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gh-104050: Argument clinic: improve typing around adding C converters#107209

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AlexWaygood merged 1 commit intopython:mainfromAlexWaygood:add-converter-typing

Jul 25, 2023

Merged

gh-104050: Argument clinic: improve typing around adding C converters#107209

AlexWaygood merged 1 commit intopython:mainfromAlexWaygood:add-converter-typing

Jul 25, 2023

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AlexWaygood commentedJul 24, 2023•
edited by bedevere-bot
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Some of this looks alittle complicated at first glance, but it's hopefully not too hard to grok

Issue:Add type annotations to clinic.py #104050

Argument clinic: improve typing around adding C converters

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AlexWaygood added the skip news label

Jul 24, 2023

AlexWaygood requested a review fromerlend-aasland as acode owner

July 24, 2023 22:41

bedevere-bot added the awaiting core review label

Jul 24, 2023

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Jul 24, 2023

Add type annotations to clinic.py#104050

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AlexWaygood commented

Jul 24, 2023

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Tools/clinic/clinic.py

Comment on lines +2651 to +2656

		CConverterClassT=TypeVar("CConverterClassT",bound=type["CConverter"])

		defadd_c_converter(
		f:type[CConverter],
		f:CConverterClassT,
		name:str\|None=None
		)->type[CConverter]:
		)->CConverterClassT:

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AlexWaygoodJul 24, 2023•
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By using aTypeVar here (and with the other functions in this PR), we can make the annotation much more expressive.

The annotation currently says "you put in an objectf that's some subtype oftype[CConverter], and you get out an object that's some subtype oftype[CConverter].

The new annotation, by contrast, says, "you put in an objectf, and you get out an object that has the same type as whatever the type off is,as long as the type off is a subtype oftype[CConverter].

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As an example, with the following snippet:

x=add_c_converter(bool_converter)

Mypy would have inferred the type ofx to betype[CConverter] with the current annotation. But with the new annotation, mypy should be able to infer that the type ofx isbool_converter.