X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcEnv.lhs;h=a23795cf6d3975b0546b4df357df73ec3959a8a4;hp=dfdf58e04a16062b8665eb504114ff1c62cd3ba3;hb=3f1b316d7035c55cd712cd39a9981339bcef2e8c;hpb=17b297d97d327620ed6bfab942f8992b2446f1bf

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index dfdf58e..a23795c 100644
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -3,11 +3,11 @@
 %
 
 \begin{code}
-{-# OPTIONS_GHC -w #-}
+{-# 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/WorkingConventions#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module TcEnv(
@@ -47,7 +47,7 @@ module TcEnv(
 
 	-- Template Haskell stuff
 	checkWellStaged, spliceOK, bracketOK, tcMetaTy, thLevel, 
-	topIdLvl, 
+	topIdLvl, thTopLevelId,
 
 	-- New Ids
 	newLocalName, newDFunName, newFamInstTyConName,
@@ -110,7 +110,7 @@ tcLookupGlobal name
   = do	{ env <- getGblEnv
 	
 		-- Try local envt
-	; case lookupNameEnv (tcg_type_env env) name of {
+	; case lookupNameEnv (tcg_type_env env) name of { 
 		Just thing -> return thing ;
 		Nothing	   -> do 
 	 
@@ -123,12 +123,12 @@ tcLookupGlobal name
 
 		-- Should it have been in the local envt?
 	{ case nameModule_maybe name of
-		Nothing -> notFound name	-- Internal names can happen in GHCi
+		Nothing -> notFound name env -- Internal names can happen in GHCi
 
 		Just mod | mod == tcg_mod env 	-- Names from this module 
-			 -> notFound name	-- should be in tcg_type_env
+			 -> notFound name env -- should be in tcg_type_env
 			 | mod == thFAKE	-- Names bound in TH declaration brackets
-			 -> notFound name	-- should be in tcg_env
+			 -> notFound name env -- should be in tcg_env
 			 | otherwise
 		         -> tcImportDecl name	-- Go find it in an interface
 	}}}}}
@@ -553,12 +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 $ 
@@ -566,7 +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]
@@ -604,6 +604,10 @@ tcMetaTy :: Name -> TcM Type
 tcMetaTy tc_name
   = tcLookupTyCon tc_name	`thenM` \ t ->
     returnM (mkTyConApp t [])
+
+thTopLevelId :: Id -> Bool
+-- See Note [What is a top-level Id?] in TcSplice
+thTopLevelId id = isGlobalId id || isExternalName (idName id)
 \end{code}
 
 
@@ -635,30 +639,20 @@ 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
@@ -718,9 +712,11 @@ pprBinders :: [Name] -> SDoc
 pprBinders [bndr] = quotes (ppr bndr)
 pprBinders bndrs  = pprWithCommas ppr bndrs
 
-notFound name 
-  = failWithTc (ptext SLIT("GHC internal error:") <+> quotes (ppr name) <+> 
-		ptext SLIT("is not in scope"))
+notFound name env
+  = failWithTc (vcat[ptext SLIT("GHC internal error:") <+> quotes (ppr name) <+> 
+                     ptext SLIT("is not in scope during type checking, but it passed the renamer"),
+                     ptext SLIT("tcg_type_env of environment:") <+> ppr (tcg_type_env env)]
+                    )
 
 wrongThingErr expected thing name
   = failWithTc (pprTcTyThingCategory thing <+> quotes (ppr name) <+>