RFC: Typecheck expr.py - Githubissues

cgravill commented 3 years ago

AB#19879 specifically AB#19886

Some good changes:

Tweaked a few types, implemenation has shifted
Added some redundant asserts for mypy. mypy can't infer types from is_derivation

A change I'm not totally happy with:

Avoided reuse of _ with singledispatch - mypy doesn't understand it

The overall situation is that mypy has numerous limitations with functools.singledispatch see https://github.com/python/mypy/issues/8356

Suffixing the type onto the dummy method isn't the listed style for singledispatch, but seems common if you want to process your code by a type checker which is what I've done here. Tests and type checker pass, though I think it means the type checkers believe most of the implementations are dead code.

Alternatives:

use comment disables
rewrite singledispatch with @overload and our own dispatch on the argument

cgravill commented 3 years ago

Long term (3.10) alternative https://www.python.org/dev/peps/pep-0636/#adding-a-ui-matching-objects

cgravill commented 3 years ago

Any thoughts on these @acl33 particularly the singledispatch?

microsoft / knossos-ksc

RFC: Typecheck expr.py #902