Function for_each_node 

pub fn for_each_node<'w, 'a>(
    stmts: &'w [Stmt<'a>],
    visit: impl FnMut(Visited<'w, 'a>),
)

Visit every statement and expression in stmts, each once — the same exhaustive child enumeration the depth gate walks, so a new variant’s children are reached here the moment the gate reaches them. Iterative, like the gate: visiting must never be what overflows.