[project @ 2003-01-09 15:35:31 by simonpj]

Catch a staging error that slipped through before

diff --git a/ghc/compiler/typecheck/TcEnv.lhs b/ghc/compiler/typecheck/TcEnv.lhs
index ec765dc..23eba50 100644 (file)
--- a/ghc/compiler/typecheck/TcEnv.lhs
+++ b/ghc/compiler/typecheck/TcEnv.lhs
@@ -59,7 +59,7 @@ import TcType         ( Type, ThetaType, TcKind, TcTyVar, TcTyVarSet,
                        )
 import qualified Type  ( getTyVar_maybe )
 import Rules           ( extendRuleBase )
-import Id              ( idName, isDataConWrapId_maybe )
+import Id              ( idName, isLocalId, isDataConWrapId_maybe )
 import Var             ( TyVar, Id, idType )
 import VarSet
 import VarEnv
@@ -339,9 +339,22 @@ tcLookupIdLvl name
   = tcLookup name      `thenM` \ thing -> 
     case thing of
        ATcId tc_id lvl   -> returnM (tc_id, lvl)
-       AGlobal (AnId id) -> returnM (id, impLevel)
+       AGlobal (AnId id)       -- See [Note: Levels]
+         | isLocalId id  -> returnM (id, topLevel)
+         | otherwise     -> returnM (id, impLevel)
        other             -> pprPanic "tcLookupIdLvl" (ppr name)
 
+--             [Note: Levels]
+-- Globals may either be imported, or may be from an earlier "chunk" 
+-- (separated by declaration splices) of this module.  The former
+-- *can* be used inside a top-level splice, but the latter cannot.
+-- Hence we give the former impLevel, but the latter topLevel
+-- E.g. this is bad:
+--     x = [| foo |]
+--     $( f x )
+-- By the time we are prcessing the $(f x), the binding for "x" 
+-- will be in the global env, not the local one.
+
 tcLookupLocalIds :: [Name] -> TcM [TcId]
 -- We expect the variables to all be bound, and all at
 -- the same level as the lookup.  Only used in one place...