Anubis

As standard library and functions or types that compose it aren't yet perfectly well designed, and name changes can be frequent, adding a keyword 'obsolete' (or any thing like this) could be a great help.

This keyword does nothing else than producing a warning during compile time, just to remember to not use this function.

A variation of this could be the keyword : obsolete(new_function)

With this, the compiler can produce a very useful warning, telling which function to use instead of this one.

The keyword could be inserted into function or type definition like this :

public define obsolete(new_function_name) [[ReturnType]]
  old_function_name
  (
    ...
  ) =
  <function body>.

Or maybe better (as we can suppose that 'obsolete' functions or type are always public ones):

obsolete(new_function_name) define [[ReturnType]]
  old_function_name
  (
    ...
  ) =
  <function body>.

which made automatically this function public but obsolete.

Private function can always be easily renamed, so there is no need to mark them as obsolete.