[project @ 2001-08-20 08:17:38 by simonpj]

Fix (another) "missing instnace" bug in the renamer.
This one interacted with the interactive loop in ghci.

diff --git a/ghc/compiler/rename/Rename.lhs b/ghc/compiler/rename/Rename.lhs
index 1a75cb3..53ed3a2 100644 (file)
--- a/ghc/compiler/rename/Rename.lhs
+++ b/ghc/compiler/rename/Rename.lhs
@@ -126,7 +126,19 @@ renameStmt dflags hit hst pcs scope_module this_module local_env stmt
         doDump dflags [] stmt [] `thenRn_` returnRn (print_unqual, Nothing)
     else
 
-    slurpImplicitDecls fvs local_env   `thenRn` \ decls ->
+       -- Add implicit free vars, and close decls
+    getImplicitStmtFVs                                 `thenRn` \ implicit_fvs ->
+    slurpImpDecls (fvs `plusFV` implicit_fvs)  `thenRn` \ decls ->
+       -- NB: an earlier version deleted (rdrEnvElts local_env) from
+       --     the fvs.  But (a) that isn't necessary, because previously
+       --     bound things in the local_env will be in the TypeEnv, and 
+       --     the renamer doesn't re-slurp such things, and 
+       -- (b) it's WRONG to delete them. Consider in GHCi:
+       --        Mod> let x = e :: T
+       --        Mod> let y = x + 3
+       --     We need to pass 'x' among the fvs to slurpImpDecls, so that
+       --     the latter can see that T is a gate, and hence import the Num T 
+       --     instance decl.  (See the InTypEnv case in RnIfaces.slurpSourceRefs
 
     doDump dflags binders stmt decls           `thenRn_`
     returnRn (print_unqual, Just (binders, (stmt, decls)))
@@ -171,7 +183,8 @@ renameRdrName dflags hit hst pcs scope_module this_module local_env rdr_names =
                returnRn (print_unqual, Nothing)
        else 
 
-  slurpImplicitDecls (mkNameSet ok_names) local_env `thenRn` \ decls ->
+  slurpImpDecls (mkNameSet ok_names)   `thenRn` \ decls ->
+
   doDump dflags ok_names decls                 `thenRn_`
   returnRn (print_unqual, Just (ok_names, decls))
  where
@@ -197,15 +210,6 @@ loadContextModule scope_module thing_inside
        returnRn (print_unqual, Nothing)
     else
        thing_inside (rdr_env, print_unqual)
-
--- Add implicit free vars, and close decls
-slurpImplicitDecls fvs local_env 
- =  getImplicitStmtFVs                                 `thenRn` \ implicit_fvs ->
-    let
-       filtered_fvs = fvs `delListFromNameSet` rdrEnvElts local_env 
-       source_fvs   = implicit_fvs `plusFV` filtered_fvs
-    in
-    slurpImpDecls source_fvs
 \end{code}
 
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