Lifetime of temporary object is extended until the end of scope of reference to subobject.

rvalue-reference-to-temporary-subobject.cpp

#include <iostream>

struct Foo {
	~Foo() { std::cout << "~Foo()\n"; }
};

struct Bar {
	Foo foo;
	~Bar() { std::cout << "~Bar()\n"; }
};

int main() {
	auto&& foo = Bar{}.foo;
	std::cout << "exit\n";
}

In this particular case, the lifetime of temporary Bar{} is prolonged until the scope of foo ends.