what operator(s) should I overload to prevent this?

Biotronic simen.kjaras at gmail.com
Mon Oct 16 12:18:05 UTC 2017


On Monday, 16 October 2017 at 12:00:13 UTC, drug wrote:
> I refactored `MyStructure` added own implementation of malloced 
> array based on pureRealloc/pureFree instead of dynamic array I 
> used before and now I have error:
> Error: cannot implicitly convert expression get(msg.getData()) 
> of type const(MyStructure) to MyStructure.
>
> What operators should I overload to let this conversion? I've 
> tryed opCast and it fails in other call sites, also I've tried 
> opAssign - it didn't works, what worked is wrapping in ctor - 
> MyStruct(const_var). But using ctor is not convenient.

The reason this doesn't work is you have some sort of 
non-immutable pointer, reference or array in your struct. I'm not 
sure why this worked before, since I have no idea what your code 
looks like. Hence, I can only give limited advice. Notably, the 
reasons this gives you a warning is because it would be unsafe to 
do a simple cast.

You might have turned immutable(T)[] into T[] (where T is int, 
byte, char, what-have-you). If this is the case, consider why 
this happened, and try to turn it back into immutable(T)[]. The 
same goes for immutable(T)*. Remember that an alias can make 
something immutable, so it might not be immediately obvious.

If you're fine with being unsafe, and can't find a solution like 
the above, consider this:

struct MyStruct {
     MyStruct getUnsafe() const {
         return cast(MyStruct)this;
     }
     alias getUnsafe this;
}

--
   Biotronic


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