Non-overlapping identity check when left operand is not optional and right operand is None

mypy does not complain on line 4 of this code:
```python
i: int = 1
s: str = 'hi'
i is s # error: Non-overlapping identity check (left operand type: "int", right operand type: "str")
if i is None: # ok
 ...
```
would it be possible to raise a *Non-overlapping identity check* error in that case, as in the previous line?

mypy version:
```
$ mypy --version
mypy 0.930
```