Compiling the following code:

	import std.typecons;

	class Foo
	{
		private int foo;

		mixin Proxy!(foo);

		this(int x)
		{
			this.foo = x;
		}
	}

	void main()
	{
	}

Produces this error:

:!rdmd --force -de -debug -w test.d
/usr/include/dmd/phobos/std/typecons.d(4043): Error: template instance isArray!(typeof(a)) template 'isArray' is not defined
test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating
Failed: ["dmd", "-de", "-debug", "-w", "-v", "-o-", "test.d", "-I."]

Can anyone else confirm or am i doing something wrong. I'm using DMD 2.066.0 64bit Ubuntu 14.04.

On 08/25/2014 11:10 AM, Gary Willoughby wrote:
> Compiling the following code:
>
>      import std.typecons;
>
>      class Foo
>      {
>          private int foo;
>
>          mixin Proxy!(foo);
>
>          this(int x)
>          {
>              this.foo = x;
>          }
>      }
>
>      void main()
>      {
>      }
>
> Produces this error:
>
> :!rdmd --force -de -debug -w test.d
> /usr/include/dmd/phobos/std/typecons.d(4043): Error: template instance
> isArray!(typeof(a)) template 'isArray' is not defined
> test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating
> Failed: ["dmd", "-de", "-debug", "-w", "-v", "-o-", "test.d", "-I."]
>
> Can anyone else confirm or am i doing something wrong. I'm using DMD
> 2.066.0 64bit Ubuntu 14.04.

isArray is defined in std.traits. I don't know why it doesn't work even though std.typecons does import it.

The workaround is to import it yourself in your program:

import std.traits;

Ali

On Monday, 25 August 2014 at 18:10:33 UTC, Gary Willoughby wrote:
> :!rdmd --force -de -debug -w test.d
> /usr/include/dmd/phobos/std/typecons.d(4043): Error: template instance isArray!(typeof(a)) template 'isArray' is not defined
> test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating
> Failed: ["dmd", "-de", "-debug", "-w", "-v", "-o-", "test.d", "-I."]
>
> Can anyone else confirm or am i doing something wrong. I'm using DMD 2.066.0 64bit Ubuntu 14.04.

It stopped working after this PR was merged:

https://github.com/D-Programming-Language/phobos/pull/1899

But I suspect that something else is going on. The PR only introduced the call to `isArray` into `std.typecons.Proxy`.

On 08/25/2014 11:38 AM, "Marc Schütz" <schuetzm@gmx.net>" wrote:

> On Monday, 25 August 2014 at 18:10:33 UTC, Gary Willoughby wrote:
>> :!rdmd --force -de -debug -w test.d
>> /usr/include/dmd/phobos/std/typecons.d(4043): Error: template instance
>> isArray!(typeof(a)) template 'isArray' is not defined
>> test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating
>> Failed: ["dmd", "-de", "-debug", "-w", "-v", "-o-", "test.d", "-I."]
>>
>> Can anyone else confirm or am i doing something wrong. I'm using DMD
>> 2.066.0 64bit Ubuntu 14.04.
>
> It stopped working after this PR was merged:
>
> https://github.com/D-Programming-Language/phobos/pull/1899
>
> But I suspect that something else is going on. The PR only introduced
> the call to `isArray` into `std.typecons.Proxy`.

It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation.

Ali

On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote:
> It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation.

You're right, that's it! It works when I import std.traits first.

So... the fix is to import std.traits inside template Proxy. Going to submit a PR.

On Monday, 25 August 2014 at 19:12:48 UTC, Marc Schütz wrote:
> On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote:
>> It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation.
>
> You're right, that's it! It works when I import std.traits first.
>
> So... the fix is to import std.traits inside template Proxy. Going to submit a PR.

https://github.com/D-Programming-Language/phobos/pull/2463

On Monday, 25 August 2014 at 19:17:22 UTC, Marc Schütz wrote:
> On Monday, 25 August 2014 at 19:12:48 UTC, Marc Schütz wrote:
>> On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote:
>>> It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation.
>>
>> You're right, that's it! It works when I import std.traits first.
>>
>> So... the fix is to import std.traits inside template Proxy. Going to submit a PR.
>
> https://github.com/D-Programming-Language/phobos/pull/2463

Smashing, ta.

On 08/25/2014 12:17 PM, "Marc Schütz" <schuetzm@gmx.net>" wrote:
> On Monday, 25 August 2014 at 19:12:48 UTC, Marc Schütz wrote:
>> On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote:
>>> It can be explained if the mixed-in template is evaluated at the
>>> mixin context without bringing in the imported modules to that
>>> context. I don't know whether it is true or whether it is a known
>>> limitation.
>>
>> You're right, that's it! It works when I import std.traits first.
>>
>> So... the fix is to import std.traits inside template Proxy. Going to
>> submit a PR.
>
> https://github.com/D-Programming-Language/phobos/pull/2463

Thanks! And I learned from you in the pull request the following fact:

<quote>
Quoting http://dlang.org/template-mixin :
"Unlike a template instantiation, a template mixin's body is evaluated within the scope where the mixin appears, not where the template declaration is defined. It is analogous to cutting and pasting the body of the template into the location of the mixin."
</quote>

Ali

On Monday, 25 August 2014 at 21:14:42 UTC, Ali Çehreli wrote:
> On 08/25/2014 12:17 PM, "Marc Schütz" <schuetzm@gmx.net>" wrote:
>> On Monday, 25 August 2014 at 19:12:48 UTC, Marc Schütz wrote:
>>> On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote:
>>>> It can be explained if the mixed-in template is evaluated at the
>>>> mixin context without bringing in the imported modules to that
>>>> context. I don't know whether it is true or whether it is a known
>>>> limitation.
>>>
>>> You're right, that's it! It works when I import std.traits first.
>>>
>>> So... the fix is to import std.traits inside template Proxy. Going to
>>> submit a PR.
>>
>> https://github.com/D-Programming-Language/phobos/pull/2463
>
> Thanks! And I learned from you in the pull request the following fact:
>
> <quote>
> Quoting http://dlang.org/template-mixin :
> "Unlike a template instantiation, a template mixin's body is evaluated within the scope where the mixin appears, not where the template declaration is defined. It is analogous to cutting and pasting the body of the template into the location of the mixin."
> </quote>
>
> Ali

With that in mind what is strange is that if in my example you change the class for a struct everything works as expected. Why is that?

On Tuesday, 26 August 2014 at 18:13:52 UTC, Gary Willoughby wrote:
> With that in mind what is strange is that if in my example you change the class for a struct everything works as expected. Why is that?

This is bizarre... I tried a few things, but I have no idea. At first I thought the `static if` that calls `isArray` is inside another `static if`, but this is not the case.

Might be a compiler bug?