User Defined Attributes

[Adam D. Ruppe]

On Tuesday, 6 November 2012 at 16:41:22 UTC, Walter Bright wrote:
> It would be a significant extension, and so I'd like to see a 
> compelling use case first.

What do you consider to be compelling use cases for UDAs on 
functions?

Going back to the links on the original post, we have:

"I have numerous systems that need to scan the module for things 
marked accordingly to automate bindings to their respective 
systems."

Putting them on parameters also helps with this. Script languages 
have to deal with parameters. Editors might. And, of course, I've 
already talked about automatic UI generation.


Here's another one: named parameters. Of course, there's D names, 
but suppose you have to hook into another naming scheme that uses 
characters that aren't valid D names?

An external system might send you "log-in?user-id=foo". You are 
doing a library to automatically call a class:

class Handler {
   [ExternalName("log-in")] /* we can do this now */
     void logIn([ExternalName("user-id")] string userId) {}
       /* but the parameter, which is the same concept, doesn't 
work */
}