Default move constructor and reference members

Question

From [12.8] [11] of N3337:

The implicitly-defined copy/move constructor for a non-union class X performs a memberwise copy/move of its bases and members. [ N

Answer 1

It's handled by the specification of class member access expressions. The key part is

Let x be either the parameter of the constructor or, for the move constructor, an xvalue referring to the parameter.

In other words, a defaulted move constructor for

struct X { int x, &y; };

does the equivalent of

X::X(X&& other) : x(std::move(other).x), y(std::move(other).y) {}

The important thing here is that the result of a class member access expression x.m, where m names a non-static data member, is always an lvalue if m has reference type, but an xvalue if x is an rvalue and m has non-reference type. (See [expr.ref]/4.) This ensures that lvalue reference members will be initialized with lvalues.