user-defined types with overloaded operator<< don't work after 7.0.3

[odygrd]

It looks like that user defined types with an overloaded operator<<, no longer work when they are used in a container.

Broken example with fmt 7.1.x

https://godbolt.org/z/z1jn66

the same example compiles fine with fmt 7.0.x

https://godbolt.org/z/Wqbjsf

[MikeGitb]

I'm having the same problem with user defined types that have an implicit conversion to std::string_view:

https://godbolt.org/z/EWfo1h

#include <fmt/core.h>
#include <fmt/format.h>
#include <fmt/ranges.h>

#include <string_view>

struct Foo {
    operator std::string_view() const { return "Hello";}
};

int main() {
    std::vector<Foo> v(5);
    fmt::print("{}", v);
}

[vitaut]

This is caused by 2f7e088. We should probably add support for the fallback_formatter there.

[odygrd]

It would be nice if this is fixed as part of the next release, it has broken backward compatibility with the previous fmt versions

[vitaut]

Yes, that's the plan.

[vitaut]

Fixed in a036cc9.