[Python-3000] Draft pre-PEP: function annotations

[Stefan Behnel]

Hi,

Collin Winter wrote:
>         def compile(source: "something compilable",
>                     filename: "where the compilable thing comes from",
>                     mode: "is this a single statement or a suite?"):
>             ...
> 
>         def sum(*vargs: Number) -> Number:
>             ...

Admittedly, I'm not so much in the "Spring stew" discussion, but I'm not a big
fan of cluttering up my function signature with "make them short to make them
fit" comments.

What would be wrong in adding a standard decorator for this purpose? Something
like:

   @type_annotate("This is a filename passed as string", filename = str)
   @type_annotate(source = str)
   def compile(source, filename, mode):
      ...

or, more explicitly:

   @arg_docstring(filename = "This is a filename passed as string")
   @arg_type(filename = str)
   @arg_type(source = str)
   def compile(source, filename, mode):
      ...

Stefan