Bugfix: code generation bug that affected dialogs.nim

lib/wrappers/gtk/gtk2.nim

@@ -5373,7 +5373,7 @@ const
   RESPONSE_ACCEPT* = - cint(3)
   RESPONSE_DELETE_EVENT* = - cint(4)
   RESPONSE_OK* = - cint(5)
-  RESPONSE_CANCEL* = - cint(6)
+  RESPONSE_CANCEL* = cint(-6)
   RESPONSE_CLOSE* = - cint(7)
   RESPONSE_YES* = - cint(8)
   RESPONSE_NO* = - cint(9)
@@ -16652,6 +16652,7 @@ proc file_chooser_dialog_new*(title: cstring, parent: PWindow,
                               action: TFileChooserAction, 
                               first_button_text: cstring): PFileChooser{.cdecl, 
     varargs, dynlib: lib, importc: "gtk_file_chooser_dialog_new".}
+        
 proc file_chooser_dialog_new_with_backend*(title: cstring, parent: PWindow, 
     action: TFileChooserAction, backend: cstring, first_button_text: cstring): PFileChooser{.
     varargs, cdecl, dynlib: lib, 

rod/ccgexprs.nim

@@ -63,7 +63,7 @@ proc genLiteral(p: BProc, v: PNode, ty: PType): PRope =
       result = ropef("(($1) $2)", [getTypeDesc(p.module, 
           skipTypes(ty, abstractVarRange)), intLiteral(v.intVal)])
   of nkNilLit: 
-    result = toRope("0")
+    result = toRope("NIM_NIL")
   of nkStrLit..nkTripleStrLit: 
     if skipTypes(ty, abstractVarRange).kind == tyString: 
       var id = NodeTableTestOrSet(p.module.dataCache, v, gid)

tests/accept/compile/tbug538751.nim

@@ -0,0 +1,8 @@
+type
+    PNode = ref TNode
+    TNode = tuple[self: PNode]
+
+var node: PNode
+new(node)
+node.self = node
+

tests/accept/compile/temptyecho.nim

@@ -0,0 +1,2 @@
+echo()
+