• Jack Applegame (14/14) Jan 06 2016 import std.algorithm;
• anonymous (13/26) Jan 06 2016 Assuming you meant `arr[0].b = 4;`. Just overwriting the mutable part of...
• Jack Applegame (5/10) Jan 07 2016 I think it isn't a bug. I'm not overwriting immutable data, I'm
• anonymous (4/7) Jan 07 2016 I don't think it's move's purpose to ignore the type system like that.

Jack Applegame <japplegame gmail.com> writes:

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?
}

anonymous <anonymous example.com> writes:

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.

 }

Jack Applegame <japplegame gmail.com> writes:

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.

anonymous <anonymous example.com> writes:

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.