Initialization of std.typecons.RefCounted objects

[Matthias Walter]

Hi,

I looked at Bug #6153 (Array!(Array!int) failure) and found that the
reason is the following behavior:

Given some type T you wrap as RefCounted!T object, then proper use of
the auto-initialization feature or manual initialization on demand
ensures that no null-pointer dereference will happen. But the other
problem is that as long as the wrapped object is uninitialized, the
object behaves like a value type instead of a reference type.

This exactly is what makes the following code fail:

Array!(Array!int) array2d;
array2d.length = 1;
array2d[0].insert(1);

The inner array "array2d[0]" was not initialized and hence the reference
pointer is null. Since Array.opIndex returns by value, the 'insert'
method is called on a temporary object and does not affect the inner
array (still being empty) which is stored in the outer array.

What do you think about this?

Must the user ensure that the Array container is always initialized
explicitly? If yes, how shall this happen since the only constructor
takes a (non-empty) tuple of new elements. Or shall opIndex return by
reference?

The problem arises in the same way if Array was a class - but then the
user typically knows that after enlarging the outer array, the inner
array is a null pointer which must be created by new.

Best regards,

Matthias Walter