DIP6: Attributes

[Leandro Lucarella]

Ary Borenszweig, el  1 de agosto a las 16:29 me escribiste:
> http://www.prowiki.org/wiki4d/wiki.cgi?LanguageDevel/DIPs/DIP6

I really think that D should support some kind of annotations. I think
it's a good idea to add them in stages. I could add that in the first
stage, old-style attributes/whatever (override, deprecated, etc.) should
be accepted too (i.e. without the leading @). Then people complaining
about backward compatibility can be happy (me included; hey! I'll add them
to D1.1 too! ;). New syntax can make use of annotations though (hello
properties!).

I think annotations in D can reach their peak of utility when AST macros
get implemented. I think it would be great being able to "register"
annotation handlers to the compiler to do arbitrary transformations to the
code. You could even move a big part of the compiler implementation to
library code using annotations and AST macros. But this have to come in
other stages for sure.

I think changing the FE to allow annotation syntax wouldn't be very hard
(I'm guessing, I never hacked the DMDFE myself). Maybe someone who played
with the FE can make a quick patch as a proof of concepts, even if the
implementation ignores the annotations completely for now it can be a good
start.

I think the "Other thoughts" section should be official part of the
proposal if there is any intention to move most of the current attribute
keywords to annotations.

About the version(X) {} else {}, first, version(!X) could be supported as
an ugly hack =P. A more generic approach could be to support annotations
returns. Annotations could return void (in which case the else statement
is a *semantic* error) or bool (in which case the else statement is
supported). The problem with this is that statements should be target for
annotations too, so one can do:

@deprecated
void foo()
{
	@version(Foo) writeln("foo");
}

Maybe this one should be delayed for a second stage of annotations =)

-- 
Leandro Lucarella (luca) | Blog colectivo: http://www.mazziblog.com.ar/blog/
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