1 //! Lints in the Rust compiler.
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main compiler.
7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
8 //! Then add code to emit the new lint in the appropriate circumstances.
9 //! You can do that in an existing `LintPass` if it makes sense, or in a
10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
11 //! compiler. Only do the latter if the check can't be written cleanly as a
12 //! `LintPass` (also, note that such lints will need to be defined in
13 //! `rustc_session::lint::builtin`, not here).
15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
18 //! with a `pub fn new()`.
20 //! If you define a new `LateLintPass`, you will also need to add it to the
21 //! `late_lint_methods!` invocation in `lib.rs`.
24 types::{transparent_newtype_field, CItemKind},
25 EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
28 use rustc_ast::tokenstream::{TokenStream, TokenTree};
29 use rustc_ast::visit::{FnCtxt, FnKind};
30 use rustc_ast::{self as ast, *};
31 use rustc_ast_pretty::pprust::{self, expr_to_string};
32 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
33 use rustc_data_structures::stack::ensure_sufficient_stack;
34 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
35 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
37 use rustc_hir::def::{DefKind, Res};
38 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
39 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
40 use rustc_hir::{HirId, Node};
41 use rustc_index::vec::Idx;
42 use rustc_middle::lint::LintDiagnosticBuilder;
43 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
44 use rustc_middle::ty::print::with_no_trimmed_paths;
45 use rustc_middle::ty::subst::{GenericArgKind, Subst};
46 use rustc_middle::ty::Instance;
47 use rustc_middle::ty::{self, Ty, TyCtxt};
48 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
49 use rustc_span::edition::Edition;
50 use rustc_span::source_map::Spanned;
51 use rustc_span::symbol::{kw, sym, Ident, Symbol};
52 use rustc_span::{BytePos, InnerSpan, MultiSpan, Span};
53 use rustc_target::abi::VariantIdx;
54 use rustc_trait_selection::traits::misc::can_type_implement_copy;
56 use crate::nonstandard_style::{method_context, MethodLateContext};
59 use tracing::{debug, trace};
61 // hardwired lints from librustc_middle
62 pub use rustc_session::lint::builtin::*;
65 /// The `while_true` lint detects `while true { }`.
79 /// `while true` should be replaced with `loop`. A `loop` expression is
80 /// the preferred way to write an infinite loop because it more directly
81 /// expresses the intent of the loop.
84 "suggest using `loop { }` instead of `while true { }`"
87 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
89 /// Traverse through any amount of parenthesis and return the first non-parens expression.
90 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
91 while let ast::ExprKind::Paren(sub) = &expr.kind {
97 impl EarlyLintPass for WhileTrue {
98 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
99 if let ast::ExprKind::While(cond, _, label) = &e.kind {
100 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
101 if let ast::LitKind::Bool(true) = lit.kind {
102 if !lit.span.from_expansion() {
103 let msg = "denote infinite loops with `loop { ... }`";
104 let condition_span = e.span.with_hi(cond.span.hi());
105 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
107 .span_suggestion_short(
112 label.map_or_else(String::new, |label| format!(
117 Applicability::MachineApplicable,
129 /// The `box_pointers` lints use of the Box type.
133 /// ```rust,compile_fail
134 /// #![deny(box_pointers)]
144 /// This lint is mostly historical, and not particularly useful. `Box<T>`
145 /// used to be built into the language, and the only way to do heap
146 /// allocation. Today's Rust can call into other allocators, etc.
149 "use of owned (Box type) heap memory"
152 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
155 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
156 for leaf in ty.walk() {
157 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
158 if leaf_ty.is_box() {
159 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
160 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
168 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
169 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
171 hir::ItemKind::Fn(..)
172 | hir::ItemKind::TyAlias(..)
173 | hir::ItemKind::Enum(..)
174 | hir::ItemKind::Struct(..)
175 | hir::ItemKind::Union(..) => {
176 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
181 // If it's a struct, we also have to check the fields' types
183 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
184 for struct_field in struct_def.fields() {
185 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
186 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
193 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
194 let ty = cx.typeck_results().node_type(e.hir_id);
195 self.check_heap_type(cx, e.span, ty);
200 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
201 /// instead of `Struct { x }` in a pattern.
219 /// Point { x: x, y: y } => (),
228 /// The preferred style is to avoid the repetition of specifying both the
229 /// field name and the binding name if both identifiers are the same.
230 NON_SHORTHAND_FIELD_PATTERNS,
232 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
235 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
237 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
238 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
239 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
244 .expect("struct pattern type is not an ADT")
245 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
246 for fieldpat in field_pats {
247 if fieldpat.is_shorthand {
250 if fieldpat.span.from_expansion() {
251 // Don't lint if this is a macro expansion: macro authors
252 // shouldn't have to worry about this kind of style issue
256 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
257 if cx.tcx.find_field_index(ident, &variant)
258 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
260 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
262 .build(&format!("the `{}:` in this pattern is redundant", ident));
263 let binding = match binding_annot {
264 hir::BindingAnnotation::Unannotated => None,
265 hir::BindingAnnotation::Mutable => Some("mut"),
266 hir::BindingAnnotation::Ref => Some("ref"),
267 hir::BindingAnnotation::RefMut => Some("ref mut"),
269 let ident = if let Some(binding) = binding {
270 format!("{} {}", binding, ident)
276 "use shorthand field pattern",
278 Applicability::MachineApplicable,
290 /// The `unsafe_code` lint catches usage of `unsafe` code.
294 /// ```rust,compile_fail
295 /// #![deny(unsafe_code)]
307 /// This lint is intended to restrict the usage of `unsafe`, which can be
308 /// difficult to use correctly.
311 "usage of `unsafe` code"
314 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
319 cx: &EarlyContext<'_>,
321 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
323 // This comes from a macro that has `#[allow_internal_unsafe]`.
324 if span.allows_unsafe() {
328 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
331 fn report_overriden_symbol_name(&self, cx: &EarlyContext<'_>, span: Span, msg: &str) {
332 self.report_unsafe(cx, span, |lint| {
335 "the linker's behavior with multiple libraries exporting duplicate symbol \
336 names is undefined and Rust cannot provide guarantees when you manually \
344 impl EarlyLintPass for UnsafeCode {
345 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
346 if attr.has_name(sym::allow_internal_unsafe) {
347 self.report_unsafe(cx, attr.span, |lint| {
349 "`allow_internal_unsafe` allows defining \
350 macros using unsafe without triggering \
351 the `unsafe_code` lint at their call site",
358 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
359 if let ast::ExprKind::Block(ref blk, _) = e.kind {
360 // Don't warn about generated blocks; that'll just pollute the output.
361 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
362 self.report_unsafe(cx, blk.span, |lint| {
363 lint.build("usage of an `unsafe` block").emit()
369 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
371 ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => self
372 .report_unsafe(cx, it.span, |lint| {
373 lint.build("declaration of an `unsafe` trait").emit()
376 ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => self
377 .report_unsafe(cx, it.span, |lint| {
378 lint.build("implementation of an `unsafe` trait").emit()
381 ast::ItemKind::Fn(..) => {
382 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
383 self.report_overriden_symbol_name(
386 "declaration of a `no_mangle` function",
389 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
390 self.report_overriden_symbol_name(
393 "declaration of a function with `export_name`",
398 ast::ItemKind::Static(..) => {
399 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
400 self.report_overriden_symbol_name(
403 "declaration of a `no_mangle` static",
406 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
407 self.report_overriden_symbol_name(
410 "declaration of a static with `export_name`",
419 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
420 if let ast::AssocItemKind::Fn(..) = it.kind {
421 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
422 self.report_overriden_symbol_name(
425 "declaration of a `no_mangle` method",
428 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
429 self.report_overriden_symbol_name(
432 "declaration of a method with `export_name`",
438 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
442 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
447 let msg = match ctxt {
448 FnCtxt::Foreign => return,
449 FnCtxt::Free => "declaration of an `unsafe` function",
450 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
451 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
453 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
459 /// The `missing_docs` lint detects missing documentation for public items.
463 /// ```rust,compile_fail
464 /// #![deny(missing_docs)]
472 /// This lint is intended to ensure that a library is well-documented.
473 /// Items without documentation can be difficult for users to understand
474 /// how to use properly.
476 /// This lint is "allow" by default because it can be noisy, and not all
477 /// projects may want to enforce everything to be documented.
480 "detects missing documentation for public members",
481 report_in_external_macro
484 pub struct MissingDoc {
485 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
486 doc_hidden_stack: Vec<bool>,
488 /// Private traits or trait items that leaked through. Don't check their methods.
489 private_traits: FxHashSet<hir::HirId>,
492 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
494 fn has_doc(attr: &ast::Attribute) -> bool {
495 if attr.is_doc_comment() {
499 if !attr.has_name(sym::doc) {
503 if attr.value_str().is_some() {
507 if let Some(list) = attr.meta_item_list() {
509 if meta.has_name(sym::hidden) {
519 pub fn new() -> MissingDoc {
520 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
523 fn doc_hidden(&self) -> bool {
524 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
527 fn check_missing_docs_attrs(
529 cx: &LateContext<'_>,
532 article: &'static str,
535 // If we're building a test harness, then warning about
536 // documentation is probably not really relevant right now.
537 if cx.sess().opts.test {
541 // `#[doc(hidden)]` disables missing_docs check.
542 if self.doc_hidden() {
546 // Only check publicly-visible items, using the result from the privacy pass.
547 // It's an option so the crate root can also use this function (it doesn't
549 if def_id != CRATE_DEF_ID {
550 if !cx.access_levels.is_exported(def_id) {
555 let attrs = cx.tcx.get_attrs(def_id.to_def_id());
556 let has_doc = attrs.iter().any(has_doc);
560 cx.tcx.sess.source_map().guess_head_span(sp),
562 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
569 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
570 fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
571 let doc_hidden = self.doc_hidden()
572 || attrs.iter().any(|attr| {
573 attr.has_name(sym::doc)
574 && match attr.meta_item_list() {
576 Some(l) => attr::list_contains_name(&l, sym::hidden),
579 self.doc_hidden_stack.push(doc_hidden);
582 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
583 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
586 fn check_crate(&mut self, cx: &LateContext<'_>) {
587 self.check_missing_docs_attrs(
590 cx.tcx.def_span(CRATE_DEF_ID),
596 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
598 hir::ItemKind::Trait(.., trait_item_refs) => {
599 // Issue #11592: traits are always considered exported, even when private.
600 if let hir::VisibilityKind::Inherited = it.vis.node {
601 self.private_traits.insert(it.hir_id());
602 for trait_item_ref in trait_item_refs {
603 self.private_traits.insert(trait_item_ref.id.hir_id());
608 hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref trait_ref), items, .. }) => {
609 // If the trait is private, add the impl items to `private_traits` so they don't get
610 // reported for missing docs.
611 let real_trait = trait_ref.path.res.def_id();
612 let Some(def_id) = real_trait.as_local() else { return };
613 let Some(Node::Item(item)) = cx.tcx.hir().find_by_def_id(def_id) else { return };
614 if let hir::VisibilityKind::Inherited = item.vis.node {
615 for impl_item_ref in items {
616 self.private_traits.insert(impl_item_ref.id.hir_id());
622 hir::ItemKind::TyAlias(..)
623 | hir::ItemKind::Fn(..)
624 | hir::ItemKind::Macro(..)
625 | hir::ItemKind::Mod(..)
626 | hir::ItemKind::Enum(..)
627 | hir::ItemKind::Struct(..)
628 | hir::ItemKind::Union(..)
629 | hir::ItemKind::Const(..)
630 | hir::ItemKind::Static(..) => {}
635 let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
637 self.check_missing_docs_attrs(cx, it.def_id, it.span, article, desc);
640 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
641 if self.private_traits.contains(&trait_item.hir_id()) {
645 let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
647 self.check_missing_docs_attrs(cx, trait_item.def_id, trait_item.span, article, desc);
650 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
651 // If the method is an impl for a trait, don't doc.
652 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
656 // If the method is an impl for an item with docs_hidden, don't doc.
657 if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
658 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
659 let impl_ty = cx.tcx.type_of(parent);
660 let outerdef = match impl_ty.kind() {
661 ty::Adt(def, _) => Some(def.did),
662 ty::Foreign(def_id) => Some(*def_id),
665 let is_hidden = match outerdef {
666 Some(id) => cx.tcx.is_doc_hidden(id),
674 let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
675 self.check_missing_docs_attrs(cx, impl_item.def_id, impl_item.span, article, desc);
678 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
679 let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
680 self.check_missing_docs_attrs(cx, foreign_item.def_id, foreign_item.span, article, desc);
683 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
684 if !sf.is_positional() {
685 let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
686 self.check_missing_docs_attrs(cx, def_id, sf.span, "a", "struct field")
690 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
691 self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), v.span, "a", "variant");
696 /// The `missing_copy_implementations` lint detects potentially-forgotten
697 /// implementations of [`Copy`].
699 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
703 /// ```rust,compile_fail
704 /// #![deny(missing_copy_implementations)]
715 /// Historically (before 1.0), types were automatically marked as `Copy`
716 /// if possible. This was changed so that it required an explicit opt-in
717 /// by implementing the `Copy` trait. As part of this change, a lint was
718 /// added to alert if a copyable type was not marked `Copy`.
720 /// This lint is "allow" by default because this code isn't bad; it is
721 /// common to write newtypes like this specifically so that a `Copy` type
722 /// is no longer `Copy`. `Copy` types can result in unintended copies of
723 /// large data which can impact performance.
724 pub MISSING_COPY_IMPLEMENTATIONS,
726 "detects potentially-forgotten implementations of `Copy`"
729 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
731 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
732 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
733 if !cx.access_levels.is_reachable(item.def_id) {
736 let (def, ty) = match item.kind {
737 hir::ItemKind::Struct(_, ref ast_generics) => {
738 if !ast_generics.params.is_empty() {
741 let def = cx.tcx.adt_def(item.def_id);
742 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
744 hir::ItemKind::Union(_, ref ast_generics) => {
745 if !ast_generics.params.is_empty() {
748 let def = cx.tcx.adt_def(item.def_id);
749 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
751 hir::ItemKind::Enum(_, ref ast_generics) => {
752 if !ast_generics.params.is_empty() {
755 let def = cx.tcx.adt_def(item.def_id);
756 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
760 if def.has_dtor(cx.tcx) {
763 let param_env = ty::ParamEnv::empty();
764 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
767 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
768 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
770 "type could implement `Copy`; consider adding `impl \
780 /// The `missing_debug_implementations` lint detects missing
781 /// implementations of [`fmt::Debug`].
783 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
787 /// ```rust,compile_fail
788 /// #![deny(missing_debug_implementations)]
797 /// Having a `Debug` implementation on all types can assist with
798 /// debugging, as it provides a convenient way to format and display a
799 /// value. Using the `#[derive(Debug)]` attribute will automatically
800 /// generate a typical implementation, or a custom implementation can be
801 /// added by manually implementing the `Debug` trait.
803 /// This lint is "allow" by default because adding `Debug` to all types can
804 /// have a negative impact on compile time and code size. It also requires
805 /// boilerplate to be added to every type, which can be an impediment.
806 MISSING_DEBUG_IMPLEMENTATIONS,
808 "detects missing implementations of Debug"
812 pub struct MissingDebugImplementations {
813 impling_types: Option<LocalDefIdSet>,
816 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
818 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
819 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
820 if !cx.access_levels.is_reachable(item.def_id) {
825 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
829 let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
833 if self.impling_types.is_none() {
834 let mut impls = LocalDefIdSet::default();
835 cx.tcx.for_each_impl(debug, |d| {
836 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
837 if let Some(def_id) = ty_def.did.as_local() {
838 impls.insert(def_id);
843 self.impling_types = Some(impls);
844 debug!("{:?}", self.impling_types);
847 if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
848 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
850 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
851 or a manual implementation",
852 cx.tcx.def_path_str(debug)
861 /// The `anonymous_parameters` lint detects anonymous parameters in trait
866 /// ```rust,edition2015,compile_fail
867 /// #![deny(anonymous_parameters)]
879 /// This syntax is mostly a historical accident, and can be worked around
880 /// quite easily by adding an `_` pattern or a descriptive identifier:
884 /// fn foo(_: usize);
888 /// This syntax is now a hard error in the 2018 edition. In the 2015
889 /// edition, this lint is "warn" by default. This lint
890 /// enables the [`cargo fix`] tool with the `--edition` flag to
891 /// automatically transition old code from the 2015 edition to 2018. The
892 /// tool will run this lint and automatically apply the
893 /// suggested fix from the compiler (which is to add `_` to each
894 /// parameter). This provides a completely automated way to update old
895 /// code for a new edition. See [issue #41686] for more details.
897 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
898 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
899 pub ANONYMOUS_PARAMETERS,
901 "detects anonymous parameters",
902 @future_incompatible = FutureIncompatibleInfo {
903 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
904 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
909 /// Checks for use of anonymous parameters (RFC 1685).
910 AnonymousParameters => [ANONYMOUS_PARAMETERS]
913 impl EarlyLintPass for AnonymousParameters {
914 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
915 if cx.sess.edition() != Edition::Edition2015 {
916 // This is a hard error in future editions; avoid linting and erroring
919 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
920 for arg in sig.decl.inputs.iter() {
921 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
922 if ident.name == kw::Empty {
923 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
924 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
926 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
927 (snip.as_str(), Applicability::MachineApplicable)
929 ("<type>", Applicability::HasPlaceholders)
933 "anonymous parameters are deprecated and will be \
934 removed in the next edition",
938 "try naming the parameter or explicitly \
940 format!("_: {}", ty_snip),
952 /// Check for use of attributes which have been deprecated.
954 pub struct DeprecatedAttr {
955 // This is not free to compute, so we want to keep it around, rather than
956 // compute it for every attribute.
957 depr_attrs: Vec<&'static BuiltinAttribute>,
960 impl_lint_pass!(DeprecatedAttr => []);
962 impl DeprecatedAttr {
963 pub fn new() -> DeprecatedAttr {
964 DeprecatedAttr { depr_attrs: deprecated_attributes() }
968 fn lint_deprecated_attr(
969 cx: &EarlyContext<'_>,
970 attr: &ast::Attribute,
972 suggestion: Option<&str>,
974 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
976 .span_suggestion_short(
978 suggestion.unwrap_or("remove this attribute"),
980 Applicability::MachineApplicable,
986 impl EarlyLintPass for DeprecatedAttr {
987 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
988 for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
989 if attr.ident().map(|ident| ident.name) == Some(*name) {
990 if let &AttributeGate::Gated(
991 Stability::Deprecated(link, suggestion),
998 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
999 lint_deprecated_attr(cx, attr, &msg, suggestion);
1004 if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
1005 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
1006 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
1007 lint_deprecated_attr(cx, attr, &msg, None);
1012 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1013 use rustc_ast::token::CommentKind;
1015 let mut attrs = attrs.iter().peekable();
1017 // Accumulate a single span for sugared doc comments.
1018 let mut sugared_span: Option<Span> = None;
1020 while let Some(attr) = attrs.next() {
1021 let is_doc_comment = attr.is_doc_comment();
1024 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1027 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1031 let span = sugared_span.take().unwrap_or(attr.span);
1033 if is_doc_comment || attr.has_name(sym::doc) {
1034 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1035 let mut err = lint.build("unused doc comment");
1038 format!("rustdoc does not generate documentation for {}", node_kind),
1041 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1042 err.help("use `//` for a plain comment");
1044 AttrKind::DocComment(CommentKind::Block, _) => {
1045 err.help("use `/* */` for a plain comment");
1054 impl EarlyLintPass for UnusedDocComment {
1055 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1056 let kind = match stmt.kind {
1057 ast::StmtKind::Local(..) => "statements",
1058 // Disabled pending discussion in #78306
1059 ast::StmtKind::Item(..) => return,
1060 // expressions will be reported by `check_expr`.
1061 ast::StmtKind::Empty
1062 | ast::StmtKind::Semi(_)
1063 | ast::StmtKind::Expr(_)
1064 | ast::StmtKind::MacCall(_) => return,
1067 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1070 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1071 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1072 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1075 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1076 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1079 fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1080 warn_if_doc(cx, param.ident.span, "generic parameters", ¶m.attrs);
1085 /// The `no_mangle_const_items` lint detects any `const` items with the
1086 /// [`no_mangle` attribute].
1088 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1092 /// ```rust,compile_fail
1094 /// const FOO: i32 = 5;
1101 /// Constants do not have their symbols exported, and therefore, this
1102 /// probably means you meant to use a [`static`], not a [`const`].
1104 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1105 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1106 NO_MANGLE_CONST_ITEMS,
1108 "const items will not have their symbols exported"
1112 /// The `no_mangle_generic_items` lint detects generic items that must be
1119 /// fn foo<T>(t: T) {
1128 /// A function with generics must have its symbol mangled to accommodate
1129 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1130 /// this situation, and should be removed.
1132 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1133 NO_MANGLE_GENERIC_ITEMS,
1135 "generic items must be mangled"
1138 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1140 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1141 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1142 let attrs = cx.tcx.hir().attrs(it.hir_id());
1143 let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1144 impl_generics: Option<&hir::Generics<'_>>,
1145 generics: &hir::Generics<'_>,
1148 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1151 GenericParamKind::Lifetime { .. } => {}
1152 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1153 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
1154 lint.build("functions generic over types or consts must be mangled")
1155 .span_suggestion_short(
1156 no_mangle_attr.span,
1157 "remove this attribute",
1159 // Use of `#[no_mangle]` suggests FFI intent; correct
1160 // fix may be to monomorphize source by hand
1161 Applicability::MaybeIncorrect,
1171 hir::ItemKind::Fn(.., ref generics, _) => {
1172 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1173 check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1176 hir::ItemKind::Const(..) => {
1177 if cx.sess().contains_name(attrs, sym::no_mangle) {
1178 // Const items do not refer to a particular location in memory, and therefore
1179 // don't have anything to attach a symbol to
1180 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1181 let msg = "const items should never be `#[no_mangle]`";
1182 let mut err = lint.build(msg);
1184 // account for "pub const" (#45562)
1189 .span_to_snippet(it.span)
1190 .map(|snippet| snippet.find("const").unwrap_or(0))
1191 .unwrap_or(0) as u32;
1192 // `const` is 5 chars
1193 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1194 err.span_suggestion(
1196 "try a static value",
1197 "pub static".to_owned(),
1198 Applicability::MachineApplicable,
1204 hir::ItemKind::Impl(hir::Impl { ref generics, items, .. }) => {
1206 if let hir::AssocItemKind::Fn { .. } = it.kind {
1207 if let Some(no_mangle_attr) = cx
1209 .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1211 check_no_mangle_on_generic_fn(
1214 cx.tcx.hir().get_generics(it.id.def_id).unwrap(),
1227 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1228 /// T` because it is [undefined behavior].
1230 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1234 /// ```rust,compile_fail
1236 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1244 /// Certain assumptions are made about aliasing of data, and this transmute
1245 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1247 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1250 "mutating transmuted &mut T from &T may cause undefined behavior"
1253 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1255 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1256 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1257 use rustc_target::spec::abi::Abi::RustIntrinsic;
1258 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1259 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1261 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1262 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1263 consider instead using an UnsafeCell";
1264 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
1268 fn get_transmute_from_to<'tcx>(
1269 cx: &LateContext<'tcx>,
1270 expr: &hir::Expr<'_>,
1271 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1272 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1273 cx.qpath_res(qpath, expr.hir_id)
1277 if let Res::Def(DefKind::Fn, did) = def {
1278 if !def_id_is_transmute(cx, did) {
1281 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1282 let from = sig.inputs().skip_binder()[0];
1283 let to = sig.output().skip_binder();
1284 return Some((from, to));
1289 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1290 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
1291 && cx.tcx.item_name(def_id) == sym::transmute
1297 /// The `unstable_features` is deprecated and should no longer be used.
1300 "enabling unstable features (deprecated. do not use)"
1304 /// Forbids using the `#[feature(...)]` attribute
1305 UnstableFeatures => [UNSTABLE_FEATURES]
1308 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1309 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1310 if attr.has_name(sym::feature) {
1311 if let Some(items) = attr.meta_item_list() {
1313 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1314 lint.build("unstable feature").emit()
1323 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1328 /// ```rust,compile_fail
1329 /// #![deny(unreachable_pub)]
1341 /// A bare `pub` visibility may be misleading if the item is not actually
1342 /// publicly exported from the crate. The `pub(crate)` visibility is
1343 /// recommended to be used instead, which more clearly expresses the intent
1344 /// that the item is only visible within its own crate.
1346 /// This lint is "allow" by default because it will trigger for a large
1347 /// amount existing Rust code, and has some false-positives. Eventually it
1348 /// is desired for this to become warn-by-default.
1349 pub UNREACHABLE_PUB,
1351 "`pub` items not reachable from crate root"
1355 /// Lint for items marked `pub` that aren't reachable from other crates.
1356 UnreachablePub => [UNREACHABLE_PUB]
1359 impl UnreachablePub {
1362 cx: &LateContext<'_>,
1365 vis: &hir::Visibility<'_>,
1369 let mut applicability = Applicability::MachineApplicable;
1371 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(def_id) => {
1372 if span.from_expansion() {
1373 applicability = Applicability::MaybeIncorrect;
1375 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1376 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1377 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1378 let replacement = if cx.tcx.features().crate_visibility_modifier {
1385 err.span_suggestion(
1387 "consider restricting its visibility",
1392 err.help("or consider exporting it for use by other crates");
1402 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1403 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1404 self.perform_lint(cx, "item", item.def_id, &item.vis, item.span, true);
1407 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1411 foreign_item.def_id,
1418 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1419 let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1420 self.perform_lint(cx, "field", def_id, &field.vis, field.span, false);
1423 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1424 self.perform_lint(cx, "item", impl_item.def_id, &impl_item.vis, impl_item.span, false);
1429 /// The `type_alias_bounds` lint detects bounds in type aliases.
1434 /// type SendVec<T: Send> = Vec<T>;
1441 /// The trait bounds in a type alias are currently ignored, and should not
1442 /// be included to avoid confusion. This was previously allowed
1443 /// unintentionally; this may become a hard error in the future.
1446 "bounds in type aliases are not enforced"
1450 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1451 /// They are relevant when using associated types, but otherwise neither checked
1452 /// at definition site nor enforced at use site.
1453 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1456 impl TypeAliasBounds {
1457 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1459 hir::QPath::TypeRelative(ref ty, _) => {
1460 // If this is a type variable, we found a `T::Assoc`.
1462 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1463 matches!(path.res, Res::Def(DefKind::TyParam, _))
1468 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1472 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1473 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1474 // bound. Let's see if this type does that.
1476 // We use a HIR visitor to walk the type.
1477 use rustc_hir::intravisit::{self, Visitor};
1478 struct WalkAssocTypes<'a, 'db> {
1479 err: &'a mut DiagnosticBuilder<'db>,
1481 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1482 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1483 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1486 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1487 associated types in type aliases",
1490 intravisit::walk_qpath(self, qpath, id, span)
1494 // Let's go for a walk!
1495 let mut visitor = WalkAssocTypes { err };
1496 visitor.visit_ty(ty);
1500 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1501 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1502 let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1505 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1506 // Bounds are respected for `type X = impl Trait`
1509 let mut suggested_changing_assoc_types = false;
1510 // There must not be a where clause
1511 if !type_alias_generics.where_clause.predicates.is_empty() {
1515 let mut err = lint.build("where clauses are not enforced in type aliases");
1516 let spans: Vec<_> = type_alias_generics
1520 .map(|pred| pred.span())
1522 err.set_span(spans);
1523 err.span_suggestion(
1524 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1525 "the clause will not be checked when the type alias is used, and should be removed",
1527 Applicability::MachineApplicable,
1529 if !suggested_changing_assoc_types {
1530 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1531 suggested_changing_assoc_types = true;
1537 // The parameters must not have bounds
1538 for param in type_alias_generics.params.iter() {
1539 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1540 let suggestion = spans
1543 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1544 (start.to(*sp), String::new())
1547 if !spans.is_empty() {
1548 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1550 lint.build("bounds on generic parameters are not enforced in type aliases");
1551 let msg = "the bound will not be checked when the type alias is used, \
1552 and should be removed";
1553 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1554 if !suggested_changing_assoc_types {
1555 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1556 suggested_changing_assoc_types = true;
1566 /// Lint constants that are erroneous.
1567 /// Without this lint, we might not get any diagnostic if the constant is
1568 /// unused within this crate, even though downstream crates can't use it
1569 /// without producing an error.
1570 UnusedBrokenConst => []
1573 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1574 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1576 hir::ItemKind::Const(_, body_id) => {
1577 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1578 // trigger the query once for all constants since that will already report the errors
1579 // FIXME: Use ensure here
1580 let _ = cx.tcx.const_eval_poly(def_id);
1582 hir::ItemKind::Static(_, _, body_id) => {
1583 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1584 // FIXME: Use ensure here
1585 let _ = cx.tcx.eval_static_initializer(def_id);
1593 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1594 /// any type parameters.
1599 /// #![feature(trivial_bounds)]
1600 /// pub struct A where i32: Copy;
1607 /// Usually you would not write a trait bound that you know is always
1608 /// true, or never true. However, when using macros, the macro may not
1609 /// know whether or not the constraint would hold or not at the time when
1610 /// generating the code. Currently, the compiler does not alert you if the
1611 /// constraint is always true, and generates an error if it is never true.
1612 /// The `trivial_bounds` feature changes this to be a warning in both
1613 /// cases, giving macros more freedom and flexibility to generate code,
1614 /// while still providing a signal when writing non-macro code that
1615 /// something is amiss.
1617 /// See [RFC 2056] for more details. This feature is currently only
1618 /// available on the nightly channel, see [tracking issue #48214].
1620 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1621 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1624 "these bounds don't depend on an type parameters"
1628 /// Lint for trait and lifetime bounds that don't depend on type parameters
1629 /// which either do nothing, or stop the item from being used.
1630 TrivialConstraints => [TRIVIAL_BOUNDS]
1633 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1634 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1635 use rustc_middle::ty::fold::TypeFoldable;
1636 use rustc_middle::ty::PredicateKind::*;
1638 if cx.tcx.features().trivial_bounds {
1639 let predicates = cx.tcx.predicates_of(item.def_id);
1640 for &(predicate, span) in predicates.predicates {
1641 let predicate_kind_name = match predicate.kind().skip_binder() {
1642 Trait(..) => "trait",
1644 RegionOutlives(..) => "lifetime",
1646 // Ignore projections, as they can only be global
1647 // if the trait bound is global
1649 // Ignore bounds that a user can't type
1655 ConstEvaluatable(..) |
1657 TypeWellFormedFromEnv(..) => continue,
1659 if predicate.is_global() {
1660 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1661 lint.build(&format!(
1662 "{} bound {} does not depend on any type \
1663 or lifetime parameters",
1664 predicate_kind_name, predicate
1675 /// Does nothing as a lint pass, but registers some `Lint`s
1676 /// which are used by other parts of the compiler.
1680 NON_SHORTHAND_FIELD_PATTERNS,
1683 MISSING_COPY_IMPLEMENTATIONS,
1684 MISSING_DEBUG_IMPLEMENTATIONS,
1685 ANONYMOUS_PARAMETERS,
1686 UNUSED_DOC_COMMENTS,
1687 NO_MANGLE_CONST_ITEMS,
1688 NO_MANGLE_GENERIC_ITEMS,
1698 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1699 /// pattern], which is deprecated.
1701 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1705 /// ```rust,edition2018
1717 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1718 /// confusion with the [`..` range expression]. Use the new form instead.
1720 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1721 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1723 "`...` range patterns are deprecated",
1724 @future_incompatible = FutureIncompatibleInfo {
1725 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1726 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1731 pub struct EllipsisInclusiveRangePatterns {
1732 /// If `Some(_)`, suppress all subsequent pattern
1733 /// warnings for better diagnostics.
1734 node_id: Option<ast::NodeId>,
1737 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1739 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1740 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1741 if self.node_id.is_some() {
1742 // Don't recursively warn about patterns inside range endpoints.
1746 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1748 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1749 /// corresponding to the ellipsis.
1750 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1755 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1756 ) => Some((a.as_deref(), b, *span)),
1761 let (parenthesise, endpoints) = match &pat.kind {
1762 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1763 _ => (false, matches_ellipsis_pat(pat)),
1766 if let Some((start, end, join)) = endpoints {
1767 let msg = "`...` range patterns are deprecated";
1768 let suggestion = "use `..=` for an inclusive range";
1770 self.node_id = Some(pat.id);
1771 let end = expr_to_string(&end);
1772 let replace = match start {
1773 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1774 None => format!("&(..={})", end),
1776 if join.edition() >= Edition::Edition2021 {
1778 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1779 err.span_suggestion(
1783 Applicability::MachineApplicable,
1787 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1793 Applicability::MachineApplicable,
1799 let replace = "..=".to_owned();
1800 if join.edition() >= Edition::Edition2021 {
1802 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1803 err.span_suggestion_short(
1807 Applicability::MachineApplicable,
1811 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1813 .span_suggestion_short(
1817 Applicability::MachineApplicable,
1826 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1827 if let Some(node_id) = self.node_id {
1828 if pat.id == node_id {
1836 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1837 /// that are not able to be run by the test harness because they are in a
1838 /// position where they are not nameable.
1840 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1848 /// // This test will not fail because it does not run.
1849 /// assert_eq!(1, 2);
1858 /// In order for the test harness to run a test, the test function must be
1859 /// located in a position where it can be accessed from the crate root.
1860 /// This generally means it must be defined in a module, and not anywhere
1861 /// else such as inside another function. The compiler previously allowed
1862 /// this without an error, so a lint was added as an alert that a test is
1863 /// not being used. Whether or not this should be allowed has not yet been
1864 /// decided, see [RFC 2471] and [issue #36629].
1866 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1867 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1868 UNNAMEABLE_TEST_ITEMS,
1870 "detects an item that cannot be named being marked as `#[test_case]`",
1871 report_in_external_macro
1874 pub struct UnnameableTestItems {
1875 boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1876 items_nameable: bool,
1879 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1881 impl UnnameableTestItems {
1882 pub fn new() -> Self {
1883 Self { boundary: None, items_nameable: true }
1887 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1888 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1889 if self.items_nameable {
1890 if let hir::ItemKind::Mod(..) = it.kind {
1892 self.items_nameable = false;
1893 self.boundary = Some(it.def_id);
1898 let attrs = cx.tcx.hir().attrs(it.hir_id());
1899 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1900 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1901 lint.build("cannot test inner items").emit()
1906 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1907 if !self.items_nameable && self.boundary == Some(it.def_id) {
1908 self.items_nameable = true;
1914 /// The `keyword_idents` lint detects edition keywords being used as an
1919 /// ```rust,edition2015,compile_fail
1920 /// #![deny(keyword_idents)]
1929 /// Rust [editions] allow the language to evolve without breaking
1930 /// backwards compatibility. This lint catches code that uses new keywords
1931 /// that are added to the language that are used as identifiers (such as a
1932 /// variable name, function name, etc.). If you switch the compiler to a
1933 /// new edition without updating the code, then it will fail to compile if
1934 /// you are using a new keyword as an identifier.
1936 /// You can manually change the identifiers to a non-keyword, or use a
1937 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1939 /// This lint solves the problem automatically. It is "allow" by default
1940 /// because the code is perfectly valid in older editions. The [`cargo
1941 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1942 /// and automatically apply the suggested fix from the compiler (which is
1943 /// to use a raw identifier). This provides a completely automated way to
1944 /// update old code for a new edition.
1946 /// [editions]: https://doc.rust-lang.org/edition-guide/
1947 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1948 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1951 "detects edition keywords being used as an identifier",
1952 @future_incompatible = FutureIncompatibleInfo {
1953 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1954 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1959 /// Check for uses of edition keywords used as an identifier.
1960 KeywordIdents => [KEYWORD_IDENTS]
1963 struct UnderMacro(bool);
1965 impl KeywordIdents {
1966 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1967 for tt in tokens.into_trees() {
1969 // Only report non-raw idents.
1970 TokenTree::Token(token) => {
1971 if let Some((ident, false)) = token.ident() {
1972 self.check_ident_token(cx, UnderMacro(true), ident);
1975 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1980 fn check_ident_token(
1982 cx: &EarlyContext<'_>,
1983 UnderMacro(under_macro): UnderMacro,
1986 let next_edition = match cx.sess.edition() {
1987 Edition::Edition2015 => {
1989 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1991 // rust-lang/rust#56327: Conservatively do not
1992 // attempt to report occurrences of `dyn` within
1993 // macro definitions or invocations, because `dyn`
1994 // can legitimately occur as a contextual keyword
1995 // in 2015 code denoting its 2018 meaning, and we
1996 // do not want rustfix to inject bugs into working
1997 // code by rewriting such occurrences.
1999 // But if we see `dyn` outside of a macro, we know
2000 // its precise role in the parsed AST and thus are
2001 // assured this is truly an attempt to use it as
2003 kw::Dyn if !under_macro => Edition::Edition2018,
2009 // There are no new keywords yet for the 2018 edition and beyond.
2013 // Don't lint `r#foo`.
2014 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2018 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2019 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
2022 "you can use a raw identifier to stay compatible",
2023 format!("r#{}", ident),
2024 Applicability::MachineApplicable,
2031 impl EarlyLintPass for KeywordIdents {
2032 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2033 self.check_tokens(cx, mac_def.body.inner_tokens());
2035 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2036 self.check_tokens(cx, mac.args.inner_tokens());
2038 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2039 self.check_ident_token(cx, UnderMacro(false), ident);
2043 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2045 impl ExplicitOutlivesRequirements {
2046 fn lifetimes_outliving_lifetime<'tcx>(
2047 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2049 ) -> Vec<ty::Region<'tcx>> {
2052 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2053 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
2054 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2062 fn lifetimes_outliving_type<'tcx>(
2063 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2065 ) -> Vec<ty::Region<'tcx>> {
2068 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2069 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2070 a.is_param(index).then_some(b)
2077 fn collect_outlived_lifetimes<'tcx>(
2079 param: &'tcx hir::GenericParam<'tcx>,
2081 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2082 ty_generics: &'tcx ty::Generics,
2083 ) -> Vec<ty::Region<'tcx>> {
2085 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
2088 hir::GenericParamKind::Lifetime { .. } => {
2089 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
2091 hir::GenericParamKind::Type { .. } => {
2092 Self::lifetimes_outliving_type(inferred_outlives, index)
2094 hir::GenericParamKind::Const { .. } => Vec::new(),
2098 fn collect_outlives_bound_spans<'tcx>(
2101 bounds: &hir::GenericBounds<'_>,
2102 inferred_outlives: &[ty::Region<'tcx>],
2104 ) -> Vec<(usize, Span)> {
2105 use rustc_middle::middle::resolve_lifetime::Region;
2110 .filter_map(|(i, bound)| {
2111 if let hir::GenericBound::Outlives(lifetime) = bound {
2112 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2113 Some(Region::Static) if infer_static => {
2114 inferred_outlives.iter().any(|r| matches!(r, ty::ReStatic))
2116 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2117 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
2121 is_inferred.then_some((i, bound.span()))
2129 fn consolidate_outlives_bound_spans(
2132 bounds: &hir::GenericBounds<'_>,
2133 bound_spans: Vec<(usize, Span)>,
2135 if bounds.is_empty() {
2138 if bound_spans.len() == bounds.len() {
2139 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2140 // If all bounds are inferable, we want to delete the colon, so
2141 // start from just after the parameter (span passed as argument)
2142 vec![lo.to(last_bound_span)]
2144 let mut merged = Vec::new();
2145 let mut last_merged_i = None;
2147 let mut from_start = true;
2148 for (i, bound_span) in bound_spans {
2149 match last_merged_i {
2150 // If the first bound is inferable, our span should also eat the leading `+`.
2152 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2153 last_merged_i = Some(0);
2155 // If consecutive bounds are inferable, merge their spans
2156 Some(h) if i == h + 1 => {
2157 if let Some(tail) = merged.last_mut() {
2158 // Also eat the trailing `+` if the first
2159 // more-than-one bound is inferable
2160 let to_span = if from_start && i < bounds.len() {
2161 bounds[i + 1].span().shrink_to_lo()
2165 *tail = tail.to(to_span);
2166 last_merged_i = Some(i);
2168 bug!("another bound-span visited earlier");
2172 // When we find a non-inferable bound, subsequent inferable bounds
2173 // won't be consecutive from the start (and we'll eat the leading
2174 // `+` rather than the trailing one)
2176 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2177 last_merged_i = Some(i);
2186 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2187 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2188 use rustc_middle::middle::resolve_lifetime::Region;
2190 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
2191 let def_id = item.def_id;
2192 if let hir::ItemKind::Struct(_, ref hir_generics)
2193 | hir::ItemKind::Enum(_, ref hir_generics)
2194 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2196 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2197 if inferred_outlives.is_empty() {
2201 let ty_generics = cx.tcx.generics_of(def_id);
2203 let mut bound_count = 0;
2204 let mut lint_spans = Vec::new();
2206 for param in hir_generics.params {
2207 let has_lifetime_bounds = param
2210 .any(|bound| matches!(bound, hir::GenericBound::Outlives(_)));
2211 if !has_lifetime_bounds {
2215 let relevant_lifetimes =
2216 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
2217 if relevant_lifetimes.is_empty() {
2221 let bound_spans = self.collect_outlives_bound_spans(
2224 &relevant_lifetimes,
2227 bound_count += bound_spans.len();
2228 lint_spans.extend(self.consolidate_outlives_bound_spans(
2229 param.span.shrink_to_hi(),
2235 let mut where_lint_spans = Vec::new();
2236 let mut dropped_predicate_count = 0;
2237 let num_predicates = hir_generics.where_clause.predicates.len();
2238 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
2239 let (relevant_lifetimes, bounds, span) = match where_predicate {
2240 hir::WherePredicate::RegionPredicate(predicate) => {
2241 if let Some(Region::EarlyBound(index, ..)) =
2242 cx.tcx.named_region(predicate.lifetime.hir_id)
2245 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2253 hir::WherePredicate::BoundPredicate(predicate) => {
2254 // FIXME we can also infer bounds on associated types,
2255 // and should check for them here.
2256 match predicate.bounded_ty.kind {
2257 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2258 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2261 let index = ty_generics.param_def_id_to_index[&def_id];
2263 Self::lifetimes_outliving_type(inferred_outlives, index),
2275 if relevant_lifetimes.is_empty() {
2279 let bound_spans = self.collect_outlives_bound_spans(
2282 &relevant_lifetimes,
2285 bound_count += bound_spans.len();
2287 let drop_predicate = bound_spans.len() == bounds.len();
2289 dropped_predicate_count += 1;
2292 // If all the bounds on a predicate were inferable and there are
2293 // further predicates, we want to eat the trailing comma.
2294 if drop_predicate && i + 1 < num_predicates {
2295 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
2296 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2298 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2299 span.shrink_to_lo(),
2306 // If all predicates are inferable, drop the entire clause
2307 // (including the `where`)
2308 if num_predicates > 0 && dropped_predicate_count == num_predicates {
2309 let where_span = hir_generics
2312 .expect("span of (nonempty) where clause should exist");
2313 // Extend the where clause back to the closing `>` of the
2314 // generics, except for tuple struct, which have the `where`
2315 // after the fields of the struct.
2316 let full_where_span =
2317 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2320 hir_generics.span.shrink_to_hi().to(where_span)
2322 lint_spans.push(full_where_span);
2324 lint_spans.extend(where_lint_spans);
2327 if !lint_spans.is_empty() {
2328 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2329 lint.build("outlives requirements can be inferred")
2330 .multipart_suggestion(
2331 if bound_count == 1 {
2334 "remove these bounds"
2338 .map(|span| (span, "".to_owned()))
2339 .collect::<Vec<_>>(),
2340 Applicability::MachineApplicable,
2350 /// The `incomplete_features` lint detects unstable features enabled with
2351 /// the [`feature` attribute] that may function improperly in some or all
2354 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2359 /// #![feature(generic_const_exprs)]
2366 /// Although it is encouraged for people to experiment with unstable
2367 /// features, some of them are known to be incomplete or faulty. This lint
2368 /// is a signal that the feature has not yet been finished, and you may
2369 /// experience problems with it.
2370 pub INCOMPLETE_FEATURES,
2372 "incomplete features that may function improperly in some or all cases"
2376 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2377 IncompleteFeatures => [INCOMPLETE_FEATURES]
2380 impl EarlyLintPass for IncompleteFeatures {
2381 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2382 let features = cx.sess.features_untracked();
2384 .declared_lang_features
2386 .map(|(name, span, _)| (name, span))
2387 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2388 .filter(|(&name, _)| features.incomplete(name))
2389 .for_each(|(&name, &span)| {
2390 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2391 let mut builder = lint.build(&format!(
2392 "the feature `{}` is incomplete and may not be safe to use \
2393 and/or cause compiler crashes",
2396 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2397 builder.note(&format!(
2398 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
2399 for more information",
2403 if HAS_MIN_FEATURES.contains(&name) {
2404 builder.help(&format!(
2405 "consider using `min_{}` instead, which is more stable and complete",
2415 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2418 /// The `invalid_value` lint detects creating a value that is not valid,
2419 /// such as a null reference.
2424 /// # #![allow(unused)]
2426 /// let x: &'static i32 = std::mem::zeroed();
2434 /// In some situations the compiler can detect that the code is creating
2435 /// an invalid value, which should be avoided.
2437 /// In particular, this lint will check for improper use of
2438 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2439 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2440 /// lint should provide extra information to indicate what the problem is
2441 /// and a possible solution.
2443 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2444 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2445 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2446 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2447 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2450 "an invalid value is being created (such as a null reference)"
2453 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2455 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2456 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2457 #[derive(Debug, Copy, Clone, PartialEq)]
2463 /// Information about why a type cannot be initialized this way.
2464 /// Contains an error message and optionally a span to point at.
2465 type InitError = (String, Option<Span>);
2467 /// Test if this constant is all-0.
2468 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2469 use hir::ExprKind::*;
2470 use rustc_ast::LitKind::*;
2473 if let Int(i, _) = lit.node {
2479 Tup(tup) => tup.iter().all(is_zero),
2484 /// Determine if this expression is a "dangerous initialization".
2485 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2486 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2487 // Find calls to `mem::{uninitialized,zeroed}` methods.
2488 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2489 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2490 match cx.tcx.get_diagnostic_name(def_id) {
2491 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2492 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2493 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2497 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
2498 // Find problematic calls to `MaybeUninit::assume_init`.
2499 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2500 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2501 // This is a call to *some* method named `assume_init`.
2502 // See if the `self` parameter is one of the dangerous constructors.
2503 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2504 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2505 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2506 match cx.tcx.get_diagnostic_name(def_id) {
2507 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2508 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2519 /// Test if this enum has several actually "existing" variants.
2520 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2521 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
2522 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2523 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
2524 existing_variants > 1
2527 /// Return `Some` only if we are sure this type does *not*
2528 /// allow zero initialization.
2529 fn ty_find_init_error<'tcx>(
2533 ) -> Option<InitError> {
2534 use rustc_middle::ty::TyKind::*;
2536 // Primitive types that don't like 0 as a value.
2537 Ref(..) => Some(("references must be non-null".to_string(), None)),
2538 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2539 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2540 Never => Some(("the `!` type has no valid value".to_string(), None)),
2541 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2542 // raw ptr to dyn Trait
2544 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2546 // Primitive types with other constraints.
2547 Bool if init == InitKind::Uninit => {
2548 Some(("booleans must be either `true` or `false`".to_string(), None))
2550 Char if init == InitKind::Uninit => {
2551 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2553 // Recurse and checks for some compound types.
2554 Adt(adt_def, substs) if !adt_def.is_union() => {
2555 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2556 use std::ops::Bound;
2557 match tcx.layout_scalar_valid_range(adt_def.did) {
2558 // We exploit here that `layout_scalar_valid_range` will never
2559 // return `Bound::Excluded`. (And we have tests checking that we
2560 // handle the attribute correctly.)
2561 (Bound::Included(lo), _) if lo > 0 => {
2562 return Some((format!("`{}` must be non-null", ty), None));
2564 (Bound::Included(_), _) | (_, Bound::Included(_))
2565 if init == InitKind::Uninit =>
2569 "`{}` must be initialized inside its custom valid range",
2578 match adt_def.variants.len() {
2579 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2581 // Struct, or enum with exactly one variant.
2582 // Proceed recursively, check all fields.
2583 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2584 variant.fields.iter().find_map(|field| {
2585 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2588 // Point to this field, should be helpful for figuring
2589 // out where the source of the error is.
2590 let span = tcx.def_span(field.did);
2593 " (in this {} field)",
2606 // Multi-variant enum.
2608 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2609 let span = tcx.def_span(adt_def.did);
2611 "enums have to be initialized to a variant".to_string(),
2615 // In principle, for zero-initialization we could figure out which variant corresponds
2616 // to tag 0, and check that... but for now we just accept all zero-initializations.
2623 // Proceed recursively, check all fields.
2624 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2626 // Conservative fallback.
2631 if let Some(init) = is_dangerous_init(cx, expr) {
2632 // This conjures an instance of a type out of nothing,
2633 // using zeroed or uninitialized memory.
2634 // We are extremely conservative with what we warn about.
2635 let conjured_ty = cx.typeck_results().expr_ty(expr);
2636 if let Some((msg, span)) =
2637 with_no_trimmed_paths(|| ty_find_init_error(cx.tcx, conjured_ty, init))
2639 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2640 let mut err = lint.build(&format!(
2641 "the type `{}` does not permit {}",
2644 InitKind::Zeroed => "zero-initialization",
2645 InitKind::Uninit => "being left uninitialized",
2648 err.span_label(expr.span, "this code causes undefined behavior when executed");
2651 "help: use `MaybeUninit<T>` instead, \
2652 and only call `assume_init` after initialization is done",
2654 if let Some(span) = span {
2655 err.span_note(span, &msg);
2667 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2668 /// has been declared with the same name but different types.
2688 /// Because two symbols of the same name cannot be resolved to two
2689 /// different functions at link time, and one function cannot possibly
2690 /// have two types, a clashing extern declaration is almost certainly a
2691 /// mistake. Check to make sure that the `extern` definitions are correct
2692 /// and equivalent, and possibly consider unifying them in one location.
2694 /// This lint does not run between crates because a project may have
2695 /// dependencies which both rely on the same extern function, but declare
2696 /// it in a different (but valid) way. For example, they may both declare
2697 /// an opaque type for one or more of the arguments (which would end up
2698 /// distinct types), or use types that are valid conversions in the
2699 /// language the `extern fn` is defined in. In these cases, the compiler
2700 /// can't say that the clashing declaration is incorrect.
2701 pub CLASHING_EXTERN_DECLARATIONS,
2703 "detects when an extern fn has been declared with the same name but different types"
2706 pub struct ClashingExternDeclarations {
2707 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2708 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2709 /// the symbol should be reported as a clashing declaration.
2710 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2711 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2712 seen_decls: FxHashMap<Symbol, HirId>,
2715 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2716 /// just from declaration itself. This is important because we don't want to report clashes on
2717 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2720 /// The name of the symbol + the span of the annotation which introduced the link name.
2722 /// No link name, so just the name of the symbol.
2727 fn get_name(&self) -> Symbol {
2729 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2734 impl ClashingExternDeclarations {
2735 crate fn new() -> Self {
2736 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2738 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2739 /// for the item, return its HirId without updating the set.
2740 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2741 let did = fi.def_id.to_def_id();
2742 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2743 let name = Symbol::intern(tcx.symbol_name(instance).name);
2744 if let Some(&hir_id) = self.seen_decls.get(&name) {
2745 // Avoid updating the map with the new entry when we do find a collision. We want to
2746 // make sure we're always pointing to the first definition as the previous declaration.
2747 // This lets us avoid emitting "knock-on" diagnostics.
2750 self.seen_decls.insert(name, fi.hir_id())
2754 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2755 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2757 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2758 if let Some((overridden_link_name, overridden_link_name_span)) =
2759 tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2760 // FIXME: Instead of searching through the attributes again to get span
2761 // information, we could have codegen_fn_attrs also give span information back for
2762 // where the attribute was defined. However, until this is found to be a
2763 // bottleneck, this does just fine.
2765 overridden_link_name,
2766 tcx.get_attrs(fi.def_id.to_def_id())
2768 .find(|at| at.has_name(sym::link_name))
2774 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2776 SymbolName::Normal(fi.ident.name)
2780 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2781 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2782 /// with the same members (as the declarations shouldn't clash).
2783 fn structurally_same_type<'tcx>(
2784 cx: &LateContext<'tcx>,
2789 fn structurally_same_type_impl<'tcx>(
2790 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2791 cx: &LateContext<'tcx>,
2796 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2799 // Given a transparent newtype, reach through and grab the inner
2800 // type unless the newtype makes the type non-null.
2801 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2804 if let ty::Adt(def, substs) = *ty.kind() {
2805 let is_transparent = def.subst(tcx, substs).repr.transparent();
2806 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, &def);
2808 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2809 ty, is_transparent, is_non_null
2811 if is_transparent && !is_non_null {
2812 debug_assert!(def.variants.len() == 1);
2813 let v = &def.variants[VariantIdx::new(0)];
2814 ty = transparent_newtype_field(tcx, v)
2816 "single-variant transparent structure with zero-sized field",
2822 debug!("non_transparent_ty -> {:?}", ty);
2827 let a = non_transparent_ty(a);
2828 let b = non_transparent_ty(b);
2830 if !seen_types.insert((a, b)) {
2831 // We've encountered a cycle. There's no point going any further -- the types are
2832 // structurally the same.
2836 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2837 // All nominally-same types are structurally same, too.
2840 // Do a full, depth-first comparison between the two.
2841 use rustc_middle::ty::TyKind::*;
2842 let a_kind = a.kind();
2843 let b_kind = b.kind();
2845 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2846 debug!("compare_layouts({:?}, {:?})", a, b);
2847 let a_layout = &cx.layout_of(a)?.layout.abi;
2848 let b_layout = &cx.layout_of(b)?.layout.abi;
2850 "comparing layouts: {:?} == {:?} = {}",
2853 a_layout == b_layout
2855 Ok(a_layout == b_layout)
2858 #[allow(rustc::usage_of_ty_tykind)]
2859 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2860 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2863 ensure_sufficient_stack(|| {
2864 match (a_kind, b_kind) {
2865 (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2866 let a = a.subst(cx.tcx, a_substs);
2867 let b = b.subst(cx.tcx, b_substs);
2868 debug!("Comparing {:?} and {:?}", a, b);
2870 // We can immediately rule out these types as structurally same if
2871 // their layouts differ.
2872 match compare_layouts(a, b) {
2873 Ok(false) => return false,
2874 _ => (), // otherwise, continue onto the full, fields comparison
2877 // Grab a flattened representation of all fields.
2878 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2879 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2881 // Perform a structural comparison for each field.
2884 |&ty::FieldDef { did: a_did, .. },
2885 &ty::FieldDef { did: b_did, .. }| {
2886 structurally_same_type_impl(
2896 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2897 // For arrays, we also check the constness of the type.
2898 a_const.val == b_const.val
2899 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2901 (Slice(a_ty), Slice(b_ty)) => {
2902 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2904 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2905 a_tymut.mutbl == b_tymut.mutbl
2906 && structurally_same_type_impl(
2914 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2915 // For structural sameness, we don't need the region to be same.
2917 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2919 (FnDef(..), FnDef(..)) => {
2920 let a_poly_sig = a.fn_sig(tcx);
2921 let b_poly_sig = b.fn_sig(tcx);
2923 // As we don't compare regions, skip_binder is fine.
2924 let a_sig = a_poly_sig.skip_binder();
2925 let b_sig = b_poly_sig.skip_binder();
2927 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2928 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2929 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2930 structurally_same_type_impl(seen_types, cx, a, b, ckind)
2932 && structurally_same_type_impl(
2940 (Tuple(a_substs), Tuple(b_substs)) => {
2941 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2942 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2945 // For these, it's not quite as easy to define structural-sameness quite so easily.
2946 // For the purposes of this lint, take the conservative approach and mark them as
2947 // not structurally same.
2948 (Dynamic(..), Dynamic(..))
2949 | (Error(..), Error(..))
2950 | (Closure(..), Closure(..))
2951 | (Generator(..), Generator(..))
2952 | (GeneratorWitness(..), GeneratorWitness(..))
2953 | (Projection(..), Projection(..))
2954 | (Opaque(..), Opaque(..)) => false,
2956 // These definitely should have been caught above.
2957 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2959 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2960 // enum layout optimisation is being applied.
2961 (Adt(..), other_kind) | (other_kind, Adt(..))
2962 if is_primitive_or_pointer(other_kind) =>
2964 let (primitive, adt) =
2965 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2966 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2969 compare_layouts(a, b).unwrap_or(false)
2972 // Otherwise, just compare the layouts. This may fail to lint for some
2973 // incompatible types, but at the very least, will stop reads into
2974 // uninitialised memory.
2975 _ => compare_layouts(a, b).unwrap_or(false),
2980 let mut seen_types = FxHashSet::default();
2981 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2985 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2987 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2988 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2989 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2990 if let ForeignItemKind::Fn(..) = this_fi.kind {
2992 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2993 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2994 let this_decl_ty = tcx.type_of(this_fi.def_id);
2996 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2997 existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2999 // Check that the declarations match.
3000 if !Self::structurally_same_type(
3004 CItemKind::Declaration,
3006 let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
3007 let orig = Self::name_of_extern_decl(tcx, orig_fi);
3009 // We want to ensure that we use spans for both decls that include where the
3010 // name was defined, whether that was from the link_name attribute or not.
3011 let get_relevant_span =
3012 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
3013 SymbolName::Normal(_) => fi.span,
3014 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
3016 // Finally, emit the diagnostic.
3017 tcx.struct_span_lint_hir(
3018 CLASHING_EXTERN_DECLARATIONS,
3020 get_relevant_span(this_fi),
3022 let mut expected_str = DiagnosticStyledString::new();
3023 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
3024 let mut found_str = DiagnosticStyledString::new();
3025 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3027 lint.build(&format!(
3028 "`{}` redeclare{} with a different signature",
3030 if orig.get_name() == this_fi.ident.name {
3033 format!("s `{}`", orig.get_name())
3037 get_relevant_span(orig_fi),
3038 &format!("`{}` previously declared here", orig.get_name()),
3041 get_relevant_span(this_fi),
3042 "this signature doesn't match the previous declaration",
3044 .note_expected_found(&"", expected_str, &"", found_str)
3055 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3056 /// which causes [undefined behavior].
3061 /// # #![allow(unused)]
3064 /// let x = &*ptr::null::<i32>();
3065 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3066 /// let x = *(0 as *const i32);
3074 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3075 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3077 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3080 "detects when an null pointer is dereferenced"
3083 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3085 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3086 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3087 /// test if expression is a null ptr
3088 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3090 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3091 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3092 return is_zero(expr) || is_null_ptr(cx, expr);
3095 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3096 rustc_hir::ExprKind::Call(ref path, _) => {
3097 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3098 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3100 cx.tcx.get_diagnostic_name(def_id),
3101 Some(sym::ptr_null | sym::ptr_null_mut)
3111 /// test if expression is the literal `0`
3112 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3114 rustc_hir::ExprKind::Lit(ref lit) => {
3115 if let LitKind::Int(a, _) = lit.node {
3124 if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3125 if is_null_ptr(cx, expr_deref) {
3126 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3127 let mut err = lint.build("dereferencing a null pointer");
3128 err.span_label(expr.span, "this code causes undefined behavior when executed");
3137 /// The `named_asm_labels` lint detects the use of named labels in the
3138 /// inline `asm!` macro.
3142 /// ```rust,compile_fail
3143 /// use std::arch::asm;
3147 /// asm!("foo: bar");
3156 /// LLVM is allowed to duplicate inline assembly blocks for any
3157 /// reason, for example when it is in a function that gets inlined. Because
3158 /// of this, GNU assembler [local labels] *must* be used instead of labels
3159 /// with a name. Using named labels might cause assembler or linker errors.
3161 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3162 pub NAMED_ASM_LABELS,
3164 "named labels in inline assembly",
3167 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3169 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3170 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3172 kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3176 for (template_sym, template_snippet, template_span) in template_strs.iter() {
3177 let template_str = template_sym.as_str();
3178 let find_label_span = |needle: &str| -> Option<Span> {
3179 if let Some(template_snippet) = template_snippet {
3180 let snippet = template_snippet.as_str();
3181 if let Some(pos) = snippet.find(needle) {
3185 .unwrap_or(snippet[pos..].len() - 1);
3186 let inner = InnerSpan::new(pos, end);
3187 return Some(template_span.from_inner(inner));
3194 let mut found_labels = Vec::new();
3196 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3197 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3198 for statement in statements {
3199 // If there's a comment, trim it from the statement
3200 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3201 let mut start_idx = 0;
3202 for (idx, _) in statement.match_indices(':') {
3203 let possible_label = statement[start_idx..idx].trim();
3204 let mut chars = possible_label.chars();
3205 let Some(c) = chars.next() else {
3206 // Empty string means a leading ':' in this section, which is not a label
3209 // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3210 if (c.is_alphabetic() || matches!(c, '.' | '_'))
3211 && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3213 found_labels.push(possible_label);
3215 // If we encounter a non-label, there cannot be any further labels, so stop checking
3219 start_idx = idx + 1;
3223 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3225 if found_labels.len() > 0 {
3226 let spans = found_labels
3228 .filter_map(|label| find_label_span(label))
3229 .collect::<Vec<Span>>();
3230 // If there were labels but we couldn't find a span, combine the warnings and use the template span
3231 let target_spans: MultiSpan =
3232 if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3234 cx.lookup_with_diagnostics(
3239 diag.build("avoid using named labels in inline assembly");
3242 BuiltinLintDiagnostics::NamedAsmLabel(
3243 "only local labels of the form `<number>:` should be used in inline asm"