On Saturday, 28 October 2017 at 13:24:49 UTC, Mike Wey wrote:
The following code runs correctly when compiled with ldc
(1.4.0) but fails with an assert error when compiled with dmd
(2.076 and ldc 1.2.0)
```
class A
{
}
class B
{
T opCast(T)()
{
return this;
}
}
void main()
{
A a = null;
B b = null;
auto c = cast(Object)a;
auto d = cast(Object)b; // Fails with:
core.exception.AssertError@test.d(8): null this
}
```
How would you write an opCast that would handle this case
correctly?
Testing if this is null at the start of the opCast doesn't help
since the assert is thrown before that happens.
Making the opCast static leaves us without access to this,
which would be needed in my use case.
We can't relay on ufcs since the rewrite to opCast doesn't
happen when it's not a member function.
As Basile mentioned, this is compiler sticking checks in behind
your back.
The reason it works on new LDC is because #6982 was cherry picked
to LDC (1.3?) before it was merged into dmd (not sure what
version, I though it was 2.076, but it might have been one of the
betas of 2.077) because I needed it for DCompute to build without
-release.
The only course is to use recent compilers.
