PEP 604 (Unions with pipe character) tracker

[srittau]

This issue is supposed to track when we can start to use the pipe character as union (PEP 604) in typeshed. Support is needed in released versions of:

• mypy (Support PEP 604 - union types as X | Y mypy#9610), mostly works, except (full list of related issues here):
  • Type aliases (3.10 union operator ( | ) doesn't work in subscripts when creating type aliases mypy#10901)
  • False-positive errors when using type[T] (or Type[T]) in a PEP 604 type alias mypy#12392
  • False-positive error when using Callable in a PEP 604 type alias mypy#12393
  • (🐞) False positive "error: Type application has too many types (1 expected)" on tuple when annotated as a type or in a TypeAlias with new union syntax (PEP 604) mypy#11098
  • False-positive error when using Callable in a PEP 604 type alias in a stub file with --python-version=3.9 mypy#14158
• pytype (Add support for PEP 604 (Union |) in stub files google/pytype#924)
• pyright (Implement PEP 604 microsoft/pyright#659)
• pyre
• PyCharm (PY-44974)

[srittau]

@rchen152 @mrkmndz Do pytype/pyre support PEP 604? If not, would you mind me creating a ticket in the respective projects that we can reference from here?

[sproshev]

Not yet supported by PyCharm https://youtrack.jetbrains.com/issue/PY-44974

[rchen152]

This is not yet supported by pytype. Opened google/pytype#785.

[JelleZijlstra]

Pyre already supports this. If I'm reading https://youtrack.jetbrains.com/issue/PY-44974 correctly, PyCharm already supports it enough for us to use it. That leaves only pytype.

[srittau]

This is the #1 feature I'm waiting for. This means we can basically replace any Union and Optional in Python 3 typeshed with a more readable alternative.

[srittau]

I think this is ready to be tested.

[srittau]

Reopening for now due to a fix for python/mypy#10901 not being released, yet. This means, we can't use this in type aliases.

[AlexWaygood]

I think mypy can now be ticked off, with the release of 0.920?

[JelleZijlstra]

We should be done now :)

[srittau]

We should replace remaining uses of Union and Optional.

[AlexWaygood]

I'm reopening this to track the remaining mypy bugs.

[Avasam]

I'm reopening this to track the remaining mypy bugs.

What is/are the bug(s) left? Is it listed on mypy side?

[AlexWaygood]

I'm reopening this to track the remaining mypy bugs.

What is/are the bug(s) left? Is it listed on mypy side?

None left now (to my knowledge)! All the significant bugs are now fixed on mypy master -- we're just waiting on a new release of mypy that includes the fixes. Then we can close this out!