[red-knot] Detect unreachable attributes assignments #15967
Description
This is probably not a high-priority feature, but it would be great if we could detect attribute assignments in unreachable code sections, and eliminate them from the set of possible answers:
class C:
def __init__(self) -> None:
if True:
self.x = 1
else:
self.x = "a"
return
self.y = "unreachable"
reveal_type(C().x) # should be `Unknown | Literal[1]` (i.e. not include `Literal["a"]`)
# Should be an error:
C().yNote that we have one existing test for this here:
ruff/crates/red_knot_python_semantic/resources/mdtest/attributes.md
Lines 434 to 448 in 16f2a93