1 //! checks for attributes
3 use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
4 use clippy_utils::msrvs;
5 use clippy_utils::source::{first_line_of_span, is_present_in_source, snippet_opt, without_block_comments};
6 use clippy_utils::{extract_msrv_attr, match_panic_def_id, meets_msrv};
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::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
14 use rustc_middle::lint::in_external_macro;
16 use rustc_semver::RustcVersion;
17 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
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! {
47 /// Checks for items annotated with `#[inline(always)]`,
48 /// unless the annotated function is empty or simply panics.
50 /// ### Why is this bad?
51 /// While there are valid uses of this annotation (and once
52 /// you know when to use it, by all means `allow` this lint), it's a common
53 /// newbie-mistake to pepper one's code with it.
55 /// As a rule of thumb, before slapping `#[inline(always)]` on a function,
56 /// measure if that additional function call really affects your runtime profile
57 /// sufficiently to make up for the increase in compile time.
59 /// ### Known problems
60 /// False positives, big time. This lint is meant to be
61 /// deactivated by everyone doing serious performance work. This means having
62 /// done the measurement.
67 /// fn not_quite_hot_code(..) { ... }
71 "use of `#[inline(always)]`"
74 declare_clippy_lint! {
76 /// Checks for `extern crate` and `use` items annotated with
79 /// This lint permits `#[allow(unused_imports)]`, `#[allow(deprecated)]`,
80 /// `#[allow(unreachable_pub)]`, `#[allow(clippy::wildcard_imports)]` and
81 /// `#[allow(clippy::enum_glob_use)]` on `use` items and `#[allow(unused_imports)]` on
82 /// `extern crate` items with a `#[macro_use]` attribute.
84 /// ### Why is this bad?
85 /// Lint attributes have no effect on crate imports. Most
86 /// likely a `!` was forgotten.
91 /// #[deny(dead_code)]
93 /// #[forbid(dead_code)]
97 /// #[allow(unused_imports)]
99 /// #[allow(unused_imports)]
101 /// extern crate baz;
103 pub USELESS_ATTRIBUTE,
105 "use of lint attributes on `extern crate` items"
108 declare_clippy_lint! {
110 /// Checks for `#[deprecated]` annotations with a `since`
111 /// field that is not a valid semantic version.
113 /// ### Why is this bad?
114 /// For checking the version of the deprecation, it must be
115 /// a valid semver. Failing that, the contained information is useless.
119 /// #[deprecated(since = "forever")]
120 /// fn something_else() { /* ... */ }
122 pub DEPRECATED_SEMVER,
124 "use of `#[deprecated(since = \"x\")]` where x is not semver"
127 declare_clippy_lint! {
129 /// Checks for empty lines after outer attributes
131 /// ### Why is this bad?
132 /// Most likely the attribute was meant to be an inner attribute using a '!'.
133 /// If it was meant to be an outer attribute, then the following item
134 /// should not be separated by empty lines.
136 /// ### Known problems
137 /// Can cause false positives.
139 /// From the clippy side it's difficult to detect empty lines between an attributes and the
140 /// following item because empty lines and comments are not part of the AST. The parsing
141 /// currently works for basic cases but is not perfect.
145 /// // Good (as inner attribute)
146 /// #![allow(dead_code)]
148 /// fn this_is_fine() { }
151 /// #[allow(dead_code)]
153 /// fn not_quite_good_code() { }
155 /// // Good (as outer attribute)
156 /// #[allow(dead_code)]
157 /// fn this_is_fine_too() { }
159 pub EMPTY_LINE_AFTER_OUTER_ATTR,
161 "empty line after outer attribute"
164 declare_clippy_lint! {
166 /// Checks for `warn`/`deny`/`forbid` attributes targeting the whole clippy::restriction category.
168 /// ### Why is this bad?
169 /// Restriction lints sometimes are in contrast with other lints or even go against idiomatic rust.
170 /// These lints should only be enabled on a lint-by-lint basis and with careful consideration.
175 /// #![deny(clippy::restriction)]
180 /// #![deny(clippy::as_conversions)]
182 pub BLANKET_CLIPPY_RESTRICTION_LINTS,
184 "enabling the complete restriction group"
187 declare_clippy_lint! {
189 /// Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
190 /// with `#[rustfmt::skip]`.
192 /// ### Why is this bad?
193 /// Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
194 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
196 /// ### Known problems
197 /// This lint doesn't detect crate level inner attributes, because they get
198 /// processed before the PreExpansionPass lints get executed. See
199 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
204 /// #[cfg_attr(rustfmt, rustfmt_skip)]
213 pub DEPRECATED_CFG_ATTR,
215 "usage of `cfg_attr(rustfmt)` instead of tool attributes"
218 declare_clippy_lint! {
220 /// Checks for cfg attributes having operating systems used in target family position.
222 /// ### Why is this bad?
223 /// The configuration option will not be recognised and the related item will not be included
224 /// by the conditional compilation engine.
230 /// fn conditional() { }
235 /// #[cfg(target_os = "linux")]
236 /// fn conditional() { }
242 /// fn conditional() { }
244 /// Check the [Rust Reference](https://doc.rust-lang.org/reference/conditional-compilation.html#target_os) for more details.
245 pub MISMATCHED_TARGET_OS,
247 "usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
250 declare_lint_pass!(Attributes => [
254 BLANKET_CLIPPY_RESTRICTION_LINTS,
257 impl<'tcx> LateLintPass<'tcx> for Attributes {
258 fn check_attribute(&mut self, cx: &LateContext<'tcx>, attr: &'tcx Attribute) {
259 if let Some(items) = &attr.meta_item_list() {
260 if let Some(ident) = attr.ident() {
261 if is_lint_level(ident.name) {
262 check_clippy_lint_names(cx, ident.name, items);
264 if items.is_empty() || !attr.has_name(sym::deprecated) {
269 if let NestedMetaItem::MetaItem(mi) = &item;
270 if let MetaItemKind::NameValue(lit) = &mi.kind;
271 if mi.has_name(sym::since);
273 check_semver(cx, item.span(), lit);
281 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
282 let attrs = cx.tcx.hir().attrs(item.hir_id());
283 if is_relevant_item(cx, item) {
284 check_attrs(cx, item.span, item.ident.name, attrs);
287 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
288 let skip_unused_imports = attrs.iter().any(|attr| attr.has_name(sym::macro_use));
291 if in_external_macro(cx.sess(), attr.span) {
294 if let Some(lint_list) = &attr.meta_item_list() {
295 if attr.ident().map_or(false, |ident| is_lint_level(ident.name)) {
296 // permit `unused_imports`, `deprecated`, `unreachable_pub`,
297 // `clippy::wildcard_imports`, and `clippy::enum_glob_use` for `use` items
298 // and `unused_imports` for `extern crate` items with `macro_use`
299 for lint in lint_list {
301 ItemKind::Use(..) => {
302 if is_word(lint, sym!(unused_imports))
303 || is_word(lint, sym::deprecated)
304 || is_word(lint, sym!(unreachable_pub))
305 || is_word(lint, sym!(unused))
306 || extract_clippy_lint(lint).map_or(false, |s| s == "wildcard_imports")
307 || extract_clippy_lint(lint).map_or(false, |s| s == "enum_glob_use")
312 ItemKind::ExternCrate(..) => {
313 if is_word(lint, sym!(unused_imports)) && skip_unused_imports {
316 if is_word(lint, sym!(unused_extern_crates)) {
323 let line_span = first_line_of_span(cx, attr.span);
325 if let Some(mut sugg) = snippet_opt(cx, line_span) {
326 if sugg.contains("#[") {
331 "useless lint attribute",
333 sugg = sugg.replacen("#[", "#![", 1);
334 diag.span_suggestion(
336 "if you just forgot a `!`, use",
338 Applicability::MaybeIncorrect,
352 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
353 if is_relevant_impl(cx, item) {
354 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
358 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
359 if is_relevant_trait(cx, item) {
360 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
365 /// Returns the lint name if it is clippy lint.
366 fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<SymbolStr> {
368 if let Some(meta_item) = lint.meta_item();
369 if meta_item.path.segments.len() > 1;
370 if let tool_name = meta_item.path.segments[0].ident;
371 if tool_name.name == sym::clippy;
373 let lint_name = meta_item.path.segments.last().unwrap().ident.name;
374 return Some(lint_name.as_str());
380 fn check_clippy_lint_names(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem]) {
382 if let Some(lint_name) = extract_clippy_lint(lint) {
383 if lint_name == "restriction" && name != sym::allow {
386 BLANKET_CLIPPY_RESTRICTION_LINTS,
388 "restriction lints are not meant to be all enabled",
390 "try enabling only the lints you really need",
397 fn is_relevant_item(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
398 if let ItemKind::Fn(_, _, eid) = item.kind {
399 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
405 fn is_relevant_impl(cx: &LateContext<'_>, item: &ImplItem<'_>) -> bool {
407 ImplItemKind::Fn(_, eid) => is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value),
412 fn is_relevant_trait(cx: &LateContext<'_>, item: &TraitItem<'_>) -> bool {
414 TraitItemKind::Fn(_, TraitFn::Required(_)) => true,
415 TraitItemKind::Fn(_, TraitFn::Provided(eid)) => {
416 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
422 fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, block: &Block<'_>) -> bool {
423 block.stmts.first().map_or(
427 .map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
428 |stmt| match &stmt.kind {
429 StmtKind::Local(_) => true,
430 StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
431 StmtKind::Item(_) => false,
436 fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, expr: &Expr<'_>) -> bool {
438 ExprKind::Block(block, _) => is_relevant_block(cx, typeck_results, block),
439 ExprKind::Ret(Some(e)) => is_relevant_expr(cx, typeck_results, e),
440 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
441 ExprKind::Call(path_expr, _) => {
442 if let ExprKind::Path(qpath) = &path_expr.kind {
444 .qpath_res(qpath, path_expr.hir_id)
446 .map_or(true, |fun_id| !match_panic_def_id(cx, fun_id))
455 fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribute]) {
456 if span.from_expansion() {
461 if let Some(values) = attr.meta_item_list() {
462 if values.len() != 1 || !attr.has_name(sym::inline) {
465 if is_word(&values[0], sym::always) {
471 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
480 fn check_semver(cx: &LateContext<'_>, span: Span, lit: &Lit) {
481 if let LitKind::Str(is, _) = lit.kind {
482 if Version::parse(&is.as_str()).is_ok() {
490 "the since field must contain a semver-compliant version",
494 fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool {
495 if let NestedMetaItem::MetaItem(mi) = &nmi {
496 mi.is_word() && mi.has_name(expected)
502 pub struct EarlyAttributes {
503 pub msrv: Option<RustcVersion>,
506 impl_lint_pass!(EarlyAttributes => [
508 MISMATCHED_TARGET_OS,
509 EMPTY_LINE_AFTER_OUTER_ATTR,
512 impl EarlyLintPass for EarlyAttributes {
513 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
514 check_empty_line_after_outer_attr(cx, item);
517 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
518 check_deprecated_cfg_attr(cx, attr, self.msrv);
519 check_mismatched_target_os(cx, attr);
522 extract_msrv_attr!(EarlyContext);
525 fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
526 for attr in &item.attrs {
527 let attr_item = if let AttrKind::Normal(ref attr, _) = attr.kind {
533 if attr.style == AttrStyle::Outer {
534 if attr_item.args.inner_tokens().is_empty() || !is_present_in_source(cx, attr.span) {
538 let begin_of_attr_to_item = Span::new(attr.span.lo(), item.span.lo(), item.span.ctxt(), item.span.parent());
539 let end_of_attr_to_item = Span::new(attr.span.hi(), item.span.lo(), item.span.ctxt(), item.span.parent());
541 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) {
542 let lines = snippet.split('\n').collect::<Vec<_>>();
543 let lines = without_block_comments(lines);
545 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
548 EMPTY_LINE_AFTER_OUTER_ATTR,
549 begin_of_attr_to_item,
550 "found an empty line after an outer attribute. \
551 Perhaps you forgot to add a `!` to make it an inner attribute?",
559 fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute, msrv: Option<RustcVersion>) {
561 if meets_msrv(msrv.as_ref(), &msrvs::TOOL_ATTRIBUTES);
563 if attr.has_name(sym::cfg_attr);
564 if let Some(items) = attr.meta_item_list();
566 // check for `rustfmt`
567 if let Some(feature_item) = items[0].meta_item();
568 if feature_item.has_name(sym::rustfmt);
569 // check for `rustfmt_skip` and `rustfmt::skip`
570 if let Some(skip_item) = &items[1].meta_item();
571 if skip_item.has_name(sym!(rustfmt_skip)) ||
572 skip_item.path.segments.last().expect("empty path in attribute").ident.name == sym::skip;
573 // Only lint outer attributes, because custom inner attributes are unstable
574 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
575 if attr.style == AttrStyle::Outer;
581 "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
583 "#[rustfmt::skip]".to_string(),
584 Applicability::MachineApplicable,
590 fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
591 fn find_os(name: &str) -> Option<&'static str> {
594 .chain(NON_UNIX_SYSTEMS.iter())
595 .find(|&&os| os == name)
599 fn is_unix(name: &str) -> bool {
600 UNIX_SYSTEMS.iter().any(|&os| os == name)
603 fn find_mismatched_target_os(items: &[NestedMetaItem]) -> Vec<(&str, Span)> {
604 let mut mismatched = Vec::new();
607 if let NestedMetaItem::MetaItem(meta) = item {
609 MetaItemKind::List(list) => {
610 mismatched.extend(find_mismatched_target_os(list));
612 MetaItemKind::Word => {
614 if let Some(ident) = meta.ident();
615 if let Some(os) = find_os(&*ident.name.as_str());
617 mismatched.push((os, ident.span));
621 MetaItemKind::NameValue(..) => {},
630 if attr.has_name(sym::cfg);
631 if let Some(list) = attr.meta_item_list();
632 let mismatched = find_mismatched_target_os(&list);
633 if !mismatched.is_empty();
635 let mess = "operating system used in target family position";
637 span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, mess, |diag| {
638 // Avoid showing the unix suggestion multiple times in case
639 // we have more than one mismatch for unix-like systems
640 let mut unix_suggested = false;
642 for (os, span) in mismatched {
643 let sugg = format!("target_os = \"{}\"", os);
644 diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
646 if !unix_suggested && is_unix(os) {
647 diag.help("did you mean `unix`?");
648 unix_suggested = true;
656 fn is_lint_level(symbol: Symbol) -> bool {
657 matches!(symbol, sym::allow | sym::warn | sym::deny | sym::forbid)