[Python-ideas] Possible enhancement to typing

[Steve Barnes]

The discussions on moving typing to a standalone library prompted me to 
take a look at the documentation for typing which in turn lead to an 
idea that should be reasonably simple to implement but greatly add value 
to typing for some applications.

If a group of iterators were to be added to the typing module it would 
be reasonably simple to automatically add and assert to any decorated 
modules to ensure that such modules were always called with the 
documented types.

I am thinking of decorators such as:

  - @typing.assert_params_mismatch - this would provide a wrapper that 
had auto-generated asserts that all the parameters were of designated types.
  - @typing.debug_assert_params_mismatch - this would provide a wrapper 
that had auto-generated asserts that all the parameters were of 
designated types only if a DEBUG environmental variable was set or similar.
  - @typing.warn_params_mismatch - this would provide a wrapper that had 
auto-generated warnings issued to stderr if any of the parameters were 
of not of the designated types.
  - @typing.coerce_params - this would add a wrapper to attempt to 
convert any mismatched parameters to the specified type(s).

I also think that this might increase the uptake of typing by giving 
some clear benefits outside of documentation and static type checking.

Pushing this out for comment before considering a more formal, (PEP), 
proposal.
-- 
Steve (Gadget) Barnes
Any opinions in this message are my personal opinions and do not reflect 
those of my employer.

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