<html>
    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - user-defined template operator < not used"
   href="https://bugs.llvm.org/show_bug.cgi?id=48611">48611</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>user-defined template operator < not used
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Windows NT
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>tobias.loew@steag.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Hi,
in the following code the user-defined operator< for enum E1 is used, but the
user-defined template operator< for enum E2 is not used - the built-in
operator< is used instead for E2. Even though the standard states that a user
user-defined relational operator candidate hides the built-in operator during
overload resolution (<a href="https://eel.is/c++draft/over.built#1">https://eel.is/c++draft/over.built#1</a>)

NB: when I change "operator <" to "operator &" (with appropriate return types)
then the user-defined overload is used in both cases.

I searched the standard, if there is a specialization for relational operators
during overload resolution, but I couldn't find one.

Tobias

-----------------------------------------------------------------

#include <iostream>

enum E1 {
    e1_a
};

inline bool operator<(E1, E1) {
    return true;
}

enum E2 {
    e2_a
};

template<class E>
inline bool operator<(E, E) {
    return true;
}


int main()
{
    if (E1::e1_a < E1::e1_a) {
        std::cout << "user-defined operator used for E1\n";
    } else {
        std::cout << "builtin operator used for E1\n";
    }

    if (E2::e2_a < E2::e2_a) {
        std::cout << "user-defined operator used for E2\n";
    } else {
        std::cout << "builtin operator used for E2\n";
    }
}</pre>
        </div>
      </p>


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