On Wednesday, 16 October 2013 at 17:55:14 UTC, H. S. Teoh wrote:
Maybe it's helpful to understand how D's const system works. The
following diagram may help (please excuse the ASCII graphics):
const
/ \
mutable immutable
I think people in this thread know how const works, but some
think it is broken. Scenario is this:
Library code:
struct Foo { int x; }
User code:
Foo f;
immutable f2 = f;
This works, even though the library writer might not have
anticipated that someone makes Foo immutable. However, now the
library writer obliviously releases a new version of the library,
which extends it like this:
struct Foo {
int x;
private int[] history;
}
Unfortunately, now the user code is broken due to the freshly
introduced mutable aliasing. Personally, I think is fine. Upon
compilation the user code gives a error message and user
developer can adapt to the code to the new library version. Some
think the library writer should have a possibility to make this
work.
