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
| 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
; 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;
-- 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.
%*********************************************************
%* *
rnPat :: HsMatchContext Name -- for error messages
-> LPat RdrName
-> (LPat Name -> RnM (a, FreeVars))
- -> RnM (a, FreeVars)
+ -> RnM (a, FreeVars) -- Variables bound by pattern do not
+ -- appear in the result FreeVars
rnPat ctxt pat thing_inside
= rnPats ctxt [pat] (\[pat'] -> thing_inside pat')