On Friday, 20 September 2013 at 07:57:43 UTC, Jacob Carlborg
wrote:
On 2013-09-20 08:59, ilya-stromberg wrote:
Can I explicitly specify when I can use attribute? Something
like
this:
@attribute("field")
struct matches(string mustMatch)
{
}
string wrongAttribute
{
}
class Foo
{
@matches("[0-9]+")
string someNumber; //OK, it's a field
}
@matches("[0-9]+") //Error, it's a class, not a field
class Bar
{
}
@wrongAttribute //Error, this attribute doesn't exist
class C
{
}
Unfortunately you can't. I tag all my structs which are
supposed to be used as UDA's with a @attribute UDA.
struct attribute {}
@attribute struct matches(string mustMatch) {}
Then I have some wrappers around __traits(getAttributes) that
will, by default, only return UDA's that them self have the
@attribute UDA attached to them.
https://github.com/jacob-carlborg/orange/blob/master/orange/core/Attribute.d
You could of course fix this in a library too.
enum AttributeUsage {
struct_ = 1 << 0,
class_ = 1 << 1,
//etc
}
struct attribute { AttributeUsage usage; }
Then the library could give a compile-time error if you tries to
use it where it's not meant to be.
