Convertible to mutable buffer requirements

A type that meets the requirements for convertibility to a mutable buffer must meet the requirements of CopyConstructible types (C++ Std, 20.1.3), and the requirements of Assignable types (C++ Std, 23.1).

In the table below, X denotes a class meeting the requirements for convertibility to a mutable buffer, a and b denote values of type X, and u, v and w denote identifiers.

Table 7. ConvertibleToMutableBuffer requirements

expression	postcondition
mutable_buffer u(a); mutable_buffer v(a);	buffer_cast<void>(u) == buffer_cast<void>(v) && buffer_size(u) == buffer_size(v)
mutable_buffer u(a); mutable_buffer v = a;	buffer_cast<void>(u) == buffer_cast<void>(v) && buffer_size(u) == buffer_size(v)
mutable_buffer u(a); mutable_buffer v; v = a;	buffer_cast<void>(u) == buffer_cast<void>(v) && buffer_size(u) == buffer_size(v)
mutable_buffer u(a); const X& v = a; mutable_buffer w(v);	buffer_cast<void>(u) == buffer_cast<void>(w) && buffer_size(u) == buffer_size(w)
mutable_buffer u(a); X v(a); mutable_buffer w(v);	buffer_cast<void>(u) == buffer_cast<void>(w) && buffer_size(u) == buffer_size(w)
mutable_buffer u(a); X v = a; mutable_buffer w(v);	buffer_cast<void>(u) == buffer_cast<void>(w) && buffer_size(u) == buffer_size(w)
mutable_buffer u(a); X v(b); v = a; mutable_buffer w(v);	buffer_cast<void>(u) == buffer_cast<void>(w) && buffer_size(u) == buffer_size(w)

expression

postcondition

mutable_buffer u(a);
mutable_buffer v(a);

buffer_cast<void*>(u) == buffer_cast<void*>(v)
  && buffer_size(u) == buffer_size(v)

mutable_buffer u(a);
mutable_buffer v = a;

buffer_cast<void*>(u) == buffer_cast<void*>(v)
  && buffer_size(u) == buffer_size(v)

mutable_buffer u(a);
mutable_buffer v; v = a;

buffer_cast<void*>(u) == buffer_cast<void*>(v)
  && buffer_size(u) == buffer_size(v)

mutable_buffer u(a);
const X& v = a;
mutable_buffer w(v);

buffer_cast<void*>(u) == buffer_cast<void*>(w)
  && buffer_size(u) == buffer_size(w)

mutable_buffer u(a);
X v(a);
mutable_buffer w(v);

buffer_cast<void*>(u) == buffer_cast<void*>(w)
  && buffer_size(u) == buffer_size(w)

mutable_buffer u(a);
X v = a;
mutable_buffer w(v);

buffer_cast<void*>(u) == buffer_cast<void*>(w)
  && buffer_size(u) == buffer_size(w)

mutable_buffer u(a);
X v(b); v = a;
mutable_buffer w(v);

buffer_cast<void*>(u) == buffer_cast<void*>(w)
  && buffer_size(u) == buffer_size(w)