[llvm-bugs] [Bug 48611] New: user-defined template operator < not used

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48611

            Bug ID: 48611
           Summary: user-defined template operator < not used
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: tobias.loew at steag.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

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 (https://eel.is/c++draft/over.built#1)

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";
    }
}

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20201228/7561d1c3/attachment.html>