https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102028
Bug ID: 102028
Summary: std::ostream& used as std::stringstream&
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lars.maier at tefax dot net
Target Milestone: ---
The following code compiles, although it shouldn't:
```
#include <sstream>
#include <iostream>
void foo(std::stringstream const&);
struct A {
friend auto operator<<(std::ostream& os, A const&) -> std::ostream&;
};
int main() {
foo(std::stringstream{} << A{});
return 0;
}
```
Reason: the result of operator<< with std::stringstream and A const& is just an
std::ostream& and you should not be able to call foo on such an reference.
