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

[Talin]

Collin Winter wrote:
>    There is no worry that these libraries will assign semantics at
>    random, or that a variety of libraries will appear, each with varying
>    semantics and interpretations of what, say, a tuple of strings
>    means. The difficulty inherent in writing annotation interpreting
>    libraries will keep their number low and their authorship in the
>    hands of people who, frankly, know what they're doing.

I find this assumption extremely dubious.

> In pseudo-grammar, parameters now look like
> ``identifier [: expression] [= expression]``.  That is, type
> annotations always precede a parameter's default value and both type
> annotations and default values are optional.  Just like how equal
> signs are used to indicate a default value, colons are used to mark
> annotations.  All annotation expressions are evaluated at the time
> the function is compiled.

Only one annotation per parameter? What if I want to specify both a 
docstring *and* a type constraint?

-- Talin