[Python-ideas] Add an option that allow check Type Hints in runtime

[Chris Angelico]

On Fri, Jul 8, 2016 at 7:02 PM, Chris Angelico <rosuav at gmail.com> wrote:
> Now your decorator does nothing, and there is literally ZERO run-time
> cost (the only cost is a single cheap check when the function is
> defined, which usually means on module import), closures aside. That
> wouldn't be possible with a core interpreter change...

I really shouldn't say impossible. Literally the moment I clicked
Send, I thought of a way it could be done with minimal run-time cost:
just create a completely separate opcode for "type-checked call". I
don't think that would materially slow down the regular call
operation. As a bonus, any functions that don't have annotations could
use the normal call opcode, so they wouldn't be slowed down.

But the main point is, this would all entail additional complexity
inside CPython, where the decorator method keeps the complexity in
your application - and doesn't need nearly as much of it. The one
advantage that CPython has is, as mentioned, the matching of arguments
to parameters; maybe that could be provided in functools somewhere?

ChrisA