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x = tuple() # type: Tuple[()] Incompatible types in assignment #6283
Description
I understand this is a silly example, but figured I'd report it anyway.
I can't find a way (other than # type: ignore) to silence mypy for this line:
x = tuple() # type: Tuple[()]I found #4211 (which is how I got to Tuple[()]
mypy 0.660 errors with:
testing/resources/builtin_constructors.py:13: error: Incompatible types in assignment (expression has type "Tuple[<nothing>, ...]", variable has type "Tuple[]")
Activity
gvanrossum commentedon Feb 1, 2019
I don't think this is a bug. Every
tuplecall returns aTuple[T, ...]for someT, which is not the same as an empty tuple -- it is a tuple containing an arbitrary number ofTs.Unless you have an actual use case I don't think we should try to special-case calling
tuple()without arguments. (It's a class constructor, not a function, so you can't use standard overload syntax to say it returns an empty tuple when called without arguments.)ilevkivskyi commentedon Feb 1, 2019
At some point mypy might support honoring the return type of
__new__(), see #1020, so that we will be able to add an overload for empty tuple. We can probably keep this open as a low priority feature.[-]`x = tuple() # type: Tuple[()]` Incompatible types in assig nment[/-][+]`x = tuple() # type: Tuple[()]` Incompatible types in assignment[/+]JelleZijlstra commentedon Apr 3, 2022
x = () # type: Tuple[()]works fine. I don't think this is worth any special casing in mypy. We're discussing adding a special case in typeshed instead, though I'm skeptical about that too.