1 //! checks for attributes
3 use crate::reexport::*;
5 in_macro, last_line_of_span, match_def_path, paths, snippet_opt, span_lint, span_lint_and_sugg, span_lint_and_then,
6 without_block_comments,
8 use if_chain::if_chain;
11 in_external_macro, CheckLintNameResult, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintArray,
12 LintContext, LintPass,
14 use rustc::ty::{self, TyCtxt};
15 use rustc::{declare_tool_lint, lint_array};
16 use rustc_errors::Applicability;
18 use syntax::ast::{AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
19 use syntax::source_map::Span;
21 declare_clippy_lint! {
22 /// **What it does:** Checks for items annotated with `#[inline(always)]`,
23 /// unless the annotated function is empty or simply panics.
25 /// **Why is this bad?** While there are valid uses of this annotation (and once
26 /// you know when to use it, by all means `allow` this lint), it's a common
27 /// newbie-mistake to pepper one's code with it.
29 /// As a rule of thumb, before slapping `#[inline(always)]` on a function,
30 /// measure if that additional function call really affects your runtime profile
31 /// sufficiently to make up for the increase in compile time.
33 /// **Known problems:** False positives, big time. This lint is meant to be
34 /// deactivated by everyone doing serious performance work. This means having
35 /// done the measurement.
40 /// fn not_quite_hot_code(..) { ... }
44 "use of `#[inline(always)]`"
47 declare_clippy_lint! {
48 /// **What it does:** Checks for `extern crate` and `use` items annotated with
51 /// This lint whitelists `#[allow(unused_imports)]` and `#[allow(deprecated)]` on
52 /// `use` items and `#[allow(unused_imports)]` on `extern crate` items with a
53 /// `#[macro_use]` attribute.
55 /// **Why is this bad?** Lint attributes have no effect on crate imports. Most
56 /// likely a `!` was forgotten.
58 /// **Known problems:** None.
63 /// #[deny(dead_code)]
65 /// #[forbid(dead_code)]
69 /// #[allow(unused_imports)]
71 /// #[allow(unused_imports)]
75 pub USELESS_ATTRIBUTE,
77 "use of lint attributes on `extern crate` items"
80 declare_clippy_lint! {
81 /// **What it does:** Checks for `#[deprecated]` annotations with a `since`
82 /// field that is not a valid semantic version.
84 /// **Why is this bad?** For checking the version of the deprecation, it must be
85 /// a valid semver. Failing that, the contained information is useless.
87 /// **Known problems:** None.
91 /// #[deprecated(since = "forever")]
92 /// fn something_else() { /* ... */ }
94 pub DEPRECATED_SEMVER,
96 "use of `#[deprecated(since = \"x\")]` where x is not semver"
99 declare_clippy_lint! {
100 /// **What it does:** Checks for empty lines after outer attributes
102 /// **Why is this bad?**
103 /// Most likely the attribute was meant to be an inner attribute using a '!'.
104 /// If it was meant to be an outer attribute, then the following item
105 /// should not be separated by empty lines.
107 /// **Known problems:** Can cause false positives.
109 /// From the clippy side it's difficult to detect empty lines between an attributes and the
110 /// following item because empty lines and comments are not part of the AST. The parsing
111 /// currently works for basic cases but is not perfect.
116 /// #[inline(always)]
118 /// fn not_quite_good_code(..) { ... }
120 /// // Good (as inner attribute)
121 /// #![inline(always)]
123 /// fn this_is_fine(..) { ... }
125 /// // Good (as outer attribute)
126 /// #[inline(always)]
127 /// fn this_is_fine_too(..) { ... }
129 pub EMPTY_LINE_AFTER_OUTER_ATTR,
131 "empty line after outer attribute"
134 declare_clippy_lint! {
135 /// **What it does:** Checks for `allow`/`warn`/`deny`/`forbid` attributes with scoped clippy
136 /// lints and if those lints exist in clippy. If there is a uppercase letter in the lint name
137 /// (not the tool name) and a lowercase version of this lint exists, it will suggest to lowercase
140 /// **Why is this bad?** A lint attribute with a mistyped lint name won't have an effect.
142 /// **Known problems:** None.
147 /// #![warn(if_not_els)]
148 /// #![deny(clippy::All)]
153 /// #![warn(if_not_else)]
154 /// #![deny(clippy::all)]
156 pub UNKNOWN_CLIPPY_LINTS,
158 "unknown_lints for scoped Clippy lints"
161 declare_clippy_lint! {
162 /// **What it does:** Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
163 /// with `#[rustfmt::skip]`.
165 /// **Why is this bad?** Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
166 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
168 /// **Known problems:** This lint doesn't detect crate level inner attributes, because they get
169 /// processed before the PreExpansionPass lints get executed. See
170 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
176 /// #[cfg_attr(rustfmt, rustfmt_skip)]
185 pub DEPRECATED_CFG_ATTR,
187 "usage of `cfg_attr(rustfmt)` instead of `tool_attributes`"
190 #[derive(Copy, Clone)]
193 impl LintPass for AttrPass {
194 fn get_lints(&self) -> LintArray {
199 EMPTY_LINE_AFTER_OUTER_ATTR,
200 UNKNOWN_CLIPPY_LINTS,
204 fn name(&self) -> &'static str {
209 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AttrPass {
210 fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) {
211 if let Some(items) = &attr.meta_item_list() {
212 if let Some(ident) = attr.ident() {
213 match &*ident.as_str() {
214 "allow" | "warn" | "deny" | "forbid" => {
215 check_clippy_lint_names(cx, items);
219 if items.is_empty() || !attr.check_name("deprecated") {
224 if let NestedMetaItem::MetaItem(mi) = &item;
225 if let MetaItemKind::NameValue(lit) = &mi.node;
226 if mi.check_name("since");
228 check_semver(cx, item.span(), lit);
236 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
237 if is_relevant_item(cx.tcx, item) {
238 check_attrs(cx, item.span, item.ident.name, &item.attrs)
241 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
242 let skip_unused_imports = item.attrs.iter().any(|attr| attr.check_name("macro_use"));
244 for attr in &item.attrs {
245 if in_external_macro(cx.sess(), attr.span) {
248 if let Some(lint_list) = &attr.meta_item_list() {
249 if let Some(ident) = attr.ident() {
250 match &*ident.as_str() {
251 "allow" | "warn" | "deny" | "forbid" => {
252 // whitelist `unused_imports` and `deprecated` for `use` items
253 // and `unused_imports` for `extern crate` items with `macro_use`
254 for lint in lint_list {
256 ItemKind::Use(..) => {
257 if is_word(lint, "unused_imports") || is_word(lint, "deprecated") {
261 ItemKind::ExternCrate(..) => {
262 if is_word(lint, "unused_imports") && skip_unused_imports {
265 if is_word(lint, "unused_extern_crates") {
272 let line_span = last_line_of_span(cx, attr.span);
274 if let Some(mut sugg) = snippet_opt(cx, line_span) {
275 if sugg.contains("#[") {
280 "useless lint attribute",
282 sugg = sugg.replacen("#[", "#![", 1);
285 "if you just forgot a `!`, use",
287 Applicability::MachineApplicable,
304 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
305 if is_relevant_impl(cx.tcx, item) {
306 check_attrs(cx, item.span, item.ident.name, &item.attrs)
310 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
311 if is_relevant_trait(cx.tcx, item) {
312 check_attrs(cx, item.span, item.ident.name, &item.attrs)
317 #[allow(clippy::single_match_else)]
318 fn check_clippy_lint_names(cx: &LateContext<'_, '_>, items: &[NestedMetaItem]) {
319 let lint_store = cx.lints();
322 if let Some(meta_item) = lint.meta_item();
323 if meta_item.path.segments.len() > 1;
324 if let tool_name = meta_item.path.segments[0].ident;
325 if tool_name.as_str() == "clippy";
326 let name = meta_item.path.segments.last().unwrap().ident.name;
327 if let CheckLintNameResult::Tool(Err((None, _))) = lint_store.check_lint_name(
329 Some(tool_name.as_str()),
334 UNKNOWN_CLIPPY_LINTS,
336 &format!("unknown clippy lint: clippy::{}", name),
338 if name.as_str().chars().any(char::is_uppercase) {
339 let name_lower = name.as_str().to_lowercase();
340 match lint_store.check_lint_name(
342 Some(tool_name.as_str())
344 // FIXME: can we suggest similar lint names here?
345 // https://github.com/rust-lang/rust/pull/56992
346 CheckLintNameResult::NoLint(None) => (),
350 "lowercase the lint name",
352 Applicability::MaybeIncorrect,
364 fn is_relevant_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item: &Item) -> bool {
365 if let ItemKind::Fn(_, _, _, eid) = item.node {
366 is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
372 fn is_relevant_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item: &ImplItem) -> bool {
374 ImplItemKind::Method(_, eid) => is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value),
379 fn is_relevant_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item: &TraitItem) -> bool {
381 TraitItemKind::Method(_, TraitMethod::Required(_)) => true,
382 TraitItemKind::Method(_, TraitMethod::Provided(eid)) => {
383 is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
389 fn is_relevant_block<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, tables: &ty::TypeckTables<'_>, block: &Block) -> bool {
390 if let Some(stmt) = block.stmts.first() {
392 StmtKind::Local(_) => true,
393 StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(tcx, tables, expr),
397 block.expr.as_ref().map_or(false, |e| is_relevant_expr(tcx, tables, e))
401 fn is_relevant_expr<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, tables: &ty::TypeckTables<'_>, expr: &Expr) -> bool {
403 ExprKind::Block(block, _) => is_relevant_block(tcx, tables, block),
404 ExprKind::Ret(Some(e)) => is_relevant_expr(tcx, tables, e),
405 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
406 ExprKind::Call(path_expr, _) => {
407 if let ExprKind::Path(qpath) = &path_expr.node {
408 if let Some(fun_id) = tables.qpath_def(qpath, path_expr.hir_id).opt_def_id() {
409 !match_def_path(tcx, fun_id, &paths::BEGIN_PANIC)
421 fn check_attrs(cx: &LateContext<'_, '_>, span: Span, name: Name, attrs: &[Attribute]) {
427 if attr.is_sugared_doc {
430 if attr.style == AttrStyle::Outer {
431 if attr.tokens.is_empty() || !is_present_in_source(cx, attr.span) {
435 let begin_of_attr_to_item = Span::new(attr.span.lo(), span.lo(), span.ctxt());
436 let end_of_attr_to_item = Span::new(attr.span.hi(), span.lo(), span.ctxt());
438 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) {
439 let lines = snippet.split('\n').collect::<Vec<_>>();
440 let lines = without_block_comments(lines);
442 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
445 EMPTY_LINE_AFTER_OUTER_ATTR,
446 begin_of_attr_to_item,
447 "Found an empty line after an outer attribute. \
448 Perhaps you forgot to add a '!' to make it an inner attribute?",
454 if let Some(values) = attr.meta_item_list() {
455 if values.len() != 1 || !attr.check_name("inline") {
458 if is_word(&values[0], "always") {
464 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
473 fn check_semver(cx: &LateContext<'_, '_>, span: Span, lit: &Lit) {
474 if let LitKind::Str(is, _) = lit.node {
475 if Version::parse(&is.as_str()).is_ok() {
483 "the since field must contain a semver-compliant version",
487 fn is_word(nmi: &NestedMetaItem, expected: &str) -> bool {
488 if let NestedMetaItem::MetaItem(mi) = &nmi {
489 mi.is_word() && mi.check_name(expected)
495 // If the snippet is empty, it's an attribute that was inserted during macro
496 // expansion and we want to ignore those, because they could come from external
497 // sources that the user has no control over.
498 // For some reason these attributes don't have any expansion info on them, so
499 // we have to check it this way until there is a better way.
500 fn is_present_in_source(cx: &LateContext<'_, '_>, span: Span) -> bool {
501 if let Some(snippet) = snippet_opt(cx, span) {
502 if snippet.is_empty() {
509 #[derive(Copy, Clone)]
510 pub struct CfgAttrPass;
512 impl LintPass for CfgAttrPass {
513 fn get_lints(&self) -> LintArray {
514 lint_array!(DEPRECATED_CFG_ATTR,)
517 fn name(&self) -> &'static str {
518 "DeprecatedCfgAttribute"
522 impl EarlyLintPass for CfgAttrPass {
523 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
526 if attr.check_name("cfg_attr");
527 if let Some(items) = attr.meta_item_list();
529 // check for `rustfmt`
530 if let Some(feature_item) = items[0].meta_item();
531 if feature_item.check_name("rustfmt");
532 // check for `rustfmt_skip` and `rustfmt::skip`
533 if let Some(skip_item) = &items[1].meta_item();
534 if skip_item.check_name("rustfmt_skip") ||
535 skip_item.path.segments.last().expect("empty path in attribute").ident.name == "skip";
536 // Only lint outer attributes, because custom inner attributes are unstable
537 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
538 if let AttrStyle::Outer = attr.style;
544 "`cfg_attr` is deprecated for rustfmt and got replaced by tool_attributes",
546 "#[rustfmt::skip]".to_string(),
547 Applicability::MachineApplicable,