• Zhouxuan (62/62) Oct 03 2013 ////////////////////////////////////////////////////////////
• Zhouxuan (2/2) Oct 03 2013 bug again!
• Zhouxuan (2/2) Oct 03 2013 http://d.puremagic.com/issues/show_bug.cgi?id=11169
• deadalnix (9/71) Oct 03 2013 this is invalid here. Not sure what you try to achieve via this
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (31/44) Oct 03 2013 static if.
• Zhouxuan (4/29) Oct 03 2013 Indeed I found the issue from use of isAbstractClass, but after
• Timon Gehr (7/20) Nov 07 2013 It has to delay it's value until it has seen as much as possible without...
• Zhouxuan (2/16) Oct 03 2013 I want to define some variables in non-abstract class.

"Zhouxuan" <pycerl qq.com> writes:

////////////////////////////////////////////////////////////
//case 1

class A
{
     abstract void foo();
}

class B : A
{
     static if( __traits(isAbstractClass, typeof(this) ))
     {
     }

     override void foo()
     {
     }
}

void main()
{
     B b = new B();
}

//Error: cannot create instance of abstract class B
////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////
//case 2

abstract class A
{
     void foo();
}

class B : A
{
     static if( __traits(isAbstractClass, typeof(this) ))
     {
     }

     override void foo()
     {
     }
}

void main()
{
     B b = new B();
}

//Okay
////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////
//case 3

class A
{
     abstract void foo();
}

class B : A
{
     override void foo()
     {
     }
}

void main()
{
     B b = new B();
}

//Okay
////////////////////////////////////////////////////////////



Do you guys never used abstract class?

"Zhouxuan" <pycerl qq.com> writes:

bug again!
http://forum.dlang.org/thread/rufoxrnrvlyqdsvnyfjf forum.dlang.org

"Zhouxuan" <pycerl qq.com> writes:

http://d.puremagic.com/issues/show_bug.cgi?id=11169
http://d.puremagic.com/issues/show_bug.cgi?id=11170

"deadalnix" <deadalnix gmail.com> writes:

On Friday, 4 October 2013 at 05:07:53 UTC, Zhouxuan wrote:
 ////////////////////////////////////////////////////////////
 //case 1

 class A
 {
     abstract void foo();
 }

 class B : A
 {
     static if( __traits(isAbstractClass, typeof(this) ))

this is invalid here. Not sure what you try to achieve via this 
static if.

     {
     }

     override void foo()
     {
     }
 }

 void main()
 {
     B b = new B();
 }

 //Error: cannot create instance of abstract class B

That is a bug.

 ////////////////////////////////////////////////////////////

 ////////////////////////////////////////////////////////////
 //case 2

 abstract class A
 {
     void foo();
 }

 class B : A
 {
     static if( __traits(isAbstractClass, typeof(this) ))
     {
     }

     override void foo()
     {
     }
 }

 void main()
 {
     B b = new B();
 }

 //Okay

It shouldn't, A.foo is not defined. You should get a link error.

 ////////////////////////////////////////////////////////////

 ////////////////////////////////////////////////////////////
 //case 3

 class A
 {
     abstract void foo();
 }

 class B : A
 {
     override void foo()
     {
     }
 }

 void main()
 {
     B b = new B();
 }

 //Okay

This one work as expected :D

 ////////////////////////////////////////////////////////////



 Do you guys never used abstract class?

Not that much. Note that error comes up when abstract is mixed 
with static if and compile time reflection, both are not present 

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 10/03/2013 11:10 PM, deadalnix wrote:

 On Friday, 4 October 2013 at 05:07:53 UTC, Zhouxuan wrote:
 ////////////////////////////////////////////////////////////
 //case 1

 class A
 {
     abstract void foo();
 }

 class B : A
 {
     static if( __traits(isAbstractClass, typeof(this) ))

 this is invalid here. Not sure what you try to achieve via this 

static if.

Well, obviously that is the reason for the bug. :) I think Zhouxuan 
thinks that it is an 'abstract' bug but actually it is some sort of 
__traits caching issue.

It would indeed be weird for isAbstractClass to delay its value until 
the whole class definition is seen.

Instead, what seems to happen is that isAbstractClass caches the first 
value that it determines and perhaps at least for consistency uses that 
value. Moving isAbstractClass after the definition of B.foo removes the 
issue in this case:

class A
{
     abstract void foo();
}

class B : A
{
     override void foo()
     {
     }

     // Added by Ali:
     pragma(msg, __traits(isAbstractClass, typeof(this)));

     static if( __traits(isAbstractClass, typeof(this) ))
     {
     }
}

void main()
{
     B b = new B();    // now compiles
}

Ali

"Zhouxuan" <pycerl qq.com> writes:

On Friday, 4 October 2013 at 06:22:57 UTC, Ali Çehreli wrote:
 On 10/03/2013 11:10 PM, deadalnix wrote:

 On Friday, 4 October 2013 at 05:07:53 UTC, Zhouxuan wrote:
 ////////////////////////////////////////////////////////////
 //case 1

 class A
 {
     abstract void foo();
 }

 class B : A
 {
     static if( __traits(isAbstractClass, typeof(this) ))

 this is invalid here. Not sure what you try to achieve via

 this static if.

 Well, obviously that is the reason for the bug. :) I think 
 Zhouxuan thinks that it is an 'abstract' bug but actually it is 
 some sort of __traits caching issue.

 It would indeed be weird for isAbstractClass to delay its value 
 until the whole class definition is seen.

 Instead, what seems to happen is that isAbstractClass caches 
 the first value that it determines and perhaps at least for 
 consistency uses that value. Moving isAbstractClass after the 
 definition of B.foo removes the issue in this case:

Indeed I found the issue from use of isAbstractClass, but after 
some
tests I'm confused by these abstract use cases.

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

On 10/04/2013 08:22 AM, Ali Çehreli wrote:
  >>
  >> class B : A
  >> {
  >>     static if( __traits(isAbstractClass, typeof(this) ))
  >
  > this is invalid here. Not sure what you try to achieve via this
 static if.

 Well, obviously that is the reason for the bug. :) I think Zhouxuan
 thinks that it is an 'abstract' bug but actually it is some sort of
 __traits caching issue.

 It would indeed be weird for isAbstractClass to delay its value until
 the whole class definition is seen.
 ...

It has to delay it's value until it has seen as much as possible without 
knowing it. Then eg. emit a compile time error if the body of the static 
if actually changes the determined fact. (Or use some sound relaxation 
of that rule.) Many compile-time reflection features can be used to 
provoke this kind of issue. (E.g. write a class that subclasses another 
class iff it cannot access some protected field of it.)

"Zhouxuan" <pycerl qq.com> writes:

On Friday, 4 October 2013 at 06:10:30 UTC, deadalnix wrote:
 On Friday, 4 October 2013 at 05:07:53 UTC, Zhouxuan wrote:
 ////////////////////////////////////////////////////////////
 //case 1

 class A
 {
    abstract void foo();
 }

 class B : A
 {
    static if( __traits(isAbstractClass, typeof(this) ))

 this is invalid here. Not sure what you try to achieve via this 
 static if.

I want to define some variables in non-abstract class.