[Bug libstdc++/119259] compilation error: *constexpr* operator==(const T&) const = default` forces compilation of std::vector's operator== function

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119259

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
operator== for std::vector is not constrained, so this is the expected
behaviour.

If you default your operator== then it will try to use equality for
std::vector, which isn't constrained so is instantiated, which fails.