X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcEnv.lhs;h=14f9541f2950f4d0029bcd408b46ed97f8b76452;hp=9afe28fdba1ee69ab34121a1a928c17778d524c2;hb=9ffadf219cbc4f8ec57264786df936a3cee88aec;hpb=9bcd95bad83ee937c178970e8b729732e680fe1e

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index 9afe28f..14f9541 100644
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -57,6 +57,7 @@ import TcType
 -- import TcSuspension
 import qualified Type
 import Id
+import Coercion
 import Var
 import VarSet
 import VarEnv
@@ -125,11 +126,8 @@ tcLookupGlobal name
 	}}}}}
 
 tcLookupField :: Name -> TcM Id		-- Returns the selector Id
-tcLookupField name = do
-    thing <- tcLookup name	-- Note [Record field lookup]
-    case thing of
-	AGlobal (AnId id) -> return id
-	thing -> wrongThingErr "field name" thing name
+tcLookupField name 
+  = tcLookupId name	-- Note [Record field lookup]
 
 {- Note [Record field lookup]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -642,8 +640,12 @@ data InstBindings a
 				-- specialised instances
 
   | NewTypeDerived              -- Used for deriving instances of newtypes, where the
-				-- witness dictionary is identical to the argument 
+	CoercionI		-- witness dictionary is identical to the argument 
 				-- dictionary.  Hence no bindings, no pragmas.
+		-- The coercion maps from newtype to the representation type
+		-- (mentioning type variables bound by the forall'd iSpec variables)
+		-- E.g.   newtype instance N [a] = N1 (Tree a)
+		-- 	  co : N [a] ~ Tree a
 
 pprInstInfo :: InstInfo a -> SDoc
 pprInstInfo info = vcat [ptext (sLit "InstInfo:") <+> ppr (idType (iDFunId info))]
@@ -651,8 +653,8 @@ pprInstInfo info = vcat [ptext (sLit "InstInfo:") <+> ppr (idType (iDFunId info)
 pprInstInfoDetails :: OutputableBndr a => InstInfo a -> SDoc
 pprInstInfoDetails info = pprInstInfo info $$ nest 2 (details (iBinds info))
   where
-    details (VanillaInst b _) = pprLHsBinds b
-    details NewTypeDerived    = text "Derived from the representation type"
+    details (VanillaInst b _)  = pprLHsBinds b
+    details (NewTypeDerived _) = text "Derived from the representation type"
 
 simpleInstInfoClsTy :: InstInfo a -> (Class, Type)
 simpleInstInfoClsTy info = case instanceHead (iSpec info) of