Warning fix for unused and redundant imports

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

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index d59278a..6d4cd46 100644 (file)
--- 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
@@ -160,15 +159,30 @@ tcLookupLocatedTyCon :: Located Name -> TcM TyCon
 tcLookupLocatedTyCon = addLocM tcLookupTyCon
 
 -- Look up the representation tycon of a family instance.
---
-tcLookupFamInst :: TyCon -> [Type] -> TcM TyCon
+-- Return the rep tycon and the corresponding rep args
+tcLookupFamInst :: TyCon -> [Type] -> TcM (TyCon, [Type])
 tcLookupFamInst tycon tys
+  | not (isOpenTyCon tycon)
+  = return (tycon, tys)
+  | otherwise
   = do { env <- getGblEnv
        ; eps <- getEps
        ; let instEnv = (eps_fam_inst_env eps, tcg_fam_inst_env env)
-       ; case lookupFamInstEnvExact instEnv tycon tys of
-          Nothing      -> famInstNotFound tycon tys
-          Just famInst -> return $ famInstTyCon famInst
+       ; case lookupFamInstEnv instEnv tycon tys of
+
+          [(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
+                 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
        }
 \end{code}
 
@@ -635,7 +649,7 @@ 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.
 
@@ -670,8 +684,10 @@ wrongThingErr expected thing name
   = failWithTc (pprTcTyThingCategory thing <+> quotes (ppr name) <+> 
                ptext SLIT("used as a") <+> text expected)
 
-famInstNotFound tycon tys
-  = failWithTc (quotes famInst <+> ptext SLIT("is not in scope"))
+famInstNotFound tycon tys what
+  = failWithTc (msg <+> quotes (pprTypeApp (ppr tycon) tys))
   where
-    famInst = ppr tycon <+> hsep (map pprParendType tys)
+    msg = ptext $ if length what > 1 
+                 then SLIT("More than one family instance for")
+                 else SLIT("No family instance exactly matching")
 \end{code}