Implement -XFunctionalDependencies

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

diff --git a/compiler/typecheck/TcTyClsDecls.lhs b/compiler/typecheck/TcTyClsDecls.lhs
index 7623b19..8a4e05b 100644 (file)
--- a/compiler/typecheck/TcTyClsDecls.lhs
+++ b/compiler/typecheck/TcTyClsDecls.lhs
@@ -1061,10 +1061,12 @@ checkValidClass cls
   = do {       -- CHECK ARITY 1 FOR HASKELL 1.4
          gla_exts <- doptM Opt_GlasgowExts
        ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
+       ; fundep_classes <- doptM Opt_FunctionalDependencies
 
        -- Check that the class is unary, unless GlaExs
        ; checkTc (notNull tyvars) (nullaryClassErr cls)
        ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
+       ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
 
        -- Check the super-classes
        ; checkValidTheta (ClassSCCtxt (className cls)) theta
@@ -1078,7 +1080,7 @@ checkValidClass cls
        ; checkTc (unary || no_generics) (genericMultiParamErr cls)
        }
   where
-    (tyvars, theta, _, op_stuff) = classBigSig cls
+    (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
     unary      = isSingleton tyvars
     no_generics = null [() | (_, GenDefMeth) <- op_stuff]
 
@@ -1141,6 +1143,10 @@ classArityErr cls
   = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
          parens (ptext SLIT("Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
 
+classFunDepsErr cls
+  = vcat [ptext SLIT("Fundeps in class") <+> quotes (ppr cls),
+         parens (ptext SLIT("Use -XFunctionalDependencies to allow fundeps"))]
+
 noClassTyVarErr clas op
   = sep [ptext SLIT("The class method") <+> quotes (ppr op),
         ptext SLIT("mentions none of the type variables of the class") <+>