1 //! Lints in the Rust compiler.
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main compiler.
7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
8 //! Then add code to emit the new lint in the appropriate circumstances.
9 //! You can do that in an existing `LintPass` if it makes sense, or in a
10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
11 //! compiler. Only do the latter if the check can't be written cleanly as a
12 //! `LintPass` (also, note that such lints will need to be defined in
13 //! `rustc_session::lint::builtin`, not here).
15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
18 //! with a `pub fn new()`.
20 //! If you define a new `LateLintPass`, you will also need to add it to the
21 //! `late_lint_methods!` invocation in `lib.rs`.
24 types::{transparent_newtype_field, CItemKind},
25 EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
28 use rustc_ast::tokenstream::{TokenStream, TokenTree};
29 use rustc_ast::visit::{FnCtxt, FnKind};
30 use rustc_ast::{self as ast, *};
31 use rustc_ast_pretty::pprust::{self, expr_to_string};
32 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
33 use rustc_data_structures::stack::ensure_sufficient_stack;
34 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
35 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
36 use rustc_feature::{GateIssue, Stability};
38 use rustc_hir::def::{DefKind, Res};
39 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
40 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
41 use rustc_hir::{HirId, Node};
42 use rustc_index::vec::Idx;
43 use rustc_middle::lint::LintDiagnosticBuilder;
44 use rustc_middle::ty::print::with_no_trimmed_paths;
45 use rustc_middle::ty::subst::{GenericArgKind, Subst};
46 use rustc_middle::ty::Instance;
47 use rustc_middle::ty::{self, layout::LayoutError, Ty, TyCtxt};
48 use rustc_session::lint::FutureIncompatibilityReason;
49 use rustc_session::Session;
50 use rustc_span::edition::Edition;
51 use rustc_span::source_map::Spanned;
52 use rustc_span::symbol::{kw, sym, Ident, Symbol};
53 use rustc_span::{BytePos, Span};
54 use rustc_target::abi::{LayoutOf, VariantIdx};
55 use rustc_trait_selection::traits::misc::can_type_implement_copy;
57 use crate::nonstandard_style::{method_context, MethodLateContext};
60 use tracing::{debug, trace};
62 // hardwired lints from librustc_middle
63 pub use rustc_session::lint::builtin::*;
66 /// The `while_true` lint detects `while true { }`.
80 /// `while true` should be replaced with `loop`. A `loop` expression is
81 /// the preferred way to write an infinite loop because it more directly
82 /// expresses the intent of the loop.
85 "suggest using `loop { }` instead of `while true { }`"
88 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
90 /// Traverse through any amount of parenthesis and return the first non-parens expression.
91 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
92 while let ast::ExprKind::Paren(sub) = &expr.kind {
98 impl EarlyLintPass for WhileTrue {
99 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
100 if let ast::ExprKind::While(cond, _, label) = &e.kind {
101 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
102 if let ast::LitKind::Bool(true) = lit.kind {
103 if !lit.span.from_expansion() {
104 let msg = "denote infinite loops with `loop { ... }`";
105 let condition_span = e.span.with_hi(cond.span.hi());
106 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
108 .span_suggestion_short(
113 label.map_or_else(String::new, |label| format!(
118 Applicability::MachineApplicable,
130 /// The `box_pointers` lints use of the Box type.
134 /// ```rust,compile_fail
135 /// #![deny(box_pointers)]
145 /// This lint is mostly historical, and not particularly useful. `Box<T>`
146 /// used to be built into the language, and the only way to do heap
147 /// allocation. Today's Rust can call into other allocators, etc.
150 "use of owned (Box type) heap memory"
153 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
156 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
157 for leaf in ty.walk() {
158 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
159 if leaf_ty.is_box() {
160 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
161 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
169 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
170 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
172 hir::ItemKind::Fn(..)
173 | hir::ItemKind::TyAlias(..)
174 | hir::ItemKind::Enum(..)
175 | hir::ItemKind::Struct(..)
176 | hir::ItemKind::Union(..) => {
177 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
182 // If it's a struct, we also have to check the fields' types
184 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
185 for struct_field in struct_def.fields() {
186 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
187 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
194 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
195 let ty = cx.typeck_results().node_type(e.hir_id);
196 self.check_heap_type(cx, e.span, ty);
201 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
202 /// instead of `Struct { x }` in a pattern.
220 /// Point { x: x, y: y } => (),
229 /// The preferred style is to avoid the repetition of specifying both the
230 /// field name and the binding name if both identifiers are the same.
231 NON_SHORTHAND_FIELD_PATTERNS,
233 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
236 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
238 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
239 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
240 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
245 .expect("struct pattern type is not an ADT")
246 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
247 for fieldpat in field_pats {
248 if fieldpat.is_shorthand {
251 if fieldpat.span.from_expansion() {
252 // Don't lint if this is a macro expansion: macro authors
253 // shouldn't have to worry about this kind of style issue
257 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
258 if cx.tcx.find_field_index(ident, &variant)
259 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
261 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
263 .build(&format!("the `{}:` in this pattern is redundant", ident));
264 let binding = match binding_annot {
265 hir::BindingAnnotation::Unannotated => None,
266 hir::BindingAnnotation::Mutable => Some("mut"),
267 hir::BindingAnnotation::Ref => Some("ref"),
268 hir::BindingAnnotation::RefMut => Some("ref mut"),
270 let ident = if let Some(binding) = binding {
271 format!("{} {}", binding, ident)
277 "use shorthand field pattern",
279 Applicability::MachineApplicable,
291 /// The `unsafe_code` lint catches usage of `unsafe` code.
295 /// ```rust,compile_fail
296 /// #![deny(unsafe_code)]
308 /// This lint is intended to restrict the usage of `unsafe`, which can be
309 /// difficult to use correctly.
312 "usage of `unsafe` code"
315 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
320 cx: &EarlyContext<'_>,
322 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
324 // This comes from a macro that has `#[allow_internal_unsafe]`.
325 if span.allows_unsafe() {
329 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
332 fn report_overriden_symbol_name(&self, cx: &EarlyContext<'_>, span: Span, msg: &str) {
333 self.report_unsafe(cx, span, |lint| {
336 "the linker's behavior with multiple libraries exporting duplicate symbol \
337 names is undefined and Rust cannot provide guarantees when you manually \
345 impl EarlyLintPass for UnsafeCode {
346 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
347 if cx.sess().check_name(attr, sym::allow_internal_unsafe) {
348 self.report_unsafe(cx, attr.span, |lint| {
350 "`allow_internal_unsafe` allows defining \
351 macros using unsafe without triggering \
352 the `unsafe_code` lint at their call site",
359 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
360 if let ast::ExprKind::Block(ref blk, _) = e.kind {
361 // Don't warn about generated blocks; that'll just pollute the output.
362 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
363 self.report_unsafe(cx, blk.span, |lint| {
364 lint.build("usage of an `unsafe` block").emit()
370 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
372 ast::ItemKind::Trait(box ast::TraitKind(_, ast::Unsafe::Yes(_), ..)) => self
373 .report_unsafe(cx, it.span, |lint| {
374 lint.build("declaration of an `unsafe` trait").emit()
377 ast::ItemKind::Impl(box ast::ImplKind { unsafety: ast::Unsafe::Yes(_), .. }) => self
378 .report_unsafe(cx, it.span, |lint| {
379 lint.build("implementation of an `unsafe` trait").emit()
382 ast::ItemKind::Fn(..) => {
383 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
384 self.report_overriden_symbol_name(
387 "declaration of a `no_mangle` function",
390 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
391 self.report_overriden_symbol_name(
394 "declaration of a function with `export_name`",
399 ast::ItemKind::Static(..) => {
400 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
401 self.report_overriden_symbol_name(
404 "declaration of a `no_mangle` static",
407 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
408 self.report_overriden_symbol_name(
411 "declaration of a static with `export_name`",
420 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
424 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
429 let msg = match ctxt {
430 FnCtxt::Foreign => return,
431 FnCtxt::Free => "declaration of an `unsafe` function",
432 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
433 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
435 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
441 /// The `missing_docs` lint detects missing documentation for public items.
445 /// ```rust,compile_fail
446 /// #![deny(missing_docs)]
454 /// This lint is intended to ensure that a library is well-documented.
455 /// Items without documentation can be difficult for users to understand
456 /// how to use properly.
458 /// This lint is "allow" by default because it can be noisy, and not all
459 /// projects may want to enforce everything to be documented.
462 "detects missing documentation for public members",
463 report_in_external_macro
466 pub struct MissingDoc {
467 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
468 doc_hidden_stack: Vec<bool>,
470 /// Private traits or trait items that leaked through. Don't check their methods.
471 private_traits: FxHashSet<hir::HirId>,
474 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
476 fn has_doc(sess: &Session, attr: &ast::Attribute) -> bool {
477 if attr.is_doc_comment() {
481 if !sess.check_name(attr, sym::doc) {
485 if attr.value_str().is_some() {
489 if let Some(list) = attr.meta_item_list() {
491 if meta.has_name(sym::hidden) {
501 pub fn new() -> MissingDoc {
502 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
505 fn doc_hidden(&self) -> bool {
506 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
509 fn check_missing_docs_attrs(
511 cx: &LateContext<'_>,
514 article: &'static str,
517 // If we're building a test harness, then warning about
518 // documentation is probably not really relevant right now.
519 if cx.sess().opts.test {
523 // `#[doc(hidden)]` disables missing_docs check.
524 if self.doc_hidden() {
528 // Only check publicly-visible items, using the result from the privacy pass.
529 // It's an option so the crate root can also use this function (it doesn't
531 if def_id != CRATE_DEF_ID {
532 if !cx.access_levels.is_exported(def_id) {
537 let attrs = cx.tcx.get_attrs(def_id.to_def_id());
538 let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
542 cx.tcx.sess.source_map().guess_head_span(sp),
544 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
551 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
552 fn enter_lint_attrs(&mut self, cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
553 let doc_hidden = self.doc_hidden()
554 || attrs.iter().any(|attr| {
555 cx.sess().check_name(attr, sym::doc)
556 && match attr.meta_item_list() {
558 Some(l) => attr::list_contains_name(&l, sym::hidden),
561 self.doc_hidden_stack.push(doc_hidden);
564 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
565 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
568 fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
569 self.check_missing_docs_attrs(cx, CRATE_DEF_ID, krate.module().inner, "the", "crate");
571 for macro_def in krate.exported_macros() {
572 // Non exported macros should be skipped, since `missing_docs` only
573 // applies to externally visible items.
574 if !cx.access_levels.is_exported(macro_def.def_id) {
578 let attrs = cx.tcx.hir().attrs(macro_def.hir_id());
579 let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
583 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
584 |lint| lint.build("missing documentation for macro").emit(),
590 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
592 hir::ItemKind::Trait(.., trait_item_refs) => {
593 // Issue #11592: traits are always considered exported, even when private.
594 if let hir::VisibilityKind::Inherited = it.vis.node {
595 self.private_traits.insert(it.hir_id());
596 for trait_item_ref in trait_item_refs {
597 self.private_traits.insert(trait_item_ref.id.hir_id());
602 hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref trait_ref), items, .. }) => {
603 // If the trait is private, add the impl items to `private_traits` so they don't get
604 // reported for missing docs.
605 let real_trait = trait_ref.path.res.def_id();
606 if let Some(def_id) = real_trait.as_local() {
607 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
608 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
609 if let hir::VisibilityKind::Inherited = item.vis.node {
610 for impl_item_ref in items {
611 self.private_traits.insert(impl_item_ref.id.hir_id());
619 hir::ItemKind::TyAlias(..)
620 | hir::ItemKind::Fn(..)
621 | hir::ItemKind::Mod(..)
622 | hir::ItemKind::Enum(..)
623 | hir::ItemKind::Struct(..)
624 | hir::ItemKind::Union(..)
625 | hir::ItemKind::Const(..)
626 | hir::ItemKind::Static(..) => {}
631 let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
633 self.check_missing_docs_attrs(cx, it.def_id, it.span, article, desc);
636 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
637 if self.private_traits.contains(&trait_item.hir_id()) {
641 let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
643 self.check_missing_docs_attrs(cx, trait_item.def_id, trait_item.span, article, desc);
646 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
647 // If the method is an impl for a trait, don't doc.
648 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
652 let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
653 self.check_missing_docs_attrs(cx, impl_item.def_id, impl_item.span, article, desc);
656 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
657 let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
658 self.check_missing_docs_attrs(cx, foreign_item.def_id, foreign_item.span, article, desc);
661 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
662 if !sf.is_positional() {
663 let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
664 self.check_missing_docs_attrs(cx, def_id, sf.span, "a", "struct field")
668 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
669 self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), v.span, "a", "variant");
674 /// The `missing_copy_implementations` lint detects potentially-forgotten
675 /// implementations of [`Copy`].
677 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
681 /// ```rust,compile_fail
682 /// #![deny(missing_copy_implementations)]
693 /// Historically (before 1.0), types were automatically marked as `Copy`
694 /// if possible. This was changed so that it required an explicit opt-in
695 /// by implementing the `Copy` trait. As part of this change, a lint was
696 /// added to alert if a copyable type was not marked `Copy`.
698 /// This lint is "allow" by default because this code isn't bad; it is
699 /// common to write newtypes like this specifically so that a `Copy` type
700 /// is no longer `Copy`. `Copy` types can result in unintended copies of
701 /// large data which can impact performance.
702 pub MISSING_COPY_IMPLEMENTATIONS,
704 "detects potentially-forgotten implementations of `Copy`"
707 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
709 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
710 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
711 if !cx.access_levels.is_reachable(item.def_id) {
714 let (def, ty) = match item.kind {
715 hir::ItemKind::Struct(_, ref ast_generics) => {
716 if !ast_generics.params.is_empty() {
719 let def = cx.tcx.adt_def(item.def_id);
720 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
722 hir::ItemKind::Union(_, ref ast_generics) => {
723 if !ast_generics.params.is_empty() {
726 let def = cx.tcx.adt_def(item.def_id);
727 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
729 hir::ItemKind::Enum(_, ref ast_generics) => {
730 if !ast_generics.params.is_empty() {
733 let def = cx.tcx.adt_def(item.def_id);
734 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
738 if def.has_dtor(cx.tcx) {
741 let param_env = ty::ParamEnv::empty();
742 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
745 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
746 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
748 "type could implement `Copy`; consider adding `impl \
758 /// The `missing_debug_implementations` lint detects missing
759 /// implementations of [`fmt::Debug`].
761 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
765 /// ```rust,compile_fail
766 /// #![deny(missing_debug_implementations)]
775 /// Having a `Debug` implementation on all types can assist with
776 /// debugging, as it provides a convenient way to format and display a
777 /// value. Using the `#[derive(Debug)]` attribute will automatically
778 /// generate a typical implementation, or a custom implementation can be
779 /// added by manually implementing the `Debug` trait.
781 /// This lint is "allow" by default because adding `Debug` to all types can
782 /// have a negative impact on compile time and code size. It also requires
783 /// boilerplate to be added to every type, which can be an impediment.
784 MISSING_DEBUG_IMPLEMENTATIONS,
786 "detects missing implementations of Debug"
790 pub struct MissingDebugImplementations {
791 impling_types: Option<LocalDefIdSet>,
794 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
796 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
797 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
798 if !cx.access_levels.is_reachable(item.def_id) {
803 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
807 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
808 Some(debug) => debug,
812 if self.impling_types.is_none() {
813 let mut impls = LocalDefIdSet::default();
814 cx.tcx.for_each_impl(debug, |d| {
815 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
816 if let Some(def_id) = ty_def.did.as_local() {
817 impls.insert(def_id);
822 self.impling_types = Some(impls);
823 debug!("{:?}", self.impling_types);
826 if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
827 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
829 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
830 or a manual implementation",
831 cx.tcx.def_path_str(debug)
840 /// The `anonymous_parameters` lint detects anonymous parameters in trait
845 /// ```rust,edition2015,compile_fail
846 /// #![deny(anonymous_parameters)]
858 /// This syntax is mostly a historical accident, and can be worked around
859 /// quite easily by adding an `_` pattern or a descriptive identifier:
863 /// fn foo(_: usize);
867 /// This syntax is now a hard error in the 2018 edition. In the 2015
868 /// edition, this lint is "warn" by default. This lint
869 /// enables the [`cargo fix`] tool with the `--edition` flag to
870 /// automatically transition old code from the 2015 edition to 2018. The
871 /// tool will run this lint and automatically apply the
872 /// suggested fix from the compiler (which is to add `_` to each
873 /// parameter). This provides a completely automated way to update old
874 /// code for a new edition. See [issue #41686] for more details.
876 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
877 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
878 pub ANONYMOUS_PARAMETERS,
880 "detects anonymous parameters",
881 @future_incompatible = FutureIncompatibleInfo {
882 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
883 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
888 /// Checks for use of anonymous parameters (RFC 1685).
889 AnonymousParameters => [ANONYMOUS_PARAMETERS]
892 impl EarlyLintPass for AnonymousParameters {
893 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
894 if cx.sess.edition() != Edition::Edition2015 {
895 // This is a hard error in future editions; avoid linting and erroring
898 if let ast::AssocItemKind::Fn(box FnKind(_, ref sig, _, _)) = it.kind {
899 for arg in sig.decl.inputs.iter() {
900 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
901 if ident.name == kw::Empty {
902 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
903 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
905 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
906 (snip.as_str(), Applicability::MachineApplicable)
908 ("<type>", Applicability::HasPlaceholders)
912 "anonymous parameters are deprecated and will be \
913 removed in the next edition.",
917 "try naming the parameter or explicitly \
919 format!("_: {}", ty_snip),
931 /// Check for use of attributes which have been deprecated.
933 pub struct DeprecatedAttr {
934 // This is not free to compute, so we want to keep it around, rather than
935 // compute it for every attribute.
936 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
939 impl_lint_pass!(DeprecatedAttr => []);
941 impl DeprecatedAttr {
942 pub fn new() -> DeprecatedAttr {
943 DeprecatedAttr { depr_attrs: deprecated_attributes() }
947 fn lint_deprecated_attr(
948 cx: &EarlyContext<'_>,
949 attr: &ast::Attribute,
951 suggestion: Option<&str>,
953 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
955 .span_suggestion_short(
957 suggestion.unwrap_or("remove this attribute"),
959 Applicability::MachineApplicable,
965 impl EarlyLintPass for DeprecatedAttr {
966 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
967 for &&(n, _, _, ref g) in &self.depr_attrs {
968 if attr.ident().map(|ident| ident.name) == Some(n) {
969 if let &AttributeGate::Gated(
970 Stability::Deprecated(link, suggestion),
977 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
978 lint_deprecated_attr(cx, attr, &msg, suggestion);
983 if cx.sess().check_name(attr, sym::no_start) || cx.sess().check_name(attr, sym::crate_id) {
984 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
985 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
986 lint_deprecated_attr(cx, attr, &msg, None);
991 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
992 use rustc_ast::token::CommentKind;
994 let mut attrs = attrs.iter().peekable();
996 // Accumulate a single span for sugared doc comments.
997 let mut sugared_span: Option<Span> = None;
999 while let Some(attr) = attrs.next() {
1000 let is_doc_comment = attr.is_doc_comment();
1003 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1006 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1010 let span = sugared_span.take().unwrap_or(attr.span);
1012 if is_doc_comment || cx.sess().check_name(attr, sym::doc) {
1013 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1014 let mut err = lint.build("unused doc comment");
1017 format!("rustdoc does not generate documentation for {}", node_kind),
1020 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1021 err.help("use `//` for a plain comment");
1023 AttrKind::DocComment(CommentKind::Block, _) => {
1024 err.help("use `/* */` for a plain comment");
1033 impl EarlyLintPass for UnusedDocComment {
1034 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1035 let kind = match stmt.kind {
1036 ast::StmtKind::Local(..) => "statements",
1037 // Disabled pending discussion in #78306
1038 ast::StmtKind::Item(..) => return,
1039 // expressions will be reported by `check_expr`.
1040 ast::StmtKind::Empty
1041 | ast::StmtKind::Semi(_)
1042 | ast::StmtKind::Expr(_)
1043 | ast::StmtKind::MacCall(_) => return,
1046 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1049 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1050 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1051 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1054 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1055 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1060 /// The `no_mangle_const_items` lint detects any `const` items with the
1061 /// [`no_mangle` attribute].
1063 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1067 /// ```rust,compile_fail
1069 /// const FOO: i32 = 5;
1076 /// Constants do not have their symbols exported, and therefore, this
1077 /// probably means you meant to use a [`static`], not a [`const`].
1079 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1080 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1081 NO_MANGLE_CONST_ITEMS,
1083 "const items will not have their symbols exported"
1087 /// The `no_mangle_generic_items` lint detects generic items that must be
1094 /// fn foo<T>(t: T) {
1103 /// A function with generics must have its symbol mangled to accommodate
1104 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1105 /// this situation, and should be removed.
1107 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1108 NO_MANGLE_GENERIC_ITEMS,
1110 "generic items must be mangled"
1113 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1115 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1116 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1117 let attrs = cx.tcx.hir().attrs(it.hir_id());
1119 hir::ItemKind::Fn(.., ref generics, _) => {
1120 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1121 for param in generics.params {
1123 GenericParamKind::Lifetime { .. } => {}
1124 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1125 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
1127 "functions generic over types or consts must be mangled",
1129 .span_suggestion_short(
1130 no_mangle_attr.span,
1131 "remove this attribute",
1133 // Use of `#[no_mangle]` suggests FFI intent; correct
1134 // fix may be to monomorphize source by hand
1135 Applicability::MaybeIncorrect,
1145 hir::ItemKind::Const(..) => {
1146 if cx.sess().contains_name(attrs, sym::no_mangle) {
1147 // Const items do not refer to a particular location in memory, and therefore
1148 // don't have anything to attach a symbol to
1149 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1150 let msg = "const items should never be `#[no_mangle]`";
1151 let mut err = lint.build(msg);
1153 // account for "pub const" (#45562)
1158 .span_to_snippet(it.span)
1159 .map(|snippet| snippet.find("const").unwrap_or(0))
1160 .unwrap_or(0) as u32;
1161 // `const` is 5 chars
1162 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1163 err.span_suggestion(
1165 "try a static value",
1166 "pub static".to_owned(),
1167 Applicability::MachineApplicable,
1179 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1180 /// T` because it is [undefined behavior].
1182 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1186 /// ```rust,compile_fail
1188 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1196 /// Certain assumptions are made about aliasing of data, and this transmute
1197 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1199 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1202 "mutating transmuted &mut T from &T may cause undefined behavior"
1205 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1207 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1208 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1209 use rustc_target::spec::abi::Abi::RustIntrinsic;
1210 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1211 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1213 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1214 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1215 consider instead using an UnsafeCell";
1216 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
1220 fn get_transmute_from_to<'tcx>(
1221 cx: &LateContext<'tcx>,
1222 expr: &hir::Expr<'_>,
1223 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1224 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1225 cx.qpath_res(qpath, expr.hir_id)
1229 if let Res::Def(DefKind::Fn, did) = def {
1230 if !def_id_is_transmute(cx, did) {
1233 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1234 let from = sig.inputs().skip_binder()[0];
1235 let to = sig.output().skip_binder();
1236 return Some((from, to));
1241 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1242 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
1243 && cx.tcx.item_name(def_id) == sym::transmute
1249 /// The `unstable_features` is deprecated and should no longer be used.
1252 "enabling unstable features (deprecated. do not use)"
1256 /// Forbids using the `#[feature(...)]` attribute
1257 UnstableFeatures => [UNSTABLE_FEATURES]
1260 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1261 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1262 if cx.sess().check_name(attr, sym::feature) {
1263 if let Some(items) = attr.meta_item_list() {
1265 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1266 lint.build("unstable feature").emit()
1275 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1280 /// ```rust,compile_fail
1281 /// #![deny(unreachable_pub)]
1293 /// A bare `pub` visibility may be misleading if the item is not actually
1294 /// publicly exported from the crate. The `pub(crate)` visibility is
1295 /// recommended to be used instead, which more clearly expresses the intent
1296 /// that the item is only visible within its own crate.
1298 /// This lint is "allow" by default because it will trigger for a large
1299 /// amount existing Rust code, and has some false-positives. Eventually it
1300 /// is desired for this to become warn-by-default.
1301 pub UNREACHABLE_PUB,
1303 "`pub` items not reachable from crate root"
1307 /// Lint for items marked `pub` that aren't reachable from other crates.
1308 UnreachablePub => [UNREACHABLE_PUB]
1311 impl UnreachablePub {
1314 cx: &LateContext<'_>,
1317 vis: &hir::Visibility<'_>,
1321 let mut applicability = Applicability::MachineApplicable;
1323 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(def_id) => {
1324 if span.from_expansion() {
1325 applicability = Applicability::MaybeIncorrect;
1327 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1328 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1329 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1330 let replacement = if cx.tcx.features().crate_visibility_modifier {
1337 err.span_suggestion(
1339 "consider restricting its visibility",
1344 err.help("or consider exporting it for use by other crates");
1354 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1355 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1356 self.perform_lint(cx, "item", item.def_id, &item.vis, item.span, true);
1359 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1363 foreign_item.def_id,
1370 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1371 let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1372 self.perform_lint(cx, "field", def_id, &field.vis, field.span, false);
1375 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1376 self.perform_lint(cx, "item", impl_item.def_id, &impl_item.vis, impl_item.span, false);
1381 /// The `type_alias_bounds` lint detects bounds in type aliases.
1386 /// type SendVec<T: Send> = Vec<T>;
1393 /// The trait bounds in a type alias are currently ignored, and should not
1394 /// be included to avoid confusion. This was previously allowed
1395 /// unintentionally; this may become a hard error in the future.
1398 "bounds in type aliases are not enforced"
1402 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1403 /// They are relevant when using associated types, but otherwise neither checked
1404 /// at definition site nor enforced at use site.
1405 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1408 impl TypeAliasBounds {
1409 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1411 hir::QPath::TypeRelative(ref ty, _) => {
1412 // If this is a type variable, we found a `T::Assoc`.
1414 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1415 matches!(path.res, Res::Def(DefKind::TyParam, _))
1420 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1424 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1425 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1426 // bound. Let's see if this type does that.
1428 // We use a HIR visitor to walk the type.
1429 use rustc_hir::intravisit::{self, Visitor};
1430 struct WalkAssocTypes<'a, 'db> {
1431 err: &'a mut DiagnosticBuilder<'db>,
1433 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1434 type Map = intravisit::ErasedMap<'v>;
1436 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1437 intravisit::NestedVisitorMap::None
1440 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1441 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1444 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1445 associated types in type aliases",
1448 intravisit::walk_qpath(self, qpath, id, span)
1452 // Let's go for a walk!
1453 let mut visitor = WalkAssocTypes { err };
1454 visitor.visit_ty(ty);
1458 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1459 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1460 let (ty, type_alias_generics) = match item.kind {
1461 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1464 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1465 // Bounds are respected for `type X = impl Trait`
1468 let mut suggested_changing_assoc_types = false;
1469 // There must not be a where clause
1470 if !type_alias_generics.where_clause.predicates.is_empty() {
1474 let mut err = lint.build("where clauses are not enforced in type aliases");
1475 let spans: Vec<_> = type_alias_generics
1479 .map(|pred| pred.span())
1481 err.set_span(spans);
1482 err.span_suggestion(
1483 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1484 "the clause will not be checked when the type alias is used, and should be removed",
1486 Applicability::MachineApplicable,
1488 if !suggested_changing_assoc_types {
1489 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1490 suggested_changing_assoc_types = true;
1496 // The parameters must not have bounds
1497 for param in type_alias_generics.params.iter() {
1498 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1499 let suggestion = spans
1502 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1503 (start.to(*sp), String::new())
1506 if !spans.is_empty() {
1507 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1509 lint.build("bounds on generic parameters are not enforced in type aliases");
1510 let msg = "the bound will not be checked when the type alias is used, \
1511 and should be removed";
1512 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1513 if !suggested_changing_assoc_types {
1514 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1515 suggested_changing_assoc_types = true;
1525 /// Lint constants that are erroneous.
1526 /// Without this lint, we might not get any diagnostic if the constant is
1527 /// unused within this crate, even though downstream crates can't use it
1528 /// without producing an error.
1529 UnusedBrokenConst => []
1532 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1533 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1535 hir::ItemKind::Const(_, body_id) => {
1536 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1537 // trigger the query once for all constants since that will already report the errors
1538 // FIXME: Use ensure here
1539 let _ = cx.tcx.const_eval_poly(def_id);
1541 hir::ItemKind::Static(_, _, body_id) => {
1542 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1543 // FIXME: Use ensure here
1544 let _ = cx.tcx.eval_static_initializer(def_id);
1552 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1553 /// any type parameters.
1558 /// #![feature(trivial_bounds)]
1559 /// pub struct A where i32: Copy;
1566 /// Usually you would not write a trait bound that you know is always
1567 /// true, or never true. However, when using macros, the macro may not
1568 /// know whether or not the constraint would hold or not at the time when
1569 /// generating the code. Currently, the compiler does not alert you if the
1570 /// constraint is always true, and generates an error if it is never true.
1571 /// The `trivial_bounds` feature changes this to be a warning in both
1572 /// cases, giving macros more freedom and flexibility to generate code,
1573 /// while still providing a signal when writing non-macro code that
1574 /// something is amiss.
1576 /// See [RFC 2056] for more details. This feature is currently only
1577 /// available on the nightly channel, see [tracking issue #48214].
1579 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1580 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1583 "these bounds don't depend on an type parameters"
1587 /// Lint for trait and lifetime bounds that don't depend on type parameters
1588 /// which either do nothing, or stop the item from being used.
1589 TrivialConstraints => [TRIVIAL_BOUNDS]
1592 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1593 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1594 use rustc_middle::ty::fold::TypeFoldable;
1595 use rustc_middle::ty::PredicateKind::*;
1597 if cx.tcx.features().trivial_bounds {
1598 let predicates = cx.tcx.predicates_of(item.def_id);
1599 for &(predicate, span) in predicates.predicates {
1600 let predicate_kind_name = match predicate.kind().skip_binder() {
1601 Trait(..) => "Trait",
1603 RegionOutlives(..) => "Lifetime",
1605 // Ignore projections, as they can only be global
1606 // if the trait bound is global
1608 // Ignore bounds that a user can't type
1613 ConstEvaluatable(..) |
1615 TypeWellFormedFromEnv(..) => continue,
1617 if predicate.is_global() {
1618 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1619 lint.build(&format!(
1620 "{} bound {} does not depend on any type \
1621 or lifetime parameters",
1622 predicate_kind_name, predicate
1633 /// Does nothing as a lint pass, but registers some `Lint`s
1634 /// which are used by other parts of the compiler.
1638 NON_SHORTHAND_FIELD_PATTERNS,
1641 MISSING_COPY_IMPLEMENTATIONS,
1642 MISSING_DEBUG_IMPLEMENTATIONS,
1643 ANONYMOUS_PARAMETERS,
1644 UNUSED_DOC_COMMENTS,
1645 NO_MANGLE_CONST_ITEMS,
1646 NO_MANGLE_GENERIC_ITEMS,
1656 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1657 /// pattern], which is deprecated.
1659 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1675 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1676 /// confusion with the [`..` range expression]. Use the new form instead.
1678 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1679 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1681 "`...` range patterns are deprecated",
1682 @future_incompatible = FutureIncompatibleInfo {
1683 reference: "issue #80165 <https://github.com/rust-lang/rust/issues/80165>",
1684 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1689 pub struct EllipsisInclusiveRangePatterns {
1690 /// If `Some(_)`, suppress all subsequent pattern
1691 /// warnings for better diagnostics.
1692 node_id: Option<ast::NodeId>,
1695 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1697 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1698 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1699 if self.node_id.is_some() {
1700 // Don't recursively warn about patterns inside range endpoints.
1704 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1706 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1707 /// corresponding to the ellipsis.
1708 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1713 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1714 ) => Some((a.as_deref(), b, *span)),
1719 let (parenthesise, endpoints) = match &pat.kind {
1720 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1721 _ => (false, matches_ellipsis_pat(pat)),
1724 if let Some((start, end, join)) = endpoints {
1725 let msg = "`...` range patterns are deprecated";
1726 let suggestion = "use `..=` for an inclusive range";
1728 self.node_id = Some(pat.id);
1729 let end = expr_to_string(&end);
1730 let replace = match start {
1731 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1732 None => format!("&(..={})", end),
1734 if join.edition() >= Edition::Edition2021 {
1736 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1737 err.span_suggestion(
1741 Applicability::MachineApplicable,
1745 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1751 Applicability::MachineApplicable,
1757 let replace = "..=".to_owned();
1758 if join.edition() >= Edition::Edition2021 {
1760 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1761 err.span_suggestion_short(
1765 Applicability::MachineApplicable,
1769 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1771 .span_suggestion_short(
1775 Applicability::MachineApplicable,
1784 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1785 if let Some(node_id) = self.node_id {
1786 if pat.id == node_id {
1794 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1795 /// that are not able to be run by the test harness because they are in a
1796 /// position where they are not nameable.
1798 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1806 /// // This test will not fail because it does not run.
1807 /// assert_eq!(1, 2);
1816 /// In order for the test harness to run a test, the test function must be
1817 /// located in a position where it can be accessed from the crate root.
1818 /// This generally means it must be defined in a module, and not anywhere
1819 /// else such as inside another function. The compiler previously allowed
1820 /// this without an error, so a lint was added as an alert that a test is
1821 /// not being used. Whether or not this should be allowed has not yet been
1822 /// decided, see [RFC 2471] and [issue #36629].
1824 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1825 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1826 UNNAMEABLE_TEST_ITEMS,
1828 "detects an item that cannot be named being marked as `#[test_case]`",
1829 report_in_external_macro
1832 pub struct UnnameableTestItems {
1833 boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1834 items_nameable: bool,
1837 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1839 impl UnnameableTestItems {
1840 pub fn new() -> Self {
1841 Self { boundary: None, items_nameable: true }
1845 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1846 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1847 if self.items_nameable {
1848 if let hir::ItemKind::Mod(..) = it.kind {
1850 self.items_nameable = false;
1851 self.boundary = Some(it.def_id);
1856 let attrs = cx.tcx.hir().attrs(it.hir_id());
1857 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1858 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1859 lint.build("cannot test inner items").emit()
1864 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1865 if !self.items_nameable && self.boundary == Some(it.def_id) {
1866 self.items_nameable = true;
1872 /// The `keyword_idents` lint detects edition keywords being used as an
1877 /// ```rust,edition2015,compile_fail
1878 /// #![deny(keyword_idents)]
1887 /// Rust [editions] allow the language to evolve without breaking
1888 /// backwards compatibility. This lint catches code that uses new keywords
1889 /// that are added to the language that are used as identifiers (such as a
1890 /// variable name, function name, etc.). If you switch the compiler to a
1891 /// new edition without updating the code, then it will fail to compile if
1892 /// you are using a new keyword as an identifier.
1894 /// You can manually change the identifiers to a non-keyword, or use a
1895 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1897 /// This lint solves the problem automatically. It is "allow" by default
1898 /// because the code is perfectly valid in older editions. The [`cargo
1899 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1900 /// and automatically apply the suggested fix from the compiler (which is
1901 /// to use a raw identifier). This provides a completely automated way to
1902 /// update old code for a new edition.
1904 /// [editions]: https://doc.rust-lang.org/edition-guide/
1905 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1906 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1909 "detects edition keywords being used as an identifier",
1910 @future_incompatible = FutureIncompatibleInfo {
1911 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1912 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1917 /// Check for uses of edition keywords used as an identifier.
1918 KeywordIdents => [KEYWORD_IDENTS]
1921 struct UnderMacro(bool);
1923 impl KeywordIdents {
1924 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1925 for tt in tokens.into_trees() {
1927 // Only report non-raw idents.
1928 TokenTree::Token(token) => {
1929 if let Some((ident, false)) = token.ident() {
1930 self.check_ident_token(cx, UnderMacro(true), ident);
1933 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1938 fn check_ident_token(
1940 cx: &EarlyContext<'_>,
1941 UnderMacro(under_macro): UnderMacro,
1944 let next_edition = match cx.sess.edition() {
1945 Edition::Edition2015 => {
1947 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1949 // rust-lang/rust#56327: Conservatively do not
1950 // attempt to report occurrences of `dyn` within
1951 // macro definitions or invocations, because `dyn`
1952 // can legitimately occur as a contextual keyword
1953 // in 2015 code denoting its 2018 meaning, and we
1954 // do not want rustfix to inject bugs into working
1955 // code by rewriting such occurrences.
1957 // But if we see `dyn` outside of a macro, we know
1958 // its precise role in the parsed AST and thus are
1959 // assured this is truly an attempt to use it as
1961 kw::Dyn if !under_macro => Edition::Edition2018,
1967 // There are no new keywords yet for the 2018 edition and beyond.
1971 // Don't lint `r#foo`.
1972 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1976 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1977 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1980 "you can use a raw identifier to stay compatible",
1981 format!("r#{}", ident),
1982 Applicability::MachineApplicable,
1989 impl EarlyLintPass for KeywordIdents {
1990 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1991 self.check_tokens(cx, mac_def.body.inner_tokens());
1993 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1994 self.check_tokens(cx, mac.args.inner_tokens());
1996 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1997 self.check_ident_token(cx, UnderMacro(false), ident);
2001 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2003 impl ExplicitOutlivesRequirements {
2004 fn lifetimes_outliving_lifetime<'tcx>(
2005 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2007 ) -> Vec<ty::Region<'tcx>> {
2010 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2011 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
2012 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2020 fn lifetimes_outliving_type<'tcx>(
2021 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2023 ) -> Vec<ty::Region<'tcx>> {
2026 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2027 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2028 a.is_param(index).then_some(b)
2035 fn collect_outlived_lifetimes<'tcx>(
2037 param: &'tcx hir::GenericParam<'tcx>,
2039 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2040 ty_generics: &'tcx ty::Generics,
2041 ) -> Vec<ty::Region<'tcx>> {
2043 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
2046 hir::GenericParamKind::Lifetime { .. } => {
2047 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
2049 hir::GenericParamKind::Type { .. } => {
2050 Self::lifetimes_outliving_type(inferred_outlives, index)
2052 hir::GenericParamKind::Const { .. } => Vec::new(),
2056 fn collect_outlives_bound_spans<'tcx>(
2059 bounds: &hir::GenericBounds<'_>,
2060 inferred_outlives: &[ty::Region<'tcx>],
2062 ) -> Vec<(usize, Span)> {
2063 use rustc_middle::middle::resolve_lifetime::Region;
2068 .filter_map(|(i, bound)| {
2069 if let hir::GenericBound::Outlives(lifetime) = bound {
2070 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2071 Some(Region::Static) if infer_static => {
2072 inferred_outlives.iter().any(|r| matches!(r, ty::ReStatic))
2074 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2075 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
2079 is_inferred.then_some((i, bound.span()))
2087 fn consolidate_outlives_bound_spans(
2090 bounds: &hir::GenericBounds<'_>,
2091 bound_spans: Vec<(usize, Span)>,
2093 if bounds.is_empty() {
2096 if bound_spans.len() == bounds.len() {
2097 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2098 // If all bounds are inferable, we want to delete the colon, so
2099 // start from just after the parameter (span passed as argument)
2100 vec![lo.to(last_bound_span)]
2102 let mut merged = Vec::new();
2103 let mut last_merged_i = None;
2105 let mut from_start = true;
2106 for (i, bound_span) in bound_spans {
2107 match last_merged_i {
2108 // If the first bound is inferable, our span should also eat the leading `+`.
2110 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2111 last_merged_i = Some(0);
2113 // If consecutive bounds are inferable, merge their spans
2114 Some(h) if i == h + 1 => {
2115 if let Some(tail) = merged.last_mut() {
2116 // Also eat the trailing `+` if the first
2117 // more-than-one bound is inferable
2118 let to_span = if from_start && i < bounds.len() {
2119 bounds[i + 1].span().shrink_to_lo()
2123 *tail = tail.to(to_span);
2124 last_merged_i = Some(i);
2126 bug!("another bound-span visited earlier");
2130 // When we find a non-inferable bound, subsequent inferable bounds
2131 // won't be consecutive from the start (and we'll eat the leading
2132 // `+` rather than the trailing one)
2134 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2135 last_merged_i = Some(i);
2144 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2145 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2146 use rustc_middle::middle::resolve_lifetime::Region;
2148 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
2149 let def_id = item.def_id;
2150 if let hir::ItemKind::Struct(_, ref hir_generics)
2151 | hir::ItemKind::Enum(_, ref hir_generics)
2152 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2154 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2155 if inferred_outlives.is_empty() {
2159 let ty_generics = cx.tcx.generics_of(def_id);
2161 let mut bound_count = 0;
2162 let mut lint_spans = Vec::new();
2164 for param in hir_generics.params {
2165 let has_lifetime_bounds = param
2168 .any(|bound| matches!(bound, hir::GenericBound::Outlives(_)));
2169 if !has_lifetime_bounds {
2173 let relevant_lifetimes =
2174 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
2175 if relevant_lifetimes.is_empty() {
2179 let bound_spans = self.collect_outlives_bound_spans(
2182 &relevant_lifetimes,
2185 bound_count += bound_spans.len();
2186 lint_spans.extend(self.consolidate_outlives_bound_spans(
2187 param.span.shrink_to_hi(),
2193 let mut where_lint_spans = Vec::new();
2194 let mut dropped_predicate_count = 0;
2195 let num_predicates = hir_generics.where_clause.predicates.len();
2196 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
2197 let (relevant_lifetimes, bounds, span) = match where_predicate {
2198 hir::WherePredicate::RegionPredicate(predicate) => {
2199 if let Some(Region::EarlyBound(index, ..)) =
2200 cx.tcx.named_region(predicate.lifetime.hir_id)
2203 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2211 hir::WherePredicate::BoundPredicate(predicate) => {
2212 // FIXME we can also infer bounds on associated types,
2213 // and should check for them here.
2214 match predicate.bounded_ty.kind {
2215 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2216 if let Res::Def(DefKind::TyParam, def_id) = path.res {
2217 let index = ty_generics.param_def_id_to_index[&def_id];
2219 Self::lifetimes_outliving_type(inferred_outlives, index),
2234 if relevant_lifetimes.is_empty() {
2238 let bound_spans = self.collect_outlives_bound_spans(
2241 &relevant_lifetimes,
2244 bound_count += bound_spans.len();
2246 let drop_predicate = bound_spans.len() == bounds.len();
2248 dropped_predicate_count += 1;
2251 // If all the bounds on a predicate were inferable and there are
2252 // further predicates, we want to eat the trailing comma.
2253 if drop_predicate && i + 1 < num_predicates {
2254 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
2255 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2257 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2258 span.shrink_to_lo(),
2265 // If all predicates are inferable, drop the entire clause
2266 // (including the `where`)
2267 if num_predicates > 0 && dropped_predicate_count == num_predicates {
2268 let where_span = hir_generics
2271 .expect("span of (nonempty) where clause should exist");
2272 // Extend the where clause back to the closing `>` of the
2273 // generics, except for tuple struct, which have the `where`
2274 // after the fields of the struct.
2275 let full_where_span =
2276 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2279 hir_generics.span.shrink_to_hi().to(where_span)
2281 lint_spans.push(full_where_span);
2283 lint_spans.extend(where_lint_spans);
2286 if !lint_spans.is_empty() {
2287 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2288 lint.build("outlives requirements can be inferred")
2289 .multipart_suggestion(
2290 if bound_count == 1 {
2293 "remove these bounds"
2297 .map(|span| (span, "".to_owned()))
2298 .collect::<Vec<_>>(),
2299 Applicability::MachineApplicable,
2309 /// The `incomplete_features` lint detects unstable features enabled with
2310 /// the [`feature` attribute] that may function improperly in some or all
2313 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2318 /// #![feature(const_generics)]
2325 /// Although it is encouraged for people to experiment with unstable
2326 /// features, some of them are known to be incomplete or faulty. This lint
2327 /// is a signal that the feature has not yet been finished, and you may
2328 /// experience problems with it.
2329 pub INCOMPLETE_FEATURES,
2331 "incomplete features that may function improperly in some or all cases"
2335 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2336 IncompleteFeatures => [INCOMPLETE_FEATURES]
2339 impl EarlyLintPass for IncompleteFeatures {
2340 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2341 let features = cx.sess.features_untracked();
2343 .declared_lang_features
2345 .map(|(name, span, _)| (name, span))
2346 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2347 .filter(|(&name, _)| features.incomplete(name))
2348 .for_each(|(&name, &span)| {
2349 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2350 let mut builder = lint.build(&format!(
2351 "the feature `{}` is incomplete and may not be safe to use \
2352 and/or cause compiler crashes",
2355 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2356 builder.note(&format!(
2357 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
2358 for more information",
2362 if HAS_MIN_FEATURES.contains(&name) {
2363 builder.help(&format!(
2364 "consider using `min_{}` instead, which is more stable and complete",
2374 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2377 /// The `invalid_value` lint detects creating a value that is not valid,
2378 /// such as a null reference.
2383 /// # #![allow(unused)]
2385 /// let x: &'static i32 = std::mem::zeroed();
2393 /// In some situations the compiler can detect that the code is creating
2394 /// an invalid value, which should be avoided.
2396 /// In particular, this lint will check for improper use of
2397 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2398 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2399 /// lint should provide extra information to indicate what the problem is
2400 /// and a possible solution.
2402 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2403 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2404 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2405 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2406 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2409 "an invalid value is being created (such as a null reference)"
2412 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2414 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2415 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2416 #[derive(Debug, Copy, Clone, PartialEq)]
2422 /// Information about why a type cannot be initialized this way.
2423 /// Contains an error message and optionally a span to point at.
2424 type InitError = (String, Option<Span>);
2426 /// Test if this constant is all-0.
2427 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2428 use hir::ExprKind::*;
2429 use rustc_ast::LitKind::*;
2432 if let Int(i, _) = lit.node {
2438 Tup(tup) => tup.iter().all(is_zero),
2443 /// Determine if this expression is a "dangerous initialization".
2444 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2445 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2446 // Find calls to `mem::{uninitialized,zeroed}` methods.
2447 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2448 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2450 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
2451 return Some(InitKind::Zeroed);
2452 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
2453 return Some(InitKind::Uninit);
2454 } else if cx.tcx.is_diagnostic_item(sym::transmute, def_id) && is_zero(&args[0])
2456 return Some(InitKind::Zeroed);
2459 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
2460 // Find problematic calls to `MaybeUninit::assume_init`.
2461 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2462 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2463 // This is a call to *some* method named `assume_init`.
2464 // See if the `self` parameter is one of the dangerous constructors.
2465 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2466 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2467 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2469 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
2470 return Some(InitKind::Zeroed);
2471 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
2472 return Some(InitKind::Uninit);
2482 /// Test if this enum has several actually "existing" variants.
2483 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2484 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
2485 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2486 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
2487 existing_variants > 1
2490 /// Return `Some` only if we are sure this type does *not*
2491 /// allow zero initialization.
2492 fn ty_find_init_error<'tcx>(
2496 ) -> Option<InitError> {
2497 use rustc_middle::ty::TyKind::*;
2499 // Primitive types that don't like 0 as a value.
2500 Ref(..) => Some(("references must be non-null".to_string(), None)),
2501 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2502 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2503 Never => Some(("the `!` type has no valid value".to_string(), None)),
2504 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2505 // raw ptr to dyn Trait
2507 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2509 // Primitive types with other constraints.
2510 Bool if init == InitKind::Uninit => {
2511 Some(("booleans must be either `true` or `false`".to_string(), None))
2513 Char if init == InitKind::Uninit => {
2514 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2516 // Recurse and checks for some compound types.
2517 Adt(adt_def, substs) if !adt_def.is_union() => {
2518 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2519 use std::ops::Bound;
2520 match tcx.layout_scalar_valid_range(adt_def.did) {
2521 // We exploit here that `layout_scalar_valid_range` will never
2522 // return `Bound::Excluded`. (And we have tests checking that we
2523 // handle the attribute correctly.)
2524 (Bound::Included(lo), _) if lo > 0 => {
2525 return Some((format!("`{}` must be non-null", ty), None));
2527 (Bound::Included(_), _) | (_, Bound::Included(_))
2528 if init == InitKind::Uninit =>
2532 "`{}` must be initialized inside its custom valid range",
2541 match adt_def.variants.len() {
2542 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2544 // Struct, or enum with exactly one variant.
2545 // Proceed recursively, check all fields.
2546 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2547 variant.fields.iter().find_map(|field| {
2548 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2551 // Point to this field, should be helpful for figuring
2552 // out where the source of the error is.
2553 let span = tcx.def_span(field.did);
2556 " (in this {} field)",
2569 // Multi-variant enum.
2571 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2572 let span = tcx.def_span(adt_def.did);
2574 "enums have to be initialized to a variant".to_string(),
2578 // In principle, for zero-initialization we could figure out which variant corresponds
2579 // to tag 0, and check that... but for now we just accept all zero-initializations.
2586 // Proceed recursively, check all fields.
2587 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2589 // Conservative fallback.
2594 if let Some(init) = is_dangerous_init(cx, expr) {
2595 // This conjures an instance of a type out of nothing,
2596 // using zeroed or uninitialized memory.
2597 // We are extremely conservative with what we warn about.
2598 let conjured_ty = cx.typeck_results().expr_ty(expr);
2599 if let Some((msg, span)) =
2600 with_no_trimmed_paths(|| ty_find_init_error(cx.tcx, conjured_ty, init))
2602 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2603 let mut err = lint.build(&format!(
2604 "the type `{}` does not permit {}",
2607 InitKind::Zeroed => "zero-initialization",
2608 InitKind::Uninit => "being left uninitialized",
2611 err.span_label(expr.span, "this code causes undefined behavior when executed");
2614 "help: use `MaybeUninit<T>` instead, \
2615 and only call `assume_init` after initialization is done",
2617 if let Some(span) = span {
2618 err.span_note(span, &msg);
2630 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2631 /// has been declared with the same name but different types.
2651 /// Because two symbols of the same name cannot be resolved to two
2652 /// different functions at link time, and one function cannot possibly
2653 /// have two types, a clashing extern declaration is almost certainly a
2654 /// mistake. Check to make sure that the `extern` definitions are correct
2655 /// and equivalent, and possibly consider unifying them in one location.
2657 /// This lint does not run between crates because a project may have
2658 /// dependencies which both rely on the same extern function, but declare
2659 /// it in a different (but valid) way. For example, they may both declare
2660 /// an opaque type for one or more of the arguments (which would end up
2661 /// distinct types), or use types that are valid conversions in the
2662 /// language the `extern fn` is defined in. In these cases, the compiler
2663 /// can't say that the clashing declaration is incorrect.
2664 pub CLASHING_EXTERN_DECLARATIONS,
2666 "detects when an extern fn has been declared with the same name but different types"
2669 pub struct ClashingExternDeclarations {
2670 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2671 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2672 /// the symbol should be reported as a clashing declaration.
2673 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2674 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2675 seen_decls: FxHashMap<Symbol, HirId>,
2678 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2679 /// just from declaration itself. This is important because we don't want to report clashes on
2680 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2683 /// The name of the symbol + the span of the annotation which introduced the link name.
2685 /// No link name, so just the name of the symbol.
2690 fn get_name(&self) -> Symbol {
2692 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2697 impl ClashingExternDeclarations {
2698 crate fn new() -> Self {
2699 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2701 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2702 /// for the item, return its HirId without updating the set.
2703 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2704 let did = fi.def_id.to_def_id();
2705 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2706 let name = Symbol::intern(tcx.symbol_name(instance).name);
2707 if let Some(&hir_id) = self.seen_decls.get(&name) {
2708 // Avoid updating the map with the new entry when we do find a collision. We want to
2709 // make sure we're always pointing to the first definition as the previous declaration.
2710 // This lets us avoid emitting "knock-on" diagnostics.
2713 self.seen_decls.insert(name, fi.hir_id())
2717 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2718 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2720 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2721 if let Some((overridden_link_name, overridden_link_name_span)) =
2722 tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2723 // FIXME: Instead of searching through the attributes again to get span
2724 // information, we could have codegen_fn_attrs also give span information back for
2725 // where the attribute was defined. However, until this is found to be a
2726 // bottleneck, this does just fine.
2728 overridden_link_name,
2729 tcx.get_attrs(fi.def_id.to_def_id())
2731 .find(|at| tcx.sess.check_name(at, sym::link_name))
2737 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2739 SymbolName::Normal(fi.ident.name)
2743 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2744 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2745 /// with the same members (as the declarations shouldn't clash).
2746 fn structurally_same_type<'tcx>(
2747 cx: &LateContext<'tcx>,
2752 fn structurally_same_type_impl<'tcx>(
2753 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2754 cx: &LateContext<'tcx>,
2759 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2762 // Given a transparent newtype, reach through and grab the inner
2763 // type unless the newtype makes the type non-null.
2764 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2767 if let ty::Adt(def, substs) = *ty.kind() {
2768 let is_transparent = def.subst(tcx, substs).repr.transparent();
2769 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, &def);
2771 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2772 ty, is_transparent, is_non_null
2774 if is_transparent && !is_non_null {
2775 debug_assert!(def.variants.len() == 1);
2776 let v = &def.variants[VariantIdx::new(0)];
2777 ty = transparent_newtype_field(tcx, v)
2779 "single-variant transparent structure with zero-sized field",
2785 debug!("non_transparent_ty -> {:?}", ty);
2790 let a = non_transparent_ty(a);
2791 let b = non_transparent_ty(b);
2793 if !seen_types.insert((a, b)) {
2794 // We've encountered a cycle. There's no point going any further -- the types are
2795 // structurally the same.
2799 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2800 // All nominally-same types are structurally same, too.
2803 // Do a full, depth-first comparison between the two.
2804 use rustc_middle::ty::TyKind::*;
2805 let a_kind = a.kind();
2806 let b_kind = b.kind();
2808 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2809 debug!("compare_layouts({:?}, {:?})", a, b);
2810 let a_layout = &cx.layout_of(a)?.layout.abi;
2811 let b_layout = &cx.layout_of(b)?.layout.abi;
2813 "comparing layouts: {:?} == {:?} = {}",
2816 a_layout == b_layout
2818 Ok(a_layout == b_layout)
2821 #[allow(rustc::usage_of_ty_tykind)]
2822 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2823 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2826 ensure_sufficient_stack(|| {
2827 match (a_kind, b_kind) {
2828 (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2829 let a = a.subst(cx.tcx, a_substs);
2830 let b = b.subst(cx.tcx, b_substs);
2831 debug!("Comparing {:?} and {:?}", a, b);
2833 // We can immediately rule out these types as structurally same if
2834 // their layouts differ.
2835 match compare_layouts(a, b) {
2836 Ok(false) => return false,
2837 _ => (), // otherwise, continue onto the full, fields comparison
2840 // Grab a flattened representation of all fields.
2841 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2842 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2844 // Perform a structural comparison for each field.
2847 |&ty::FieldDef { did: a_did, .. },
2848 &ty::FieldDef { did: b_did, .. }| {
2849 structurally_same_type_impl(
2859 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2860 // For arrays, we also check the constness of the type.
2861 a_const.val == b_const.val
2862 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2864 (Slice(a_ty), Slice(b_ty)) => {
2865 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2867 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2868 a_tymut.mutbl == b_tymut.mutbl
2869 && structurally_same_type_impl(
2877 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2878 // For structural sameness, we don't need the region to be same.
2880 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2882 (FnDef(..), FnDef(..)) => {
2883 let a_poly_sig = a.fn_sig(tcx);
2884 let b_poly_sig = b.fn_sig(tcx);
2886 // As we don't compare regions, skip_binder is fine.
2887 let a_sig = a_poly_sig.skip_binder();
2888 let b_sig = b_poly_sig.skip_binder();
2890 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2891 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2892 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2893 structurally_same_type_impl(seen_types, cx, a, b, ckind)
2895 && structurally_same_type_impl(
2903 (Tuple(a_substs), Tuple(b_substs)) => {
2904 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2905 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2908 // For these, it's not quite as easy to define structural-sameness quite so easily.
2909 // For the purposes of this lint, take the conservative approach and mark them as
2910 // not structurally same.
2911 (Dynamic(..), Dynamic(..))
2912 | (Error(..), Error(..))
2913 | (Closure(..), Closure(..))
2914 | (Generator(..), Generator(..))
2915 | (GeneratorWitness(..), GeneratorWitness(..))
2916 | (Projection(..), Projection(..))
2917 | (Opaque(..), Opaque(..)) => false,
2919 // These definitely should have been caught above.
2920 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2922 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2923 // enum layout optimisation is being applied.
2924 (Adt(..), other_kind) | (other_kind, Adt(..))
2925 if is_primitive_or_pointer(other_kind) =>
2927 let (primitive, adt) =
2928 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2929 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2932 compare_layouts(a, b).unwrap_or(false)
2935 // Otherwise, just compare the layouts. This may fail to lint for some
2936 // incompatible types, but at the very least, will stop reads into
2937 // uninitialised memory.
2938 _ => compare_layouts(a, b).unwrap_or(false),
2943 let mut seen_types = FxHashSet::default();
2944 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2948 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2950 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2951 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2952 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2953 if let ForeignItemKind::Fn(..) = this_fi.kind {
2955 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2956 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2957 let this_decl_ty = tcx.type_of(this_fi.def_id);
2959 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2960 existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
2962 // Check that the declarations match.
2963 if !Self::structurally_same_type(
2967 CItemKind::Declaration,
2969 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2970 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2972 // We want to ensure that we use spans for both decls that include where the
2973 // name was defined, whether that was from the link_name attribute or not.
2974 let get_relevant_span =
2975 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2976 SymbolName::Normal(_) => fi.span,
2977 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2979 // Finally, emit the diagnostic.
2980 tcx.struct_span_lint_hir(
2981 CLASHING_EXTERN_DECLARATIONS,
2983 get_relevant_span(this_fi),
2985 let mut expected_str = DiagnosticStyledString::new();
2986 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2987 let mut found_str = DiagnosticStyledString::new();
2988 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2990 lint.build(&format!(
2991 "`{}` redeclare{} with a different signature",
2993 if orig.get_name() == this_fi.ident.name {
2996 format!("s `{}`", orig.get_name())
3000 get_relevant_span(orig_fi),
3001 &format!("`{}` previously declared here", orig.get_name()),
3004 get_relevant_span(this_fi),
3005 "this signature doesn't match the previous declaration",
3007 .note_expected_found(&"", expected_str, &"", found_str)
3018 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3019 /// which causes [undefined behavior].
3024 /// # #![allow(unused)]
3027 /// let x = &*ptr::null::<i32>();
3028 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3029 /// let x = *(0 as *const i32);
3037 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3038 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3040 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3043 "detects when an null pointer is dereferenced"
3046 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3048 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3049 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3050 /// test if expression is a null ptr
3051 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3053 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3054 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3055 return is_zero(expr) || is_null_ptr(cx, expr);
3058 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3059 rustc_hir::ExprKind::Call(ref path, _) => {
3060 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3061 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3062 return cx.tcx.is_diagnostic_item(sym::ptr_null, def_id)
3063 || cx.tcx.is_diagnostic_item(sym::ptr_null_mut, def_id);
3072 /// test if expression is the literal `0`
3073 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3075 rustc_hir::ExprKind::Lit(ref lit) => {
3076 if let LitKind::Int(a, _) = lit.node {
3085 if let rustc_hir::ExprKind::Unary(ref un_op, ref expr_deref) = expr.kind {
3086 if let rustc_hir::UnOp::Deref = un_op {
3087 if is_null_ptr(cx, expr_deref) {
3088 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3089 let mut err = lint.build("dereferencing a null pointer");
3092 "this code causes undefined behavior when executed",