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::match_panic_def_id;
5 use clippy_utils::source::{first_line_of_span, is_present_in_source, snippet_opt, without_block_comments};
6 use if_chain::if_chain;
7 use rustc_ast::{AttrKind, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
8 use rustc_errors::Applicability;
10 Block, Expr, ExprKind, ImplItem, ImplItemKind, Item, ItemKind, StmtKind, TraitFn, TraitItem, TraitItemKind,
12 use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
13 use rustc_middle::lint::in_external_macro;
15 use rustc_session::{declare_lint_pass, declare_tool_lint};
16 use rustc_span::source_map::Span;
18 use rustc_span::symbol::{Symbol, SymbolStr};
21 static UNIX_SYSTEMS: &[&str] = &[
40 // NOTE: windows is excluded from the list because it's also a valid target family.
41 static NON_UNIX_SYSTEMS: &[&str] = &["hermit", "none", "wasi"];
43 declare_clippy_lint! {
45 /// Checks for items annotated with `#[inline(always)]`,
46 /// unless the annotated function is empty or simply panics.
48 /// ### Why is this bad?
49 /// 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
58 /// False positives, big time. This lint is meant to be
59 /// deactivated by everyone doing serious performance work. This means having
60 /// done the measurement.
65 /// fn not_quite_hot_code(..) { ... }
69 "use of `#[inline(always)]`"
72 declare_clippy_lint! {
74 /// Checks for `extern crate` and `use` items annotated with
77 /// This lint permits `#[allow(unused_imports)]`, `#[allow(deprecated)]`,
78 /// `#[allow(unreachable_pub)]`, `#[allow(clippy::wildcard_imports)]` and
79 /// `#[allow(clippy::enum_glob_use)]` on `use` items and `#[allow(unused_imports)]` on
80 /// `extern crate` items with a `#[macro_use]` attribute.
82 /// ### Why is this bad?
83 /// Lint attributes have no effect on crate imports. Most
84 /// likely a `!` was forgotten.
89 /// #[deny(dead_code)]
91 /// #[forbid(dead_code)]
95 /// #[allow(unused_imports)]
97 /// #[allow(unused_imports)]
101 pub USELESS_ATTRIBUTE,
103 "use of lint attributes on `extern crate` items"
106 declare_clippy_lint! {
108 /// Checks for `#[deprecated]` annotations with a `since`
109 /// field that is not a valid semantic version.
111 /// ### Why is this bad?
112 /// For checking the version of the deprecation, it must be
113 /// a valid semver. Failing that, the contained information is useless.
117 /// #[deprecated(since = "forever")]
118 /// fn something_else() { /* ... */ }
120 pub DEPRECATED_SEMVER,
122 "use of `#[deprecated(since = \"x\")]` where x is not semver"
125 declare_clippy_lint! {
127 /// Checks for empty lines after outer attributes
129 /// ### Why is this bad?
130 /// Most likely the attribute was meant to be an inner attribute using a '!'.
131 /// If it was meant to be an outer attribute, then the following item
132 /// should not be separated by empty lines.
134 /// ### Known problems
135 /// Can cause false positives.
137 /// From the clippy side it's difficult to detect empty lines between an attributes and the
138 /// following item because empty lines and comments are not part of the AST. The parsing
139 /// currently works for basic cases but is not perfect.
143 /// // Good (as inner attribute)
144 /// #![allow(dead_code)]
146 /// fn this_is_fine() { }
149 /// #[allow(dead_code)]
151 /// fn not_quite_good_code() { }
153 /// // Good (as outer attribute)
154 /// #[allow(dead_code)]
155 /// fn this_is_fine_too() { }
157 pub EMPTY_LINE_AFTER_OUTER_ATTR,
159 "empty line after outer attribute"
162 declare_clippy_lint! {
164 /// Checks for `warn`/`deny`/`forbid` attributes targeting the whole clippy::restriction category.
166 /// ### Why is this bad?
167 /// Restriction lints sometimes are in contrast with other lints or even go against idiomatic rust.
168 /// These lints should only be enabled on a lint-by-lint basis and with careful consideration.
173 /// #![deny(clippy::restriction)]
178 /// #![deny(clippy::as_conversions)]
180 pub BLANKET_CLIPPY_RESTRICTION_LINTS,
182 "enabling the complete restriction group"
185 declare_clippy_lint! {
187 /// Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
188 /// with `#[rustfmt::skip]`.
190 /// ### Why is this bad?
191 /// Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
192 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
194 /// ### Known problems
195 /// This lint doesn't detect crate level inner attributes, because they get
196 /// processed before the PreExpansionPass lints get executed. See
197 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
202 /// #[cfg_attr(rustfmt, rustfmt_skip)]
211 pub DEPRECATED_CFG_ATTR,
213 "usage of `cfg_attr(rustfmt)` instead of tool attributes"
216 declare_clippy_lint! {
218 /// Checks for cfg attributes having operating systems used in target family position.
220 /// ### Why is this bad?
221 /// The configuration option will not be recognised and the related item will not be included
222 /// by the conditional compilation engine.
228 /// fn conditional() { }
233 /// #[cfg(target_os = "linux")]
234 /// fn conditional() { }
240 /// fn conditional() { }
242 /// Check the [Rust Reference](https://doc.rust-lang.org/reference/conditional-compilation.html#target_os) for more details.
243 pub MISMATCHED_TARGET_OS,
245 "usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
248 declare_lint_pass!(Attributes => [
252 BLANKET_CLIPPY_RESTRICTION_LINTS,
255 impl<'tcx> LateLintPass<'tcx> for Attributes {
256 fn check_attribute(&mut self, cx: &LateContext<'tcx>, attr: &'tcx Attribute) {
257 if let Some(items) = &attr.meta_item_list() {
258 if let Some(ident) = attr.ident() {
259 if is_lint_level(ident.name) {
260 check_clippy_lint_names(cx, ident.name, items);
262 if items.is_empty() || !attr.has_name(sym::deprecated) {
267 if let NestedMetaItem::MetaItem(mi) = &item;
268 if let MetaItemKind::NameValue(lit) = &mi.kind;
269 if mi.has_name(sym::since);
271 check_semver(cx, item.span(), lit);
279 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
280 let attrs = cx.tcx.hir().attrs(item.hir_id());
281 if is_relevant_item(cx, item) {
282 check_attrs(cx, item.span, item.ident.name, attrs);
285 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
286 let skip_unused_imports = attrs.iter().any(|attr| attr.has_name(sym::macro_use));
289 if in_external_macro(cx.sess(), attr.span) {
292 if let Some(lint_list) = &attr.meta_item_list() {
293 if attr.ident().map_or(false, |ident| is_lint_level(ident.name)) {
294 // permit `unused_imports`, `deprecated`, `unreachable_pub`,
295 // `clippy::wildcard_imports`, and `clippy::enum_glob_use` for `use` items
296 // and `unused_imports` for `extern crate` items with `macro_use`
297 for lint in lint_list {
299 ItemKind::Use(..) => {
300 if is_word(lint, sym!(unused_imports))
301 || is_word(lint, sym::deprecated)
302 || is_word(lint, sym!(unreachable_pub))
303 || is_word(lint, sym!(unused))
304 || extract_clippy_lint(lint).map_or(false, |s| s == "wildcard_imports")
305 || extract_clippy_lint(lint).map_or(false, |s| s == "enum_glob_use")
310 ItemKind::ExternCrate(..) => {
311 if is_word(lint, sym!(unused_imports)) && skip_unused_imports {
314 if is_word(lint, sym!(unused_extern_crates)) {
321 let line_span = first_line_of_span(cx, attr.span);
323 if let Some(mut sugg) = snippet_opt(cx, line_span) {
324 if sugg.contains("#[") {
329 "useless lint attribute",
331 sugg = sugg.replacen("#[", "#![", 1);
332 diag.span_suggestion(
334 "if you just forgot a `!`, use",
336 Applicability::MaybeIncorrect,
350 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
351 if is_relevant_impl(cx, item) {
352 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
356 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
357 if is_relevant_trait(cx, item) {
358 check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
363 /// Returns the lint name if it is clippy lint.
364 fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<SymbolStr> {
366 if let Some(meta_item) = lint.meta_item();
367 if meta_item.path.segments.len() > 1;
368 if let tool_name = meta_item.path.segments[0].ident;
369 if tool_name.name == sym::clippy;
371 let lint_name = meta_item.path.segments.last().unwrap().ident.name;
372 return Some(lint_name.as_str());
378 fn check_clippy_lint_names(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem]) {
380 if let Some(lint_name) = extract_clippy_lint(lint) {
381 if lint_name == "restriction" && name != sym::allow {
384 BLANKET_CLIPPY_RESTRICTION_LINTS,
386 "restriction lints are not meant to be all enabled",
388 "try enabling only the lints you really need",
395 fn is_relevant_item(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
396 if let ItemKind::Fn(_, _, eid) = item.kind {
397 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
403 fn is_relevant_impl(cx: &LateContext<'_>, item: &ImplItem<'_>) -> bool {
405 ImplItemKind::Fn(_, eid) => is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value),
410 fn is_relevant_trait(cx: &LateContext<'_>, item: &TraitItem<'_>) -> bool {
412 TraitItemKind::Fn(_, TraitFn::Required(_)) => true,
413 TraitItemKind::Fn(_, TraitFn::Provided(eid)) => {
414 is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
420 fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, block: &Block<'_>) -> bool {
421 block.stmts.first().map_or(
425 .map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
426 |stmt| match &stmt.kind {
427 StmtKind::Local(_) => true,
428 StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
429 StmtKind::Item(_) => false,
434 fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, expr: &Expr<'_>) -> bool {
436 ExprKind::Block(block, _) => is_relevant_block(cx, typeck_results, block),
437 ExprKind::Ret(Some(e)) => is_relevant_expr(cx, typeck_results, e),
438 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
439 ExprKind::Call(path_expr, _) => {
440 if let ExprKind::Path(qpath) = &path_expr.kind {
442 .qpath_res(qpath, path_expr.hir_id)
444 .map_or(true, |fun_id| !match_panic_def_id(cx, fun_id))
453 fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribute]) {
454 if span.from_expansion() {
459 if let Some(values) = attr.meta_item_list() {
460 if values.len() != 1 || !attr.has_name(sym::inline) {
463 if is_word(&values[0], sym::always) {
469 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
478 fn check_semver(cx: &LateContext<'_>, span: Span, lit: &Lit) {
479 if let LitKind::Str(is, _) = lit.kind {
480 if Version::parse(&is.as_str()).is_ok() {
488 "the since field must contain a semver-compliant version",
492 fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool {
493 if let NestedMetaItem::MetaItem(mi) = &nmi {
494 mi.is_word() && mi.has_name(expected)
500 declare_lint_pass!(EarlyAttributes => [
502 MISMATCHED_TARGET_OS,
503 EMPTY_LINE_AFTER_OUTER_ATTR,
506 impl EarlyLintPass for EarlyAttributes {
507 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
508 check_empty_line_after_outer_attr(cx, item);
511 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
512 check_deprecated_cfg_attr(cx, attr);
513 check_mismatched_target_os(cx, attr);
517 fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
518 for attr in &item.attrs {
519 let attr_item = if let AttrKind::Normal(ref attr, _) = attr.kind {
525 if attr.style == AttrStyle::Outer {
526 if attr_item.args.inner_tokens().is_empty() || !is_present_in_source(cx, attr.span) {
530 let begin_of_attr_to_item = Span::new(attr.span.lo(), item.span.lo(), item.span.ctxt(), item.span.parent());
531 let end_of_attr_to_item = Span::new(attr.span.hi(), item.span.lo(), item.span.ctxt(), item.span.parent());
533 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) {
534 let lines = snippet.split('\n').collect::<Vec<_>>();
535 let lines = without_block_comments(lines);
537 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
540 EMPTY_LINE_AFTER_OUTER_ATTR,
541 begin_of_attr_to_item,
542 "found an empty line after an outer attribute. \
543 Perhaps you forgot to add a `!` to make it an inner attribute?",
551 fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute) {
554 if attr.has_name(sym::cfg_attr);
555 if let Some(items) = attr.meta_item_list();
557 // check for `rustfmt`
558 if let Some(feature_item) = items[0].meta_item();
559 if feature_item.has_name(sym::rustfmt);
560 // check for `rustfmt_skip` and `rustfmt::skip`
561 if let Some(skip_item) = &items[1].meta_item();
562 if skip_item.has_name(sym!(rustfmt_skip)) ||
563 skip_item.path.segments.last().expect("empty path in attribute").ident.name == sym::skip;
564 // Only lint outer attributes, because custom inner attributes are unstable
565 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
566 if let AttrStyle::Outer = attr.style;
572 "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
574 "#[rustfmt::skip]".to_string(),
575 Applicability::MachineApplicable,
581 fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
582 fn find_os(name: &str) -> Option<&'static str> {
585 .chain(NON_UNIX_SYSTEMS.iter())
586 .find(|&&os| os == name)
590 fn is_unix(name: &str) -> bool {
591 UNIX_SYSTEMS.iter().any(|&os| os == name)
594 fn find_mismatched_target_os(items: &[NestedMetaItem]) -> Vec<(&str, Span)> {
595 let mut mismatched = Vec::new();
598 if let NestedMetaItem::MetaItem(meta) = item {
600 MetaItemKind::List(list) => {
601 mismatched.extend(find_mismatched_target_os(list));
603 MetaItemKind::Word => {
605 if let Some(ident) = meta.ident();
606 if let Some(os) = find_os(&*ident.name.as_str());
608 mismatched.push((os, ident.span));
612 MetaItemKind::NameValue(..) => {},
621 if attr.has_name(sym::cfg);
622 if let Some(list) = attr.meta_item_list();
623 let mismatched = find_mismatched_target_os(&list);
624 if !mismatched.is_empty();
626 let mess = "operating system used in target family position";
628 span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, mess, |diag| {
629 // Avoid showing the unix suggestion multiple times in case
630 // we have more than one mismatch for unix-like systems
631 let mut unix_suggested = false;
633 for (os, span) in mismatched {
634 let sugg = format!("target_os = \"{}\"", os);
635 diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
637 if !unix_suggested && is_unix(os) {
638 diag.help("did you mean `unix`?");
639 unix_suggested = true;
647 fn is_lint_level(symbol: Symbol) -> bool {
648 matches!(symbol, sym::allow | sym::warn | sym::deny | sym::forbid)