1 //! checks for attributes
4 first_line_of_span, is_present_in_source, match_panic_def_id, snippet_opt, span_lint, span_lint_and_help,
5 span_lint_and_sugg, span_lint_and_then, without_block_comments,
7 use if_chain::if_chain;
8 use rustc_ast::{AttrKind, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
9 use rustc_errors::Applicability;
11 Block, Expr, ExprKind, ImplItem, ImplItemKind, Item, ItemKind, StmtKind, TraitFn, TraitItem, TraitItemKind,
13 use rustc_lint::{CheckLintNameResult, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
14 use rustc_middle::lint::in_external_macro;
16 use rustc_session::{declare_lint_pass, declare_tool_lint};
17 use rustc_span::lev_distance::find_best_match_for_name;
18 use rustc_span::source_map::Span;
20 use rustc_span::symbol::{Symbol, SymbolStr};
23 static UNIX_SYSTEMS: &[&str] = &[
42 // NOTE: windows is excluded from the list because it's also a valid target family.
43 static NON_UNIX_SYSTEMS: &[&str] = &["hermit", "none", "wasi"];
45 declare_clippy_lint! {
46 /// **What it does:** Checks for items annotated with `#[inline(always)]`,
47 /// unless the annotated function is empty or simply panics.
49 /// **Why is this bad?** While there are valid uses of this annotation (and once
50 /// you know when to use it, by all means `allow` this lint), it's a common
51 /// newbie-mistake to pepper one's code with it.
53 /// As a rule of thumb, before slapping `#[inline(always)]` on a function,
54 /// measure if that additional function call really affects your runtime profile
55 /// sufficiently to make up for the increase in compile time.
57 /// **Known problems:** False positives, big time. This lint is meant to be
58 /// deactivated by everyone doing serious performance work. This means having
59 /// done the measurement.
64 /// fn not_quite_hot_code(..) { ... }
68 "use of `#[inline(always)]`"
71 declare_clippy_lint! {
72 /// **What it does:** Checks for `extern crate` and `use` items annotated with
75 /// This lint permits `#[allow(unused_imports)]`, `#[allow(deprecated)]`,
76 /// `#[allow(unreachable_pub)]`, `#[allow(clippy::wildcard_imports)]` and
77 /// `#[allow(clippy::enum_glob_use)]` on `use` items and `#[allow(unused_imports)]` on
78 /// `extern crate` items with a `#[macro_use]` attribute.
80 /// **Why is this bad?** Lint attributes have no effect on crate imports. Most
81 /// likely a `!` was forgotten.
83 /// **Known problems:** None.
88 /// #[deny(dead_code)]
90 /// #[forbid(dead_code)]
94 /// #[allow(unused_imports)]
96 /// #[allow(unused_imports)]
100 pub USELESS_ATTRIBUTE,
102 "use of lint attributes on `extern crate` items"
105 declare_clippy_lint! {
106 /// **What it does:** Checks for `#[deprecated]` annotations with a `since`
107 /// field that is not a valid semantic version.
109 /// **Why is this bad?** For checking the version of the deprecation, it must be
110 /// a valid semver. Failing that, the contained information is useless.
112 /// **Known problems:** None.
116 /// #[deprecated(since = "forever")]
117 /// fn something_else() { /* ... */ }
119 pub DEPRECATED_SEMVER,
121 "use of `#[deprecated(since = \"x\")]` where x is not semver"
124 declare_clippy_lint! {
125 /// **What it does:** Checks for empty lines after outer attributes
127 /// **Why is this bad?**
128 /// Most likely the attribute was meant to be an inner attribute using a '!'.
129 /// If it was meant to be an outer attribute, then the following item
130 /// should not be separated by empty lines.
132 /// **Known problems:** Can cause false positives.
134 /// From the clippy side it's difficult to detect empty lines between an attributes and the
135 /// following item because empty lines and comments are not part of the AST. The parsing
136 /// currently works for basic cases but is not perfect.
140 /// // Good (as inner attribute)
141 /// #![allow(dead_code)]
143 /// fn this_is_fine() { }
146 /// #[allow(dead_code)]
148 /// fn not_quite_good_code() { }
150 /// // Good (as outer attribute)
151 /// #[allow(dead_code)]
152 /// fn this_is_fine_too() { }
154 pub EMPTY_LINE_AFTER_OUTER_ATTR,
156 "empty line after outer attribute"
159 declare_clippy_lint! {
160 /// **What it does:** Checks for `allow`/`warn`/`deny`/`forbid` attributes with scoped clippy
161 /// lints and if those lints exist in clippy. If there is an uppercase letter in the lint name
162 /// (not the tool name) and a lowercase version of this lint exists, it will suggest to lowercase
165 /// **Why is this bad?** A lint attribute with a mistyped lint name won't have an effect.
167 /// **Known problems:** None.
172 /// #![warn(if_not_els)]
173 /// #![deny(clippy::All)]
178 /// #![warn(if_not_else)]
179 /// #![deny(clippy::all)]
181 pub UNKNOWN_CLIPPY_LINTS,
183 "unknown_lints for scoped Clippy lints"
186 declare_clippy_lint! {
187 /// **What it does:** Checks for `warn`/`deny`/`forbid` attributes targeting the whole clippy::restriction category.
189 /// **Why is this bad?** Restriction lints sometimes are in contrast with other lints or even go against idiomatic rust.
190 /// These lints should only be enabled on a lint-by-lint basis and with careful consideration.
192 /// **Known problems:** None.
197 /// #![deny(clippy::restriction)]
202 /// #![deny(clippy::as_conversions)]
204 pub BLANKET_CLIPPY_RESTRICTION_LINTS,
206 "enabling the complete restriction group"
209 declare_clippy_lint! {
210 /// **What it does:** Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
211 /// with `#[rustfmt::skip]`.
213 /// **Why is this bad?** Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
214 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
216 /// **Known problems:** This lint doesn't detect crate level inner attributes, because they get
217 /// processed before the PreExpansionPass lints get executed. See
218 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
224 /// #[cfg_attr(rustfmt, rustfmt_skip)]
233 pub DEPRECATED_CFG_ATTR,
235 "usage of `cfg_attr(rustfmt)` instead of tool attributes"
238 declare_clippy_lint! {
239 /// **What it does:** Checks for cfg attributes having operating systems used in target family position.
241 /// **Why is this bad?** The configuration option will not be recognised and the related item will not be included
242 /// by the conditional compilation engine.
244 /// **Known problems:** None.
251 /// fn conditional() { }
256 /// #[cfg(target_os = "linux")]
257 /// fn conditional() { }
263 /// fn conditional() { }
265 /// Check the [Rust Reference](https://doc.rust-lang.org/reference/conditional-compilation.html#target_os) for more details.
266 pub MISMATCHED_TARGET_OS,
268 "usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
271 declare_lint_pass!(Attributes => [
275 UNKNOWN_CLIPPY_LINTS,
276 BLANKET_CLIPPY_RESTRICTION_LINTS,
279 impl<'tcx> LateLintPass<'tcx> for Attributes {
280 fn check_attribute(&mut self, cx: &LateContext<'tcx>, attr: &'tcx Attribute) {
281 if let Some(items) = &attr.meta_item_list() {
282 if let Some(ident) = attr.ident() {
283 let ident = &*ident.as_str();
285 "allow" | "warn" | "deny" | "forbid" => {
286 check_clippy_lint_names(cx, ident, items);
290 if items.is_empty() || !attr.has_name(sym::deprecated) {
295 if let NestedMetaItem::MetaItem(mi) = &item;
296 if let MetaItemKind::NameValue(lit) = &mi.kind;
297 if mi.has_name(sym::since);
299 check_semver(cx, item.span(), lit);
307 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
308 if is_relevant_item(cx, item) {
309 check_attrs(cx, item.span, item.ident.name, &item.attrs)
312 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
313 let skip_unused_imports = item.attrs.iter().any(|attr| attr.has_name(sym::macro_use));
315 for attr in item.attrs {
316 if in_external_macro(cx.sess(), attr.span) {
319 if let Some(lint_list) = &attr.meta_item_list() {
320 if let Some(ident) = attr.ident() {
321 match &*ident.as_str() {
322 "allow" | "warn" | "deny" | "forbid" => {
323 // permit `unused_imports`, `deprecated`, `unreachable_pub`,
324 // `clippy::wildcard_imports`, and `clippy::enum_glob_use` for `use` items
325 // and `unused_imports` for `extern crate` items with `macro_use`
326 for lint in lint_list {
328 ItemKind::Use(..) => {
329 if is_word(lint, sym!(unused_imports))
330 || is_word(lint, sym::deprecated)
331 || is_word(lint, sym!(unreachable_pub))
332 || is_word(lint, sym!(unused))
333 || extract_clippy_lint(lint)
334 .map_or(false, |s| s == "wildcard_imports")
335 || extract_clippy_lint(lint).map_or(false, |s| s == "enum_glob_use")
340 ItemKind::ExternCrate(..) => {
341 if is_word(lint, sym!(unused_imports)) && skip_unused_imports {
344 if is_word(lint, sym!(unused_extern_crates)) {
351 let line_span = first_line_of_span(cx, attr.span);
353 if let Some(mut sugg) = snippet_opt(cx, line_span) {
354 if sugg.contains("#[") {
359 "useless lint attribute",
361 sugg = sugg.replacen("#[", "#![", 1);
362 diag.span_suggestion(
364 "if you just forgot a `!`, use",
366 Applicability::MaybeIncorrect,
383 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
384 if is_relevant_impl(cx, item) {
385 check_attrs(cx, item.span, item.ident.name, &item.attrs)
389 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
390 if is_relevant_trait(cx, item) {
391 check_attrs(cx, item.span, item.ident.name, &item.attrs)
396 /// Returns the lint name if it is clippy lint.
397 fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<SymbolStr> {
399 if let Some(meta_item) = lint.meta_item();
400 if meta_item.path.segments.len() > 1;
401 if let tool_name = meta_item.path.segments[0].ident;
402 if tool_name.name == sym::clippy;
403 let lint_name = meta_item.path.segments.last().unwrap().ident.name;
405 return Some(lint_name.as_str());
411 fn check_clippy_lint_names(cx: &LateContext<'_>, ident: &str, items: &[NestedMetaItem]) {
412 let lint_store = cx.lints();
414 if let Some(lint_name) = extract_clippy_lint(lint) {
415 if let CheckLintNameResult::Tool(Err((None, _))) = lint_store.check_lint_name(&lint_name, Some(sym::clippy))
419 UNKNOWN_CLIPPY_LINTS,
421 &format!("unknown clippy lint: clippy::{}", lint_name),
423 let name_lower = lint_name.to_lowercase();
424 let symbols = lint_store
427 .map(|l| Symbol::intern(&l.name_lower()))
428 .collect::<Vec<_>>();
429 let sugg = find_best_match_for_name(
431 Symbol::intern(&format!("clippy::{}", name_lower)),
434 if lint_name.chars().any(char::is_uppercase)
435 && lint_store.find_lints(&format!("clippy::{}", name_lower)).is_ok()
437 diag.span_suggestion(
439 "lowercase the lint name",
440 format!("clippy::{}", name_lower),
441 Applicability::MachineApplicable,
443 } else if let Some(sugg) = sugg {
444 diag.span_suggestion(
448 Applicability::MachineApplicable,
453 } else if lint_name == "restriction" && ident != "allow" {
456 BLANKET_CLIPPY_RESTRICTION_LINTS,
458 "restriction lints are not meant to be all enabled",
460 "try enabling only the lints you really need",
467 fn is_relevant_item(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
468 if let ItemKind::Fn(_, _, eid) = item.kind {
469 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
475 fn is_relevant_impl(cx: &LateContext<'_>, item: &ImplItem<'_>) -> bool {
477 ImplItemKind::Fn(_, eid) => is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value),
482 fn is_relevant_trait(cx: &LateContext<'_>, item: &TraitItem<'_>) -> bool {
484 TraitItemKind::Fn(_, TraitFn::Required(_)) => true,
485 TraitItemKind::Fn(_, TraitFn::Provided(eid)) => {
486 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
492 fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, block: &Block<'_>) -> bool {
493 block.stmts.first().map_or(
497 .map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
498 |stmt| match &stmt.kind {
499 StmtKind::Local(_) => true,
500 StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
506 fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, expr: &Expr<'_>) -> bool {
508 ExprKind::Block(block, _) => is_relevant_block(cx, typeck_results, block),
509 ExprKind::Ret(Some(e)) => is_relevant_expr(cx, typeck_results, e),
510 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
511 ExprKind::Call(path_expr, _) => {
512 if let ExprKind::Path(qpath) = &path_expr.kind {
514 .qpath_res(qpath, path_expr.hir_id)
516 .map_or(true, |fun_id| !match_panic_def_id(cx, fun_id))
525 fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribute]) {
526 if span.from_expansion() {
531 if let Some(values) = attr.meta_item_list() {
532 if values.len() != 1 || !attr.has_name(sym::inline) {
535 if is_word(&values[0], sym::always) {
541 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
550 fn check_semver(cx: &LateContext<'_>, span: Span, lit: &Lit) {
551 if let LitKind::Str(is, _) = lit.kind {
552 if Version::parse(&is.as_str()).is_ok() {
560 "the since field must contain a semver-compliant version",
564 fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool {
565 if let NestedMetaItem::MetaItem(mi) = &nmi {
566 mi.is_word() && mi.has_name(expected)
572 declare_lint_pass!(EarlyAttributes => [
574 MISMATCHED_TARGET_OS,
575 EMPTY_LINE_AFTER_OUTER_ATTR,
578 impl EarlyLintPass for EarlyAttributes {
579 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
580 check_empty_line_after_outer_attr(cx, item);
583 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
584 check_deprecated_cfg_attr(cx, attr);
585 check_mismatched_target_os(cx, attr);
589 fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
590 for attr in &item.attrs {
591 let attr_item = if let AttrKind::Normal(ref attr, _) = attr.kind {
597 if attr.style == AttrStyle::Outer {
598 if attr_item.args.inner_tokens().is_empty() || !is_present_in_source(cx, attr.span) {
602 let begin_of_attr_to_item = Span::new(attr.span.lo(), item.span.lo(), item.span.ctxt());
603 let end_of_attr_to_item = Span::new(attr.span.hi(), item.span.lo(), item.span.ctxt());
605 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) {
606 let lines = snippet.split('\n').collect::<Vec<_>>();
607 let lines = without_block_comments(lines);
609 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
612 EMPTY_LINE_AFTER_OUTER_ATTR,
613 begin_of_attr_to_item,
614 "found an empty line after an outer attribute. \
615 Perhaps you forgot to add a `!` to make it an inner attribute?",
623 fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute) {
626 if attr.has_name(sym::cfg_attr);
627 if let Some(items) = attr.meta_item_list();
629 // check for `rustfmt`
630 if let Some(feature_item) = items[0].meta_item();
631 if feature_item.has_name(sym::rustfmt);
632 // check for `rustfmt_skip` and `rustfmt::skip`
633 if let Some(skip_item) = &items[1].meta_item();
634 if skip_item.has_name(sym!(rustfmt_skip)) ||
635 skip_item.path.segments.last().expect("empty path in attribute").ident.name == sym!(skip);
636 // Only lint outer attributes, because custom inner attributes are unstable
637 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
638 if let AttrStyle::Outer = attr.style;
644 "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
646 "#[rustfmt::skip]".to_string(),
647 Applicability::MachineApplicable,
653 fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
654 fn find_os(name: &str) -> Option<&'static str> {
657 .chain(NON_UNIX_SYSTEMS.iter())
658 .find(|&&os| os == name)
662 fn is_unix(name: &str) -> bool {
663 UNIX_SYSTEMS.iter().any(|&os| os == name)
666 fn find_mismatched_target_os(items: &[NestedMetaItem]) -> Vec<(&str, Span)> {
667 let mut mismatched = Vec::new();
670 if let NestedMetaItem::MetaItem(meta) = item {
672 MetaItemKind::List(list) => {
673 mismatched.extend(find_mismatched_target_os(&list));
675 MetaItemKind::Word => {
677 if let Some(ident) = meta.ident();
678 if let Some(os) = find_os(&*ident.name.as_str());
680 mismatched.push((os, ident.span));
693 if attr.has_name(sym::cfg);
694 if let Some(list) = attr.meta_item_list();
695 let mismatched = find_mismatched_target_os(&list);
696 if !mismatched.is_empty();
698 let mess = "operating system used in target family position";
700 span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, &mess, |diag| {
701 // Avoid showing the unix suggestion multiple times in case
702 // we have more than one mismatch for unix-like systems
703 let mut unix_suggested = false;
705 for (os, span) in mismatched {
706 let sugg = format!("target_os = \"{}\"", os);
707 diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
709 if !unix_suggested && is_unix(os) {
710 diag.help("Did you mean `unix`?");
711 unix_suggested = true;