feat: add type statement support (PEP-695, Python 3.12 and 3.13)

[wookayin]

Overview

• Basic type statement support (3.12), any following code should not lose their variable scope
• bound and default parameter support (3.13)
• The new generic syntax, e.g. class Generic[T], def generic_method[T], def func[T](...), etc. (3.12)

References:

• https://docs.python.org/3/library/typing.html#type-aliases
• https://peps.python.org/pep-0695/

Example 1:

type MyList[T] = list[T]

def foo():
   mylist: MyList[int] = [1, 2, 3]   # semshi used to break here

Example 2: bound and default (python 3.13):

type Alias1[T, P] = list[P] | set[T]
type Alias2[T, P: type[T]] = list[P] | set[T]
type Alias3[T, P = T] = list[P] | set[T]
type Alias4[T: int, P: int = bool | T] = list[P] | set[T]

Example 3: generic syntax

def get_first[T: float](data: list[T]) -> T:
   ...

class Foo[**P, R]:
    fn: Callable[P, R]
    def __call__(self, *args: P.args, **kwargs: P.kwargs) -> R:
        ...

[wookayin]

Parser and AST visitation works fine now, but semantic reference tracking within (nested) lexical scopes is not quite accurate:

e.g.

def func1[**P, R](func: Callable[P, R], /, *args: *tuple[()]) -> Callable[P, R]: ...

We could still merge the basic support and later fix the bug as a follow-up.