What are the unused but useful feature you know in D?

[codephantom]

On Sunday, 25 June 2017 at 23:21:25 UTC, aberba wrote:
> Can you share feature(s) in D people are not talking about 
> which you've found very useful?

How about this feature: i.e. it actually compiles just fine ;-)

//------------------------------------------------------------

module test;

void main()
{
     void main()
     {
         void main()
         {
             void main()
             {
                 void main()
                 {
                     void main()
                     {
                         void main()
                         {
                             //and so on... and so on....and so 
on....
                         }
                     }
                 }
             }

         }
     }
}

//------------------------------------------------------------