Match statement + exception on default case doesn't narrow properly #1384
Description
Summary
Example function:
def do_something(interval: str, number_of_periods: int | None = None) -> None:
match interval:
case "monthly":
if number_of_periods is None:
number_of_periods = 12
# do other stuff here
case "daily":
if number_of_periods is None:
number_of_periods = 30
case "hourly":
if number_of_periods is None:
number_of_periods = 24
case _:
raise ValueError(f"Unknown interval {interval}")
if number_of_periods < 0 or number_of_periods > 50:
raise ValueError(f"Invalid number of periods {number_of_periods}")
# now fetch some data or something, IDKRunning ty check on this function returns two errors because ty does not catch that number_of_periods has to be an int at that point (each branch of the match either coerces that variable into an int or fails out with an exception).
error[unsupported-operator]: Operator `<` is not supported for types `None` and `int`, in comparing `int | None` with `Literal[0]`
--> ty_fail.py:15:8
|
13 | case _:
14 | raise ValueError(f"Unknown interval {interval}")
15 | if number_of_periods < 0 or number_of_periods > 50:
| ^^^^^^^^^^^^^^^^^^^^^
16 | raise ValueError(f"Invalid number of periods {number_of_periods}")
17 | # now fetch some data or something, IDK
|
info: rule `unsupported-operator` is enabled by default
error[unsupported-operator]: Operator `>` is not supported for types `None` and `int`, in comparing `int | None` with `Literal[50]`
--> ty_fail.py:15:33
|
13 | case _:
14 | raise ValueError(f"Unknown interval {interval}")
15 | if number_of_periods < 0 or number_of_periods > 50:
| ^^^^^^^^^^^^^^^^^^^^^^
16 | raise ValueError(f"Invalid number of periods {number_of_periods}")
17 | # now fetch some data or something, IDK
|
info: rule `unsupported-operator` is enabled by default
This may be related to #1349 but I'm not 100% sure.
Version
ty 0.0.1-alpha.23