[Python-Dev] PEP 484 -- proposal to allow @overload in non-stub files

[Guido van Rossum]

Well the whole point is not to have to figure out how to implement that
right now.

On Wed, Oct 21, 2015 at 6:45 PM, Random832 <random832 at fastmail.com> wrote:

> Guido van Rossum <guido at python.org> writes:
> > The proposal is to allow this to be written as follows in
> > implementation (non-stub) modules:
> >
> > class Foo(Generic[T]):
> > @overload
> > def __getitem__(self, i: int) -> T: ...
> > @overload
> > def __getitem__(self, s: slice) -> Foo[T]: ...
> > def __getitem__(self, x):
> > <actual implementation goes here>
> >
> > The actual implementation must be last, so at run time it will
> > override the definition.
>
> How about this to allow overloads to have actual implementations?
>
> @overloaded
> def __getitem__(self, x):
>     <default implementation, if none of the overloads matched>
>
> @overloaded returns a function which will check the types against the
> overloads (or anyway any overloads that have actual implementations),
> call them returning the result if applicable, otherwise call the
> original function.
>
> Some magic with help() would improve usability, too - it could print all
> the overloads and their docstrings.  Maybe even @overload('__getitem__')
> def __get_int(self, i: int), to make it so order doesn't matter.
>
> That just leaves the question of how's this all gonna work with
> subclasses.
>
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-- 
--Guido van Rossum (python.org/~guido)
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