1 //! checks for attributes
3 use crate::reexport::*;
5 in_macro, last_line_of_span, match_def_path, opt_def_id, paths, snippet_opt, span_lint, span_lint_and_sugg,
6 span_lint_and_then, without_block_comments,
8 use if_chain::if_chain;
11 CheckLintNameResult, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintArray, LintContext, LintPass,
13 use rustc::ty::{self, TyCtxt};
14 use rustc::{declare_tool_lint, lint_array};
15 use rustc_errors::Applicability;
17 use syntax::ast::{AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind};
18 use syntax::source_map::Span;
20 /// **What it does:** Checks for items annotated with `#[inline(always)]`,
21 /// unless the annotated function is empty or simply panics.
23 /// **Why is this bad?** While there are valid uses of this annotation (and once
24 /// you know when to use it, by all means `allow` this lint), it's a common
25 /// newbie-mistake to pepper one's code with it.
27 /// As a rule of thumb, before slapping `#[inline(always)]` on a function,
28 /// measure if that additional function call really affects your runtime profile
29 /// sufficiently to make up for the increase in compile time.
31 /// **Known problems:** False positives, big time. This lint is meant to be
32 /// deactivated by everyone doing serious performance work. This means having
33 /// done the measurement.
38 /// fn not_quite_hot_code(..) { ... }
40 declare_clippy_lint! {
43 "use of `#[inline(always)]`"
46 /// **What it does:** Checks for `extern crate` and `use` items annotated with
49 /// This lint whitelists `#[allow(unused_imports)]` and `#[allow(deprecated)]` on
50 /// `use` items and `#[allow(unused_imports)]` on `extern crate` items with a
51 /// `#[macro_use]` attribute.
53 /// **Why is this bad?** Lint attributes have no effect on crate imports. Most
54 /// likely a `!` was forgotten.
56 /// **Known problems:** None.
61 /// #[deny(dead_code)]
63 /// #[forbid(dead_code)]
67 /// #[allow(unused_imports)]
69 /// #[allow(unused_imports)]
73 declare_clippy_lint! {
74 pub USELESS_ATTRIBUTE,
76 "use of lint attributes on `extern crate` items"
79 /// **What it does:** Checks for `#[deprecated]` annotations with a `since`
80 /// field that is not a valid semantic version.
82 /// **Why is this bad?** For checking the version of the deprecation, it must be
83 /// a valid semver. Failing that, the contained information is useless.
85 /// **Known problems:** None.
89 /// #[deprecated(since = "forever")]
90 /// fn something_else(..) { ... }
92 declare_clippy_lint! {
93 pub DEPRECATED_SEMVER,
95 "use of `#[deprecated(since = \"x\")]` where x is not semver"
98 /// **What it does:** Checks for empty lines after outer attributes
100 /// **Why is this bad?**
101 /// Most likely the attribute was meant to be an inner attribute using a '!'.
102 /// If it was meant to be an outer attribute, then the following item
103 /// should not be separated by empty lines.
105 /// **Known problems:** Can cause false positives.
107 /// From the clippy side it's difficult to detect empty lines between an attributes and the
108 /// following item because empty lines and comments are not part of the AST. The parsing
109 /// currently works for basic cases but is not perfect.
114 /// #[inline(always)]
116 /// fn not_quite_good_code(..) { ... }
118 /// // Good (as inner attribute)
119 /// #![inline(always)]
121 /// fn this_is_fine(..) { ... }
123 /// // Good (as outer attribute)
124 /// #[inline(always)]
125 /// fn this_is_fine_too(..) { ... }
127 declare_clippy_lint! {
128 pub EMPTY_LINE_AFTER_OUTER_ATTR,
130 "empty line after outer attribute"
133 /// **What it does:** Checks for `allow`/`warn`/`deny`/`forbid` attributes with scoped clippy
134 /// lints and if those lints exist in clippy. If there is a uppercase letter in the lint name
135 /// (not the tool name) and a lowercase version of this lint exists, it will suggest to lowercase
138 /// **Why is this bad?** A lint attribute with a mistyped lint name won't have an effect.
140 /// **Known problems:** None.
145 /// #![warn(if_not_els)]
146 /// #![deny(clippy::All)]
151 /// #![warn(if_not_else)]
152 /// #![deny(clippy::all)]
154 declare_clippy_lint! {
155 pub UNKNOWN_CLIPPY_LINTS,
157 "unknown_lints for scoped Clippy lints"
160 /// **What it does:** Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
161 /// with `#[rustfmt::skip]`.
163 /// **Why is this bad?** Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
164 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
166 /// **Known problems:** This lint doesn't detect crate level inner attributes, because they get
167 /// processed before the PreExpansionPass lints get executed. See
168 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
174 /// #[cfg_attr(rustfmt, rustfmt_skip)]
183 declare_clippy_lint! {
184 pub DEPRECATED_CFG_ATTR,
186 "usage of `cfg_attr(rustfmt)` instead of `tool_attributes`"
189 #[derive(Copy, Clone)]
192 impl LintPass for AttrPass {
193 fn get_lints(&self) -> LintArray {
198 EMPTY_LINE_AFTER_OUTER_ATTR,
199 UNKNOWN_CLIPPY_LINTS,
203 fn name(&self) -> &'static str {
208 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AttrPass {
209 fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) {
210 if let Some(items) = &attr.meta_item_list() {
211 match &*attr.name().as_str() {
212 "allow" | "warn" | "deny" | "forbid" => {
213 check_clippy_lint_names(cx, items);
217 if items.is_empty() || attr.name() != "deprecated" {
222 if let NestedMetaItemKind::MetaItem(mi) = &item.node;
223 if let MetaItemKind::NameValue(lit) = &mi.node;
224 if mi.name() == "since";
226 check_semver(cx, item.span, lit);
233 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
234 if is_relevant_item(cx.tcx, item) {
235 check_attrs(cx, item.span, item.ident.name, &item.attrs)
238 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
239 let skip_unused_imports = item.attrs.iter().any(|attr| attr.name() == "macro_use");
241 for attr in &item.attrs {
242 if let Some(lint_list) = &attr.meta_item_list() {
243 match &*attr.name().as_str() {
244 "allow" | "warn" | "deny" | "forbid" => {
245 // whitelist `unused_imports` and `deprecated` for `use` items
246 // and `unused_imports` for `extern crate` items with `macro_use`
247 for lint in lint_list {
249 ItemKind::Use(..) => {
250 if is_word(lint, "unused_imports") || is_word(lint, "deprecated") {
254 ItemKind::ExternCrate(..) => {
255 if is_word(lint, "unused_imports") && skip_unused_imports {
258 if is_word(lint, "unused_extern_crates") {
265 let line_span = last_line_of_span(cx, attr.span);
267 if let Some(mut sugg) = snippet_opt(cx, line_span) {
268 if sugg.contains("#[") {
273 "useless lint attribute",
275 sugg = sugg.replacen("#[", "#![", 1);
278 "if you just forgot a `!`, use",
280 Applicability::MachineApplicable,
296 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
297 if is_relevant_impl(cx.tcx, item) {
298 check_attrs(cx, item.span, item.ident.name, &item.attrs)
302 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
303 if is_relevant_trait(cx.tcx, item) {
304 check_attrs(cx, item.span, item.ident.name, &item.attrs)
309 #[allow(clippy::single_match_else)]
310 fn check_clippy_lint_names(cx: &LateContext<'_, '_>, items: &[NestedMetaItem]) {
311 let lint_store = cx.lints();
314 if let Some(word) = lint.word();
315 if let Some(tool_name) = word.is_scoped();
316 if tool_name.as_str() == "clippy";
317 let name = word.name();
318 if let CheckLintNameResult::Tool(Err((None, _))) = lint_store.check_lint_name(
320 Some(tool_name.as_str()),
325 UNKNOWN_CLIPPY_LINTS,
327 &format!("unknown clippy lint: clippy::{}", name),
329 if name.as_str().chars().any(|c| c.is_uppercase()) {
330 let name_lower = name.as_str().to_lowercase();
331 match lint_store.check_lint_name(
333 Some(tool_name.as_str())
335 // FIXME: can we suggest similar lint names here?
336 // https://github.com/rust-lang/rust/pull/56992
337 CheckLintNameResult::NoLint(None) => (),
341 "lowercase the lint name",
343 Applicability::MaybeIncorrect,
355 fn is_relevant_item(tcx: TyCtxt<'_, '_, '_>, item: &Item) -> bool {
356 if let ItemKind::Fn(_, _, _, eid) = item.node {
357 is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
363 fn is_relevant_impl(tcx: TyCtxt<'_, '_, '_>, item: &ImplItem) -> bool {
365 ImplItemKind::Method(_, eid) => is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value),
370 fn is_relevant_trait(tcx: TyCtxt<'_, '_, '_>, item: &TraitItem) -> bool {
372 TraitItemKind::Method(_, TraitMethod::Required(_)) => true,
373 TraitItemKind::Method(_, TraitMethod::Provided(eid)) => {
374 is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
380 fn is_relevant_block(tcx: TyCtxt<'_, '_, '_>, tables: &ty::TypeckTables<'_>, block: &Block) -> bool {
381 if let Some(stmt) = block.stmts.first() {
383 StmtKind::Local(_) => true,
384 StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(tcx, tables, expr),
388 block.expr.as_ref().map_or(false, |e| is_relevant_expr(tcx, tables, e))
392 fn is_relevant_expr(tcx: TyCtxt<'_, '_, '_>, tables: &ty::TypeckTables<'_>, expr: &Expr) -> bool {
394 ExprKind::Block(block, _) => is_relevant_block(tcx, tables, block),
395 ExprKind::Ret(Some(e)) => is_relevant_expr(tcx, tables, e),
396 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
397 ExprKind::Call(path_expr, _) => {
398 if let ExprKind::Path(qpath) = &path_expr.node {
399 if let Some(fun_id) = opt_def_id(tables.qpath_def(qpath, path_expr.hir_id)) {
400 !match_def_path(tcx, fun_id, &paths::BEGIN_PANIC)
412 fn check_attrs(cx: &LateContext<'_, '_>, span: Span, name: Name, attrs: &[Attribute]) {
418 if attr.is_sugared_doc {
421 if attr.style == AttrStyle::Outer {
422 if attr.tokens.is_empty() || !is_present_in_source(cx, attr.span) {
426 let begin_of_attr_to_item = Span::new(attr.span.lo(), span.lo(), span.ctxt());
427 let end_of_attr_to_item = Span::new(attr.span.hi(), span.lo(), span.ctxt());
429 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) {
430 let lines = snippet.split('\n').collect::<Vec<_>>();
431 let lines = without_block_comments(lines);
433 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
436 EMPTY_LINE_AFTER_OUTER_ATTR,
437 begin_of_attr_to_item,
438 "Found an empty line after an outer attribute. \
439 Perhaps you forgot to add a '!' to make it an inner attribute?",
445 if let Some(values) = attr.meta_item_list() {
446 if values.len() != 1 || attr.name() != "inline" {
449 if is_word(&values[0], "always") {
455 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
464 fn check_semver(cx: &LateContext<'_, '_>, span: Span, lit: &Lit) {
465 if let LitKind::Str(is, _) = lit.node {
466 if Version::parse(&is.as_str()).is_ok() {
474 "the since field must contain a semver-compliant version",
478 fn is_word(nmi: &NestedMetaItem, expected: &str) -> bool {
479 if let NestedMetaItemKind::MetaItem(mi) = &nmi.node {
480 mi.is_word() && mi.name() == expected
486 // If the snippet is empty, it's an attribute that was inserted during macro
487 // expansion and we want to ignore those, because they could come from external
488 // sources that the user has no control over.
489 // For some reason these attributes don't have any expansion info on them, so
490 // we have to check it this way until there is a better way.
491 fn is_present_in_source(cx: &LateContext<'_, '_>, span: Span) -> bool {
492 if let Some(snippet) = snippet_opt(cx, span) {
493 if snippet.is_empty() {
500 #[derive(Copy, Clone)]
501 pub struct CfgAttrPass;
503 impl LintPass for CfgAttrPass {
504 fn get_lints(&self) -> LintArray {
505 lint_array!(DEPRECATED_CFG_ATTR,)
508 fn name(&self) -> &'static str {
509 "DeprecatedCfgAttribute"
513 impl EarlyLintPass for CfgAttrPass {
514 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
517 if attr.name() == "cfg_attr";
518 if let Some(items) = attr.meta_item_list();
520 // check for `rustfmt`
521 if let Some(feature_item) = items[0].meta_item();
522 if feature_item.name() == "rustfmt";
523 // check for `rustfmt_skip` and `rustfmt::skip`
524 if let Some(skip_item) = &items[1].meta_item();
525 if skip_item.name() == "rustfmt_skip" || skip_item.name() == "skip";
526 // Only lint outer attributes, because custom inner attributes are unstable
527 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
528 if let AttrStyle::Outer = attr.style;
534 "`cfg_attr` is deprecated for rustfmt and got replaced by tool_attributes",
536 "#[rustfmt::skip]".to_string(),
537 Applicability::MachineApplicable,