1 // ignore-tidy-filelength
3 //! Lints in the Rust compiler.
5 //! This contains lints which can feasibly be implemented as their own
6 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
7 //! definitions of lints that are emitted directly inside the main compiler.
9 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
10 //! Then add code to emit the new lint in the appropriate circumstances.
11 //! You can do that in an existing `LintPass` if it makes sense, or in a
12 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
13 //! compiler. Only do the latter if the check can't be written cleanly as a
14 //! `LintPass` (also, note that such lints will need to be defined in
15 //! `rustc_session::lint::builtin`, not here).
17 //! If you define a new `EarlyLintPass`, you will also need to add it to the
18 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
19 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
20 //! with a `pub fn new()`.
22 //! If you define a new `LateLintPass`, you will also need to add it to the
23 //! `late_lint_methods!` invocation in `lib.rs`.
26 types::{transparent_newtype_field, CItemKind},
27 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;
36 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
37 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
38 use rustc_feature::{GateIssue, Stability};
40 use rustc_hir::def::{DefKind, Res};
41 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet};
42 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
43 use rustc_hir::{HirId, Node};
44 use rustc_index::vec::Idx;
45 use rustc_middle::lint::LintDiagnosticBuilder;
46 use rustc_middle::ty::print::with_no_trimmed_paths;
47 use rustc_middle::ty::subst::{GenericArgKind, Subst};
48 use rustc_middle::ty::Instance;
49 use rustc_middle::ty::{self, layout::LayoutError, Ty, TyCtxt};
50 use rustc_session::lint::FutureIncompatibilityReason;
51 use rustc_session::Session;
52 use rustc_span::edition::Edition;
53 use rustc_span::source_map::Spanned;
54 use rustc_span::symbol::{kw, sym, Ident, Symbol};
55 use rustc_span::{BytePos, Span};
56 use rustc_target::abi::{LayoutOf, VariantIdx};
57 use rustc_trait_selection::traits::misc::can_type_implement_copy;
59 use crate::nonstandard_style::{method_context, MethodLateContext};
62 use tracing::{debug, trace};
64 // hardwired lints from librustc_middle
65 pub use rustc_session::lint::builtin::*;
68 /// The `while_true` lint detects `while true { }`.
82 /// `while true` should be replaced with `loop`. A `loop` expression is
83 /// the preferred way to write an infinite loop because it more directly
84 /// expresses the intent of the loop.
87 "suggest using `loop { }` instead of `while true { }`"
90 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
92 /// Traverse through any amount of parenthesis and return the first non-parens expression.
93 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
94 while let ast::ExprKind::Paren(sub) = &expr.kind {
100 impl EarlyLintPass for WhileTrue {
101 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
102 if let ast::ExprKind::While(cond, _, label) = &e.kind {
103 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
104 if let ast::LitKind::Bool(true) = lit.kind {
105 if !lit.span.from_expansion() {
106 let msg = "denote infinite loops with `loop { ... }`";
107 let condition_span = e.span.with_hi(cond.span.hi());
108 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
110 .span_suggestion_short(
115 label.map_or_else(String::new, |label| format!(
120 Applicability::MachineApplicable,
132 /// The `box_pointers` lints use of the Box type.
136 /// ```rust,compile_fail
137 /// #![deny(box_pointers)]
147 /// This lint is mostly historical, and not particularly useful. `Box<T>`
148 /// used to be built into the language, and the only way to do heap
149 /// allocation. Today's Rust can call into other allocators, etc.
152 "use of owned (Box type) heap memory"
155 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
158 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
159 for leaf in ty.walk() {
160 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
161 if leaf_ty.is_box() {
162 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
163 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
171 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
172 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
174 hir::ItemKind::Fn(..)
175 | hir::ItemKind::TyAlias(..)
176 | hir::ItemKind::Enum(..)
177 | hir::ItemKind::Struct(..)
178 | hir::ItemKind::Union(..) => {
179 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
184 // If it's a struct, we also have to check the fields' types
186 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
187 for struct_field in struct_def.fields() {
188 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
189 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
196 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
197 let ty = cx.typeck_results().node_type(e.hir_id);
198 self.check_heap_type(cx, e.span, ty);
203 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
204 /// instead of `Struct { x }` in a pattern.
222 /// Point { x: x, y: y } => (),
231 /// The preferred style is to avoid the repetition of specifying both the
232 /// field name and the binding name if both identifiers are the same.
233 NON_SHORTHAND_FIELD_PATTERNS,
235 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
238 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
240 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
241 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
242 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
247 .expect("struct pattern type is not an ADT")
248 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
249 for fieldpat in field_pats {
250 if fieldpat.is_shorthand {
253 if fieldpat.span.from_expansion() {
254 // Don't lint if this is a macro expansion: macro authors
255 // shouldn't have to worry about this kind of style issue
259 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
260 if cx.tcx.find_field_index(ident, &variant)
261 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
263 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
265 .build(&format!("the `{}:` in this pattern is redundant", ident));
266 let binding = match binding_annot {
267 hir::BindingAnnotation::Unannotated => None,
268 hir::BindingAnnotation::Mutable => Some("mut"),
269 hir::BindingAnnotation::Ref => Some("ref"),
270 hir::BindingAnnotation::RefMut => Some("ref mut"),
272 let ident = if let Some(binding) = binding {
273 format!("{} {}", binding, ident)
279 "use shorthand field pattern",
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 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
326 // This comes from a macro that has `#[allow_internal_unsafe]`.
327 if span.allows_unsafe() {
331 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
334 fn report_overriden_symbol_name(&self, cx: &EarlyContext<'_>, span: Span, msg: &str) {
335 self.report_unsafe(cx, span, |lint| {
338 "the linker's behavior with multiple libraries exporting duplicate symbol \
339 names is undefined and Rust cannot provide guarantees when you manually \
347 impl EarlyLintPass for UnsafeCode {
348 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
349 if cx.sess().check_name(attr, sym::allow_internal_unsafe) {
350 self.report_unsafe(cx, attr.span, |lint| {
352 "`allow_internal_unsafe` allows defining \
353 macros using unsafe without triggering \
354 the `unsafe_code` lint at their call site",
361 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
362 if let ast::ExprKind::Block(ref blk, _) = e.kind {
363 // Don't warn about generated blocks; that'll just pollute the output.
364 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
365 self.report_unsafe(cx, blk.span, |lint| {
366 lint.build("usage of an `unsafe` block").emit()
372 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
374 ast::ItemKind::Trait(box ast::TraitKind(_, ast::Unsafe::Yes(_), ..)) => self
375 .report_unsafe(cx, it.span, |lint| {
376 lint.build("declaration of an `unsafe` trait").emit()
379 ast::ItemKind::Impl(box ast::ImplKind { unsafety: ast::Unsafe::Yes(_), .. }) => self
380 .report_unsafe(cx, it.span, |lint| {
381 lint.build("implementation of an `unsafe` trait").emit()
384 ast::ItemKind::Fn(..) => {
385 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
386 self.report_overriden_symbol_name(
389 "declaration of a `no_mangle` function",
392 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
393 self.report_overriden_symbol_name(
396 "declaration of a function with `export_name`",
401 ast::ItemKind::Static(..) => {
402 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
403 self.report_overriden_symbol_name(
406 "declaration of a `no_mangle` static",
409 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
410 self.report_overriden_symbol_name(
413 "declaration of a static with `export_name`",
422 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
426 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
431 let msg = match ctxt {
432 FnCtxt::Foreign => return,
433 FnCtxt::Free => "declaration of an `unsafe` function",
434 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
435 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
437 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
443 /// The `missing_docs` lint detects missing documentation for public items.
447 /// ```rust,compile_fail
448 /// #![deny(missing_docs)]
456 /// This lint is intended to ensure that a library is well-documented.
457 /// Items without documentation can be difficult for users to understand
458 /// how to use properly.
460 /// This lint is "allow" by default because it can be noisy, and not all
461 /// projects may want to enforce everything to be documented.
464 "detects missing documentation for public members",
465 report_in_external_macro
468 pub struct MissingDoc {
469 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
470 doc_hidden_stack: Vec<bool>,
472 /// Private traits or trait items that leaked through. Don't check their methods.
473 private_traits: FxHashSet<hir::HirId>,
476 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
478 fn has_doc(sess: &Session, attr: &ast::Attribute) -> bool {
479 if attr.is_doc_comment() {
483 if !sess.check_name(attr, sym::doc) {
487 if attr.value_str().is_some() {
491 if let Some(list) = attr.meta_item_list() {
493 if meta.has_name(sym::hidden) {
503 pub fn new() -> MissingDoc {
504 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
507 fn doc_hidden(&self) -> bool {
508 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
511 fn check_missing_docs_attrs(
513 cx: &LateContext<'_>,
516 article: &'static str,
519 // If we're building a test harness, then warning about
520 // documentation is probably not really relevant right now.
521 if cx.sess().opts.test {
525 // `#[doc(hidden)]` disables missing_docs check.
526 if self.doc_hidden() {
530 // Only check publicly-visible items, using the result from the privacy pass.
531 // It's an option so the crate root can also use this function (it doesn't
533 if id != hir::CRATE_HIR_ID {
534 if !cx.access_levels.is_exported(id) {
539 let attrs = cx.tcx.hir().attrs(id);
540 let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
544 cx.tcx.sess.source_map().guess_head_span(sp),
546 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
553 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
554 fn enter_lint_attrs(&mut self, cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
555 let doc_hidden = self.doc_hidden()
556 || attrs.iter().any(|attr| {
557 cx.sess().check_name(attr, sym::doc)
558 && match attr.meta_item_list() {
560 Some(l) => attr::list_contains_name(&l, sym::hidden),
563 self.doc_hidden_stack.push(doc_hidden);
566 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
567 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
570 fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
571 self.check_missing_docs_attrs(cx, hir::CRATE_HIR_ID, krate.item.inner, "the", "crate");
573 for macro_def in krate.exported_macros {
574 let attrs = cx.tcx.hir().attrs(macro_def.hir_id());
575 let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
579 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
580 |lint| lint.build("missing documentation for macro").emit(),
586 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
588 hir::ItemKind::Trait(.., trait_item_refs) => {
589 // Issue #11592: traits are always considered exported, even when private.
590 if let hir::VisibilityKind::Inherited = it.vis.node {
591 self.private_traits.insert(it.hir_id());
592 for trait_item_ref in trait_item_refs {
593 self.private_traits.insert(trait_item_ref.id.hir_id());
598 hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref trait_ref), items, .. }) => {
599 // If the trait is private, add the impl items to `private_traits` so they don't get
600 // reported for missing docs.
601 let real_trait = trait_ref.path.res.def_id();
602 if let Some(def_id) = real_trait.as_local() {
603 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
604 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
605 if let hir::VisibilityKind::Inherited = item.vis.node {
606 for impl_item_ref in items {
607 self.private_traits.insert(impl_item_ref.id.hir_id());
615 hir::ItemKind::TyAlias(..)
616 | hir::ItemKind::Fn(..)
617 | hir::ItemKind::Mod(..)
618 | hir::ItemKind::Enum(..)
619 | hir::ItemKind::Struct(..)
620 | hir::ItemKind::Union(..)
621 | hir::ItemKind::Const(..)
622 | hir::ItemKind::Static(..) => {}
627 let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
629 self.check_missing_docs_attrs(cx, it.hir_id(), it.span, article, desc);
632 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
633 if self.private_traits.contains(&trait_item.hir_id()) {
637 let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
639 self.check_missing_docs_attrs(cx, trait_item.hir_id(), trait_item.span, article, desc);
642 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
643 // If the method is an impl for a trait, don't doc.
644 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
648 let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
649 self.check_missing_docs_attrs(cx, impl_item.hir_id(), impl_item.span, article, desc);
652 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
653 let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
654 self.check_missing_docs_attrs(cx, foreign_item.hir_id(), foreign_item.span, article, desc);
657 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
658 if !sf.is_positional() {
659 self.check_missing_docs_attrs(cx, sf.hir_id, sf.span, "a", "struct field")
663 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
664 self.check_missing_docs_attrs(cx, v.id, v.span, "a", "variant");
669 /// The `missing_copy_implementations` lint detects potentially-forgotten
670 /// implementations of [`Copy`].
672 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
676 /// ```rust,compile_fail
677 /// #![deny(missing_copy_implementations)]
688 /// Historically (before 1.0), types were automatically marked as `Copy`
689 /// if possible. This was changed so that it required an explicit opt-in
690 /// by implementing the `Copy` trait. As part of this change, a lint was
691 /// added to alert if a copyable type was not marked `Copy`.
693 /// This lint is "allow" by default because this code isn't bad; it is
694 /// common to write newtypes like this specifically so that a `Copy` type
695 /// is no longer `Copy`. `Copy` types can result in unintended copies of
696 /// large data which can impact performance.
697 pub MISSING_COPY_IMPLEMENTATIONS,
699 "detects potentially-forgotten implementations of `Copy`"
702 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
704 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
705 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
706 if !cx.access_levels.is_reachable(item.hir_id()) {
709 let (def, ty) = match item.kind {
710 hir::ItemKind::Struct(_, ref ast_generics) => {
711 if !ast_generics.params.is_empty() {
714 let def = cx.tcx.adt_def(item.def_id);
715 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
717 hir::ItemKind::Union(_, ref ast_generics) => {
718 if !ast_generics.params.is_empty() {
721 let def = cx.tcx.adt_def(item.def_id);
722 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
724 hir::ItemKind::Enum(_, ref ast_generics) => {
725 if !ast_generics.params.is_empty() {
728 let def = cx.tcx.adt_def(item.def_id);
729 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
733 if def.has_dtor(cx.tcx) {
736 let param_env = ty::ParamEnv::empty();
737 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
740 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
741 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
743 "type could implement `Copy`; consider adding `impl \
753 /// The `missing_debug_implementations` lint detects missing
754 /// implementations of [`fmt::Debug`].
756 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
760 /// ```rust,compile_fail
761 /// #![deny(missing_debug_implementations)]
770 /// Having a `Debug` implementation on all types can assist with
771 /// debugging, as it provides a convenient way to format and display a
772 /// value. Using the `#[derive(Debug)]` attribute will automatically
773 /// generate a typical implementation, or a custom implementation can be
774 /// added by manually implementing the `Debug` trait.
776 /// This lint is "allow" by default because adding `Debug` to all types can
777 /// have a negative impact on compile time and code size. It also requires
778 /// boilerplate to be added to every type, which can be an impediment.
779 MISSING_DEBUG_IMPLEMENTATIONS,
781 "detects missing implementations of Debug"
785 pub struct MissingDebugImplementations {
786 impling_types: Option<LocalDefIdSet>,
789 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
791 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
792 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
793 if !cx.access_levels.is_reachable(item.hir_id()) {
798 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
802 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
803 Some(debug) => debug,
807 if self.impling_types.is_none() {
808 let mut impls = LocalDefIdSet::default();
809 cx.tcx.for_each_impl(debug, |d| {
810 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
811 if let Some(def_id) = ty_def.did.as_local() {
812 impls.insert(def_id);
817 self.impling_types = Some(impls);
818 debug!("{:?}", self.impling_types);
821 if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
822 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
824 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
825 or a manual implementation",
826 cx.tcx.def_path_str(debug)
835 /// The `anonymous_parameters` lint detects anonymous parameters in trait
840 /// ```rust,edition2015,compile_fail
841 /// #![deny(anonymous_parameters)]
853 /// This syntax is mostly a historical accident, and can be worked around
854 /// quite easily by adding an `_` pattern or a descriptive identifier:
858 /// fn foo(_: usize);
862 /// This syntax is now a hard error in the 2018 edition. In the 2015
863 /// edition, this lint is "warn" by default. This lint
864 /// enables the [`cargo fix`] tool with the `--edition` flag to
865 /// automatically transition old code from the 2015 edition to 2018. The
866 /// tool will run this lint and automatically apply the
867 /// suggested fix from the compiler (which is to add `_` to each
868 /// parameter). This provides a completely automated way to update old
869 /// code for a new edition. See [issue #41686] for more details.
871 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
872 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
873 pub ANONYMOUS_PARAMETERS,
875 "detects anonymous parameters",
876 @future_incompatible = FutureIncompatibleInfo {
877 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
878 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
883 /// Checks for use of anonymous parameters (RFC 1685).
884 AnonymousParameters => [ANONYMOUS_PARAMETERS]
887 impl EarlyLintPass for AnonymousParameters {
888 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
889 if cx.sess.edition() != Edition::Edition2015 {
890 // This is a hard error in future editions; avoid linting and erroring
893 if let ast::AssocItemKind::Fn(box FnKind(_, ref sig, _, _)) = it.kind {
894 for arg in sig.decl.inputs.iter() {
895 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
896 if ident.name == kw::Empty {
897 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
898 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
900 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
901 (snip.as_str(), Applicability::MachineApplicable)
903 ("<type>", Applicability::HasPlaceholders)
907 "anonymous parameters are deprecated and will be \
908 removed in the next edition.",
912 "try naming the parameter or explicitly \
914 format!("_: {}", ty_snip),
926 /// Check for use of attributes which have been deprecated.
928 pub struct DeprecatedAttr {
929 // This is not free to compute, so we want to keep it around, rather than
930 // compute it for every attribute.
931 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
934 impl_lint_pass!(DeprecatedAttr => []);
936 impl DeprecatedAttr {
937 pub fn new() -> DeprecatedAttr {
938 DeprecatedAttr { depr_attrs: deprecated_attributes() }
942 fn lint_deprecated_attr(
943 cx: &EarlyContext<'_>,
944 attr: &ast::Attribute,
946 suggestion: Option<&str>,
948 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
950 .span_suggestion_short(
952 suggestion.unwrap_or("remove this attribute"),
954 Applicability::MachineApplicable,
960 impl EarlyLintPass for DeprecatedAttr {
961 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
962 for &&(n, _, _, ref g) in &self.depr_attrs {
963 if attr.ident().map(|ident| ident.name) == Some(n) {
964 if let &AttributeGate::Gated(
965 Stability::Deprecated(link, suggestion),
972 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
973 lint_deprecated_attr(cx, attr, &msg, suggestion);
978 if cx.sess().check_name(attr, sym::no_start) || cx.sess().check_name(attr, sym::crate_id) {
979 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
980 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
981 lint_deprecated_attr(cx, attr, &msg, None);
986 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
987 let mut attrs = attrs.iter().peekable();
989 // Accumulate a single span for sugared doc comments.
990 let mut sugared_span: Option<Span> = None;
992 while let Some(attr) = attrs.next() {
993 if attr.is_doc_comment() {
995 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
998 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1002 let span = sugared_span.take().unwrap_or(attr.span);
1004 if attr.is_doc_comment() || cx.sess().check_name(attr, sym::doc) {
1005 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1006 let mut err = lint.build("unused doc comment");
1009 format!("rustdoc does not generate documentation for {}", node_kind),
1017 impl EarlyLintPass for UnusedDocComment {
1018 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1019 let kind = match stmt.kind {
1020 ast::StmtKind::Local(..) => "statements",
1021 // Disabled pending discussion in #78306
1022 ast::StmtKind::Item(..) => return,
1023 // expressions will be reported by `check_expr`.
1024 ast::StmtKind::Empty
1025 | ast::StmtKind::Semi(_)
1026 | ast::StmtKind::Expr(_)
1027 | ast::StmtKind::MacCall(_) => return,
1030 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1033 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1034 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1035 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1038 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1039 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1044 /// The `no_mangle_const_items` lint detects any `const` items with the
1045 /// [`no_mangle` attribute].
1047 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1051 /// ```rust,compile_fail
1053 /// const FOO: i32 = 5;
1060 /// Constants do not have their symbols exported, and therefore, this
1061 /// probably means you meant to use a [`static`], not a [`const`].
1063 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1064 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1065 NO_MANGLE_CONST_ITEMS,
1067 "const items will not have their symbols exported"
1071 /// The `no_mangle_generic_items` lint detects generic items that must be
1078 /// fn foo<T>(t: T) {
1087 /// An function with generics must have its symbol mangled to accommodate
1088 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1089 /// this situation, and should be removed.
1091 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1092 NO_MANGLE_GENERIC_ITEMS,
1094 "generic items must be mangled"
1097 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1099 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1100 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1101 let attrs = cx.tcx.hir().attrs(it.hir_id());
1103 hir::ItemKind::Fn(.., ref generics, _) => {
1104 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1105 for param in generics.params {
1107 GenericParamKind::Lifetime { .. } => {}
1108 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1109 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
1111 "functions generic over types or consts must be mangled",
1113 .span_suggestion_short(
1114 no_mangle_attr.span,
1115 "remove this attribute",
1117 // Use of `#[no_mangle]` suggests FFI intent; correct
1118 // fix may be to monomorphize source by hand
1119 Applicability::MaybeIncorrect,
1129 hir::ItemKind::Const(..) => {
1130 if cx.sess().contains_name(attrs, sym::no_mangle) {
1131 // Const items do not refer to a particular location in memory, and therefore
1132 // don't have anything to attach a symbol to
1133 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1134 let msg = "const items should never be `#[no_mangle]`";
1135 let mut err = lint.build(msg);
1137 // account for "pub const" (#45562)
1142 .span_to_snippet(it.span)
1143 .map(|snippet| snippet.find("const").unwrap_or(0))
1144 .unwrap_or(0) as u32;
1145 // `const` is 5 chars
1146 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1147 err.span_suggestion(
1149 "try a static value",
1150 "pub static".to_owned(),
1151 Applicability::MachineApplicable,
1163 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1164 /// T` because it is [undefined behavior].
1166 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1170 /// ```rust,compile_fail
1172 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1180 /// Certain assumptions are made about aliasing of data, and this transmute
1181 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1183 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1186 "mutating transmuted &mut T from &T may cause undefined behavior"
1189 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1191 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1192 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1193 use rustc_target::spec::abi::Abi::RustIntrinsic;
1194 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1195 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1197 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1198 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1199 consider instead using an UnsafeCell";
1200 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
1204 fn get_transmute_from_to<'tcx>(
1205 cx: &LateContext<'tcx>,
1206 expr: &hir::Expr<'_>,
1207 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1208 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1209 cx.qpath_res(qpath, expr.hir_id)
1213 if let Res::Def(DefKind::Fn, did) = def {
1214 if !def_id_is_transmute(cx, did) {
1217 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1218 let from = sig.inputs().skip_binder()[0];
1219 let to = sig.output().skip_binder();
1220 return Some((from, to));
1225 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1226 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
1227 && cx.tcx.item_name(def_id) == sym::transmute
1233 /// The `unstable_features` is deprecated and should no longer be used.
1236 "enabling unstable features (deprecated. do not use)"
1240 /// Forbids using the `#[feature(...)]` attribute
1241 UnstableFeatures => [UNSTABLE_FEATURES]
1244 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1245 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1246 if cx.sess().check_name(attr, sym::feature) {
1247 if let Some(items) = attr.meta_item_list() {
1249 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1250 lint.build("unstable feature").emit()
1259 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1264 /// ```rust,compile_fail
1265 /// #![deny(unreachable_pub)]
1277 /// A bare `pub` visibility may be misleading if the item is not actually
1278 /// publicly exported from the crate. The `pub(crate)` visibility is
1279 /// recommended to be used instead, which more clearly expresses the intent
1280 /// that the item is only visible within its own crate.
1282 /// This lint is "allow" by default because it will trigger for a large
1283 /// amount existing Rust code, and has some false-positives. Eventually it
1284 /// is desired for this to become warn-by-default.
1285 pub UNREACHABLE_PUB,
1287 "`pub` items not reachable from crate root"
1291 /// Lint for items marked `pub` that aren't reachable from other crates.
1292 UnreachablePub => [UNREACHABLE_PUB]
1295 impl UnreachablePub {
1298 cx: &LateContext<'_>,
1301 vis: &hir::Visibility<'_>,
1305 let mut applicability = Applicability::MachineApplicable;
1307 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1308 if span.from_expansion() {
1309 applicability = Applicability::MaybeIncorrect;
1311 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1312 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1313 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1314 let replacement = if cx.tcx.features().crate_visibility_modifier {
1321 err.span_suggestion(
1323 "consider restricting its visibility",
1328 err.help("or consider exporting it for use by other crates");
1338 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1339 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1340 self.perform_lint(cx, "item", item.hir_id(), &item.vis, item.span, true);
1343 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1347 foreign_item.hir_id(),
1354 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1355 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1358 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1359 self.perform_lint(cx, "item", impl_item.hir_id(), &impl_item.vis, impl_item.span, false);
1364 /// The `type_alias_bounds` lint detects bounds in type aliases.
1369 /// type SendVec<T: Send> = Vec<T>;
1376 /// The trait bounds in a type alias are currently ignored, and should not
1377 /// be included to avoid confusion. This was previously allowed
1378 /// unintentionally; this may become a hard error in the future.
1381 "bounds in type aliases are not enforced"
1385 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1386 /// They are relevant when using associated types, but otherwise neither checked
1387 /// at definition site nor enforced at use site.
1388 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1391 impl TypeAliasBounds {
1392 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1394 hir::QPath::TypeRelative(ref ty, _) => {
1395 // If this is a type variable, we found a `T::Assoc`.
1397 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1398 matches!(path.res, Res::Def(DefKind::TyParam, _))
1403 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1407 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1408 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1409 // bound. Let's see if this type does that.
1411 // We use a HIR visitor to walk the type.
1412 use rustc_hir::intravisit::{self, Visitor};
1413 struct WalkAssocTypes<'a, 'db> {
1414 err: &'a mut DiagnosticBuilder<'db>,
1416 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1417 type Map = intravisit::ErasedMap<'v>;
1419 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1420 intravisit::NestedVisitorMap::None
1423 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1424 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1427 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1428 associated types in type aliases",
1431 intravisit::walk_qpath(self, qpath, id, span)
1435 // Let's go for a walk!
1436 let mut visitor = WalkAssocTypes { err };
1437 visitor.visit_ty(ty);
1441 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1442 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1443 let (ty, type_alias_generics) = match item.kind {
1444 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1447 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1448 // Bounds are respected for `type X = impl Trait`
1451 let mut suggested_changing_assoc_types = false;
1452 // There must not be a where clause
1453 if !type_alias_generics.where_clause.predicates.is_empty() {
1457 let mut err = lint.build("where clauses are not enforced in type aliases");
1458 let spans: Vec<_> = type_alias_generics
1462 .map(|pred| pred.span())
1464 err.set_span(spans);
1465 err.span_suggestion(
1466 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1467 "the clause will not be checked when the type alias is used, and should be removed",
1469 Applicability::MachineApplicable,
1471 if !suggested_changing_assoc_types {
1472 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1473 suggested_changing_assoc_types = true;
1479 // The parameters must not have bounds
1480 for param in type_alias_generics.params.iter() {
1481 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1482 let suggestion = spans
1485 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1486 (start.to(*sp), String::new())
1489 if !spans.is_empty() {
1490 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1492 lint.build("bounds on generic parameters are not enforced in type aliases");
1493 let msg = "the bound will not be checked when the type alias is used, \
1494 and should be removed";
1495 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1496 if !suggested_changing_assoc_types {
1497 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1498 suggested_changing_assoc_types = true;
1508 /// Lint constants that are erroneous.
1509 /// Without this lint, we might not get any diagnostic if the constant is
1510 /// unused within this crate, even though downstream crates can't use it
1511 /// without producing an error.
1512 UnusedBrokenConst => []
1515 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1516 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1518 hir::ItemKind::Const(_, body_id) => {
1519 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1520 // trigger the query once for all constants since that will already report the errors
1521 // FIXME: Use ensure here
1522 let _ = cx.tcx.const_eval_poly(def_id);
1524 hir::ItemKind::Static(_, _, body_id) => {
1525 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1526 // FIXME: Use ensure here
1527 let _ = cx.tcx.eval_static_initializer(def_id);
1535 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1536 /// any type parameters.
1541 /// #![feature(trivial_bounds)]
1542 /// pub struct A where i32: Copy;
1549 /// Usually you would not write a trait bound that you know is always
1550 /// true, or never true. However, when using macros, the macro may not
1551 /// know whether or not the constraint would hold or not at the time when
1552 /// generating the code. Currently, the compiler does not alert you if the
1553 /// constraint is always true, and generates an error if it is never true.
1554 /// The `trivial_bounds` feature changes this to be a warning in both
1555 /// cases, giving macros more freedom and flexibility to generate code,
1556 /// while still providing a signal when writing non-macro code that
1557 /// something is amiss.
1559 /// See [RFC 2056] for more details. This feature is currently only
1560 /// available on the nightly channel, see [tracking issue #48214].
1562 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1563 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1566 "these bounds don't depend on an type parameters"
1570 /// Lint for trait and lifetime bounds that don't depend on type parameters
1571 /// which either do nothing, or stop the item from being used.
1572 TrivialConstraints => [TRIVIAL_BOUNDS]
1575 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1576 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1577 use rustc_middle::ty::fold::TypeFoldable;
1578 use rustc_middle::ty::PredicateKind::*;
1580 if cx.tcx.features().trivial_bounds {
1581 let predicates = cx.tcx.predicates_of(item.def_id);
1582 for &(predicate, span) in predicates.predicates {
1583 let predicate_kind_name = match predicate.kind().skip_binder() {
1584 Trait(..) => "Trait",
1586 RegionOutlives(..) => "Lifetime",
1588 // Ignore projections, as they can only be global
1589 // if the trait bound is global
1591 // Ignore bounds that a user can't type
1596 ConstEvaluatable(..) |
1598 TypeWellFormedFromEnv(..) => continue,
1600 if predicate.is_global() {
1601 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1602 lint.build(&format!(
1603 "{} bound {} does not depend on any type \
1604 or lifetime parameters",
1605 predicate_kind_name, predicate
1616 /// Does nothing as a lint pass, but registers some `Lint`s
1617 /// which are used by other parts of the compiler.
1621 NON_SHORTHAND_FIELD_PATTERNS,
1624 MISSING_COPY_IMPLEMENTATIONS,
1625 MISSING_DEBUG_IMPLEMENTATIONS,
1626 ANONYMOUS_PARAMETERS,
1627 UNUSED_DOC_COMMENTS,
1628 NO_MANGLE_CONST_ITEMS,
1629 NO_MANGLE_GENERIC_ITEMS,
1639 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1640 /// pattern], which is deprecated.
1642 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1658 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1659 /// confusion with the [`..` range expression]. Use the new form instead.
1661 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1662 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1664 "`...` range patterns are deprecated",
1665 @future_incompatible = FutureIncompatibleInfo {
1666 reference: "issue #80165 <https://github.com/rust-lang/rust/issues/80165>",
1667 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1672 pub struct EllipsisInclusiveRangePatterns {
1673 /// If `Some(_)`, suppress all subsequent pattern
1674 /// warnings for better diagnostics.
1675 node_id: Option<ast::NodeId>,
1678 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1680 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1681 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1682 if self.node_id.is_some() {
1683 // Don't recursively warn about patterns inside range endpoints.
1687 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1689 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1690 /// corresponding to the ellipsis.
1691 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1696 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1697 ) => Some((a.as_deref(), b, *span)),
1702 let (parenthesise, endpoints) = match &pat.kind {
1703 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1704 _ => (false, matches_ellipsis_pat(pat)),
1707 if let Some((start, end, join)) = endpoints {
1708 let msg = "`...` range patterns are deprecated";
1709 let suggestion = "use `..=` for an inclusive range";
1711 self.node_id = Some(pat.id);
1712 let end = expr_to_string(&end);
1713 let replace = match start {
1714 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1715 None => format!("&(..={})", end),
1717 if join.edition() >= Edition::Edition2021 {
1719 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1720 err.span_suggestion(
1724 Applicability::MachineApplicable,
1728 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1734 Applicability::MachineApplicable,
1740 let replace = "..=".to_owned();
1741 if join.edition() >= Edition::Edition2021 {
1743 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1744 err.span_suggestion_short(
1748 Applicability::MachineApplicable,
1752 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1754 .span_suggestion_short(
1758 Applicability::MachineApplicable,
1767 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1768 if let Some(node_id) = self.node_id {
1769 if pat.id == node_id {
1777 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1778 /// that are not able to be run by the test harness because they are in a
1779 /// position where they are not nameable.
1781 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1789 /// // This test will not fail because it does not run.
1790 /// assert_eq!(1, 2);
1799 /// In order for the test harness to run a test, the test function must be
1800 /// located in a position where it can be accessed from the crate root.
1801 /// This generally means it must be defined in a module, and not anywhere
1802 /// else such as inside another function. The compiler previously allowed
1803 /// this without an error, so a lint was added as an alert that a test is
1804 /// not being used. Whether or not this should be allowed has not yet been
1805 /// decided, see [RFC 2471] and [issue #36629].
1807 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1808 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1809 UNNAMEABLE_TEST_ITEMS,
1811 "detects an item that cannot be named being marked as `#[test_case]`",
1812 report_in_external_macro
1815 pub struct UnnameableTestItems {
1816 boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1817 items_nameable: bool,
1820 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1822 impl UnnameableTestItems {
1823 pub fn new() -> Self {
1824 Self { boundary: None, items_nameable: true }
1828 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1829 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1830 if self.items_nameable {
1831 if let hir::ItemKind::Mod(..) = it.kind {
1833 self.items_nameable = false;
1834 self.boundary = Some(it.def_id);
1839 let attrs = cx.tcx.hir().attrs(it.hir_id());
1840 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1841 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1842 lint.build("cannot test inner items").emit()
1847 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1848 if !self.items_nameable && self.boundary == Some(it.def_id) {
1849 self.items_nameable = true;
1855 /// The `keyword_idents` lint detects edition keywords being used as an
1860 /// ```rust,edition2015,compile_fail
1861 /// #![deny(keyword_idents)]
1870 /// Rust [editions] allow the language to evolve without breaking
1871 /// backwards compatibility. This lint catches code that uses new keywords
1872 /// that are added to the language that are used as identifiers (such as a
1873 /// variable name, function name, etc.). If you switch the compiler to a
1874 /// new edition without updating the code, then it will fail to compile if
1875 /// you are using a new keyword as an identifier.
1877 /// You can manually change the identifiers to a non-keyword, or use a
1878 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1880 /// This lint solves the problem automatically. It is "allow" by default
1881 /// because the code is perfectly valid in older editions. The [`cargo
1882 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1883 /// and automatically apply the suggested fix from the compiler (which is
1884 /// to use a raw identifier). This provides a completely automated way to
1885 /// update old code for a new edition.
1887 /// [editions]: https://doc.rust-lang.org/edition-guide/
1888 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1889 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1892 "detects edition keywords being used as an identifier",
1893 @future_incompatible = FutureIncompatibleInfo {
1894 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1895 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1900 /// Check for uses of edition keywords used as an identifier.
1901 KeywordIdents => [KEYWORD_IDENTS]
1904 struct UnderMacro(bool);
1906 impl KeywordIdents {
1907 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1908 for tt in tokens.into_trees() {
1910 // Only report non-raw idents.
1911 TokenTree::Token(token) => {
1912 if let Some((ident, false)) = token.ident() {
1913 self.check_ident_token(cx, UnderMacro(true), ident);
1916 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1921 fn check_ident_token(
1923 cx: &EarlyContext<'_>,
1924 UnderMacro(under_macro): UnderMacro,
1927 let next_edition = match cx.sess.edition() {
1928 Edition::Edition2015 => {
1930 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1932 // rust-lang/rust#56327: Conservatively do not
1933 // attempt to report occurrences of `dyn` within
1934 // macro definitions or invocations, because `dyn`
1935 // can legitimately occur as a contextual keyword
1936 // in 2015 code denoting its 2018 meaning, and we
1937 // do not want rustfix to inject bugs into working
1938 // code by rewriting such occurrences.
1940 // But if we see `dyn` outside of a macro, we know
1941 // its precise role in the parsed AST and thus are
1942 // assured this is truly an attempt to use it as
1944 kw::Dyn if !under_macro => Edition::Edition2018,
1950 // There are no new keywords yet for the 2018 edition and beyond.
1954 // Don't lint `r#foo`.
1955 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1959 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1960 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1963 "you can use a raw identifier to stay compatible",
1964 format!("r#{}", ident),
1965 Applicability::MachineApplicable,
1972 impl EarlyLintPass for KeywordIdents {
1973 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1974 self.check_tokens(cx, mac_def.body.inner_tokens());
1976 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1977 self.check_tokens(cx, mac.args.inner_tokens());
1979 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1980 self.check_ident_token(cx, UnderMacro(false), ident);
1984 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1986 impl ExplicitOutlivesRequirements {
1987 fn lifetimes_outliving_lifetime<'tcx>(
1988 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1990 ) -> Vec<ty::Region<'tcx>> {
1993 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
1994 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
1995 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2003 fn lifetimes_outliving_type<'tcx>(
2004 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2006 ) -> Vec<ty::Region<'tcx>> {
2009 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2010 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2011 a.is_param(index).then_some(b)
2018 fn collect_outlived_lifetimes<'tcx>(
2020 param: &'tcx hir::GenericParam<'tcx>,
2022 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2023 ty_generics: &'tcx ty::Generics,
2024 ) -> Vec<ty::Region<'tcx>> {
2026 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
2029 hir::GenericParamKind::Lifetime { .. } => {
2030 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
2032 hir::GenericParamKind::Type { .. } => {
2033 Self::lifetimes_outliving_type(inferred_outlives, index)
2035 hir::GenericParamKind::Const { .. } => Vec::new(),
2039 fn collect_outlives_bound_spans<'tcx>(
2042 bounds: &hir::GenericBounds<'_>,
2043 inferred_outlives: &[ty::Region<'tcx>],
2045 ) -> Vec<(usize, Span)> {
2046 use rustc_middle::middle::resolve_lifetime::Region;
2051 .filter_map(|(i, bound)| {
2052 if let hir::GenericBound::Outlives(lifetime) = bound {
2053 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2054 Some(Region::Static) if infer_static => {
2055 inferred_outlives.iter().any(|r| matches!(r, ty::ReStatic))
2057 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2058 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
2062 is_inferred.then_some((i, bound.span()))
2070 fn consolidate_outlives_bound_spans(
2073 bounds: &hir::GenericBounds<'_>,
2074 bound_spans: Vec<(usize, Span)>,
2076 if bounds.is_empty() {
2079 if bound_spans.len() == bounds.len() {
2080 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2081 // If all bounds are inferable, we want to delete the colon, so
2082 // start from just after the parameter (span passed as argument)
2083 vec![lo.to(last_bound_span)]
2085 let mut merged = Vec::new();
2086 let mut last_merged_i = None;
2088 let mut from_start = true;
2089 for (i, bound_span) in bound_spans {
2090 match last_merged_i {
2091 // If the first bound is inferable, our span should also eat the leading `+`.
2093 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2094 last_merged_i = Some(0);
2096 // If consecutive bounds are inferable, merge their spans
2097 Some(h) if i == h + 1 => {
2098 if let Some(tail) = merged.last_mut() {
2099 // Also eat the trailing `+` if the first
2100 // more-than-one bound is inferable
2101 let to_span = if from_start && i < bounds.len() {
2102 bounds[i + 1].span().shrink_to_lo()
2106 *tail = tail.to(to_span);
2107 last_merged_i = Some(i);
2109 bug!("another bound-span visited earlier");
2113 // When we find a non-inferable bound, subsequent inferable bounds
2114 // won't be consecutive from the start (and we'll eat the leading
2115 // `+` rather than the trailing one)
2117 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2118 last_merged_i = Some(i);
2127 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2128 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2129 use rustc_middle::middle::resolve_lifetime::Region;
2131 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
2132 let def_id = item.def_id;
2133 if let hir::ItemKind::Struct(_, ref hir_generics)
2134 | hir::ItemKind::Enum(_, ref hir_generics)
2135 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2137 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2138 if inferred_outlives.is_empty() {
2142 let ty_generics = cx.tcx.generics_of(def_id);
2144 let mut bound_count = 0;
2145 let mut lint_spans = Vec::new();
2147 for param in hir_generics.params {
2148 let has_lifetime_bounds = param
2151 .any(|bound| matches!(bound, hir::GenericBound::Outlives(_)));
2152 if !has_lifetime_bounds {
2156 let relevant_lifetimes =
2157 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
2158 if relevant_lifetimes.is_empty() {
2162 let bound_spans = self.collect_outlives_bound_spans(
2165 &relevant_lifetimes,
2168 bound_count += bound_spans.len();
2169 lint_spans.extend(self.consolidate_outlives_bound_spans(
2170 param.span.shrink_to_hi(),
2176 let mut where_lint_spans = Vec::new();
2177 let mut dropped_predicate_count = 0;
2178 let num_predicates = hir_generics.where_clause.predicates.len();
2179 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
2180 let (relevant_lifetimes, bounds, span) = match where_predicate {
2181 hir::WherePredicate::RegionPredicate(predicate) => {
2182 if let Some(Region::EarlyBound(index, ..)) =
2183 cx.tcx.named_region(predicate.lifetime.hir_id)
2186 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2194 hir::WherePredicate::BoundPredicate(predicate) => {
2195 // FIXME we can also infer bounds on associated types,
2196 // and should check for them here.
2197 match predicate.bounded_ty.kind {
2198 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2199 if let Res::Def(DefKind::TyParam, def_id) = path.res {
2200 let index = ty_generics.param_def_id_to_index[&def_id];
2202 Self::lifetimes_outliving_type(inferred_outlives, index),
2217 if relevant_lifetimes.is_empty() {
2221 let bound_spans = self.collect_outlives_bound_spans(
2224 &relevant_lifetimes,
2227 bound_count += bound_spans.len();
2229 let drop_predicate = bound_spans.len() == bounds.len();
2231 dropped_predicate_count += 1;
2234 // If all the bounds on a predicate were inferable and there are
2235 // further predicates, we want to eat the trailing comma.
2236 if drop_predicate && i + 1 < num_predicates {
2237 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
2238 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2240 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2241 span.shrink_to_lo(),
2248 // If all predicates are inferable, drop the entire clause
2249 // (including the `where`)
2250 if num_predicates > 0 && dropped_predicate_count == num_predicates {
2251 let where_span = hir_generics
2254 .expect("span of (nonempty) where clause should exist");
2255 // Extend the where clause back to the closing `>` of the
2256 // generics, except for tuple struct, which have the `where`
2257 // after the fields of the struct.
2258 let full_where_span =
2259 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2262 hir_generics.span.shrink_to_hi().to(where_span)
2264 lint_spans.push(full_where_span);
2266 lint_spans.extend(where_lint_spans);
2269 if !lint_spans.is_empty() {
2270 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2271 lint.build("outlives requirements can be inferred")
2272 .multipart_suggestion(
2273 if bound_count == 1 {
2276 "remove these bounds"
2280 .map(|span| (span, "".to_owned()))
2281 .collect::<Vec<_>>(),
2282 Applicability::MachineApplicable,
2292 /// The `incomplete_features` lint detects unstable features enabled with
2293 /// the [`feature` attribute] that may function improperly in some or all
2296 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2301 /// #![feature(generic_associated_types)]
2308 /// Although it is encouraged for people to experiment with unstable
2309 /// features, some of them are known to be incomplete or faulty. This lint
2310 /// is a signal that the feature has not yet been finished, and you may
2311 /// experience problems with it.
2312 pub INCOMPLETE_FEATURES,
2314 "incomplete features that may function improperly in some or all cases"
2318 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2319 IncompleteFeatures => [INCOMPLETE_FEATURES]
2322 impl EarlyLintPass for IncompleteFeatures {
2323 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2324 let features = cx.sess.features_untracked();
2326 .declared_lang_features
2328 .map(|(name, span, _)| (name, span))
2329 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2330 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
2331 .for_each(|(&name, &span)| {
2332 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2333 let mut builder = lint.build(&format!(
2334 "the feature `{}` is incomplete and may not be safe to use \
2335 and/or cause compiler crashes",
2338 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2339 builder.note(&format!(
2340 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
2341 for more information",
2345 if HAS_MIN_FEATURES.contains(&name) {
2346 builder.help(&format!(
2347 "consider using `min_{}` instead, which is more stable and complete",
2357 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2360 /// The `invalid_value` lint detects creating a value that is not valid,
2361 /// such as a null reference.
2366 /// # #![allow(unused)]
2368 /// let x: &'static i32 = std::mem::zeroed();
2376 /// In some situations the compiler can detect that the code is creating
2377 /// an invalid value, which should be avoided.
2379 /// In particular, this lint will check for improper use of
2380 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2381 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2382 /// lint should provide extra information to indicate what the problem is
2383 /// and a possible solution.
2385 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2386 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2387 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2388 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2389 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2392 "an invalid value is being created (such as a null reference)"
2395 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2397 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2398 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2399 #[derive(Debug, Copy, Clone, PartialEq)]
2405 /// Information about why a type cannot be initialized this way.
2406 /// Contains an error message and optionally a span to point at.
2407 type InitError = (String, Option<Span>);
2409 /// Test if this constant is all-0.
2410 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2411 use hir::ExprKind::*;
2412 use rustc_ast::LitKind::*;
2415 if let Int(i, _) = lit.node {
2421 Tup(tup) => tup.iter().all(is_zero),
2426 /// Determine if this expression is a "dangerous initialization".
2427 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2428 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2429 // Find calls to `mem::{uninitialized,zeroed}` methods.
2430 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2431 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2433 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
2434 return Some(InitKind::Zeroed);
2435 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
2436 return Some(InitKind::Uninit);
2437 } else if cx.tcx.is_diagnostic_item(sym::transmute, def_id) && is_zero(&args[0])
2439 return Some(InitKind::Zeroed);
2442 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
2443 // Find problematic calls to `MaybeUninit::assume_init`.
2444 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2445 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2446 // This is a call to *some* method named `assume_init`.
2447 // See if the `self` parameter is one of the dangerous constructors.
2448 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2449 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2450 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2452 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
2453 return Some(InitKind::Zeroed);
2454 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
2455 return Some(InitKind::Uninit);
2465 /// Test if this enum has several actually "existing" variants.
2466 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2467 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
2468 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2469 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
2470 existing_variants > 1
2473 /// Return `Some` only if we are sure this type does *not*
2474 /// allow zero initialization.
2475 fn ty_find_init_error<'tcx>(
2479 ) -> Option<InitError> {
2480 use rustc_middle::ty::TyKind::*;
2482 // Primitive types that don't like 0 as a value.
2483 Ref(..) => Some(("references must be non-null".to_string(), None)),
2484 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2485 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2486 Never => Some(("the `!` type has no valid value".to_string(), None)),
2487 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2488 // raw ptr to dyn Trait
2490 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2492 // Primitive types with other constraints.
2493 Bool if init == InitKind::Uninit => {
2494 Some(("booleans must be either `true` or `false`".to_string(), None))
2496 Char if init == InitKind::Uninit => {
2497 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2499 // Recurse and checks for some compound types.
2500 Adt(adt_def, substs) if !adt_def.is_union() => {
2501 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2502 use std::ops::Bound;
2503 match tcx.layout_scalar_valid_range(adt_def.did) {
2504 // We exploit here that `layout_scalar_valid_range` will never
2505 // return `Bound::Excluded`. (And we have tests checking that we
2506 // handle the attribute correctly.)
2507 (Bound::Included(lo), _) if lo > 0 => {
2508 return Some((format!("`{}` must be non-null", ty), None));
2510 (Bound::Included(_), _) | (_, Bound::Included(_))
2511 if init == InitKind::Uninit =>
2515 "`{}` must be initialized inside its custom valid range",
2524 match adt_def.variants.len() {
2525 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2527 // Struct, or enum with exactly one variant.
2528 // Proceed recursively, check all fields.
2529 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2530 variant.fields.iter().find_map(|field| {
2531 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2534 // Point to this field, should be helpful for figuring
2535 // out where the source of the error is.
2536 let span = tcx.def_span(field.did);
2539 " (in this {} field)",
2552 // Multi-variant enum.
2554 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2555 let span = tcx.def_span(adt_def.did);
2557 "enums have to be initialized to a variant".to_string(),
2561 // In principle, for zero-initialization we could figure out which variant corresponds
2562 // to tag 0, and check that... but for now we just accept all zero-initializations.
2569 // Proceed recursively, check all fields.
2570 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2572 // Conservative fallback.
2577 if let Some(init) = is_dangerous_init(cx, expr) {
2578 // This conjures an instance of a type out of nothing,
2579 // using zeroed or uninitialized memory.
2580 // We are extremely conservative with what we warn about.
2581 let conjured_ty = cx.typeck_results().expr_ty(expr);
2582 if let Some((msg, span)) =
2583 with_no_trimmed_paths(|| ty_find_init_error(cx.tcx, conjured_ty, init))
2585 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2586 let mut err = lint.build(&format!(
2587 "the type `{}` does not permit {}",
2590 InitKind::Zeroed => "zero-initialization",
2591 InitKind::Uninit => "being left uninitialized",
2594 err.span_label(expr.span, "this code causes undefined behavior when executed");
2597 "help: use `MaybeUninit<T>` instead, \
2598 and only call `assume_init` after initialization is done",
2600 if let Some(span) = span {
2601 err.span_note(span, &msg);
2613 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2614 /// has been declared with the same name but different types.
2634 /// Because two symbols of the same name cannot be resolved to two
2635 /// different functions at link time, and one function cannot possibly
2636 /// have two types, a clashing extern declaration is almost certainly a
2637 /// mistake. Check to make sure that the `extern` definitions are correct
2638 /// and equivalent, and possibly consider unifying them in one location.
2640 /// This lint does not run between crates because a project may have
2641 /// dependencies which both rely on the same extern function, but declare
2642 /// it in a different (but valid) way. For example, they may both declare
2643 /// an opaque type for one or more of the arguments (which would end up
2644 /// distinct types), or use types that are valid conversions in the
2645 /// language the `extern fn` is defined in. In these cases, the compiler
2646 /// can't say that the clashing declaration is incorrect.
2647 pub CLASHING_EXTERN_DECLARATIONS,
2649 "detects when an extern fn has been declared with the same name but different types"
2652 pub struct ClashingExternDeclarations {
2653 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2654 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2655 /// the symbol should be reported as a clashing declaration.
2656 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2657 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2658 seen_decls: FxHashMap<Symbol, HirId>,
2661 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2662 /// just from declaration itself. This is important because we don't want to report clashes on
2663 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2666 /// The name of the symbol + the span of the annotation which introduced the link name.
2668 /// No link name, so just the name of the symbol.
2673 fn get_name(&self) -> Symbol {
2675 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2680 impl ClashingExternDeclarations {
2681 crate fn new() -> Self {
2682 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2684 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2685 /// for the item, return its HirId without updating the set.
2686 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2687 let did = fi.def_id.to_def_id();
2688 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2689 let name = Symbol::intern(tcx.symbol_name(instance).name);
2690 if let Some(&hir_id) = self.seen_decls.get(&name) {
2691 // Avoid updating the map with the new entry when we do find a collision. We want to
2692 // make sure we're always pointing to the first definition as the previous declaration.
2693 // This lets us avoid emitting "knock-on" diagnostics.
2696 self.seen_decls.insert(name, fi.hir_id())
2700 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2701 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2703 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2704 if let Some((overridden_link_name, overridden_link_name_span)) =
2705 tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2706 // FIXME: Instead of searching through the attributes again to get span
2707 // information, we could have codegen_fn_attrs also give span information back for
2708 // where the attribute was defined. However, until this is found to be a
2709 // bottleneck, this does just fine.
2711 overridden_link_name,
2712 tcx.get_attrs(fi.def_id.to_def_id())
2714 .find(|at| tcx.sess.check_name(at, sym::link_name))
2720 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2722 SymbolName::Normal(fi.ident.name)
2726 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2727 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2728 /// with the same members (as the declarations shouldn't clash).
2729 fn structurally_same_type<'tcx>(
2730 cx: &LateContext<'tcx>,
2735 fn structurally_same_type_impl<'tcx>(
2736 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2737 cx: &LateContext<'tcx>,
2742 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2745 // Given a transparent newtype, reach through and grab the inner
2746 // type unless the newtype makes the type non-null.
2747 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2750 if let ty::Adt(def, substs) = *ty.kind() {
2751 let is_transparent = def.subst(tcx, substs).repr.transparent();
2752 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, &def);
2754 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2755 ty, is_transparent, is_non_null
2757 if is_transparent && !is_non_null {
2758 debug_assert!(def.variants.len() == 1);
2759 let v = &def.variants[VariantIdx::new(0)];
2760 ty = transparent_newtype_field(tcx, v)
2762 "single-variant transparent structure with zero-sized field",
2768 debug!("non_transparent_ty -> {:?}", ty);
2773 let a = non_transparent_ty(a);
2774 let b = non_transparent_ty(b);
2776 if !seen_types.insert((a, b)) {
2777 // We've encountered a cycle. There's no point going any further -- the types are
2778 // structurally the same.
2782 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2783 // All nominally-same types are structurally same, too.
2786 // Do a full, depth-first comparison between the two.
2787 use rustc_middle::ty::TyKind::*;
2788 let a_kind = a.kind();
2789 let b_kind = b.kind();
2791 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2792 debug!("compare_layouts({:?}, {:?})", a, b);
2793 let a_layout = &cx.layout_of(a)?.layout.abi;
2794 let b_layout = &cx.layout_of(b)?.layout.abi;
2796 "comparing layouts: {:?} == {:?} = {}",
2799 a_layout == b_layout
2801 Ok(a_layout == b_layout)
2804 #[allow(rustc::usage_of_ty_tykind)]
2805 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2806 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2809 ensure_sufficient_stack(|| {
2810 match (a_kind, b_kind) {
2811 (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2812 let a = a.subst(cx.tcx, a_substs);
2813 let b = b.subst(cx.tcx, b_substs);
2814 debug!("Comparing {:?} and {:?}", a, b);
2816 // We can immediately rule out these types as structurally same if
2817 // their layouts differ.
2818 match compare_layouts(a, b) {
2819 Ok(false) => return false,
2820 _ => (), // otherwise, continue onto the full, fields comparison
2823 // Grab a flattened representation of all fields.
2824 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2825 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2827 // Perform a structural comparison for each field.
2830 |&ty::FieldDef { did: a_did, .. },
2831 &ty::FieldDef { did: b_did, .. }| {
2832 structurally_same_type_impl(
2842 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2843 // For arrays, we also check the constness of the type.
2844 a_const.val == b_const.val
2845 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2847 (Slice(a_ty), Slice(b_ty)) => {
2848 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2850 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2851 a_tymut.mutbl == b_tymut.mutbl
2852 && structurally_same_type_impl(
2860 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2861 // For structural sameness, we don't need the region to be same.
2863 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2865 (FnDef(..), FnDef(..)) => {
2866 let a_poly_sig = a.fn_sig(tcx);
2867 let b_poly_sig = b.fn_sig(tcx);
2869 // As we don't compare regions, skip_binder is fine.
2870 let a_sig = a_poly_sig.skip_binder();
2871 let b_sig = b_poly_sig.skip_binder();
2873 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2874 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2875 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2876 structurally_same_type_impl(seen_types, cx, a, b, ckind)
2878 && structurally_same_type_impl(
2886 (Tuple(a_substs), Tuple(b_substs)) => {
2887 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2888 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2891 // For these, it's not quite as easy to define structural-sameness quite so easily.
2892 // For the purposes of this lint, take the conservative approach and mark them as
2893 // not structurally same.
2894 (Dynamic(..), Dynamic(..))
2895 | (Error(..), Error(..))
2896 | (Closure(..), Closure(..))
2897 | (Generator(..), Generator(..))
2898 | (GeneratorWitness(..), GeneratorWitness(..))
2899 | (Projection(..), Projection(..))
2900 | (Opaque(..), Opaque(..)) => false,
2902 // These definitely should have been caught above.
2903 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2905 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2906 // enum layout optimisation is being applied.
2907 (Adt(..), other_kind) | (other_kind, Adt(..))
2908 if is_primitive_or_pointer(other_kind) =>
2910 let (primitive, adt) =
2911 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2912 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2915 compare_layouts(a, b).unwrap_or(false)
2918 // Otherwise, just compare the layouts. This may fail to lint for some
2919 // incompatible types, but at the very least, will stop reads into
2920 // uninitialised memory.
2921 _ => compare_layouts(a, b).unwrap_or(false),
2926 let mut seen_types = FxHashSet::default();
2927 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2931 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2933 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2934 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2935 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2936 if let ForeignItemKind::Fn(..) = this_fi.kind {
2938 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2939 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2940 let this_decl_ty = tcx.type_of(this_fi.def_id);
2942 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2943 existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2945 // Check that the declarations match.
2946 if !Self::structurally_same_type(
2950 CItemKind::Declaration,
2952 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2953 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2955 // We want to ensure that we use spans for both decls that include where the
2956 // name was defined, whether that was from the link_name attribute or not.
2957 let get_relevant_span =
2958 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2959 SymbolName::Normal(_) => fi.span,
2960 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2962 // Finally, emit the diagnostic.
2963 tcx.struct_span_lint_hir(
2964 CLASHING_EXTERN_DECLARATIONS,
2966 get_relevant_span(this_fi),
2968 let mut expected_str = DiagnosticStyledString::new();
2969 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2970 let mut found_str = DiagnosticStyledString::new();
2971 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2973 lint.build(&format!(
2974 "`{}` redeclare{} with a different signature",
2976 if orig.get_name() == this_fi.ident.name {
2979 format!("s `{}`", orig.get_name())
2983 get_relevant_span(orig_fi),
2984 &format!("`{}` previously declared here", orig.get_name()),
2987 get_relevant_span(this_fi),
2988 "this signature doesn't match the previous declaration",
2990 .note_expected_found(&"", expected_str, &"", found_str)
3001 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3002 /// which causes [undefined behavior].
3007 /// # #![allow(unused)]
3010 /// let x = &*ptr::null::<i32>();
3011 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3012 /// let x = *(0 as *const i32);
3020 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3021 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3023 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3026 "detects when an null pointer is dereferenced"
3029 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3031 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3032 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3033 /// test if expression is a null ptr
3034 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3036 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3037 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3038 return is_zero(expr) || is_null_ptr(cx, expr);
3041 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3042 rustc_hir::ExprKind::Call(ref path, _) => {
3043 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3044 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3045 return cx.tcx.is_diagnostic_item(sym::ptr_null, def_id)
3046 || cx.tcx.is_diagnostic_item(sym::ptr_null_mut, def_id);
3055 /// test if expression is the literal `0`
3056 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3058 rustc_hir::ExprKind::Lit(ref lit) => {
3059 if let LitKind::Int(a, _) = lit.node {
3068 if let rustc_hir::ExprKind::Unary(ref un_op, ref expr_deref) = expr.kind {
3069 if let rustc_hir::UnOp::Deref = un_op {
3070 if is_null_ptr(cx, expr_deref) {
3071 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3072 let mut err = lint.build("dereferencing a null pointer");
3075 "this code causes undefined behavior when executed",