Function derives_structural_eq 

pub fn derives_structural_eq(node: &AIRNode) -> bool

True when a RecordDecl / EnumDecl node carries the checker’s bock_types::checker::DERIVE_EQ_META_KEY stamp — the type conforms to Equatable structurally (DQ29) and declares no explicit impl, so the Rust backend adds PartialEq to its #[derive(..)] list.