Type inference issue in Pylance for a variable of Union type

I'm writing a function with different behaviors depending on whether the argument is a scalar or a NumPy array. However, I'm getting the following two typing errors that I don't know how to solve:

1. Expression of type "generic | bool | int | float | complex | str | bytes | memoryview" cannot be assigned to return type "float"
Type "generic | bool | int | float | complex | str | bytes | memoryview" cannot be assigned to type "float"
"bytes" is incompatible with "float" PylancereportGeneralTypeIssues
2. "__ getitem __" method not defined on type "float" PylancereportGeneralTypeIssues**.

How can I let Pylance know that if the code reaches the expressions inside the if statement x should be a float, and if it reaches the else expresssions x should be a NumPy array?

Example code:

import numpy as np
import numpy.typing as npt
def func(x: float | npt.NDArray[np.float64]) -> float:
    if np.isscalar(x):
        return x     # Error 1)
    else:
        return x[0]  # Error 2)
def main():
    x = 0.4
    print(func(x))
if __name__ == "__main__":
    main()

One possibility is to add an assert or a cast to force it to be treated as a float. Any of the following will work:

assert isinstance(x, float)
x = cast(float, x)
x = float(x)  # type: ignore

All together:

def func(x: float | npt.NDArray[np.float64]) -> float:
    if np.isscalar(x):
        assert isinstance(x, float)
        return x
    else:
        assert not isinstance(x, float)
        return x[0]

...although, more direct would have been:

def func(x: float | npt.NDArray[np.float64]) -> float:
    return x if isinstance(x, float) else x[0]

...unless you're relying upon np.isscalar to do something other than what these type signatures suggest.