+
+/// Calls `cb` on each expression inside `expr` that is at "tail position".
+/// Does not walk into `break` or `return` expressions.
+/// Note that modifying the tree while iterating it will cause undefined iteration which might
+/// potentially results in an out of bounds panic.
+pub fn for_each_tail_expr(expr: &ast::Expr, cb: &mut dyn FnMut(&ast::Expr)) {
+ match expr {
+ ast::Expr::BlockExpr(b) => {
+ match b.modifier() {
+ Some(
+ ast::BlockModifier::Async(_)
+ | ast::BlockModifier::Try(_)
+ | ast::BlockModifier::Const(_),
+ ) => return cb(expr),
+
+ Some(ast::BlockModifier::Label(label)) => {
+ for_each_break_expr(Some(label), b.stmt_list(), &mut |b| {
+ cb(&ast::Expr::BreakExpr(b))
+ });
+ }
+ Some(ast::BlockModifier::Unsafe(_)) => (),
+ None => (),
+ }
+ if let Some(stmt_list) = b.stmt_list() {
+ if let Some(e) = stmt_list.tail_expr() {
+ for_each_tail_expr(&e, cb);
+ }
+ }
+ }
+ ast::Expr::IfExpr(if_) => {
+ let mut if_ = if_.clone();
+ loop {
+ if let Some(block) = if_.then_branch() {
+ for_each_tail_expr(&ast::Expr::BlockExpr(block), cb);
+ }
+ match if_.else_branch() {
+ Some(ast::ElseBranch::IfExpr(it)) => if_ = it,
+ Some(ast::ElseBranch::Block(block)) => {
+ for_each_tail_expr(&ast::Expr::BlockExpr(block), cb);
+ break;
+ }
+ None => break,
+ }
+ }
+ }
+ ast::Expr::LoopExpr(l) => {
+ for_each_break_expr(l.label(), l.loop_body().and_then(|it| it.stmt_list()), &mut |b| {
+ cb(&ast::Expr::BreakExpr(b))
+ })
+ }
+ ast::Expr::MatchExpr(m) => {
+ if let Some(arms) = m.match_arm_list() {
+ arms.arms().filter_map(|arm| arm.expr()).for_each(|e| for_each_tail_expr(&e, cb));
+ }
+ }
+ ast::Expr::ArrayExpr(_)
+ | ast::Expr::AwaitExpr(_)
+ | ast::Expr::BinExpr(_)
+ | ast::Expr::BoxExpr(_)
+ | ast::Expr::BreakExpr(_)
+ | ast::Expr::CallExpr(_)
+ | ast::Expr::CastExpr(_)
+ | ast::Expr::ClosureExpr(_)
+ | ast::Expr::ContinueExpr(_)
+ | ast::Expr::FieldExpr(_)
+ | ast::Expr::ForExpr(_)
+ | ast::Expr::IndexExpr(_)
+ | ast::Expr::Literal(_)
+ | ast::Expr::MacroCall(_)
+ | ast::Expr::MacroStmts(_)
+ | ast::Expr::MethodCallExpr(_)
+ | ast::Expr::ParenExpr(_)
+ | ast::Expr::PathExpr(_)
+ | ast::Expr::PrefixExpr(_)
+ | ast::Expr::RangeExpr(_)
+ | ast::Expr::RecordExpr(_)
+ | ast::Expr::RefExpr(_)
+ | ast::Expr::ReturnExpr(_)
+ | ast::Expr::TryExpr(_)
+ | ast::Expr::TupleExpr(_)
+ | ast::Expr::WhileExpr(_)
+ | ast::Expr::YieldExpr(_) => cb(expr),
+ }
+}
+
+/// Calls `cb` on each break expr inside of `body` that is applicable for the given label.
+pub fn for_each_break_expr(
+ label: Option<ast::Label>,
+ body: Option<ast::StmtList>,
+ cb: &mut dyn FnMut(ast::BreakExpr),
+) {
+ let label = label.and_then(|lbl| lbl.lifetime());
+ let mut depth = 0;
+ if let Some(b) = body {
+ let preorder = &mut b.syntax().preorder();
+ let ev_as_expr = |ev| match ev {
+ WalkEvent::Enter(it) => Some(WalkEvent::Enter(ast::Expr::cast(it)?)),
+ WalkEvent::Leave(it) => Some(WalkEvent::Leave(ast::Expr::cast(it)?)),
+ };
+ let eq_label = |lt: Option<ast::Lifetime>| {
+ lt.zip(label.as_ref()).map_or(false, |(lt, lbl)| lt.text() == lbl.text())
+ };
+ while let Some(node) = preorder.find_map(ev_as_expr) {
+ match node {
+ WalkEvent::Enter(expr) => match expr {
+ ast::Expr::LoopExpr(_) | ast::Expr::WhileExpr(_) | ast::Expr::ForExpr(_) => {
+ depth += 1
+ }
+ ast::Expr::BlockExpr(e) if e.label().is_some() => depth += 1,
+ ast::Expr::BreakExpr(b)
+ if (depth == 0 && b.lifetime().is_none()) || eq_label(b.lifetime()) =>
+ {
+ cb(b);
+ }
+ _ => (),
+ },
+ WalkEvent::Leave(expr) => match expr {
+ ast::Expr::LoopExpr(_) | ast::Expr::WhileExpr(_) | ast::Expr::ForExpr(_) => {
+ depth -= 1
+ }
+ ast::Expr::BlockExpr(e) if e.label().is_some() => depth -= 1,
+ _ => (),
+ },
+ }
+ }
+ }
+}