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 errors::BuiltinEllpisisInclusiveRangePatterns,
25 types::{transparent_newtype_field, CItemKind},
26 EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
30 use rustc_ast::tokenstream::{TokenStream, TokenTree};
31 use rustc_ast::visit::{FnCtxt, FnKind};
32 use rustc_ast::{self as ast, *};
33 use rustc_ast_pretty::pprust::{self, expr_to_string};
34 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
35 use rustc_data_structures::stack::ensure_sufficient_stack;
37 fluent, Applicability, DelayDm, Diagnostic, DiagnosticBuilder, DiagnosticMessage,
38 DiagnosticStyledString, MultiSpan,
40 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
42 use rustc_hir::def::{DefKind, Res};
43 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
44 use rustc_hir::intravisit::FnKind as HirFnKind;
46 Body, FnDecl, ForeignItemKind, GenericParamKind, HirId, Node, PatKind, PredicateOrigin,
48 use rustc_index::vec::Idx;
49 use rustc_middle::lint::in_external_macro;
50 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
51 use rustc_middle::ty::print::with_no_trimmed_paths;
52 use rustc_middle::ty::subst::GenericArgKind;
53 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, VariantDef};
54 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
55 use rustc_span::edition::Edition;
56 use rustc_span::source_map::Spanned;
57 use rustc_span::symbol::{kw, sym, Ident, Symbol};
58 use rustc_span::{BytePos, InnerSpan, Span};
59 use rustc_target::abi::{Abi, VariantIdx};
60 use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
61 use rustc_trait_selection::traits::{self, misc::can_type_implement_copy, EvaluationResult};
63 use crate::nonstandard_style::{method_context, MethodLateContext};
67 // hardwired lints from librustc_middle
68 pub use rustc_session::lint::builtin::*;
71 /// The `while_true` lint detects `while true { }`.
85 /// `while true` should be replaced with `loop`. A `loop` expression is
86 /// the preferred way to write an infinite loop because it more directly
87 /// expresses the intent of the loop.
90 "suggest using `loop { }` instead of `while true { }`"
93 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
95 /// Traverse through any amount of parenthesis and return the first non-parens expression.
96 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
97 while let ast::ExprKind::Paren(sub) = &expr.kind {
103 impl EarlyLintPass for WhileTrue {
105 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
106 if let ast::ExprKind::While(cond, _, label) = &e.kind
107 && let cond = pierce_parens(cond)
108 && let ast::ExprKind::Lit(token_lit) = cond.kind
109 && let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
110 && !cond.span.from_expansion()
112 let condition_span = e.span.with_hi(cond.span.hi());
116 fluent::lint_builtin_while_true,
118 lint.span_suggestion_short(
123 label.map_or_else(String::new, |label| format!(
128 Applicability::MachineApplicable,
137 /// The `box_pointers` lints use of the Box type.
141 /// ```rust,compile_fail
142 /// #![deny(box_pointers)]
152 /// This lint is mostly historical, and not particularly useful. `Box<T>`
153 /// used to be built into the language, and the only way to do heap
154 /// allocation. Today's Rust can call into other allocators, etc.
157 "use of owned (Box type) heap memory"
160 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
163 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
164 for leaf in ty.walk() {
165 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
166 if leaf_ty.is_box() {
170 fluent::lint_builtin_box_pointers,
171 |lint| lint.set_arg("ty", ty),
179 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
180 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
182 hir::ItemKind::Fn(..)
183 | hir::ItemKind::TyAlias(..)
184 | hir::ItemKind::Enum(..)
185 | hir::ItemKind::Struct(..)
186 | hir::ItemKind::Union(..) => {
187 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.owner_id))
192 // If it's a struct, we also have to check the fields' types
194 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
195 for field in struct_def.fields() {
196 self.check_heap_type(cx, field.span, cx.tcx.type_of(field.def_id));
203 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
204 let ty = cx.typeck_results().node_type(e.hir_id);
205 self.check_heap_type(cx, e.span, ty);
210 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
211 /// instead of `Struct { x }` in a pattern.
229 /// Point { x: x, y: y } => (),
238 /// The preferred style is to avoid the repetition of specifying both the
239 /// field name and the binding name if both identifiers are the same.
240 NON_SHORTHAND_FIELD_PATTERNS,
242 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
245 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
247 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
248 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
249 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
254 .expect("struct pattern type is not an ADT")
255 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
256 for fieldpat in field_pats {
257 if fieldpat.is_shorthand {
260 if fieldpat.span.from_expansion() {
261 // Don't lint if this is a macro expansion: macro authors
262 // shouldn't have to worry about this kind of style issue
266 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
267 if cx.tcx.find_field_index(ident, &variant)
268 == Some(cx.typeck_results().field_index(fieldpat.hir_id))
271 NON_SHORTHAND_FIELD_PATTERNS,
273 fluent::lint_builtin_non_shorthand_field_patterns,
275 let suggested_ident =
276 format!("{}{}", binding_annot.prefix_str(), ident);
277 lint.set_arg("ident", ident).span_suggestion(
281 Applicability::MachineApplicable,
293 /// The `unsafe_code` lint catches usage of `unsafe` code.
297 /// ```rust,compile_fail
298 /// #![deny(unsafe_code)]
310 /// This lint is intended to restrict the usage of `unsafe`, which can be
311 /// difficult to use correctly.
314 "usage of `unsafe` code"
317 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
322 cx: &EarlyContext<'_>,
324 msg: impl Into<DiagnosticMessage>,
325 decorate: impl for<'a, 'b> FnOnce(
326 &'b mut DiagnosticBuilder<'a, ()>,
327 ) -> &'b mut DiagnosticBuilder<'a, ()>,
329 // This comes from a macro that has `#[allow_internal_unsafe]`.
330 if span.allows_unsafe() {
334 cx.struct_span_lint(UNSAFE_CODE, span, msg, decorate);
337 fn report_overridden_symbol_name(
339 cx: &EarlyContext<'_>,
341 msg: DiagnosticMessage,
343 self.report_unsafe(cx, span, msg, |lint| {
344 lint.note(fluent::lint_builtin_overridden_symbol_name)
348 fn report_overridden_symbol_section(
350 cx: &EarlyContext<'_>,
352 msg: DiagnosticMessage,
354 self.report_unsafe(cx, span, msg, |lint| {
355 lint.note(fluent::lint_builtin_overridden_symbol_section)
360 impl EarlyLintPass for UnsafeCode {
361 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
362 if attr.has_name(sym::allow_internal_unsafe) {
363 self.report_unsafe(cx, attr.span, fluent::lint_builtin_allow_internal_unsafe, |lint| {
370 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
371 if let ast::ExprKind::Block(ref blk, _) = e.kind {
372 // Don't warn about generated blocks; that'll just pollute the output.
373 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
374 self.report_unsafe(cx, blk.span, fluent::lint_builtin_unsafe_block, |lint| lint);
379 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
381 ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => {
382 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_trait, |lint| lint)
385 ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => {
386 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_impl, |lint| lint)
389 ast::ItemKind::Fn(..) => {
390 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
391 self.report_overridden_symbol_name(
394 fluent::lint_builtin_no_mangle_fn,
398 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
399 self.report_overridden_symbol_name(
402 fluent::lint_builtin_export_name_fn,
406 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
407 self.report_overridden_symbol_section(
410 fluent::lint_builtin_link_section_fn,
415 ast::ItemKind::Static(..) => {
416 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
417 self.report_overridden_symbol_name(
420 fluent::lint_builtin_no_mangle_static,
424 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
425 self.report_overridden_symbol_name(
428 fluent::lint_builtin_export_name_static,
432 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
433 self.report_overridden_symbol_section(
436 fluent::lint_builtin_link_section_static,
445 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
446 if let ast::AssocItemKind::Fn(..) = it.kind {
447 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
448 self.report_overridden_symbol_name(
451 fluent::lint_builtin_no_mangle_method,
454 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
455 self.report_overridden_symbol_name(
458 fluent::lint_builtin_export_name_method,
464 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
468 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
474 let msg = match ctxt {
475 FnCtxt::Foreign => return,
476 FnCtxt::Free => fluent::lint_builtin_decl_unsafe_fn,
477 FnCtxt::Assoc(_) if body.is_none() => fluent::lint_builtin_decl_unsafe_method,
478 FnCtxt::Assoc(_) => fluent::lint_builtin_impl_unsafe_method,
480 self.report_unsafe(cx, span, msg, |lint| lint);
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.effective_visibilities.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);
583 cx.tcx.def_span(def_id),
584 fluent::lint_builtin_missing_doc,
585 |lint| lint.set_arg("article", article).set_arg("desc", desc),
591 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
593 fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
594 let doc_hidden = self.doc_hidden()
595 || attrs.iter().any(|attr| {
596 attr.has_name(sym::doc)
597 && match attr.meta_item_list() {
599 Some(l) => attr::list_contains_name(&l, sym::hidden),
602 self.doc_hidden_stack.push(doc_hidden);
605 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
606 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
609 fn check_crate(&mut self, cx: &LateContext<'_>) {
610 self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
613 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
615 hir::ItemKind::Trait(..) => {
616 // Issue #11592: traits are always considered exported, even when private.
617 if cx.tcx.visibility(it.owner_id)
618 == ty::Visibility::Restricted(
619 cx.tcx.parent_module_from_def_id(it.owner_id.def_id).to_def_id(),
625 hir::ItemKind::TyAlias(..)
626 | hir::ItemKind::Fn(..)
627 | hir::ItemKind::Macro(..)
628 | hir::ItemKind::Mod(..)
629 | hir::ItemKind::Enum(..)
630 | hir::ItemKind::Struct(..)
631 | hir::ItemKind::Union(..)
632 | hir::ItemKind::Const(..)
633 | hir::ItemKind::Static(..) => {}
638 let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
640 self.check_missing_docs_attrs(cx, it.owner_id.def_id, article, desc);
643 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
644 let (article, desc) = cx.tcx.article_and_description(trait_item.owner_id.to_def_id());
646 self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, article, desc);
649 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
650 // If the method is an impl for a trait, don't doc.
651 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
655 // If the method is an impl for an item with docs_hidden, don't doc.
656 if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
657 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
658 let impl_ty = cx.tcx.type_of(parent);
659 let outerdef = match impl_ty.kind() {
660 ty::Adt(def, _) => Some(def.did()),
661 ty::Foreign(def_id) => Some(*def_id),
664 let is_hidden = match outerdef {
665 Some(id) => cx.tcx.is_doc_hidden(id),
673 let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
674 self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);
677 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
678 let (article, desc) = cx.tcx.article_and_description(foreign_item.owner_id.to_def_id());
679 self.check_missing_docs_attrs(cx, foreign_item.owner_id.def_id, article, desc);
682 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
683 if !sf.is_positional() {
684 self.check_missing_docs_attrs(cx, sf.def_id, "a", "struct field")
688 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
689 self.check_missing_docs_attrs(cx, v.def_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.effective_visibilities.is_reachable(item.owner_id.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.owner_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.owner_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.owner_id);
754 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
758 if def.has_dtor(cx.tcx) {
762 // If the type contains a raw pointer, it may represent something like a handle,
763 // and recommending Copy might be a bad idea.
764 for field in def.all_fields() {
766 if cx.tcx.type_of(did).is_unsafe_ptr() {
770 let param_env = ty::ParamEnv::empty();
771 if ty.is_copy_modulo_regions(cx.tcx, param_env) {
775 // We shouldn't recommend implementing `Copy` on stateful things,
776 // such as iterators.
777 if let Some(iter_trait) = cx.tcx.get_diagnostic_item(sym::Iterator) {
778 if cx.tcx.infer_ctxt().build().type_implements_trait(iter_trait, [ty], param_env)
779 == EvaluationResult::EvaluatedToOk
785 // Default value of clippy::trivially_copy_pass_by_ref
786 const MAX_SIZE: u64 = 256;
788 if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes()) {
794 if can_type_implement_copy(
798 traits::ObligationCause::misc(item.span, item.hir_id()),
803 MISSING_COPY_IMPLEMENTATIONS,
805 fluent::lint_builtin_missing_copy_impl,
813 /// The `missing_debug_implementations` lint detects missing
814 /// implementations of [`fmt::Debug`].
816 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
820 /// ```rust,compile_fail
821 /// #![deny(missing_debug_implementations)]
830 /// Having a `Debug` implementation on all types can assist with
831 /// debugging, as it provides a convenient way to format and display a
832 /// value. Using the `#[derive(Debug)]` attribute will automatically
833 /// generate a typical implementation, or a custom implementation can be
834 /// added by manually implementing the `Debug` trait.
836 /// This lint is "allow" by default because adding `Debug` to all types can
837 /// have a negative impact on compile time and code size. It also requires
838 /// boilerplate to be added to every type, which can be an impediment.
839 MISSING_DEBUG_IMPLEMENTATIONS,
841 "detects missing implementations of Debug"
845 pub struct MissingDebugImplementations {
846 impling_types: Option<LocalDefIdSet>,
849 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
851 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
852 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
853 if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
858 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
862 let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
866 if self.impling_types.is_none() {
867 let mut impls = LocalDefIdSet::default();
868 cx.tcx.for_each_impl(debug, |d| {
869 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
870 if let Some(def_id) = ty_def.did().as_local() {
871 impls.insert(def_id);
876 self.impling_types = Some(impls);
877 debug!("{:?}", self.impling_types);
880 if !self.impling_types.as_ref().unwrap().contains(&item.owner_id.def_id) {
882 MISSING_DEBUG_IMPLEMENTATIONS,
884 fluent::lint_builtin_missing_debug_impl,
885 |lint| lint.set_arg("debug", cx.tcx.def_path_str(debug)),
892 /// The `anonymous_parameters` lint detects anonymous parameters in trait
897 /// ```rust,edition2015,compile_fail
898 /// #![deny(anonymous_parameters)]
910 /// This syntax is mostly a historical accident, and can be worked around
911 /// quite easily by adding an `_` pattern or a descriptive identifier:
915 /// fn foo(_: usize);
919 /// This syntax is now a hard error in the 2018 edition. In the 2015
920 /// edition, this lint is "warn" by default. This lint
921 /// enables the [`cargo fix`] tool with the `--edition` flag to
922 /// automatically transition old code from the 2015 edition to 2018. The
923 /// tool will run this lint and automatically apply the
924 /// suggested fix from the compiler (which is to add `_` to each
925 /// parameter). This provides a completely automated way to update old
926 /// code for a new edition. See [issue #41686] for more details.
928 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
929 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
930 pub ANONYMOUS_PARAMETERS,
932 "detects anonymous parameters",
933 @future_incompatible = FutureIncompatibleInfo {
934 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
935 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
940 /// Checks for use of anonymous parameters (RFC 1685).
941 AnonymousParameters => [ANONYMOUS_PARAMETERS]
944 impl EarlyLintPass for AnonymousParameters {
945 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
946 if cx.sess().edition() != Edition::Edition2015 {
947 // This is a hard error in future editions; avoid linting and erroring
950 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
951 for arg in sig.decl.inputs.iter() {
952 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
953 if ident.name == kw::Empty {
954 let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
956 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
957 (snip.as_str(), Applicability::MachineApplicable)
959 ("<type>", Applicability::HasPlaceholders)
962 ANONYMOUS_PARAMETERS,
964 fluent::lint_builtin_anonymous_params,
966 lint.span_suggestion(
969 format!("_: {}", ty_snip),
981 /// Check for use of attributes which have been deprecated.
983 pub struct DeprecatedAttr {
984 // This is not free to compute, so we want to keep it around, rather than
985 // compute it for every attribute.
986 depr_attrs: Vec<&'static BuiltinAttribute>,
989 impl_lint_pass!(DeprecatedAttr => []);
991 impl DeprecatedAttr {
992 pub fn new() -> DeprecatedAttr {
993 DeprecatedAttr { depr_attrs: deprecated_attributes() }
997 impl EarlyLintPass for DeprecatedAttr {
998 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
999 for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
1000 if attr.ident().map(|ident| ident.name) == Some(*name) {
1001 if let &AttributeGate::Gated(
1002 Stability::Deprecated(link, suggestion),
1008 // FIXME(davidtwco) translatable deprecated attr
1009 cx.struct_span_lint(
1012 fluent::lint_builtin_deprecated_attr_link,
1014 lint.set_arg("name", name)
1015 .set_arg("reason", reason)
1016 .set_arg("link", link)
1017 .span_suggestion_short(
1019 suggestion.map(|s| s.into()).unwrap_or(
1020 fluent::lint_builtin_deprecated_attr_default_suggestion,
1023 Applicability::MachineApplicable,
1031 if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
1032 cx.struct_span_lint(
1035 fluent::lint_builtin_deprecated_attr_used,
1037 lint.set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
1038 .span_suggestion_short(
1040 fluent::lint_builtin_deprecated_attr_default_suggestion,
1042 Applicability::MachineApplicable,
1050 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1051 use rustc_ast::token::CommentKind;
1053 let mut attrs = attrs.iter().peekable();
1055 // Accumulate a single span for sugared doc comments.
1056 let mut sugared_span: Option<Span> = None;
1058 while let Some(attr) = attrs.next() {
1059 let is_doc_comment = attr.is_doc_comment();
1062 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1065 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1069 let span = sugared_span.take().unwrap_or(attr.span);
1071 if is_doc_comment || attr.has_name(sym::doc) {
1072 cx.struct_span_lint(
1073 UNUSED_DOC_COMMENTS,
1075 fluent::lint_builtin_unused_doc_comment,
1077 lint.set_arg("kind", node_kind).span_label(node_span, fluent::label).help(
1079 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1082 AttrKind::DocComment(CommentKind::Block, _) => fluent::block_help,
1091 impl EarlyLintPass for UnusedDocComment {
1092 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1093 let kind = match stmt.kind {
1094 ast::StmtKind::Local(..) => "statements",
1095 // Disabled pending discussion in #78306
1096 ast::StmtKind::Item(..) => return,
1097 // expressions will be reported by `check_expr`.
1098 ast::StmtKind::Empty
1099 | ast::StmtKind::Semi(_)
1100 | ast::StmtKind::Expr(_)
1101 | ast::StmtKind::MacCall(_) => return,
1104 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1107 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1108 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1109 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1112 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1113 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1116 fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1117 warn_if_doc(cx, param.ident.span, "generic parameters", ¶m.attrs);
1120 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1121 warn_if_doc(cx, block.span, "blocks", &block.attrs());
1124 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1125 if let ast::ItemKind::ForeignMod(_) = item.kind {
1126 warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1132 /// The `no_mangle_const_items` lint detects any `const` items with the
1133 /// [`no_mangle` attribute].
1135 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1139 /// ```rust,compile_fail
1141 /// const FOO: i32 = 5;
1148 /// Constants do not have their symbols exported, and therefore, this
1149 /// probably means you meant to use a [`static`], not a [`const`].
1151 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1152 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1153 NO_MANGLE_CONST_ITEMS,
1155 "const items will not have their symbols exported"
1159 /// The `no_mangle_generic_items` lint detects generic items that must be
1166 /// fn foo<T>(t: T) {
1175 /// A function with generics must have its symbol mangled to accommodate
1176 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1177 /// this situation, and should be removed.
1179 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1180 NO_MANGLE_GENERIC_ITEMS,
1182 "generic items must be mangled"
1185 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1187 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1188 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1189 let attrs = cx.tcx.hir().attrs(it.hir_id());
1190 let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1191 impl_generics: Option<&hir::Generics<'_>>,
1192 generics: &hir::Generics<'_>,
1195 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1198 GenericParamKind::Lifetime { .. } => {}
1199 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1200 cx.struct_span_lint(
1201 NO_MANGLE_GENERIC_ITEMS,
1203 fluent::lint_builtin_no_mangle_generic,
1205 lint.span_suggestion_short(
1206 no_mangle_attr.span,
1209 // Use of `#[no_mangle]` suggests FFI intent; correct
1210 // fix may be to monomorphize source by hand
1211 Applicability::MaybeIncorrect,
1221 hir::ItemKind::Fn(.., ref generics, _) => {
1222 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1223 check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1226 hir::ItemKind::Const(..) => {
1227 if cx.sess().contains_name(attrs, sym::no_mangle) {
1228 // Const items do not refer to a particular location in memory, and therefore
1229 // don't have anything to attach a symbol to
1230 cx.struct_span_lint(
1231 NO_MANGLE_CONST_ITEMS,
1233 fluent::lint_builtin_const_no_mangle,
1235 // account for "pub const" (#45562)
1240 .span_to_snippet(it.span)
1241 .map(|snippet| snippet.find("const").unwrap_or(0))
1242 .unwrap_or(0) as u32;
1243 // `const` is 5 chars
1244 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1245 lint.span_suggestion(
1249 Applicability::MachineApplicable,
1255 hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1257 if let hir::AssocItemKind::Fn { .. } = it.kind {
1258 if let Some(no_mangle_attr) = cx
1260 .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1262 check_no_mangle_on_generic_fn(
1265 cx.tcx.hir().get_generics(it.id.owner_id.def_id).unwrap(),
1278 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1279 /// T` because it is [undefined behavior].
1281 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1285 /// ```rust,compile_fail
1287 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1295 /// Certain assumptions are made about aliasing of data, and this transmute
1296 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1298 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1301 "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1304 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1306 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1307 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1308 if let Some((&ty::Ref(_, _, from_mutbl), &ty::Ref(_, _, to_mutbl))) =
1309 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1311 if from_mutbl < to_mutbl {
1312 cx.struct_span_lint(
1315 fluent::lint_builtin_mutable_transmutes,
1321 fn get_transmute_from_to<'tcx>(
1322 cx: &LateContext<'tcx>,
1323 expr: &hir::Expr<'_>,
1324 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1325 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1326 cx.qpath_res(qpath, expr.hir_id)
1330 if let Res::Def(DefKind::Fn, did) = def {
1331 if !def_id_is_transmute(cx, did) {
1334 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1335 let from = sig.inputs().skip_binder()[0];
1336 let to = sig.output().skip_binder();
1337 return Some((from, to));
1342 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1343 cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1349 /// The `unstable_features` is deprecated and should no longer be used.
1352 "enabling unstable features (deprecated. do not use)"
1356 /// Forbids using the `#[feature(...)]` attribute
1357 UnstableFeatures => [UNSTABLE_FEATURES]
1360 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1361 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1362 if attr.has_name(sym::feature) {
1363 if let Some(items) = attr.meta_item_list() {
1365 cx.struct_span_lint(
1368 fluent::lint_builtin_unstable_features,
1378 /// The `ungated_async_fn_track_caller` lint warns when the
1379 /// `#[track_caller]` attribute is used on an async function, method, or
1380 /// closure, without enabling the corresponding unstable feature flag.
1386 /// async fn foo() {}
1393 /// The attribute must be used in conjunction with the
1394 /// [`closure_track_caller` feature flag]. Otherwise, the `#[track_caller]`
1395 /// annotation will function as a no-op.
1397 /// [`closure_track_caller` feature flag]: https://doc.rust-lang.org/beta/unstable-book/language-features/closure-track-caller.html
1398 UNGATED_ASYNC_FN_TRACK_CALLER,
1400 "enabling track_caller on an async fn is a no-op unless the closure_track_caller feature is enabled"
1404 /// Explains corresponding feature flag must be enabled for the `#[track_caller] attribute to
1406 UngatedAsyncFnTrackCaller => [UNGATED_ASYNC_FN_TRACK_CALLER]
1409 impl<'tcx> LateLintPass<'tcx> for UngatedAsyncFnTrackCaller {
1412 cx: &LateContext<'_>,
1413 fn_kind: HirFnKind<'_>,
1414 _: &'tcx FnDecl<'_>,
1419 if fn_kind.asyncness() == IsAsync::Async
1420 && !cx.tcx.features().closure_track_caller
1421 && let attrs = cx.tcx.hir().attrs(hir_id)
1422 // Now, check if the function has the `#[track_caller]` attribute
1423 && let Some(attr) = attrs.iter().find(|attr| attr.has_name(sym::track_caller))
1425 cx.struct_span_lint(
1426 UNGATED_ASYNC_FN_TRACK_CALLER,
1428 fluent::lint_ungated_async_fn_track_caller,
1430 lint.span_label(span, fluent::label);
1431 rustc_session::parse::add_feature_diagnostics(
1433 &cx.tcx.sess.parse_sess,
1434 sym::closure_track_caller,
1444 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1449 /// ```rust,compile_fail
1450 /// #![deny(unreachable_pub)]
1462 /// A bare `pub` visibility may be misleading if the item is not actually
1463 /// publicly exported from the crate. The `pub(crate)` visibility is
1464 /// recommended to be used instead, which more clearly expresses the intent
1465 /// that the item is only visible within its own crate.
1467 /// This lint is "allow" by default because it will trigger for a large
1468 /// amount existing Rust code, and has some false-positives. Eventually it
1469 /// is desired for this to become warn-by-default.
1470 pub UNREACHABLE_PUB,
1472 "`pub` items not reachable from crate root"
1476 /// Lint for items marked `pub` that aren't reachable from other crates.
1477 UnreachablePub => [UNREACHABLE_PUB]
1480 impl UnreachablePub {
1483 cx: &LateContext<'_>,
1489 let mut applicability = Applicability::MachineApplicable;
1490 if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
1492 if vis_span.from_expansion() {
1493 applicability = Applicability::MaybeIncorrect;
1495 let def_span = cx.tcx.def_span(def_id);
1496 cx.struct_span_lint(
1499 fluent::lint_builtin_unreachable_pub,
1501 lint.set_arg("what", what);
1503 lint.span_suggestion(vis_span, fluent::suggestion, "pub(crate)", applicability);
1505 lint.help(fluent::help);
1514 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1515 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1516 // Do not warn for fake `use` statements.
1517 if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1520 self.perform_lint(cx, "item", item.owner_id.def_id, item.vis_span, true);
1523 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1524 self.perform_lint(cx, "item", foreign_item.owner_id.def_id, foreign_item.vis_span, true);
1527 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1528 let map = cx.tcx.hir();
1529 if matches!(map.get_parent(field.hir_id), Node::Variant(_)) {
1532 self.perform_lint(cx, "field", field.def_id, field.vis_span, false);
1535 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1536 // Only lint inherent impl items.
1537 if cx.tcx.associated_item(impl_item.owner_id).trait_item_def_id.is_none() {
1538 self.perform_lint(cx, "item", impl_item.owner_id.def_id, impl_item.vis_span, false);
1544 /// The `type_alias_bounds` lint detects bounds in type aliases.
1549 /// type SendVec<T: Send> = Vec<T>;
1556 /// The trait bounds in a type alias are currently ignored, and should not
1557 /// be included to avoid confusion. This was previously allowed
1558 /// unintentionally; this may become a hard error in the future.
1561 "bounds in type aliases are not enforced"
1565 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1566 /// They are relevant when using associated types, but otherwise neither checked
1567 /// at definition site nor enforced at use site.
1568 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1571 impl TypeAliasBounds {
1572 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1574 hir::QPath::TypeRelative(ref ty, _) => {
1575 // If this is a type variable, we found a `T::Assoc`.
1577 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1578 matches!(path.res, Res::Def(DefKind::TyParam, _))
1583 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1587 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1588 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1589 // bound. Let's see if this type does that.
1591 // We use a HIR visitor to walk the type.
1592 use rustc_hir::intravisit::{self, Visitor};
1593 struct WalkAssocTypes<'a> {
1594 err: &'a mut Diagnostic,
1596 impl Visitor<'_> for WalkAssocTypes<'_> {
1597 fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1598 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1599 self.err.span_help(span, fluent::lint_builtin_type_alias_bounds_help);
1601 intravisit::walk_qpath(self, qpath, id)
1605 // Let's go for a walk!
1606 let mut visitor = WalkAssocTypes { err };
1607 visitor.visit_ty(ty);
1611 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1612 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1613 let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1616 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1617 // Bounds are respected for `type X = impl Trait`
1620 // There must not be a where clause
1621 if type_alias_generics.predicates.is_empty() {
1625 let mut where_spans = Vec::new();
1626 let mut inline_spans = Vec::new();
1627 let mut inline_sugg = Vec::new();
1628 for p in type_alias_generics.predicates {
1629 let span = p.span();
1630 if p.in_where_clause() {
1631 where_spans.push(span);
1633 for b in p.bounds() {
1634 inline_spans.push(b.span());
1636 inline_sugg.push((span, String::new()));
1640 let mut suggested_changing_assoc_types = false;
1641 if !where_spans.is_empty() {
1642 cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_where_clause, |lint| {
1643 lint.set_span(where_spans);
1644 lint.span_suggestion(
1645 type_alias_generics.where_clause_span,
1648 Applicability::MachineApplicable,
1650 if !suggested_changing_assoc_types {
1651 TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1652 suggested_changing_assoc_types = true;
1658 if !inline_spans.is_empty() {
1659 cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_generic_bounds, |lint| {
1660 lint.set_span(inline_spans);
1661 lint.multipart_suggestion(
1664 Applicability::MachineApplicable,
1666 if !suggested_changing_assoc_types {
1667 TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1676 /// Lint constants that are erroneous.
1677 /// Without this lint, we might not get any diagnostic if the constant is
1678 /// unused within this crate, even though downstream crates can't use it
1679 /// without producing an error.
1680 UnusedBrokenConst => []
1683 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1684 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1686 hir::ItemKind::Const(_, body_id) => {
1687 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1688 // trigger the query once for all constants since that will already report the errors
1689 cx.tcx.ensure().const_eval_poly(def_id);
1691 hir::ItemKind::Static(_, _, body_id) => {
1692 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1693 cx.tcx.ensure().eval_static_initializer(def_id);
1701 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1702 /// any type parameters.
1707 /// #![feature(trivial_bounds)]
1708 /// pub struct A where i32: Copy;
1715 /// Usually you would not write a trait bound that you know is always
1716 /// true, or never true. However, when using macros, the macro may not
1717 /// know whether or not the constraint would hold or not at the time when
1718 /// generating the code. Currently, the compiler does not alert you if the
1719 /// constraint is always true, and generates an error if it is never true.
1720 /// The `trivial_bounds` feature changes this to be a warning in both
1721 /// cases, giving macros more freedom and flexibility to generate code,
1722 /// while still providing a signal when writing non-macro code that
1723 /// something is amiss.
1725 /// See [RFC 2056] for more details. This feature is currently only
1726 /// available on the nightly channel, see [tracking issue #48214].
1728 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1729 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1732 "these bounds don't depend on an type parameters"
1736 /// Lint for trait and lifetime bounds that don't depend on type parameters
1737 /// which either do nothing, or stop the item from being used.
1738 TrivialConstraints => [TRIVIAL_BOUNDS]
1741 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1742 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1743 use rustc_middle::ty::visit::TypeVisitable;
1744 use rustc_middle::ty::Clause;
1745 use rustc_middle::ty::PredicateKind::*;
1747 if cx.tcx.features().trivial_bounds {
1748 let predicates = cx.tcx.predicates_of(item.owner_id);
1749 for &(predicate, span) in predicates.predicates {
1750 let predicate_kind_name = match predicate.kind().skip_binder() {
1751 Clause(Clause::Trait(..)) => "trait",
1752 Clause(Clause::TypeOutlives(..)) |
1753 Clause(Clause::RegionOutlives(..)) => "lifetime",
1755 // Ignore projections, as they can only be global
1756 // if the trait bound is global
1757 Clause(Clause::Projection(..)) |
1758 // Ignore bounds that a user can't type
1764 ConstEvaluatable(..) |
1767 TypeWellFormedFromEnv(..) => continue,
1769 if predicate.is_global() {
1770 cx.struct_span_lint(
1773 fluent::lint_builtin_trivial_bounds,
1775 lint.set_arg("predicate_kind_name", predicate_kind_name)
1776 .set_arg("predicate", predicate)
1786 /// Does nothing as a lint pass, but registers some `Lint`s
1787 /// which are used by other parts of the compiler.
1791 NON_SHORTHAND_FIELD_PATTERNS,
1794 MISSING_COPY_IMPLEMENTATIONS,
1795 MISSING_DEBUG_IMPLEMENTATIONS,
1796 ANONYMOUS_PARAMETERS,
1797 UNUSED_DOC_COMMENTS,
1798 NO_MANGLE_CONST_ITEMS,
1799 NO_MANGLE_GENERIC_ITEMS,
1809 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1810 /// pattern], which is deprecated.
1812 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1816 /// ```rust,edition2018
1828 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1829 /// confusion with the [`..` range expression]. Use the new form instead.
1831 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1832 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1834 "`...` range patterns are deprecated",
1835 @future_incompatible = FutureIncompatibleInfo {
1836 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1837 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1842 pub struct EllipsisInclusiveRangePatterns {
1843 /// If `Some(_)`, suppress all subsequent pattern
1844 /// warnings for better diagnostics.
1845 node_id: Option<ast::NodeId>,
1848 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1850 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1851 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1852 if self.node_id.is_some() {
1853 // Don't recursively warn about patterns inside range endpoints.
1857 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1859 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1860 /// corresponding to the ellipsis.
1861 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1866 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1867 ) => Some((a.as_deref(), b, *span)),
1872 let (parenthesise, endpoints) = match &pat.kind {
1873 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1874 _ => (false, matches_ellipsis_pat(pat)),
1877 if let Some((start, end, join)) = endpoints {
1878 let msg = fluent::lint_builtin_ellipsis_inclusive_range_patterns;
1879 let suggestion = fluent::suggestion;
1881 self.node_id = Some(pat.id);
1882 let end = expr_to_string(&end);
1883 let replace = match start {
1884 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1885 None => format!("&(..={})", end),
1887 if join.edition() >= Edition::Edition2021 {
1888 cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1890 suggestion: pat.span,
1894 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg, |lint| {
1895 lint.span_suggestion(
1899 Applicability::MachineApplicable,
1904 let replace = "..=";
1905 if join.edition() >= Edition::Edition2021 {
1906 cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1909 replace: replace.to_string(),
1912 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg, |lint| {
1913 lint.span_suggestion_short(
1917 Applicability::MachineApplicable,
1925 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1926 if let Some(node_id) = self.node_id {
1927 if pat.id == node_id {
1935 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1936 /// that are not able to be run by the test harness because they are in a
1937 /// position where they are not nameable.
1939 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1947 /// // This test will not fail because it does not run.
1948 /// assert_eq!(1, 2);
1957 /// In order for the test harness to run a test, the test function must be
1958 /// located in a position where it can be accessed from the crate root.
1959 /// This generally means it must be defined in a module, and not anywhere
1960 /// else such as inside another function. The compiler previously allowed
1961 /// this without an error, so a lint was added as an alert that a test is
1962 /// not being used. Whether or not this should be allowed has not yet been
1963 /// decided, see [RFC 2471] and [issue #36629].
1965 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1966 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1967 UNNAMEABLE_TEST_ITEMS,
1969 "detects an item that cannot be named being marked as `#[test_case]`",
1970 report_in_external_macro
1973 pub struct UnnameableTestItems {
1974 boundary: Option<hir::OwnerId>, // Id of the item under which things are not nameable
1975 items_nameable: bool,
1978 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1980 impl UnnameableTestItems {
1981 pub fn new() -> Self {
1982 Self { boundary: None, items_nameable: true }
1986 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1987 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1988 if self.items_nameable {
1989 if let hir::ItemKind::Mod(..) = it.kind {
1991 self.items_nameable = false;
1992 self.boundary = Some(it.owner_id);
1997 let attrs = cx.tcx.hir().attrs(it.hir_id());
1998 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1999 cx.struct_span_lint(
2000 UNNAMEABLE_TEST_ITEMS,
2002 fluent::lint_builtin_unnameable_test_items,
2008 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
2009 if !self.items_nameable && self.boundary == Some(it.owner_id) {
2010 self.items_nameable = true;
2016 /// The `keyword_idents` lint detects edition keywords being used as an
2021 /// ```rust,edition2015,compile_fail
2022 /// #![deny(keyword_idents)]
2031 /// Rust [editions] allow the language to evolve without breaking
2032 /// backwards compatibility. This lint catches code that uses new keywords
2033 /// that are added to the language that are used as identifiers (such as a
2034 /// variable name, function name, etc.). If you switch the compiler to a
2035 /// new edition without updating the code, then it will fail to compile if
2036 /// you are using a new keyword as an identifier.
2038 /// You can manually change the identifiers to a non-keyword, or use a
2039 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
2041 /// This lint solves the problem automatically. It is "allow" by default
2042 /// because the code is perfectly valid in older editions. The [`cargo
2043 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
2044 /// and automatically apply the suggested fix from the compiler (which is
2045 /// to use a raw identifier). This provides a completely automated way to
2046 /// update old code for a new edition.
2048 /// [editions]: https://doc.rust-lang.org/edition-guide/
2049 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
2050 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
2053 "detects edition keywords being used as an identifier",
2054 @future_incompatible = FutureIncompatibleInfo {
2055 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
2056 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
2061 /// Check for uses of edition keywords used as an identifier.
2062 KeywordIdents => [KEYWORD_IDENTS]
2065 struct UnderMacro(bool);
2067 impl KeywordIdents {
2068 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
2069 for tt in tokens.into_trees() {
2071 // Only report non-raw idents.
2072 TokenTree::Token(token, _) => {
2073 if let Some((ident, false)) = token.ident() {
2074 self.check_ident_token(cx, UnderMacro(true), ident);
2077 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
2082 fn check_ident_token(
2084 cx: &EarlyContext<'_>,
2085 UnderMacro(under_macro): UnderMacro,
2088 let next_edition = match cx.sess().edition() {
2089 Edition::Edition2015 => {
2091 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
2093 // rust-lang/rust#56327: Conservatively do not
2094 // attempt to report occurrences of `dyn` within
2095 // macro definitions or invocations, because `dyn`
2096 // can legitimately occur as a contextual keyword
2097 // in 2015 code denoting its 2018 meaning, and we
2098 // do not want rustfix to inject bugs into working
2099 // code by rewriting such occurrences.
2101 // But if we see `dyn` outside of a macro, we know
2102 // its precise role in the parsed AST and thus are
2103 // assured this is truly an attempt to use it as
2105 kw::Dyn if !under_macro => Edition::Edition2018,
2111 // There are no new keywords yet for the 2018 edition and beyond.
2115 // Don't lint `r#foo`.
2116 if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2120 cx.struct_span_lint(
2123 fluent::lint_builtin_keyword_idents,
2125 lint.set_arg("kw", ident).set_arg("next", next_edition).span_suggestion(
2128 format!("r#{}", ident),
2129 Applicability::MachineApplicable,
2136 impl EarlyLintPass for KeywordIdents {
2137 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
2138 self.check_tokens(cx, mac_def.body.tokens.clone());
2140 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2141 self.check_tokens(cx, mac.args.tokens.clone());
2143 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2144 self.check_ident_token(cx, UnderMacro(false), ident);
2148 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2150 impl ExplicitOutlivesRequirements {
2151 fn lifetimes_outliving_lifetime<'tcx>(
2152 inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
2154 ) -> Vec<ty::Region<'tcx>> {
2157 .filter_map(|(clause, _)| match *clause {
2158 ty::Clause::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2159 ty::ReEarlyBound(ebr) if ebr.def_id == def_id => Some(b),
2167 fn lifetimes_outliving_type<'tcx>(
2168 inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
2170 ) -> Vec<ty::Region<'tcx>> {
2173 .filter_map(|(clause, _)| match *clause {
2174 ty::Clause::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2175 a.is_param(index).then_some(b)
2182 fn collect_outlives_bound_spans<'tcx>(
2185 bounds: &hir::GenericBounds<'_>,
2186 inferred_outlives: &[ty::Region<'tcx>],
2187 predicate_span: Span,
2188 ) -> Vec<(usize, Span)> {
2189 use rustc_middle::middle::resolve_lifetime::Region;
2194 .filter_map(|(i, bound)| {
2195 let hir::GenericBound::Outlives(lifetime) = bound else {
2199 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2200 Some(Region::EarlyBound(def_id)) => inferred_outlives
2202 .any(|r| matches!(**r, ty::ReEarlyBound(ebr) if { ebr.def_id == def_id })),
2210 let span = bound.span().find_ancestor_inside(predicate_span)?;
2211 if in_external_macro(tcx.sess, span) {
2220 fn consolidate_outlives_bound_spans(
2223 bounds: &hir::GenericBounds<'_>,
2224 bound_spans: Vec<(usize, Span)>,
2226 if bounds.is_empty() {
2229 if bound_spans.len() == bounds.len() {
2230 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2231 // If all bounds are inferable, we want to delete the colon, so
2232 // start from just after the parameter (span passed as argument)
2233 vec![lo.to(last_bound_span)]
2235 let mut merged = Vec::new();
2236 let mut last_merged_i = None;
2238 let mut from_start = true;
2239 for (i, bound_span) in bound_spans {
2240 match last_merged_i {
2241 // If the first bound is inferable, our span should also eat the leading `+`.
2243 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2244 last_merged_i = Some(0);
2246 // If consecutive bounds are inferable, merge their spans
2247 Some(h) if i == h + 1 => {
2248 if let Some(tail) = merged.last_mut() {
2249 // Also eat the trailing `+` if the first
2250 // more-than-one bound is inferable
2251 let to_span = if from_start && i < bounds.len() {
2252 bounds[i + 1].span().shrink_to_lo()
2256 *tail = tail.to(to_span);
2257 last_merged_i = Some(i);
2259 bug!("another bound-span visited earlier");
2263 // When we find a non-inferable bound, subsequent inferable bounds
2264 // won't be consecutive from the start (and we'll eat the leading
2265 // `+` rather than the trailing one)
2267 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2268 last_merged_i = Some(i);
2277 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2278 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2279 use rustc_middle::middle::resolve_lifetime::Region;
2281 let def_id = item.owner_id.def_id;
2282 if let hir::ItemKind::Struct(_, hir_generics)
2283 | hir::ItemKind::Enum(_, hir_generics)
2284 | hir::ItemKind::Union(_, hir_generics) = item.kind
2286 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2287 if inferred_outlives.is_empty() {
2291 let ty_generics = cx.tcx.generics_of(def_id);
2293 let mut bound_count = 0;
2294 let mut lint_spans = Vec::new();
2295 let mut where_lint_spans = Vec::new();
2296 let mut dropped_predicate_count = 0;
2297 let num_predicates = hir_generics.predicates.len();
2298 for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2299 let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
2300 match where_predicate {
2301 hir::WherePredicate::RegionPredicate(predicate) => {
2302 if let Some(Region::EarlyBound(region_def_id)) =
2303 cx.tcx.named_region(predicate.lifetime.hir_id)
2306 Self::lifetimes_outliving_lifetime(
2312 predicate.in_where_clause,
2318 hir::WherePredicate::BoundPredicate(predicate) => {
2319 // FIXME we can also infer bounds on associated types,
2320 // and should check for them here.
2321 match predicate.bounded_ty.kind {
2322 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => {
2323 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2326 let index = ty_generics.param_def_id_to_index[&def_id];
2328 Self::lifetimes_outliving_type(inferred_outlives, index),
2331 predicate.origin == PredicateOrigin::WhereClause,
2341 if relevant_lifetimes.is_empty() {
2345 let bound_spans = self.collect_outlives_bound_spans(
2348 &relevant_lifetimes,
2351 bound_count += bound_spans.len();
2353 let drop_predicate = bound_spans.len() == bounds.len();
2355 dropped_predicate_count += 1;
2358 if drop_predicate && !in_where_clause {
2359 lint_spans.push(predicate_span);
2360 } else if drop_predicate && i + 1 < num_predicates {
2361 // If all the bounds on a predicate were inferable and there are
2362 // further predicates, we want to eat the trailing comma.
2363 let next_predicate_span = hir_generics.predicates[i + 1].span();
2364 where_lint_spans.push(predicate_span.to(next_predicate_span.shrink_to_lo()));
2366 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2367 predicate_span.shrink_to_lo(),
2374 // If all predicates are inferable, drop the entire clause
2375 // (including the `where`)
2376 if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2378 let where_span = hir_generics.where_clause_span;
2379 // Extend the where clause back to the closing `>` of the
2380 // generics, except for tuple struct, which have the `where`
2381 // after the fields of the struct.
2382 let full_where_span =
2383 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2386 hir_generics.span.shrink_to_hi().to(where_span)
2389 // Due to macro expansions, the `full_where_span` might not actually contain all predicates.
2390 if where_lint_spans.iter().all(|&sp| full_where_span.contains(sp)) {
2391 lint_spans.push(full_where_span);
2393 lint_spans.extend(where_lint_spans);
2396 lint_spans.extend(where_lint_spans);
2399 if !lint_spans.is_empty() {
2400 // Do not automatically delete outlives requirements from macros.
2401 let applicability = if lint_spans.iter().all(|sp| sp.can_be_used_for_suggestions())
2403 Applicability::MachineApplicable
2405 Applicability::MaybeIncorrect
2408 cx.struct_span_lint(
2409 EXPLICIT_OUTLIVES_REQUIREMENTS,
2411 fluent::lint_builtin_explicit_outlives,
2413 lint.set_arg("count", bound_count).multipart_suggestion(
2415 lint_spans.into_iter().map(|span| (span, String::new())).collect(),
2426 /// The `incomplete_features` lint detects unstable features enabled with
2427 /// the [`feature` attribute] that may function improperly in some or all
2430 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2435 /// #![feature(generic_const_exprs)]
2442 /// Although it is encouraged for people to experiment with unstable
2443 /// features, some of them are known to be incomplete or faulty. This lint
2444 /// is a signal that the feature has not yet been finished, and you may
2445 /// experience problems with it.
2446 pub INCOMPLETE_FEATURES,
2448 "incomplete features that may function improperly in some or all cases"
2452 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2453 IncompleteFeatures => [INCOMPLETE_FEATURES]
2456 impl EarlyLintPass for IncompleteFeatures {
2457 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2458 let features = cx.sess().features_untracked();
2460 .declared_lang_features
2462 .map(|(name, span, _)| (name, span))
2463 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2464 .filter(|(&name, _)| features.incomplete(name))
2465 .for_each(|(&name, &span)| {
2466 cx.struct_span_lint(
2467 INCOMPLETE_FEATURES,
2469 fluent::lint_builtin_incomplete_features,
2471 lint.set_arg("name", name);
2473 rustc_feature::find_feature_issue(name, GateIssue::Language)
2475 lint.set_arg("n", n);
2476 lint.note(fluent::note);
2478 if HAS_MIN_FEATURES.contains(&name) {
2479 lint.help(fluent::help);
2488 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2491 /// The `invalid_value` lint detects creating a value that is not valid,
2492 /// such as a null reference.
2497 /// # #![allow(unused)]
2499 /// let x: &'static i32 = std::mem::zeroed();
2507 /// In some situations the compiler can detect that the code is creating
2508 /// an invalid value, which should be avoided.
2510 /// In particular, this lint will check for improper use of
2511 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2512 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2513 /// lint should provide extra information to indicate what the problem is
2514 /// and a possible solution.
2516 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2517 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2518 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2519 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2520 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2523 "an invalid value is being created (such as a null reference)"
2526 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2528 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2529 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2530 #[derive(Debug, Copy, Clone, PartialEq)]
2536 /// Information about why a type cannot be initialized this way.
2539 /// Spans from struct fields and similar that can be obtained from just the type.
2541 /// Used to report a trace through adts.
2542 nested: Option<Box<InitError>>,
2545 fn spanned(self, span: Span) -> InitError {
2546 Self { span: Some(span), ..self }
2549 fn nested(self, nested: impl Into<Option<InitError>>) -> InitError {
2550 assert!(self.nested.is_none());
2551 Self { nested: nested.into().map(Box::new), ..self }
2555 impl<'a> From<&'a str> for InitError {
2556 fn from(s: &'a str) -> Self {
2560 impl From<String> for InitError {
2561 fn from(message: String) -> Self {
2562 Self { message, span: None, nested: None }
2566 /// Test if this constant is all-0.
2567 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2568 use hir::ExprKind::*;
2569 use rustc_ast::LitKind::*;
2572 if let Int(i, _) = lit.node {
2578 Tup(tup) => tup.iter().all(is_zero),
2583 /// Determine if this expression is a "dangerous initialization".
2584 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2585 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2586 // Find calls to `mem::{uninitialized,zeroed}` methods.
2587 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2588 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2589 match cx.tcx.get_diagnostic_name(def_id) {
2590 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2591 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2592 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2596 } else if let hir::ExprKind::MethodCall(_, receiver, ..) = expr.kind {
2597 // Find problematic calls to `MaybeUninit::assume_init`.
2598 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2599 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2600 // This is a call to *some* method named `assume_init`.
2601 // See if the `self` parameter is one of the dangerous constructors.
2602 if let hir::ExprKind::Call(ref path_expr, _) = receiver.kind {
2603 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2604 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2605 match cx.tcx.get_diagnostic_name(def_id) {
2606 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2607 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2618 fn variant_find_init_error<'tcx>(
2619 cx: &LateContext<'tcx>,
2621 variant: &VariantDef,
2622 substs: ty::SubstsRef<'tcx>,
2625 ) -> Option<InitError> {
2626 let mut field_err = variant.fields.iter().find_map(|field| {
2627 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|mut err| {
2628 if !field.did.is_local() {
2630 } else if err.span.is_none() {
2631 err.span = Some(cx.tcx.def_span(field.did));
2632 write!(&mut err.message, " (in this {descr})").unwrap();
2635 InitError::from(format!("in this {descr}"))
2636 .spanned(cx.tcx.def_span(field.did))
2642 // Check if this ADT has a constrained layout (like `NonNull` and friends).
2643 if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty)) {
2644 if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &layout.abi {
2645 let range = scalar.valid_range(cx);
2646 let msg = if !range.contains(0) {
2648 } else if init == InitKind::Uninit && !scalar.is_always_valid(cx) {
2649 // Prefer reporting on the fields over the entire struct for uninit,
2650 // as the information bubbles out and it may be unclear why the type can't
2651 // be null from just its outside signature.
2653 "must be initialized inside its custom valid range"
2657 if let Some(field_err) = &mut field_err {
2658 // Most of the time, if the field error is the same as the struct error,
2659 // the struct error only happens because of the field error.
2660 if field_err.message.contains(msg) {
2661 field_err.message = format!("because {}", field_err.message);
2664 return Some(InitError::from(format!("`{ty}` {msg}")).nested(field_err));
2670 /// Return `Some` only if we are sure this type does *not*
2671 /// allow zero initialization.
2672 fn ty_find_init_error<'tcx>(
2673 cx: &LateContext<'tcx>,
2676 ) -> Option<InitError> {
2677 use rustc_type_ir::sty::TyKind::*;
2679 // Primitive types that don't like 0 as a value.
2680 Ref(..) => Some("references must be non-null".into()),
2681 Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),
2682 FnPtr(..) => Some("function pointers must be non-null".into()),
2683 Never => Some("the `!` type has no valid value".into()),
2684 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2685 // raw ptr to dyn Trait
2687 Some("the vtable of a wide raw pointer must be non-null".into())
2689 // Primitive types with other constraints.
2690 Bool if init == InitKind::Uninit => {
2691 Some("booleans must be either `true` or `false`".into())
2693 Char if init == InitKind::Uninit => {
2694 Some("characters must be a valid Unicode codepoint".into())
2696 Int(_) | Uint(_) if init == InitKind::Uninit => {
2697 Some("integers must be initialized".into())
2699 Float(_) if init == InitKind::Uninit => Some("floats must be initialized".into()),
2700 RawPtr(_) if init == InitKind::Uninit => {
2701 Some("raw pointers must be initialized".into())
2703 // Recurse and checks for some compound types. (but not unions)
2704 Adt(adt_def, substs) if !adt_def.is_union() => {
2706 if adt_def.is_struct() {
2707 return variant_find_init_error(
2710 adt_def.non_enum_variant(),
2717 let span = cx.tcx.def_span(adt_def.did());
2718 let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
2719 let definitely_inhabited = match variant
2720 .inhabited_predicate(cx.tcx, *adt_def)
2721 .subst(cx.tcx, substs)
2722 .apply_any_module(cx.tcx, cx.param_env)
2724 // Entirely skip uninhbaited variants.
2725 Some(false) => return None,
2726 // Forward the others, but remember which ones are definitely inhabited.
2730 Some((variant, definitely_inhabited))
2732 let Some(first_variant) = potential_variants.next() else {
2733 return Some(InitError::from("enums with no inhabited variants have no valid value").spanned(span));
2735 // So we have at least one potentially inhabited variant. Might we have two?
2736 let Some(second_variant) = potential_variants.next() else {
2737 // There is only one potentially inhabited variant. So we can recursively check that variant!
2738 return variant_find_init_error(
2743 "field of the only potentially inhabited enum variant",
2747 // So we have at least two potentially inhabited variants.
2748 // If we can prove that we have at least two *definitely* inhabited variants,
2749 // then we have a tag and hence leaving this uninit is definitely disallowed.
2750 // (Leaving it zeroed could be okay, depending on which variant is encoded as zero tag.)
2751 if init == InitKind::Uninit {
2752 let definitely_inhabited = (first_variant.1 as usize)
2753 + (second_variant.1 as usize)
2754 + potential_variants
2755 .filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
2757 if definitely_inhabited > 1 {
2758 return Some(InitError::from(
2759 "enums with multiple inhabited variants have to be initialized to a variant",
2763 // We couldn't find anything wrong here.
2767 // Proceed recursively, check all fields.
2768 ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2771 if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2772 // Array length known at array non-empty -- recurse.
2773 ty_find_init_error(cx, *ty, init)
2775 // Empty array or size unknown.
2779 // Conservative fallback.
2784 if let Some(init) = is_dangerous_init(cx, expr) {
2785 // This conjures an instance of a type out of nothing,
2786 // using zeroed or uninitialized memory.
2787 // We are extremely conservative with what we warn about.
2788 let conjured_ty = cx.typeck_results().expr_ty(expr);
2789 if let Some(mut err) = with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2791 // FIXME(davidtwco): make translatable
2792 cx.struct_span_lint(
2797 "the type `{}` does not permit {}",
2800 InitKind::Zeroed => "zero-initialization",
2801 InitKind::Uninit => "being left uninitialized",
2808 "this code causes undefined behavior when executed",
2812 "help: use `MaybeUninit<T>` instead, \
2813 and only call `assume_init` after initialization is done",
2816 if let Some(span) = err.span {
2817 lint.span_note(span, &err.message);
2819 lint.note(&err.message);
2821 if let Some(e) = err.nested {
2836 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2837 /// has been declared with the same name but different types.
2857 /// Because two symbols of the same name cannot be resolved to two
2858 /// different functions at link time, and one function cannot possibly
2859 /// have two types, a clashing extern declaration is almost certainly a
2860 /// mistake. Check to make sure that the `extern` definitions are correct
2861 /// and equivalent, and possibly consider unifying them in one location.
2863 /// This lint does not run between crates because a project may have
2864 /// dependencies which both rely on the same extern function, but declare
2865 /// it in a different (but valid) way. For example, they may both declare
2866 /// an opaque type for one or more of the arguments (which would end up
2867 /// distinct types), or use types that are valid conversions in the
2868 /// language the `extern fn` is defined in. In these cases, the compiler
2869 /// can't say that the clashing declaration is incorrect.
2870 pub CLASHING_EXTERN_DECLARATIONS,
2872 "detects when an extern fn has been declared with the same name but different types"
2875 pub struct ClashingExternDeclarations {
2876 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2877 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2878 /// the symbol should be reported as a clashing declaration.
2879 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2880 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2881 seen_decls: FxHashMap<Symbol, HirId>,
2884 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2885 /// just from declaration itself. This is important because we don't want to report clashes on
2886 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2889 /// The name of the symbol + the span of the annotation which introduced the link name.
2891 /// No link name, so just the name of the symbol.
2896 fn get_name(&self) -> Symbol {
2898 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2903 impl ClashingExternDeclarations {
2904 pub(crate) fn new() -> Self {
2905 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2907 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2908 /// for the item, return its HirId without updating the set.
2909 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2910 let did = fi.owner_id.to_def_id();
2911 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2912 let name = Symbol::intern(tcx.symbol_name(instance).name);
2913 if let Some(&hir_id) = self.seen_decls.get(&name) {
2914 // Avoid updating the map with the new entry when we do find a collision. We want to
2915 // make sure we're always pointing to the first definition as the previous declaration.
2916 // This lets us avoid emitting "knock-on" diagnostics.
2919 self.seen_decls.insert(name, fi.hir_id())
2923 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2924 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2926 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2927 if let Some((overridden_link_name, overridden_link_name_span)) =
2928 tcx.codegen_fn_attrs(fi.owner_id).link_name.map(|overridden_link_name| {
2929 // FIXME: Instead of searching through the attributes again to get span
2930 // information, we could have codegen_fn_attrs also give span information back for
2931 // where the attribute was defined. However, until this is found to be a
2932 // bottleneck, this does just fine.
2934 overridden_link_name,
2935 tcx.get_attr(fi.owner_id.to_def_id(), sym::link_name).unwrap().span,
2939 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2941 SymbolName::Normal(fi.ident.name)
2945 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2946 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2947 /// with the same members (as the declarations shouldn't clash).
2948 fn structurally_same_type<'tcx>(
2949 cx: &LateContext<'tcx>,
2954 fn structurally_same_type_impl<'tcx>(
2955 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2956 cx: &LateContext<'tcx>,
2961 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2964 // Given a transparent newtype, reach through and grab the inner
2965 // type unless the newtype makes the type non-null.
2966 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2969 if let ty::Adt(def, substs) = *ty.kind() {
2970 let is_transparent = def.repr().transparent();
2971 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2973 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2974 ty, is_transparent, is_non_null
2976 if is_transparent && !is_non_null {
2977 debug_assert!(def.variants().len() == 1);
2978 let v = &def.variant(VariantIdx::new(0));
2979 ty = transparent_newtype_field(tcx, v)
2981 "single-variant transparent structure with zero-sized field",
2987 debug!("non_transparent_ty -> {:?}", ty);
2992 let a = non_transparent_ty(a);
2993 let b = non_transparent_ty(b);
2995 if !seen_types.insert((a, b)) {
2996 // We've encountered a cycle. There's no point going any further -- the types are
2997 // structurally the same.
3002 // All nominally-same types are structurally same, too.
3005 // Do a full, depth-first comparison between the two.
3006 use rustc_type_ir::sty::TyKind::*;
3007 let a_kind = a.kind();
3008 let b_kind = b.kind();
3010 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
3011 debug!("compare_layouts({:?}, {:?})", a, b);
3012 let a_layout = &cx.layout_of(a)?.layout.abi();
3013 let b_layout = &cx.layout_of(b)?.layout.abi();
3015 "comparing layouts: {:?} == {:?} = {}",
3018 a_layout == b_layout
3020 Ok(a_layout == b_layout)
3023 #[allow(rustc::usage_of_ty_tykind)]
3024 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
3025 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
3028 ensure_sufficient_stack(|| {
3029 match (a_kind, b_kind) {
3030 (Adt(a_def, _), Adt(b_def, _)) => {
3031 // We can immediately rule out these types as structurally same if
3032 // their layouts differ.
3033 match compare_layouts(a, b) {
3034 Ok(false) => return false,
3035 _ => (), // otherwise, continue onto the full, fields comparison
3038 // Grab a flattened representation of all fields.
3039 let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
3040 let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
3042 // Perform a structural comparison for each field.
3045 |&ty::FieldDef { did: a_did, .. },
3046 &ty::FieldDef { did: b_did, .. }| {
3047 structurally_same_type_impl(
3057 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
3058 // For arrays, we also check the constness of the type.
3059 a_const.kind() == b_const.kind()
3060 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
3062 (Slice(a_ty), Slice(b_ty)) => {
3063 structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
3065 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
3066 a_tymut.mutbl == b_tymut.mutbl
3067 && structurally_same_type_impl(
3068 seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
3071 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
3072 // For structural sameness, we don't need the region to be same.
3074 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
3076 (FnDef(..), FnDef(..)) => {
3077 let a_poly_sig = a.fn_sig(tcx);
3078 let b_poly_sig = b.fn_sig(tcx);
3080 // We don't compare regions, but leaving bound regions around ICEs, so
3082 let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
3083 let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
3085 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
3086 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
3087 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
3088 structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
3090 && structurally_same_type_impl(
3098 (Tuple(a_substs), Tuple(b_substs)) => {
3099 a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
3100 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
3103 // For these, it's not quite as easy to define structural-sameness quite so easily.
3104 // For the purposes of this lint, take the conservative approach and mark them as
3105 // not structurally same.
3106 (Dynamic(..), Dynamic(..))
3107 | (Error(..), Error(..))
3108 | (Closure(..), Closure(..))
3109 | (Generator(..), Generator(..))
3110 | (GeneratorWitness(..), GeneratorWitness(..))
3111 | (Alias(ty::Projection, ..), Alias(ty::Projection, ..))
3112 | (Alias(ty::Opaque, ..), Alias(ty::Opaque, ..)) => false,
3114 // These definitely should have been caught above.
3115 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
3117 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
3118 // enum layout optimisation is being applied.
3119 (Adt(..), other_kind) | (other_kind, Adt(..))
3120 if is_primitive_or_pointer(other_kind) =>
3122 let (primitive, adt) =
3123 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
3124 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
3127 compare_layouts(a, b).unwrap_or(false)
3130 // Otherwise, just compare the layouts. This may fail to lint for some
3131 // incompatible types, but at the very least, will stop reads into
3132 // uninitialised memory.
3133 _ => compare_layouts(a, b).unwrap_or(false),
3138 let mut seen_types = FxHashSet::default();
3139 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
3143 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
3145 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
3146 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
3147 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
3148 if let ForeignItemKind::Fn(..) = this_fi.kind {
3150 if let Some(existing_hid) = self.insert(tcx, this_fi) {
3151 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
3152 let this_decl_ty = tcx.type_of(this_fi.owner_id);
3154 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
3155 existing_hid, existing_decl_ty, this_fi.owner_id, this_decl_ty
3157 // Check that the declarations match.
3158 if !Self::structurally_same_type(
3162 CItemKind::Declaration,
3164 let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
3165 let orig = Self::name_of_extern_decl(tcx, orig_fi);
3167 // We want to ensure that we use spans for both decls that include where the
3168 // name was defined, whether that was from the link_name attribute or not.
3169 let get_relevant_span =
3170 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
3171 SymbolName::Normal(_) => fi.span,
3172 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
3174 // Finally, emit the diagnostic.
3176 let msg = if orig.get_name() == this_fi.ident.name {
3177 fluent::lint_builtin_clashing_extern_same_name
3179 fluent::lint_builtin_clashing_extern_diff_name
3181 tcx.struct_span_lint_hir(
3182 CLASHING_EXTERN_DECLARATIONS,
3184 get_relevant_span(this_fi),
3187 let mut expected_str = DiagnosticStyledString::new();
3188 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
3189 let mut found_str = DiagnosticStyledString::new();
3190 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3192 lint.set_arg("this_fi", this_fi.ident.name)
3193 .set_arg("orig", orig.get_name())
3194 .span_label(get_relevant_span(orig_fi), fluent::previous_decl_label)
3195 .span_label(get_relevant_span(this_fi), fluent::mismatch_label)
3196 // FIXME(davidtwco): translatable expected/found
3197 .note_expected_found(&"", expected_str, &"", found_str)
3207 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3208 /// which causes [undefined behavior].
3213 /// # #![allow(unused)]
3216 /// let x = &*ptr::null::<i32>();
3217 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3218 /// let x = *(0 as *const i32);
3226 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3227 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3229 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3232 "detects when an null pointer is dereferenced"
3235 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3237 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3238 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3239 /// test if expression is a null ptr
3240 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3242 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3243 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3244 return is_zero(expr) || is_null_ptr(cx, expr);
3247 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3248 rustc_hir::ExprKind::Call(ref path, _) => {
3249 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3250 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3252 cx.tcx.get_diagnostic_name(def_id),
3253 Some(sym::ptr_null | sym::ptr_null_mut)
3263 /// test if expression is the literal `0`
3264 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3266 rustc_hir::ExprKind::Lit(ref lit) => {
3267 if let LitKind::Int(a, _) = lit.node {
3276 if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3277 if is_null_ptr(cx, expr_deref) {
3278 cx.struct_span_lint(
3281 fluent::lint_builtin_deref_nullptr,
3282 |lint| lint.span_label(expr.span, fluent::label),
3290 /// The `named_asm_labels` lint detects the use of named labels in the
3291 /// inline `asm!` macro.
3295 /// ```rust,compile_fail
3296 /// # #![feature(asm_experimental_arch)]
3297 /// use std::arch::asm;
3301 /// asm!("foo: bar");
3310 /// LLVM is allowed to duplicate inline assembly blocks for any
3311 /// reason, for example when it is in a function that gets inlined. Because
3312 /// of this, GNU assembler [local labels] *must* be used instead of labels
3313 /// with a name. Using named labels might cause assembler or linker errors.
3315 /// See the explanation in [Rust By Example] for more details.
3317 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3318 /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3319 pub NAMED_ASM_LABELS,
3321 "named labels in inline assembly",
3324 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3326 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3327 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3329 kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3333 for (template_sym, template_snippet, template_span) in template_strs.iter() {
3334 let template_str = template_sym.as_str();
3335 let find_label_span = |needle: &str| -> Option<Span> {
3336 if let Some(template_snippet) = template_snippet {
3337 let snippet = template_snippet.as_str();
3338 if let Some(pos) = snippet.find(needle) {
3342 .unwrap_or(snippet[pos..].len() - 1);
3343 let inner = InnerSpan::new(pos, end);
3344 return Some(template_span.from_inner(inner));
3351 let mut found_labels = Vec::new();
3353 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3354 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3355 for statement in statements {
3356 // If there's a comment, trim it from the statement
3357 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3358 let mut start_idx = 0;
3359 for (idx, _) in statement.match_indices(':') {
3360 let possible_label = statement[start_idx..idx].trim();
3361 let mut chars = possible_label.chars();
3362 let Some(c) = chars.next() else {
3363 // Empty string means a leading ':' in this section, which is not a label
3366 // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3367 if (c.is_alphabetic() || matches!(c, '.' | '_'))
3368 && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3370 found_labels.push(possible_label);
3372 // If we encounter a non-label, there cannot be any further labels, so stop checking
3376 start_idx = idx + 1;
3380 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3382 if found_labels.len() > 0 {
3383 let spans = found_labels
3385 .filter_map(|label| find_label_span(label))
3386 .collect::<Vec<Span>>();
3387 // If there were labels but we couldn't find a span, combine the warnings and use the template span
3388 let target_spans: MultiSpan =
3389 if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3391 cx.lookup_with_diagnostics(
3394 fluent::lint_builtin_asm_labels,
3396 BuiltinLintDiagnostics::NamedAsmLabel(
3397 "only local labels of the form `<number>:` should be used in inline asm"
3408 /// The `special_module_name` lint detects module
3409 /// declarations for files that have a special meaning.
3413 /// ```rust,compile_fail
3425 /// Cargo recognizes `lib.rs` and `main.rs` as the root of a
3426 /// library or binary crate, so declaring them as modules
3427 /// will lead to miscompilation of the crate unless configured
3430 /// To access a library from a binary target within the same crate,
3431 /// use `your_crate_name::` as the path instead of `lib::`:
3433 /// ```rust,compile_fail
3434 /// // bar/src/lib.rs
3439 /// // bar/src/main.rs
3445 /// Binary targets cannot be used as libraries and so declaring
3446 /// one as a module is not allowed.
3447 pub SPECIAL_MODULE_NAME,
3449 "module declarations for files with a special meaning",
3452 declare_lint_pass!(SpecialModuleName => [SPECIAL_MODULE_NAME]);
3454 impl EarlyLintPass for SpecialModuleName {
3455 fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
3456 for item in &krate.items {
3457 if let ast::ItemKind::Mod(
3459 ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _),
3462 if item.attrs.iter().any(|a| a.has_name(sym::path)) {
3466 match item.ident.name.as_str() {
3467 "lib" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for lib.rs", |lint| {
3469 .note("lib.rs is the root of this crate's library target")
3470 .help("to refer to it from other targets, use the library's name as the path")
3472 "main" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for main.rs", |lint| {
3474 .note("a binary crate cannot be used as library")
3483 pub use rustc_session::lint::builtin::UNEXPECTED_CFGS;
3485 declare_lint_pass!(UnexpectedCfgs => [UNEXPECTED_CFGS]);
3487 impl EarlyLintPass for UnexpectedCfgs {
3488 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
3489 let cfg = &cx.sess().parse_sess.config;
3490 let check_cfg = &cx.sess().parse_sess.check_config;
3491 for &(name, value) in cfg {
3492 if let Some(names_valid) = &check_cfg.names_valid {
3493 if !names_valid.contains(&name) {
3497 fluent::lint_builtin_unexpected_cli_config_name,
3498 |diag| diag.help(fluent::help).set_arg("name", name),
3502 if let Some(value) = value {
3503 if let Some(values) = &check_cfg.values_valid.get(&name) {
3504 if !values.contains(&value) {
3508 fluent::lint_builtin_unexpected_cli_config_value,
3510 diag.help(fluent::help)
3511 .set_arg("name", name)
3512 .set_arg("value", value)