Is it possible to make structs containing slices support implicit conversion from const to mutable? I tried adding a postblit that dupes the member 'a'. That didn't work.

struct A
{
    int[] a;
}

void main()
{
    static assert (is(const(A) : A)); // fails
}

On 8/17/17 3:24 PM, Balagopal Komarath wrote:
> Is it possible to make structs containing slices support implicit conversion from const to mutable?

This should "work". I don't think your static assert will pass, but the main function below should run.

struct A
{
   int[] a;
   A dup() const
   {
       return A(a.dup);
   }
   alias dup this;
}

void main()
{
	const A a;
	A a2 = a;
}

However, this results in a segfault as far back as 2.064, and 2.063 doesn't seem to like it (but maybe because alias this wasn't supported? I'm not sure).

https://issues.dlang.org/show_bug.cgi?id=17759

-Steve

On Thursday, 17 August 2017 at 20:22:09 UTC, Steven Schveighoffer wrote:
>
> This should "work". I don't think your static assert will pass, but the main function below should run.

Thanks. But, isn't my static assert testing for exactly this?

On 8/17/17 5:28 PM, Balagopal Komarath wrote:
> On Thursday, 17 August 2017 at 20:22:09 UTC, Steven Schveighoffer wrote:
>>
>> This should "work". I don't think your static assert will pass, but the main function below should run.
> 
> Thanks. But, isn't my static assert testing for exactly this?
> 

I might be wrong. It's hard to tell, because the compiler doesn't work with the struct itself.

If I change the alias this to something else, your form of conversion does work. But the compiler may recognize that specific form and still disallow it. IMO, that would be a further bug.

-Steve