Separate the language flags from the other DynFlag's

[ghc-hetmet.git] / compiler / rename / RnPat.lhs

diff --git a/compiler/rename/RnPat.lhs b/compiler/rename/RnPat.lhs
index 813f39b..01f621b 100644 (file)
--- a/compiler/rename/RnPat.lhs
+++ b/compiler/rename/RnPat.lhs
@@ -40,13 +40,13 @@ import TcRnMonad
 import TcHsSyn         ( hsOverLitName )
 import RnEnv
 import RnTypes
-import DynFlags                ( DynFlag(..) )
+import DynFlags
 import PrelNames
 import Constants       ( mAX_TUPLE_SIZE )
 import Name
 import NameSet
-import Module
 import RdrName
+import BasicTypes
 import ListSetOps      ( removeDups, minusList )
 import Outputable
 import SrcLoc
@@ -135,15 +135,14 @@ data NameMaker
 
   | LetMk       -- Let bindings, incl top level
                -- Do *not* check for unused bindings
-      (Maybe Module)   -- Just m  => top level of module m
-                       -- Nothing => not top level
+      TopLevelFlag
       MiniFixityEnv
 
-topRecNameMaker :: Module -> MiniFixityEnv -> NameMaker
-topRecNameMaker mod fix_env = LetMk (Just mod) fix_env
+topRecNameMaker :: MiniFixityEnv -> NameMaker
+topRecNameMaker fix_env = LetMk TopLevel fix_env
 
 localRecNameMaker :: MiniFixityEnv -> NameMaker
-localRecNameMaker fix_env = LetMk Nothing fix_env 
+localRecNameMaker fix_env = LetMk NotTopLevel fix_env 
 
 matchNameMaker :: HsMatchContext a -> NameMaker
 matchNameMaker ctxt = LamMk report_unused
@@ -162,15 +161,17 @@ newName (LamMk report_unused) rdr_name
           ; when report_unused $ warnUnusedMatches [name] fvs
           ; return (res, name `delFV` fvs) })
 
-newName (LetMk mb_top fix_env) rdr_name
+newName (LetMk is_top fix_env) rdr_name
   = CpsRn (\ thing_inside -> 
-        do { name <- case mb_top of
-                       Nothing  -> newLocalBndrRn rdr_name
-                       Just mod -> newTopSrcBinder mod rdr_name
-          ; bindLocalNamesFV_WithFixities [name] fix_env $
+        do { name <- case is_top of
+                       NotTopLevel -> newLocalBndrRn rdr_name
+                       TopLevel    -> newTopSrcBinder rdr_name
+          ; bindLocalName name $       -- Do *not* use bindLocalNameFV here
+                                       -- See Note [View pattern usage]
+             addLocalFixities fix_env [name] $
             thing_inside name })
                          
-    -- Note: the bindLocalNamesFV_WithFixities is somewhat suspicious 
+    -- Note: the bindLocalName is somewhat suspicious
     --       because it binds a top-level name as a local name.
     --       however, this binding seems to work, and it only exists for
     --       the duration of the patterns and the continuation;
@@ -178,6 +179,14 @@ newName (LetMk mb_top fix_env) rdr_name
     --       before going on to the RHSes (see RnSource.lhs).
 \end{code}
 
+Note [View pattern usage]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+  let (r, (r -> x)) = x in ...
+Here the pattern binds 'r', and then uses it *only* in the view pattern.
+We want to "see" this use, and in let-bindings we collect all uses and
+report unused variables at the binding level. So we must use bindLocalName
+here, *not* bindLocalNameFV.  Trac #3943.
 
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