Red-knot currently doesn't emit a diagnostic on this snippet:

raise 42

But we should, since 42 is not a valid object to be used in a raise statement:

>>> raise 42
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    raise 42
TypeError: exceptions must derive from BaseException

The rule is that the object used in a raise statement must have a type that is assignable to the type BaseException | type[BaseException], since both of the following work:

>>> raise ValueError
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    raise ValueError
ValueError
>>> raise ValueError()
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    raise ValueError()
ValueError

We need to add some extra logic to this branch here:

I think this will probably need to be a new rule added to https://github.com/astral-sh/ruff/blob/main/crates/red_knot_python_semantic/src/types/diagnostic.rs ? I don't think it fits neatly into any other rule. The alternative might be to make the existing INVALID_EXCEPTION_CAUGHT rule broader (and rename it).