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From: "fchelnokov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/113529] New: Incorrect result of requires-expression in case of function call ambiguity
Date: Sun, 21 Jan 2024 08:51:31 +0000	[thread overview]
Message-ID: <bug-113529-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113529

            Bug ID: 113529
           Summary: Incorrect result of requires-expression in case of
                    function call ambiguity
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

In this program


#include <compare>

struct A { 
    auto operator <=>(const A&) const = default;
    bool operator <(const A&) const = default;
};
struct B { 
    auto operator <=>(const B&) const = default; 
};
struct C : A, B {};

template<typename T>
concept Cmp = requires(T u, T v) { u < v; };

//auto cmp = C{} < C{}; //this correctly fails due to ambiguity
static_assert( !Cmp<C> ); //but this evaluates wrongly in GCC


C{} < C{} is correctly rejected as ambiguous, but for some reason `requires` in
GCC returns that the objects can be compared. This program is accepted by Clang
truck (to be v18). Online demo: https://godbolt.org/z/76zoYMd6h

Explanation of ambiguity: https://stackoverflow.com/a/69245639/7325599

             reply	other threads:[~2024-01-21  8:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-21  8:51 fchelnokov at gmail dot com [this message]
2024-01-21  9:03 ` [Bug c++/113529] Incorrect result of requires-expression in case of function call ambiguity and `operator<=>` pinskia at gcc dot gnu.org
2024-01-22 18:15 ` ppalka at gcc dot gnu.org
2024-01-24 22:11 ` cvs-commit at gcc dot gnu.org
2024-01-26 14:42 ` cvs-commit at gcc dot gnu.org
2024-01-26 14:43 ` ppalka at gcc dot gnu.org

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