variance for parameter specification and type variable tuples#1771
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Diff from mypy_primer, showing the effect of this PR on open source code: core (https://github.com/home-assistant/core)
- Type parameter "_P@HassJob" is invariant, but "(_: datetime | None = None)" is not the same as "(datetime)"
+ .../projects/core/homeassistant/components/google_assistant/report_state.py:196:37 - warning: Argument type is partially unknown
+ Argument corresponds to parameter "action" in function "async_call_later"
+ Argument type is "HassJob[(_now: Unknown), Coroutine[Any, Any, None] | None]" (reportUnknownArgumentType)
- Type parameter "_P@HassJob" is invariant, but "(_: datetime | None = None)" is not the same as "(datetime)"
- Type parameter "_P@HassJob" is invariant, but "(_now: datetime | None = None)" is not the same as "(datetime)"
- Type parameter "_P@HassJob" is invariant, but "(_: Exception | None = None)" is not the same as "(datetime)"
+ Type parameter "_P@HassJob" is covariant, but "(_: Exception | None = None)" is not a subtype of "(datetime)"
+ Type "(_: Exception | None = None)" is not assignable to type "(datetime)"
+ Parameter 1: type "datetime" is incompatible with type "Exception | None"
- .../projects/core/homeassistant/components/wemo/__init__.py:289:17 - error: Argument of type "HassJob[(datetime), None]" cannot be assigned to parameter "action" of type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))" in function "async_call_later"
+ .../projects/core/homeassistant/components/wemo/__init__.py:289:17 - error: Argument of type "HassJob[(event_time: datetime), None] | HassJob[(datetime), None]" cannot be assigned to parameter "action" of type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))" in function "async_call_later"
+ Type "HassJob[(event_time: datetime), None] | HassJob[(datetime), None]" is not assignable to type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))"
- Type "HassJob[(datetime), None]" is not assignable to type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))"
+ Type "HassJob[(datetime), None]" is not assignable to type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))"
- "HassJob[(datetime), None]" is not assignable to "HassJob[(datetime), Coroutine[Any, Any, None] | None]"
+ "HassJob[(datetime), None]" is not assignable to "HassJob[(datetime), Coroutine[Any, Any, None] | None]"
- Type parameter "_R_co@HassJob" is invariant, but "None" is not the same as "Coroutine[Any, Any, None] | None"
+ Type parameter "_R_co@HassJob" is invariant, but "None" is not the same as "Coroutine[Any, Any, None] | None"
- Type "HassJob[(datetime), None]" is not assignable to type "(datetime) -> (Coroutine[Any, Any, None] | None)" (reportArgumentType)
+ Type "HassJob[(datetime), None]" is not assignable to type "(datetime) -> (Coroutine[Any, Any, None] | None)" (reportArgumentType)
+ .../projects/core/homeassistant/components/yeelight/scanner.py:186:28 - warning: Argument type is partially unknown
+ Argument corresponds to parameter "action" in function "async_call_later"
+ Argument type is "HassJob[(*_: Unknown), Coroutine[Any, Any, None] | None]" (reportUnknownArgumentType)
- .../projects/core/homeassistant/helpers/event.py:1819:13 - error: Argument of type "HassJob[(datetime), None]" cannot be assigned to parameter "action" of type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))" in function "async_track_point_in_utc_time"
+ .../projects/core/homeassistant/helpers/event.py:1819:13 - error: Argument of type "HassJob[(_: datetime), None]" cannot be assigned to parameter "action" of type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))" in function "async_track_point_in_utc_time"
- Type "HassJob[(datetime), None]" is not assignable to type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))"
+ Type "HassJob[(_: datetime), None]" is not assignable to type "HassJob[(datetime), Coroutine[Any, Any, None] | None] | ((datetime) -> (Coroutine[Any, Any, None] | None))"
- "HassJob[(datetime), None]" is not assignable to "HassJob[(datetime), Coroutine[Any, Any, None] | None]"
+ "HassJob[(_: datetime), None]" is not assignable to "HassJob[(datetime), Coroutine[Any, Any, None] | None]"
- Type "HassJob[(datetime), None]" is not assignable to type "(datetime) -> (Coroutine[Any, Any, None] | None)" (reportArgumentType)
+ Type "HassJob[(_: datetime), None]" is not assignable to type "(datetime) -> (Coroutine[Any, Any, None] | None)" (reportArgumentType)
- 33917 errors, 397968 warnings, 0 notes
+ 33917 errors, 397970 warnings, 0 notes
|
Owner
|
what issue is this fixing? |
Collaborator
Author
the issue that tvt/param spec variance isn't supported |
DetachHead
reviewed
Apr 24, 2026
Comment on lines
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| if (paramName === 'covariant') { | ||
| if (argList[i].valueExpression && getBooleanValue(argList[i].valueExpression!)) { | ||
| if ( | ||
| paramSpec.shared.declaredVariance === Variance.Contravariant || | ||
| paramSpec.shared.declaredVariance === Variance.Auto | ||
| ) { | ||
| addDiagnostic( | ||
| DiagnosticRule.reportGeneralTypeIssues, | ||
| LocMessage.typeVarVariance(), | ||
| argList[i].valueExpression! | ||
| ); | ||
| } else { | ||
| paramSpec.shared.declaredVariance = Variance.Covariant; | ||
| } | ||
| } | ||
| } else if (paramName === 'contravariant') { | ||
| if (argList[i].valueExpression && getBooleanValue(argList[i].valueExpression!)) { | ||
| if ( | ||
| paramSpec.shared.declaredVariance === Variance.Covariant || | ||
| paramSpec.shared.declaredVariance === Variance.Auto | ||
| ) { | ||
| addDiagnostic( | ||
| DiagnosticRule.reportGeneralTypeIssues, | ||
| LocMessage.typeVarVariance(), | ||
| argList[i].valueExpression! | ||
| ); | ||
| } else { | ||
| paramSpec.shared.declaredVariance = Variance.Contravariant; | ||
| } | ||
| } | ||
| } else if (paramName === 'infer_variance') { | ||
| if (argList[i].valueExpression && getBooleanValue(argList[i].valueExpression!)) { | ||
| if ( | ||
| paramSpec.shared.declaredVariance === Variance.Covariant || | ||
| paramSpec.shared.declaredVariance === Variance.Contravariant | ||
| ) { | ||
| addDiagnostic( | ||
| DiagnosticRule.reportGeneralTypeIssues, | ||
| LocMessage.typeVarVariance(), | ||
| argList[i].valueExpression! | ||
| ); | ||
| } else { | ||
| paramSpec.shared.declaredVariance = Variance.Auto; | ||
| } | ||
| } | ||
| } else if (paramName === 'default') { |
Comment on lines
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| class ShouldBeContravariant1[**OutP]: | ||
| def f(self) -> Callable[OutP, None]: ... |
Owner
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should also have a test for the most common usage:
class ShouldBeContravariant2[**OutP]:
def f(self, *args: P.args, **kwargs: P.kwargs): ...
Comment on lines
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| P_co = ParamSpec("P_co", covariant=True) | ||
| P_contra = ParamSpec("P_contra", contravariant=True) | ||
| P_infer = ParamSpec("P_infer", infer_variance=True) |
Owner
There was a problem hiding this comment.
is it just to make sure theres no error on the arguments? if so should add a comment
Comment on lines
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| Ts_co = TypeVarTuple("Ts_co", covariant=True) | ||
| Ts_contra = TypeVarTuple("Ts_contra", contravariant=True) | ||
| Ts_infer = TypeVarTuple("Ts_infer", infer_variance=True) |
Owner
There was a problem hiding this comment.
comment saying why these unused typevar variables are here
Owner
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honestly i have never encountered a single situation where a typevartuple has been useful. could you please provide a realistic example of when anyone would ever use one, and how it could benefit from supporting variance? otherwise i dont see why we should even bother to add variance support to them or touch them in any way.
it sounds like it was just scope creeped in your discourse thread about ParamSpecs for no reason
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poc for python/typing#2215