`_x.a = 1`, `_x.a += 2`, `_x[0] = 3` and `_x.a: T = v` only visited the assigned value, so an unresolved target base never produced the unknown-name warning.
`_x.a = 1`, `_x.a += 2`, `_x[0] = 3` and `_x.a: T = v` only visited the assigned value, so an unresolved target base never produced the unknown-name warning.