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digitalmars.D.learn - Template

reply Vladimir <v.voinkov gmail.com> writes:
I tried to use common c++ technique in D:

class Super (alias T)
{
	alias T.Type A; >>> Error: no property 'Type' for type xxx.Sub'

	void test()
	{
		alias T.Type B; >>> ok
	}
}

class Sub : Super !(Sub)
{
	alias int Type;
}

alias A fails to compile although alias B inside scope of function is ok. Is
that intended? What is the idea behind that?

Vladimir
Aug 09 2007
parent reply Regan Heath <regan netmail.co.nz> writes:
Vladimir wrote:

 I tried to use common c++ technique in D:
 
 class Super (alias T)
 {
 	alias T.Type A; >>> Error: no property 'Type' for type xxx.Sub'
 
 	void test()
 	{
 		alias T.Type B; >>> ok
 	}
 }
 
 class Sub : Super !(Sub)
 {
 	alias int Type;
 }
 
 alias A fails to compile although alias B inside scope of function is ok. Is
that intended? What is the idea behind that?



I suspect it must have something to do with 'Sub' not being defined at 
the point where you're using it as a template parameter.

This compiles:

class Super (T)
{
	alias T.Type A;

	void test()
	{
		alias T.Type B;
	}
}

class Temp
{
	alias int Type;
}

class Sub : Super !(Temp)
{
	alias int Type;
}

void main() {}

Incidently, notice that I'm not using 'alias' in my Super template.  It 
doesn't seem to be required.

Regan
Aug 09 2007
parent reply Vladimir <v.voinkov gmail.com> writes:
Regan Heath Wrote:


 Vladimir wrote:

 I tried to use common c++ technique in D:
 
 class Super (alias T)
 {
 	alias T.Type A; >>> Error: no property 'Type' for type xxx.Sub'
 
 	void test()
 	{
 		alias T.Type B; >>> ok
 	}
 }
 
 class Sub : Super !(Sub)
 {
 	alias int Type;
 }
 
 alias A fails to compile although alias B inside scope of function is ok. Is
that intended? What is the idea behind that?



 I suspect it must have something to do with 'Sub' not being defined at 
 the point where you're using it as a template parameter.
 
 This compiles:
 
 class Super (T)
 {
 	alias T.Type A;
 
 	void test()
 	{
 		alias T.Type B;
 	}
 }
 
 class Temp
 {
 	alias int Type;
 }
 
 class Sub : Super !(Temp)
 {
 	alias int Type;
 }
 
 void main() {}
 
 Incidently, notice that I'm not using 'alias' in my Super template.  It 
 doesn't seem to be required.
 
 Regan



Thanks for quick response. Your workarrond is suitable.  I wonder should it be
considered as a bug and subject for future fix?
Aug 09 2007
parent Regan Heath <regan netmail.co.nz> writes:
Vladimir wrote:

 Regan Heath Wrote:
 

 Vladimir wrote:

 I tried to use common c++ technique in D:

 class Super (alias T)
 {
 	alias T.Type A; >>> Error: no property 'Type' for type xxx.Sub'

 	void test()
 	{
 		alias T.Type B; >>> ok
 	}
 }

 class Sub : Super !(Sub)
 {
 	alias int Type;
 }

 alias A fails to compile although alias B inside scope of function is ok. Is
that intended? What is the idea behind that?



 the point where you're using it as a template parameter.

 This compiles:

 class Super (T)
 {
 	alias T.Type A;

 	void test()
 	{
 		alias T.Type B;
 	}
 }

 class Temp
 {
 	alias int Type;
 }

 class Sub : Super !(Temp)
 {
 	alias int Type;
 }

 void main() {}

 Incidently, notice that I'm not using 'alias' in my Super template.  It 
 doesn't seem to be required.

 Regan



 Thanks for quick response. Your workarrond is suitable.  I wonder should it be
considered as a bug and subject for future fix?



I think you should post it to bugzilla, if it's a bug it will get dealt 
with eventually, if not it will get dealt with eventually.  :)

Regan
Aug 09 2007