5bf5f3682a
## Summary This addresses @sharkdp's post-merge review in https://github.com/astral-sh/ruff/pull/18053#discussion_r2086190617 ## Test Plan `cargo test -p ty_python_semantic`
1.0 KiB
1.0 KiB
Narrowing using hasattr()
The builtin function hasattr() can be used to narrow nominal and structural types. This is
accomplished using an intersection with a synthesized protocol:
from typing import final
class Foo: ...
@final
class Bar: ...
def f(x: Foo):
if hasattr(x, "spam"):
reveal_type(x) # revealed: Foo & <Protocol with members 'spam'>
reveal_type(x.spam) # revealed: object
else:
reveal_type(x) # revealed: Foo & ~<Protocol with members 'spam'>
# TODO: should error and reveal `Unknown`
reveal_type(x.spam) # revealed: @Todo(map_with_boundness: intersections with negative contributions)
if hasattr(x, "not-an-identifier"):
reveal_type(x) # revealed: Foo
else:
reveal_type(x) # revealed: Foo
def y(x: Bar):
if hasattr(x, "spam"):
reveal_type(x) # revealed: Never
reveal_type(x.spam) # revealed: Never
else:
reveal_type(x) # revealed: Bar
# error: [unresolved-attribute]
reveal_type(x.spam) # revealed: Unknown