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.
93 /// #[deny(dead_code)]
95 /// #[forbid(dead_code)]
99 /// #[allow(unused_imports)]
101 /// #[allow(unused_imports)]
103 /// extern crate baz;
105 #[clippy::version = "pre 1.29.0"]
106 pub USELESS_ATTRIBUTE,
108 "use of lint attributes on `extern crate` items"
111 declare_clippy_lint! {
113 /// Checks for `#[deprecated]` annotations with a `since`
114 /// field that is not a valid semantic version.
116 /// ### Why is this bad?
117 /// For checking the version of the deprecation, it must be
118 /// a valid semver. Failing that, the contained information is useless.
122 /// #[deprecated(since = "forever")]
123 /// fn something_else() { /* ... */ }
125 #[clippy::version = "pre 1.29.0"]
126 pub DEPRECATED_SEMVER,
128 "use of `#[deprecated(since = \"x\")]` where x is not semver"
131 declare_clippy_lint! {
133 /// Checks for empty lines after outer attributes
135 /// ### Why is this bad?
136 /// Most likely the attribute was meant to be an inner attribute using a '!'.
137 /// If it was meant to be an outer attribute, then the following item
138 /// should not be separated by empty lines.
140 /// ### Known problems
141 /// Can cause false positives.
143 /// From the clippy side it's difficult to detect empty lines between an attributes and the
144 /// following item because empty lines and comments are not part of the AST. The parsing
145 /// currently works for basic cases but is not perfect.
149 /// // Good (as inner attribute)
150 /// #![allow(dead_code)]
152 /// fn this_is_fine() { }
155 /// #[allow(dead_code)]
157 /// fn not_quite_good_code() { }
159 /// // Good (as outer attribute)
160 /// #[allow(dead_code)]
161 /// fn this_is_fine_too() { }
163 #[clippy::version = "pre 1.29.0"]
164 pub EMPTY_LINE_AFTER_OUTER_ATTR,
166 "empty line after outer attribute"
169 declare_clippy_lint! {
171 /// Checks for `warn`/`deny`/`forbid` attributes targeting the whole clippy::restriction category.
173 /// ### Why is this bad?
174 /// Restriction lints sometimes are in contrast with other lints or even go against idiomatic rust.
175 /// These lints should only be enabled on a lint-by-lint basis and with careful consideration.
180 /// #![deny(clippy::restriction)]
185 /// #![deny(clippy::as_conversions)]
187 #[clippy::version = "1.47.0"]
188 pub BLANKET_CLIPPY_RESTRICTION_LINTS,
190 "enabling the complete restriction group"
193 declare_clippy_lint! {
195 /// Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
196 /// with `#[rustfmt::skip]`.
198 /// ### Why is this bad?
199 /// Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
200 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
202 /// ### Known problems
203 /// This lint doesn't detect crate level inner attributes, because they get
204 /// processed before the PreExpansionPass lints get executed. See
205 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
210 /// #[cfg_attr(rustfmt, rustfmt_skip)]
219 #[clippy::version = "1.32.0"]
220 pub DEPRECATED_CFG_ATTR,
222 "usage of `cfg_attr(rustfmt)` instead of tool attributes"
225 declare_clippy_lint! {
227 /// Checks for cfg attributes having operating systems used in target family position.
229 /// ### Why is this bad?
230 /// The configuration option will not be recognised and the related item will not be included
231 /// by the conditional compilation engine.
237 /// fn conditional() { }
242 /// #[cfg(target_os = "linux")]
243 /// fn conditional() { }
249 /// fn conditional() { }
251 /// Check the [Rust Reference](https://doc.rust-lang.org/reference/conditional-compilation.html#target_os) for more details.
252 #[clippy::version = "1.45.0"]
253 pub MISMATCHED_TARGET_OS,
255 "usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
258 declare_lint_pass!(Attributes => [
262 BLANKET_CLIPPY_RESTRICTION_LINTS,
265 impl<'tcx> LateLintPass<'tcx> for Attributes {
266 fn check_attribute(&mut self, cx: &LateContext<'tcx>, attr: &'tcx Attribute) {
267 if let Some(items) = &attr.meta_item_list() {
268 if let Some(ident) = attr.ident() {
269 if is_lint_level(ident.name) {
270 check_clippy_lint_names(cx, ident.name, items);
272 if items.is_empty() || !attr.has_name(sym::deprecated) {
277 if let NestedMetaItem::MetaItem(mi) = &item;
278 if let MetaItemKind::NameValue(lit) = &mi.kind;
279 if mi.has_name(sym::since);
281 check_semver(cx, item.span(), lit);
289 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
290 let attrs = cx.tcx.hir().attrs(item.hir_id());
291 if is_relevant_item(cx, item) {
292 check_attrs(cx, item.span, item.ident.name, attrs);
295 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
296 let skip_unused_imports = attrs.iter().any(|attr| attr.has_name(sym::macro_use));
299 if in_external_macro(cx.sess(), attr.span) {
302 if let Some(lint_list) = &attr.meta_item_list() {
303 if attr.ident().map_or(false, |ident| is_lint_level(ident.name)) {
304 // permit `unused_imports`, `deprecated`, `unreachable_pub`,
305 // `clippy::wildcard_imports`, and `clippy::enum_glob_use` for `use` items
306 // and `unused_imports` for `extern crate` items with `macro_use`
307 for lint in lint_list {
309 ItemKind::Use(..) => {
310 if is_word(lint, sym!(unused_imports))
311 || is_word(lint, sym::deprecated)
312 || is_word(lint, sym!(unreachable_pub))
313 || is_word(lint, sym!(unused))
314 || extract_clippy_lint(lint)
315 .map_or(false, |s| s.as_str() == "wildcard_imports")
316 || extract_clippy_lint(lint)
317 .map_or(false, |s| s.as_str() == "enum_glob_use")
322 ItemKind::ExternCrate(..) => {
323 if is_word(lint, sym!(unused_imports)) && skip_unused_imports {
326 if is_word(lint, sym!(unused_extern_crates)) {
333 let line_span = first_line_of_span(cx, attr.span);
335 if let Some(mut sugg) = snippet_opt(cx, line_span) {
336 if sugg.contains("#[") {
341 "useless lint attribute",
343 sugg = sugg.replacen("#[", "#![", 1);
344 diag.span_suggestion(
346 "if you just forgot a `!`, use",
348 Applicability::MaybeIncorrect,
362 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
363 if is_relevant_impl(cx, item) {
364 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
368 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
369 if is_relevant_trait(cx, item) {
370 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
375 /// Returns the lint name if it is clippy lint.
376 fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<Symbol> {
378 if let Some(meta_item) = lint.meta_item();
379 if meta_item.path.segments.len() > 1;
380 if let tool_name = meta_item.path.segments[0].ident;
381 if tool_name.name == sym::clippy;
383 let lint_name = meta_item.path.segments.last().unwrap().ident.name;
384 return Some(lint_name);
390 fn check_clippy_lint_names(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem]) {
392 if let Some(lint_name) = extract_clippy_lint(lint) {
393 if lint_name.as_str() == "restriction" && name != sym::allow {
396 BLANKET_CLIPPY_RESTRICTION_LINTS,
398 "restriction lints are not meant to be all enabled",
400 "try enabling only the lints you really need",
407 fn is_relevant_item(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
408 if let ItemKind::Fn(_, _, eid) = item.kind {
409 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
415 fn is_relevant_impl(cx: &LateContext<'_>, item: &ImplItem<'_>) -> bool {
417 ImplItemKind::Fn(_, eid) => is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value),
422 fn is_relevant_trait(cx: &LateContext<'_>, item: &TraitItem<'_>) -> bool {
424 TraitItemKind::Fn(_, TraitFn::Required(_)) => true,
425 TraitItemKind::Fn(_, TraitFn::Provided(eid)) => {
426 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
432 fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, block: &Block<'_>) -> bool {
433 block.stmts.first().map_or(
437 .map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
438 |stmt| match &stmt.kind {
439 StmtKind::Local(_) => true,
440 StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
441 StmtKind::Item(_) => false,
446 fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, expr: &Expr<'_>) -> bool {
447 if macro_backtrace(expr.span).last().map_or(false, |macro_call| {
448 is_panic(cx, macro_call.def_id) || cx.tcx.item_name(macro_call.def_id) == sym::unreachable
453 ExprKind::Block(block, _) => is_relevant_block(cx, typeck_results, block),
454 ExprKind::Ret(Some(e)) => is_relevant_expr(cx, typeck_results, e),
455 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
460 fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribute]) {
461 if span.from_expansion() {
466 if let Some(values) = attr.meta_item_list() {
467 if values.len() != 1 || !attr.has_name(sym::inline) {
470 if is_word(&values[0], sym::always) {
476 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
485 fn check_semver(cx: &LateContext<'_>, span: Span, lit: &Lit) {
486 if let LitKind::Str(is, _) = lit.kind {
487 if Version::parse(is.as_str()).is_ok() {
495 "the since field must contain a semver-compliant version",
499 fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool {
500 if let NestedMetaItem::MetaItem(mi) = &nmi {
501 mi.is_word() && mi.has_name(expected)
507 pub struct EarlyAttributes {
508 pub msrv: Option<RustcVersion>,
511 impl_lint_pass!(EarlyAttributes => [
513 MISMATCHED_TARGET_OS,
514 EMPTY_LINE_AFTER_OUTER_ATTR,
517 impl EarlyLintPass for EarlyAttributes {
518 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
519 check_empty_line_after_outer_attr(cx, item);
522 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
523 check_deprecated_cfg_attr(cx, attr, self.msrv);
524 check_mismatched_target_os(cx, attr);
527 extract_msrv_attr!(EarlyContext);
530 fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
531 for attr in &item.attrs {
532 let attr_item = if let AttrKind::Normal(ref attr, _) = attr.kind {
538 if attr.style == AttrStyle::Outer {
539 if attr_item.args.inner_tokens().is_empty() || !is_present_in_source(cx, attr.span) {
543 let begin_of_attr_to_item = Span::new(attr.span.lo(), item.span.lo(), item.span.ctxt(), item.span.parent());
544 let end_of_attr_to_item = Span::new(attr.span.hi(), item.span.lo(), item.span.ctxt(), item.span.parent());
546 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) {
547 let lines = snippet.split('\n').collect::<Vec<_>>();
548 let lines = without_block_comments(lines);
550 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
553 EMPTY_LINE_AFTER_OUTER_ATTR,
554 begin_of_attr_to_item,
555 "found an empty line after an outer attribute. \
556 Perhaps you forgot to add a `!` to make it an inner attribute?",
564 fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute, msrv: Option<RustcVersion>) {
566 if meets_msrv(msrv.as_ref(), &msrvs::TOOL_ATTRIBUTES);
568 if attr.has_name(sym::cfg_attr);
569 if let Some(items) = attr.meta_item_list();
571 // check for `rustfmt`
572 if let Some(feature_item) = items[0].meta_item();
573 if feature_item.has_name(sym::rustfmt);
574 // check for `rustfmt_skip` and `rustfmt::skip`
575 if let Some(skip_item) = &items[1].meta_item();
576 if skip_item.has_name(sym!(rustfmt_skip)) ||
577 skip_item.path.segments.last().expect("empty path in attribute").ident.name == sym::skip;
578 // Only lint outer attributes, because custom inner attributes are unstable
579 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
580 if attr.style == AttrStyle::Outer;
586 "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
588 "#[rustfmt::skip]".to_string(),
589 Applicability::MachineApplicable,
595 fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
596 fn find_os(name: &str) -> Option<&'static str> {
599 .chain(NON_UNIX_SYSTEMS.iter())
600 .find(|&&os| os == name)
604 fn is_unix(name: &str) -> bool {
605 UNIX_SYSTEMS.iter().any(|&os| os == name)
608 fn find_mismatched_target_os(items: &[NestedMetaItem]) -> Vec<(&str, Span)> {
609 let mut mismatched = Vec::new();
612 if let NestedMetaItem::MetaItem(meta) = item {
614 MetaItemKind::List(list) => {
615 mismatched.extend(find_mismatched_target_os(list));
617 MetaItemKind::Word => {
619 if let Some(ident) = meta.ident();
620 if let Some(os) = find_os(ident.name.as_str());
622 mismatched.push((os, ident.span));
626 MetaItemKind::NameValue(..) => {},
635 if attr.has_name(sym::cfg);
636 if let Some(list) = attr.meta_item_list();
637 let mismatched = find_mismatched_target_os(&list);
638 if !mismatched.is_empty();
640 let mess = "operating system used in target family position";
642 span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, mess, |diag| {
643 // Avoid showing the unix suggestion multiple times in case
644 // we have more than one mismatch for unix-like systems
645 let mut unix_suggested = false;
647 for (os, span) in mismatched {
648 let sugg = format!("target_os = \"{}\"", os);
649 diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
651 if !unix_suggested && is_unix(os) {
652 diag.help("did you mean `unix`?");
653 unix_suggested = true;
661 fn is_lint_level(symbol: Symbol) -> bool {
662 matches!(symbol, sym::allow | sym::warn | sym::deny | sym::forbid)