[3.10] bpo-43897: Reject "_" captures and top-level MatchStar in the AST validator (GH-27432) (GH-27435)



(cherry picked from commit 8d0647485db5af2a0f0929d6509479ca45f1281b)


Co-authored-by: Brandt Bucher <brandt@python.org>

Automerge-Triggered-By: GH:brandtbucher
2 files changed