When I declare operators for some of my custom flags, it causes some of the default flags to lose their operators. Below is an example that reproduces the issue (Qt 4.6/4.7).

Not sure if I've simply missed some caveat and, of course, in my actual app the MainWindow and Foo classes are in separate files as is the main().

Qt Code: 
  1. #include <QList>
  2. #include <QSet>
  3. #include <iostream>
  4. #include <cstdlib>
  5. #include <ctime>
  6. #include <QObject>
  7. #include <QDockWidget>
  8. #include <QMainWindow>
  9.  
  10. using namespace std;
  11.  
  12. namespace kex
  13. {
  14.   class Foo
  15.   {
  16.     Q_FLAGS(NType NTypes)
  17.  
  18.   public:
  19.     enum NType {
  20.       TypeOne = 0x1,
  21.       TypeTwo = 0x2,
  22.     };
  23.     Q_DECLARE_FLAGS(NTypes, NType)
  24.  
  25.     void flagsFunc(NTypes nt)
  26.     {
  27.  
  28.     }
  29.   };
  30.  
  31.   Q_DECLARE_OPERATORS_FOR_FLAGS(Foo::NTypes)
  32.  
  33.     class MyMainWindow : public QMainWindow
  34.     {
  35.     public:
  36.       MyMainWindow(QWidget *parent = 0) : QMainWindow(parent) {
  37.         /*
  38. temp.cpp: In constructor 'kex::MyMainWindow::MyMainWindow(QWidget*)':
  39. temp.cpp:38: error: conversion from 'int' to 'Qt::DockWidgetAreas' is ambiguous
  40. /Library/Frameworks/QtCore.framework/Headers/qglobal.h:2169: note: candidates are: QFlags<Enum>::QFlags(void**) [with Enum = Qt::DockWidgetArea] <near match>
  41. /Library/Frameworks/QtCore.framework/Headers/qglobal.h:2168: note:                 QFlags<Enum>::QFlags(Enum) [with Enum = Qt::DockWidgetArea] <near match>
  42.         */
  43.         _dock.setAllowedAreas(Qt::LeftDockWidgetArea | 
  44.           Qt::RightDockWidgetArea);
  45.       }
  46.  
  47.     private:
  48.       QDockWidget _dock;
  49.     };
  50.  
  51. };
  52.  
  53. int main ()
  54. {
  55.   kex::Foo foo;
  56.   foo.flagsFunc(kex::Foo::TypeOne | kex::Foo::TypeTwo);
  57.   return 0
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