Below program has been reduced as far as possible to show the issue encountered with Visual Studio C++ compiler.

f is some algorithm function taking on input predicate object P p, which has user-defined copy constructor that remembers the pointer on the source object. In that constructor it is checked that source and copy objects are distinct indeed if (s == this) throw 0; but in operator () the same check returns the opposite result:

struct P {
    const P * s = nullptr;
    constexpr P() {}
    constexpr P(const P & p) : s(&p) {
        if (s == this) throw 0; // never happens
    }
    constexpr bool operator()() const {
        return s != this; // shall be always true?
    }
};

constexpr bool f(P p) {
    return p.s ? p() : f(p);
}

int main() {
    static_assert( f(P{}) ); // fails in MSVC, where static_assert( f(P{}) == false );
}

Online demo: https://gcc.godbolt.org/z/nqYoshExj

How can one explain that the same check passes in an object’s constructor, but then fails in its method?