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## Summary This PR closes #16248. If the return type of the function isn't assignable to the one specified, an `invalid-return-type` error occurs. I thought it would be better to report this as a different kind of error than the `invalid-assignment` error, so I defined this as a new error. ## Test Plan All type inconsistencies in the test cases have been replaced with appropriate ones. --------- Co-authored-by: Carl Meyer <carl@astral.sh>
1.2 KiB
1.2 KiB
Narrowing in while loops
We only make sure that narrowing works for while loops in general, we do not exhaustively test all
narrowing forms here, as they are covered in other tests.
Note how type narrowing works subtly different from if ... else, because the negated constraint
is retained after the loop.
Basic while loop
def next_item() -> int | None:
return 1
x = next_item()
while x is not None:
reveal_type(x) # revealed: int
x = next_item()
reveal_type(x) # revealed: None
while loop with else
def next_item() -> int | None:
return 1
x = next_item()
while x is not None:
reveal_type(x) # revealed: int
x = next_item()
else:
reveal_type(x) # revealed: None
reveal_type(x) # revealed: None
Nested while loops
from typing import Literal
def next_item() -> Literal[1, 2, 3]:
raise NotImplementedError
x = next_item()
while x != 1:
reveal_type(x) # revealed: Literal[2, 3]
while x != 2:
# TODO: this should be Literal[1, 3]; Literal[3] is only correct
# in the first loop iteration
reveal_type(x) # revealed: Literal[3]
x = next_item()
x = next_item()