[project @ 2001-05-14 12:03:41 by simonpj]

****	MERGE WITH 5.00 BRANCH     ********

	-----------------------------------------------
	Expose record selectors with correct unfoldings
	-----------------------------------------------

The problem was that there was that with "ghc --make" we were
passing on record selectors to importing modules in their un-tidied
form.  The idea was that they have very stylised bindings so they
don't need tidying.  But they do, because they may mention error
messages that get floated out.

Here's the comment from CoreTidy.lhs

-- MINOR-HACK ALERT: we *do* tidy record selectors.  Reason: they mention error
-- messages, which may be floated out:
--	x_field pt = case pt of
--			Rect x y -> y
--			Pol _ _  -> error "buggle wuggle"
-- The error message will be floated out so we'll get
--	lvl5 = error "buggle wuggle"
--	x_field pt = case pt of
--			Rect x y -> y
--			Pol _ _  -> lvl5
--
-- When this happens, it's vital that the Id exposed to importing modules
-- (by ghci) mentions lvl5 in its unfolding, not the un-tidied version.
--
-- What about the Id in the TyCon?  It probably shouldn't be in the TyCon at
-- all, but in any case it will have the error message inline so it won't matter.

1 files changed, 24 insertions, 6 deletions

diff --git a/ghc/compiler/coreSyn/CoreTidy.lhs b/ghc/compiler/coreSyn/CoreTidy.lhs
index 64d7c738d6..dc2c600fbc 100644
--- a/ghc/compiler/coreSyn/CoreTidy.lhs
+++ b/ghc/compiler/coreSyn/CoreTidy.lhs
@@ -20,8 +20,8 @@ import VarEnv
 import VarSet
 import Var		( Id, Var )
 import Id		( idType, idInfo, idName, isExportedId, 
-			  idSpecialisation, idUnique, 
-			  mkVanillaGlobal, isLocalId, isImplicitId,
+			  idSpecialisation, idUnique, isDataConWrapId,
+			  mkVanillaGlobal, isLocalId, 
 			  hasNoBinding, mkUserLocal
 			) 
 import IdInfo		{- loads of stuff -}
@@ -204,8 +204,8 @@ mkFinalTypeEnv type_env final_ids
 	-- in interface files, because they are needed by importing modules when
 	-- using the compilation manager
 
-	-- We keep constructor workers, because they won't appear
-	-- in the bindings from which final_ids are derived!
+	-- We keep "hasNoBinding" Ids, notably constructor workers, 
+	-- because they won't appear in the bindings from which final_ids are derived!
     keep_it (AnId id) = hasNoBinding id	-- Remove all Ids except constructor workers
     keep_it other     = True		-- Keep all TyCons and Classes
 \end{code}
@@ -393,8 +393,26 @@ tidyTopBinder :: Module -> IdEnv Bool
 tidyTopBinder mod ext_ids cg_info_env tidy_env rhs
 	      env@(orig_env2, occ_env2, subst_env2) id
 
-  | isImplicitId id	-- Don't mess with constructors, 
-  = (env, id)		-- record selectors, and the like
+  | isDataConWrapId id	-- Don't tidy constructor wrappers
+  = (env, id)		-- The Id is stored in the TyCon, so it would be bad
+			-- if anything changed
+
+-- HACK ALERT: we *do* tidy record selectors.  Reason: they mention error
+-- messages, which may be floated out:
+--	x_field pt = case pt of
+--			Rect x y -> y
+--			Pol _ _  -> error "buggle wuggle"
+-- The error message will be floated out so we'll get
+--	lvl5 = error "buggle wuggle"
+--	x_field pt = case pt of
+--			Rect x y -> y
+--			Pol _ _  -> lvl5
+--
+-- When this happens, it's vital that the Id exposed to importing modules
+-- (by ghci) mentions lvl5 in its unfolding, not the un-tidied version.
+-- 
+-- What about the Id in the TyCon?  It probably shouldn't be in the TyCon at
+-- all, but in any case it will have the error message inline so it won't matter.
 
   | otherwise
 	-- This function is the heart of Step 2