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TypeVarTuple example has unused TypeVar #95337

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adriangb opened this issue Jul 27, 2022 · 1 comment
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TypeVarTuple example has unused TypeVar #95337

adriangb opened this issue Jul 27, 2022 · 1 comment
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docs Documentation in the Doc dir topic-typing

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@adriangb
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From the docs:

Ts = TypeVarTuple('Ts')

def remove_first_element(tup: tuple[Any, *Ts]) -> tuple[*Ts]:
    return tup[1:]

# Ts is bound to ()
# Return value is (), which has type tuple[()]
remove_first_element(tup=(1,))

# Ts is bound to (str,)
# Return value is ('spam',), which has type tuple[str]
remove_first_element(tup=(1, 'spam'))

# Ts is bound to (str, float)
# Return value is ('spam', 3.0), which has type tuple[str, float]
remove_first_element(tup=(1, 'spam', 3.0))

Notice that "T" is only used once in the function signature, which Pylance will highlight as an error.
In this case, Any is just as meaningful as T (and I would argue semantically better, we don't care what the first element is)
All of the examples (checked with reveal_type) are still valid.
@adriangb adriangb added the docs Documentation in the Doc dir label Jul 27, 2022
@bedevere-bot bedevere-bot mentioned this issue Jul 27, 2022
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@bedevere-bot bedevere-bot mentioned this issue Aug 30, 2022
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miss-islington pushed a commit to miss-islington/cpython that referenced this issue Aug 30, 2022
@adriangb @miss-islington
pythongh-95337: update TypeVarTuple example (pythonGH-95338)
635751c 
Co-authored-by: Alex Waygood <[email protected]>
(cherry picked from commit 07f12b5)

Co-authored-by: Adrian Garcia Badaracco <[email protected]>
JelleZijlstra pushed a commit that referenced this issue Aug 30, 2022
@adriangb @AlexWaygood
gh-95337: update TypeVarTuple example (#95338)
07f12b5 
Co-authored-by: Alex Waygood <[email protected]>
miss-islington added a commit that referenced this issue Aug 30, 2022
@miss-islington @adriangb
gh-95337: update TypeVarTuple example (GH-95338)
d00a9e0 
Co-authored-by: Alex Waygood <[email protected]>
(cherry picked from commit 07f12b5)

Co-authored-by: Adrian Garcia Badaracco <[email protected]>
@hauntsaninja
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Looks like this has been completed

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@adriangb @hauntsaninja @AlexWaygood