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::macros::{is_panic, macro_backtrace};
5 use clippy_utils::msrvs;
6 use clippy_utils::source::{first_line_of_span, is_present_in_source, snippet_opt, without_block_comments};
7 use clippy_utils::{extract_msrv_attr, meets_msrv};
8 use if_chain::if_chain;
9 use rustc_ast::{AttrKind, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
10 use rustc_errors::Applicability;
12 Block, Expr, ExprKind, ImplItem, ImplItemKind, Item, ItemKind, StmtKind, TraitFn, TraitItem, TraitItemKind,
14 use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
15 use rustc_middle::lint::in_external_macro;
17 use rustc_semver::RustcVersion;
18 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
19 use rustc_span::source_map::Span;
21 use rustc_span::symbol::Symbol;
24 static UNIX_SYSTEMS: &[&str] = &[
43 // NOTE: windows is excluded from the list because it's also a valid target family.
44 static NON_UNIX_SYSTEMS: &[&str] = &["hermit", "none", "wasi"];
46 declare_clippy_lint! {
48 /// Checks for items annotated with `#[inline(always)]`,
49 /// unless the annotated function is empty or simply panics.
51 /// ### Why is this bad?
52 /// While there are valid uses of this annotation (and once
53 /// you know when to use it, by all means `allow` this lint), it's a common
54 /// newbie-mistake to pepper one's code with it.
56 /// As a rule of thumb, before slapping `#[inline(always)]` on a function,
57 /// measure if that additional function call really affects your runtime profile
58 /// sufficiently to make up for the increase in compile time.
60 /// ### Known problems
61 /// False positives, big time. This lint is meant to be
62 /// deactivated by everyone doing serious performance work. This means having
63 /// done the measurement.
68 /// fn not_quite_hot_code(..) { ... }
70 #[clippy::version = "pre 1.29.0"]
73 "use of `#[inline(always)]`"
76 declare_clippy_lint! {
78 /// Checks for `extern crate` and `use` items annotated with
81 /// This lint permits `#[allow(unused_imports)]`, `#[allow(deprecated)]`,
82 /// `#[allow(unreachable_pub)]`, `#[allow(clippy::wildcard_imports)]` and
83 /// `#[allow(clippy::enum_glob_use)]` on `use` items and `#[allow(unused_imports)]` on
84 /// `extern crate` items with a `#[macro_use]` attribute.
86 /// ### Why is this bad?
87 /// Lint attributes have no effect on crate imports. Most
88 /// likely a `!` was forgotten.
92 /// #[deny(dead_code)]
94 /// #[forbid(dead_code)]
100 /// #[allow(unused_imports)]
102 /// #[allow(unused_imports)]
104 /// extern crate baz;
106 #[clippy::version = "pre 1.29.0"]
107 pub USELESS_ATTRIBUTE,
109 "use of lint attributes on `extern crate` items"
112 declare_clippy_lint! {
114 /// Checks for `#[deprecated]` annotations with a `since`
115 /// field that is not a valid semantic version.
117 /// ### Why is this bad?
118 /// For checking the version of the deprecation, it must be
119 /// a valid semver. Failing that, the contained information is useless.
123 /// #[deprecated(since = "forever")]
124 /// fn something_else() { /* ... */ }
126 #[clippy::version = "pre 1.29.0"]
127 pub DEPRECATED_SEMVER,
129 "use of `#[deprecated(since = \"x\")]` where x is not semver"
132 declare_clippy_lint! {
134 /// Checks for empty lines after outer attributes
136 /// ### Why is this bad?
137 /// Most likely the attribute was meant to be an inner attribute using a '!'.
138 /// If it was meant to be an outer attribute, then the following item
139 /// should not be separated by empty lines.
141 /// ### Known problems
142 /// Can cause false positives.
144 /// From the clippy side it's difficult to detect empty lines between an attributes and the
145 /// following item because empty lines and comments are not part of the AST. The parsing
146 /// currently works for basic cases but is not perfect.
150 /// #[allow(dead_code)]
152 /// fn not_quite_good_code() { }
157 /// // Good (as inner attribute)
158 /// #![allow(dead_code)]
160 /// fn this_is_fine() { }
164 /// // Good (as outer attribute)
165 /// #[allow(dead_code)]
166 /// fn this_is_fine_too() { }
168 #[clippy::version = "pre 1.29.0"]
169 pub EMPTY_LINE_AFTER_OUTER_ATTR,
171 "empty line after outer attribute"
174 declare_clippy_lint! {
176 /// Checks for `warn`/`deny`/`forbid` attributes targeting the whole clippy::restriction category.
178 /// ### Why is this bad?
179 /// Restriction lints sometimes are in contrast with other lints or even go against idiomatic rust.
180 /// These lints should only be enabled on a lint-by-lint basis and with careful consideration.
184 /// #![deny(clippy::restriction)]
189 /// #![deny(clippy::as_conversions)]
191 #[clippy::version = "1.47.0"]
192 pub BLANKET_CLIPPY_RESTRICTION_LINTS,
194 "enabling the complete restriction group"
197 declare_clippy_lint! {
199 /// Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
200 /// with `#[rustfmt::skip]`.
202 /// ### Why is this bad?
203 /// Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
204 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
206 /// ### Known problems
207 /// This lint doesn't detect crate level inner attributes, because they get
208 /// processed before the PreExpansionPass lints get executed. See
209 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
213 /// #[cfg_attr(rustfmt, rustfmt_skip)]
222 #[clippy::version = "1.32.0"]
223 pub DEPRECATED_CFG_ATTR,
225 "usage of `cfg_attr(rustfmt)` instead of tool attributes"
228 declare_clippy_lint! {
230 /// Checks for cfg attributes having operating systems used in target family position.
232 /// ### Why is this bad?
233 /// The configuration option will not be recognised and the related item will not be included
234 /// by the conditional compilation engine.
239 /// fn conditional() { }
245 /// #[cfg(target_os = "linux")]
246 /// fn conditional() { }
252 /// fn conditional() { }
254 /// Check the [Rust Reference](https://doc.rust-lang.org/reference/conditional-compilation.html#target_os) for more details.
255 #[clippy::version = "1.45.0"]
256 pub MISMATCHED_TARGET_OS,
258 "usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
261 declare_clippy_lint! {
263 /// Checks for attributes that allow lints without a reason.
265 /// (This requires the `lint_reasons` feature)
267 /// ### Why is this bad?
268 /// Allowing a lint should always have a reason. This reason should be documented to
269 /// ensure that others understand the reasoning
273 /// #![feature(lint_reasons)]
275 /// #![allow(clippy::some_lint)]
280 /// #![feature(lint_reasons)]
282 /// #![allow(clippy::some_lint, reason = "False positive rust-lang/rust-clippy#1002020")]
284 #[clippy::version = "1.61.0"]
285 pub ALLOW_ATTRIBUTES_WITHOUT_REASON,
287 "ensures that all `allow` and `expect` attributes have a reason"
290 declare_lint_pass!(Attributes => [
291 ALLOW_ATTRIBUTES_WITHOUT_REASON,
295 BLANKET_CLIPPY_RESTRICTION_LINTS,
298 impl<'tcx> LateLintPass<'tcx> for Attributes {
299 fn check_attribute(&mut self, cx: &LateContext<'tcx>, attr: &'tcx Attribute) {
300 if let Some(items) = &attr.meta_item_list() {
301 if let Some(ident) = attr.ident() {
302 if is_lint_level(ident.name) {
303 check_clippy_lint_names(cx, ident.name, items);
305 if matches!(ident.name, sym::allow | sym::expect) {
306 check_lint_reason(cx, ident.name, items, attr);
308 if items.is_empty() || !attr.has_name(sym::deprecated) {
313 if let NestedMetaItem::MetaItem(mi) = &item;
314 if let MetaItemKind::NameValue(lit) = &mi.kind;
315 if mi.has_name(sym::since);
317 check_semver(cx, item.span(), lit);
325 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
326 let attrs = cx.tcx.hir().attrs(item.hir_id());
327 if is_relevant_item(cx, item) {
328 check_attrs(cx, item.span, item.ident.name, attrs);
331 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
332 let skip_unused_imports = attrs.iter().any(|attr| attr.has_name(sym::macro_use));
335 if in_external_macro(cx.sess(), attr.span) {
338 if let Some(lint_list) = &attr.meta_item_list() {
339 if attr.ident().map_or(false, |ident| is_lint_level(ident.name)) {
340 for lint in lint_list {
342 ItemKind::Use(..) => {
343 if is_word(lint, sym!(unused_imports))
344 || is_word(lint, sym::deprecated)
345 || is_word(lint, sym!(unreachable_pub))
346 || is_word(lint, sym!(unused))
347 || extract_clippy_lint(lint).map_or(false, |s| {
350 "wildcard_imports" | "enum_glob_use" | "redundant_pub_crate",
357 ItemKind::ExternCrate(..) => {
358 if is_word(lint, sym!(unused_imports)) && skip_unused_imports {
361 if is_word(lint, sym!(unused_extern_crates)) {
368 let line_span = first_line_of_span(cx, attr.span);
370 if let Some(mut sugg) = snippet_opt(cx, line_span) {
371 if sugg.contains("#[") {
376 "useless lint attribute",
378 sugg = sugg.replacen("#[", "#![", 1);
379 diag.span_suggestion(
381 "if you just forgot a `!`, use",
383 Applicability::MaybeIncorrect,
397 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
398 if is_relevant_impl(cx, item) {
399 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
403 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
404 if is_relevant_trait(cx, item) {
405 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
410 /// Returns the lint name if it is clippy lint.
411 fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<Symbol> {
413 if let Some(meta_item) = lint.meta_item();
414 if meta_item.path.segments.len() > 1;
415 if let tool_name = meta_item.path.segments[0].ident;
416 if tool_name.name == sym::clippy;
418 let lint_name = meta_item.path.segments.last().unwrap().ident.name;
419 return Some(lint_name);
425 fn check_clippy_lint_names(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem]) {
427 if let Some(lint_name) = extract_clippy_lint(lint) {
428 if lint_name.as_str() == "restriction" && name != sym::allow {
431 BLANKET_CLIPPY_RESTRICTION_LINTS,
433 "restriction lints are not meant to be all enabled",
435 "try enabling only the lints you really need",
442 fn check_lint_reason(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem], attr: &'_ Attribute) {
443 // Check for the feature
444 if !cx.tcx.sess.features_untracked().lint_reasons {
448 // Check if the reason is present
449 if let Some(item) = items.last().and_then(NestedMetaItem::meta_item)
450 && let MetaItemKind::NameValue(_) = &item.kind
451 && item.path == sym::reason
458 ALLOW_ATTRIBUTES_WITHOUT_REASON,
460 &format!("`{}` attribute without specifying a reason", name.as_str()),
462 "try adding a reason at the end with `, reason = \"..\"`",
466 fn is_relevant_item(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
467 if let ItemKind::Fn(_, _, eid) = item.kind {
468 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
474 fn is_relevant_impl(cx: &LateContext<'_>, item: &ImplItem<'_>) -> bool {
476 ImplItemKind::Fn(_, eid) => is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value),
481 fn is_relevant_trait(cx: &LateContext<'_>, item: &TraitItem<'_>) -> bool {
483 TraitItemKind::Fn(_, TraitFn::Required(_)) => true,
484 TraitItemKind::Fn(_, TraitFn::Provided(eid)) => {
485 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
491 fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, block: &Block<'_>) -> bool {
492 block.stmts.first().map_or(
496 .map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
497 |stmt| match &stmt.kind {
498 StmtKind::Local(_) => true,
499 StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
500 StmtKind::Item(_) => false,
505 fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, expr: &Expr<'_>) -> bool {
506 if macro_backtrace(expr.span).last().map_or(false, |macro_call| {
507 is_panic(cx, macro_call.def_id) || cx.tcx.item_name(macro_call.def_id) == sym::unreachable
512 ExprKind::Block(block, _) => is_relevant_block(cx, typeck_results, block),
513 ExprKind::Ret(Some(e)) => is_relevant_expr(cx, typeck_results, e),
514 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
519 fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribute]) {
520 if span.from_expansion() {
525 if let Some(values) = attr.meta_item_list() {
526 if values.len() != 1 || !attr.has_name(sym::inline) {
529 if is_word(&values[0], sym::always) {
535 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
544 fn check_semver(cx: &LateContext<'_>, span: Span, lit: &Lit) {
545 if let LitKind::Str(is, _) = lit.kind {
546 if Version::parse(is.as_str()).is_ok() {
554 "the since field must contain a semver-compliant version",
558 fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool {
559 if let NestedMetaItem::MetaItem(mi) = &nmi {
560 mi.is_word() && mi.has_name(expected)
566 pub struct EarlyAttributes {
567 pub msrv: Option<RustcVersion>,
570 impl_lint_pass!(EarlyAttributes => [
572 MISMATCHED_TARGET_OS,
573 EMPTY_LINE_AFTER_OUTER_ATTR,
576 impl EarlyLintPass for EarlyAttributes {
577 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
578 check_empty_line_after_outer_attr(cx, item);
581 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
582 check_deprecated_cfg_attr(cx, attr, self.msrv);
583 check_mismatched_target_os(cx, attr);
586 extract_msrv_attr!(EarlyContext);
589 fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
590 let mut iter = item.attrs.iter().peekable();
591 while let Some(attr) = iter.next() {
592 if matches!(attr.kind, AttrKind::Normal(..))
593 && attr.style == AttrStyle::Outer
594 && is_present_in_source(cx, attr.span)
596 let begin_of_attr_to_item = Span::new(attr.span.lo(), item.span.lo(), item.span.ctxt(), item.span.parent());
597 let end_of_attr_to_next_attr_or_item = Span::new(
599 iter.peek().map_or(item.span.lo(), |next_attr| next_attr.span.lo()),
604 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_next_attr_or_item) {
605 let lines = snippet.split('\n').collect::<Vec<_>>();
606 let lines = without_block_comments(lines);
608 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
611 EMPTY_LINE_AFTER_OUTER_ATTR,
612 begin_of_attr_to_item,
613 "found an empty line after an outer attribute. \
614 Perhaps you forgot to add a `!` to make it an inner attribute?",
622 fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute, msrv: Option<RustcVersion>) {
624 if meets_msrv(msrv, msrvs::TOOL_ATTRIBUTES);
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))
639 .expect("empty path in attribute")
643 // Only lint outer attributes, because custom inner attributes are unstable
644 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
645 if attr.style == AttrStyle::Outer;
651 "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
653 "#[rustfmt::skip]".to_string(),
654 Applicability::MachineApplicable,
660 fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
661 fn find_os(name: &str) -> Option<&'static str> {
664 .chain(NON_UNIX_SYSTEMS.iter())
665 .find(|&&os| os == name)
669 fn is_unix(name: &str) -> bool {
670 UNIX_SYSTEMS.iter().any(|&os| os == name)
673 fn find_mismatched_target_os(items: &[NestedMetaItem]) -> Vec<(&str, Span)> {
674 let mut mismatched = Vec::new();
677 if let NestedMetaItem::MetaItem(meta) = item {
679 MetaItemKind::List(list) => {
680 mismatched.extend(find_mismatched_target_os(list));
682 MetaItemKind::Word => {
684 if let Some(ident) = meta.ident();
685 if let Some(os) = find_os(ident.name.as_str());
687 mismatched.push((os, ident.span));
691 MetaItemKind::NameValue(..) => {},
700 if attr.has_name(sym::cfg);
701 if let Some(list) = attr.meta_item_list();
702 let mismatched = find_mismatched_target_os(&list);
703 if !mismatched.is_empty();
705 let mess = "operating system used in target family position";
707 span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, mess, |diag| {
708 // Avoid showing the unix suggestion multiple times in case
709 // we have more than one mismatch for unix-like systems
710 let mut unix_suggested = false;
712 for (os, span) in mismatched {
713 let sugg = format!("target_os = \"{}\"", os);
714 diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
716 if !unix_suggested && is_unix(os) {
717 diag.help("did you mean `unix`?");
718 unix_suggested = true;
726 fn is_lint_level(symbol: Symbol) -> bool {
727 matches!(symbol, sym::allow | sym::expect | sym::warn | sym::deny | sym::forbid)