symtable entries should expose the scope attributes computed by the analysis

Feature or enhancement

The symbol table analysis computes a number of per-scope attributes that the compiler relies on, but does not expose them. I propose to add them as read-only attributes of the symbol table entries: is_generator, is_coroutine, has_annotations, has_conditional_annotations, needs_class_closure, needs_classdict, can_see_class_scope and annotation_block.

>>> import _symtable
>>> top = _symtable.symtable("async def f(): yield", "<string>", "exec")
>>> f = next(c for c in top.children if c.name == "f")
>>> f.is_generator, f.is_coroutine
(True, True)

A consumer currently has to re-derive these by walking the AST and replicating the exact rules of Python/symtable.c, which can change between versions. Trivially derivable attributes (like whether a function has a *args parameter or a docstring) are left out, but can be added later.

Linked PRs

• gh-153850

Start by reviewing linked PR gh-153850, then read the scope analysis in Python/symtable.c, which the issue identifies as the source of these attributes. Verify that the requested values are exposed as read-only symbol-table entry attributes and that the linked PR covers the stated cases.