[Jump to usage instructions](#usage)
##Lints
-There are 131 lints included in this crate:
+There are 132 lints included in this crate:
name | default | meaning
---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[unstable_as_mut_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_mut_slice) | warn | as_mut_slice is not stable and can be replaced by &mut v[..]see https://github.com/rust-lang/rust/issues/27729
[unstable_as_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_slice) | warn | as_slice is not stable and can be replaced by & v[..]see https://github.com/rust-lang/rust/issues/27729
[unused_collect](https://github.com/Manishearth/rust-clippy/wiki#unused_collect) | warn | `collect()`ing an iterator without using the result; this is usually better written as a for loop
+[unused_label](https://github.com/Manishearth/rust-clippy/wiki#unused_label) | warn | unused label
[unused_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#unused_lifetimes) | warn | unused lifetimes in function definitions
[use_debug](https://github.com/Manishearth/rust-clippy/wiki#use_debug) | allow | use `Debug`-based formatting
[used_underscore_binding](https://github.com/Manishearth/rust-clippy/wiki#used_underscore_binding) | warn | using a binding which is prefixed with an underscore
pub mod transmute;
pub mod types;
pub mod unicode;
+pub mod unused_label;
pub mod vec;
pub mod zero_div_zero;
// end lints modules, do not remove this comment, it’s used in `update_lints`
reg.register_late_lint_pass(box swap::Swap);
reg.register_early_lint_pass(box if_not_else::IfNotElse);
reg.register_late_lint_pass(box overflow_check_conditional::OverflowCheckConditional);
+ reg.register_late_lint_pass(box unused_label::UnusedLabel);
reg.register_lint_group("clippy_pedantic", vec![
enum_glob_use::ENUM_GLOB_USE,
types::TYPE_COMPLEXITY,
types::UNIT_CMP,
unicode::ZERO_WIDTH_SPACE,
+ unused_label::UNUSED_LABEL,
vec::USELESS_VEC,
zero_div_zero::ZERO_DIVIDED_BY_ZERO,
]);
--- /dev/null
+use rustc::lint::*;
+use rustc_front::hir;
+use rustc_front::intravisit::{FnKind, Visitor, walk_expr, walk_fn};
+use std::collections::HashMap;
+use syntax::ast;
+use syntax::codemap::Span;
+use syntax::parse::token::InternedString;
+use utils::{in_macro, span_lint};
+
+/// **What it does:** This lint checks for unused labels.
+///
+/// **Why is this bad?** Maybe the label should be used in which case there is an error in the
+/// code or it should be removed.
+///
+/// **Known problems:** Hopefully none.
+///
+/// **Example:**
+/// ```rust,ignore
+/// fn unused_label() {
+/// 'label: for i in 1..2 {
+/// if i > 4 { continue }
+/// }
+/// ```
+declare_lint! {
+ pub UNUSED_LABEL,
+ Warn,
+ "unused label"
+}
+
+pub struct UnusedLabel;
+
+#[derive(Default)]
+struct UnusedLabelVisitor {
+ labels: HashMap<InternedString, Span>,
+}
+
+impl UnusedLabelVisitor {
+ pub fn new() -> UnusedLabelVisitor {
+ ::std::default::Default::default()
+ }
+}
+
+impl LintPass for UnusedLabel {
+ fn get_lints(&self) -> LintArray {
+ lint_array!(UNUSED_LABEL)
+ }
+}
+
+impl LateLintPass for UnusedLabel {
+ fn check_fn(&mut self, cx: &LateContext, kind: FnKind, decl: &hir::FnDecl, body: &hir::Block, span: Span, _: ast::NodeId) {
+ if in_macro(cx, span) {
+ return;
+ }
+
+ let mut v = UnusedLabelVisitor::new();
+ walk_fn(&mut v, kind, decl, body, span);
+
+ for (label, span) in v.labels {
+ span_lint(cx, UNUSED_LABEL, span, &format!("unused label `{}`", label));
+ }
+ }
+}
+
+impl<'v> Visitor<'v> for UnusedLabelVisitor {
+ fn visit_expr(&mut self, expr: &hir::Expr) {
+ match expr.node {
+ hir::ExprBreak(Some(label)) | hir::ExprAgain(Some(label)) => {
+ self.labels.remove(&label.node.name.as_str());
+ }
+ hir::ExprLoop(_, Some(label)) | hir::ExprWhile(_, _, Some(label)) => {
+ self.labels.insert(label.name.as_str(), expr.span);
+ }
+ _ => (),
+ }
+
+ walk_expr(self, expr);
+ }
+}
--- /dev/null
+#![plugin(clippy)]
+#![feature(plugin)]
+
+#![allow(dead_code, items_after_statements)]
+#![deny(unused_label)]
+
+fn unused_label() {
+ 'label: for i in 1..2 { //~ERROR: unused label `'label`
+ if i > 4 { continue }
+ }
+}
+
+fn foo() {
+ 'same_label_in_two_fns: loop {
+ break 'same_label_in_two_fns;
+ }
+}
+
+
+fn bla() {
+ 'a: loop { break } //~ERROR: unused label `'a`
+ fn blub() {}
+}
+
+fn main() {
+ 'a: for _ in 0..10 {
+ while let Some(42) = None {
+ continue 'a;
+ }
+ }
+
+ 'same_label_in_two_fns: loop { //~ERROR: unused label `'same_label_in_two_fns`
+ let _ = 1;
+ }
+}