1 //! Lints in the Rust compiler.
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main compiler.
7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
8 //! Then add code to emit the new lint in the appropriate circumstances.
9 //! You can do that in an existing `LintPass` if it makes sense, or in a
10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
11 //! compiler. Only do the latter if the check can't be written cleanly as a
12 //! `LintPass` (also, note that such lints will need to be defined in
13 //! `rustc_session::lint::builtin`, not here).
15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
18 //! with a `pub fn new()`.
20 //! If you define a new `LateLintPass`, you will also need to add it to the
21 //! `late_lint_methods!` invocation in `lib.rs`.
24 types::{transparent_newtype_field, CItemKind},
25 EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
28 use rustc_ast::tokenstream::{TokenStream, TokenTree};
29 use rustc_ast::visit::{FnCtxt, FnKind};
30 use rustc_ast::{self as ast, *};
31 use rustc_ast_pretty::pprust::{self, expr_to_string};
32 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
33 use rustc_data_structures::stack::ensure_sufficient_stack;
34 use rustc_errors::{Applicability, Diagnostic, DiagnosticStyledString, MultiSpan};
35 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
37 use rustc_hir::def::{DefKind, Res};
38 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
39 use rustc_hir::{ForeignItemKind, GenericParamKind, HirId, PatKind, PredicateOrigin};
40 use rustc_index::vec::Idx;
41 use rustc_middle::lint::{in_external_macro, LintDiagnosticBuilder};
42 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
43 use rustc_middle::ty::print::with_no_trimmed_paths;
44 use rustc_middle::ty::subst::GenericArgKind;
45 use rustc_middle::ty::Instance;
46 use rustc_middle::ty::{self, Ty, TyCtxt};
47 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
48 use rustc_span::edition::Edition;
49 use rustc_span::source_map::Spanned;
50 use rustc_span::symbol::{kw, sym, Ident, Symbol};
51 use rustc_span::{BytePos, InnerSpan, Span};
52 use rustc_target::abi::VariantIdx;
53 use rustc_trait_selection::traits::{self, misc::can_type_implement_copy};
55 use crate::nonstandard_style::{method_context, MethodLateContext};
58 use tracing::{debug, trace};
60 // hardwired lints from librustc_middle
61 pub use rustc_session::lint::builtin::*;
64 /// The `while_true` lint detects `while true { }`.
78 /// `while true` should be replaced with `loop`. A `loop` expression is
79 /// the preferred way to write an infinite loop because it more directly
80 /// expresses the intent of the loop.
83 "suggest using `loop { }` instead of `while true { }`"
86 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
88 /// Traverse through any amount of parenthesis and return the first non-parens expression.
89 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
90 while let ast::ExprKind::Paren(sub) = &expr.kind {
96 impl EarlyLintPass for WhileTrue {
97 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
98 if let ast::ExprKind::While(cond, _, label) = &e.kind {
99 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
100 if let ast::LitKind::Bool(true) = lit.kind {
101 if !lit.span.from_expansion() {
102 let msg = "denote infinite loops with `loop { ... }`";
103 let condition_span = e.span.with_hi(cond.span.hi());
104 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
106 .span_suggestion_short(
111 label.map_or_else(String::new, |label| format!(
116 Applicability::MachineApplicable,
128 /// The `box_pointers` lints use of the Box type.
132 /// ```rust,compile_fail
133 /// #![deny(box_pointers)]
143 /// This lint is mostly historical, and not particularly useful. `Box<T>`
144 /// used to be built into the language, and the only way to do heap
145 /// allocation. Today's Rust can call into other allocators, etc.
148 "use of owned (Box type) heap memory"
151 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
154 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
155 for leaf in ty.walk() {
156 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
157 if leaf_ty.is_box() {
158 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
159 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit();
167 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
168 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
170 hir::ItemKind::Fn(..)
171 | hir::ItemKind::TyAlias(..)
172 | hir::ItemKind::Enum(..)
173 | hir::ItemKind::Struct(..)
174 | hir::ItemKind::Union(..) => {
175 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
180 // If it's a struct, we also have to check the fields' types
182 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
183 for struct_field in struct_def.fields() {
184 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
185 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
192 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
193 let ty = cx.typeck_results().node_type(e.hir_id);
194 self.check_heap_type(cx, e.span, ty);
199 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
200 /// instead of `Struct { x }` in a pattern.
218 /// Point { x: x, y: y } => (),
227 /// The preferred style is to avoid the repetition of specifying both the
228 /// field name and the binding name if both identifiers are the same.
229 NON_SHORTHAND_FIELD_PATTERNS,
231 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
234 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
236 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
237 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
238 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
243 .expect("struct pattern type is not an ADT")
244 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
245 for fieldpat in field_pats {
246 if fieldpat.is_shorthand {
249 if fieldpat.span.from_expansion() {
250 // Don't lint if this is a macro expansion: macro authors
251 // shouldn't have to worry about this kind of style issue
255 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
256 if cx.tcx.find_field_index(ident, &variant)
257 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
259 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
261 .build(&format!("the `{}:` in this pattern is redundant", ident));
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 ident = if let Some(binding) = binding {
269 format!("{} {}", binding, ident)
275 "use shorthand field pattern",
277 Applicability::MachineApplicable,
289 /// The `unsafe_code` lint catches usage of `unsafe` code.
293 /// ```rust,compile_fail
294 /// #![deny(unsafe_code)]
306 /// This lint is intended to restrict the usage of `unsafe`, which can be
307 /// difficult to use correctly.
310 "usage of `unsafe` code"
313 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
318 cx: &EarlyContext<'_>,
320 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
322 // This comes from a macro that has `#[allow_internal_unsafe]`.
323 if span.allows_unsafe() {
327 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
330 fn report_overridden_symbol_name(&self, cx: &EarlyContext<'_>, span: Span, msg: &str) {
331 self.report_unsafe(cx, span, |lint| {
334 "the linker's behavior with multiple libraries exporting duplicate symbol \
335 names is undefined and Rust cannot provide guarantees when you manually \
342 fn report_overridden_symbol_section(&self, cx: &EarlyContext<'_>, span: Span, msg: &str) {
343 self.report_unsafe(cx, span, |lint| {
346 "the program's behavior with overridden link sections on items is unpredictable \
347 and Rust cannot provide guarantees when you manually override them",
354 impl EarlyLintPass for UnsafeCode {
355 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
356 if attr.has_name(sym::allow_internal_unsafe) {
357 self.report_unsafe(cx, attr.span, |lint| {
359 "`allow_internal_unsafe` allows defining \
360 macros using unsafe without triggering \
361 the `unsafe_code` lint at their call site",
368 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
369 if let ast::ExprKind::Block(ref blk, _) = e.kind {
370 // Don't warn about generated blocks; that'll just pollute the output.
371 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
372 self.report_unsafe(cx, blk.span, |lint| {
373 lint.build("usage of an `unsafe` block").emit();
379 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
381 ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => self
382 .report_unsafe(cx, it.span, |lint| {
383 lint.build("declaration of an `unsafe` trait").emit();
386 ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => self
387 .report_unsafe(cx, it.span, |lint| {
388 lint.build("implementation of an `unsafe` trait").emit();
391 ast::ItemKind::Fn(..) => {
392 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
393 self.report_overridden_symbol_name(
396 "declaration of a `no_mangle` function",
400 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
401 self.report_overridden_symbol_name(
404 "declaration of a function with `export_name`",
408 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
409 self.report_overridden_symbol_section(
412 "declaration of a function with `link_section`",
417 ast::ItemKind::Static(..) => {
418 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
419 self.report_overridden_symbol_name(
422 "declaration of a `no_mangle` static",
426 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
427 self.report_overridden_symbol_name(
430 "declaration of a static with `export_name`",
434 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
435 self.report_overridden_symbol_section(
438 "declaration of a static with `link_section`",
447 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
448 if let ast::AssocItemKind::Fn(..) = it.kind {
449 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
450 self.report_overridden_symbol_name(
453 "declaration of a `no_mangle` method",
456 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
457 self.report_overridden_symbol_name(
460 "declaration of a method with `export_name`",
466 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
470 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
476 let msg = match ctxt {
477 FnCtxt::Foreign => return,
478 FnCtxt::Free => "declaration of an `unsafe` function",
479 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
480 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
482 self.report_unsafe(cx, span, |lint| {
483 lint.build(msg).emit();
490 /// The `missing_docs` lint detects missing documentation for public items.
494 /// ```rust,compile_fail
495 /// #![deny(missing_docs)]
503 /// This lint is intended to ensure that a library is well-documented.
504 /// Items without documentation can be difficult for users to understand
505 /// how to use properly.
507 /// This lint is "allow" by default because it can be noisy, and not all
508 /// projects may want to enforce everything to be documented.
511 "detects missing documentation for public members",
512 report_in_external_macro
515 pub struct MissingDoc {
516 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
517 doc_hidden_stack: Vec<bool>,
520 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
522 fn has_doc(attr: &ast::Attribute) -> bool {
523 if attr.is_doc_comment() {
527 if !attr.has_name(sym::doc) {
531 if attr.value_str().is_some() {
535 if let Some(list) = attr.meta_item_list() {
537 if meta.has_name(sym::hidden) {
547 pub fn new() -> MissingDoc {
548 MissingDoc { doc_hidden_stack: vec![false] }
551 fn doc_hidden(&self) -> bool {
552 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
555 fn check_missing_docs_attrs(
557 cx: &LateContext<'_>,
560 article: &'static str,
563 // If we're building a test harness, then warning about
564 // documentation is probably not really relevant right now.
565 if cx.sess().opts.test {
569 // `#[doc(hidden)]` disables missing_docs check.
570 if self.doc_hidden() {
574 // Only check publicly-visible items, using the result from the privacy pass.
575 // It's an option so the crate root can also use this function (it doesn't
577 if def_id != CRATE_DEF_ID {
578 if !cx.access_levels.is_exported(def_id) {
583 let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
584 let has_doc = attrs.iter().any(has_doc);
588 cx.tcx.sess.source_map().guess_head_span(sp),
590 lint.build(&format!("missing documentation for {} {}", article, desc)).emit();
597 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
598 fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
599 let doc_hidden = self.doc_hidden()
600 || attrs.iter().any(|attr| {
601 attr.has_name(sym::doc)
602 && match attr.meta_item_list() {
604 Some(l) => attr::list_contains_name(&l, sym::hidden),
607 self.doc_hidden_stack.push(doc_hidden);
610 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
611 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
614 fn check_crate(&mut self, cx: &LateContext<'_>) {
615 self.check_missing_docs_attrs(
618 cx.tcx.def_span(CRATE_DEF_ID),
624 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
626 hir::ItemKind::Trait(..) => {
627 // Issue #11592: traits are always considered exported, even when private.
628 if cx.tcx.visibility(it.def_id)
629 == ty::Visibility::Restricted(
630 cx.tcx.parent_module_from_def_id(it.def_id).to_def_id(),
636 hir::ItemKind::TyAlias(..)
637 | hir::ItemKind::Fn(..)
638 | hir::ItemKind::Macro(..)
639 | hir::ItemKind::Mod(..)
640 | hir::ItemKind::Enum(..)
641 | hir::ItemKind::Struct(..)
642 | hir::ItemKind::Union(..)
643 | hir::ItemKind::Const(..)
644 | hir::ItemKind::Static(..) => {}
649 let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
651 self.check_missing_docs_attrs(cx, it.def_id, it.span, article, desc);
654 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
655 let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
657 self.check_missing_docs_attrs(cx, trait_item.def_id, trait_item.span, article, desc);
660 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
661 // If the method is an impl for a trait, don't doc.
662 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
666 // If the method is an impl for an item with docs_hidden, don't doc.
667 if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
668 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
669 let impl_ty = cx.tcx.type_of(parent);
670 let outerdef = match impl_ty.kind() {
671 ty::Adt(def, _) => Some(def.did()),
672 ty::Foreign(def_id) => Some(*def_id),
675 let is_hidden = match outerdef {
676 Some(id) => cx.tcx.is_doc_hidden(id),
684 let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
685 self.check_missing_docs_attrs(cx, impl_item.def_id, impl_item.span, article, desc);
688 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
689 let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
690 self.check_missing_docs_attrs(cx, foreign_item.def_id, foreign_item.span, article, desc);
693 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
694 if !sf.is_positional() {
695 let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
696 self.check_missing_docs_attrs(cx, def_id, sf.span, "a", "struct field")
700 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
701 self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), v.span, "a", "variant");
706 /// The `missing_copy_implementations` lint detects potentially-forgotten
707 /// implementations of [`Copy`].
709 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
713 /// ```rust,compile_fail
714 /// #![deny(missing_copy_implementations)]
725 /// Historically (before 1.0), types were automatically marked as `Copy`
726 /// if possible. This was changed so that it required an explicit opt-in
727 /// by implementing the `Copy` trait. As part of this change, a lint was
728 /// added to alert if a copyable type was not marked `Copy`.
730 /// This lint is "allow" by default because this code isn't bad; it is
731 /// common to write newtypes like this specifically so that a `Copy` type
732 /// is no longer `Copy`. `Copy` types can result in unintended copies of
733 /// large data which can impact performance.
734 pub MISSING_COPY_IMPLEMENTATIONS,
736 "detects potentially-forgotten implementations of `Copy`"
739 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
741 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
742 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
743 if !cx.access_levels.is_reachable(item.def_id) {
746 let (def, ty) = match item.kind {
747 hir::ItemKind::Struct(_, ref ast_generics) => {
748 if !ast_generics.params.is_empty() {
751 let def = cx.tcx.adt_def(item.def_id);
752 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
754 hir::ItemKind::Union(_, ref ast_generics) => {
755 if !ast_generics.params.is_empty() {
758 let def = cx.tcx.adt_def(item.def_id);
759 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
761 hir::ItemKind::Enum(_, ref ast_generics) => {
762 if !ast_generics.params.is_empty() {
765 let def = cx.tcx.adt_def(item.def_id);
766 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
770 if def.has_dtor(cx.tcx) {
773 let param_env = ty::ParamEnv::empty();
774 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
777 if can_type_implement_copy(
781 traits::ObligationCause::misc(item.span, item.hir_id()),
785 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
787 "type could implement `Copy`; consider adding `impl \
797 /// The `missing_debug_implementations` lint detects missing
798 /// implementations of [`fmt::Debug`].
800 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
804 /// ```rust,compile_fail
805 /// #![deny(missing_debug_implementations)]
814 /// Having a `Debug` implementation on all types can assist with
815 /// debugging, as it provides a convenient way to format and display a
816 /// value. Using the `#[derive(Debug)]` attribute will automatically
817 /// generate a typical implementation, or a custom implementation can be
818 /// added by manually implementing the `Debug` trait.
820 /// This lint is "allow" by default because adding `Debug` to all types can
821 /// have a negative impact on compile time and code size. It also requires
822 /// boilerplate to be added to every type, which can be an impediment.
823 MISSING_DEBUG_IMPLEMENTATIONS,
825 "detects missing implementations of Debug"
829 pub struct MissingDebugImplementations {
830 impling_types: Option<LocalDefIdSet>,
833 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
835 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
836 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
837 if !cx.access_levels.is_reachable(item.def_id) {
842 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
846 let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
850 if self.impling_types.is_none() {
851 let mut impls = LocalDefIdSet::default();
852 cx.tcx.for_each_impl(debug, |d| {
853 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
854 if let Some(def_id) = ty_def.did().as_local() {
855 impls.insert(def_id);
860 self.impling_types = Some(impls);
861 debug!("{:?}", self.impling_types);
864 if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
865 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
867 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
868 or a manual implementation",
869 cx.tcx.def_path_str(debug)
878 /// The `anonymous_parameters` lint detects anonymous parameters in trait
883 /// ```rust,edition2015,compile_fail
884 /// #![deny(anonymous_parameters)]
896 /// This syntax is mostly a historical accident, and can be worked around
897 /// quite easily by adding an `_` pattern or a descriptive identifier:
901 /// fn foo(_: usize);
905 /// This syntax is now a hard error in the 2018 edition. In the 2015
906 /// edition, this lint is "warn" by default. This lint
907 /// enables the [`cargo fix`] tool with the `--edition` flag to
908 /// automatically transition old code from the 2015 edition to 2018. The
909 /// tool will run this lint and automatically apply the
910 /// suggested fix from the compiler (which is to add `_` to each
911 /// parameter). This provides a completely automated way to update old
912 /// code for a new edition. See [issue #41686] for more details.
914 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
915 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
916 pub ANONYMOUS_PARAMETERS,
918 "detects anonymous parameters",
919 @future_incompatible = FutureIncompatibleInfo {
920 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
921 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
926 /// Checks for use of anonymous parameters (RFC 1685).
927 AnonymousParameters => [ANONYMOUS_PARAMETERS]
930 impl EarlyLintPass for AnonymousParameters {
931 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
932 if cx.sess().edition() != Edition::Edition2015 {
933 // This is a hard error in future editions; avoid linting and erroring
936 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
937 for arg in sig.decl.inputs.iter() {
938 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
939 if ident.name == kw::Empty {
940 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
941 let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
943 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
944 (snip.as_str(), Applicability::MachineApplicable)
946 ("<type>", Applicability::HasPlaceholders)
950 "anonymous parameters are deprecated and will be \
951 removed in the next edition",
955 "try naming the parameter or explicitly \
957 format!("_: {}", ty_snip),
969 /// Check for use of attributes which have been deprecated.
971 pub struct DeprecatedAttr {
972 // This is not free to compute, so we want to keep it around, rather than
973 // compute it for every attribute.
974 depr_attrs: Vec<&'static BuiltinAttribute>,
977 impl_lint_pass!(DeprecatedAttr => []);
979 impl DeprecatedAttr {
980 pub fn new() -> DeprecatedAttr {
981 DeprecatedAttr { depr_attrs: deprecated_attributes() }
985 fn lint_deprecated_attr(
986 cx: &EarlyContext<'_>,
987 attr: &ast::Attribute,
989 suggestion: Option<&str>,
991 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
993 .span_suggestion_short(
995 suggestion.unwrap_or("remove this attribute"),
997 Applicability::MachineApplicable,
1003 impl EarlyLintPass for DeprecatedAttr {
1004 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
1005 for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
1006 if attr.ident().map(|ident| ident.name) == Some(*name) {
1007 if let &AttributeGate::Gated(
1008 Stability::Deprecated(link, suggestion),
1015 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
1016 lint_deprecated_attr(cx, attr, &msg, suggestion);
1021 if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
1022 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
1023 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
1024 lint_deprecated_attr(cx, attr, &msg, None);
1029 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1030 use rustc_ast::token::CommentKind;
1032 let mut attrs = attrs.iter().peekable();
1034 // Accumulate a single span for sugared doc comments.
1035 let mut sugared_span: Option<Span> = None;
1037 while let Some(attr) = attrs.next() {
1038 let is_doc_comment = attr.is_doc_comment();
1041 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1044 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1048 let span = sugared_span.take().unwrap_or(attr.span);
1050 if is_doc_comment || attr.has_name(sym::doc) {
1051 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1052 let mut err = lint.build("unused doc comment");
1055 format!("rustdoc does not generate documentation for {}", node_kind),
1058 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1059 err.help("use `//` for a plain comment");
1061 AttrKind::DocComment(CommentKind::Block, _) => {
1062 err.help("use `/* */` for a plain comment");
1071 impl EarlyLintPass for UnusedDocComment {
1072 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1073 let kind = match stmt.kind {
1074 ast::StmtKind::Local(..) => "statements",
1075 // Disabled pending discussion in #78306
1076 ast::StmtKind::Item(..) => return,
1077 // expressions will be reported by `check_expr`.
1078 ast::StmtKind::Empty
1079 | ast::StmtKind::Semi(_)
1080 | ast::StmtKind::Expr(_)
1081 | ast::StmtKind::MacCall(_) => return,
1084 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1087 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1088 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1089 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1092 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1093 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1096 fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1097 warn_if_doc(cx, param.ident.span, "generic parameters", ¶m.attrs);
1100 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1101 warn_if_doc(cx, block.span, "block", &block.attrs());
1104 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1105 if let ast::ItemKind::ForeignMod(_) = item.kind {
1106 warn_if_doc(cx, item.span, "extern block", &item.attrs);
1112 /// The `no_mangle_const_items` lint detects any `const` items with the
1113 /// [`no_mangle` attribute].
1115 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1119 /// ```rust,compile_fail
1121 /// const FOO: i32 = 5;
1128 /// Constants do not have their symbols exported, and therefore, this
1129 /// probably means you meant to use a [`static`], not a [`const`].
1131 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1132 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1133 NO_MANGLE_CONST_ITEMS,
1135 "const items will not have their symbols exported"
1139 /// The `no_mangle_generic_items` lint detects generic items that must be
1146 /// fn foo<T>(t: T) {
1155 /// A function with generics must have its symbol mangled to accommodate
1156 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1157 /// this situation, and should be removed.
1159 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1160 NO_MANGLE_GENERIC_ITEMS,
1162 "generic items must be mangled"
1165 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1167 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1168 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1169 let attrs = cx.tcx.hir().attrs(it.hir_id());
1170 let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1171 impl_generics: Option<&hir::Generics<'_>>,
1172 generics: &hir::Generics<'_>,
1175 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1178 GenericParamKind::Lifetime { .. } => {}
1179 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1180 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
1181 lint.build("functions generic over types or consts must be mangled")
1182 .span_suggestion_short(
1183 no_mangle_attr.span,
1184 "remove this attribute",
1186 // Use of `#[no_mangle]` suggests FFI intent; correct
1187 // fix may be to monomorphize source by hand
1188 Applicability::MaybeIncorrect,
1198 hir::ItemKind::Fn(.., ref generics, _) => {
1199 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1200 check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1203 hir::ItemKind::Const(..) => {
1204 if cx.sess().contains_name(attrs, sym::no_mangle) {
1205 // Const items do not refer to a particular location in memory, and therefore
1206 // don't have anything to attach a symbol to
1207 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1208 let msg = "const items should never be `#[no_mangle]`";
1209 let mut err = lint.build(msg);
1211 // account for "pub const" (#45562)
1216 .span_to_snippet(it.span)
1217 .map(|snippet| snippet.find("const").unwrap_or(0))
1218 .unwrap_or(0) as u32;
1219 // `const` is 5 chars
1220 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1221 err.span_suggestion(
1223 "try a static value",
1224 "pub static".to_owned(),
1225 Applicability::MachineApplicable,
1231 hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1233 if let hir::AssocItemKind::Fn { .. } = it.kind {
1234 if let Some(no_mangle_attr) = cx
1236 .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1238 check_no_mangle_on_generic_fn(
1241 cx.tcx.hir().get_generics(it.id.def_id).unwrap(),
1254 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1255 /// T` because it is [undefined behavior].
1257 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1261 /// ```rust,compile_fail
1263 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1271 /// Certain assumptions are made about aliasing of data, and this transmute
1272 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1274 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1277 "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1280 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1282 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1283 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1284 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1285 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1287 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1288 let msg = "transmuting &T to &mut T is undefined behavior, \
1289 even if the reference is unused, consider instead using an UnsafeCell";
1290 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
1291 lint.build(msg).emit();
1296 fn get_transmute_from_to<'tcx>(
1297 cx: &LateContext<'tcx>,
1298 expr: &hir::Expr<'_>,
1299 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1300 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1301 cx.qpath_res(qpath, expr.hir_id)
1305 if let Res::Def(DefKind::Fn, did) = def {
1306 if !def_id_is_transmute(cx, did) {
1309 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1310 let from = sig.inputs().skip_binder()[0];
1311 let to = sig.output().skip_binder();
1312 return Some((from, to));
1317 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1318 cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1324 /// The `unstable_features` is deprecated and should no longer be used.
1327 "enabling unstable features (deprecated. do not use)"
1331 /// Forbids using the `#[feature(...)]` attribute
1332 UnstableFeatures => [UNSTABLE_FEATURES]
1335 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1336 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1337 if attr.has_name(sym::feature) {
1338 if let Some(items) = attr.meta_item_list() {
1340 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1341 lint.build("unstable feature").emit();
1350 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1355 /// ```rust,compile_fail
1356 /// #![deny(unreachable_pub)]
1368 /// A bare `pub` visibility may be misleading if the item is not actually
1369 /// publicly exported from the crate. The `pub(crate)` visibility is
1370 /// recommended to be used instead, which more clearly expresses the intent
1371 /// that the item is only visible within its own crate.
1373 /// This lint is "allow" by default because it will trigger for a large
1374 /// amount existing Rust code, and has some false-positives. Eventually it
1375 /// is desired for this to become warn-by-default.
1376 pub UNREACHABLE_PUB,
1378 "`pub` items not reachable from crate root"
1382 /// Lint for items marked `pub` that aren't reachable from other crates.
1383 UnreachablePub => [UNREACHABLE_PUB]
1386 impl UnreachablePub {
1389 cx: &LateContext<'_>,
1396 let mut applicability = Applicability::MachineApplicable;
1397 if cx.tcx.visibility(def_id).is_public() && !cx.access_levels.is_reachable(def_id) {
1398 if vis_span.from_expansion() {
1399 applicability = Applicability::MaybeIncorrect;
1401 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1402 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1403 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1405 err.span_suggestion(
1407 "consider restricting its visibility",
1408 "pub(crate)".to_owned(),
1412 err.help("or consider exporting it for use by other crates");
1420 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1421 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1422 // Do not warn for fake `use` statements.
1423 if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1426 self.perform_lint(cx, "item", item.def_id, item.span, item.vis_span, true);
1429 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1433 foreign_item.def_id,
1435 foreign_item.vis_span,
1440 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1441 let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1442 self.perform_lint(cx, "field", def_id, field.span, field.vis_span, false);
1445 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1446 // Only lint inherent impl items.
1447 if cx.tcx.associated_item(impl_item.def_id).trait_item_def_id.is_none() {
1461 /// The `type_alias_bounds` lint detects bounds in type aliases.
1466 /// type SendVec<T: Send> = Vec<T>;
1473 /// The trait bounds in a type alias are currently ignored, and should not
1474 /// be included to avoid confusion. This was previously allowed
1475 /// unintentionally; this may become a hard error in the future.
1478 "bounds in type aliases are not enforced"
1482 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1483 /// They are relevant when using associated types, but otherwise neither checked
1484 /// at definition site nor enforced at use site.
1485 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1488 impl TypeAliasBounds {
1489 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1491 hir::QPath::TypeRelative(ref ty, _) => {
1492 // If this is a type variable, we found a `T::Assoc`.
1494 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1495 matches!(path.res, Res::Def(DefKind::TyParam, _))
1500 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1504 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1505 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1506 // bound. Let's see if this type does that.
1508 // We use a HIR visitor to walk the type.
1509 use rustc_hir::intravisit::{self, Visitor};
1510 struct WalkAssocTypes<'a> {
1511 err: &'a mut Diagnostic,
1513 impl Visitor<'_> for WalkAssocTypes<'_> {
1514 fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1515 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1518 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1519 associated types in type aliases",
1522 intravisit::walk_qpath(self, qpath, id, span)
1526 // Let's go for a walk!
1527 let mut visitor = WalkAssocTypes { err };
1528 visitor.visit_ty(ty);
1532 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1533 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1534 let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1537 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1538 // Bounds are respected for `type X = impl Trait`
1541 // There must not be a where clause
1542 if type_alias_generics.predicates.is_empty() {
1546 let mut where_spans = Vec::new();
1547 let mut inline_spans = Vec::new();
1548 let mut inline_sugg = Vec::new();
1549 for p in type_alias_generics.predicates {
1550 let span = p.span();
1551 if p.in_where_clause() {
1552 where_spans.push(span);
1554 for b in p.bounds() {
1555 inline_spans.push(b.span());
1557 inline_sugg.push((span, String::new()));
1561 let mut suggested_changing_assoc_types = false;
1562 if !where_spans.is_empty() {
1563 cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1564 let mut err = lint.build("where clauses are not enforced in type aliases");
1565 err.set_span(where_spans);
1566 err.span_suggestion(
1567 type_alias_generics.where_clause_span,
1568 "the clause will not be checked when the type alias is used, and should be removed",
1570 Applicability::MachineApplicable,
1572 if !suggested_changing_assoc_types {
1573 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1574 suggested_changing_assoc_types = true;
1580 if !inline_spans.is_empty() {
1581 cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
1583 lint.build("bounds on generic parameters are not enforced in type aliases");
1584 err.set_span(inline_spans);
1585 err.multipart_suggestion(
1586 "the bound will not be checked when the type alias is used, and should be removed",
1588 Applicability::MachineApplicable,
1590 if !suggested_changing_assoc_types {
1591 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1600 /// Lint constants that are erroneous.
1601 /// Without this lint, we might not get any diagnostic if the constant is
1602 /// unused within this crate, even though downstream crates can't use it
1603 /// without producing an error.
1604 UnusedBrokenConst => []
1607 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1608 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1610 hir::ItemKind::Const(_, body_id) => {
1611 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1612 // trigger the query once for all constants since that will already report the errors
1613 // FIXME: Use ensure here
1614 let _ = cx.tcx.const_eval_poly(def_id);
1616 hir::ItemKind::Static(_, _, body_id) => {
1617 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1618 // FIXME: Use ensure here
1619 let _ = cx.tcx.eval_static_initializer(def_id);
1627 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1628 /// any type parameters.
1633 /// #![feature(trivial_bounds)]
1634 /// pub struct A where i32: Copy;
1641 /// Usually you would not write a trait bound that you know is always
1642 /// true, or never true. However, when using macros, the macro may not
1643 /// know whether or not the constraint would hold or not at the time when
1644 /// generating the code. Currently, the compiler does not alert you if the
1645 /// constraint is always true, and generates an error if it is never true.
1646 /// The `trivial_bounds` feature changes this to be a warning in both
1647 /// cases, giving macros more freedom and flexibility to generate code,
1648 /// while still providing a signal when writing non-macro code that
1649 /// something is amiss.
1651 /// See [RFC 2056] for more details. This feature is currently only
1652 /// available on the nightly channel, see [tracking issue #48214].
1654 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1655 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1658 "these bounds don't depend on an type parameters"
1662 /// Lint for trait and lifetime bounds that don't depend on type parameters
1663 /// which either do nothing, or stop the item from being used.
1664 TrivialConstraints => [TRIVIAL_BOUNDS]
1667 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1668 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1669 use rustc_middle::ty::fold::TypeFoldable;
1670 use rustc_middle::ty::PredicateKind::*;
1672 if cx.tcx.features().trivial_bounds {
1673 let predicates = cx.tcx.predicates_of(item.def_id);
1674 for &(predicate, span) in predicates.predicates {
1675 let predicate_kind_name = match predicate.kind().skip_binder() {
1676 Trait(..) => "trait",
1678 RegionOutlives(..) => "lifetime",
1680 // Ignore projections, as they can only be global
1681 // if the trait bound is global
1683 // Ignore bounds that a user can't type
1689 ConstEvaluatable(..) |
1691 TypeWellFormedFromEnv(..) => continue,
1693 if predicate.is_global() {
1694 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1695 lint.build(&format!(
1696 "{} bound {} does not depend on any type \
1697 or lifetime parameters",
1698 predicate_kind_name, predicate
1709 /// Does nothing as a lint pass, but registers some `Lint`s
1710 /// which are used by other parts of the compiler.
1714 NON_SHORTHAND_FIELD_PATTERNS,
1717 MISSING_COPY_IMPLEMENTATIONS,
1718 MISSING_DEBUG_IMPLEMENTATIONS,
1719 ANONYMOUS_PARAMETERS,
1720 UNUSED_DOC_COMMENTS,
1721 NO_MANGLE_CONST_ITEMS,
1722 NO_MANGLE_GENERIC_ITEMS,
1732 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1733 /// pattern], which is deprecated.
1735 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1739 /// ```rust,edition2018
1751 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1752 /// confusion with the [`..` range expression]. Use the new form instead.
1754 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1755 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1757 "`...` range patterns are deprecated",
1758 @future_incompatible = FutureIncompatibleInfo {
1759 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1760 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1765 pub struct EllipsisInclusiveRangePatterns {
1766 /// If `Some(_)`, suppress all subsequent pattern
1767 /// warnings for better diagnostics.
1768 node_id: Option<ast::NodeId>,
1771 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1773 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1774 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1775 if self.node_id.is_some() {
1776 // Don't recursively warn about patterns inside range endpoints.
1780 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1782 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1783 /// corresponding to the ellipsis.
1784 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1789 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1790 ) => Some((a.as_deref(), b, *span)),
1795 let (parenthesise, endpoints) = match &pat.kind {
1796 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1797 _ => (false, matches_ellipsis_pat(pat)),
1800 if let Some((start, end, join)) = endpoints {
1801 let msg = "`...` range patterns are deprecated";
1802 let suggestion = "use `..=` for an inclusive range";
1804 self.node_id = Some(pat.id);
1805 let end = expr_to_string(&end);
1806 let replace = match start {
1807 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1808 None => format!("&(..={})", end),
1810 if join.edition() >= Edition::Edition2021 {
1812 rustc_errors::struct_span_err!(cx.sess(), pat.span, E0783, "{}", msg,);
1813 err.span_suggestion(
1817 Applicability::MachineApplicable,
1821 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1827 Applicability::MachineApplicable,
1833 let replace = "..=".to_owned();
1834 if join.edition() >= Edition::Edition2021 {
1836 rustc_errors::struct_span_err!(cx.sess(), pat.span, E0783, "{}", msg,);
1837 err.span_suggestion_short(
1841 Applicability::MachineApplicable,
1845 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1847 .span_suggestion_short(
1851 Applicability::MachineApplicable,
1860 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1861 if let Some(node_id) = self.node_id {
1862 if pat.id == node_id {
1870 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1871 /// that are not able to be run by the test harness because they are in a
1872 /// position where they are not nameable.
1874 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1882 /// // This test will not fail because it does not run.
1883 /// assert_eq!(1, 2);
1892 /// In order for the test harness to run a test, the test function must be
1893 /// located in a position where it can be accessed from the crate root.
1894 /// This generally means it must be defined in a module, and not anywhere
1895 /// else such as inside another function. The compiler previously allowed
1896 /// this without an error, so a lint was added as an alert that a test is
1897 /// not being used. Whether or not this should be allowed has not yet been
1898 /// decided, see [RFC 2471] and [issue #36629].
1900 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1901 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1902 UNNAMEABLE_TEST_ITEMS,
1904 "detects an item that cannot be named being marked as `#[test_case]`",
1905 report_in_external_macro
1908 pub struct UnnameableTestItems {
1909 boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1910 items_nameable: bool,
1913 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1915 impl UnnameableTestItems {
1916 pub fn new() -> Self {
1917 Self { boundary: None, items_nameable: true }
1921 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1922 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1923 if self.items_nameable {
1924 if let hir::ItemKind::Mod(..) = it.kind {
1926 self.items_nameable = false;
1927 self.boundary = Some(it.def_id);
1932 let attrs = cx.tcx.hir().attrs(it.hir_id());
1933 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1934 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1935 lint.build("cannot test inner items").emit();
1940 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1941 if !self.items_nameable && self.boundary == Some(it.def_id) {
1942 self.items_nameable = true;
1948 /// The `keyword_idents` lint detects edition keywords being used as an
1953 /// ```rust,edition2015,compile_fail
1954 /// #![deny(keyword_idents)]
1963 /// Rust [editions] allow the language to evolve without breaking
1964 /// backwards compatibility. This lint catches code that uses new keywords
1965 /// that are added to the language that are used as identifiers (such as a
1966 /// variable name, function name, etc.). If you switch the compiler to a
1967 /// new edition without updating the code, then it will fail to compile if
1968 /// you are using a new keyword as an identifier.
1970 /// You can manually change the identifiers to a non-keyword, or use a
1971 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1973 /// This lint solves the problem automatically. It is "allow" by default
1974 /// because the code is perfectly valid in older editions. The [`cargo
1975 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1976 /// and automatically apply the suggested fix from the compiler (which is
1977 /// to use a raw identifier). This provides a completely automated way to
1978 /// update old code for a new edition.
1980 /// [editions]: https://doc.rust-lang.org/edition-guide/
1981 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1982 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1985 "detects edition keywords being used as an identifier",
1986 @future_incompatible = FutureIncompatibleInfo {
1987 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1988 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1993 /// Check for uses of edition keywords used as an identifier.
1994 KeywordIdents => [KEYWORD_IDENTS]
1997 struct UnderMacro(bool);
1999 impl KeywordIdents {
2000 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
2001 for tt in tokens.into_trees() {
2003 // Only report non-raw idents.
2004 TokenTree::Token(token) => {
2005 if let Some((ident, false)) = token.ident() {
2006 self.check_ident_token(cx, UnderMacro(true), ident);
2009 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
2014 fn check_ident_token(
2016 cx: &EarlyContext<'_>,
2017 UnderMacro(under_macro): UnderMacro,
2020 let next_edition = match cx.sess().edition() {
2021 Edition::Edition2015 => {
2023 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
2025 // rust-lang/rust#56327: Conservatively do not
2026 // attempt to report occurrences of `dyn` within
2027 // macro definitions or invocations, because `dyn`
2028 // can legitimately occur as a contextual keyword
2029 // in 2015 code denoting its 2018 meaning, and we
2030 // do not want rustfix to inject bugs into working
2031 // code by rewriting such occurrences.
2033 // But if we see `dyn` outside of a macro, we know
2034 // its precise role in the parsed AST and thus are
2035 // assured this is truly an attempt to use it as
2037 kw::Dyn if !under_macro => Edition::Edition2018,
2043 // There are no new keywords yet for the 2018 edition and beyond.
2047 // Don't lint `r#foo`.
2048 if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2052 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2053 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
2056 "you can use a raw identifier to stay compatible",
2057 format!("r#{}", ident),
2058 Applicability::MachineApplicable,
2065 impl EarlyLintPass for KeywordIdents {
2066 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2067 self.check_tokens(cx, mac_def.body.inner_tokens());
2069 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2070 self.check_tokens(cx, mac.args.inner_tokens());
2072 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2073 self.check_ident_token(cx, UnderMacro(false), ident);
2077 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2079 impl ExplicitOutlivesRequirements {
2080 fn lifetimes_outliving_lifetime<'tcx>(
2081 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2083 ) -> Vec<ty::Region<'tcx>> {
2086 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2087 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
2088 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2096 fn lifetimes_outliving_type<'tcx>(
2097 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2099 ) -> Vec<ty::Region<'tcx>> {
2102 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2103 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2104 a.is_param(index).then_some(b)
2111 fn collect_outlives_bound_spans<'tcx>(
2114 bounds: &hir::GenericBounds<'_>,
2115 inferred_outlives: &[ty::Region<'tcx>],
2116 ) -> Vec<(usize, Span)> {
2117 use rustc_middle::middle::resolve_lifetime::Region;
2122 .filter_map(|(i, bound)| {
2123 if let hir::GenericBound::Outlives(lifetime) = bound {
2124 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2125 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2126 if let ty::ReEarlyBound(ebr) = **r { ebr.index == index } else { false }
2130 is_inferred.then_some((i, bound.span()))
2135 .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
2139 fn consolidate_outlives_bound_spans(
2142 bounds: &hir::GenericBounds<'_>,
2143 bound_spans: Vec<(usize, Span)>,
2145 if bounds.is_empty() {
2148 if bound_spans.len() == bounds.len() {
2149 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2150 // If all bounds are inferable, we want to delete the colon, so
2151 // start from just after the parameter (span passed as argument)
2152 vec![lo.to(last_bound_span)]
2154 let mut merged = Vec::new();
2155 let mut last_merged_i = None;
2157 let mut from_start = true;
2158 for (i, bound_span) in bound_spans {
2159 match last_merged_i {
2160 // If the first bound is inferable, our span should also eat the leading `+`.
2162 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2163 last_merged_i = Some(0);
2165 // If consecutive bounds are inferable, merge their spans
2166 Some(h) if i == h + 1 => {
2167 if let Some(tail) = merged.last_mut() {
2168 // Also eat the trailing `+` if the first
2169 // more-than-one bound is inferable
2170 let to_span = if from_start && i < bounds.len() {
2171 bounds[i + 1].span().shrink_to_lo()
2175 *tail = tail.to(to_span);
2176 last_merged_i = Some(i);
2178 bug!("another bound-span visited earlier");
2182 // When we find a non-inferable bound, subsequent inferable bounds
2183 // won't be consecutive from the start (and we'll eat the leading
2184 // `+` rather than the trailing one)
2186 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2187 last_merged_i = Some(i);
2196 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2197 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2198 use rustc_middle::middle::resolve_lifetime::Region;
2200 let def_id = item.def_id;
2201 if let hir::ItemKind::Struct(_, ref hir_generics)
2202 | hir::ItemKind::Enum(_, ref hir_generics)
2203 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2205 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2206 if inferred_outlives.is_empty() {
2210 let ty_generics = cx.tcx.generics_of(def_id);
2212 let mut bound_count = 0;
2213 let mut lint_spans = Vec::new();
2214 let mut where_lint_spans = Vec::new();
2215 let mut dropped_predicate_count = 0;
2216 let num_predicates = hir_generics.predicates.len();
2217 for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2218 let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
2219 hir::WherePredicate::RegionPredicate(predicate) => {
2220 if let Some(Region::EarlyBound(index, ..)) =
2221 cx.tcx.named_region(predicate.lifetime.hir_id)
2224 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2227 predicate.in_where_clause,
2233 hir::WherePredicate::BoundPredicate(predicate) => {
2234 // FIXME we can also infer bounds on associated types,
2235 // and should check for them here.
2236 match predicate.bounded_ty.kind {
2237 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2238 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2241 let index = ty_generics.param_def_id_to_index[&def_id];
2243 Self::lifetimes_outliving_type(inferred_outlives, index),
2246 predicate.origin == PredicateOrigin::WhereClause,
2256 if relevant_lifetimes.is_empty() {
2261 self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
2262 bound_count += bound_spans.len();
2264 let drop_predicate = bound_spans.len() == bounds.len();
2266 dropped_predicate_count += 1;
2269 if drop_predicate && !in_where_clause {
2270 lint_spans.push(span);
2271 } else if drop_predicate && i + 1 < num_predicates {
2272 // If all the bounds on a predicate were inferable and there are
2273 // further predicates, we want to eat the trailing comma.
2274 let next_predicate_span = hir_generics.predicates[i + 1].span();
2275 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2277 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2278 span.shrink_to_lo(),
2285 // If all predicates are inferable, drop the entire clause
2286 // (including the `where`)
2287 if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2289 let where_span = hir_generics.where_clause_span;
2290 // Extend the where clause back to the closing `>` of the
2291 // generics, except for tuple struct, which have the `where`
2292 // after the fields of the struct.
2293 let full_where_span =
2294 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2297 hir_generics.span.shrink_to_hi().to(where_span)
2299 lint_spans.push(full_where_span);
2301 lint_spans.extend(where_lint_spans);
2304 if !lint_spans.is_empty() {
2305 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2306 lint.build("outlives requirements can be inferred")
2307 .multipart_suggestion(
2308 if bound_count == 1 {
2311 "remove these bounds"
2315 .map(|span| (span, String::new()))
2316 .collect::<Vec<_>>(),
2317 Applicability::MachineApplicable,
2327 /// The `incomplete_features` lint detects unstable features enabled with
2328 /// the [`feature` attribute] that may function improperly in some or all
2331 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2336 /// #![feature(generic_const_exprs)]
2343 /// Although it is encouraged for people to experiment with unstable
2344 /// features, some of them are known to be incomplete or faulty. This lint
2345 /// is a signal that the feature has not yet been finished, and you may
2346 /// experience problems with it.
2347 pub INCOMPLETE_FEATURES,
2349 "incomplete features that may function improperly in some or all cases"
2353 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2354 IncompleteFeatures => [INCOMPLETE_FEATURES]
2357 impl EarlyLintPass for IncompleteFeatures {
2358 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2359 let features = cx.sess().features_untracked();
2361 .declared_lang_features
2363 .map(|(name, span, _)| (name, span))
2364 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2365 .filter(|(&name, _)| features.incomplete(name))
2366 .for_each(|(&name, &span)| {
2367 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2368 let mut builder = lint.build(&format!(
2369 "the feature `{}` is incomplete and may not be safe to use \
2370 and/or cause compiler crashes",
2373 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2374 builder.note(&format!(
2375 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
2376 for more information",
2380 if HAS_MIN_FEATURES.contains(&name) {
2381 builder.help(&format!(
2382 "consider using `min_{}` instead, which is more stable and complete",
2392 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2395 /// The `invalid_value` lint detects creating a value that is not valid,
2396 /// such as a null reference.
2401 /// # #![allow(unused)]
2403 /// let x: &'static i32 = std::mem::zeroed();
2411 /// In some situations the compiler can detect that the code is creating
2412 /// an invalid value, which should be avoided.
2414 /// In particular, this lint will check for improper use of
2415 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2416 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2417 /// lint should provide extra information to indicate what the problem is
2418 /// and a possible solution.
2420 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2421 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2422 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2423 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2424 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2427 "an invalid value is being created (such as a null reference)"
2430 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2432 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2433 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2434 #[derive(Debug, Copy, Clone, PartialEq)]
2440 /// Information about why a type cannot be initialized this way.
2441 /// Contains an error message and optionally a span to point at.
2442 type InitError = (String, Option<Span>);
2444 /// Test if this constant is all-0.
2445 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2446 use hir::ExprKind::*;
2447 use rustc_ast::LitKind::*;
2450 if let Int(i, _) = lit.node {
2456 Tup(tup) => tup.iter().all(is_zero),
2461 /// Determine if this expression is a "dangerous initialization".
2462 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2463 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2464 // Find calls to `mem::{uninitialized,zeroed}` methods.
2465 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2466 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2467 match cx.tcx.get_diagnostic_name(def_id) {
2468 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2469 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2470 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2474 } else if let hir::ExprKind::MethodCall(_, ref args, _) = expr.kind {
2475 // Find problematic calls to `MaybeUninit::assume_init`.
2476 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2477 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2478 // This is a call to *some* method named `assume_init`.
2479 // See if the `self` parameter is one of the dangerous constructors.
2480 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2481 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2482 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2483 match cx.tcx.get_diagnostic_name(def_id) {
2484 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2485 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2496 /// Test if this enum has several actually "existing" variants.
2497 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2498 fn is_multi_variant<'tcx>(adt: ty::AdtDef<'tcx>) -> bool {
2499 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2500 let existing_variants = adt.variants().iter().filter(|v| v.fields.is_empty()).count();
2501 existing_variants > 1
2504 /// Return `Some` only if we are sure this type does *not*
2505 /// allow zero initialization.
2506 fn ty_find_init_error<'tcx>(
2507 cx: &LateContext<'tcx>,
2510 ) -> Option<InitError> {
2511 use rustc_type_ir::sty::TyKind::*;
2513 // Primitive types that don't like 0 as a value.
2514 Ref(..) => Some(("references must be non-null".to_string(), None)),
2515 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2516 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2517 Never => Some(("the `!` type has no valid value".to_string(), None)),
2518 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2519 // raw ptr to dyn Trait
2521 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2523 // Primitive types with other constraints.
2524 Bool if init == InitKind::Uninit => {
2525 Some(("booleans must be either `true` or `false`".to_string(), None))
2527 Char if init == InitKind::Uninit => {
2528 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2530 // Recurse and checks for some compound types.
2531 Adt(adt_def, substs) if !adt_def.is_union() => {
2532 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2533 use std::ops::Bound;
2534 match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
2535 // We exploit here that `layout_scalar_valid_range` will never
2536 // return `Bound::Excluded`. (And we have tests checking that we
2537 // handle the attribute correctly.)
2538 (Bound::Included(lo), _) if lo > 0 => {
2539 return Some((format!("`{}` must be non-null", ty), None));
2541 (Bound::Included(_), _) | (_, Bound::Included(_))
2542 if init == InitKind::Uninit =>
2546 "`{}` must be initialized inside its custom valid range",
2555 match adt_def.variants().len() {
2556 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2558 // Struct, or enum with exactly one variant.
2559 // Proceed recursively, check all fields.
2560 let variant = &adt_def.variant(VariantIdx::from_u32(0));
2561 variant.fields.iter().find_map(|field| {
2562 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(
2565 // Point to this field, should be helpful for figuring
2566 // out where the source of the error is.
2567 let span = cx.tcx.def_span(field.did);
2570 " (in this {} field)",
2583 // Multi-variant enum.
2585 if init == InitKind::Uninit && is_multi_variant(*adt_def) {
2586 let span = cx.tcx.def_span(adt_def.did());
2588 "enums have to be initialized to a variant".to_string(),
2592 // In principle, for zero-initialization we could figure out which variant corresponds
2593 // to tag 0, and check that... but for now we just accept all zero-initializations.
2600 // Proceed recursively, check all fields.
2601 ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2604 if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2605 // Array length known at array non-empty -- recurse.
2606 ty_find_init_error(cx, *ty, init)
2608 // Empty array or size unknown.
2612 // Conservative fallback.
2617 if let Some(init) = is_dangerous_init(cx, expr) {
2618 // This conjures an instance of a type out of nothing,
2619 // using zeroed or uninitialized memory.
2620 // We are extremely conservative with what we warn about.
2621 let conjured_ty = cx.typeck_results().expr_ty(expr);
2622 if let Some((msg, span)) =
2623 with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2625 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2626 let mut err = lint.build(&format!(
2627 "the type `{}` does not permit {}",
2630 InitKind::Zeroed => "zero-initialization",
2631 InitKind::Uninit => "being left uninitialized",
2634 err.span_label(expr.span, "this code causes undefined behavior when executed");
2637 "help: use `MaybeUninit<T>` instead, \
2638 and only call `assume_init` after initialization is done",
2640 if let Some(span) = span {
2641 err.span_note(span, &msg);
2653 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2654 /// has been declared with the same name but different types.
2674 /// Because two symbols of the same name cannot be resolved to two
2675 /// different functions at link time, and one function cannot possibly
2676 /// have two types, a clashing extern declaration is almost certainly a
2677 /// mistake. Check to make sure that the `extern` definitions are correct
2678 /// and equivalent, and possibly consider unifying them in one location.
2680 /// This lint does not run between crates because a project may have
2681 /// dependencies which both rely on the same extern function, but declare
2682 /// it in a different (but valid) way. For example, they may both declare
2683 /// an opaque type for one or more of the arguments (which would end up
2684 /// distinct types), or use types that are valid conversions in the
2685 /// language the `extern fn` is defined in. In these cases, the compiler
2686 /// can't say that the clashing declaration is incorrect.
2687 pub CLASHING_EXTERN_DECLARATIONS,
2689 "detects when an extern fn has been declared with the same name but different types"
2692 pub struct ClashingExternDeclarations {
2693 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2694 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2695 /// the symbol should be reported as a clashing declaration.
2696 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2697 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2698 seen_decls: FxHashMap<Symbol, HirId>,
2701 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2702 /// just from declaration itself. This is important because we don't want to report clashes on
2703 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2706 /// The name of the symbol + the span of the annotation which introduced the link name.
2708 /// No link name, so just the name of the symbol.
2713 fn get_name(&self) -> Symbol {
2715 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2720 impl ClashingExternDeclarations {
2721 pub(crate) fn new() -> Self {
2722 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2724 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2725 /// for the item, return its HirId without updating the set.
2726 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2727 let did = fi.def_id.to_def_id();
2728 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2729 let name = Symbol::intern(tcx.symbol_name(instance).name);
2730 if let Some(&hir_id) = self.seen_decls.get(&name) {
2731 // Avoid updating the map with the new entry when we do find a collision. We want to
2732 // make sure we're always pointing to the first definition as the previous declaration.
2733 // This lets us avoid emitting "knock-on" diagnostics.
2736 self.seen_decls.insert(name, fi.hir_id())
2740 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2741 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2743 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2744 if let Some((overridden_link_name, overridden_link_name_span)) =
2745 tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2746 // FIXME: Instead of searching through the attributes again to get span
2747 // information, we could have codegen_fn_attrs also give span information back for
2748 // where the attribute was defined. However, until this is found to be a
2749 // bottleneck, this does just fine.
2751 overridden_link_name,
2752 tcx.get_attr(fi.def_id.to_def_id(), sym::link_name).unwrap().span,
2756 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2758 SymbolName::Normal(fi.ident.name)
2762 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2763 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2764 /// with the same members (as the declarations shouldn't clash).
2765 fn structurally_same_type<'tcx>(
2766 cx: &LateContext<'tcx>,
2771 fn structurally_same_type_impl<'tcx>(
2772 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2773 cx: &LateContext<'tcx>,
2778 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2781 // Given a transparent newtype, reach through and grab the inner
2782 // type unless the newtype makes the type non-null.
2783 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2786 if let ty::Adt(def, substs) = *ty.kind() {
2787 let is_transparent = def.repr().transparent();
2788 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2790 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2791 ty, is_transparent, is_non_null
2793 if is_transparent && !is_non_null {
2794 debug_assert!(def.variants().len() == 1);
2795 let v = &def.variant(VariantIdx::new(0));
2796 ty = transparent_newtype_field(tcx, v)
2798 "single-variant transparent structure with zero-sized field",
2804 debug!("non_transparent_ty -> {:?}", ty);
2809 let a = non_transparent_ty(a);
2810 let b = non_transparent_ty(b);
2812 if !seen_types.insert((a, b)) {
2813 // We've encountered a cycle. There's no point going any further -- the types are
2814 // structurally the same.
2819 // All nominally-same types are structurally same, too.
2822 // Do a full, depth-first comparison between the two.
2823 use rustc_type_ir::sty::TyKind::*;
2824 let a_kind = a.kind();
2825 let b_kind = b.kind();
2827 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2828 debug!("compare_layouts({:?}, {:?})", a, b);
2829 let a_layout = &cx.layout_of(a)?.layout.abi();
2830 let b_layout = &cx.layout_of(b)?.layout.abi();
2832 "comparing layouts: {:?} == {:?} = {}",
2835 a_layout == b_layout
2837 Ok(a_layout == b_layout)
2840 #[allow(rustc::usage_of_ty_tykind)]
2841 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2842 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2845 ensure_sufficient_stack(|| {
2846 match (a_kind, b_kind) {
2847 (Adt(a_def, _), Adt(b_def, _)) => {
2848 // We can immediately rule out these types as structurally same if
2849 // their layouts differ.
2850 match compare_layouts(a, b) {
2851 Ok(false) => return false,
2852 _ => (), // otherwise, continue onto the full, fields comparison
2855 // Grab a flattened representation of all fields.
2856 let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2857 let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2859 // Perform a structural comparison for each field.
2862 |&ty::FieldDef { did: a_did, .. },
2863 &ty::FieldDef { did: b_did, .. }| {
2864 structurally_same_type_impl(
2874 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2875 // For arrays, we also check the constness of the type.
2876 a_const.val() == b_const.val()
2877 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2879 (Slice(a_ty), Slice(b_ty)) => {
2880 structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2882 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2883 a_tymut.mutbl == b_tymut.mutbl
2884 && structurally_same_type_impl(
2885 seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2888 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2889 // For structural sameness, we don't need the region to be same.
2891 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2893 (FnDef(..), FnDef(..)) => {
2894 let a_poly_sig = a.fn_sig(tcx);
2895 let b_poly_sig = b.fn_sig(tcx);
2897 // As we don't compare regions, skip_binder is fine.
2898 let a_sig = a_poly_sig.skip_binder();
2899 let b_sig = b_poly_sig.skip_binder();
2901 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2902 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2903 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2904 structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2906 && structurally_same_type_impl(
2914 (Tuple(a_substs), Tuple(b_substs)) => {
2915 a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2916 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2919 // For these, it's not quite as easy to define structural-sameness quite so easily.
2920 // For the purposes of this lint, take the conservative approach and mark them as
2921 // not structurally same.
2922 (Dynamic(..), Dynamic(..))
2923 | (Error(..), Error(..))
2924 | (Closure(..), Closure(..))
2925 | (Generator(..), Generator(..))
2926 | (GeneratorWitness(..), GeneratorWitness(..))
2927 | (Projection(..), Projection(..))
2928 | (Opaque(..), Opaque(..)) => false,
2930 // These definitely should have been caught above.
2931 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2933 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2934 // enum layout optimisation is being applied.
2935 (Adt(..), other_kind) | (other_kind, Adt(..))
2936 if is_primitive_or_pointer(other_kind) =>
2938 let (primitive, adt) =
2939 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2940 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2943 compare_layouts(a, b).unwrap_or(false)
2946 // Otherwise, just compare the layouts. This may fail to lint for some
2947 // incompatible types, but at the very least, will stop reads into
2948 // uninitialised memory.
2949 _ => compare_layouts(a, b).unwrap_or(false),
2954 let mut seen_types = FxHashSet::default();
2955 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2959 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2961 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2962 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2963 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2964 if let ForeignItemKind::Fn(..) = this_fi.kind {
2966 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2967 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2968 let this_decl_ty = tcx.type_of(this_fi.def_id);
2970 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2971 existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2973 // Check that the declarations match.
2974 if !Self::structurally_same_type(
2978 CItemKind::Declaration,
2980 let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
2981 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2983 // We want to ensure that we use spans for both decls that include where the
2984 // name was defined, whether that was from the link_name attribute or not.
2985 let get_relevant_span =
2986 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2987 SymbolName::Normal(_) => fi.span,
2988 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2990 // Finally, emit the diagnostic.
2991 tcx.struct_span_lint_hir(
2992 CLASHING_EXTERN_DECLARATIONS,
2994 get_relevant_span(this_fi),
2996 let mut expected_str = DiagnosticStyledString::new();
2997 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2998 let mut found_str = DiagnosticStyledString::new();
2999 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3001 lint.build(&format!(
3002 "`{}` redeclare{} with a different signature",
3004 if orig.get_name() == this_fi.ident.name {
3007 format!("s `{}`", orig.get_name())
3011 get_relevant_span(orig_fi),
3012 &format!("`{}` previously declared here", orig.get_name()),
3015 get_relevant_span(this_fi),
3016 "this signature doesn't match the previous declaration",
3018 .note_expected_found(&"", expected_str, &"", found_str)
3029 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3030 /// which causes [undefined behavior].
3035 /// # #![allow(unused)]
3038 /// let x = &*ptr::null::<i32>();
3039 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3040 /// let x = *(0 as *const i32);
3048 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3049 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3051 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3054 "detects when an null pointer is dereferenced"
3057 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3059 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3060 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3061 /// test if expression is a null ptr
3062 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3064 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3065 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3066 return is_zero(expr) || is_null_ptr(cx, expr);
3069 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3070 rustc_hir::ExprKind::Call(ref path, _) => {
3071 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3072 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3074 cx.tcx.get_diagnostic_name(def_id),
3075 Some(sym::ptr_null | sym::ptr_null_mut)
3085 /// test if expression is the literal `0`
3086 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3088 rustc_hir::ExprKind::Lit(ref lit) => {
3089 if let LitKind::Int(a, _) = lit.node {
3098 if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3099 if is_null_ptr(cx, expr_deref) {
3100 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3101 let mut err = lint.build("dereferencing a null pointer");
3102 err.span_label(expr.span, "this code causes undefined behavior when executed");
3111 /// The `named_asm_labels` lint detects the use of named labels in the
3112 /// inline `asm!` macro.
3116 /// ```rust,compile_fail
3117 /// use std::arch::asm;
3121 /// asm!("foo: bar");
3130 /// LLVM is allowed to duplicate inline assembly blocks for any
3131 /// reason, for example when it is in a function that gets inlined. Because
3132 /// of this, GNU assembler [local labels] *must* be used instead of labels
3133 /// with a name. Using named labels might cause assembler or linker errors.
3135 /// See the explanation in [Rust By Example] for more details.
3137 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3138 /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3139 pub NAMED_ASM_LABELS,
3141 "named labels in inline assembly",
3144 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3146 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3147 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3149 kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3153 for (template_sym, template_snippet, template_span) in template_strs.iter() {
3154 let template_str = template_sym.as_str();
3155 let find_label_span = |needle: &str| -> Option<Span> {
3156 if let Some(template_snippet) = template_snippet {
3157 let snippet = template_snippet.as_str();
3158 if let Some(pos) = snippet.find(needle) {
3162 .unwrap_or(snippet[pos..].len() - 1);
3163 let inner = InnerSpan::new(pos, end);
3164 return Some(template_span.from_inner(inner));
3171 let mut found_labels = Vec::new();
3173 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3174 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3175 for statement in statements {
3176 // If there's a comment, trim it from the statement
3177 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3178 let mut start_idx = 0;
3179 for (idx, _) in statement.match_indices(':') {
3180 let possible_label = statement[start_idx..idx].trim();
3181 let mut chars = possible_label.chars();
3182 let Some(c) = chars.next() else {
3183 // Empty string means a leading ':' in this section, which is not a label
3186 // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3187 if (c.is_alphabetic() || matches!(c, '.' | '_'))
3188 && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3190 found_labels.push(possible_label);
3192 // If we encounter a non-label, there cannot be any further labels, so stop checking
3196 start_idx = idx + 1;
3200 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3202 if found_labels.len() > 0 {
3203 let spans = found_labels
3205 .filter_map(|label| find_label_span(label))
3206 .collect::<Vec<Span>>();
3207 // If there were labels but we couldn't find a span, combine the warnings and use the template span
3208 let target_spans: MultiSpan =
3209 if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3211 cx.lookup_with_diagnostics(
3216 diag.build("avoid using named labels in inline assembly");
3219 BuiltinLintDiagnostics::NamedAsmLabel(
3220 "only local labels of the form `<number>:` should be used in inline asm"