Add more cases to `test_patma`

[sobolevn]

While anwsering #106133 I've noticed that test_patma does not have tests for some corner-cases:

1. Case case [x] | x: ... is mentined in https://peps.python.org/pep-0634/#capture-patterns but is never tested, the closest we have to it is case [z] | [1, (0 | 1 as z)] | [z]:, which is not the same
2. Guards can have side effects according to https://peps.python.org/pep-0634/#guards but it is never tested
3. Guards are never tested with: mapping patterns, dotted value patterns
4. In ClassPattern section PEP says: If name_or_attr is not an instance of the builtin type, TypeError is raised. It is never tested in TestTypeErrors
5. LiteralPattern might have some more expected SyntaxError cases, like using * and /, using three numbers like 0 + 0j + 0
6. LiteralPattern says: The singleton literals None, True and False are compared using the is operator., but only None is checked

I would like to send a PR with the new test cases.

Linked PRs

• gh-106135: Improve test_patma with more cases #106271

[terryjreedy]

Seems like a good idea. Question: case x, x: pass evokes SyntaxError: incomplete input for any statement. Does this seem right or should I open an issue?

[sobolevn]

@terryjreedy yes, this is not allowed: https://peps.python.org/pep-0634/#capture-patterns

This disallows for example case x, x: ...

[brandtbucher]

Thanks for taking this on, it's definitely appreciated! Please ping me for review once it's ready. :)