Should we have an Unimplemented Attribute?

[Jonathan M Davis]

On Thursday 03 February 2011 03:02:04 Jacob Carlborg wrote:
> On 2011-02-03 00:38, Piotr Szturmaj wrote:
> > Andrej Mitrovic wrote:
> >> We know what a Deprecated Attribute is for:
> >> http://www.digitalmars.com/d/2.0/attribute.html#deprecated.
> >> 
> >> You can use a compiler switch to enable using these:
> >> -d
> >> allow deprecated features
> >> 
> >> But what about structs/classes/functions/etc which are partially
> >> implemented, but still unusable? Marking them with deprecated doesn't
> >> make sense, as this will likely confuse both the user and the library
> >> writers. Would it be overkill to introduce a new attribute?
> >> 
> >> The idea came after I've spent some good time trying to get druntime's
> >> getMembers function to work in my code, only to find out from this NG
> >> that it's not properly implemented.
> >> 
> >> Discuss?
> > 
> > In C# there is NotImplementedException for that.
> > 
> > public class A
> > {
> > public int foo()
> > {
> > throw new NotImplementedException();
> > }
> > }
> > 
> > I see people ask for new attributes. Why not add user defined attributes
> > into language? C# has custom attributes and Java has custom annotations.
> > 
> > Custom attributes could be just classes (as in C#):
> > 
> > class GuidAttribute : Attribute
> > {
> > string guid;
> > 
> > this(string guid)
> > {
> > this.guid = guid;
> > }
> > }
> > 
> > used like this (COM interfaces):
> > 
> > @Guid("48eecd81-35d7-4d4e-9ab8-479a38713053")
> > interface MyInterface
> > {
> > byte foo();
> > ulong bar();
> > }
> > 
> > or used for ORM:
> > 
> > @DBTable("users")
> > struct UserRow
> > {
> > @NotNull string username;
> > @NotNull string password
> > ubyte age;
> > }
> > 
> > There would be also need for some method to enumerate those attributes
> > at compile time/run time. We already have that possibility for
> > predefined attributes.
> 
> I would love to have user defined attributes/annotations.

I agree with that whole-heartedly. They really should be added at some point, 
though since they should be backwards compatible, there's not necessarily any 
rush given everything else that needs to be done. Still, I don't think that we 
need an attribute for this particular case.

- Jonathan M Davis