PEP 647: Incorporated feedback from Guido about terminology and type relationship between bool and TypeGuard #1765
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…w section to "Rejected Ideas" section about conditional application of the TypeGuard type.
…th "positional" when referring to argument) and clarified the type relationship between bool and TypeGuard.
gvanrossum
reviewed
Jan 16, 2021
pep-0647.rst
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| allows for a single type argument. It is meant to be used to annotate the | ||
| return type of a function or method. When it is used in other contexts, it | ||
| is treated as a ``bool``. | ||
| module. ``TypeGuard`` is a generic type that accepts a single type argument. |
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Suggested change
| module. ``TypeGuard`` is a generic type that accepts a single type argument. | |
| module. ``TypeGuard`` is a special form that accepts a single type argument. |
I propose to use "special form" instead of "generic type" since the functionality cannot be emulated using a user-defined generic type (same as for Union, Tuple etc.). I don't recall whether "special form" is a technical term defined in PEP 484, but we do use it in typing.py.
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PEP 484 doesn't define the term "special form", but the change sounds reasonable to me.
Not sure why github is repeating all of my prior commits when it creates the PR.
gvanrossum
approved these changes
Jan 16, 2021
gvanrossum
approved these changes
Jan 16, 2021
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