On Monday, 24 December 2018 at 11:23:32 UTC, Johan Engelen wrote:
On Sunday, 23 December 2018 at 14:07:04 UTC, Johannes Loher
wrote:
[...]
The types of the 2nd and 3rd arguments of `cas` do not have to
be the same, and aren't in your case. I think what's happening
is that you are overwriting `testInterface` with a pointer to a
TestClass which is not a valid TestInterface pointer. And then
the program does something invalid because, well, you enter UB
land.
Fixed by:
```
cas(&testInterface, testInterface, cast(shared(TestInterface))
new shared TestClass).writeln;
```
Note the cast!
Whether this is a bug in `cas` or not, I don't know. The `cas`
template checks whether the 3rd can be assigned to the 1st
argument (`*here = writeThis;`) which indeed compiles _with_ an
automatic conversion. But then the implementation of `cas` does
not do any automatic conversions (casts to `void*`). Hence the
problem you are seeing.
-Johan
Thanks a lot for the info, that clarifies things a bit. But it
still leaves the question, why it works correctly when inheriting
from an abstract class instead of implementing an interface...
Any idea about why that?
