Missing introspection? "How exactly this type is actually used"

[Ali Çehreli]

On 5/20/22 12:41, H. S. Teoh wrote:

 > Actually, there would not be any compile-time or runtime cost if the
 > user doesn't actually use a method that requires calling the expensive
 > member.

Agreed about functions.

DbI allows one to inject member variables:

   static if (something) {
     int[1000] big;
   }

That big member cannot be optimized away if 'something' is true. Even if 
the user never uses this type in a way that necessitates that big member...

This appeared as I was designing a range type that could support 
BidirectionalRange primitives, which could make me add a buffer for 
those back elements:

   static if (isBidirectionalRange!R) {
     ElementType!R[] backElements;
   }

As you can see, the type is going out of its way to be helpful. But it 
costs the user even if they don't use .back or .popBack().

Ali