas of the ?x in e.   For example, a
        -- If we allowed        instance (?x::Int, Eq a) => Foo [a] where ...
        -- then when we saw (e :: (?x::Int) => t) it would be unclear how to 
        -- discharge all the potential usas of the ?x in e.   For example, a

@@ -1013,7 +1051,9 @@ even in a scope where b is in scope.
 
 \begin{code}
 checkFreeness forall_tyvars theta
 
 \begin{code}
 checkFreeness forall_tyvars theta

-  = mappM_ complain (filter is_free theta)
+  = do { gla_exts <- doptM Opt_GlasgowExts
+       ; if gla_exts then return ()    -- New!  Oct06
+         else mappM_ complain (filter is_free theta) }

   where    
     is_free pred     =  not (isIPPred pred)
                     && not (any bound_var (varSetElems (tyVarsOfPred pred)))
   where    
     is_free pred     =  not (isIPPred pred)
                     && not (any bound_var (varSetElems (tyVarsOfPred pred)))

@@ -1033,6 +1073,9 @@ checkThetaCtxt ctxt theta
          ptext SLIT("While checking") <+> pprSourceTyCtxt ctxt ]
 
 badPredTyErr sty = ptext SLIT("Illegal constraint") <+> pprPred sty
          ptext SLIT("While checking") <+> pprSourceTyCtxt ctxt ]
 
 badPredTyErr sty = ptext SLIT("Illegal constraint") <+> pprPred sty

+eqPredTyErr  sty = ptext SLIT("Illegal equational constraint") <+> pprPred sty
+                  $$
+                  parens (ptext SLIT("Use -findexed-types to permit this"))

 predTyVarErr pred  = sep [ptext SLIT("Non type-variable argument"),
                          nest 2 (ptext SLIT("in the constraint:") <+> pprPred pred)]
 dupPredWarn dups   = ptext SLIT("Duplicate constraint(s):") <+> pprWithCommas pprPred (map head dups)
 predTyVarErr pred  = sep [ptext SLIT("Non type-variable argument"),
                          nest 2 (ptext SLIT("in the constraint:") <+> pprPred pred)]
 dupPredWarn dups   = ptext SLIT("Duplicate constraint(s):") <+> pprWithCommas pprPred (map head dups)

@@ -1093,8 +1136,8 @@ check_inst_head dflags clas tys
   where
     (first_ty : _) = tys
 
   where
     (first_ty : _) = tys
 

-    head_shape_msg = parens (text "The instance type must be of form (T a b c)" $$
-                            text "where T is not a synonym, and a,b,c are distinct type variables")
+    head_shape_msg = parens (text "The instance type must be of form (T a1 ... an)" $$
+                            text "where T is not a synonym, and a1 ... an are distinct type *variables*")

 
        -- For now, I only allow tau-types (not polytypes) in 
        -- the head of an instance decl.  
 
        -- For now, I only allow tau-types (not polytypes) in 
        -- the head of an instance decl.  

@@ -1129,17 +1172,22 @@ checkValidInstance tyvars theta clas inst_tys
        -- Check that instance inference will terminate (if we care)
        -- For Haskell 98, checkValidTheta has already done that
        ; when (gla_exts && not undecidable_ok) $
        -- Check that instance inference will terminate (if we care)
        -- For Haskell 98, checkValidTheta has already done that
        ; when (gla_exts && not undecidable_ok) $

-              checkInstTermination theta inst_tys
+         mapM_ addErrTc (checkInstTermination inst_tys theta)

        
        -- The Coverage Condition
        ; checkTc (undecidable_ok || checkInstCoverage clas inst_tys)
                  (instTypeErr (pprClassPred clas inst_tys) msg)
        }
   where
        
        -- The Coverage Condition
        ; checkTc (undecidable_ok || checkInstCoverage clas inst_tys)
                  (instTypeErr (pprClassPred clas inst_tys) msg)
        }
   where

-    msg  = parens (ptext SLIT("the Coverage Condition fails for one of the functional dependencies"))
+    msg  = parens (vcat [ptext SLIT("the Coverage Condition fails for one of the functional dependencies;"),
+                        undecidableMsg])

 \end{code}
 
 \end{code}
 

-Termination test: each assertion in the context satisfies
+Termination test: the so-called "Paterson conditions" (see Section 5 of
+"Understanding functionsl dependencies via Constraint Handling Rules, 
+JFP Jan 2007).
+
+We check that each assertion in the context satisfies:

  (1) no variable has more occurrences in the assertion than in the head, and
  (2) the assertion has fewer constructors and variables (taken together
      and counting repetitions) than the head.
  (1) no variable has more occurrences in the assertion than in the head, and
  (2) the assertion has fewer constructors and variables (taken together
      and counting repetitions) than the head.

@@ -1153,20 +1201,19 @@ The underlying idea is that
 
 
 \begin{code}
 
 
 \begin{code}

-checkInstTermination :: ThetaType -> [TcType] -> TcM ()
-checkInstTermination theta tys
-  = do { mappM_ (check_nomore (fvTypes tys))    theta
-       ; mappM_ (check_smaller (sizeTypes tys)) theta }
-
-check_nomore :: [TyVar] -> PredType -> TcM ()
-check_nomore fvs pred
-  = checkTc (null (fvPred pred \\ fvs))
-           (predUndecErr pred nomoreMsg $$ parens undecidableMsg)
-
-check_smaller :: Int -> PredType -> TcM ()
-check_smaller n pred
-  = checkTc (sizePred pred < n)
-           (predUndecErr pred smallerMsg $$ parens undecidableMsg)
+checkInstTermination :: [TcType] -> ThetaType -> [Message]
+checkInstTermination tys theta
+  = mapCatMaybes check theta
+  where
+   fvs  = fvTypes tys
+   size = sizeTypes tys
+   check pred 
+      | not (null (fvPred pred \\ fvs)) 
+      = Just (predUndecErr pred nomoreMsg $$ parens undecidableMsg)
+      | sizePred pred >= size
+      = Just (predUndecErr pred smallerMsg $$ parens undecidableMsg)
+      | otherwise
+      = Nothing

 
 predUndecErr pred msg = sep [msg,
                        nest 2 (ptext SLIT("in the constraint:") <+> pprPred pred)]
 
 predUndecErr pred msg = sep [msg,
                        nest 2 (ptext SLIT("in the constraint:") <+> pprPred pred)]