X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcEnv.lhs;h=787616aa3e60c0c9f6a106cae148ffe898c85371;hb=940524aec90652b5ef81789c9a453c57c0e42cc9;hp=2e3b80ba7e356008476191881a40f513de80dba1;hpb=1166c7d62f3fa9acd2084c90df6585cbbf868ceb;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index 2e3b80b..787616a 100644
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -17,7 +17,7 @@ module TcEnv(
 	tcLookupLocatedGlobal,	tcLookupGlobal, 
 	tcLookupField, tcLookupTyCon, tcLookupClass, tcLookupDataCon,
 	tcLookupLocatedGlobalId, tcLookupLocatedTyCon,
-	tcLookupLocatedClass, 
+	tcLookupLocatedClass, tcLookupFamInst,
 	
 	-- Local environment
 	tcExtendKindEnv, tcExtendKindEnvTvs,
@@ -55,12 +55,12 @@ import TcMType
 import TcType
 import TcGadt
 import qualified Type
-import Id
 import Var
 import VarSet
 import VarEnv
 import RdrName
 import InstEnv
+import FamInstEnv
 import DataCon
 import TyCon
 import Class
@@ -157,6 +157,33 @@ tcLookupLocatedClass = addLocM tcLookupClass
 
 tcLookupLocatedTyCon :: Located Name -> TcM TyCon
 tcLookupLocatedTyCon = addLocM tcLookupTyCon
+
+-- Look up the representation tycon of a family instance.
+-- 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 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}
 
 %************************************************************************
@@ -400,6 +427,9 @@ refineEnvironment :: Refinement -> TcM a -> TcM a
 -- I don't think I have to refine the set of global type variables in scope
 -- Reason: the refinement never increases that set
 refineEnvironment reft thing_inside
+  | isEmptyRefinement reft		-- Common case
+  = thing_inside
+  | otherwise
   = do	{ env <- getLclEnv
 	; let le' = mapNameEnv refine (tcl_env env)
  	; setLclEnv (env {tcl_env = le'}) thing_inside }
@@ -605,7 +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
@@ -619,12 +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
@@ -653,4 +683,11 @@ notFound name
 wrongThingErr expected thing name
   = failWithTc (pprTcTyThingCategory thing <+> quotes (ppr name) <+> 
 		ptext SLIT("used as a") <+> text expected)
+
+famInstNotFound tycon tys what
+  = failWithTc (msg <+> quotes (pprTypeApp (ppr tycon) tys))
+  where
+    msg = ptext $ if length what > 1 
+		  then SLIT("More than one family instance for")
+		  else SLIT("No family instance exactly matching")
 \end{code}