CWG Issue 2789 (original) (raw)

This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 118f. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-11-07

2789. Overload resolution with implicit and explicit object member functions

Section: 12.2.4.1 [over.match.best.general]Status: CD7Submitter: Corentin JabotDate: 2023-08-08

[Accepted as a DR at the November, 2023 meeting.]

Consider:

template struct S { constexpr void f(); // #1 constexpr void f(this S&) requires true; // #2 };

void test() { S<> s; s.f(); // #3 }

With the current rules, the call at #3 is ambiguous, even though #2 is more constrainted.

Proposed resolution (approved by CWG 2023-11-07):

Change in 12.2.4.1 [over.match.best.general] bullet 2.6 as follows:

• ...
• F1 and F2 are non-template functions with and
  • they have the sameparameter-type-lists non-object-parameter-type-lists (9.3.4.6 [dcl.fct]), and
  • if they are member functions, both are direct members of the same class, and
  • if both are non-static member functions, they have the same types for their object parameters, and
  • F1 is more constrained than F2 according to the partial ordering of constraints described in 13.5.5 [temp.constr.order],
    or if not that,
    [ Example:
    template
    struct S {
    constexpr void f(); // #1
    constexpr void f(this S&) requires true; // #2
    };
    void test() {
    S<> s;
    s.f(); // calls #2
    }
    -- end example ]
• ...