Jacob Carlborg wrote:
On 2012-04-06 14:38, Piotr Szturmaj wrote:
Do you mean return type? I think your syntax has some serious
disadvantages. Consider parameters and multiple attributes.
For return types I'd like to see something like this:
@return: not_null
@return: MyAttr("foo")
Foo bar(@custom int a) {}
This is similar to C#'s [return: MyAttr]. Alternatively it might be:
@return(not_null)
@return(MyAttr("foo"))
Hmm, or something like how Java does it. You attached this information
when you declare the attribute:
@Retention(RetentionPolicy.RUNTIME) // Make this annotation accessible
at runtime via reflection.
@Target({ElementType.METHOD}) // This annotation can only be applied to
class methods.
public @interface Tweezable {
}
Or with another syntax:
@attribute @target(type) struct not_null {}
I think that @target is a solution for simple types, but UDTs may use
another one:
struct MyAttr
{
template Attach(Symbol)
{
static if (!is(typeof(Symbol) == class) || !is(typeof(Symbol) : A))
static assert(0, "MyAttr must be attached to classes
derived from class A");
}
}
This allows more complex target checking possible. Besides above
example, some attributes can be mutually exclusive and
__traits(hasAttribute, ...) may be used to check that.
