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,
204 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AttrPass {
205 fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) {
206 if let Some(items) = &attr.meta_item_list() {
207 match &*attr.name().as_str() {
208 "allow" | "warn" | "deny" | "forbid" => {
209 check_clippy_lint_names(cx, items);
213 if items.is_empty() || attr.name() != "deprecated" {
218 if let NestedMetaItemKind::MetaItem(mi) = &item.node;
219 if let MetaItemKind::NameValue(lit) = &mi.node;
220 if mi.name() == "since";
222 check_semver(cx, item.span, lit);
229 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
230 if is_relevant_item(cx.tcx, item) {
231 check_attrs(cx, item.span, item.ident.name, &item.attrs)
234 ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
235 let skip_unused_imports = item.attrs.iter().any(|attr| attr.name() == "macro_use");
237 for attr in &item.attrs {
238 if let Some(lint_list) = &attr.meta_item_list() {
239 match &*attr.name().as_str() {
240 "allow" | "warn" | "deny" | "forbid" => {
241 // whitelist `unused_imports` and `deprecated` for `use` items
242 // and `unused_imports` for `extern crate` items with `macro_use`
243 for lint in lint_list {
245 ItemKind::Use(..) => {
246 if is_word(lint, "unused_imports") || is_word(lint, "deprecated") {
250 ItemKind::ExternCrate(..) => {
251 if is_word(lint, "unused_imports") && skip_unused_imports {
254 if is_word(lint, "unused_extern_crates") {
261 let line_span = last_line_of_span(cx, attr.span);
263 if let Some(mut sugg) = snippet_opt(cx, line_span) {
264 if sugg.contains("#[") {
269 "useless lint attribute",
271 sugg = sugg.replacen("#[", "#![", 1);
272 db.span_suggestion_with_applicability(
274 "if you just forgot a `!`, use",
276 Applicability::MachineApplicable,
292 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
293 if is_relevant_impl(cx.tcx, item) {
294 check_attrs(cx, item.span, item.ident.name, &item.attrs)
298 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
299 if is_relevant_trait(cx.tcx, item) {
300 check_attrs(cx, item.span, item.ident.name, &item.attrs)
305 #[allow(clippy::single_match_else)]
306 fn check_clippy_lint_names(cx: &LateContext<'_, '_>, items: &[NestedMetaItem]) {
307 let lint_store = cx.lints();
310 if let Some(word) = lint.word();
311 if let Some(tool_name) = word.is_scoped();
312 if tool_name.as_str() == "clippy";
313 let name = word.name();
314 if let CheckLintNameResult::Tool(Err((None, _))) = lint_store.check_lint_name(
316 Some(tool_name.as_str()),
321 UNKNOWN_CLIPPY_LINTS,
323 &format!("unknown clippy lint: clippy::{}", name),
325 if name.as_str().chars().any(|c| c.is_uppercase()) {
326 let name_lower = name.as_str().to_lowercase();
327 match lint_store.check_lint_name(
329 Some(tool_name.as_str())
331 // FIXME: can we suggest similar lint names here?
332 // https://github.com/rust-lang/rust/pull/56992
333 CheckLintNameResult::NoLint(None) => (),
335 db.span_suggestion_with_applicability(
337 "lowercase the lint name",
339 Applicability::MaybeIncorrect,
351 fn is_relevant_item(tcx: TyCtxt<'_, '_, '_>, item: &Item) -> bool {
352 if let ItemKind::Fn(_, _, _, eid) = item.node {
353 is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
359 fn is_relevant_impl(tcx: TyCtxt<'_, '_, '_>, item: &ImplItem) -> bool {
361 ImplItemKind::Method(_, eid) => is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value),
366 fn is_relevant_trait(tcx: TyCtxt<'_, '_, '_>, item: &TraitItem) -> bool {
368 TraitItemKind::Method(_, TraitMethod::Required(_)) => true,
369 TraitItemKind::Method(_, TraitMethod::Provided(eid)) => {
370 is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
376 fn is_relevant_block(tcx: TyCtxt<'_, '_, '_>, tables: &ty::TypeckTables<'_>, block: &Block) -> bool {
377 if let Some(stmt) = block.stmts.first() {
379 StmtKind::Decl(_, _) => true,
380 StmtKind::Expr(expr, _) | StmtKind::Semi(expr, _) => is_relevant_expr(tcx, tables, expr),
383 block.expr.as_ref().map_or(false, |e| is_relevant_expr(tcx, tables, e))
387 fn is_relevant_expr(tcx: TyCtxt<'_, '_, '_>, tables: &ty::TypeckTables<'_>, expr: &Expr) -> bool {
389 ExprKind::Block(block, _) => is_relevant_block(tcx, tables, block),
390 ExprKind::Ret(Some(e)) => is_relevant_expr(tcx, tables, e),
391 ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
392 ExprKind::Call(path_expr, _) => {
393 if let ExprKind::Path(qpath) = &path_expr.node {
394 if let Some(fun_id) = opt_def_id(tables.qpath_def(qpath, path_expr.hir_id)) {
395 !match_def_path(tcx, fun_id, &paths::BEGIN_PANIC)
407 fn check_attrs(cx: &LateContext<'_, '_>, span: Span, name: Name, attrs: &[Attribute]) {
413 if attr.is_sugared_doc {
416 if attr.style == AttrStyle::Outer {
417 if attr.tokens.is_empty() || !is_present_in_source(cx, attr.span) {
421 let begin_of_attr_to_item = Span::new(attr.span.lo(), span.lo(), span.ctxt());
422 let end_of_attr_to_item = Span::new(attr.span.hi(), span.lo(), span.ctxt());
424 if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) {
425 let lines = snippet.split('\n').collect::<Vec<_>>();
426 let lines = without_block_comments(lines);
428 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
431 EMPTY_LINE_AFTER_OUTER_ATTR,
432 begin_of_attr_to_item,
433 "Found an empty line after an outer attribute. \
434 Perhaps you forgot to add a '!' to make it an inner attribute?",
440 if let Some(values) = attr.meta_item_list() {
441 if values.len() != 1 || attr.name() != "inline" {
444 if is_word(&values[0], "always") {
450 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
459 fn check_semver(cx: &LateContext<'_, '_>, span: Span, lit: &Lit) {
460 if let LitKind::Str(is, _) = lit.node {
461 if Version::parse(&is.as_str()).is_ok() {
469 "the since field must contain a semver-compliant version",
473 fn is_word(nmi: &NestedMetaItem, expected: &str) -> bool {
474 if let NestedMetaItemKind::MetaItem(mi) = &nmi.node {
475 mi.is_word() && mi.name() == expected
481 // If the snippet is empty, it's an attribute that was inserted during macro
482 // expansion and we want to ignore those, because they could come from external
483 // sources that the user has no control over.
484 // For some reason these attributes don't have any expansion info on them, so
485 // we have to check it this way until there is a better way.
486 fn is_present_in_source(cx: &LateContext<'_, '_>, span: Span) -> bool {
487 if let Some(snippet) = snippet_opt(cx, span) {
488 if snippet.is_empty() {
495 #[derive(Copy, Clone)]
496 pub struct CfgAttrPass;
498 impl LintPass for CfgAttrPass {
499 fn get_lints(&self) -> LintArray {
500 lint_array!(DEPRECATED_CFG_ATTR,)
504 impl EarlyLintPass for CfgAttrPass {
505 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
508 if attr.name() == "cfg_attr";
509 if let Some(items) = attr.meta_item_list();
511 // check for `rustfmt`
512 if let Some(feature_item) = items[0].meta_item();
513 if feature_item.name() == "rustfmt";
514 // check for `rustfmt_skip` and `rustfmt::skip`
515 if let Some(skip_item) = &items[1].meta_item();
516 if skip_item.name() == "rustfmt_skip" || skip_item.name() == "skip";
517 // Only lint outer attributes, because custom inner attributes are unstable
518 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
519 if let AttrStyle::Outer = attr.style;
525 "`cfg_attr` is deprecated for rustfmt and got replaced by tool_attributes",
527 "#[rustfmt::skip]".to_string(),
528 Applicability::MachineApplicable,