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 ca5ca0e..6e72536 100644 (file)
--- a/compiler/typecheck/TcMType.lhs
+++ b/compiler/typecheck/TcMType.lhs
@@ -161,7 +161,7 @@ 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 ]
 

-tcInstSkolTyVar :: SkolemInfo -> Maybe SrcLoc -> TyVar -> TcM TcTyVar
+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,
 -- Instantiate the tyvar, using 
 --     * the occ-name and kind of the supplied tyvar, 
 --     * the unique from the monad,

@@ -171,7 +171,7 @@ tcInstSkolTyVar info mb_loc tyvar
   = do { uniq <- newUnique
        ; let old_name = tyVarName tyvar
              kind     = tyVarKind tyvar
   = do { uniq <- newUnique
        ; let old_name = tyVarName tyvar
              kind     = tyVarKind tyvar

-             loc      = mb_loc `orElse` getSrcLoc old_name
+             loc      = mb_loc `orElse` getSrcSpan old_name

              new_name = mkInternalName uniq (nameOccName old_name) loc
        ; return (mkSkolTyVar new_name kind info) }
 
              new_name = mkInternalName uniq (nameOccName old_name) loc
        ; return (mkSkolTyVar new_name kind info) }
 

@@ -179,7 +179,7 @@ tcInstSkolTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]
 -- Get the location from the monad
 tcInstSkolTyVars info tyvars 
   = do         { span <- getSrcSpanM
 -- Get the location from the monad
 tcInstSkolTyVars info tyvars 
   = do         { span <- getSrcSpanM

-       ; mapM (tcInstSkolTyVar info (Just (srcSpanStart span))) tyvars }
+       ; mapM (tcInstSkolTyVar info (Just span)) tyvars }

 
 tcInstSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
 -- Instantiate a type with fresh skolem constants
 
 tcInstSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
 -- Instantiate a type with fresh skolem constants

@@ -422,7 +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}
 

@@ -1136,8 +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.  

@@ -1183,7 +1183,11 @@ checkValidInstance tyvars theta clas inst_tys
                         undecidableMsg])
 \end{code}
 
                         undecidableMsg])
 \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.