1 //! checks for attributes
4 first_line_of_span
, is_present_in_source
, match_def_path
, paths
, snippet_opt
, span_lint
, span_lint_and_help
,
5 span_lint_and_sugg
, span_lint_and_then
, without_block_comments
,
7 use if_chain
::if_chain
;
8 use rustc_ast
::util
::lev_distance
::find_best_match_for_name
;
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
::{CheckLintNameResult, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext}
;
15 use rustc_middle
::lint
::in_external_macro
;
17 use rustc_session
::{declare_lint_pass, declare_tool_lint}
;
18 use rustc_span
::source_map
::Span
;
20 use rustc_span
::symbol
::{Symbol, SymbolStr}
;
23 static UNIX_SYSTEMS
: &[&str] = &[
42 // NOTE: windows is excluded from the list because it's also a valid target family.
43 static NON_UNIX_SYSTEMS
: &[&str] = &["cloudabi", "hermit", "none", "wasi"];
45 declare_clippy_lint
! {
46 /// **What it does:** Checks for items annotated with `#[inline(always)]`,
47 /// unless the annotated function is empty or simply panics.
49 /// **Why is this bad?** 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:** False positives, big time. This lint is meant to be
58 /// deactivated by everyone doing serious performance work. This means having
59 /// done the measurement.
64 /// fn not_quite_hot_code(..) { ... }
68 "use of `#[inline(always)]`"
71 declare_clippy_lint
! {
72 /// **What it does:** Checks for `extern crate` and `use` items annotated with
75 /// This lint permits `#[allow(unused_imports)]`, `#[allow(deprecated)]`,
76 /// `#[allow(unreachable_pub)]`, `#[allow(clippy::wildcard_imports)]` and
77 /// `#[allow(clippy::enum_glob_use)]` on `use` items and `#[allow(unused_imports)]` on
78 /// `extern crate` items with a `#[macro_use]` attribute.
80 /// **Why is this bad?** Lint attributes have no effect on crate imports. Most
81 /// likely a `!` was forgotten.
83 /// **Known problems:** None.
88 /// #[deny(dead_code)]
90 /// #[forbid(dead_code)]
94 /// #[allow(unused_imports)]
96 /// #[allow(unused_imports)]
100 pub USELESS_ATTRIBUTE
,
102 "use of lint attributes on `extern crate` items"
105 declare_clippy_lint
! {
106 /// **What it does:** Checks for `#[deprecated]` annotations with a `since`
107 /// field that is not a valid semantic version.
109 /// **Why is this bad?** For checking the version of the deprecation, it must be
110 /// a valid semver. Failing that, the contained information is useless.
112 /// **Known problems:** None.
116 /// #[deprecated(since = "forever")]
117 /// fn something_else() { /* ... */ }
119 pub DEPRECATED_SEMVER
,
121 "use of `#[deprecated(since = \"x\")]` where x is not semver"
124 declare_clippy_lint
! {
125 /// **What it does:** Checks for empty lines after outer attributes
127 /// **Why is this bad?**
128 /// Most likely the attribute was meant to be an inner attribute using a '!'.
129 /// If it was meant to be an outer attribute, then the following item
130 /// should not be separated by empty lines.
132 /// **Known problems:** Can cause false positives.
134 /// From the clippy side it's difficult to detect empty lines between an attributes and the
135 /// following item because empty lines and comments are not part of the AST. The parsing
136 /// currently works for basic cases but is not perfect.
140 /// // Good (as inner attribute)
141 /// #![allow(dead_code)]
143 /// fn this_is_fine() { }
146 /// #[allow(dead_code)]
148 /// fn not_quite_good_code() { }
150 /// // Good (as outer attribute)
151 /// #[allow(dead_code)]
152 /// fn this_is_fine_too() { }
154 pub EMPTY_LINE_AFTER_OUTER_ATTR
,
156 "empty line after outer attribute"
159 declare_clippy_lint
! {
160 /// **What it does:** Checks for `allow`/`warn`/`deny`/`forbid` attributes with scoped clippy
161 /// lints and if those lints exist in clippy. If there is an uppercase letter in the lint name
162 /// (not the tool name) and a lowercase version of this lint exists, it will suggest to lowercase
165 /// **Why is this bad?** A lint attribute with a mistyped lint name won't have an effect.
167 /// **Known problems:** None.
172 /// #![warn(if_not_els)]
173 /// #![deny(clippy::All)]
178 /// #![warn(if_not_else)]
179 /// #![deny(clippy::all)]
181 pub UNKNOWN_CLIPPY_LINTS
,
183 "unknown_lints for scoped Clippy lints"
186 declare_clippy_lint
! {
187 /// **What it does:** Checks for `warn`/`deny`/`forbid` attributes targeting the whole clippy::restriction category.
189 /// **Why is this bad?** Restriction lints sometimes are in contrast with other lints or even go against idiomatic rust.
190 /// These lints should only be enabled on a lint-by-lint basis and with careful consideration.
192 /// **Known problems:** None.
197 /// #![deny(clippy::restriction)]
202 /// #![deny(clippy::as_conversions)]
204 pub BLANKET_CLIPPY_RESTRICTION_LINTS
,
206 "enabling the complete restriction group"
209 declare_clippy_lint
! {
210 /// **What it does:** Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
211 /// with `#[rustfmt::skip]`.
213 /// **Why is this bad?** Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
214 /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
216 /// **Known problems:** This lint doesn't detect crate level inner attributes, because they get
217 /// processed before the PreExpansionPass lints get executed. See
218 /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
224 /// #[cfg_attr(rustfmt, rustfmt_skip)]
233 pub DEPRECATED_CFG_ATTR
,
235 "usage of `cfg_attr(rustfmt)` instead of tool attributes"
238 declare_clippy_lint
! {
239 /// **What it does:** Checks for cfg attributes having operating systems used in target family position.
241 /// **Why is this bad?** The configuration option will not be recognised and the related item will not be included
242 /// by the conditional compilation engine.
244 /// **Known problems:** None.
251 /// fn conditional() { }
256 /// #[cfg(target_os = "linux")]
257 /// fn conditional() { }
263 /// fn conditional() { }
265 /// Check the [Rust Reference](https://doc.rust-lang.org/reference/conditional-compilation.html#target_os) for more details.
266 pub MISMATCHED_TARGET_OS
,
268 "usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
271 declare_lint_pass
!(Attributes
=> [
275 UNKNOWN_CLIPPY_LINTS
,
276 BLANKET_CLIPPY_RESTRICTION_LINTS
,
279 impl<'tcx
> LateLintPass
<'tcx
> for Attributes
{
280 fn check_attribute(&mut self, cx
: &LateContext
<'tcx
>, attr
: &'tcx Attribute
) {
281 if let Some(items
) = &attr
.meta_item_list() {
282 if let Some(ident
) = attr
.ident() {
283 let ident
= &*ident
.as_str();
285 "allow" | "warn" | "deny" | "forbid" => {
286 check_clippy_lint_names(cx
, ident
, items
);
290 if items
.is_empty() || !attr
.has_name(sym
::deprecated
) {
295 if let NestedMetaItem
::MetaItem(mi
) = &item
;
296 if let MetaItemKind
::NameValue(lit
) = &mi
.kind
;
297 if mi
.has_name(sym
::since
);
299 check_semver(cx
, item
.span(), lit
);
307 fn check_item(&mut self, cx
: &LateContext
<'tcx
>, item
: &'tcx Item
<'_
>) {
308 if is_relevant_item(cx
, item
) {
309 check_attrs(cx
, item
.span
, item
.ident
.name
, &item
.attrs
)
312 ItemKind
::ExternCrate(..) | ItemKind
::Use(..) => {
313 let skip_unused_imports
= item
.attrs
.iter().any(|attr
| attr
.has_name(sym
::macro_use
));
315 for attr
in item
.attrs
{
316 if in_external_macro(cx
.sess(), attr
.span
) {
319 if let Some(lint_list
) = &attr
.meta_item_list() {
320 if let Some(ident
) = attr
.ident() {
321 match &*ident
.as_str() {
322 "allow" | "warn" | "deny" | "forbid" => {
323 // permit `unused_imports`, `deprecated`, `unreachable_pub`,
324 // `clippy::wildcard_imports`, and `clippy::enum_glob_use` for `use` items
325 // and `unused_imports` for `extern crate` items with `macro_use`
326 for lint
in lint_list
{
328 ItemKind
::Use(..) => {
329 if is_word(lint
, sym
!(unused_imports
))
330 || is_word(lint
, sym
::deprecated
)
331 || is_word(lint
, sym
!(unreachable_pub
))
332 || is_word(lint
, sym
!(unused
))
333 || extract_clippy_lint(lint
)
334 .map_or(false, |s
| s
== "wildcard_imports")
335 || extract_clippy_lint(lint
).map_or(false, |s
| s
== "enum_glob_use")
340 ItemKind
::ExternCrate(..) => {
341 if is_word(lint
, sym
!(unused_imports
)) && skip_unused_imports
{
344 if is_word(lint
, sym
!(unused_extern_crates
)) {
351 let line_span
= first_line_of_span(cx
, attr
.span
);
353 if let Some(mut sugg
) = snippet_opt(cx
, line_span
) {
354 if sugg
.contains("#[") {
359 "useless lint attribute",
361 sugg
= sugg
.replacen("#[", "#![", 1);
362 diag
.span_suggestion(
364 "if you just forgot a `!`, use",
366 Applicability
::MaybeIncorrect
,
383 fn check_impl_item(&mut self, cx
: &LateContext
<'tcx
>, item
: &'tcx ImplItem
<'_
>) {
384 if is_relevant_impl(cx
, item
) {
385 check_attrs(cx
, item
.span
, item
.ident
.name
, &item
.attrs
)
389 fn check_trait_item(&mut self, cx
: &LateContext
<'tcx
>, item
: &'tcx TraitItem
<'_
>) {
390 if is_relevant_trait(cx
, item
) {
391 check_attrs(cx
, item
.span
, item
.ident
.name
, &item
.attrs
)
396 /// Returns the lint name if it is clippy lint.
397 fn extract_clippy_lint(lint
: &NestedMetaItem
) -> Option
<SymbolStr
> {
399 if let Some(meta_item
) = lint
.meta_item();
400 if meta_item
.path
.segments
.len() > 1;
401 if let tool_name
= meta_item
.path
.segments
[0].ident
;
402 if tool_name
.as_str() == "clippy";
403 let lint_name
= meta_item
.path
.segments
.last().unwrap().ident
.name
;
405 return Some(lint_name
.as_str());
411 fn check_clippy_lint_names(cx
: &LateContext
<'_
>, ident
: &str, items
: &[NestedMetaItem
]) {
412 let lint_store
= cx
.lints();
414 if let Some(lint_name
) = extract_clippy_lint(lint
) {
415 if let CheckLintNameResult
::Tool(Err((None
, _
))) = lint_store
.check_lint_name(&lint_name
, Some(sym
::clippy
))
419 UNKNOWN_CLIPPY_LINTS
,
421 &format
!("unknown clippy lint: clippy::{}", lint_name
),
423 let name_lower
= lint_name
.to_lowercase();
424 let symbols
= lint_store
427 .map(|l
| Symbol
::intern(&l
.name_lower()))
428 .collect
::<Vec
<_
>>();
429 let sugg
= find_best_match_for_name(
431 Symbol
::intern(&format
!("clippy::{}", name_lower
)),
434 if lint_name
.chars().any(char::is_uppercase
)
435 && lint_store
.find_lints(&format
!("clippy::{}", name_lower
)).is_ok()
437 diag
.span_suggestion(
439 "lowercase the lint name",
440 format
!("clippy::{}", name_lower
),
441 Applicability
::MachineApplicable
,
443 } else if let Some(sugg
) = sugg
{
444 diag
.span_suggestion(
448 Applicability
::MachineApplicable
,
453 } else if lint_name
== "restriction" && ident
!= "allow" {
456 BLANKET_CLIPPY_RESTRICTION_LINTS
,
458 "restriction lints are not meant to be all enabled",
460 "try enabling only the lints you really need",
467 fn is_relevant_item(cx
: &LateContext
<'_
>, item
: &Item
<'_
>) -> bool
{
468 if let ItemKind
::Fn(_
, _
, eid
) = item
.kind
{
469 is_relevant_expr(cx
, cx
.tcx
.typeck_body(eid
), &cx
.tcx
.hir().body(eid
).value
)
475 fn is_relevant_impl(cx
: &LateContext
<'_
>, item
: &ImplItem
<'_
>) -> bool
{
477 ImplItemKind
::Fn(_
, eid
) => is_relevant_expr(cx
, cx
.tcx
.typeck_body(eid
), &cx
.tcx
.hir().body(eid
).value
),
482 fn is_relevant_trait(cx
: &LateContext
<'_
>, item
: &TraitItem
<'_
>) -> bool
{
484 TraitItemKind
::Fn(_
, TraitFn
::Required(_
)) => true,
485 TraitItemKind
::Fn(_
, TraitFn
::Provided(eid
)) => {
486 is_relevant_expr(cx
, cx
.tcx
.typeck_body(eid
), &cx
.tcx
.hir().body(eid
).value
)
492 fn is_relevant_block(cx
: &LateContext
<'_
>, typeck_results
: &ty
::TypeckResults
<'_
>, block
: &Block
<'_
>) -> bool
{
493 block
.stmts
.first().map_or(
497 .map_or(false, |e
| is_relevant_expr(cx
, typeck_results
, e
)),
498 |stmt
| match &stmt
.kind
{
499 StmtKind
::Local(_
) => true,
500 StmtKind
::Expr(expr
) | StmtKind
::Semi(expr
) => is_relevant_expr(cx
, typeck_results
, expr
),
506 fn is_relevant_expr(cx
: &LateContext
<'_
>, typeck_results
: &ty
::TypeckResults
<'_
>, expr
: &Expr
<'_
>) -> bool
{
508 ExprKind
::Block(block
, _
) => is_relevant_block(cx
, typeck_results
, block
),
509 ExprKind
::Ret(Some(e
)) => is_relevant_expr(cx
, typeck_results
, e
),
510 ExprKind
::Ret(None
) | ExprKind
::Break(_
, None
) => false,
511 ExprKind
::Call(path_expr
, _
) => {
512 if let ExprKind
::Path(qpath
) = &path_expr
.kind
{
514 .qpath_res(qpath
, path_expr
.hir_id
)
516 .map_or(true, |fun_id
| !match_def_path(cx
, fun_id
, &paths
::BEGIN_PANIC
))
525 fn check_attrs(cx
: &LateContext
<'_
>, span
: Span
, name
: Symbol
, attrs
: &[Attribute
]) {
526 if span
.from_expansion() {
531 if let Some(values
) = attr
.meta_item_list() {
532 if values
.len() != 1 || !attr
.has_name(sym
::inline
) {
535 if is_word(&values
[0], sym
::always
) {
541 "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
550 fn check_semver(cx
: &LateContext
<'_
>, span
: Span
, lit
: &Lit
) {
551 if let LitKind
::Str(is
, _
) = lit
.kind
{
552 if Version
::parse(&is
.as_str()).is_ok() {
560 "the since field must contain a semver-compliant version",
564 fn is_word(nmi
: &NestedMetaItem
, expected
: Symbol
) -> bool
{
565 if let NestedMetaItem
::MetaItem(mi
) = &nmi
{
566 mi
.is_word() && mi
.has_name(expected
)
572 declare_lint_pass
!(EarlyAttributes
=> [
574 MISMATCHED_TARGET_OS
,
575 EMPTY_LINE_AFTER_OUTER_ATTR
,
578 impl EarlyLintPass
for EarlyAttributes
{
579 fn check_item(&mut self, cx
: &EarlyContext
<'_
>, item
: &rustc_ast
::Item
) {
580 check_empty_line_after_outer_attr(cx
, item
);
583 fn check_attribute(&mut self, cx
: &EarlyContext
<'_
>, attr
: &Attribute
) {
584 check_deprecated_cfg_attr(cx
, attr
);
585 check_mismatched_target_os(cx
, attr
);
589 fn check_empty_line_after_outer_attr(cx
: &EarlyContext
<'_
>, item
: &rustc_ast
::Item
) {
590 for attr
in &item
.attrs
{
591 let attr_item
= if let AttrKind
::Normal(ref attr
, _
) = attr
.kind
{
597 if attr
.style
== AttrStyle
::Outer
{
598 if attr_item
.args
.inner_tokens().is_empty() || !is_present_in_source(cx
, attr
.span
) {
602 let begin_of_attr_to_item
= Span
::new(attr
.span
.lo(), item
.span
.lo(), item
.span
.ctxt());
603 let end_of_attr_to_item
= Span
::new(attr
.span
.hi(), item
.span
.lo(), item
.span
.ctxt());
605 if let Some(snippet
) = snippet_opt(cx
, end_of_attr_to_item
) {
606 let lines
= snippet
.split('
\n'
).collect
::<Vec
<_
>>();
607 let lines
= without_block_comments(lines
);
609 if lines
.iter().filter(|l
| l
.trim().is_empty()).count() > 2 {
612 EMPTY_LINE_AFTER_OUTER_ATTR
,
613 begin_of_attr_to_item
,
614 "found an empty line after an outer attribute. \
615 Perhaps you forgot to add a `!` to make it an inner attribute?",
623 fn check_deprecated_cfg_attr(cx
: &EarlyContext
<'_
>, attr
: &Attribute
) {
626 if attr
.has_name(sym
::cfg_attr
);
627 if let Some(items
) = attr
.meta_item_list();
629 // check for `rustfmt`
630 if let Some(feature_item
) = items
[0].meta_item();
631 if feature_item
.has_name(sym
::rustfmt
);
632 // check for `rustfmt_skip` and `rustfmt::skip`
633 if let Some(skip_item
) = &items
[1].meta_item();
634 if skip_item
.has_name(sym
!(rustfmt_skip
)) ||
635 skip_item
.path
.segments
.last().expect("empty path in attribute").ident
.name
== sym
!(skip
);
636 // Only lint outer attributes, because custom inner attributes are unstable
637 // Tracking issue: https://github.com/rust-lang/rust/issues/54726
638 if let AttrStyle
::Outer
= attr
.style
;
644 "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
646 "#[rustfmt::skip]".to_string(),
647 Applicability
::MachineApplicable
,
653 fn check_mismatched_target_os(cx
: &EarlyContext
<'_
>, attr
: &Attribute
) {
654 fn find_os(name
: &str) -> Option
<&'
static str> {
657 .chain(NON_UNIX_SYSTEMS
.iter())
658 .find(|&&os
| os
== name
)
662 fn is_unix(name
: &str) -> bool
{
663 UNIX_SYSTEMS
.iter().any(|&os
| os
== name
)
666 fn find_mismatched_target_os(items
: &[NestedMetaItem
]) -> Vec
<(&str, Span
)> {
667 let mut mismatched
= Vec
::new();
670 if let NestedMetaItem
::MetaItem(meta
) = item
{
672 MetaItemKind
::List(list
) => {
673 mismatched
.extend(find_mismatched_target_os(&list
));
675 MetaItemKind
::Word
=> {
677 if let Some(ident
) = meta
.ident();
678 if let Some(os
) = find_os(&*ident
.name
.as_str());
680 mismatched
.push((os
, ident
.span
));
693 if attr
.has_name(sym
::cfg
);
694 if let Some(list
) = attr
.meta_item_list();
695 let mismatched
= find_mismatched_target_os(&list
);
696 if !mismatched
.is_empty();
698 let mess
= "operating system used in target family position";
700 span_lint_and_then(cx
, MISMATCHED_TARGET_OS
, attr
.span
, &mess
, |diag
| {
701 // Avoid showing the unix suggestion multiple times in case
702 // we have more than one mismatch for unix-like systems
703 let mut unix_suggested
= false;
705 for (os
, span
) in mismatched
{
706 let sugg
= format
!("target_os = \"{}\"", os
);
707 diag
.span_suggestion(span
, "try", sugg
, Applicability
::MaybeIncorrect
);
709 if !unix_suggested
&& is_unix(os
) {
710 diag
.help("Did you mean `unix`?");
711 unix_suggested
= true;