mypy doesn't flag continue/break/return in except*

[jakkdl]

Feature
continue/break/return in except* is a syntax error, see https://peps.python.org/pep-0654/#forbidden-combinations.

def foo():
    for _ in range(5):
        try:
            ...
        except* Exception:
            continue
        except* ValueError:
            break
        except* TypeError:
            return

$ mypy --python-version=3.11 foo.py
Success: no issues found in 1 source file
$ mypy --version
mypy 1.13.0 (compiled: yes)

Pitch
mypy does give an error if you try to combine except and except*, and as far as I know it flags all other syntax errors as well, so should probably handle this too. It might also cause users to adjust code to avoid unreachable code needlessly, when in fact they have bigger problems to fix first.

[coldwolverine]

I'd like to work on this!

[brianschubert]

@coldwolverine great! You can check out CONTRIBUTING.md and the Developer Guides for contributing guidelines and tips on where to start.

I'm guessing this feature will involve adding some new state to the semantic analyzer to keep track of whether its currently inside an except* block. While working on this feature, be mindful of edge cases like nested try statements and function definitions or loops inside the except* block.