On Thursday, 11 February 2016 at 03:47:09 UTC, Steven
Schveighoffer wrote:
Misunderstanding.
An AA under the hood is simply a pointer. Initialized to null.
When you pass it around, you are passing a pointer. AA assign
checks for null and allocates a new AA impl to hold the data.
But this doesn't affect other copies (that were null).
So what is happening is aa() returns a null AA. You assign to
it, which allocates a new AA impl, and sets the rvalue to point
at it. The rvalue promptly disappears. The original m_aa is
still set to point at null.
Makes sense (though it defies my intuition; I would have expected
an NPE or crash at time of assignment). Thanks!
