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

[ghc-hetmet.git] / ghc / compiler / coreSyn / CoreTidy.lhs

diff --git a/ghc/compiler/coreSyn/CoreTidy.lhs b/ghc/compiler/coreSyn/CoreTidy.lhs
index 64d7c73..dc2c600 100644 (file)
--- 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