• Balagopal Komarath (11/11) Aug 17 2017 Is it possible to make structs containing slices support implicit
• Steven Schveighoffer (22/24) Aug 17 2017 This should "work". I don't think your static assert will pass, but the
• Balagopal Komarath (3/5) Aug 17 2017 Thanks. But, isn't my static assert testing for exactly this?
• Steven Schveighoffer (7/14) Aug 17 2017 I might be wrong. It's hard to tell, because the compiler doesn't work

Balagopal Komarath <baluks gmail.com> writes:

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
}

Steven Schveighoffer <schveiguy yahoo.com> writes:

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

Balagopal Komarath <baluks gmail.com> writes:

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?

Steven Schveighoffer <schveiguy yahoo.com> writes:

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