Inconsistent types for variable with partial type #4484

In the example below the variable seemingly has two types (None and x) which is wrong. This also results in an inconsistency with fine-grained incremental mode.

x = None

def f() -> None:
    reveal_type(x)  # None
    if x:
        1()  # No error, considered as not reachable
        y = 1
    else:
        y = ''  # No error

x = 1
reveal_type(x)  # int

The expected behavior is for x to always have the type int and for every line in the example to be considered reachable.