X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcTyClsDecls.lhs;h=834bedcc3352b1f8bf5e9f1c22f87d585ec403cf;hb=f8f8449e1e54d0da1d16536070f18709b9e95af4;hp=8ab053ecb249029c657fbbdb993b28b8baa4e787;hpb=ab22f4e6456820c1b5169d75f5975a94e61f54ce;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcTyClsDecls.lhs b/compiler/typecheck/TcTyClsDecls.lhs
index 8ab053e..834bedc 100644
--- a/compiler/typecheck/TcTyClsDecls.lhs
+++ b/compiler/typecheck/TcTyClsDecls.lhs
@@ -24,6 +24,7 @@ import TcClassDcl
 import TcHsType
 import TcMType
 import TcType
+import FunDeps
 import Type
 import Generics
 import Class
@@ -1043,8 +1044,13 @@ checkValidClass cls
 	; checkValidType (FunSigCtxt op_name) tau
 
 		-- Check that the type mentions at least one of
-		-- the class type variables
-	; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
+		-- the class type variables...or at least one reachable
+		-- from one of the class variables.  Example: tc223
+		--   class Error e => Game b mv e | b -> mv e where
+		--      newBoard :: MonadState b m => m ()
+		-- Here, MonadState has a fundep m->b, so newBoard is fine
+	; let grown_tyvars = grow theta (mkVarSet tyvars)
+	; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
 	          (noClassTyVarErr cls sel_id)
 
 		-- Check that for a generic method, the type of 
@@ -1150,7 +1156,7 @@ newtypeFieldErr con_name n_flds
 badSigTyDecl tc_name
   = vcat [ ptext SLIT("Illegal kind signature") <+>
 	   quotes (ppr tc_name)
-	 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
+	 , nest 2 (parens $ ptext SLIT("Use -findexed-types to allow indexed types")) ]
 
 badKindSigCtxt tc_name
   = vcat [ ptext SLIT("Illegal context in kind signature") <+>
@@ -1160,7 +1166,7 @@ badKindSigCtxt tc_name
 badIdxTyDecl tc_name
   = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
 	   quotes (ppr tc_name)
-	 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
+	 , nest 2 (parens $ ptext SLIT("Use -findexed-types to allow indexed types")) ]
 
 badGadtIdxTyDecl tc_name
   = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>