PEP 613 (Explicit Type Aliases) tracker

[srittau]

This issue is supposed to track when we can start to use explicit type aliases (PEP 613) in typeshed. Support is needed in released versions of:

• mypy (Support PEP 613 mypy#9404)
  • Explicit type aliases fail in typeshed mypy#12422
• pytype (Support PEP 613: Explicit Type Aliases google/pytype#787)
  • Problems with explicit type aliases in typeshed google/pytype#1159
• pyright (Implement PEP 613 microsoft/pyright#655)
• pyre
• PyCharm PY-42334

[srittau]

@rchen152 I am sorry for the mention spam, but does pytype support PEP 613? If not, would you mind me creating a ticket that we can reference from here?

[sproshev]

Supported since PyCharm 2020.3 https://youtrack.jetbrains.com/issue/PY-42334

[rchen152]

pytype doesn't support this yet. Opened google/pytype#787.

[srittau]

I used this simple script to test this feature.

from typing_extensions import TypeAlias

Alias1 = str
Alias2: TypeAlias = str

def foo() -> Alias1: pass
def bar() -> Alias2: pass

reveal_type(foo)
reveal_type(bar)

[srittau]

mypy 0.930 now supports this.

[rchen152]

pytype-2022.03.21 supports explicit type aliases.

[AlexWaygood]

Seems like there's nothing left to do here :)

[srittau]

Reopening as mypy still seems to have problems. #7534

[AlexWaygood]

@rchen152, #7534 also has several pytype errors, but they all look like valid type aliases to me — any idea what the problem is? :)

[rchen152]

Whoops, that's embarrassing XD
It looks almost like the type aliases aren't being stored at all - I'll investigate.

[srittau]

mypy and pytype are now fixed. 🎉

[laundmo]

Does the closing of this issue mean that TypeAlias can now be used in TypeShed?

if yes, this should probably be edited:

typeshed/CONTRIBUTING.md

Lines 241 to 242 in be64b01

	- [PEP 613](https://www.python.org/dev/peps/pep-0613/) (TypeAlias):
	see [#4913](https://github.com/python/typeshed/issues/4913)

[AlexWaygood]

Does the closing of this issue mean that TypeAlias can now be used in TypeShed?

if yes, this should probably be edited:

typeshed/CONTRIBUTING.md

Lines 241 to 242 in be64b01

	- [PEP 613](https://www.python.org/dev/peps/pep-0613/) (TypeAlias):
	see [#4913](https://github.com/python/typeshed/issues/4913)

It does — and yes, CONTRIBUTING does need to be edited :) I think the guidance on ParamSpec is also slightly out of date.

PR welcome, if you'd like to help out!

[kkirsche]

Does the closing of this issue mean that TypeAlias can now be used in TypeShed?
if yes, this should probably be edited:

typeshed/CONTRIBUTING.md

Lines 241 to 242 in be64b01

	- [PEP 613](https://www.python.org/dev/peps/pep-0613/) (TypeAlias):
	see [#4913](https://github.com/python/typeshed/issues/4913)

It does — and yes, CONTRIBUTING does need to be edited :) I think the guidance on ParamSpec is also slightly out of date.

PR welcome, if you'd like to help out!

#8397 created to address this