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Union of unpacked TypeVarTuple should evaluate to Never for empty TypeVarTuple #4739

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erictraut opened this issue Mar 6, 2023 · 1 comment
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Union of unpacked TypeVarTuple should evaluate to Never for empty TypeVarTuple #4739

erictraut opened this issue Mar 6, 2023 · 1 comment
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addressed in next version Issue is fixed and will appear in next published version bug Something isn't working

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@erictraut
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erictraut commented Mar 6, 2023 •
edited
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from typing import Generic, TypeVarTuple, Union

Ts = TypeVarTuple("Ts")

class ClassA(Generic[*Ts]):
    def __init__(self, *args: *Ts):
        ...

    def foo(self) -> Union[*Ts]:
        ...

x = ClassA()
y = x.foo()
reveal_type(y, expected_text="Never")
@erictraut erictraut added bug Something isn't working addressed in next version Issue is fixed and will appear in next published version labels Mar 6, 2023
erictraut pushed a commit that referenced this issue Mar 6, 2023
@msfterictraut
Fixed bug that resulted in the incorrect type evaluation for a functi…
5180be8 
…on or method that returns `Union[*Ts]` where `Ts` is a TypeVarTuple bound to `*tuple[()]`. This addresses #4739.
@erictraut
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This is addressed in pyright 1.1.297, which I just published. It will also be included in a future release of pylance.

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