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PEP 696: Final round of changes before submitting to SC #3052

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Merged
JelleZijlstra merged 5 commits into from
Mar 12, 2023
Merged

PEP 696: Final round of changes before submitting to SC #3052

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506636c
Remove support for tuples as ParamSpec defaults
Gobot1234 Mar 11, 2023
08a5ed4
Update discussions to and post history
Gobot1234 Mar 11, 2023
0db657f
Add link to reference cpython impl
Gobot1234 Mar 11, 2023
c3befd9
Try fixing lint
Gobot1234 Mar 11, 2023
d334dd3
Try fixing the lint for the second time
Gobot1234 Mar 12, 2023
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19 changes: 12 additions & 7 deletions pep-0696.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,15 @@ PEP: 696
Title: Type defaults for TypeVarLikes
Author: James Hilton-Balfe <gobot1234yt@gmail.com>
Sponsor: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Discussions-To: typing-sig@python.org
Discussions-To: https://mail.python.org/archives/list/typing-sig@python.org/thread/7VWBZWXTCX6RAJO6GG67BAXUPFZ24NTC
Status: Draft
Type: Standards Track
Topic: Typing
Content-Type: text/x-rst
Created: 14-Jul-2022
Python-Version: 3.12
Post-History: `22-Mar-2022 <https://mail.python.org/archives/list/typing-sig@python.org/thread/7VWBZWXTCX6RAJO6GG67BAXUPFZ24NTC/>`__,
`08-Jan-2023 <https://discuss.python.org/t/pep-696-type-defaults-for-typevarlikes/22569/5/>`__,

@CAM-Gerlach CAM-Gerlach Mar 12, 2023

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The reason the linter (correctly) flagged this was due to it accidentally being a direct link to an arbitrary post down in the thread, instead of the thread itself. You were able to unintentionally bypass it due to the escape hatch of manually adding a trailing slash (which is not added by Discourse by default, like the post number is) recently implemented in #3005 in response to an author request in #3004 , which allows direct links to specific posts in special cases where the author specifically finds it necessary and intends to do so.

To actually fix this properly, the trailing post number, 5/, should be removed from this URL so it goes to the thread, not an arbitrary post within it.

@CAM-Gerlach CAM-Gerlach Mar 12, 2023

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I've opened #3053 to fix this.


Abstract
--------
Expand Down Expand Up @@ -143,7 +145,7 @@ future, this might be possible (see `Interaction with PEP
''''''''''''''''''''''

``ParamSpec`` defaults are defined using the same syntax as
``TypeVar`` \ s but use a ``list`` or ``tuple`` of types or an ellipsis
``TypeVar`` \ s but use a ``list`` of types or an ellipsis
literal "``...``" or another in-scope ``ParamSpec`` (see :ref:`696-scoping-rules`).

.. code-block:: py
Expand All @@ -152,9 +154,9 @@ literal "``...``" or another in-scope ``ParamSpec`` (see :ref:`696-scoping-rules

class Foo(Generic[DefaultP]): ...

reveal_type(Foo) # type is type[Foo[DefaultP = (str, int)]]
reveal_type(Foo()) # type is Foo[(str, int)]
reveal_type(Foo[(bool, bool)]()) # type is Foo[(bool, bool)]
reveal_type(Foo) # type is type[Foo[DefaultP = [str, int]]]
reveal_type(Foo()) # type is Foo[[str, int]]
reveal_type(Foo[[bool, bool]]()) # type is Foo[[bool, bool]]

``TypeVarTuple`` Defaults
'''''''''''''''''''''''''
Expand Down Expand Up @@ -399,6 +401,9 @@ The following changes would be required to both ``GenericAlias``\ es:
- ideally, logic to determine if subscription (like
``Generic[T, DefaultT]``) would be valid.

A reference implementation of the runtime changes can be found at
https://github.com/Gobot1234/cpython/tree/pep-696

A reference implementation of the type checker can be found at
https://github.com/Gobot1234/mypy/tree/TypeVar-defaults

Expand All @@ -418,14 +423,14 @@ using the "=" operator inside of the square brackets like so:
class Foo[T = str]: ...

# ParamSpecs
class Baz[**P = (int, str)]: ...
class Baz[**P = [int, str]]: ...

# TypeVarTuples
class Qux[*Ts = *tuple[int, bool]]: ...

# TypeAliases
type Foo[T, U = str] = Bar[T, U]
type Baz[**P = (int, str)] = Spam[**P]
type Baz[**P = [int, str]] = Spam[**P]
type Qux[*Ts = *tuple[str]] = Ham[*Ts]
type Rab[U, T = str] = Bar[T, U]

Expand Down