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Merged
merged 5 commits into from
May 17, 2023
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typing: Use PEP 695 syntax in typing.py #104553

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e1ff413
typing: Use PEP 695 syntax in typing.py
JelleZijlstra May 16, 2023
16b0978
Use an alias, remove unnecessary _co suffix
JelleZijlstra May 16, 2023
655d6ac
Merge branch 'main' into use695
AlexWaygood May 16, 2023
754dda0
Better type for dataclass_transform
JelleZijlstra May 17, 2023
302f071
Merge remote-tracking branch 'upstream/main' into use695
JelleZijlstra May 17, 2023
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23 changes: 12 additions & 11 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2471,8 +2471,9 @@ class Other(Leaf): # Error reported by type checker
return f


# Some unconstrained type variables. These are used by the container types.
# (These are not for export.)
# Some unconstrained type variables. These were initially used by the container types.
# They were never meant for export and are now unused, but we keep them around to
# avoid breaking compatibility with users who import them.
T = TypeVar('T') # Any type.
KT = TypeVar('KT') # Key type.
VT = TypeVar('VT') # Value type.
Expand Down Expand Up @@ -2577,8 +2578,6 @@ def new_user(user_class: Type[U]) -> U:
At this point the type checker knows that joe has type BasicUser.
"""

# Internal type variable for callables. Not for export.
F = TypeVar("F", bound=Callable[..., Any])
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@JelleZijlstra JelleZijlstra May 16, 2023

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This one was added as part of implementing override earlier in 3.12, so there's no need to keep it around for compatibility.


@runtime_checkable
class SupportsInt(Protocol):
Expand Down Expand Up @@ -2631,22 +2630,22 @@ def __index__(self) -> int:


@runtime_checkable
class SupportsAbs(Protocol[T_co]):
class SupportsAbs[T](Protocol):
"""An ABC with one abstract method __abs__ that is covariant in its return type."""
__slots__ = ()

@abstractmethod
def __abs__(self) -> T_co:
def __abs__(self) -> T:
pass


@runtime_checkable
class SupportsRound(Protocol[T_co]):
class SupportsRound[T](Protocol):
"""An ABC with one abstract method __round__ that is covariant in its return type."""
__slots__ = ()

@abstractmethod
def __round__(self, ndigits: int = 0) -> T_co:
def __round__(self, ndigits: int = 0) -> T:
pass


Expand Down Expand Up @@ -3183,7 +3182,7 @@ class re(metaclass=_DeprecatedType):
sys.modules[re.__name__] = re


def reveal_type(obj: T, /) -> T:
def reveal_type[T](obj: T, /) -> T:
"""Reveal the inferred type of a variable.

When a static type checker encounters a call to ``reveal_type()``,
Expand All @@ -3203,7 +3202,7 @@ def reveal_type(obj: T, /) -> T:
return obj


def dataclass_transform(
def dataclass_transform[T](
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@AlexWaygood AlexWaygood May 16, 2023 •
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This feels slightly strange to me, as (to me) it implies that dataclass_transform is a function generic around the type variable T. But that's not really true; it's a non-generic function that returns an identity function. I skimmed PEP 695, and it doesn't seem to mention how such cases should be handled.

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@gvanrossum gvanrossum May 16, 2023

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IIRC we did think about this and decided that this is indeed how such cases should be spelled (since Callable doesn't have a way yet to spell "generic").

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@hauntsaninja hauntsaninja May 16, 2023

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I think we shouldn't do this since it confuses scoping and much of the point of PEP 695 is to clarify scoping. We can use a callback protocol to spell this.

I'd brought this up somewhere before PEP 695 was accepted, but didn't get much of a response. Presumably since it's not the most common thing and I think e.g. pyre might not even support -> Callable[[T], T]

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@JelleZijlstra JelleZijlstra May 17, 2023

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Changed to a callback protocol

*,
eq_default: bool = True,
order_default: bool = False,
Expand Down Expand Up @@ -3288,8 +3287,10 @@ def decorator(cls_or_fn):
return decorator


type _Func = Callable[..., Any]

def override(method: F, /) -> F:

def override[F: _Func](method: F, /) -> F:
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@AlexWaygood AlexWaygood May 16, 2023 •
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Yeah, the alias makes that so much more readable, in my opinion. Thanks! Good call @gvanrossum.

"""Indicate that a method is intended to override a method in a base class.

Usage:
Expand Down