{"ast_node_type":"function","tokens":[{"end":94,"kind":"keyword","start":0,"text":"fn"}]}
fn select_arm(ecx: &ExtCtxt<'_>, branches: CfgSelectBranches) -> Option<(TokenStream, Span)> {
/// Selects the first arm whose predicate evaluates to true.
    for (cfg, tt, arm_span) in branches.reachable {