On Friday, 6 April 2012 at 13:23:03 UTC, Steven Schveighoffer
wrote:
OK, so I woke up this morning to find a huge discussion on
attributes, and I'd like to once again propose the idea of how
to define and use an attribute.
I do not like the idea of:
@attr(identifier)
Why? Because what the hell did we create that "@" syntax for?
I though it was to avoid misinterpreting such things as normal
symbols, and avoid creating new keywords. Why should the
compiler be the only one able to use such symbols?
Another thing I don't like is some idea that only a certain
type of construct can be the identifier. An attribute should
have one requirement -- that it can be created/determined at
compile time.
Either this or the one that's the same just with structs is the
way to go. The original proposal by Walter is good, it's just a
little verbose.
I slightly prefer this function method over the struct method
because:
1) No need to generate a custom struct for everything. Plenty of
things are just a true or false, or a string. Saves a little bit
of TypeInfo generation.
2) The more important one: The possibility to eventually include
an alias template parameter. This allows things like looking up
whether the symbol with the attribute has other attributes
applied, or determining type. This allows things like
constraints, and can be a nice benefit.
On the topic of type vs storage, it is useful to be able to apply
attributes to a type, but this should /not/ change the type
itself. It must be transparent to the user what attributes a type
has unless they're actually accessing attributes.
