X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcEnv.lhs;h=787616aa3e60c0c9f6a106cae148ffe898c85371;hb=940524aec90652b5ef81789c9a453c57c0e42cc9;hp=e1b9bd31b70c912cf74f7b61754aa43d89c77fb6;hpb=84923cc7de2a93c22a2f72daf9ac863959efae13;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index e1b9bd3..787616a 100644
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -55,7 +55,6 @@ import TcMType
 import TcType
 import TcGadt
 import qualified Type
-import Id
 import Var
 import VarSet
 import VarEnv
@@ -170,10 +169,18 @@ tcLookupFamInst tycon tys
        ; eps <- getEps
        ; let instEnv = (eps_fam_inst_env eps, tcg_fam_inst_env env)
        ; case lookupFamInstEnv instEnv tycon tys of
-	   [(subst,fam_inst)] -> return (rep_tc, substTyVars subst (tyConTyVars rep_tc))
+
+	   [(subst, fam_inst)] | variable_only_subst -> 
+	     return (rep_tc, substTyVars subst (tyConTyVars rep_tc))
 		where	-- NB: assumption is that (tyConTyVars rep_tc) is in 
 			--     the domain of the substitution
-		  rep_tc = famInstTyCon fam_inst 
+		  rep_tc              = famInstTyCon fam_inst
+		  subst_domain        = varEnvElts . getTvSubstEnv $ subst
+		  tvs		      = map (Type.getTyVar "tcLookupFamInst") 
+					    subst_domain
+		  variable_only_subst = all Type.isTyVarTy subst_domain &&
+					sizeVarSet (mkVarSet tvs) == length tvs
+					-- renaming may have no repetitions
 
 	   other -> famInstNotFound tycon tys other
        }
@@ -628,7 +635,7 @@ Make a name for the dict fun for an instance decl.  It's an *external*
 name, like otber top-level names, and hence must be made with newGlobalBinder.
 
 \begin{code}
-newDFunName :: Class -> [Type] -> SrcLoc -> TcM Name
+newDFunName :: Class -> [Type] -> SrcSpan -> TcM Name
 newDFunName clas (ty:_) loc
   = do	{ index   <- nextDFunIndex
 	; is_boot <- tcIsHsBoot
@@ -642,12 +649,12 @@ newDFunName clas (ty:_) loc
 newDFunName clas [] loc = pprPanic "newDFunName" (ppr clas <+> ppr loc)
 \end{code}
 
-Make a name for the representation tycon of a data/newtype instance.  It's an
+Make a name for the representation tycon of a family instance.  It's an
 *external* name, like otber top-level names, and hence must be made with
 newGlobalBinder.
 
 \begin{code}
-newFamInstTyConName :: Name -> SrcLoc -> TcM Name
+newFamInstTyConName :: Name -> SrcSpan -> TcM Name
 newFamInstTyConName tc_name loc
   = do	{ index <- nextDFunIndex
 	; mod   <- getModule
@@ -678,9 +685,9 @@ wrongThingErr expected thing name
 		ptext SLIT("used as a") <+> text expected)
 
 famInstNotFound tycon tys what
-  = failWithTc (msg <+> quotes (ppr tycon <+> hsep (map pprParendType tys)))
+  = failWithTc (msg <+> quotes (pprTypeApp (ppr tycon) tys))
   where
-    msg = case what of
-		[] -> ptext SLIT("No instance for")
-		xs -> ptext SLIT("More than one instance for")
+    msg = ptext $ if length what > 1 
+		  then SLIT("More than one family instance for")
+		  else SLIT("No family instance exactly matching")
 \end{code}