import std.algorithm;

struct Bar {
    const int a;
    int b;
}

void main() {
    Bar[1] arr;
    Bar bar = Bar(1, 2);
    bar[0].b = 4;
    move(bar, arr[0]);       // ok
    arr[1] = bar;            // fail, why?
    move(Bar(1, 2), arr[0]); // fail, why source parameter isn't auto ref?
}

On 06.01.2016 23:04, Jack Applegame wrote:
> import std.algorithm;
>
> struct Bar {
>      const int a;
>      int b;
> }
>
> void main() {
>      Bar[1] arr;
>      Bar bar = Bar(1, 2);
>      bar[0].b = 4;

Assuming you meant `arr[0].b = 4;`. Just overwriting the mutable part of bar[0] is ok, of course.

>      move(bar, arr[0]);       // ok

I consider it a bug that this compiles. You're overwriting immutable data, which shouldn't be possible (without casting). https://issues.dlang.org/show_bug.cgi?id=15315

>      arr[1] = bar;            // fail, why?

Assuming you meant `arr[0] = bar;`.

The error message isn't too bad here: "Error: cannot modify struct arr[0] Bar with immutable members". You're trying to overwrite immutable data, that's not allowed.

>      move(Bar(1, 2), arr[0]); // fail, why source parameter isn't auto ref?

I'm not sure about the details. Maybe it would make sense for `move` to accept rvalues, maybe not. Breaking immutable is certainly not a good reason to do it, though.

> }

On Thursday, 7 January 2016 at 00:19:12 UTC, anonymous wrote:
> On 06.01.2016 23:04, Jack Applegame wrote:
>
>>      move(bar, arr[0]);       // ok
>
> I consider it a bug that this compiles. You're overwriting immutable data, which shouldn't be possible (without casting). https://issues.dlang.org/show_bug.cgi?id=15315
>
I think it isn't a bug. I'm not overwriting immutable data, I'm replacing old data with a new constructed one. I want to destruct old data and fill uninitialized raw memory with a new constructed one.

On 07.01.2016 09:16, Jack Applegame wrote:
> I think it isn't a bug. I'm not overwriting immutable data, I'm
> replacing old data with a new constructed one. I want to destruct old
> data and fill uninitialized raw memory with a new constructed one.

I don't think it's move's purpose to ignore the type system like that. If it was, it would need more warning signs and preferably a more obscure name.