Standard Conversion Sequences

The following standard conversion sequences are unsupported:

• A standard conversion sequence that includes a conversion having a conversion rank. Example:

  int f0(long double) { return 0; }
  
  int f0(double) { return 1; }
  
  float f = 2.3f; 
  
  value = f0(f); //should be 1 
  
  -----------^------------- ERROR ambiguous
  

• A standard conversion sequence that includes a promotion, but no conversion, having a conversion rank. Example:

  int f0(char) { return 0; }
  
  int f0(int) { return 1; }
  
   short s = 5;
  
  value = f0(s);
  
  -----------------^------------- ERROR ambiguous
  

• A pointer conversion with a Conversion rank. Example:

  int f0(void *) { return 0; }
  
  int f0(int) { return 1; }
  
  value = f0((short) 0);
  
  ----------------^------------- ERROR ambiguous
  

• User-Defined Conversion Sequences

  A conversion sequence that consists of a standard conversion sequence, followed by a conversion constructor and a standard conversion sequence, is considered a user-defined conversion sequence by overload resolution and is unsupported. Example:

  char k = 'a';
  
  char * kp = &k;
  
  struct S0 {
  
        S0(...) { flag = 0; }
  
        S0(void *) { flag = 1; }
  
  };
  
  const S0& s0r = kp; 
  
  -----------------^-----ERROR: Illegal cast-operation