[LLVMbugs] [Bug 17834] New: "candidate template ignored: invalid explicitly-specified argument for template parameter" involving out-of-range packages int parameters

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17834

            Bug ID: 17834
           Summary: "candidate template ignored: invalid
                    explicitly-specified argument for template parameter"
                    involving out-of-range packages int parameters
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: marc at kdab.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

This is a destilled version of https://codereview.qt-project.org/65868

#include <type_traits>

// Enum                                                                         

enum MouseButton {
  NoButton         = 0x00000000,
  LeftButton       = 0x00000001,
  RightButton      = 0x00000002,
  MidButton        = 0x00000004, // ### Qt 6: remove me                         
  MiddleButton     = MidButton,
  BackButton       = 0x00000008,
  XButton1         = BackButton,
  ExtraButton1     = XButton1,
  ForwardButton    = 0x00000010,
  XButton2         = ForwardButton,
  ExtraButton2     = ForwardButton,
  TaskButton       = 0x00000020,
  ExtraButton3     = TaskButton,
  ExtraButton4     = 0x00000040,
  ExtraButton5     = 0x00000080,
  ExtraButton6     = 0x00000100,
  ExtraButton7     = 0x00000200,
  ExtraButton8     = 0x00000400,
  ExtraButton9     = 0x00000800,
  ExtraButton10    = 0x00001000,
  ExtraButton11    = 0x00002000,
  ExtraButton12    = 0x00004000,
  ExtraButton13    = 0x00008000,
  ExtraButton14    = 0x00010000,
  ExtraButton15    = 0x00020000,
  ExtraButton16    = 0x00040000,
  ExtraButton17    = 0x00080000,
  ExtraButton18    = 0x00100000,
  ExtraButton19    = 0x00200000,
  ExtraButton20    = 0x00400000,
  ExtraButton21    = 0x00800000,
  ExtraButton22    = 0x01000000,
  ExtraButton23    = 0x02000000,
  ExtraButton24    = 0x04000000,
  AllButtons       = 0x07ffffff,
  MaxMouseButton   = ExtraButton24,
  MouseButtonMask  = 0xffffffff
};


static_assert(!std::is_signed<MouseButton>::value, "Enum should be unsigned");

// MouseButtons code                                                            

struct Int {
  int i;
  constexpr Int(int i) : i(i) {}
  constexpr operator int() const { return i; }
};

struct MouseButtons {
  unsigned int i;

  constexpr MouseButtons(MouseButton e) : i(e) {}
  constexpr MouseButtons(Int i) : i(i) {}
  constexpr operator unsigned int() const { return i; }
};

constexpr MouseButtons operator~(MouseButtons i) { return Int(~i.i); }

// test code                                                                    

template <unsigned int N, typename T> bool f(T n) { return n == N; }

int main() {
  f< MouseButtons(LeftButton)>( LeftButton); // OK                              
  f<~MouseButtons(LeftButton)>(~LeftButton); // ERROR: invalid
explicitly-specified argument for template parameter 'T'                        
}

Expected error: "candidate template ignored: narrowing conversion from X to Y
for template argument 'N'.
Note in particular how the current message picks the _wrong template argument_
to complain about.

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