// N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf 
#define msg "p320.cpp(152) 13.3.1.2 Operators in expressions [over.match.oper]"
// Edited by Dr. Ogawa Kiyoshi. Compile procedure and results record.

#include <iostream>

struct String {
String (const String&);
String (const char*);
operator const char* ();
};
String operator + (const String&, const String&);

void f() {
const char* p= "one" + "two"; // ill-formed because neither
// operand has class or enumeration type
int I = 1 + 1; // Always evaluates to 2 even if
// class or enumeration types exist that
// would perform the operation.
}


struct A {
operator int();
};
A operator+(const A&, const A&);
void m() {
A a, b;
a + b; // operator+(a,b) chosen over int(a) + int(b)
}

struct X {
operator double();
};
struct Y {
operator int*();
};
int *a = Y() + 100.0; // error: pointer arithmetic requires integral operand
int *b = Y() + X(); // error: pointer arithmetic requires integral operand

struct A { };
void operator + (A, A);
struct B {
void operator + (B);
void f ();
};
A a;
void B::f() {
operator+ (a,a); // error: global operator hidden by member
a + a; // OK: calls global operator+
}
int main(){
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppgl17.sh p320
$ clang++ p320.cpp
p320.cpp:16:22: error: invalid operands to binary expression ('const char *' and 'const char *')
const char* p= "one" + "two"; // ill-formed because neither
               ~~~~~ ^ ~~~~~
p320.cpp:50:15: error: too many arguments to function call, expected 1, have 2
operator+ (a2,a2); // error: global operator hidden by member
~~~~~~~~~     ^~
p320.cpp:45:1: note: 'operator+' declared here
void operator + (B);
^
2 errors generated.

$ g++-7 p320.cpp
p320.cpp: In function 'void f()':
p320.cpp:16:22: error: invalid operands of types 'const char [4]' and 'const char [4]' to binary 'operator+'
 const char* p= "one" + "two"; // ill-formed because neither
                ~~~~~~^~~~~~~
p320.cpp: At global scope:
p320.cpp:39:14: error: no match for 'operator+' (operand types are 'Y' and 'double')
 int *a = Y() + 100.0; // error: pointer arithmetic requires integral operand
          ~~~~^~~~~~~
p320.cpp:13:8: note: candidate: String operator+(const String&, const String&)
 String operator + (const String&, const String&);
        ^~~~~~~~
p320.cpp:13:8: note:   no known conversion for argument 1 from 'Y' to 'const String&'
p320.cpp:27:3: note: candidate: A operator+(const A&, const A&)
 A operator+(const A&, const A&);
   ^~~~~~~~
p320.cpp:27:3: note:   no known conversion for argument 1 from 'Y' to 'const A&'
p320.cpp:40:14: error: no match for 'operator+' (operand types are 'Y' and 'X')
 int *b = Y() + X(); // error: pointer arithmetic requires integral operand
          ~~~~^~~~~
p320.cpp:13:8: note: candidate: String operator+(const String&, const String&)
 String operator + (const String&, const String&);
        ^~~~~~~~
p320.cpp:13:8: note:   no known conversion for argument 1 from 'Y' to 'const String&'
p320.cpp:27:3: note: candidate: A operator+(const A&, const A&)
 A operator+(const A&, const A&);
   ^~~~~~~~
p320.cpp:27:3: note:   no known conversion for argument 1 from 'Y' to 'const A&'
p320.cpp: In member function 'void B::f()':
p320.cpp:50:17: error: no matching function for call to 'B::operator+(A2&, A2&)'
 operator+ (a2,a2); // error: global operator hidden by member
                 ^
p320.cpp:45:6: note: candidate: void B::operator+(B)
 void operator + (B);
      ^~~~~~~~
p320.cpp:45:6: note:   candidate expects 1 argument, 2 provided