X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=compiler%2Ftypecheck%2FTcEnv.lhs;h=0f9bf231c8c66b3c2475e73630a82bb4a5657533;hb=289ee3d0daa95445ead578f2b674987a4187993d;hp=c638c04d5e060aef26355946d6870a255c03eb6d;hpb=49c98d143c382a1341e1046f5ca00819a25691ba;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index c638c04..0f9bf23 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,
@@ -42,7 +42,10 @@ module TcEnv(
 	topIdLvl, 
 
 	-- New Ids
-	newLocalName, newDFunName, newFamInstTyConName
+	newLocalName, newDFunName, newFamInstTyConName,
+
+        -- Errors
+        famInstNotFound
   ) where
 
 #include "HsVersions.h"
@@ -55,12 +58,12 @@ 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 +160,35 @@ tcLookupLocatedClass = addLocM tcLookupClass
 
 tcLookupLocatedTyCon :: Located Name -> TcM TyCon
 tcLookupLocatedTyCon = addLocM tcLookupTyCon
+
+-- Look up the representation tycon of a family instance.
+--
+-- The match must be unique - ie, match exactly one instance - but the 
+-- type arguments used for matching may be more specific than those of 
+-- the family instance declaration.
+--
+-- Return the instance tycon and its type instance.  For example, if we have
+--
+--  tcLookupFamInst 'T' '[Int]' yields (':R42T', 'Int')
+--
+-- then we have a coercion (ie, type instance of family instance coercion)
+--
+--  :Co:R42T Int :: T [Int] ~ :R42T Int
+--
+-- which implies that :R42T was declared as 'data instance T [a]'.
+--
+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
+	   [(fam_inst, rep_tys)] -> return (famInstTyCon fam_inst, rep_tys)
+	   other                 -> famInstNotFound tycon tys other
+       }
 \end{code}
 
 %************************************************************************
@@ -400,16 +432,21 @@ 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 }
   where
     refine elt@(ATcId { tct_co = Just co, tct_type = ty })
-			  = let (co', ty') = refineType reft ty
-			    in elt { tct_co = Just (co' <.> co), tct_type = ty' }
-    refine (ATyVar tv ty) = ATyVar tv (snd (refineType reft ty))
-				-- Ignore the coercion that refineType returns
-    refine elt		  = elt
+	| Just (co', ty') <- refineType reft ty
+	= elt { tct_co = Just (WpCo co' <.> co), tct_type = ty' }
+    refine (ATyVar tv ty) 
+	| Just (_, ty') <- refineType reft ty
+	= ATyVar tv ty'	-- Ignore the coercion that refineType returns
+
+    refine elt = elt	-- Common case
 \end{code}
 
 %************************************************************************
@@ -603,7 +640,7 @@ 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
@@ -617,12 +654,12 @@ 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
@@ -651,4 +688,11 @@ 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}