[Python-3000] Type annotations: annotating generators

[Paul Boddie]

Guido van Rossum wrote:
>
> I'm not convinced that we need all this for the likely intended use,
> since static type checking isn't really high on the agenda anyway.

I know I'll get into trouble for quoting this out of context, and I accept 
that there's a difference between static typing and writing declarations that 
look like static type declarations but which operate at run-time. However, I 
keep wondering whether we're missing out on something by adopting a type 
description language that will either prove to be inadequately expressive or 
evolve to something on the level of a full programming language in its own 
right.

What's the general opinion on systems which attempt to infer and predict 
inappropriate type usage? (Which I'm guessing is the main motivation here, 
rather than performance, which if I recall correctly, was downplayed in the 
context of "optional" type declarations.) By "predict", I mean something that 
operates before run-time; not something which tells you 100ns before an 
exception is raised. Couldn't such systems be a better aid to program 
reliability? Would "optional" type declarations be relevant to the operation 
of such systems?

Paul