https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101698
Bug ID: 101698
Summary: Template type conversion operator from base class
preferred over matching overload
Product: gcc
Version: 11.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ammiera at hotmail dot com
Target Milestone: ---
There are two conversion operators, template and non-templated.
Their return type might match:
virtual operator const std::string&() const;
template <class T> operator const T&() const;
If so, when trying to call it, the template is always preferred over
non-template and there's no way to SFINAE out of it:
#include <iostream>
#include <string>
#include <type_traits>
class Base {
public:
template <class T>
operator const T&() const {
std::cout << "use template method" << std::endl;
static T tmp{};
return tmp;
}
virtual operator const std::string&() const {
std::cout << "use overload method" << std::endl;
const static std::string tmp;
return tmp;
}
};
template <class T>
class Derive : public Base {
public:
operator const T&() const override {
using Y = std::string;
static_assert(std::is_same<T, Y>::value, "");
std::string static res;
res = Base::operator const Y&();
res = Base::operator const T&();
return res;
}
};
int main() {
Derive<std::string> a;
const std::string& b = a;
(void)b;
}
Reproduced locally on:
gcc (SUSE Linux) 11.1.1 20210721 [revision
076930b9690ac3564638636f6b13bbb6bc608aea]
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Did a quick bisection via godbolt.org, the last version it's didn't occur is
7.5.
https://gcc.godbolt.org/z/KcbK9vv5z
