Nonlocal float | None variable asserted to not be None still has None in its type #2649
Description
Summary
When a nonlocal variable of inferred type float | None is known (by control flow) not to be an int and is known (by assertion) not to be None, ty detects its type as int | float | None, ignoring the assertion. Example:
$ cat >bug.py <<'# EOF'
def _(maybe_float: float | None, certain_int: int, flag: bool) -> None:
if isinstance(maybe_float, int):
return
x = maybe_float
def _() -> None:
nonlocal x
if flag:
x = certain_int
assert x is not None
+x
# EOF
$ ty check bug.py
error[unsupported-operator]: Unary operator `+` is not supported for object of type `int | float | None`
--> bug.py:10:9
|
8 | x = certain_int
9 | assert x is not None
10 | +x
| ^^
|
info: rule `unsupported-operator` is enabled by default
Found 1 diagnosticVersion
ty 0.0.14 (16597f5 2026-01-26)