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,
27 use rustc_ast::attr::{self, HasAttrs};
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;
40 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
41 use rustc_hir::{HirId, HirIdSet, 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::Session;
49 use rustc_span::edition::Edition;
50 use rustc_span::source_map::Spanned;
51 use rustc_span::symbol::{kw, sym, Ident, Symbol};
52 use rustc_span::{BytePos, Span};
53 use rustc_target::abi::{LayoutOf, VariantIdx};
54 use rustc_trait_selection::traits::misc::can_type_implement_copy;
56 use crate::nonstandard_style::{method_context, MethodLateContext};
59 use tracing::{debug, trace};
61 // hardwired lints from librustc_middle
62 pub use rustc_session::lint::builtin::*;
65 /// The `while_true` lint detects `while true { }`.
79 /// `while true` should be replaced with `loop`. A `loop` expression is
80 /// the preferred way to write an infinite loop because it more directly
81 /// expresses the intent of the loop.
84 "suggest using `loop { }` instead of `while true { }`"
87 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
89 /// Traverse through any amount of parenthesis and return the first non-parens expression.
90 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
91 while let ast::ExprKind::Paren(sub) = &expr.kind {
97 impl EarlyLintPass for WhileTrue {
98 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
99 if let ast::ExprKind::While(cond, _, label) = &e.kind {
100 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
101 if let ast::LitKind::Bool(true) = lit.kind {
102 if !lit.span.from_expansion() {
103 let msg = "denote infinite loops with `loop { ... }`";
104 let condition_span = e.span.with_hi(cond.span.hi());
105 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
107 .span_suggestion_short(
112 label.map_or_else(String::new, |label| format!(
117 Applicability::MachineApplicable,
129 /// The `box_pointers` lints use of the Box type.
133 /// ```rust,compile_fail
134 /// #![deny(box_pointers)]
144 /// This lint is mostly historical, and not particularly useful. `Box<T>`
145 /// used to be built into the language, and the only way to do heap
146 /// allocation. Today's Rust can call into other allocators, etc.
149 "use of owned (Box type) heap memory"
152 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
155 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
156 for leaf in ty.walk() {
157 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
158 if leaf_ty.is_box() {
159 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
160 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
168 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
169 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
171 hir::ItemKind::Fn(..)
172 | hir::ItemKind::TyAlias(..)
173 | hir::ItemKind::Enum(..)
174 | hir::ItemKind::Struct(..)
175 | hir::ItemKind::Union(..) => {
176 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
177 self.check_heap_type(cx, it.span, cx.tcx.type_of(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);
333 impl EarlyLintPass for UnsafeCode {
334 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
335 if cx.sess().check_name(attr, sym::allow_internal_unsafe) {
336 self.report_unsafe(cx, attr.span, |lint| {
338 "`allow_internal_unsafe` allows defining \
339 macros using unsafe without triggering \
340 the `unsafe_code` lint at their call site",
347 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
348 if let ast::ExprKind::Block(ref blk, _) = e.kind {
349 // Don't warn about generated blocks; that'll just pollute the output.
350 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
351 self.report_unsafe(cx, blk.span, |lint| {
352 lint.build("usage of an `unsafe` block").emit()
358 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
360 ast::ItemKind::Trait(box ast::TraitKind(_, ast::Unsafe::Yes(_), ..)) => self
361 .report_unsafe(cx, it.span, |lint| {
362 lint.build("declaration of an `unsafe` trait").emit()
365 ast::ItemKind::Impl(box ast::ImplKind { unsafety: ast::Unsafe::Yes(_), .. }) => self
366 .report_unsafe(cx, it.span, |lint| {
367 lint.build("implementation of an `unsafe` trait").emit()
374 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
378 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
383 let msg = match ctxt {
384 FnCtxt::Foreign => return,
385 FnCtxt::Free => "declaration of an `unsafe` function",
386 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
387 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
389 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
395 /// The `missing_docs` lint detects missing documentation for public items.
399 /// ```rust,compile_fail
400 /// #![deny(missing_docs)]
408 /// This lint is intended to ensure that a library is well-documented.
409 /// Items without documentation can be difficult for users to understand
410 /// how to use properly.
412 /// This lint is "allow" by default because it can be noisy, and not all
413 /// projects may want to enforce everything to be documented.
416 "detects missing documentation for public members",
417 report_in_external_macro
420 pub struct MissingDoc {
421 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
422 doc_hidden_stack: Vec<bool>,
424 /// Private traits or trait items that leaked through. Don't check their methods.
425 private_traits: FxHashSet<hir::HirId>,
428 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
430 fn has_doc(sess: &Session, attr: &ast::Attribute) -> bool {
431 if attr.is_doc_comment() {
435 if !sess.check_name(attr, sym::doc) {
439 if attr.is_value_str() {
443 if let Some(list) = attr.meta_item_list() {
445 if meta.has_name(sym::include) || meta.has_name(sym::hidden) {
455 pub fn new() -> MissingDoc {
456 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
459 fn doc_hidden(&self) -> bool {
460 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
463 fn check_missing_docs_attrs(
465 cx: &LateContext<'_>,
466 id: Option<hir::HirId>,
467 attrs: &[ast::Attribute],
469 article: &'static str,
472 // If we're building a test harness, then warning about
473 // documentation is probably not really relevant right now.
474 if cx.sess().opts.test {
478 // `#[doc(hidden)]` disables missing_docs check.
479 if self.doc_hidden() {
483 // Only check publicly-visible items, using the result from the privacy pass.
484 // It's an option so the crate root can also use this function (it doesn't
486 if let Some(id) = id {
487 if !cx.access_levels.is_exported(id) {
492 let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
496 cx.tcx.sess.source_map().guess_head_span(sp),
498 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
505 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
506 fn enter_lint_attrs(&mut self, cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
507 let doc_hidden = self.doc_hidden()
508 || attrs.iter().any(|attr| {
509 cx.sess().check_name(attr, sym::doc)
510 && match attr.meta_item_list() {
512 Some(l) => attr::list_contains_name(&l, sym::hidden),
515 self.doc_hidden_stack.push(doc_hidden);
518 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
519 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
522 fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
523 self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
525 for macro_def in krate.exported_macros {
526 let has_doc = macro_def.attrs.iter().any(|a| has_doc(cx.sess(), a));
530 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
531 |lint| lint.build("missing documentation for macro").emit(),
537 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
539 hir::ItemKind::Trait(.., trait_item_refs) => {
540 // Issue #11592: traits are always considered exported, even when private.
541 if let hir::VisibilityKind::Inherited = it.vis.node {
542 self.private_traits.insert(it.hir_id);
543 for trait_item_ref in trait_item_refs {
544 self.private_traits.insert(trait_item_ref.id.hir_id);
549 hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref trait_ref), items, .. }) => {
550 // If the trait is private, add the impl items to `private_traits` so they don't get
551 // reported for missing docs.
552 let real_trait = trait_ref.path.res.def_id();
553 if let Some(def_id) = real_trait.as_local() {
554 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
555 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
556 if let hir::VisibilityKind::Inherited = item.vis.node {
557 for impl_item_ref in items {
558 self.private_traits.insert(impl_item_ref.id.hir_id);
566 hir::ItemKind::TyAlias(..)
567 | hir::ItemKind::Fn(..)
568 | hir::ItemKind::Mod(..)
569 | hir::ItemKind::Enum(..)
570 | hir::ItemKind::Struct(..)
571 | hir::ItemKind::Union(..)
572 | hir::ItemKind::Const(..)
573 | hir::ItemKind::Static(..) => {}
578 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
579 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
581 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
584 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
585 if self.private_traits.contains(&trait_item.hir_id) {
589 let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
590 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
592 self.check_missing_docs_attrs(
594 Some(trait_item.hir_id),
602 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
603 // If the method is an impl for a trait, don't doc.
604 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
608 let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
609 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
610 self.check_missing_docs_attrs(
612 Some(impl_item.hir_id),
620 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
621 let def_id = cx.tcx.hir().local_def_id(foreign_item.hir_id);
622 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
623 self.check_missing_docs_attrs(
625 Some(foreign_item.hir_id),
633 fn check_struct_field(&mut self, cx: &LateContext<'_>, sf: &hir::StructField<'_>) {
634 if !sf.is_positional() {
635 self.check_missing_docs_attrs(
646 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
647 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
652 /// The `missing_copy_implementations` lint detects potentially-forgotten
653 /// implementations of [`Copy`].
655 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
659 /// ```rust,compile_fail
660 /// #![deny(missing_copy_implementations)]
671 /// Historically (before 1.0), types were automatically marked as `Copy`
672 /// if possible. This was changed so that it required an explicit opt-in
673 /// by implementing the `Copy` trait. As part of this change, a lint was
674 /// added to alert if a copyable type was not marked `Copy`.
676 /// This lint is "allow" by default because this code isn't bad; it is
677 /// common to write newtypes like this specifically so that a `Copy` type
678 /// is no longer `Copy`. `Copy` types can result in unintended copies of
679 /// large data which can impact performance.
680 pub MISSING_COPY_IMPLEMENTATIONS,
682 "detects potentially-forgotten implementations of `Copy`"
685 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
687 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
688 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
689 if !cx.access_levels.is_reachable(item.hir_id) {
692 let (def, ty) = match item.kind {
693 hir::ItemKind::Struct(_, ref ast_generics) => {
694 if !ast_generics.params.is_empty() {
697 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
698 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
700 hir::ItemKind::Union(_, ref ast_generics) => {
701 if !ast_generics.params.is_empty() {
704 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
705 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
707 hir::ItemKind::Enum(_, ref ast_generics) => {
708 if !ast_generics.params.is_empty() {
711 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
712 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
716 if def.has_dtor(cx.tcx) {
719 let param_env = ty::ParamEnv::empty();
720 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
723 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
724 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
726 "type could implement `Copy`; consider adding `impl \
736 /// The `missing_debug_implementations` lint detects missing
737 /// implementations of [`fmt::Debug`].
739 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
743 /// ```rust,compile_fail
744 /// #![deny(missing_debug_implementations)]
753 /// Having a `Debug` implementation on all types can assist with
754 /// debugging, as it provides a convenient way to format and display a
755 /// value. Using the `#[derive(Debug)]` attribute will automatically
756 /// generate a typical implementation, or a custom implementation can be
757 /// added by manually implementing the `Debug` trait.
759 /// This lint is "allow" by default because adding `Debug` to all types can
760 /// have a negative impact on compile time and code size. It also requires
761 /// boilerplate to be added to every type, which can be an impediment.
762 MISSING_DEBUG_IMPLEMENTATIONS,
764 "detects missing implementations of Debug"
768 pub struct MissingDebugImplementations {
769 impling_types: Option<HirIdSet>,
772 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
774 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
775 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
776 if !cx.access_levels.is_reachable(item.hir_id) {
781 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
785 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
786 Some(debug) => debug,
790 if self.impling_types.is_none() {
791 let mut impls = HirIdSet::default();
792 cx.tcx.for_each_impl(debug, |d| {
793 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
794 if let Some(def_id) = ty_def.did.as_local() {
795 impls.insert(cx.tcx.hir().local_def_id_to_hir_id(def_id));
800 self.impling_types = Some(impls);
801 debug!("{:?}", self.impling_types);
804 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
805 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
807 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
808 or a manual implementation",
809 cx.tcx.def_path_str(debug)
818 /// The `anonymous_parameters` lint detects anonymous parameters in trait
823 /// ```rust,edition2015,compile_fail
824 /// #![deny(anonymous_parameters)]
836 /// This syntax is mostly a historical accident, and can be worked around
837 /// quite easily by adding an `_` pattern or a descriptive identifier:
841 /// fn foo(_: usize);
845 /// This syntax is now a hard error in the 2018 edition. In the 2015
846 /// edition, this lint is "allow" by default, because the old code is
847 /// still valid, and warning for all old code can be noisy. This lint
848 /// enables the [`cargo fix`] tool with the `--edition` flag to
849 /// automatically transition old code from the 2015 edition to 2018. The
850 /// tool will switch this lint to "warn" and will automatically apply the
851 /// suggested fix from the compiler (which is to add `_` to each
852 /// parameter). This provides a completely automated way to update old
853 /// code for a new edition. See [issue #41686] for more details.
855 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
856 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
857 pub ANONYMOUS_PARAMETERS,
859 "detects anonymous parameters",
860 @future_incompatible = FutureIncompatibleInfo {
861 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
862 edition: Some(Edition::Edition2018),
867 /// Checks for use of anonymous parameters (RFC 1685).
868 AnonymousParameters => [ANONYMOUS_PARAMETERS]
871 impl EarlyLintPass for AnonymousParameters {
872 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
873 if let ast::AssocItemKind::Fn(box FnKind(_, ref sig, _, _)) = it.kind {
874 for arg in sig.decl.inputs.iter() {
875 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
876 if ident.name == kw::Empty {
877 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
878 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
880 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
881 (snip.as_str(), Applicability::MachineApplicable)
883 ("<type>", Applicability::HasPlaceholders)
887 "anonymous parameters are deprecated and will be \
888 removed in the next edition.",
892 "try naming the parameter or explicitly \
894 format!("_: {}", ty_snip),
906 /// Check for use of attributes which have been deprecated.
908 pub struct DeprecatedAttr {
909 // This is not free to compute, so we want to keep it around, rather than
910 // compute it for every attribute.
911 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
914 impl_lint_pass!(DeprecatedAttr => []);
916 impl DeprecatedAttr {
917 pub fn new() -> DeprecatedAttr {
918 DeprecatedAttr { depr_attrs: deprecated_attributes() }
922 fn lint_deprecated_attr(
923 cx: &EarlyContext<'_>,
924 attr: &ast::Attribute,
926 suggestion: Option<&str>,
928 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
930 .span_suggestion_short(
932 suggestion.unwrap_or("remove this attribute"),
934 Applicability::MachineApplicable,
940 impl EarlyLintPass for DeprecatedAttr {
941 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
942 for &&(n, _, _, ref g) in &self.depr_attrs {
943 if attr.ident().map(|ident| ident.name) == Some(n) {
944 if let &AttributeGate::Gated(
945 Stability::Deprecated(link, suggestion),
952 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
953 lint_deprecated_attr(cx, attr, &msg, suggestion);
958 if cx.sess().check_name(attr, sym::no_start) || cx.sess().check_name(attr, sym::crate_id) {
959 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
960 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
961 lint_deprecated_attr(cx, attr, &msg, None);
966 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
967 let mut attrs = attrs.iter().peekable();
969 // Accumulate a single span for sugared doc comments.
970 let mut sugared_span: Option<Span> = None;
972 while let Some(attr) = attrs.next() {
973 if attr.is_doc_comment() {
975 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
978 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
982 let span = sugared_span.take().unwrap_or(attr.span);
984 if attr.is_doc_comment() || cx.sess().check_name(attr, sym::doc) {
985 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
986 let mut err = lint.build("unused doc comment");
989 format!("rustdoc does not generate documentation for {}", node_kind),
997 impl EarlyLintPass for UnusedDocComment {
998 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
999 let kind = match stmt.kind {
1000 ast::StmtKind::Local(..) => "statements",
1001 // Disabled pending discussion in #78306
1002 ast::StmtKind::Item(..) => return,
1003 // expressions will be reported by `check_expr`.
1004 ast::StmtKind::Empty
1005 | ast::StmtKind::Semi(_)
1006 | ast::StmtKind::Expr(_)
1007 | ast::StmtKind::MacCall(_) => return,
1010 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1013 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1014 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1015 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1018 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1019 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1024 /// The `no_mangle_const_items` lint detects any `const` items with the
1025 /// [`no_mangle` attribute].
1027 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1031 /// ```rust,compile_fail
1033 /// const FOO: i32 = 5;
1040 /// Constants do not have their symbols exported, and therefore, this
1041 /// probably means you meant to use a [`static`], not a [`const`].
1043 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1044 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1045 NO_MANGLE_CONST_ITEMS,
1047 "const items will not have their symbols exported"
1051 /// The `no_mangle_generic_items` lint detects generic items that must be
1058 /// fn foo<T>(t: T) {
1067 /// An function with generics must have its symbol mangled to accommodate
1068 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1069 /// this situation, and should be removed.
1071 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1072 NO_MANGLE_GENERIC_ITEMS,
1074 "generic items must be mangled"
1077 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1079 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1080 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1082 hir::ItemKind::Fn(.., ref generics, _) => {
1083 if let Some(no_mangle_attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
1084 for param in generics.params {
1086 GenericParamKind::Lifetime { .. } => {}
1087 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1088 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
1090 "functions generic over types or consts must be mangled",
1092 .span_suggestion_short(
1093 no_mangle_attr.span,
1094 "remove this attribute",
1096 // Use of `#[no_mangle]` suggests FFI intent; correct
1097 // fix may be to monomorphize source by hand
1098 Applicability::MaybeIncorrect,
1108 hir::ItemKind::Const(..) => {
1109 if cx.sess().contains_name(&it.attrs, sym::no_mangle) {
1110 // Const items do not refer to a particular location in memory, and therefore
1111 // don't have anything to attach a symbol to
1112 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1113 let msg = "const items should never be `#[no_mangle]`";
1114 let mut err = lint.build(msg);
1116 // account for "pub const" (#45562)
1121 .span_to_snippet(it.span)
1122 .map(|snippet| snippet.find("const").unwrap_or(0))
1123 .unwrap_or(0) as u32;
1124 // `const` is 5 chars
1125 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1126 err.span_suggestion(
1128 "try a static value",
1129 "pub static".to_owned(),
1130 Applicability::MachineApplicable,
1142 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1143 /// T` because it is [undefined behavior].
1145 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1149 /// ```rust,compile_fail
1151 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1159 /// Certain assumptions are made about aliasing of data, and this transmute
1160 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1162 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1165 "mutating transmuted &mut T from &T may cause undefined behavior"
1168 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1170 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1171 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1172 use rustc_target::spec::abi::Abi::RustIntrinsic;
1173 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1174 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1176 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1177 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1178 consider instead using an UnsafeCell";
1179 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
1183 fn get_transmute_from_to<'tcx>(
1184 cx: &LateContext<'tcx>,
1185 expr: &hir::Expr<'_>,
1186 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1187 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1188 cx.qpath_res(qpath, expr.hir_id)
1192 if let Res::Def(DefKind::Fn, did) = def {
1193 if !def_id_is_transmute(cx, did) {
1196 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1197 let from = sig.inputs().skip_binder()[0];
1198 let to = sig.output().skip_binder();
1199 return Some((from, to));
1204 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1205 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
1206 && cx.tcx.item_name(def_id) == sym::transmute
1212 /// The `unstable_features` is deprecated and should no longer be used.
1215 "enabling unstable features (deprecated. do not use)"
1219 /// Forbids using the `#[feature(...)]` attribute
1220 UnstableFeatures => [UNSTABLE_FEATURES]
1223 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1224 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1225 if cx.sess().check_name(attr, sym::feature) {
1226 if let Some(items) = attr.meta_item_list() {
1228 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1229 lint.build("unstable feature").emit()
1238 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1243 /// ```rust,compile_fail
1244 /// #![deny(unreachable_pub)]
1256 /// A bare `pub` visibility may be misleading if the item is not actually
1257 /// publicly exported from the crate. The `pub(crate)` visibility is
1258 /// recommended to be used instead, which more clearly expresses the intent
1259 /// that the item is only visible within its own crate.
1261 /// This lint is "allow" by default because it will trigger for a large
1262 /// amount existing Rust code, and has some false-positives. Eventually it
1263 /// is desired for this to become warn-by-default.
1264 pub UNREACHABLE_PUB,
1266 "`pub` items not reachable from crate root"
1270 /// Lint for items marked `pub` that aren't reachable from other crates.
1271 UnreachablePub => [UNREACHABLE_PUB]
1274 impl UnreachablePub {
1277 cx: &LateContext<'_>,
1280 vis: &hir::Visibility<'_>,
1284 let mut applicability = Applicability::MachineApplicable;
1286 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1287 if span.from_expansion() {
1288 applicability = Applicability::MaybeIncorrect;
1290 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1291 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1292 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1293 let replacement = if cx.tcx.features().crate_visibility_modifier {
1300 err.span_suggestion(
1302 "consider restricting its visibility",
1307 err.help("or consider exporting it for use by other crates");
1317 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1318 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1319 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1322 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1326 foreign_item.hir_id,
1333 fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
1334 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1337 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1338 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1343 /// The `type_alias_bounds` lint detects bounds in type aliases.
1348 /// type SendVec<T: Send> = Vec<T>;
1355 /// The trait bounds in a type alias are currently ignored, and should not
1356 /// be included to avoid confusion. This was previously allowed
1357 /// unintentionally; this may become a hard error in the future.
1360 "bounds in type aliases are not enforced"
1364 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1365 /// They are relevant when using associated types, but otherwise neither checked
1366 /// at definition site nor enforced at use site.
1367 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1370 impl TypeAliasBounds {
1371 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1373 hir::QPath::TypeRelative(ref ty, _) => {
1374 // If this is a type variable, we found a `T::Assoc`.
1376 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1377 matches!(path.res, Res::Def(DefKind::TyParam, _))
1382 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1386 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1387 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1388 // bound. Let's see if this type does that.
1390 // We use a HIR visitor to walk the type.
1391 use rustc_hir::intravisit::{self, Visitor};
1392 struct WalkAssocTypes<'a, 'db> {
1393 err: &'a mut DiagnosticBuilder<'db>,
1395 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1396 type Map = intravisit::ErasedMap<'v>;
1398 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1399 intravisit::NestedVisitorMap::None
1402 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1403 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1406 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1407 associated types in type aliases",
1410 intravisit::walk_qpath(self, qpath, id, span)
1414 // Let's go for a walk!
1415 let mut visitor = WalkAssocTypes { err };
1416 visitor.visit_ty(ty);
1420 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1421 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1422 let (ty, type_alias_generics) = match item.kind {
1423 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1426 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1427 // Bounds are respected for `type X = impl Trait`
1430 let mut suggested_changing_assoc_types = false;
1431 // There must not be a where clause
1432 if !type_alias_generics.where_clause.predicates.is_empty() {
1436 let mut err = lint.build("where clauses are not enforced in type aliases");
1437 let spans: Vec<_> = type_alias_generics
1441 .map(|pred| pred.span())
1443 err.set_span(spans);
1444 err.span_suggestion(
1445 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1446 "the clause will not be checked when the type alias is used, and should be removed",
1448 Applicability::MachineApplicable,
1450 if !suggested_changing_assoc_types {
1451 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1452 suggested_changing_assoc_types = true;
1458 // The parameters must not have bounds
1459 for param in type_alias_generics.params.iter() {
1460 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1461 let suggestion = spans
1464 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1465 (start.to(*sp), String::new())
1468 if !spans.is_empty() {
1469 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1471 lint.build("bounds on generic parameters are not enforced in type aliases");
1472 let msg = "the bound will not be checked when the type alias is used, \
1473 and should be removed";
1474 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1475 if !suggested_changing_assoc_types {
1476 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1477 suggested_changing_assoc_types = true;
1487 /// Lint constants that are erroneous.
1488 /// Without this lint, we might not get any diagnostic if the constant is
1489 /// unused within this crate, even though downstream crates can't use it
1490 /// without producing an error.
1491 UnusedBrokenConst => []
1494 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1495 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1497 hir::ItemKind::Const(_, body_id) => {
1498 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1499 // trigger the query once for all constants since that will already report the errors
1500 // FIXME: Use ensure here
1501 let _ = cx.tcx.const_eval_poly(def_id);
1503 hir::ItemKind::Static(_, _, body_id) => {
1504 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1505 // FIXME: Use ensure here
1506 let _ = cx.tcx.eval_static_initializer(def_id);
1514 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1515 /// any type parameters.
1520 /// #![feature(trivial_bounds)]
1521 /// pub struct A where i32: Copy;
1528 /// Usually you would not write a trait bound that you know is always
1529 /// true, or never true. However, when using macros, the macro may not
1530 /// know whether or not the constraint would hold or not at the time when
1531 /// generating the code. Currently, the compiler does not alert you if the
1532 /// constraint is always true, and generates an error if it is never true.
1533 /// The `trivial_bounds` feature changes this to be a warning in both
1534 /// cases, giving macros more freedom and flexibility to generate code,
1535 /// while still providing a signal when writing non-macro code that
1536 /// something is amiss.
1538 /// See [RFC 2056] for more details. This feature is currently only
1539 /// available on the nightly channel, see [tracking issue #48214].
1541 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1542 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1545 "these bounds don't depend on an type parameters"
1549 /// Lint for trait and lifetime bounds that don't depend on type parameters
1550 /// which either do nothing, or stop the item from being used.
1551 TrivialConstraints => [TRIVIAL_BOUNDS]
1554 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1555 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1556 use rustc_middle::ty::fold::TypeFoldable;
1557 use rustc_middle::ty::PredicateKind::*;
1559 if cx.tcx.features().trivial_bounds {
1560 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1561 let predicates = cx.tcx.predicates_of(def_id);
1562 for &(predicate, span) in predicates.predicates {
1563 let predicate_kind_name = match predicate.kind().skip_binder() {
1564 Trait(..) => "Trait",
1566 RegionOutlives(..) => "Lifetime",
1568 // Ignore projections, as they can only be global
1569 // if the trait bound is global
1571 // Ignore bounds that a user can't type
1576 ConstEvaluatable(..) |
1578 TypeWellFormedFromEnv(..) => continue,
1580 if predicate.is_global() {
1581 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1582 lint.build(&format!(
1583 "{} bound {} does not depend on any type \
1584 or lifetime parameters",
1585 predicate_kind_name, predicate
1596 /// Does nothing as a lint pass, but registers some `Lint`s
1597 /// which are used by other parts of the compiler.
1601 NON_SHORTHAND_FIELD_PATTERNS,
1604 MISSING_COPY_IMPLEMENTATIONS,
1605 MISSING_DEBUG_IMPLEMENTATIONS,
1606 ANONYMOUS_PARAMETERS,
1607 UNUSED_DOC_COMMENTS,
1608 NO_MANGLE_CONST_ITEMS,
1609 NO_MANGLE_GENERIC_ITEMS,
1619 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1620 /// pattern], which is deprecated.
1622 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1638 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1639 /// confusion with the [`..` range expression]. Use the new form instead.
1641 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1642 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1644 "`...` range patterns are deprecated"
1648 pub struct EllipsisInclusiveRangePatterns {
1649 /// If `Some(_)`, suppress all subsequent pattern
1650 /// warnings for better diagnostics.
1651 node_id: Option<ast::NodeId>,
1654 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1656 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1657 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1658 if self.node_id.is_some() {
1659 // Don't recursively warn about patterns inside range endpoints.
1663 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1665 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1666 /// corresponding to the ellipsis.
1667 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1672 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1673 ) => Some((a.as_deref(), b, *span)),
1678 let (parenthesise, endpoints) = match &pat.kind {
1679 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1680 _ => (false, matches_ellipsis_pat(pat)),
1683 if let Some((start, end, join)) = endpoints {
1684 let msg = "`...` range patterns are deprecated";
1685 let suggestion = "use `..=` for an inclusive range";
1687 self.node_id = Some(pat.id);
1688 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1689 let end = expr_to_string(&end);
1690 let replace = match start {
1691 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1692 None => format!("&(..={})", end),
1699 Applicability::MachineApplicable,
1704 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1706 .span_suggestion_short(
1710 Applicability::MachineApplicable,
1718 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1719 if let Some(node_id) = self.node_id {
1720 if pat.id == node_id {
1728 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1729 /// that are not able to be run by the test harness because they are in a
1730 /// position where they are not nameable.
1732 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1740 /// // This test will not fail because it does not run.
1741 /// assert_eq!(1, 2);
1750 /// In order for the test harness to run a test, the test function must be
1751 /// located in a position where it can be accessed from the crate root.
1752 /// This generally means it must be defined in a module, and not anywhere
1753 /// else such as inside another function. The compiler previously allowed
1754 /// this without an error, so a lint was added as an alert that a test is
1755 /// not being used. Whether or not this should be allowed has not yet been
1756 /// decided, see [RFC 2471] and [issue #36629].
1758 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1759 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1760 UNNAMEABLE_TEST_ITEMS,
1762 "detects an item that cannot be named being marked as `#[test_case]`",
1763 report_in_external_macro
1766 pub struct UnnameableTestItems {
1767 boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1768 items_nameable: bool,
1771 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1773 impl UnnameableTestItems {
1774 pub fn new() -> Self {
1775 Self { boundary: None, items_nameable: true }
1779 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1780 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1781 if self.items_nameable {
1782 if let hir::ItemKind::Mod(..) = it.kind {
1784 self.items_nameable = false;
1785 self.boundary = Some(it.hir_id);
1790 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::rustc_test_marker) {
1791 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1792 lint.build("cannot test inner items").emit()
1797 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1798 if !self.items_nameable && self.boundary == Some(it.hir_id) {
1799 self.items_nameable = true;
1805 /// The `keyword_idents` lint detects edition keywords being used as an
1810 /// ```rust,edition2015,compile_fail
1811 /// #![deny(keyword_idents)]
1820 /// Rust [editions] allow the language to evolve without breaking
1821 /// backwards compatibility. This lint catches code that uses new keywords
1822 /// that are added to the language that are used as identifiers (such as a
1823 /// variable name, function name, etc.). If you switch the compiler to a
1824 /// new edition without updating the code, then it will fail to compile if
1825 /// you are using a new keyword as an identifier.
1827 /// You can manually change the identifiers to a non-keyword, or use a
1828 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1830 /// This lint solves the problem automatically. It is "allow" by default
1831 /// because the code is perfectly valid in older editions. The [`cargo
1832 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1833 /// and automatically apply the suggested fix from the compiler (which is
1834 /// to use a raw identifier). This provides a completely automated way to
1835 /// update old code for a new edition.
1837 /// [editions]: https://doc.rust-lang.org/edition-guide/
1838 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1839 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1842 "detects edition keywords being used as an identifier",
1843 @future_incompatible = FutureIncompatibleInfo {
1844 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1845 edition: Some(Edition::Edition2018),
1850 /// Check for uses of edition keywords used as an identifier.
1851 KeywordIdents => [KEYWORD_IDENTS]
1854 struct UnderMacro(bool);
1856 impl KeywordIdents {
1857 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1858 for tt in tokens.into_trees() {
1860 // Only report non-raw idents.
1861 TokenTree::Token(token) => {
1862 if let Some((ident, false)) = token.ident() {
1863 self.check_ident_token(cx, UnderMacro(true), ident);
1866 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1871 fn check_ident_token(
1873 cx: &EarlyContext<'_>,
1874 UnderMacro(under_macro): UnderMacro,
1877 let next_edition = match cx.sess.edition() {
1878 Edition::Edition2015 => {
1880 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1882 // rust-lang/rust#56327: Conservatively do not
1883 // attempt to report occurrences of `dyn` within
1884 // macro definitions or invocations, because `dyn`
1885 // can legitimately occur as a contextual keyword
1886 // in 2015 code denoting its 2018 meaning, and we
1887 // do not want rustfix to inject bugs into working
1888 // code by rewriting such occurrences.
1890 // But if we see `dyn` outside of a macro, we know
1891 // its precise role in the parsed AST and thus are
1892 // assured this is truly an attempt to use it as
1894 kw::Dyn if !under_macro => Edition::Edition2018,
1900 // There are no new keywords yet for the 2018 edition and beyond.
1904 // Don't lint `r#foo`.
1905 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1909 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1910 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1913 "you can use a raw identifier to stay compatible",
1914 format!("r#{}", ident),
1915 Applicability::MachineApplicable,
1922 impl EarlyLintPass for KeywordIdents {
1923 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1924 self.check_tokens(cx, mac_def.body.inner_tokens());
1926 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1927 self.check_tokens(cx, mac.args.inner_tokens());
1929 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1930 self.check_ident_token(cx, UnderMacro(false), ident);
1934 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1936 impl ExplicitOutlivesRequirements {
1937 fn lifetimes_outliving_lifetime<'tcx>(
1938 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1940 ) -> Vec<ty::Region<'tcx>> {
1943 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
1944 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
1945 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
1953 fn lifetimes_outliving_type<'tcx>(
1954 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1956 ) -> Vec<ty::Region<'tcx>> {
1959 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
1960 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
1961 a.is_param(index).then_some(b)
1968 fn collect_outlived_lifetimes<'tcx>(
1970 param: &'tcx hir::GenericParam<'tcx>,
1972 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1973 ty_generics: &'tcx ty::Generics,
1974 ) -> Vec<ty::Region<'tcx>> {
1976 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1979 hir::GenericParamKind::Lifetime { .. } => {
1980 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1982 hir::GenericParamKind::Type { .. } => {
1983 Self::lifetimes_outliving_type(inferred_outlives, index)
1985 hir::GenericParamKind::Const { .. } => Vec::new(),
1989 fn collect_outlives_bound_spans<'tcx>(
1992 bounds: &hir::GenericBounds<'_>,
1993 inferred_outlives: &[ty::Region<'tcx>],
1995 ) -> Vec<(usize, Span)> {
1996 use rustc_middle::middle::resolve_lifetime::Region;
2001 .filter_map(|(i, bound)| {
2002 if let hir::GenericBound::Outlives(lifetime) = bound {
2003 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2004 Some(Region::Static) if infer_static => {
2005 inferred_outlives.iter().any(|r| matches!(r, ty::ReStatic))
2007 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2008 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
2012 is_inferred.then_some((i, bound.span()))
2020 fn consolidate_outlives_bound_spans(
2023 bounds: &hir::GenericBounds<'_>,
2024 bound_spans: Vec<(usize, Span)>,
2026 if bounds.is_empty() {
2029 if bound_spans.len() == bounds.len() {
2030 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2031 // If all bounds are inferable, we want to delete the colon, so
2032 // start from just after the parameter (span passed as argument)
2033 vec![lo.to(last_bound_span)]
2035 let mut merged = Vec::new();
2036 let mut last_merged_i = None;
2038 let mut from_start = true;
2039 for (i, bound_span) in bound_spans {
2040 match last_merged_i {
2041 // If the first bound is inferable, our span should also eat the leading `+`.
2043 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2044 last_merged_i = Some(0);
2046 // If consecutive bounds are inferable, merge their spans
2047 Some(h) if i == h + 1 => {
2048 if let Some(tail) = merged.last_mut() {
2049 // Also eat the trailing `+` if the first
2050 // more-than-one bound is inferable
2051 let to_span = if from_start && i < bounds.len() {
2052 bounds[i + 1].span().shrink_to_lo()
2056 *tail = tail.to(to_span);
2057 last_merged_i = Some(i);
2059 bug!("another bound-span visited earlier");
2063 // When we find a non-inferable bound, subsequent inferable bounds
2064 // won't be consecutive from the start (and we'll eat the leading
2065 // `+` rather than the trailing one)
2067 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2068 last_merged_i = Some(i);
2077 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2078 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2079 use rustc_middle::middle::resolve_lifetime::Region;
2081 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
2082 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
2083 if let hir::ItemKind::Struct(_, ref hir_generics)
2084 | hir::ItemKind::Enum(_, ref hir_generics)
2085 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2087 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2088 if inferred_outlives.is_empty() {
2092 let ty_generics = cx.tcx.generics_of(def_id);
2094 let mut bound_count = 0;
2095 let mut lint_spans = Vec::new();
2097 for param in hir_generics.params {
2098 let has_lifetime_bounds = param
2101 .any(|bound| matches!(bound, hir::GenericBound::Outlives(_)));
2102 if !has_lifetime_bounds {
2106 let relevant_lifetimes =
2107 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
2108 if relevant_lifetimes.is_empty() {
2112 let bound_spans = self.collect_outlives_bound_spans(
2115 &relevant_lifetimes,
2118 bound_count += bound_spans.len();
2119 lint_spans.extend(self.consolidate_outlives_bound_spans(
2120 param.span.shrink_to_hi(),
2126 let mut where_lint_spans = Vec::new();
2127 let mut dropped_predicate_count = 0;
2128 let num_predicates = hir_generics.where_clause.predicates.len();
2129 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
2130 let (relevant_lifetimes, bounds, span) = match where_predicate {
2131 hir::WherePredicate::RegionPredicate(predicate) => {
2132 if let Some(Region::EarlyBound(index, ..)) =
2133 cx.tcx.named_region(predicate.lifetime.hir_id)
2136 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2144 hir::WherePredicate::BoundPredicate(predicate) => {
2145 // FIXME we can also infer bounds on associated types,
2146 // and should check for them here.
2147 match predicate.bounded_ty.kind {
2148 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2149 if let Res::Def(DefKind::TyParam, def_id) = path.res {
2150 let index = ty_generics.param_def_id_to_index[&def_id];
2152 Self::lifetimes_outliving_type(inferred_outlives, index),
2167 if relevant_lifetimes.is_empty() {
2171 let bound_spans = self.collect_outlives_bound_spans(
2174 &relevant_lifetimes,
2177 bound_count += bound_spans.len();
2179 let drop_predicate = bound_spans.len() == bounds.len();
2181 dropped_predicate_count += 1;
2184 // If all the bounds on a predicate were inferable and there are
2185 // further predicates, we want to eat the trailing comma.
2186 if drop_predicate && i + 1 < num_predicates {
2187 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
2188 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2190 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2191 span.shrink_to_lo(),
2198 // If all predicates are inferable, drop the entire clause
2199 // (including the `where`)
2200 if num_predicates > 0 && dropped_predicate_count == num_predicates {
2201 let where_span = hir_generics
2204 .expect("span of (nonempty) where clause should exist");
2205 // Extend the where clause back to the closing `>` of the
2206 // generics, except for tuple struct, which have the `where`
2207 // after the fields of the struct.
2208 let full_where_span =
2209 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2212 hir_generics.span.shrink_to_hi().to(where_span)
2214 lint_spans.push(full_where_span);
2216 lint_spans.extend(where_lint_spans);
2219 if !lint_spans.is_empty() {
2220 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2221 lint.build("outlives requirements can be inferred")
2222 .multipart_suggestion(
2223 if bound_count == 1 {
2226 "remove these bounds"
2230 .map(|span| (span, "".to_owned()))
2231 .collect::<Vec<_>>(),
2232 Applicability::MachineApplicable,
2242 /// The `incomplete_features` lint detects unstable features enabled with
2243 /// the [`feature` attribute] that may function improperly in some or all
2246 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2251 /// #![feature(generic_associated_types)]
2258 /// Although it is encouraged for people to experiment with unstable
2259 /// features, some of them are known to be incomplete or faulty. This lint
2260 /// is a signal that the feature has not yet been finished, and you may
2261 /// experience problems with it.
2262 pub INCOMPLETE_FEATURES,
2264 "incomplete features that may function improperly in some or all cases"
2268 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
2269 IncompleteFeatures => [INCOMPLETE_FEATURES]
2272 impl EarlyLintPass for IncompleteFeatures {
2273 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2274 let features = cx.sess.features_untracked();
2276 .declared_lang_features
2278 .map(|(name, span, _)| (name, span))
2279 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2280 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
2281 .for_each(|(&name, &span)| {
2282 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2283 let mut builder = lint.build(&format!(
2284 "the feature `{}` is incomplete and may not be safe to use \
2285 and/or cause compiler crashes",
2288 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2289 builder.note(&format!(
2290 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
2291 for more information",
2295 if HAS_MIN_FEATURES.contains(&name) {
2296 builder.help(&format!(
2297 "consider using `min_{}` instead, which is more stable and complete",
2307 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2310 /// The `invalid_value` lint detects creating a value that is not valid,
2311 /// such as a NULL reference.
2316 /// # #![allow(unused)]
2318 /// let x: &'static i32 = std::mem::zeroed();
2326 /// In some situations the compiler can detect that the code is creating
2327 /// an invalid value, which should be avoided.
2329 /// In particular, this lint will check for improper use of
2330 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2331 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2332 /// lint should provide extra information to indicate what the problem is
2333 /// and a possible solution.
2335 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2336 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2337 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2338 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2339 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2342 "an invalid value is being created (such as a NULL reference)"
2345 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2347 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2348 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2349 #[derive(Debug, Copy, Clone, PartialEq)]
2355 /// Information about why a type cannot be initialized this way.
2356 /// Contains an error message and optionally a span to point at.
2357 type InitError = (String, Option<Span>);
2359 /// Test if this constant is all-0.
2360 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2361 use hir::ExprKind::*;
2362 use rustc_ast::LitKind::*;
2365 if let Int(i, _) = lit.node {
2371 Tup(tup) => tup.iter().all(is_zero),
2376 /// Determine if this expression is a "dangerous initialization".
2377 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2378 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2379 // Find calls to `mem::{uninitialized,zeroed}` methods.
2380 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2381 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2383 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
2384 return Some(InitKind::Zeroed);
2385 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
2386 return Some(InitKind::Uninit);
2387 } else if cx.tcx.is_diagnostic_item(sym::transmute, def_id) && is_zero(&args[0])
2389 return Some(InitKind::Zeroed);
2392 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
2393 // Find problematic calls to `MaybeUninit::assume_init`.
2394 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2395 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2396 // This is a call to *some* method named `assume_init`.
2397 // See if the `self` parameter is one of the dangerous constructors.
2398 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2399 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2400 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2402 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
2403 return Some(InitKind::Zeroed);
2404 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
2405 return Some(InitKind::Uninit);
2415 /// Test if this enum has several actually "existing" variants.
2416 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2417 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
2418 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2419 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
2420 existing_variants > 1
2423 /// Return `Some` only if we are sure this type does *not*
2424 /// allow zero initialization.
2425 fn ty_find_init_error<'tcx>(
2429 ) -> Option<InitError> {
2430 use rustc_middle::ty::TyKind::*;
2432 // Primitive types that don't like 0 as a value.
2433 Ref(..) => Some(("references must be non-null".to_string(), None)),
2434 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2435 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2436 Never => Some(("the `!` type has no valid value".to_string(), None)),
2437 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2438 // raw ptr to dyn Trait
2440 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2442 // Primitive types with other constraints.
2443 Bool if init == InitKind::Uninit => {
2444 Some(("booleans must be either `true` or `false`".to_string(), None))
2446 Char if init == InitKind::Uninit => {
2447 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2449 // Recurse and checks for some compound types.
2450 Adt(adt_def, substs) if !adt_def.is_union() => {
2451 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2452 use std::ops::Bound;
2453 match tcx.layout_scalar_valid_range(adt_def.did) {
2454 // We exploit here that `layout_scalar_valid_range` will never
2455 // return `Bound::Excluded`. (And we have tests checking that we
2456 // handle the attribute correctly.)
2457 (Bound::Included(lo), _) if lo > 0 => {
2458 return Some((format!("`{}` must be non-null", ty), None));
2460 (Bound::Included(_), _) | (_, Bound::Included(_))
2461 if init == InitKind::Uninit =>
2465 "`{}` must be initialized inside its custom valid range",
2474 match adt_def.variants.len() {
2475 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2477 // Struct, or enum with exactly one variant.
2478 // Proceed recursively, check all fields.
2479 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2480 variant.fields.iter().find_map(|field| {
2481 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2484 // Point to this field, should be helpful for figuring
2485 // out where the source of the error is.
2486 let span = tcx.def_span(field.did);
2489 " (in this {} field)",
2502 // Multi-variant enum.
2504 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2505 let span = tcx.def_span(adt_def.did);
2507 "enums have to be initialized to a variant".to_string(),
2511 // In principle, for zero-initialization we could figure out which variant corresponds
2512 // to tag 0, and check that... but for now we just accept all zero-initializations.
2519 // Proceed recursively, check all fields.
2520 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2522 // Conservative fallback.
2527 if let Some(init) = is_dangerous_init(cx, expr) {
2528 // This conjures an instance of a type out of nothing,
2529 // using zeroed or uninitialized memory.
2530 // We are extremely conservative with what we warn about.
2531 let conjured_ty = cx.typeck_results().expr_ty(expr);
2532 if let Some((msg, span)) =
2533 with_no_trimmed_paths(|| ty_find_init_error(cx.tcx, conjured_ty, init))
2535 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2536 let mut err = lint.build(&format!(
2537 "the type `{}` does not permit {}",
2540 InitKind::Zeroed => "zero-initialization",
2541 InitKind::Uninit => "being left uninitialized",
2544 err.span_label(expr.span, "this code causes undefined behavior when executed");
2547 "help: use `MaybeUninit<T>` instead, \
2548 and only call `assume_init` after initialization is done",
2550 if let Some(span) = span {
2551 err.span_note(span, &msg);
2563 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2564 /// has been declared with the same name but different types.
2584 /// Because two symbols of the same name cannot be resolved to two
2585 /// different functions at link time, and one function cannot possibly
2586 /// have two types, a clashing extern declaration is almost certainly a
2587 /// mistake. Check to make sure that the `extern` definitions are correct
2588 /// and equivalent, and possibly consider unifying them in one location.
2590 /// This lint does not run between crates because a project may have
2591 /// dependencies which both rely on the same extern function, but declare
2592 /// it in a different (but valid) way. For example, they may both declare
2593 /// an opaque type for one or more of the arguments (which would end up
2594 /// distinct types), or use types that are valid conversions in the
2595 /// language the `extern fn` is defined in. In these cases, the compiler
2596 /// can't say that the clashing declaration is incorrect.
2597 pub CLASHING_EXTERN_DECLARATIONS,
2599 "detects when an extern fn has been declared with the same name but different types"
2602 pub struct ClashingExternDeclarations {
2603 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2604 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2605 /// the symbol should be reported as a clashing declaration.
2606 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2607 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2608 seen_decls: FxHashMap<Symbol, HirId>,
2611 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2612 /// just from declaration itself. This is important because we don't want to report clashes on
2613 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2616 /// The name of the symbol + the span of the annotation which introduced the link name.
2618 /// No link name, so just the name of the symbol.
2623 fn get_name(&self) -> Symbol {
2625 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2630 impl ClashingExternDeclarations {
2631 crate fn new() -> Self {
2632 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2634 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2635 /// for the item, return its HirId without updating the set.
2636 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2637 let hid = fi.hir_id;
2639 let local_did = tcx.hir().local_def_id(fi.hir_id);
2640 let did = local_did.to_def_id();
2641 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2642 let name = Symbol::intern(tcx.symbol_name(instance).name);
2643 if let Some(&hir_id) = self.seen_decls.get(&name) {
2644 // Avoid updating the map with the new entry when we do find a collision. We want to
2645 // make sure we're always pointing to the first definition as the previous declaration.
2646 // This lets us avoid emitting "knock-on" diagnostics.
2649 self.seen_decls.insert(name, hid)
2653 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2654 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2656 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2657 let did = tcx.hir().local_def_id(fi.hir_id);
2658 if let Some((overridden_link_name, overridden_link_name_span)) =
2659 tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2660 // FIXME: Instead of searching through the attributes again to get span
2661 // information, we could have codegen_fn_attrs also give span information back for
2662 // where the attribute was defined. However, until this is found to be a
2663 // bottleneck, this does just fine.
2665 overridden_link_name,
2666 tcx.get_attrs(did.to_def_id())
2668 .find(|at| tcx.sess.check_name(at, sym::link_name))
2674 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2676 SymbolName::Normal(fi.ident.name)
2680 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2681 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2682 /// with the same members (as the declarations shouldn't clash).
2683 fn structurally_same_type<'tcx>(
2684 cx: &LateContext<'tcx>,
2689 fn structurally_same_type_impl<'tcx>(
2690 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2691 cx: &LateContext<'tcx>,
2696 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2699 // Given a transparent newtype, reach through and grab the inner
2700 // type unless the newtype makes the type non-null.
2701 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2704 if let ty::Adt(def, substs) = *ty.kind() {
2705 let is_transparent = def.subst(tcx, substs).repr.transparent();
2706 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, &def);
2708 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2709 ty, is_transparent, is_non_null
2711 if is_transparent && !is_non_null {
2712 debug_assert!(def.variants.len() == 1);
2713 let v = &def.variants[VariantIdx::new(0)];
2714 ty = transparent_newtype_field(tcx, v)
2716 "single-variant transparent structure with zero-sized field",
2722 debug!("non_transparent_ty -> {:?}", ty);
2727 let a = non_transparent_ty(a);
2728 let b = non_transparent_ty(b);
2730 if !seen_types.insert((a, b)) {
2731 // We've encountered a cycle. There's no point going any further -- the types are
2732 // structurally the same.
2736 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2737 // All nominally-same types are structurally same, too.
2740 // Do a full, depth-first comparison between the two.
2741 use rustc_middle::ty::TyKind::*;
2742 let a_kind = a.kind();
2743 let b_kind = b.kind();
2745 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2746 debug!("compare_layouts({:?}, {:?})", a, b);
2747 let a_layout = &cx.layout_of(a)?.layout.abi;
2748 let b_layout = &cx.layout_of(b)?.layout.abi;
2750 "comparing layouts: {:?} == {:?} = {}",
2753 a_layout == b_layout
2755 Ok(a_layout == b_layout)
2758 #[allow(rustc::usage_of_ty_tykind)]
2759 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2760 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2763 ensure_sufficient_stack(|| {
2764 match (a_kind, b_kind) {
2765 (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2766 let a = a.subst(cx.tcx, a_substs);
2767 let b = b.subst(cx.tcx, b_substs);
2768 debug!("Comparing {:?} and {:?}", a, b);
2770 // We can immediately rule out these types as structurally same if
2771 // their layouts differ.
2772 match compare_layouts(a, b) {
2773 Ok(false) => return false,
2774 _ => (), // otherwise, continue onto the full, fields comparison
2777 // Grab a flattened representation of all fields.
2778 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2779 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2781 // Perform a structural comparison for each field.
2784 |&ty::FieldDef { did: a_did, .. },
2785 &ty::FieldDef { did: b_did, .. }| {
2786 structurally_same_type_impl(
2796 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2797 // For arrays, we also check the constness of the type.
2798 a_const.val == b_const.val
2799 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2801 (Slice(a_ty), Slice(b_ty)) => {
2802 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2804 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2805 a_tymut.mutbl == b_tymut.mutbl
2806 && structurally_same_type_impl(
2814 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2815 // For structural sameness, we don't need the region to be same.
2817 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2819 (FnDef(..), FnDef(..)) => {
2820 let a_poly_sig = a.fn_sig(tcx);
2821 let b_poly_sig = b.fn_sig(tcx);
2823 // As we don't compare regions, skip_binder is fine.
2824 let a_sig = a_poly_sig.skip_binder();
2825 let b_sig = b_poly_sig.skip_binder();
2827 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2828 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2829 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2830 structurally_same_type_impl(seen_types, cx, a, b, ckind)
2832 && structurally_same_type_impl(
2840 (Tuple(a_substs), Tuple(b_substs)) => {
2841 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2842 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2845 // For these, it's not quite as easy to define structural-sameness quite so easily.
2846 // For the purposes of this lint, take the conservative approach and mark them as
2847 // not structurally same.
2848 (Dynamic(..), Dynamic(..))
2849 | (Error(..), Error(..))
2850 | (Closure(..), Closure(..))
2851 | (Generator(..), Generator(..))
2852 | (GeneratorWitness(..), GeneratorWitness(..))
2853 | (Projection(..), Projection(..))
2854 | (Opaque(..), Opaque(..)) => false,
2856 // These definitely should have been caught above.
2857 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2859 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2860 // enum layout optimisation is being applied.
2861 (Adt(..), other_kind) | (other_kind, Adt(..))
2862 if is_primitive_or_pointer(other_kind) =>
2864 let (primitive, adt) =
2865 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2866 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2869 compare_layouts(a, b).unwrap_or(false)
2872 // Otherwise, just compare the layouts. This may fail to lint for some
2873 // incompatible types, but at the very least, will stop reads into
2874 // uninitialised memory.
2875 _ => compare_layouts(a, b).unwrap_or(false),
2880 let mut seen_types = FxHashSet::default();
2881 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2885 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2887 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2888 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2889 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2890 if let ForeignItemKind::Fn(..) = this_fi.kind {
2892 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2893 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2894 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2896 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2897 existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2899 // Check that the declarations match.
2900 if !Self::structurally_same_type(
2904 CItemKind::Declaration,
2906 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2907 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2909 // We want to ensure that we use spans for both decls that include where the
2910 // name was defined, whether that was from the link_name attribute or not.
2911 let get_relevant_span =
2912 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2913 SymbolName::Normal(_) => fi.span,
2914 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2916 // Finally, emit the diagnostic.
2917 tcx.struct_span_lint_hir(
2918 CLASHING_EXTERN_DECLARATIONS,
2920 get_relevant_span(this_fi),
2922 let mut expected_str = DiagnosticStyledString::new();
2923 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2924 let mut found_str = DiagnosticStyledString::new();
2925 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2927 lint.build(&format!(
2928 "`{}` redeclare{} with a different signature",
2930 if orig.get_name() == this_fi.ident.name {
2933 format!("s `{}`", orig.get_name())
2937 get_relevant_span(orig_fi),
2938 &format!("`{}` previously declared here", orig.get_name()),
2941 get_relevant_span(this_fi),
2942 "this signature doesn't match the previous declaration",
2944 .note_expected_found(&"", expected_str, &"", found_str)