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;
35 fluent, Applicability, Diagnostic, DiagnosticMessage, DiagnosticStyledString,
36 LintDiagnosticBuilder, MultiSpan,
38 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
40 use rustc_hir::def::{DefKind, Res};
41 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
42 use rustc_hir::{ForeignItemKind, GenericParamKind, HirId, PatKind, PredicateOrigin};
43 use rustc_index::vec::Idx;
44 use rustc_middle::lint::in_external_macro;
45 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
46 use rustc_middle::ty::print::with_no_trimmed_paths;
47 use rustc_middle::ty::subst::GenericArgKind;
48 use rustc_middle::ty::Instance;
49 use rustc_middle::ty::{self, Ty, TyCtxt};
50 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
51 use rustc_span::edition::Edition;
52 use rustc_span::source_map::Spanned;
53 use rustc_span::symbol::{kw, sym, Ident, Symbol};
54 use rustc_span::{BytePos, InnerSpan, Span};
55 use rustc_target::abi::VariantIdx;
56 use rustc_trait_selection::traits::{self, misc::can_type_implement_copy};
58 use crate::nonstandard_style::{method_context, MethodLateContext};
61 use tracing::{debug, trace};
63 // hardwired lints from librustc_middle
64 pub use rustc_session::lint::builtin::*;
67 /// The `while_true` lint detects `while true { }`.
81 /// `while true` should be replaced with `loop`. A `loop` expression is
82 /// the preferred way to write an infinite loop because it more directly
83 /// expresses the intent of the loop.
86 "suggest using `loop { }` instead of `while true { }`"
89 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
91 /// Traverse through any amount of parenthesis and return the first non-parens expression.
92 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
93 while let ast::ExprKind::Paren(sub) = &expr.kind {
99 impl EarlyLintPass for WhileTrue {
100 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
101 if let ast::ExprKind::While(cond, _, label) = &e.kind {
102 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
103 if let ast::LitKind::Bool(true) = lit.kind {
104 if !lit.span.from_expansion() {
105 let condition_span = e.span.with_hi(cond.span.hi());
106 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
107 lint.build(fluent::lint::builtin_while_true)
108 .span_suggestion_short(
110 fluent::lint::suggestion,
113 label.map_or_else(String::new, |label| format!(
118 Applicability::MachineApplicable,
130 /// The `box_pointers` lints use of the Box type.
134 /// ```rust,compile_fail
135 /// #![deny(box_pointers)]
145 /// This lint is mostly historical, and not particularly useful. `Box<T>`
146 /// used to be built into the language, and the only way to do heap
147 /// allocation. Today's Rust can call into other allocators, etc.
150 "use of owned (Box type) heap memory"
153 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
156 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
157 for leaf in ty.walk() {
158 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
159 if leaf_ty.is_box() {
160 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
161 lint.build(fluent::lint::builtin_box_pointers).set_arg("ty", ty).emit();
169 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
170 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
172 hir::ItemKind::Fn(..)
173 | hir::ItemKind::TyAlias(..)
174 | hir::ItemKind::Enum(..)
175 | hir::ItemKind::Struct(..)
176 | hir::ItemKind::Union(..) => {
177 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
182 // If it's a struct, we also have to check the fields' types
184 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
185 for struct_field in struct_def.fields() {
186 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
187 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
194 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
195 let ty = cx.typeck_results().node_type(e.hir_id);
196 self.check_heap_type(cx, e.span, ty);
201 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
202 /// instead of `Struct { x }` in a pattern.
220 /// Point { x: x, y: y } => (),
229 /// The preferred style is to avoid the repetition of specifying both the
230 /// field name and the binding name if both identifiers are the same.
231 NON_SHORTHAND_FIELD_PATTERNS,
233 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
236 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
238 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
239 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
240 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
245 .expect("struct pattern type is not an ADT")
246 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
247 for fieldpat in field_pats {
248 if fieldpat.is_shorthand {
251 if fieldpat.span.from_expansion() {
252 // Don't lint if this is a macro expansion: macro authors
253 // shouldn't have to worry about this kind of style issue
257 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
258 if cx.tcx.find_field_index(ident, &variant)
259 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
261 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
262 let binding = match binding_annot {
263 hir::BindingAnnotation::Unannotated => None,
264 hir::BindingAnnotation::Mutable => Some("mut"),
265 hir::BindingAnnotation::Ref => Some("ref"),
266 hir::BindingAnnotation::RefMut => Some("ref mut"),
268 let suggested_ident = if let Some(binding) = binding {
269 format!("{} {}", binding, ident)
273 lint.build(fluent::lint::builtin_non_shorthand_field_patterns)
274 .set_arg("ident", ident.clone())
277 fluent::lint::suggestion,
279 Applicability::MachineApplicable,
291 /// The `unsafe_code` lint catches usage of `unsafe` code.
295 /// ```rust,compile_fail
296 /// #![deny(unsafe_code)]
308 /// This lint is intended to restrict the usage of `unsafe`, which can be
309 /// difficult to use correctly.
312 "usage of `unsafe` code"
315 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
320 cx: &EarlyContext<'_>,
322 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
324 // This comes from a macro that has `#[allow_internal_unsafe]`.
325 if span.allows_unsafe() {
329 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
332 fn report_overridden_symbol_name(
334 cx: &EarlyContext<'_>,
336 msg: DiagnosticMessage,
338 self.report_unsafe(cx, span, |lint| {
339 lint.build(msg).note(fluent::lint::builtin_overridden_symbol_name).emit();
343 fn report_overridden_symbol_section(
345 cx: &EarlyContext<'_>,
347 msg: DiagnosticMessage,
349 self.report_unsafe(cx, span, |lint| {
350 lint.build(msg).note(fluent::lint::builtin_overridden_symbol_section).emit();
355 impl EarlyLintPass for UnsafeCode {
356 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
357 if attr.has_name(sym::allow_internal_unsafe) {
358 self.report_unsafe(cx, attr.span, |lint| {
359 lint.build(fluent::lint::builtin_allow_internal_unsafe).emit();
364 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
365 if let ast::ExprKind::Block(ref blk, _) = e.kind {
366 // Don't warn about generated blocks; that'll just pollute the output.
367 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
368 self.report_unsafe(cx, blk.span, |lint| {
369 lint.build(fluent::lint::builtin_unsafe_block).emit();
375 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
377 ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => self
378 .report_unsafe(cx, it.span, |lint| {
379 lint.build(fluent::lint::builtin_unsafe_trait).emit();
382 ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => self
383 .report_unsafe(cx, it.span, |lint| {
384 lint.build(fluent::lint::builtin_unsafe_impl).emit();
387 ast::ItemKind::Fn(..) => {
388 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
389 self.report_overridden_symbol_name(
392 fluent::lint::builtin_no_mangle_fn,
396 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
397 self.report_overridden_symbol_name(
400 fluent::lint::builtin_export_name_fn,
404 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
405 self.report_overridden_symbol_section(
408 fluent::lint::builtin_link_section_fn,
413 ast::ItemKind::Static(..) => {
414 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
415 self.report_overridden_symbol_name(
418 fluent::lint::builtin_no_mangle_static,
422 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
423 self.report_overridden_symbol_name(
426 fluent::lint::builtin_export_name_static,
430 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
431 self.report_overridden_symbol_section(
434 fluent::lint::builtin_link_section_static,
443 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
444 if let ast::AssocItemKind::Fn(..) = it.kind {
445 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
446 self.report_overridden_symbol_name(
449 fluent::lint::builtin_no_mangle_method,
452 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
453 self.report_overridden_symbol_name(
456 fluent::lint::builtin_export_name_method,
462 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
466 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
472 let msg = match ctxt {
473 FnCtxt::Foreign => return,
474 FnCtxt::Free => fluent::lint::builtin_decl_unsafe_fn,
475 FnCtxt::Assoc(_) if body.is_none() => fluent::lint::builtin_decl_unsafe_method,
476 FnCtxt::Assoc(_) => fluent::lint::builtin_impl_unsafe_method,
478 self.report_unsafe(cx, span, |lint| {
479 lint.build(msg).emit();
486 /// The `missing_docs` lint detects missing documentation for public items.
490 /// ```rust,compile_fail
491 /// #![deny(missing_docs)]
499 /// This lint is intended to ensure that a library is well-documented.
500 /// Items without documentation can be difficult for users to understand
501 /// how to use properly.
503 /// This lint is "allow" by default because it can be noisy, and not all
504 /// projects may want to enforce everything to be documented.
507 "detects missing documentation for public members",
508 report_in_external_macro
511 pub struct MissingDoc {
512 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
513 doc_hidden_stack: Vec<bool>,
516 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
518 fn has_doc(attr: &ast::Attribute) -> bool {
519 if attr.is_doc_comment() {
523 if !attr.has_name(sym::doc) {
527 if attr.value_str().is_some() {
531 if let Some(list) = attr.meta_item_list() {
533 if meta.has_name(sym::hidden) {
543 pub fn new() -> MissingDoc {
544 MissingDoc { doc_hidden_stack: vec![false] }
547 fn doc_hidden(&self) -> bool {
548 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
551 fn check_missing_docs_attrs(
553 cx: &LateContext<'_>,
555 article: &'static str,
558 // If we're building a test harness, then warning about
559 // documentation is probably not really relevant right now.
560 if cx.sess().opts.test {
564 // `#[doc(hidden)]` disables missing_docs check.
565 if self.doc_hidden() {
569 // Only check publicly-visible items, using the result from the privacy pass.
570 // It's an option so the crate root can also use this function (it doesn't
572 if def_id != CRATE_DEF_ID {
573 if !cx.access_levels.is_exported(def_id) {
578 let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
579 let has_doc = attrs.iter().any(has_doc);
581 cx.struct_span_lint(MISSING_DOCS, cx.tcx.def_span(def_id), |lint| {
582 lint.build(fluent::lint::builtin_missing_doc)
583 .set_arg("article", article)
584 .set_arg("desc", desc)
591 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
592 fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
593 let doc_hidden = self.doc_hidden()
594 || attrs.iter().any(|attr| {
595 attr.has_name(sym::doc)
596 && match attr.meta_item_list() {
598 Some(l) => attr::list_contains_name(&l, sym::hidden),
601 self.doc_hidden_stack.push(doc_hidden);
604 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
605 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
608 fn check_crate(&mut self, cx: &LateContext<'_>) {
609 self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
612 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
614 hir::ItemKind::Trait(..) => {
615 // Issue #11592: traits are always considered exported, even when private.
616 if cx.tcx.visibility(it.def_id)
617 == ty::Visibility::Restricted(
618 cx.tcx.parent_module_from_def_id(it.def_id).to_def_id(),
624 hir::ItemKind::TyAlias(..)
625 | hir::ItemKind::Fn(..)
626 | hir::ItemKind::Macro(..)
627 | hir::ItemKind::Mod(..)
628 | hir::ItemKind::Enum(..)
629 | hir::ItemKind::Struct(..)
630 | hir::ItemKind::Union(..)
631 | hir::ItemKind::Const(..)
632 | hir::ItemKind::Static(..) => {}
637 let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
639 self.check_missing_docs_attrs(cx, it.def_id, article, desc);
642 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
643 let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
645 self.check_missing_docs_attrs(cx, trait_item.def_id, article, desc);
648 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
649 // If the method is an impl for a trait, don't doc.
650 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
654 // If the method is an impl for an item with docs_hidden, don't doc.
655 if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
656 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
657 let impl_ty = cx.tcx.type_of(parent);
658 let outerdef = match impl_ty.kind() {
659 ty::Adt(def, _) => Some(def.did()),
660 ty::Foreign(def_id) => Some(*def_id),
663 let is_hidden = match outerdef {
664 Some(id) => cx.tcx.is_doc_hidden(id),
672 let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
673 self.check_missing_docs_attrs(cx, impl_item.def_id, article, desc);
676 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
677 let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
678 self.check_missing_docs_attrs(cx, foreign_item.def_id, article, desc);
681 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
682 if !sf.is_positional() {
683 let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
684 self.check_missing_docs_attrs(cx, def_id, "a", "struct field")
688 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
689 self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), "a", "variant");
694 /// The `missing_copy_implementations` lint detects potentially-forgotten
695 /// implementations of [`Copy`].
697 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
701 /// ```rust,compile_fail
702 /// #![deny(missing_copy_implementations)]
713 /// Historically (before 1.0), types were automatically marked as `Copy`
714 /// if possible. This was changed so that it required an explicit opt-in
715 /// by implementing the `Copy` trait. As part of this change, a lint was
716 /// added to alert if a copyable type was not marked `Copy`.
718 /// This lint is "allow" by default because this code isn't bad; it is
719 /// common to write newtypes like this specifically so that a `Copy` type
720 /// is no longer `Copy`. `Copy` types can result in unintended copies of
721 /// large data which can impact performance.
722 pub MISSING_COPY_IMPLEMENTATIONS,
724 "detects potentially-forgotten implementations of `Copy`"
727 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
729 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
730 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
731 if !cx.access_levels.is_reachable(item.def_id) {
734 let (def, ty) = match item.kind {
735 hir::ItemKind::Struct(_, ref ast_generics) => {
736 if !ast_generics.params.is_empty() {
739 let def = cx.tcx.adt_def(item.def_id);
740 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
742 hir::ItemKind::Union(_, ref ast_generics) => {
743 if !ast_generics.params.is_empty() {
746 let def = cx.tcx.adt_def(item.def_id);
747 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
749 hir::ItemKind::Enum(_, ref ast_generics) => {
750 if !ast_generics.params.is_empty() {
753 let def = cx.tcx.adt_def(item.def_id);
754 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
758 if def.has_dtor(cx.tcx) {
761 let param_env = ty::ParamEnv::empty();
762 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
765 if can_type_implement_copy(
769 traits::ObligationCause::misc(item.span, item.hir_id()),
773 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
774 lint.build(fluent::lint::builtin_missing_copy_impl).emit();
781 /// The `missing_debug_implementations` lint detects missing
782 /// implementations of [`fmt::Debug`].
784 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
788 /// ```rust,compile_fail
789 /// #![deny(missing_debug_implementations)]
798 /// Having a `Debug` implementation on all types can assist with
799 /// debugging, as it provides a convenient way to format and display a
800 /// value. Using the `#[derive(Debug)]` attribute will automatically
801 /// generate a typical implementation, or a custom implementation can be
802 /// added by manually implementing the `Debug` trait.
804 /// This lint is "allow" by default because adding `Debug` to all types can
805 /// have a negative impact on compile time and code size. It also requires
806 /// boilerplate to be added to every type, which can be an impediment.
807 MISSING_DEBUG_IMPLEMENTATIONS,
809 "detects missing implementations of Debug"
813 pub struct MissingDebugImplementations {
814 impling_types: Option<LocalDefIdSet>,
817 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
819 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
820 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
821 if !cx.access_levels.is_reachable(item.def_id) {
826 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
830 let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
834 if self.impling_types.is_none() {
835 let mut impls = LocalDefIdSet::default();
836 cx.tcx.for_each_impl(debug, |d| {
837 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
838 if let Some(def_id) = ty_def.did().as_local() {
839 impls.insert(def_id);
844 self.impling_types = Some(impls);
845 debug!("{:?}", self.impling_types);
848 if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
849 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
850 lint.build(fluent::lint::builtin_missing_debug_impl)
851 .set_arg("debug", cx.tcx.def_path_str(debug))
859 /// The `anonymous_parameters` lint detects anonymous parameters in trait
864 /// ```rust,edition2015,compile_fail
865 /// #![deny(anonymous_parameters)]
877 /// This syntax is mostly a historical accident, and can be worked around
878 /// quite easily by adding an `_` pattern or a descriptive identifier:
882 /// fn foo(_: usize);
886 /// This syntax is now a hard error in the 2018 edition. In the 2015
887 /// edition, this lint is "warn" by default. This lint
888 /// enables the [`cargo fix`] tool with the `--edition` flag to
889 /// automatically transition old code from the 2015 edition to 2018. The
890 /// tool will run this lint and automatically apply the
891 /// suggested fix from the compiler (which is to add `_` to each
892 /// parameter). This provides a completely automated way to update old
893 /// code for a new edition. See [issue #41686] for more details.
895 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
896 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
897 pub ANONYMOUS_PARAMETERS,
899 "detects anonymous parameters",
900 @future_incompatible = FutureIncompatibleInfo {
901 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
902 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
907 /// Checks for use of anonymous parameters (RFC 1685).
908 AnonymousParameters => [ANONYMOUS_PARAMETERS]
911 impl EarlyLintPass for AnonymousParameters {
912 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
913 if cx.sess().edition() != Edition::Edition2015 {
914 // This is a hard error in future editions; avoid linting and erroring
917 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
918 for arg in sig.decl.inputs.iter() {
919 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
920 if ident.name == kw::Empty {
921 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
922 let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
924 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
925 (snip.as_str(), Applicability::MachineApplicable)
927 ("<type>", Applicability::HasPlaceholders)
930 lint.build(fluent::lint::builtin_anonymous_params)
933 fluent::lint::suggestion,
934 format!("_: {}", ty_snip),
946 /// Check for use of attributes which have been deprecated.
948 pub struct DeprecatedAttr {
949 // This is not free to compute, so we want to keep it around, rather than
950 // compute it for every attribute.
951 depr_attrs: Vec<&'static BuiltinAttribute>,
954 impl_lint_pass!(DeprecatedAttr => []);
956 impl DeprecatedAttr {
957 pub fn new() -> DeprecatedAttr {
958 DeprecatedAttr { depr_attrs: deprecated_attributes() }
962 impl EarlyLintPass for DeprecatedAttr {
963 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
964 for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
965 if attr.ident().map(|ident| ident.name) == Some(*name) {
966 if let &AttributeGate::Gated(
967 Stability::Deprecated(link, suggestion),
973 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
974 // FIXME(davidtwco) translatable deprecated attr
975 lint.build(fluent::lint::builtin_deprecated_attr_link)
976 .set_arg("name", name)
977 .set_arg("reason", reason)
978 .set_arg("link", link)
979 .span_suggestion_short(
981 suggestion.map(|s| s.into()).unwrap_or(
982 fluent::lint::builtin_deprecated_attr_default_suggestion,
985 Applicability::MachineApplicable,
993 if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
994 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
995 lint.build(fluent::lint::builtin_deprecated_attr_used)
996 .set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
997 .span_suggestion_short(
999 fluent::lint::builtin_deprecated_attr_default_suggestion,
1001 Applicability::MachineApplicable,
1009 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1010 use rustc_ast::token::CommentKind;
1012 let mut attrs = attrs.iter().peekable();
1014 // Accumulate a single span for sugared doc comments.
1015 let mut sugared_span: Option<Span> = None;
1017 while let Some(attr) = attrs.next() {
1018 let is_doc_comment = attr.is_doc_comment();
1021 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1024 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1028 let span = sugared_span.take().unwrap_or(attr.span);
1030 if is_doc_comment || attr.has_name(sym::doc) {
1031 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1032 let mut err = lint.build(fluent::lint::builtin_unused_doc_comment);
1033 err.set_arg("kind", node_kind);
1034 err.span_label(node_span, fluent::lint::label);
1036 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1037 err.help(fluent::lint::plain_help);
1039 AttrKind::DocComment(CommentKind::Block, _) => {
1040 err.help(fluent::lint::block_help);
1049 impl EarlyLintPass for UnusedDocComment {
1050 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1051 let kind = match stmt.kind {
1052 ast::StmtKind::Local(..) => "statements",
1053 // Disabled pending discussion in #78306
1054 ast::StmtKind::Item(..) => return,
1055 // expressions will be reported by `check_expr`.
1056 ast::StmtKind::Empty
1057 | ast::StmtKind::Semi(_)
1058 | ast::StmtKind::Expr(_)
1059 | ast::StmtKind::MacCall(_) => return,
1062 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1065 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1066 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1067 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1070 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1071 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1074 fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1075 warn_if_doc(cx, param.ident.span, "generic parameters", ¶m.attrs);
1078 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1079 warn_if_doc(cx, block.span, "blocks", &block.attrs());
1082 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1083 if let ast::ItemKind::ForeignMod(_) = item.kind {
1084 warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1090 /// The `no_mangle_const_items` lint detects any `const` items with the
1091 /// [`no_mangle` attribute].
1093 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1097 /// ```rust,compile_fail
1099 /// const FOO: i32 = 5;
1106 /// Constants do not have their symbols exported, and therefore, this
1107 /// probably means you meant to use a [`static`], not a [`const`].
1109 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1110 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1111 NO_MANGLE_CONST_ITEMS,
1113 "const items will not have their symbols exported"
1117 /// The `no_mangle_generic_items` lint detects generic items that must be
1124 /// fn foo<T>(t: T) {
1133 /// A function with generics must have its symbol mangled to accommodate
1134 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1135 /// this situation, and should be removed.
1137 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1138 NO_MANGLE_GENERIC_ITEMS,
1140 "generic items must be mangled"
1143 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1145 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1146 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1147 let attrs = cx.tcx.hir().attrs(it.hir_id());
1148 let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1149 impl_generics: Option<&hir::Generics<'_>>,
1150 generics: &hir::Generics<'_>,
1153 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1156 GenericParamKind::Lifetime { .. } => {}
1157 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1158 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
1159 lint.build(fluent::lint::builtin_no_mangle_generic)
1160 .span_suggestion_short(
1161 no_mangle_attr.span,
1162 fluent::lint::suggestion,
1164 // Use of `#[no_mangle]` suggests FFI intent; correct
1165 // fix may be to monomorphize source by hand
1166 Applicability::MaybeIncorrect,
1176 hir::ItemKind::Fn(.., ref generics, _) => {
1177 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1178 check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1181 hir::ItemKind::Const(..) => {
1182 if cx.sess().contains_name(attrs, sym::no_mangle) {
1183 // Const items do not refer to a particular location in memory, and therefore
1184 // don't have anything to attach a symbol to
1185 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1186 let mut err = lint.build(fluent::lint::builtin_const_no_mangle);
1188 // account for "pub const" (#45562)
1193 .span_to_snippet(it.span)
1194 .map(|snippet| snippet.find("const").unwrap_or(0))
1195 .unwrap_or(0) as u32;
1196 // `const` is 5 chars
1197 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1198 err.span_suggestion(
1200 fluent::lint::suggestion,
1202 Applicability::MachineApplicable,
1208 hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1210 if let hir::AssocItemKind::Fn { .. } = it.kind {
1211 if let Some(no_mangle_attr) = cx
1213 .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1215 check_no_mangle_on_generic_fn(
1218 cx.tcx.hir().get_generics(it.id.def_id).unwrap(),
1231 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1232 /// T` because it is [undefined behavior].
1234 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1238 /// ```rust,compile_fail
1240 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1248 /// Certain assumptions are made about aliasing of data, and this transmute
1249 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1251 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1254 "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1257 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1259 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1260 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1261 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1262 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1264 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1265 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
1266 lint.build(fluent::lint::builtin_mutable_transmutes).emit();
1271 fn get_transmute_from_to<'tcx>(
1272 cx: &LateContext<'tcx>,
1273 expr: &hir::Expr<'_>,
1274 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1275 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1276 cx.qpath_res(qpath, expr.hir_id)
1280 if let Res::Def(DefKind::Fn, did) = def {
1281 if !def_id_is_transmute(cx, did) {
1284 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1285 let from = sig.inputs().skip_binder()[0];
1286 let to = sig.output().skip_binder();
1287 return Some((from, to));
1292 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1293 cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1299 /// The `unstable_features` is deprecated and should no longer be used.
1302 "enabling unstable features (deprecated. do not use)"
1306 /// Forbids using the `#[feature(...)]` attribute
1307 UnstableFeatures => [UNSTABLE_FEATURES]
1310 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1311 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1312 if attr.has_name(sym::feature) {
1313 if let Some(items) = attr.meta_item_list() {
1315 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1316 lint.build(fluent::lint::builtin_unstable_features).emit();
1325 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1330 /// ```rust,compile_fail
1331 /// #![deny(unreachable_pub)]
1343 /// A bare `pub` visibility may be misleading if the item is not actually
1344 /// publicly exported from the crate. The `pub(crate)` visibility is
1345 /// recommended to be used instead, which more clearly expresses the intent
1346 /// that the item is only visible within its own crate.
1348 /// This lint is "allow" by default because it will trigger for a large
1349 /// amount existing Rust code, and has some false-positives. Eventually it
1350 /// is desired for this to become warn-by-default.
1351 pub UNREACHABLE_PUB,
1353 "`pub` items not reachable from crate root"
1357 /// Lint for items marked `pub` that aren't reachable from other crates.
1358 UnreachablePub => [UNREACHABLE_PUB]
1361 impl UnreachablePub {
1364 cx: &LateContext<'_>,
1370 let mut applicability = Applicability::MachineApplicable;
1371 if cx.tcx.visibility(def_id).is_public() && !cx.access_levels.is_reachable(def_id) {
1372 if vis_span.from_expansion() {
1373 applicability = Applicability::MaybeIncorrect;
1375 let def_span = cx.tcx.def_span(def_id);
1376 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1377 let mut err = lint.build(fluent::lint::builtin_unreachable_pub);
1378 err.set_arg("what", what);
1380 err.span_suggestion(
1382 fluent::lint::suggestion,
1387 err.help(fluent::lint::help);
1395 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1396 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1397 // Do not warn for fake `use` statements.
1398 if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1401 self.perform_lint(cx, "item", item.def_id, item.vis_span, true);
1404 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1405 self.perform_lint(cx, "item", foreign_item.def_id, foreign_item.vis_span, true);
1408 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1409 let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1410 self.perform_lint(cx, "field", def_id, field.vis_span, false);
1413 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1414 // Only lint inherent impl items.
1415 if cx.tcx.associated_item(impl_item.def_id).trait_item_def_id.is_none() {
1416 self.perform_lint(cx, "item", impl_item.def_id, impl_item.vis_span, false);
1422 /// The `type_alias_bounds` lint detects bounds in type aliases.
1427 /// type SendVec<T: Send> = Vec<T>;
1434 /// The trait bounds in a type alias are currently ignored, and should not
1435 /// be included to avoid confusion. This was previously allowed
1436 /// unintentionally; this may become a hard error in the future.
1439 "bounds in type aliases are not enforced"
1443 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1444 /// They are relevant when using associated types, but otherwise neither checked
1445 /// at definition site nor enforced at use site.
1446 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1449 impl TypeAliasBounds {
1450 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1452 hir::QPath::TypeRelative(ref ty, _) => {
1453 // If this is a type variable, we found a `T::Assoc`.
1455 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1456 matches!(path.res, Res::Def(DefKind::TyParam, _))
1461 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1465 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1466 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1467 // bound. Let's see if this type does that.
1469 // We use a HIR visitor to walk the type.
1470 use rustc_hir::intravisit::{self, Visitor};
1471 struct WalkAssocTypes<'a> {
1472 err: &'a mut Diagnostic,
1474 impl Visitor<'_> for WalkAssocTypes<'_> {
1475 fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1476 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1477 self.err.span_help(span, fluent::lint::builtin_type_alias_bounds_help);
1479 intravisit::walk_qpath(self, qpath, id, span)
1483 // Let's go for a walk!
1484 let mut visitor = WalkAssocTypes { err };
1485 visitor.visit_ty(ty);
1489 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1490 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1491 let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1494 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1495 // Bounds are respected for `type X = impl Trait`
1498 // There must not be a where clause
1499 if type_alias_generics.predicates.is_empty() {
1503 let mut where_spans = Vec::new();
1504 let mut inline_spans = Vec::new();
1505 let mut inline_sugg = Vec::new();
1506 for p in type_alias_generics.predicates {
1507 let span = p.span();
1508 if p.in_where_clause() {
1509 where_spans.push(span);
1511 for b in p.bounds() {
1512 inline_spans.push(b.span());
1514 inline_sugg.push((span, String::new()));
1518 let mut suggested_changing_assoc_types = false;
1519 if !where_spans.is_empty() {
1520 cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1521 let mut err = lint.build(fluent::lint::builtin_type_alias_where_clause);
1522 err.set_span(where_spans);
1523 err.span_suggestion(
1524 type_alias_generics.where_clause_span,
1525 fluent::lint::suggestion,
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 if !inline_spans.is_empty() {
1538 cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1539 let mut err = lint.build(fluent::lint::builtin_type_alias_generic_bounds);
1540 err.set_span(inline_spans);
1541 err.multipart_suggestion(
1542 fluent::lint::suggestion,
1544 Applicability::MachineApplicable,
1546 if !suggested_changing_assoc_types {
1547 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1556 /// Lint constants that are erroneous.
1557 /// Without this lint, we might not get any diagnostic if the constant is
1558 /// unused within this crate, even though downstream crates can't use it
1559 /// without producing an error.
1560 UnusedBrokenConst => []
1563 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1564 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1566 hir::ItemKind::Const(_, body_id) => {
1567 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1568 // trigger the query once for all constants since that will already report the errors
1569 cx.tcx.ensure().const_eval_poly(def_id);
1571 hir::ItemKind::Static(_, _, body_id) => {
1572 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1573 cx.tcx.ensure().eval_static_initializer(def_id);
1581 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1582 /// any type parameters.
1587 /// #![feature(trivial_bounds)]
1588 /// pub struct A where i32: Copy;
1595 /// Usually you would not write a trait bound that you know is always
1596 /// true, or never true. However, when using macros, the macro may not
1597 /// know whether or not the constraint would hold or not at the time when
1598 /// generating the code. Currently, the compiler does not alert you if the
1599 /// constraint is always true, and generates an error if it is never true.
1600 /// The `trivial_bounds` feature changes this to be a warning in both
1601 /// cases, giving macros more freedom and flexibility to generate code,
1602 /// while still providing a signal when writing non-macro code that
1603 /// something is amiss.
1605 /// See [RFC 2056] for more details. This feature is currently only
1606 /// available on the nightly channel, see [tracking issue #48214].
1608 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1609 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1612 "these bounds don't depend on an type parameters"
1616 /// Lint for trait and lifetime bounds that don't depend on type parameters
1617 /// which either do nothing, or stop the item from being used.
1618 TrivialConstraints => [TRIVIAL_BOUNDS]
1621 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1622 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1623 use rustc_middle::ty::visit::TypeVisitable;
1624 use rustc_middle::ty::PredicateKind::*;
1626 if cx.tcx.features().trivial_bounds {
1627 let predicates = cx.tcx.predicates_of(item.def_id);
1628 for &(predicate, span) in predicates.predicates {
1629 let predicate_kind_name = match predicate.kind().skip_binder() {
1630 Trait(..) => "trait",
1632 RegionOutlives(..) => "lifetime",
1634 // Ignore projections, as they can only be global
1635 // if the trait bound is global
1637 // Ignore bounds that a user can't type
1643 ConstEvaluatable(..) |
1645 TypeWellFormedFromEnv(..) => continue,
1647 if predicate.is_global() {
1648 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1649 lint.build(fluent::lint::builtin_trivial_bounds)
1650 .set_arg("predicate_kind_name", predicate_kind_name)
1651 .set_arg("predicate", predicate)
1661 /// Does nothing as a lint pass, but registers some `Lint`s
1662 /// which are used by other parts of the compiler.
1666 NON_SHORTHAND_FIELD_PATTERNS,
1669 MISSING_COPY_IMPLEMENTATIONS,
1670 MISSING_DEBUG_IMPLEMENTATIONS,
1671 ANONYMOUS_PARAMETERS,
1672 UNUSED_DOC_COMMENTS,
1673 NO_MANGLE_CONST_ITEMS,
1674 NO_MANGLE_GENERIC_ITEMS,
1684 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1685 /// pattern], which is deprecated.
1687 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1691 /// ```rust,edition2018
1703 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1704 /// confusion with the [`..` range expression]. Use the new form instead.
1706 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1707 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1709 "`...` range patterns are deprecated",
1710 @future_incompatible = FutureIncompatibleInfo {
1711 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1712 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1717 pub struct EllipsisInclusiveRangePatterns {
1718 /// If `Some(_)`, suppress all subsequent pattern
1719 /// warnings for better diagnostics.
1720 node_id: Option<ast::NodeId>,
1723 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1725 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1726 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1727 if self.node_id.is_some() {
1728 // Don't recursively warn about patterns inside range endpoints.
1732 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1734 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1735 /// corresponding to the ellipsis.
1736 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1741 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1742 ) => Some((a.as_deref(), b, *span)),
1747 let (parenthesise, endpoints) = match &pat.kind {
1748 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1749 _ => (false, matches_ellipsis_pat(pat)),
1752 if let Some((start, end, join)) = endpoints {
1753 let msg = fluent::lint::builtin_ellipsis_inclusive_range_patterns;
1754 let suggestion = fluent::lint::suggestion;
1756 self.node_id = Some(pat.id);
1757 let end = expr_to_string(&end);
1758 let replace = match start {
1759 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1760 None => format!("&(..={})", end),
1762 if join.edition() >= Edition::Edition2021 {
1763 let mut err = cx.sess().struct_span_err_with_code(
1766 rustc_errors::error_code!(E0783),
1768 err.span_suggestion(
1772 Applicability::MachineApplicable,
1776 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1782 Applicability::MachineApplicable,
1788 let replace = "..=";
1789 if join.edition() >= Edition::Edition2021 {
1790 let mut err = cx.sess().struct_span_err_with_code(
1793 rustc_errors::error_code!(E0783),
1795 err.span_suggestion_short(
1799 Applicability::MachineApplicable,
1803 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1805 .span_suggestion_short(
1809 Applicability::MachineApplicable,
1818 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1819 if let Some(node_id) = self.node_id {
1820 if pat.id == node_id {
1828 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1829 /// that are not able to be run by the test harness because they are in a
1830 /// position where they are not nameable.
1832 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1840 /// // This test will not fail because it does not run.
1841 /// assert_eq!(1, 2);
1850 /// In order for the test harness to run a test, the test function must be
1851 /// located in a position where it can be accessed from the crate root.
1852 /// This generally means it must be defined in a module, and not anywhere
1853 /// else such as inside another function. The compiler previously allowed
1854 /// this without an error, so a lint was added as an alert that a test is
1855 /// not being used. Whether or not this should be allowed has not yet been
1856 /// decided, see [RFC 2471] and [issue #36629].
1858 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1859 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1860 UNNAMEABLE_TEST_ITEMS,
1862 "detects an item that cannot be named being marked as `#[test_case]`",
1863 report_in_external_macro
1866 pub struct UnnameableTestItems {
1867 boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1868 items_nameable: bool,
1871 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1873 impl UnnameableTestItems {
1874 pub fn new() -> Self {
1875 Self { boundary: None, items_nameable: true }
1879 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1880 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1881 if self.items_nameable {
1882 if let hir::ItemKind::Mod(..) = it.kind {
1884 self.items_nameable = false;
1885 self.boundary = Some(it.def_id);
1890 let attrs = cx.tcx.hir().attrs(it.hir_id());
1891 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1892 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1893 lint.build(fluent::lint::builtin_unnameable_test_items).emit();
1898 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1899 if !self.items_nameable && self.boundary == Some(it.def_id) {
1900 self.items_nameable = true;
1906 /// The `keyword_idents` lint detects edition keywords being used as an
1911 /// ```rust,edition2015,compile_fail
1912 /// #![deny(keyword_idents)]
1921 /// Rust [editions] allow the language to evolve without breaking
1922 /// backwards compatibility. This lint catches code that uses new keywords
1923 /// that are added to the language that are used as identifiers (such as a
1924 /// variable name, function name, etc.). If you switch the compiler to a
1925 /// new edition without updating the code, then it will fail to compile if
1926 /// you are using a new keyword as an identifier.
1928 /// You can manually change the identifiers to a non-keyword, or use a
1929 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1931 /// This lint solves the problem automatically. It is "allow" by default
1932 /// because the code is perfectly valid in older editions. The [`cargo
1933 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1934 /// and automatically apply the suggested fix from the compiler (which is
1935 /// to use a raw identifier). This provides a completely automated way to
1936 /// update old code for a new edition.
1938 /// [editions]: https://doc.rust-lang.org/edition-guide/
1939 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1940 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1943 "detects edition keywords being used as an identifier",
1944 @future_incompatible = FutureIncompatibleInfo {
1945 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1946 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1951 /// Check for uses of edition keywords used as an identifier.
1952 KeywordIdents => [KEYWORD_IDENTS]
1955 struct UnderMacro(bool);
1957 impl KeywordIdents {
1958 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1959 for tt in tokens.into_trees() {
1961 // Only report non-raw idents.
1962 TokenTree::Token(token, _) => {
1963 if let Some((ident, false)) = token.ident() {
1964 self.check_ident_token(cx, UnderMacro(true), ident);
1967 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1972 fn check_ident_token(
1974 cx: &EarlyContext<'_>,
1975 UnderMacro(under_macro): UnderMacro,
1978 let next_edition = match cx.sess().edition() {
1979 Edition::Edition2015 => {
1981 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1983 // rust-lang/rust#56327: Conservatively do not
1984 // attempt to report occurrences of `dyn` within
1985 // macro definitions or invocations, because `dyn`
1986 // can legitimately occur as a contextual keyword
1987 // in 2015 code denoting its 2018 meaning, and we
1988 // do not want rustfix to inject bugs into working
1989 // code by rewriting such occurrences.
1991 // But if we see `dyn` outside of a macro, we know
1992 // its precise role in the parsed AST and thus are
1993 // assured this is truly an attempt to use it as
1995 kw::Dyn if !under_macro => Edition::Edition2018,
2001 // There are no new keywords yet for the 2018 edition and beyond.
2005 // Don't lint `r#foo`.
2006 if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2010 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2011 lint.build(fluent::lint::builtin_keyword_idents)
2012 .set_arg("kw", ident.clone())
2013 .set_arg("next", next_edition)
2016 fluent::lint::suggestion,
2017 format!("r#{}", ident),
2018 Applicability::MachineApplicable,
2025 impl EarlyLintPass for KeywordIdents {
2026 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2027 self.check_tokens(cx, mac_def.body.inner_tokens());
2029 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2030 self.check_tokens(cx, mac.args.inner_tokens());
2032 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2033 self.check_ident_token(cx, UnderMacro(false), ident);
2037 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2039 impl ExplicitOutlivesRequirements {
2040 fn lifetimes_outliving_lifetime<'tcx>(
2041 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2043 ) -> Vec<ty::Region<'tcx>> {
2046 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2047 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2048 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2056 fn lifetimes_outliving_type<'tcx>(
2057 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2059 ) -> Vec<ty::Region<'tcx>> {
2062 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2063 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2064 a.is_param(index).then_some(b)
2071 fn collect_outlives_bound_spans<'tcx>(
2074 bounds: &hir::GenericBounds<'_>,
2075 inferred_outlives: &[ty::Region<'tcx>],
2076 ) -> Vec<(usize, Span)> {
2077 use rustc_middle::middle::resolve_lifetime::Region;
2082 .filter_map(|(i, bound)| {
2083 if let hir::GenericBound::Outlives(lifetime) = bound {
2084 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2085 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2086 if let ty::ReEarlyBound(ebr) = **r { ebr.index == index } else { false }
2090 is_inferred.then_some((i, bound.span()))
2095 .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
2099 fn consolidate_outlives_bound_spans(
2102 bounds: &hir::GenericBounds<'_>,
2103 bound_spans: Vec<(usize, Span)>,
2105 if bounds.is_empty() {
2108 if bound_spans.len() == bounds.len() {
2109 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2110 // If all bounds are inferable, we want to delete the colon, so
2111 // start from just after the parameter (span passed as argument)
2112 vec![lo.to(last_bound_span)]
2114 let mut merged = Vec::new();
2115 let mut last_merged_i = None;
2117 let mut from_start = true;
2118 for (i, bound_span) in bound_spans {
2119 match last_merged_i {
2120 // If the first bound is inferable, our span should also eat the leading `+`.
2122 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2123 last_merged_i = Some(0);
2125 // If consecutive bounds are inferable, merge their spans
2126 Some(h) if i == h + 1 => {
2127 if let Some(tail) = merged.last_mut() {
2128 // Also eat the trailing `+` if the first
2129 // more-than-one bound is inferable
2130 let to_span = if from_start && i < bounds.len() {
2131 bounds[i + 1].span().shrink_to_lo()
2135 *tail = tail.to(to_span);
2136 last_merged_i = Some(i);
2138 bug!("another bound-span visited earlier");
2142 // When we find a non-inferable bound, subsequent inferable bounds
2143 // won't be consecutive from the start (and we'll eat the leading
2144 // `+` rather than the trailing one)
2146 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2147 last_merged_i = Some(i);
2156 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2157 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2158 use rustc_middle::middle::resolve_lifetime::Region;
2160 let def_id = item.def_id;
2161 if let hir::ItemKind::Struct(_, ref hir_generics)
2162 | hir::ItemKind::Enum(_, ref hir_generics)
2163 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2165 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2166 if inferred_outlives.is_empty() {
2170 let ty_generics = cx.tcx.generics_of(def_id);
2172 let mut bound_count = 0;
2173 let mut lint_spans = Vec::new();
2174 let mut where_lint_spans = Vec::new();
2175 let mut dropped_predicate_count = 0;
2176 let num_predicates = hir_generics.predicates.len();
2177 for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2178 let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
2179 hir::WherePredicate::RegionPredicate(predicate) => {
2180 if let Some(Region::EarlyBound(index, ..)) =
2181 cx.tcx.named_region(predicate.lifetime.hir_id)
2184 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2187 predicate.in_where_clause,
2193 hir::WherePredicate::BoundPredicate(predicate) => {
2194 // FIXME we can also infer bounds on associated types,
2195 // and should check for them here.
2196 match predicate.bounded_ty.kind {
2197 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2198 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2201 let index = ty_generics.param_def_id_to_index[&def_id];
2203 Self::lifetimes_outliving_type(inferred_outlives, index),
2206 predicate.origin == PredicateOrigin::WhereClause,
2216 if relevant_lifetimes.is_empty() {
2221 self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
2222 bound_count += bound_spans.len();
2224 let drop_predicate = bound_spans.len() == bounds.len();
2226 dropped_predicate_count += 1;
2229 if drop_predicate && !in_where_clause {
2230 lint_spans.push(span);
2231 } else if drop_predicate && i + 1 < num_predicates {
2232 // If all the bounds on a predicate were inferable and there are
2233 // further predicates, we want to eat the trailing comma.
2234 let next_predicate_span = hir_generics.predicates[i + 1].span();
2235 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2237 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2238 span.shrink_to_lo(),
2245 // If all predicates are inferable, drop the entire clause
2246 // (including the `where`)
2247 if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2249 let where_span = hir_generics.where_clause_span;
2250 // Extend the where clause back to the closing `>` of the
2251 // generics, except for tuple struct, which have the `where`
2252 // after the fields of the struct.
2253 let full_where_span =
2254 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2257 hir_generics.span.shrink_to_hi().to(where_span)
2259 lint_spans.push(full_where_span);
2261 lint_spans.extend(where_lint_spans);
2264 if !lint_spans.is_empty() {
2265 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2266 lint.build(fluent::lint::builtin_explicit_outlives)
2267 .set_arg("count", bound_count)
2268 .multipart_suggestion(
2269 fluent::lint::suggestion,
2272 .map(|span| (span, String::new()))
2273 .collect::<Vec<_>>(),
2274 Applicability::MachineApplicable,
2284 /// The `incomplete_features` lint detects unstable features enabled with
2285 /// the [`feature` attribute] that may function improperly in some or all
2288 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2293 /// #![feature(generic_const_exprs)]
2300 /// Although it is encouraged for people to experiment with unstable
2301 /// features, some of them are known to be incomplete or faulty. This lint
2302 /// is a signal that the feature has not yet been finished, and you may
2303 /// experience problems with it.
2304 pub INCOMPLETE_FEATURES,
2306 "incomplete features that may function improperly in some or all cases"
2310 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2311 IncompleteFeatures => [INCOMPLETE_FEATURES]
2314 impl EarlyLintPass for IncompleteFeatures {
2315 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2316 let features = cx.sess().features_untracked();
2318 .declared_lang_features
2320 .map(|(name, span, _)| (name, span))
2321 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2322 .filter(|(&name, _)| features.incomplete(name))
2323 .for_each(|(&name, &span)| {
2324 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2325 let mut builder = lint.build(fluent::lint::builtin_incomplete_features);
2326 builder.set_arg("name", name);
2327 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2328 builder.set_arg("n", n);
2329 builder.note(fluent::lint::note);
2331 if HAS_MIN_FEATURES.contains(&name) {
2332 builder.help(fluent::lint::help);
2340 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2343 /// The `invalid_value` lint detects creating a value that is not valid,
2344 /// such as a null reference.
2349 /// # #![allow(unused)]
2351 /// let x: &'static i32 = std::mem::zeroed();
2359 /// In some situations the compiler can detect that the code is creating
2360 /// an invalid value, which should be avoided.
2362 /// In particular, this lint will check for improper use of
2363 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2364 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2365 /// lint should provide extra information to indicate what the problem is
2366 /// and a possible solution.
2368 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2369 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2370 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2371 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2372 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2375 "an invalid value is being created (such as a null reference)"
2378 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2380 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2381 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2382 #[derive(Debug, Copy, Clone, PartialEq)]
2388 /// Information about why a type cannot be initialized this way.
2389 /// Contains an error message and optionally a span to point at.
2390 type InitError = (String, Option<Span>);
2392 /// Test if this constant is all-0.
2393 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2394 use hir::ExprKind::*;
2395 use rustc_ast::LitKind::*;
2398 if let Int(i, _) = lit.node {
2404 Tup(tup) => tup.iter().all(is_zero),
2409 /// Determine if this expression is a "dangerous initialization".
2410 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2411 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2412 // Find calls to `mem::{uninitialized,zeroed}` methods.
2413 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2414 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2415 match cx.tcx.get_diagnostic_name(def_id) {
2416 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2417 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2418 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2422 } else if let hir::ExprKind::MethodCall(_, ref args, _) = expr.kind {
2423 // Find problematic calls to `MaybeUninit::assume_init`.
2424 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2425 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2426 // This is a call to *some* method named `assume_init`.
2427 // See if the `self` parameter is one of the dangerous constructors.
2428 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2429 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2430 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2431 match cx.tcx.get_diagnostic_name(def_id) {
2432 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2433 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2444 /// Test if this enum has several actually "existing" variants.
2445 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2446 fn is_multi_variant<'tcx>(adt: ty::AdtDef<'tcx>) -> bool {
2447 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2448 let existing_variants = adt.variants().iter().filter(|v| v.fields.is_empty()).count();
2449 existing_variants > 1
2452 /// Return `Some` only if we are sure this type does *not*
2453 /// allow zero initialization.
2454 fn ty_find_init_error<'tcx>(
2455 cx: &LateContext<'tcx>,
2458 ) -> Option<InitError> {
2459 use rustc_type_ir::sty::TyKind::*;
2461 // Primitive types that don't like 0 as a value.
2462 Ref(..) => Some(("references must be non-null".to_string(), None)),
2463 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2464 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2465 Never => Some(("the `!` type has no valid value".to_string(), None)),
2466 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2467 // raw ptr to dyn Trait
2469 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2471 // Primitive types with other constraints.
2472 Bool if init == InitKind::Uninit => {
2473 Some(("booleans must be either `true` or `false`".to_string(), None))
2475 Char if init == InitKind::Uninit => {
2476 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2478 // Recurse and checks for some compound types.
2479 Adt(adt_def, substs) if !adt_def.is_union() => {
2480 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2481 use std::ops::Bound;
2482 match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
2483 // We exploit here that `layout_scalar_valid_range` will never
2484 // return `Bound::Excluded`. (And we have tests checking that we
2485 // handle the attribute correctly.)
2486 (Bound::Included(lo), _) if lo > 0 => {
2487 return Some((format!("`{}` must be non-null", ty), None));
2489 (Bound::Included(_), _) | (_, Bound::Included(_))
2490 if init == InitKind::Uninit =>
2494 "`{}` must be initialized inside its custom valid range",
2503 match adt_def.variants().len() {
2504 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2506 // Struct, or enum with exactly one variant.
2507 // Proceed recursively, check all fields.
2508 let variant = &adt_def.variant(VariantIdx::from_u32(0));
2509 variant.fields.iter().find_map(|field| {
2510 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(
2513 // Point to this field, should be helpful for figuring
2514 // out where the source of the error is.
2515 let span = cx.tcx.def_span(field.did);
2518 " (in this {} field)",
2531 // Multi-variant enum.
2533 if init == InitKind::Uninit && is_multi_variant(*adt_def) {
2534 let span = cx.tcx.def_span(adt_def.did());
2536 "enums have to be initialized to a variant".to_string(),
2540 // In principle, for zero-initialization we could figure out which variant corresponds
2541 // to tag 0, and check that... but for now we just accept all zero-initializations.
2548 // Proceed recursively, check all fields.
2549 ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2552 if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2553 // Array length known at array non-empty -- recurse.
2554 ty_find_init_error(cx, *ty, init)
2556 // Empty array or size unknown.
2560 // Conservative fallback.
2565 if let Some(init) = is_dangerous_init(cx, expr) {
2566 // This conjures an instance of a type out of nothing,
2567 // using zeroed or uninitialized memory.
2568 // We are extremely conservative with what we warn about.
2569 let conjured_ty = cx.typeck_results().expr_ty(expr);
2570 if let Some((msg, span)) =
2571 with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2573 // FIXME(davidtwco): make translatable
2574 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2575 let mut err = lint.build(&format!(
2576 "the type `{}` does not permit {}",
2579 InitKind::Zeroed => "zero-initialization",
2580 InitKind::Uninit => "being left uninitialized",
2583 err.span_label(expr.span, "this code causes undefined behavior when executed");
2586 "help: use `MaybeUninit<T>` instead, \
2587 and only call `assume_init` after initialization is done",
2589 if let Some(span) = span {
2590 err.span_note(span, &msg);
2602 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2603 /// has been declared with the same name but different types.
2623 /// Because two symbols of the same name cannot be resolved to two
2624 /// different functions at link time, and one function cannot possibly
2625 /// have two types, a clashing extern declaration is almost certainly a
2626 /// mistake. Check to make sure that the `extern` definitions are correct
2627 /// and equivalent, and possibly consider unifying them in one location.
2629 /// This lint does not run between crates because a project may have
2630 /// dependencies which both rely on the same extern function, but declare
2631 /// it in a different (but valid) way. For example, they may both declare
2632 /// an opaque type for one or more of the arguments (which would end up
2633 /// distinct types), or use types that are valid conversions in the
2634 /// language the `extern fn` is defined in. In these cases, the compiler
2635 /// can't say that the clashing declaration is incorrect.
2636 pub CLASHING_EXTERN_DECLARATIONS,
2638 "detects when an extern fn has been declared with the same name but different types"
2641 pub struct ClashingExternDeclarations {
2642 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2643 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2644 /// the symbol should be reported as a clashing declaration.
2645 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2646 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2647 seen_decls: FxHashMap<Symbol, HirId>,
2650 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2651 /// just from declaration itself. This is important because we don't want to report clashes on
2652 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2655 /// The name of the symbol + the span of the annotation which introduced the link name.
2657 /// No link name, so just the name of the symbol.
2662 fn get_name(&self) -> Symbol {
2664 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2669 impl ClashingExternDeclarations {
2670 pub(crate) fn new() -> Self {
2671 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2673 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2674 /// for the item, return its HirId without updating the set.
2675 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2676 let did = fi.def_id.to_def_id();
2677 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2678 let name = Symbol::intern(tcx.symbol_name(instance).name);
2679 if let Some(&hir_id) = self.seen_decls.get(&name) {
2680 // Avoid updating the map with the new entry when we do find a collision. We want to
2681 // make sure we're always pointing to the first definition as the previous declaration.
2682 // This lets us avoid emitting "knock-on" diagnostics.
2685 self.seen_decls.insert(name, fi.hir_id())
2689 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2690 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2692 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2693 if let Some((overridden_link_name, overridden_link_name_span)) =
2694 tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2695 // FIXME: Instead of searching through the attributes again to get span
2696 // information, we could have codegen_fn_attrs also give span information back for
2697 // where the attribute was defined. However, until this is found to be a
2698 // bottleneck, this does just fine.
2700 overridden_link_name,
2701 tcx.get_attr(fi.def_id.to_def_id(), sym::link_name).unwrap().span,
2705 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2707 SymbolName::Normal(fi.ident.name)
2711 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2712 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2713 /// with the same members (as the declarations shouldn't clash).
2714 fn structurally_same_type<'tcx>(
2715 cx: &LateContext<'tcx>,
2720 fn structurally_same_type_impl<'tcx>(
2721 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2722 cx: &LateContext<'tcx>,
2727 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2730 // Given a transparent newtype, reach through and grab the inner
2731 // type unless the newtype makes the type non-null.
2732 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2735 if let ty::Adt(def, substs) = *ty.kind() {
2736 let is_transparent = def.repr().transparent();
2737 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2739 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2740 ty, is_transparent, is_non_null
2742 if is_transparent && !is_non_null {
2743 debug_assert!(def.variants().len() == 1);
2744 let v = &def.variant(VariantIdx::new(0));
2745 ty = transparent_newtype_field(tcx, v)
2747 "single-variant transparent structure with zero-sized field",
2753 debug!("non_transparent_ty -> {:?}", ty);
2758 let a = non_transparent_ty(a);
2759 let b = non_transparent_ty(b);
2761 if !seen_types.insert((a, b)) {
2762 // We've encountered a cycle. There's no point going any further -- the types are
2763 // structurally the same.
2768 // All nominally-same types are structurally same, too.
2771 // Do a full, depth-first comparison between the two.
2772 use rustc_type_ir::sty::TyKind::*;
2773 let a_kind = a.kind();
2774 let b_kind = b.kind();
2776 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2777 debug!("compare_layouts({:?}, {:?})", a, b);
2778 let a_layout = &cx.layout_of(a)?.layout.abi();
2779 let b_layout = &cx.layout_of(b)?.layout.abi();
2781 "comparing layouts: {:?} == {:?} = {}",
2784 a_layout == b_layout
2786 Ok(a_layout == b_layout)
2789 #[allow(rustc::usage_of_ty_tykind)]
2790 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2791 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2794 ensure_sufficient_stack(|| {
2795 match (a_kind, b_kind) {
2796 (Adt(a_def, _), Adt(b_def, _)) => {
2797 // We can immediately rule out these types as structurally same if
2798 // their layouts differ.
2799 match compare_layouts(a, b) {
2800 Ok(false) => return false,
2801 _ => (), // otherwise, continue onto the full, fields comparison
2804 // Grab a flattened representation of all fields.
2805 let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2806 let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2808 // Perform a structural comparison for each field.
2811 |&ty::FieldDef { did: a_did, .. },
2812 &ty::FieldDef { did: b_did, .. }| {
2813 structurally_same_type_impl(
2823 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2824 // For arrays, we also check the constness of the type.
2825 a_const.kind() == b_const.kind()
2826 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2828 (Slice(a_ty), Slice(b_ty)) => {
2829 structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2831 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2832 a_tymut.mutbl == b_tymut.mutbl
2833 && structurally_same_type_impl(
2834 seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2837 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2838 // For structural sameness, we don't need the region to be same.
2840 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2842 (FnDef(..), FnDef(..)) => {
2843 let a_poly_sig = a.fn_sig(tcx);
2844 let b_poly_sig = b.fn_sig(tcx);
2846 // We don't compare regions, but leaving bound regions around ICEs, so
2848 let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
2849 let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
2851 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2852 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2853 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2854 structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2856 && structurally_same_type_impl(
2864 (Tuple(a_substs), Tuple(b_substs)) => {
2865 a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2866 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2869 // For these, it's not quite as easy to define structural-sameness quite so easily.
2870 // For the purposes of this lint, take the conservative approach and mark them as
2871 // not structurally same.
2872 (Dynamic(..), Dynamic(..))
2873 | (Error(..), Error(..))
2874 | (Closure(..), Closure(..))
2875 | (Generator(..), Generator(..))
2876 | (GeneratorWitness(..), GeneratorWitness(..))
2877 | (Projection(..), Projection(..))
2878 | (Opaque(..), Opaque(..)) => false,
2880 // These definitely should have been caught above.
2881 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2883 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2884 // enum layout optimisation is being applied.
2885 (Adt(..), other_kind) | (other_kind, Adt(..))
2886 if is_primitive_or_pointer(other_kind) =>
2888 let (primitive, adt) =
2889 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2890 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2893 compare_layouts(a, b).unwrap_or(false)
2896 // Otherwise, just compare the layouts. This may fail to lint for some
2897 // incompatible types, but at the very least, will stop reads into
2898 // uninitialised memory.
2899 _ => compare_layouts(a, b).unwrap_or(false),
2904 let mut seen_types = FxHashSet::default();
2905 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2909 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2911 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2912 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2913 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2914 if let ForeignItemKind::Fn(..) = this_fi.kind {
2916 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2917 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2918 let this_decl_ty = tcx.type_of(this_fi.def_id);
2920 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2921 existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2923 // Check that the declarations match.
2924 if !Self::structurally_same_type(
2928 CItemKind::Declaration,
2930 let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
2931 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2933 // We want to ensure that we use spans for both decls that include where the
2934 // name was defined, whether that was from the link_name attribute or not.
2935 let get_relevant_span =
2936 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2937 SymbolName::Normal(_) => fi.span,
2938 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2940 // Finally, emit the diagnostic.
2941 tcx.struct_span_lint_hir(
2942 CLASHING_EXTERN_DECLARATIONS,
2944 get_relevant_span(this_fi),
2946 let mut expected_str = DiagnosticStyledString::new();
2947 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2948 let mut found_str = DiagnosticStyledString::new();
2949 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2951 lint.build(if orig.get_name() == this_fi.ident.name {
2952 fluent::lint::builtin_clashing_extern_same_name
2954 fluent::lint::builtin_clashing_extern_diff_name
2956 .set_arg("this_fi", this_fi.ident.name)
2957 .set_arg("orig", orig.get_name())
2959 get_relevant_span(orig_fi),
2960 fluent::lint::previous_decl_label,
2962 .span_label(get_relevant_span(this_fi), fluent::lint::mismatch_label)
2963 // FIXME(davidtwco): translatable expected/found
2964 .note_expected_found(&"", expected_str, &"", found_str)
2975 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
2976 /// which causes [undefined behavior].
2981 /// # #![allow(unused)]
2984 /// let x = &*ptr::null::<i32>();
2985 /// let x = ptr::addr_of!(*ptr::null::<i32>());
2986 /// let x = *(0 as *const i32);
2994 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
2995 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
2997 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3000 "detects when an null pointer is dereferenced"
3003 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3005 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3006 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3007 /// test if expression is a null ptr
3008 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3010 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3011 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3012 return is_zero(expr) || is_null_ptr(cx, expr);
3015 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3016 rustc_hir::ExprKind::Call(ref path, _) => {
3017 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3018 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3020 cx.tcx.get_diagnostic_name(def_id),
3021 Some(sym::ptr_null | sym::ptr_null_mut)
3031 /// test if expression is the literal `0`
3032 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3034 rustc_hir::ExprKind::Lit(ref lit) => {
3035 if let LitKind::Int(a, _) = lit.node {
3044 if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3045 if is_null_ptr(cx, expr_deref) {
3046 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3047 let mut err = lint.build(fluent::lint::builtin_deref_nullptr);
3048 err.span_label(expr.span, fluent::lint::label);
3057 /// The `named_asm_labels` lint detects the use of named labels in the
3058 /// inline `asm!` macro.
3062 /// ```rust,compile_fail
3063 /// use std::arch::asm;
3067 /// asm!("foo: bar");
3076 /// LLVM is allowed to duplicate inline assembly blocks for any
3077 /// reason, for example when it is in a function that gets inlined. Because
3078 /// of this, GNU assembler [local labels] *must* be used instead of labels
3079 /// with a name. Using named labels might cause assembler or linker errors.
3081 /// See the explanation in [Rust By Example] for more details.
3083 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3084 /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3085 pub NAMED_ASM_LABELS,
3087 "named labels in inline assembly",
3090 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3092 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3093 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3095 kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3099 for (template_sym, template_snippet, template_span) in template_strs.iter() {
3100 let template_str = template_sym.as_str();
3101 let find_label_span = |needle: &str| -> Option<Span> {
3102 if let Some(template_snippet) = template_snippet {
3103 let snippet = template_snippet.as_str();
3104 if let Some(pos) = snippet.find(needle) {
3108 .unwrap_or(snippet[pos..].len() - 1);
3109 let inner = InnerSpan::new(pos, end);
3110 return Some(template_span.from_inner(inner));
3117 let mut found_labels = Vec::new();
3119 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3120 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3121 for statement in statements {
3122 // If there's a comment, trim it from the statement
3123 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3124 let mut start_idx = 0;
3125 for (idx, _) in statement.match_indices(':') {
3126 let possible_label = statement[start_idx..idx].trim();
3127 let mut chars = possible_label.chars();
3128 let Some(c) = chars.next() else {
3129 // Empty string means a leading ':' in this section, which is not a label
3132 // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3133 if (c.is_alphabetic() || matches!(c, '.' | '_'))
3134 && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3136 found_labels.push(possible_label);
3138 // If we encounter a non-label, there cannot be any further labels, so stop checking
3142 start_idx = idx + 1;
3146 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3148 if found_labels.len() > 0 {
3149 let spans = found_labels
3151 .filter_map(|label| find_label_span(label))
3152 .collect::<Vec<Span>>();
3153 // If there were labels but we couldn't find a span, combine the warnings and use the template span
3154 let target_spans: MultiSpan =
3155 if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3157 cx.lookup_with_diagnostics(
3161 diag.build(fluent::lint::builtin_asm_labels).emit();
3163 BuiltinLintDiagnostics::NamedAsmLabel(
3164 "only local labels of the form `<number>:` should be used in inline asm"