unified and extensible annotations

[waldmann@…]

We have several annotations in current Haskell: deriving,  pragmas {-# #-}, {-! !-} ( DrIFT),  haddock... These are ad-hoc, and not extensible by the programmer.

There are better ways:

• C-sharp has  custom attributes.
• Java (1.5) has  annotations.

For me the important features are

• An annotation is allowed basically at any declaration,
• and programmers can define their own annotations,
• and annotations can also have values.
• Also, they have a retention policy saying whether they should be visible at compile time or at run time, where compile time is for tools/preprocessors, and visibility at run time is helpful for reflection. (Would need some support from Data.Generics or thereabouts.)

I have brought this  proposal up on the mailing list and there was one  response.