REQUIRE does not compile when operator== in different namespace

[darrenjs]

Hi,

I have a simple equality that compiles normally but fails when placed within a REQUIRE. This is a surprise to me, since I was hoping to replace many of my manual tests (which are based on f ( a == b) ) by moving them into a REQUIRE. (Aside, this same conditional compiles when inside the equivalent CppUnit macro).

To reproduce, please compile the file below. I used gcc 7.5.0 on Ubuntu 18, doctest 2.4.1

#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include "doctest.h"

namespace user {

struct label {
  label() : i(0) {}
  int i;
};

}

/* deliberately outside the user:: namespace */
bool operator==(const user::label& lhs, const user::label& rhs) {
  return lhs.i == rhs.i;
}

void foo() {
  user::label a;
  user::label b;

  if (a == b) return; /* this compiles */

  REQUIRE(a == b); /* does not compile */
}

Error:

g++   -Wfatal-errors  -pedantic -Wall --std=c++1z main.cc  
In file included from main.cc:2:0:
doctest.h: In instantiation of ‘doctest::detail::Result doctest::detail::Expression_lhs<L>::operator==(const R&) [with R = user::label; L = const user::label&]’:
main.cc:26:3:   required from here
doctest.h:1149:32: error: no match for ‘operator==’ (operand types are ‘const user::label’ and ‘const user::label’)
 #define DOCTEST_CMP_EQ(l, r) l == r
                                ^
doctest.h:1044:20: note: in expansion of macro ‘DOCTEST_CMP_EQ’
         bool res = op_macro(lhs, rhs);                                                             \
                    ^~~~~~~~
doctest.h:1186:9: note: in expansion of macro ‘DOCTEST_DO_BINARY_EXPRESSION_COMPARISON’
         DOCTEST_DO_BINARY_EXPRESSION_COMPARISON(==, " == ", DOCTEST_CMP_EQ) //!OCLINT bitwise operator in conditional

The declaration of the operator== outside the user namespace is significant; if I move it into user, everything does compiles.

[onqtam]

Well, this isn't good... Catch2 handles this OK as well - only doctest doesn't.

I'm curious what's the use case of having the operator== outside of the namespace?

[darrenjs]

I'm curious what's the use case of having the operator== outside of the namespace?

Am not sure. I came across this code when porting a large project from cppunit to doctest, I don't think it was put in that other namespace deliberately, more likely an accident. But it never caused any problem, well, except as we port to doctest.

Fyi, the reason we prefer doctest over catch, is doctest support for threading, ie, calling REQUIRE from any thread.

[onqtam]

closed thanks to #468 (merged in dev)