Add unless-disposed combinator to clean up some repetition, and fix bogus error reported from timer thread if an I/O operation with a set timeout fails on Windows

basis/io/backend/unix/unix.factor

@@ -25,25 +25,25 @@ TUPLE: fd < disposable fd ;
     fd new-disposable swap >>fd ;
 
 M: fd dispose
-    dup disposed>> [ drop ] [
+    [
         {
             [ cancel-operation ]
             [ t >>disposed drop ]
             [ unregister-disposable ]
             [ fd>> close-file ]
         } cleave
-    ] if ;
+    ] unless-disposed ;
 
 M: fd handle-fd dup check-disposed fd>> ;
 
 M: fd cancel-operation ( fd -- )
-    dup disposed>> [ drop ] [
+    [
         fd>>
         mx get-global
         [ remove-input-callbacks [ t swap resume-with ] each ]
         [ remove-output-callbacks [ t swap resume-with ] each ]
         2bi
-    ] if ;
+    ] unless-disposed ;
 
 M: unix tell-handle ( handle -- n )
     fd>> 0 SEEK_CUR [ lseek ] unix-system-call [ io-error ] [ ] bi ;

basis/io/backend/windows/nt/nt.factor

@@ -71,7 +71,7 @@ M: winnt add-completion ( win32-handle -- )
     ] [ resume-callback t ] if ;
 
 M: win32-handle cancel-operation
-    [ check-disposed ] [ handle>> CancelIo drop ] bi ;
+    [ handle>> CancelIo win32-error=0/f ] unless-disposed ;
 
 M: winnt io-multiplex ( nanos -- )
     handle-overlapped [ 0 io-multiplex ] when ;

basis/io/backend/windows/windows.factor

@@ -30,9 +30,7 @@ TUPLE: win32-file < win32-handle ptr ;
     win32-file new-win32-handle ;
 
 M: win32-file dispose
-    [ dup disposed>> [ drop ] [ cancel-operation ] if ]
-    [ call-next-method ]
-    bi ;
+    [ cancel-operation ] [ call-next-method ] bi ;
 
 HOOK: CreateFile-flags io-backend ( DWORD -- DWORD )
 HOOK: FileArgs-overlapped io-backend ( port -- overlapped/f )

basis/io/monitors/linux/linux.factor

@@ -56,10 +56,10 @@ M: linux (monitor) ( path recursive? mailbox -- monitor )
 M: linux-monitor dispose* ( monitor -- )
     [ [ wd>> ] [ watches>> ] bi delete-at ]
     [
-        dup inotify>> disposed>> [ drop ] [
+        dup inotify>> [
             [ inotify>> handle>> handle-fd ] [ wd>> ] bi
             inotify_rm_watch io-error
-        ] if
+        ] unless-disposed
     ]
     [ call-next-method ]
     tri ;

basis/io/monitors/recursive/recursive.factor

@@ -49,10 +49,10 @@ M: recursive-monitor dispose*
     monitor tget children>> values dispose-each ;
 
 : pump-step ( msg -- )
-    monitor tget disposed>> [ drop ] [
+    monitor tget [
         [ [ monitor>> path>> ] [ path>> ] bi append-path ] [ changed>> ] bi
         monitor tget queue-change
-    ] if ;
+    ] unless-disposed ;
 
 : child-added ( path monitor -- )
     path>> prepend-path add-child-monitor ;

core/destructors/destructors.factor

@@ -1,4 +1,4 @@
-! Copyright (C) 2007, 2009 Doug Coleman, Slava Pestov.
+! Copyright (C) 2007, 2010 Doug Coleman, Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors continuations kernel namespaces make
 sequences vectors sets assocs init math ;
@@ -40,15 +40,17 @@ ERROR: already-disposed disposable ;
 
 GENERIC: dispose ( disposable -- )
 
-M: object dispose
-    dup disposed>> [ drop ] [ t >>disposed dispose* ] if ;
+: unless-disposed ( disposable quot -- )
+    [ dup disposed>> [ drop ] ] dip if ; inline
+
+M: object dispose [ t >>disposed dispose* ] unless-disposed ;
 
 M: disposable dispose
-    dup disposed>> [ drop ] [
+    [
         [ unregister-disposable ]
         [ call-next-method ]
         bi
-    ] if ;
+    ] unless-disposed ;
 
 : dispose-each ( seq -- )
     [