X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcEnv.lhs;h=58bda528cfedf6f6f65da9f0f84594b365a11db3;hb=2eeaaa6f9eb206ad3473c151556629a2e2624f78;hp=4f48f7fde58d3294ed032fb4a655f0371daf1bdc;hpb=5822cb8d13aa3c05d2b46b4510c13d94b902eb21;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index 4f48f7f..58bda52 100644
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -3,6 +3,13 @@
 %
 
 \begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
 module TcEnv(
 	TyThing(..), TcTyThing(..), TcId,
 
@@ -546,12 +553,12 @@ thLevel (Brack l _ _) = l
 
 
 checkWellStaged :: SDoc		-- What the stage check is for
-		-> ThLevel 	-- Binding level
+		-> ThLevel 	-- Binding level (increases inside brackets)
 	        -> ThStage	-- Use stage
 		-> TcM ()	-- Fail if badly staged, adding an error
 checkWellStaged pp_thing bind_lvl use_stage
-  | bind_lvl <= use_lvl 	-- OK!
-  = returnM ()	
+  | use_lvl >= bind_lvl 	-- OK! Used later than bound
+  = returnM ()			-- E.g.  \x -> [| $(f x) |]
 
   | bind_lvl == topLevel	-- GHC restriction on top level splices
   = failWithTc $ 
@@ -559,7 +566,7 @@ checkWellStaged pp_thing bind_lvl use_stage
 	 nest 2 (ptext SLIT("is used in a top-level splice, and must be imported, not defined locally"))]
 
   | otherwise			-- Badly staged
-  = failWithTc $ 
+  = failWithTc $ 		-- E.g.  \x -> $(f x)
     ptext SLIT("Stage error:") <+> pp_thing <+> 
 	hsep   [ptext SLIT("is bound at stage") <+> ppr bind_lvl,
 		ptext SLIT("but used at stage") <+> ppr use_lvl]
@@ -628,30 +635,20 @@ iDFunId info = instanceDFunId (iSpec info)
 
 data InstBindings
   = VanillaInst 		-- The normal case
-	(LHsBinds Name)		-- Bindings
+	(LHsBinds Name)		-- Bindings for the instance methods
 	[LSig Name]		-- User pragmas recorded for generating 
 				-- specialised instances
 
   | NewTypeDerived              -- Used for deriving instances of newtypes, where the
 				-- witness dictionary is identical to the argument 
 				-- dictionary.  Hence no bindings, no pragmas.
-	(Maybe [PredType])
-		-- Nothing      => The newtype-derived instance involves type variables,
-		--	           and the dfun has a type like df :: forall a. Eq a => Eq (T a)
-		-- Just (r:scs) => The newtype-defined instance has no type variables
-		--		   so the dfun is just a constant, df :: Eq T
-		-- 		   In this case we need to know waht the rep dict, r, and the 
-		--		   superclasses, scs, are.  (In the Nothing case these are in the
-		--		   dict fun's type.)
-		--		   Invariant: these PredTypes have no free variables
-		-- NB: In both cases, the representation dict is the *first* dict.
 
 pprInstInfo info = vcat [ptext SLIT("InstInfo:") <+> ppr (idType (iDFunId info))]
 
 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 -> (Class, Type)
 simpleInstInfoClsTy info = case instanceHead (iSpec info) of