Eponymous template with full template syntax

[Ali Çehreli]

On 07/01/2013 12:03 PM, Maxim Fomin wrote:

 > I think that this probably worked as early as in the end of 2011 but I
 > can be wrong as don't remember exactly.

To answer Jonathan's question as well, it must have worked because I see 
it in code that is definitely tested when it was written.

 > It seems that dmd recognizes isSmall!int.isSmall as potential UFCS
 > property, converts isSmall!int to bool and tries to issue call
 > isSmall(bool) and fails, because that template does not define any
 > function.

That explains it. :) Let's play with it a little:

import std.stdio;

template isSmall(T)
{
     enum isSmall = (T.sizeof < 12345);

     struct S
     {
         T m;
     }
}

struct S
{
     int[10] i;
}

void main()
{
     writeln(isSmall!int);
     writeln(isSmall!int.S.init);
     writeln(isSmall!int.S);
}

First of all, apparently a template can include a definition with the 
same name but I still cannot type isSmall!int.isSmall. I guess the above 
is still an eponymous template and isSmall!int still means 
isSmall!int.isSmall.

Now guess what the last two lines print. :) isSmall!int.S is *not* the S 
that is included in the template! Here is the output:

true
S([0, 0, 0, 0, 0, 0, 0, 0, 0, 0])
S([1, 1, 1, 1, 1, 1, 1, 1, 1, 1])

The last line is actually an anonymous struct object of type S (the S 
that is defined at module level). That is confusing.

Ali