• bearophile (17/17) Aug 30 2011 DMD 2.055head gives no compile-time errors on this, is this expected and...
• Jonathan M Davis (6/24) Aug 30 2011 I believe that that's as expected. If the struct had member variables wh...
• Timon Gehr (19/43) Aug 30 2011 The problem is that:
• bearophile (4/13) Aug 30 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6578

bearophile <bearophileHUGS lycos.com> writes:

DMD 2.055head gives no compile-time errors on this, is this expected and
good/acceptable?


struct Foo {
    int x;
    this(int x_) { this.x = x_; }
}
void main() {
    auto f1 = new const(Foo)(1);
    f1.x++;
    auto f2 = new immutable(Foo)(1);
    f2.x++;
    auto f3 = const(Foo)(1);
    f3.x++;
    auto f4 = immutable(Foo)(1);
    f4.x++;
}


Bye and thank you,
bearophile

Jonathan M Davis <jmdavisProg gmx.com> writes:

On Tuesday, August 30, 2011 07:08:32 bearophile wrote:
 DMD 2.055head gives no compile-time errors on this, is this expected and
 good/acceptable?
 
 
 struct Foo {
     int x;
     this(int x_) { this.x = x_; }
 }
 void main() {
     auto f1 = new const(Foo)(1);
     f1.x++;
     auto f2 = new immutable(Foo)(1);
     f2.x++;
     auto f3 = const(Foo)(1);
     f3.x++;
     auto f4 = immutable(Foo)(1);
     f4.x++;
 }

I believe that that's as expected. If the struct had member variables which 
were references or pointers, then you'd need an immutable constructor to 
construct an immutable one, but in this case, it shouldn't be necessary. And I 
don't think that it's ever necessary to have a special constructor for const.

- Jonathan M Davis

Timon Gehr <timon.gehr gmx.ch> writes:

On 08/30/2011 01:19 PM, Jonathan M Davis wrote:
 On Tuesday, August 30, 2011 07:08:32 bearophile wrote:
 DMD 2.055head gives no compile-time errors on this, is this expected and
 good/acceptable?


 struct Foo {
      int x;
      this(int x_) { this.x = x_; }
 }
 void main() {
      auto f1 = new const(Foo)(1);
      f1.x++;
      auto f2 = new immutable(Foo)(1);
      f2.x++;
      auto f3 = const(Foo)(1);
      f3.x++;
      auto f4 = immutable(Foo)(1);
      f4.x++;
 }

 I believe that that's as expected. If the struct had member variables which
 were references or pointers, then you'd need an immutable constructor to
 construct an immutable one, but in this case, it shouldn't be necessary. And I
 don't think that it's ever necessary to have a special constructor for const.

 - Jonathan M Davis

The problem is that:

struct Foo {
     int x;
     this(int x_) { this.x = x_; }
}
static assert(is(typeof(new const(Foo)(1)) == Foo*));
static assert(is(typeof(new immutable(Foo)(1)) == Foo*));
static assert(is(typeof(const(Foo)(1)) == Foo));
static assert(is(typeof(immutable(Foo)(1)) == Foo));

// But:

struct Bar {
     int x;
}
static assert(is(typeof(new const(Bar)) == const(Bar)*));
static assert(is(typeof(new immutable(Bar)) == immutable(Bar)*));
static assert(is(typeof(const(Bar)(1)) == const(Bar)));
static assert(is(typeof(immutable(Bar)(1)) == immutable(Bar)));


And I'd call that a bug.

bearophile <bearophileHUGS lycos.com> writes:

Timon Gehr:

 struct Bar {
      int x;
 }
 static assert(is(typeof(new const(Bar)) == const(Bar)*));
 static assert(is(typeof(new immutable(Bar)) == immutable(Bar)*));
 static assert(is(typeof(const(Bar)(1)) == const(Bar)));
 static assert(is(typeof(immutable(Bar)(1)) == immutable(Bar)));
 
 And I'd call that a bug.

http://d.puremagic.com/issues/show_bug.cgi?id=6578

Bye,
bearophile