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::layout::{LayoutError, LayoutOf};
45 use rustc_middle::ty::print::with_no_trimmed_paths;
46 use rustc_middle::ty::subst::{GenericArgKind, Subst};
47 use rustc_middle::ty::Instance;
48 use rustc_middle::ty::{self, Ty, TyCtxt};
49 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
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, InnerSpan, MultiSpan, Span};
54 use rustc_target::abi::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<'tcx>(&self, cx: &LateContext<'tcx>, span: Span, ty: Ty<'tcx>) {
157 for leaf in ty.walk(cx.tcx) {
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 attr.has_name(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::Trait { unsafety: 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::Impl { 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_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
421 if let ast::AssocItemKind::Fn(..) = it.kind {
422 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
423 self.report_overriden_symbol_name(
426 "declaration of a `no_mangle` method",
429 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
430 self.report_overriden_symbol_name(
433 "declaration of a method with `export_name`",
439 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
443 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
448 let msg = match ctxt {
449 FnCtxt::Foreign => return,
450 FnCtxt::Free => "declaration of an `unsafe` function",
451 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
452 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
454 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
460 /// The `missing_docs` lint detects missing documentation for public items.
464 /// ```rust,compile_fail
465 /// #![deny(missing_docs)]
473 /// This lint is intended to ensure that a library is well-documented.
474 /// Items without documentation can be difficult for users to understand
475 /// how to use properly.
477 /// This lint is "allow" by default because it can be noisy, and not all
478 /// projects may want to enforce everything to be documented.
481 "detects missing documentation for public members",
482 report_in_external_macro
485 pub struct MissingDoc {
486 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
487 doc_hidden_stack: Vec<bool>,
489 /// Private traits or trait items that leaked through. Don't check their methods.
490 private_traits: FxHashSet<hir::HirId>,
493 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
495 fn has_doc(attr: &ast::Attribute) -> bool {
496 if attr.is_doc_comment() {
500 if !attr.has_name(sym::doc) {
504 if attr.value_str().is_some() {
508 if let Some(list) = attr.meta_item_list() {
510 if meta.has_name(sym::hidden) {
520 pub fn new() -> MissingDoc {
521 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
524 fn doc_hidden(&self) -> bool {
525 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
528 fn check_missing_docs_attrs(
530 cx: &LateContext<'_>,
533 article: &'static str,
536 // If we're building a test harness, then warning about
537 // documentation is probably not really relevant right now.
538 if cx.sess().opts.test {
542 // `#[doc(hidden)]` disables missing_docs check.
543 if self.doc_hidden() {
547 // Only check publicly-visible items, using the result from the privacy pass.
548 // It's an option so the crate root can also use this function (it doesn't
550 if def_id != CRATE_DEF_ID {
551 if !cx.access_levels.is_exported(def_id) {
556 let attrs = cx.tcx.get_attrs(def_id.to_def_id());
557 let has_doc = attrs.iter().any(has_doc);
561 cx.tcx.sess.source_map().guess_head_span(sp),
563 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
570 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
571 fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
572 let doc_hidden = self.doc_hidden()
573 || attrs.iter().any(|attr| {
574 attr.has_name(sym::doc)
575 && match attr.meta_item_list() {
577 Some(l) => attr::list_contains_name(&l, sym::hidden),
580 self.doc_hidden_stack.push(doc_hidden);
583 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
584 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
587 fn check_crate(&mut self, cx: &LateContext<'_>) {
588 self.check_missing_docs_attrs(
591 cx.tcx.def_span(CRATE_DEF_ID),
597 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
599 hir::ItemKind::Trait(.., trait_item_refs) => {
600 // Issue #11592: traits are always considered exported, even when private.
601 if let hir::VisibilityKind::Inherited = it.vis.node {
602 self.private_traits.insert(it.hir_id());
603 for trait_item_ref in trait_item_refs {
604 self.private_traits.insert(trait_item_ref.id.hir_id());
609 hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref trait_ref), items, .. }) => {
610 // If the trait is private, add the impl items to `private_traits` so they don't get
611 // reported for missing docs.
612 let real_trait = trait_ref.path.res.def_id();
613 if let Some(def_id) = real_trait.as_local() {
614 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
615 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
616 if let hir::VisibilityKind::Inherited = item.vis.node {
617 for impl_item_ref in items {
618 self.private_traits.insert(impl_item_ref.id.hir_id());
626 hir::ItemKind::TyAlias(..)
627 | hir::ItemKind::Fn(..)
628 | hir::ItemKind::Macro(..)
629 | hir::ItemKind::Mod(..)
630 | hir::ItemKind::Enum(..)
631 | hir::ItemKind::Struct(..)
632 | hir::ItemKind::Union(..)
633 | hir::ItemKind::Const(..)
634 | hir::ItemKind::Static(..) => {}
639 let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
641 self.check_missing_docs_attrs(cx, it.def_id, it.span, article, desc);
644 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
645 if self.private_traits.contains(&trait_item.hir_id()) {
649 let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
651 self.check_missing_docs_attrs(cx, trait_item.def_id, trait_item.span, article, desc);
654 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
655 // If the method is an impl for a trait, don't doc.
656 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
660 // If the method is an impl for an item with docs_hidden, don't doc.
661 if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
662 let parent = cx.tcx.hir().get_parent_did(impl_item.hir_id());
663 let impl_ty = cx.tcx.type_of(parent);
664 let outerdef = match impl_ty.kind() {
665 ty::Adt(def, _) => Some(def.did),
666 ty::Foreign(def_id) => Some(*def_id),
669 let is_hidden = match outerdef {
670 Some(id) => cx.tcx.is_doc_hidden(id),
678 let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
679 self.check_missing_docs_attrs(cx, impl_item.def_id, impl_item.span, article, desc);
682 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
683 let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
684 self.check_missing_docs_attrs(cx, foreign_item.def_id, foreign_item.span, article, desc);
687 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
688 if !sf.is_positional() {
689 let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
690 self.check_missing_docs_attrs(cx, def_id, sf.span, "a", "struct field")
694 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
695 self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), v.span, "a", "variant");
700 /// The `missing_copy_implementations` lint detects potentially-forgotten
701 /// implementations of [`Copy`].
703 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
707 /// ```rust,compile_fail
708 /// #![deny(missing_copy_implementations)]
719 /// Historically (before 1.0), types were automatically marked as `Copy`
720 /// if possible. This was changed so that it required an explicit opt-in
721 /// by implementing the `Copy` trait. As part of this change, a lint was
722 /// added to alert if a copyable type was not marked `Copy`.
724 /// This lint is "allow" by default because this code isn't bad; it is
725 /// common to write newtypes like this specifically so that a `Copy` type
726 /// is no longer `Copy`. `Copy` types can result in unintended copies of
727 /// large data which can impact performance.
728 pub MISSING_COPY_IMPLEMENTATIONS,
730 "detects potentially-forgotten implementations of `Copy`"
733 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
735 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
736 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
737 if !cx.access_levels.is_reachable(item.def_id) {
740 let (def, ty) = match item.kind {
741 hir::ItemKind::Struct(_, ref ast_generics) => {
742 if !ast_generics.params.is_empty() {
745 let def = cx.tcx.adt_def(item.def_id);
746 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
748 hir::ItemKind::Union(_, ref ast_generics) => {
749 if !ast_generics.params.is_empty() {
752 let def = cx.tcx.adt_def(item.def_id);
753 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
755 hir::ItemKind::Enum(_, ref ast_generics) => {
756 if !ast_generics.params.is_empty() {
759 let def = cx.tcx.adt_def(item.def_id);
760 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
764 if def.has_dtor(cx.tcx) {
767 let param_env = ty::ParamEnv::empty();
768 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
771 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
772 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
774 "type could implement `Copy`; consider adding `impl \
784 /// The `missing_debug_implementations` lint detects missing
785 /// implementations of [`fmt::Debug`].
787 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
791 /// ```rust,compile_fail
792 /// #![deny(missing_debug_implementations)]
801 /// Having a `Debug` implementation on all types can assist with
802 /// debugging, as it provides a convenient way to format and display a
803 /// value. Using the `#[derive(Debug)]` attribute will automatically
804 /// generate a typical implementation, or a custom implementation can be
805 /// added by manually implementing the `Debug` trait.
807 /// This lint is "allow" by default because adding `Debug` to all types can
808 /// have a negative impact on compile time and code size. It also requires
809 /// boilerplate to be added to every type, which can be an impediment.
810 MISSING_DEBUG_IMPLEMENTATIONS,
812 "detects missing implementations of Debug"
816 pub struct MissingDebugImplementations {
817 impling_types: Option<LocalDefIdSet>,
820 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
822 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
823 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
824 if !cx.access_levels.is_reachable(item.def_id) {
829 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
833 let debug = match cx.tcx.get_diagnostic_item(sym::Debug) {
834 Some(debug) => debug,
838 if self.impling_types.is_none() {
839 let mut impls = LocalDefIdSet::default();
840 cx.tcx.for_each_impl(debug, |d| {
841 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
842 if let Some(def_id) = ty_def.did.as_local() {
843 impls.insert(def_id);
848 self.impling_types = Some(impls);
849 debug!("{:?}", self.impling_types);
852 if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
853 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
855 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
856 or a manual implementation",
857 cx.tcx.def_path_str(debug)
866 /// The `anonymous_parameters` lint detects anonymous parameters in trait
871 /// ```rust,edition2015,compile_fail
872 /// #![deny(anonymous_parameters)]
884 /// This syntax is mostly a historical accident, and can be worked around
885 /// quite easily by adding an `_` pattern or a descriptive identifier:
889 /// fn foo(_: usize);
893 /// This syntax is now a hard error in the 2018 edition. In the 2015
894 /// edition, this lint is "warn" by default. This lint
895 /// enables the [`cargo fix`] tool with the `--edition` flag to
896 /// automatically transition old code from the 2015 edition to 2018. The
897 /// tool will run this lint and automatically apply the
898 /// suggested fix from the compiler (which is to add `_` to each
899 /// parameter). This provides a completely automated way to update old
900 /// code for a new edition. See [issue #41686] for more details.
902 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
903 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
904 pub ANONYMOUS_PARAMETERS,
906 "detects anonymous parameters",
907 @future_incompatible = FutureIncompatibleInfo {
908 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
909 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
914 /// Checks for use of anonymous parameters (RFC 1685).
915 AnonymousParameters => [ANONYMOUS_PARAMETERS]
918 impl EarlyLintPass for AnonymousParameters {
919 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
920 if cx.sess.edition() != Edition::Edition2015 {
921 // This is a hard error in future editions; avoid linting and erroring
924 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
925 for arg in sig.decl.inputs.iter() {
926 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
927 if ident.name == kw::Empty {
928 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
929 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
931 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
932 (snip.as_str(), Applicability::MachineApplicable)
934 ("<type>", Applicability::HasPlaceholders)
938 "anonymous parameters are deprecated and will be \
939 removed in the next edition",
943 "try naming the parameter or explicitly \
945 format!("_: {}", ty_snip),
957 /// Check for use of attributes which have been deprecated.
959 pub struct DeprecatedAttr {
960 // This is not free to compute, so we want to keep it around, rather than
961 // compute it for every attribute.
962 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
965 impl_lint_pass!(DeprecatedAttr => []);
967 impl DeprecatedAttr {
968 pub fn new() -> DeprecatedAttr {
969 DeprecatedAttr { depr_attrs: deprecated_attributes() }
973 fn lint_deprecated_attr(
974 cx: &EarlyContext<'_>,
975 attr: &ast::Attribute,
977 suggestion: Option<&str>,
979 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
981 .span_suggestion_short(
983 suggestion.unwrap_or("remove this attribute"),
985 Applicability::MachineApplicable,
991 impl EarlyLintPass for DeprecatedAttr {
992 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
993 for &&(n, _, _, ref g) in &self.depr_attrs {
994 if attr.ident().map(|ident| ident.name) == Some(n) {
995 if let &AttributeGate::Gated(
996 Stability::Deprecated(link, suggestion),
1003 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
1004 lint_deprecated_attr(cx, attr, &msg, suggestion);
1009 if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
1010 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
1011 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
1012 lint_deprecated_attr(cx, attr, &msg, None);
1017 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1018 use rustc_ast::token::CommentKind;
1020 let mut attrs = attrs.iter().peekable();
1022 // Accumulate a single span for sugared doc comments.
1023 let mut sugared_span: Option<Span> = None;
1025 while let Some(attr) = attrs.next() {
1026 let is_doc_comment = attr.is_doc_comment();
1029 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1032 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1036 let span = sugared_span.take().unwrap_or(attr.span);
1038 if is_doc_comment || attr.has_name(sym::doc) {
1039 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1040 let mut err = lint.build("unused doc comment");
1043 format!("rustdoc does not generate documentation for {}", node_kind),
1046 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1047 err.help("use `//` for a plain comment");
1049 AttrKind::DocComment(CommentKind::Block, _) => {
1050 err.help("use `/* */` for a plain comment");
1059 impl EarlyLintPass for UnusedDocComment {
1060 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1061 let kind = match stmt.kind {
1062 ast::StmtKind::Local(..) => "statements",
1063 // Disabled pending discussion in #78306
1064 ast::StmtKind::Item(..) => return,
1065 // expressions will be reported by `check_expr`.
1066 ast::StmtKind::Empty
1067 | ast::StmtKind::Semi(_)
1068 | ast::StmtKind::Expr(_)
1069 | ast::StmtKind::MacCall(_) => return,
1072 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1075 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1076 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1077 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1080 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1081 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1086 /// The `no_mangle_const_items` lint detects any `const` items with the
1087 /// [`no_mangle` attribute].
1089 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1093 /// ```rust,compile_fail
1095 /// const FOO: i32 = 5;
1102 /// Constants do not have their symbols exported, and therefore, this
1103 /// probably means you meant to use a [`static`], not a [`const`].
1105 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1106 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1107 NO_MANGLE_CONST_ITEMS,
1109 "const items will not have their symbols exported"
1113 /// The `no_mangle_generic_items` lint detects generic items that must be
1120 /// fn foo<T>(t: T) {
1129 /// A function with generics must have its symbol mangled to accommodate
1130 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1131 /// this situation, and should be removed.
1133 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1134 NO_MANGLE_GENERIC_ITEMS,
1136 "generic items must be mangled"
1139 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1141 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1142 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1143 let attrs = cx.tcx.hir().attrs(it.hir_id());
1144 let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1145 impl_generics: Option<&hir::Generics<'_>>,
1146 generics: &hir::Generics<'_>,
1149 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1152 GenericParamKind::Lifetime { .. } => {}
1153 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1154 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
1155 lint.build("functions generic over types or consts must be mangled")
1156 .span_suggestion_short(
1157 no_mangle_attr.span,
1158 "remove this attribute",
1160 // Use of `#[no_mangle]` suggests FFI intent; correct
1161 // fix may be to monomorphize source by hand
1162 Applicability::MaybeIncorrect,
1172 hir::ItemKind::Fn(.., ref generics, _) => {
1173 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1174 check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1177 hir::ItemKind::Const(..) => {
1178 if cx.sess().contains_name(attrs, sym::no_mangle) {
1179 // Const items do not refer to a particular location in memory, and therefore
1180 // don't have anything to attach a symbol to
1181 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1182 let msg = "const items should never be `#[no_mangle]`";
1183 let mut err = lint.build(msg);
1185 // account for "pub const" (#45562)
1190 .span_to_snippet(it.span)
1191 .map(|snippet| snippet.find("const").unwrap_or(0))
1192 .unwrap_or(0) as u32;
1193 // `const` is 5 chars
1194 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1195 err.span_suggestion(
1197 "try a static value",
1198 "pub static".to_owned(),
1199 Applicability::MachineApplicable,
1205 hir::ItemKind::Impl(hir::Impl { ref generics, items, .. }) => {
1207 if let hir::AssocItemKind::Fn { .. } = it.kind {
1208 if let Some(no_mangle_attr) = cx
1210 .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1212 check_no_mangle_on_generic_fn(
1215 cx.tcx.hir().get_generics(it.id.def_id.to_def_id()).unwrap(),
1228 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1229 /// T` because it is [undefined behavior].
1231 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1235 /// ```rust,compile_fail
1237 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1245 /// Certain assumptions are made about aliasing of data, and this transmute
1246 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1248 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1251 "mutating transmuted &mut T from &T may cause undefined behavior"
1254 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1256 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1257 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1258 use rustc_target::spec::abi::Abi::RustIntrinsic;
1259 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1260 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1262 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1263 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1264 consider instead using an UnsafeCell";
1265 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
1269 fn get_transmute_from_to<'tcx>(
1270 cx: &LateContext<'tcx>,
1271 expr: &hir::Expr<'_>,
1272 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1273 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1274 cx.qpath_res(qpath, expr.hir_id)
1278 if let Res::Def(DefKind::Fn, did) = def {
1279 if !def_id_is_transmute(cx, did) {
1282 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1283 let from = sig.inputs().skip_binder()[0];
1284 let to = sig.output().skip_binder();
1285 return Some((from, to));
1290 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1291 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
1292 && cx.tcx.item_name(def_id) == sym::transmute
1298 /// The `unstable_features` is deprecated and should no longer be used.
1301 "enabling unstable features (deprecated. do not use)"
1305 /// Forbids using the `#[feature(...)]` attribute
1306 UnstableFeatures => [UNSTABLE_FEATURES]
1309 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1310 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1311 if attr.has_name(sym::feature) {
1312 if let Some(items) = attr.meta_item_list() {
1314 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1315 lint.build("unstable feature").emit()
1324 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1329 /// ```rust,compile_fail
1330 /// #![deny(unreachable_pub)]
1342 /// A bare `pub` visibility may be misleading if the item is not actually
1343 /// publicly exported from the crate. The `pub(crate)` visibility is
1344 /// recommended to be used instead, which more clearly expresses the intent
1345 /// that the item is only visible within its own crate.
1347 /// This lint is "allow" by default because it will trigger for a large
1348 /// amount existing Rust code, and has some false-positives. Eventually it
1349 /// is desired for this to become warn-by-default.
1350 pub UNREACHABLE_PUB,
1352 "`pub` items not reachable from crate root"
1356 /// Lint for items marked `pub` that aren't reachable from other crates.
1357 UnreachablePub => [UNREACHABLE_PUB]
1360 impl UnreachablePub {
1363 cx: &LateContext<'_>,
1366 vis: &hir::Visibility<'_>,
1370 let mut applicability = Applicability::MachineApplicable;
1372 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(def_id) => {
1373 if span.from_expansion() {
1374 applicability = Applicability::MaybeIncorrect;
1376 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1377 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1378 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1379 let replacement = if cx.tcx.features().crate_visibility_modifier {
1386 err.span_suggestion(
1388 "consider restricting its visibility",
1393 err.help("or consider exporting it for use by other crates");
1403 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1404 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1405 self.perform_lint(cx, "item", item.def_id, &item.vis, item.span, true);
1408 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1412 foreign_item.def_id,
1419 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1420 let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1421 self.perform_lint(cx, "field", def_id, &field.vis, field.span, false);
1424 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1425 self.perform_lint(cx, "item", impl_item.def_id, &impl_item.vis, impl_item.span, false);
1430 /// The `type_alias_bounds` lint detects bounds in type aliases.
1435 /// type SendVec<T: Send> = Vec<T>;
1442 /// The trait bounds in a type alias are currently ignored, and should not
1443 /// be included to avoid confusion. This was previously allowed
1444 /// unintentionally; this may become a hard error in the future.
1447 "bounds in type aliases are not enforced"
1451 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1452 /// They are relevant when using associated types, but otherwise neither checked
1453 /// at definition site nor enforced at use site.
1454 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1457 impl TypeAliasBounds {
1458 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1460 hir::QPath::TypeRelative(ref ty, _) => {
1461 // If this is a type variable, we found a `T::Assoc`.
1463 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1464 matches!(path.res, Res::Def(DefKind::TyParam, _))
1469 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1473 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1474 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1475 // bound. Let's see if this type does that.
1477 // We use a HIR visitor to walk the type.
1478 use rustc_hir::intravisit::{self, Visitor};
1479 struct WalkAssocTypes<'a, 'db> {
1480 err: &'a mut DiagnosticBuilder<'db>,
1482 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1483 type Map = intravisit::ErasedMap<'v>;
1485 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1486 intravisit::NestedVisitorMap::None
1489 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1490 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1493 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1494 associated types in type aliases",
1497 intravisit::walk_qpath(self, qpath, id, span)
1501 // Let's go for a walk!
1502 let mut visitor = WalkAssocTypes { err };
1503 visitor.visit_ty(ty);
1507 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1508 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1509 let (ty, type_alias_generics) = match item.kind {
1510 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1513 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1514 // Bounds are respected for `type X = impl Trait`
1517 let mut suggested_changing_assoc_types = false;
1518 // There must not be a where clause
1519 if !type_alias_generics.where_clause.predicates.is_empty() {
1523 let mut err = lint.build("where clauses are not enforced in type aliases");
1524 let spans: Vec<_> = type_alias_generics
1528 .map(|pred| pred.span())
1530 err.set_span(spans);
1531 err.span_suggestion(
1532 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1533 "the clause will not be checked when the type alias is used, and should be removed",
1535 Applicability::MachineApplicable,
1537 if !suggested_changing_assoc_types {
1538 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1539 suggested_changing_assoc_types = true;
1545 // The parameters must not have bounds
1546 for param in type_alias_generics.params.iter() {
1547 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1548 let suggestion = spans
1551 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1552 (start.to(*sp), String::new())
1555 if !spans.is_empty() {
1556 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1558 lint.build("bounds on generic parameters are not enforced in type aliases");
1559 let msg = "the bound will not be checked when the type alias is used, \
1560 and should be removed";
1561 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1562 if !suggested_changing_assoc_types {
1563 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1564 suggested_changing_assoc_types = true;
1574 /// Lint constants that are erroneous.
1575 /// Without this lint, we might not get any diagnostic if the constant is
1576 /// unused within this crate, even though downstream crates can't use it
1577 /// without producing an error.
1578 UnusedBrokenConst => []
1581 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1582 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1584 hir::ItemKind::Const(_, body_id) => {
1585 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1586 // trigger the query once for all constants since that will already report the errors
1587 // FIXME: Use ensure here
1588 let _ = cx.tcx.const_eval_poly(def_id);
1590 hir::ItemKind::Static(_, _, body_id) => {
1591 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1592 // FIXME: Use ensure here
1593 let _ = cx.tcx.eval_static_initializer(def_id);
1601 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1602 /// any type parameters.
1607 /// #![feature(trivial_bounds)]
1608 /// pub struct A where i32: Copy;
1615 /// Usually you would not write a trait bound that you know is always
1616 /// true, or never true. However, when using macros, the macro may not
1617 /// know whether or not the constraint would hold or not at the time when
1618 /// generating the code. Currently, the compiler does not alert you if the
1619 /// constraint is always true, and generates an error if it is never true.
1620 /// The `trivial_bounds` feature changes this to be a warning in both
1621 /// cases, giving macros more freedom and flexibility to generate code,
1622 /// while still providing a signal when writing non-macro code that
1623 /// something is amiss.
1625 /// See [RFC 2056] for more details. This feature is currently only
1626 /// available on the nightly channel, see [tracking issue #48214].
1628 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1629 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1632 "these bounds don't depend on an type parameters"
1636 /// Lint for trait and lifetime bounds that don't depend on type parameters
1637 /// which either do nothing, or stop the item from being used.
1638 TrivialConstraints => [TRIVIAL_BOUNDS]
1641 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1642 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1643 use rustc_middle::ty::fold::TypeFoldable;
1644 use rustc_middle::ty::PredicateKind::*;
1646 if cx.tcx.features().trivial_bounds {
1647 let predicates = cx.tcx.predicates_of(item.def_id);
1648 for &(predicate, span) in predicates.predicates {
1649 let predicate_kind_name = match predicate.kind().skip_binder() {
1650 Trait(..) => "trait",
1652 RegionOutlives(..) => "lifetime",
1654 // Ignore projections, as they can only be global
1655 // if the trait bound is global
1657 // Ignore bounds that a user can't type
1663 ConstEvaluatable(..) |
1665 TypeWellFormedFromEnv(..) => continue,
1667 if predicate.is_global(cx.tcx) {
1668 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1669 lint.build(&format!(
1670 "{} bound {} does not depend on any type \
1671 or lifetime parameters",
1672 predicate_kind_name, predicate
1683 /// Does nothing as a lint pass, but registers some `Lint`s
1684 /// which are used by other parts of the compiler.
1688 NON_SHORTHAND_FIELD_PATTERNS,
1691 MISSING_COPY_IMPLEMENTATIONS,
1692 MISSING_DEBUG_IMPLEMENTATIONS,
1693 ANONYMOUS_PARAMETERS,
1694 UNUSED_DOC_COMMENTS,
1695 NO_MANGLE_CONST_ITEMS,
1696 NO_MANGLE_GENERIC_ITEMS,
1706 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1707 /// pattern], which is deprecated.
1709 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1713 /// ```rust,edition2018
1725 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1726 /// confusion with the [`..` range expression]. Use the new form instead.
1728 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1729 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1731 "`...` range patterns are deprecated",
1732 @future_incompatible = FutureIncompatibleInfo {
1733 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1734 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1739 pub struct EllipsisInclusiveRangePatterns {
1740 /// If `Some(_)`, suppress all subsequent pattern
1741 /// warnings for better diagnostics.
1742 node_id: Option<ast::NodeId>,
1745 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1747 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1748 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1749 if self.node_id.is_some() {
1750 // Don't recursively warn about patterns inside range endpoints.
1754 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1756 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1757 /// corresponding to the ellipsis.
1758 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1763 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1764 ) => Some((a.as_deref(), b, *span)),
1769 let (parenthesise, endpoints) = match &pat.kind {
1770 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1771 _ => (false, matches_ellipsis_pat(pat)),
1774 if let Some((start, end, join)) = endpoints {
1775 let msg = "`...` range patterns are deprecated";
1776 let suggestion = "use `..=` for an inclusive range";
1778 self.node_id = Some(pat.id);
1779 let end = expr_to_string(&end);
1780 let replace = match start {
1781 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1782 None => format!("&(..={})", end),
1784 if join.edition() >= Edition::Edition2021 {
1786 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1787 err.span_suggestion(
1791 Applicability::MachineApplicable,
1795 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1801 Applicability::MachineApplicable,
1807 let replace = "..=".to_owned();
1808 if join.edition() >= Edition::Edition2021 {
1810 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1811 err.span_suggestion_short(
1815 Applicability::MachineApplicable,
1819 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1821 .span_suggestion_short(
1825 Applicability::MachineApplicable,
1834 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1835 if let Some(node_id) = self.node_id {
1836 if pat.id == node_id {
1844 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1845 /// that are not able to be run by the test harness because they are in a
1846 /// position where they are not nameable.
1848 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1856 /// // This test will not fail because it does not run.
1857 /// assert_eq!(1, 2);
1866 /// In order for the test harness to run a test, the test function must be
1867 /// located in a position where it can be accessed from the crate root.
1868 /// This generally means it must be defined in a module, and not anywhere
1869 /// else such as inside another function. The compiler previously allowed
1870 /// this without an error, so a lint was added as an alert that a test is
1871 /// not being used. Whether or not this should be allowed has not yet been
1872 /// decided, see [RFC 2471] and [issue #36629].
1874 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1875 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1876 UNNAMEABLE_TEST_ITEMS,
1878 "detects an item that cannot be named being marked as `#[test_case]`",
1879 report_in_external_macro
1882 pub struct UnnameableTestItems {
1883 boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1884 items_nameable: bool,
1887 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1889 impl UnnameableTestItems {
1890 pub fn new() -> Self {
1891 Self { boundary: None, items_nameable: true }
1895 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1896 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1897 if self.items_nameable {
1898 if let hir::ItemKind::Mod(..) = it.kind {
1900 self.items_nameable = false;
1901 self.boundary = Some(it.def_id);
1906 let attrs = cx.tcx.hir().attrs(it.hir_id());
1907 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1908 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1909 lint.build("cannot test inner items").emit()
1914 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1915 if !self.items_nameable && self.boundary == Some(it.def_id) {
1916 self.items_nameable = true;
1922 /// The `keyword_idents` lint detects edition keywords being used as an
1927 /// ```rust,edition2015,compile_fail
1928 /// #![deny(keyword_idents)]
1937 /// Rust [editions] allow the language to evolve without breaking
1938 /// backwards compatibility. This lint catches code that uses new keywords
1939 /// that are added to the language that are used as identifiers (such as a
1940 /// variable name, function name, etc.). If you switch the compiler to a
1941 /// new edition without updating the code, then it will fail to compile if
1942 /// you are using a new keyword as an identifier.
1944 /// You can manually change the identifiers to a non-keyword, or use a
1945 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1947 /// This lint solves the problem automatically. It is "allow" by default
1948 /// because the code is perfectly valid in older editions. The [`cargo
1949 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1950 /// and automatically apply the suggested fix from the compiler (which is
1951 /// to use a raw identifier). This provides a completely automated way to
1952 /// update old code for a new edition.
1954 /// [editions]: https://doc.rust-lang.org/edition-guide/
1955 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1956 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1959 "detects edition keywords being used as an identifier",
1960 @future_incompatible = FutureIncompatibleInfo {
1961 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1962 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1967 /// Check for uses of edition keywords used as an identifier.
1968 KeywordIdents => [KEYWORD_IDENTS]
1971 struct UnderMacro(bool);
1973 impl KeywordIdents {
1974 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1975 for tt in tokens.into_trees() {
1977 // Only report non-raw idents.
1978 TokenTree::Token(token) => {
1979 if let Some((ident, false)) = token.ident() {
1980 self.check_ident_token(cx, UnderMacro(true), ident);
1983 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1988 fn check_ident_token(
1990 cx: &EarlyContext<'_>,
1991 UnderMacro(under_macro): UnderMacro,
1994 let next_edition = match cx.sess.edition() {
1995 Edition::Edition2015 => {
1997 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1999 // rust-lang/rust#56327: Conservatively do not
2000 // attempt to report occurrences of `dyn` within
2001 // macro definitions or invocations, because `dyn`
2002 // can legitimately occur as a contextual keyword
2003 // in 2015 code denoting its 2018 meaning, and we
2004 // do not want rustfix to inject bugs into working
2005 // code by rewriting such occurrences.
2007 // But if we see `dyn` outside of a macro, we know
2008 // its precise role in the parsed AST and thus are
2009 // assured this is truly an attempt to use it as
2011 kw::Dyn if !under_macro => Edition::Edition2018,
2017 // There are no new keywords yet for the 2018 edition and beyond.
2021 // Don't lint `r#foo`.
2022 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2026 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2027 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
2030 "you can use a raw identifier to stay compatible",
2031 format!("r#{}", ident),
2032 Applicability::MachineApplicable,
2039 impl EarlyLintPass for KeywordIdents {
2040 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2041 self.check_tokens(cx, mac_def.body.inner_tokens());
2043 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2044 self.check_tokens(cx, mac.args.inner_tokens());
2046 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2047 self.check_ident_token(cx, UnderMacro(false), ident);
2051 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2053 impl ExplicitOutlivesRequirements {
2054 fn lifetimes_outliving_lifetime<'tcx>(
2055 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2057 ) -> Vec<ty::Region<'tcx>> {
2060 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2061 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
2062 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2070 fn lifetimes_outliving_type<'tcx>(
2071 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2073 ) -> Vec<ty::Region<'tcx>> {
2076 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2077 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2078 a.is_param(index).then_some(b)
2085 fn collect_outlived_lifetimes<'tcx>(
2087 param: &'tcx hir::GenericParam<'tcx>,
2089 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2090 ty_generics: &'tcx ty::Generics,
2091 ) -> Vec<ty::Region<'tcx>> {
2093 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
2096 hir::GenericParamKind::Lifetime { .. } => {
2097 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
2099 hir::GenericParamKind::Type { .. } => {
2100 Self::lifetimes_outliving_type(inferred_outlives, index)
2102 hir::GenericParamKind::Const { .. } => Vec::new(),
2106 fn collect_outlives_bound_spans<'tcx>(
2109 bounds: &hir::GenericBounds<'_>,
2110 inferred_outlives: &[ty::Region<'tcx>],
2112 ) -> Vec<(usize, Span)> {
2113 use rustc_middle::middle::resolve_lifetime::Region;
2118 .filter_map(|(i, bound)| {
2119 if let hir::GenericBound::Outlives(lifetime) = bound {
2120 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2121 Some(Region::Static) if infer_static => {
2122 inferred_outlives.iter().any(|r| matches!(r, ty::ReStatic))
2124 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2125 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
2129 is_inferred.then_some((i, bound.span()))
2137 fn consolidate_outlives_bound_spans(
2140 bounds: &hir::GenericBounds<'_>,
2141 bound_spans: Vec<(usize, Span)>,
2143 if bounds.is_empty() {
2146 if bound_spans.len() == bounds.len() {
2147 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2148 // If all bounds are inferable, we want to delete the colon, so
2149 // start from just after the parameter (span passed as argument)
2150 vec![lo.to(last_bound_span)]
2152 let mut merged = Vec::new();
2153 let mut last_merged_i = None;
2155 let mut from_start = true;
2156 for (i, bound_span) in bound_spans {
2157 match last_merged_i {
2158 // If the first bound is inferable, our span should also eat the leading `+`.
2160 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2161 last_merged_i = Some(0);
2163 // If consecutive bounds are inferable, merge their spans
2164 Some(h) if i == h + 1 => {
2165 if let Some(tail) = merged.last_mut() {
2166 // Also eat the trailing `+` if the first
2167 // more-than-one bound is inferable
2168 let to_span = if from_start && i < bounds.len() {
2169 bounds[i + 1].span().shrink_to_lo()
2173 *tail = tail.to(to_span);
2174 last_merged_i = Some(i);
2176 bug!("another bound-span visited earlier");
2180 // When we find a non-inferable bound, subsequent inferable bounds
2181 // won't be consecutive from the start (and we'll eat the leading
2182 // `+` rather than the trailing one)
2184 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2185 last_merged_i = Some(i);
2194 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2195 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2196 use rustc_middle::middle::resolve_lifetime::Region;
2198 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
2199 let def_id = item.def_id;
2200 if let hir::ItemKind::Struct(_, ref hir_generics)
2201 | hir::ItemKind::Enum(_, ref hir_generics)
2202 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2204 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2205 if inferred_outlives.is_empty() {
2209 let ty_generics = cx.tcx.generics_of(def_id);
2211 let mut bound_count = 0;
2212 let mut lint_spans = Vec::new();
2214 for param in hir_generics.params {
2215 let has_lifetime_bounds = param
2218 .any(|bound| matches!(bound, hir::GenericBound::Outlives(_)));
2219 if !has_lifetime_bounds {
2223 let relevant_lifetimes =
2224 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
2225 if relevant_lifetimes.is_empty() {
2229 let bound_spans = self.collect_outlives_bound_spans(
2232 &relevant_lifetimes,
2235 bound_count += bound_spans.len();
2236 lint_spans.extend(self.consolidate_outlives_bound_spans(
2237 param.span.shrink_to_hi(),
2243 let mut where_lint_spans = Vec::new();
2244 let mut dropped_predicate_count = 0;
2245 let num_predicates = hir_generics.where_clause.predicates.len();
2246 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
2247 let (relevant_lifetimes, bounds, span) = match where_predicate {
2248 hir::WherePredicate::RegionPredicate(predicate) => {
2249 if let Some(Region::EarlyBound(index, ..)) =
2250 cx.tcx.named_region(predicate.lifetime.hir_id)
2253 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2261 hir::WherePredicate::BoundPredicate(predicate) => {
2262 // FIXME we can also infer bounds on associated types,
2263 // and should check for them here.
2264 match predicate.bounded_ty.kind {
2265 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2266 if let Res::Def(DefKind::TyParam, def_id) = path.res {
2267 let index = ty_generics.param_def_id_to_index[&def_id];
2269 Self::lifetimes_outliving_type(inferred_outlives, index),
2284 if relevant_lifetimes.is_empty() {
2288 let bound_spans = self.collect_outlives_bound_spans(
2291 &relevant_lifetimes,
2294 bound_count += bound_spans.len();
2296 let drop_predicate = bound_spans.len() == bounds.len();
2298 dropped_predicate_count += 1;
2301 // If all the bounds on a predicate were inferable and there are
2302 // further predicates, we want to eat the trailing comma.
2303 if drop_predicate && i + 1 < num_predicates {
2304 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
2305 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2307 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2308 span.shrink_to_lo(),
2315 // If all predicates are inferable, drop the entire clause
2316 // (including the `where`)
2317 if num_predicates > 0 && dropped_predicate_count == num_predicates {
2318 let where_span = hir_generics
2321 .expect("span of (nonempty) where clause should exist");
2322 // Extend the where clause back to the closing `>` of the
2323 // generics, except for tuple struct, which have the `where`
2324 // after the fields of the struct.
2325 let full_where_span =
2326 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2329 hir_generics.span.shrink_to_hi().to(where_span)
2331 lint_spans.push(full_where_span);
2333 lint_spans.extend(where_lint_spans);
2336 if !lint_spans.is_empty() {
2337 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2338 lint.build("outlives requirements can be inferred")
2339 .multipart_suggestion(
2340 if bound_count == 1 {
2343 "remove these bounds"
2347 .map(|span| (span, "".to_owned()))
2348 .collect::<Vec<_>>(),
2349 Applicability::MachineApplicable,
2359 /// The `incomplete_features` lint detects unstable features enabled with
2360 /// the [`feature` attribute] that may function improperly in some or all
2363 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2368 /// #![feature(generic_const_exprs)]
2375 /// Although it is encouraged for people to experiment with unstable
2376 /// features, some of them are known to be incomplete or faulty. This lint
2377 /// is a signal that the feature has not yet been finished, and you may
2378 /// experience problems with it.
2379 pub INCOMPLETE_FEATURES,
2381 "incomplete features that may function improperly in some or all cases"
2385 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2386 IncompleteFeatures => [INCOMPLETE_FEATURES]
2389 impl EarlyLintPass for IncompleteFeatures {
2390 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2391 let features = cx.sess.features_untracked();
2393 .declared_lang_features
2395 .map(|(name, span, _)| (name, span))
2396 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2397 .filter(|(&name, _)| features.incomplete(name))
2398 .for_each(|(&name, &span)| {
2399 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2400 let mut builder = lint.build(&format!(
2401 "the feature `{}` is incomplete and may not be safe to use \
2402 and/or cause compiler crashes",
2405 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2406 builder.note(&format!(
2407 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
2408 for more information",
2412 if HAS_MIN_FEATURES.contains(&name) {
2413 builder.help(&format!(
2414 "consider using `min_{}` instead, which is more stable and complete",
2424 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2427 /// The `invalid_value` lint detects creating a value that is not valid,
2428 /// such as a null reference.
2433 /// # #![allow(unused)]
2435 /// let x: &'static i32 = std::mem::zeroed();
2443 /// In some situations the compiler can detect that the code is creating
2444 /// an invalid value, which should be avoided.
2446 /// In particular, this lint will check for improper use of
2447 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2448 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2449 /// lint should provide extra information to indicate what the problem is
2450 /// and a possible solution.
2452 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2453 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2454 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2455 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2456 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2459 "an invalid value is being created (such as a null reference)"
2462 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2464 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2465 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2466 #[derive(Debug, Copy, Clone, PartialEq)]
2472 /// Information about why a type cannot be initialized this way.
2473 /// Contains an error message and optionally a span to point at.
2474 type InitError = (String, Option<Span>);
2476 /// Test if this constant is all-0.
2477 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2478 use hir::ExprKind::*;
2479 use rustc_ast::LitKind::*;
2482 if let Int(i, _) = lit.node {
2488 Tup(tup) => tup.iter().all(is_zero),
2493 /// Determine if this expression is a "dangerous initialization".
2494 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2495 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2496 // Find calls to `mem::{uninitialized,zeroed}` methods.
2497 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2498 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2499 match cx.tcx.get_diagnostic_name(def_id) {
2500 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2501 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2502 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2506 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
2507 // Find problematic calls to `MaybeUninit::assume_init`.
2508 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2509 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2510 // This is a call to *some* method named `assume_init`.
2511 // See if the `self` parameter is one of the dangerous constructors.
2512 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2513 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2514 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2515 match cx.tcx.get_diagnostic_name(def_id) {
2516 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2517 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2528 /// Test if this enum has several actually "existing" variants.
2529 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2530 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
2531 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2532 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
2533 existing_variants > 1
2536 /// Return `Some` only if we are sure this type does *not*
2537 /// allow zero initialization.
2538 fn ty_find_init_error<'tcx>(
2542 ) -> Option<InitError> {
2543 use rustc_middle::ty::TyKind::*;
2545 // Primitive types that don't like 0 as a value.
2546 Ref(..) => Some(("references must be non-null".to_string(), None)),
2547 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2548 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2549 Never => Some(("the `!` type has no valid value".to_string(), None)),
2550 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2551 // raw ptr to dyn Trait
2553 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2555 // Primitive types with other constraints.
2556 Bool if init == InitKind::Uninit => {
2557 Some(("booleans must be either `true` or `false`".to_string(), None))
2559 Char if init == InitKind::Uninit => {
2560 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2562 // Recurse and checks for some compound types.
2563 Adt(adt_def, substs) if !adt_def.is_union() => {
2564 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2565 use std::ops::Bound;
2566 match tcx.layout_scalar_valid_range(adt_def.did) {
2567 // We exploit here that `layout_scalar_valid_range` will never
2568 // return `Bound::Excluded`. (And we have tests checking that we
2569 // handle the attribute correctly.)
2570 (Bound::Included(lo), _) if lo > 0 => {
2571 return Some((format!("`{}` must be non-null", ty), None));
2573 (Bound::Included(_), _) | (_, Bound::Included(_))
2574 if init == InitKind::Uninit =>
2578 "`{}` must be initialized inside its custom valid range",
2587 match adt_def.variants.len() {
2588 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2590 // Struct, or enum with exactly one variant.
2591 // Proceed recursively, check all fields.
2592 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2593 variant.fields.iter().find_map(|field| {
2594 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2597 // Point to this field, should be helpful for figuring
2598 // out where the source of the error is.
2599 let span = tcx.def_span(field.did);
2602 " (in this {} field)",
2615 // Multi-variant enum.
2617 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2618 let span = tcx.def_span(adt_def.did);
2620 "enums have to be initialized to a variant".to_string(),
2624 // In principle, for zero-initialization we could figure out which variant corresponds
2625 // to tag 0, and check that... but for now we just accept all zero-initializations.
2632 // Proceed recursively, check all fields.
2633 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2635 // Conservative fallback.
2640 if let Some(init) = is_dangerous_init(cx, expr) {
2641 // This conjures an instance of a type out of nothing,
2642 // using zeroed or uninitialized memory.
2643 // We are extremely conservative with what we warn about.
2644 let conjured_ty = cx.typeck_results().expr_ty(expr);
2645 if let Some((msg, span)) =
2646 with_no_trimmed_paths(|| ty_find_init_error(cx.tcx, conjured_ty, init))
2648 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2649 let mut err = lint.build(&format!(
2650 "the type `{}` does not permit {}",
2653 InitKind::Zeroed => "zero-initialization",
2654 InitKind::Uninit => "being left uninitialized",
2657 err.span_label(expr.span, "this code causes undefined behavior when executed");
2660 "help: use `MaybeUninit<T>` instead, \
2661 and only call `assume_init` after initialization is done",
2663 if let Some(span) = span {
2664 err.span_note(span, &msg);
2676 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2677 /// has been declared with the same name but different types.
2697 /// Because two symbols of the same name cannot be resolved to two
2698 /// different functions at link time, and one function cannot possibly
2699 /// have two types, a clashing extern declaration is almost certainly a
2700 /// mistake. Check to make sure that the `extern` definitions are correct
2701 /// and equivalent, and possibly consider unifying them in one location.
2703 /// This lint does not run between crates because a project may have
2704 /// dependencies which both rely on the same extern function, but declare
2705 /// it in a different (but valid) way. For example, they may both declare
2706 /// an opaque type for one or more of the arguments (which would end up
2707 /// distinct types), or use types that are valid conversions in the
2708 /// language the `extern fn` is defined in. In these cases, the compiler
2709 /// can't say that the clashing declaration is incorrect.
2710 pub CLASHING_EXTERN_DECLARATIONS,
2712 "detects when an extern fn has been declared with the same name but different types"
2715 pub struct ClashingExternDeclarations {
2716 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2717 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2718 /// the symbol should be reported as a clashing declaration.
2719 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2720 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2721 seen_decls: FxHashMap<Symbol, HirId>,
2724 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2725 /// just from declaration itself. This is important because we don't want to report clashes on
2726 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2729 /// The name of the symbol + the span of the annotation which introduced the link name.
2731 /// No link name, so just the name of the symbol.
2736 fn get_name(&self) -> Symbol {
2738 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2743 impl ClashingExternDeclarations {
2744 crate fn new() -> Self {
2745 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2747 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2748 /// for the item, return its HirId without updating the set.
2749 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2750 let did = fi.def_id.to_def_id();
2751 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2752 let name = Symbol::intern(tcx.symbol_name(instance).name);
2753 if let Some(&hir_id) = self.seen_decls.get(&name) {
2754 // Avoid updating the map with the new entry when we do find a collision. We want to
2755 // make sure we're always pointing to the first definition as the previous declaration.
2756 // This lets us avoid emitting "knock-on" diagnostics.
2759 self.seen_decls.insert(name, fi.hir_id())
2763 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2764 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2766 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2767 if let Some((overridden_link_name, overridden_link_name_span)) =
2768 tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2769 // FIXME: Instead of searching through the attributes again to get span
2770 // information, we could have codegen_fn_attrs also give span information back for
2771 // where the attribute was defined. However, until this is found to be a
2772 // bottleneck, this does just fine.
2774 overridden_link_name,
2775 tcx.get_attrs(fi.def_id.to_def_id())
2777 .find(|at| at.has_name(sym::link_name))
2783 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2785 SymbolName::Normal(fi.ident.name)
2789 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2790 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2791 /// with the same members (as the declarations shouldn't clash).
2792 fn structurally_same_type<'tcx>(
2793 cx: &LateContext<'tcx>,
2798 fn structurally_same_type_impl<'tcx>(
2799 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2800 cx: &LateContext<'tcx>,
2805 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2808 // Given a transparent newtype, reach through and grab the inner
2809 // type unless the newtype makes the type non-null.
2810 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2813 if let ty::Adt(def, substs) = *ty.kind() {
2814 let is_transparent = def.subst(tcx, substs).repr.transparent();
2815 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, &def);
2817 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2818 ty, is_transparent, is_non_null
2820 if is_transparent && !is_non_null {
2821 debug_assert!(def.variants.len() == 1);
2822 let v = &def.variants[VariantIdx::new(0)];
2823 ty = transparent_newtype_field(tcx, v)
2825 "single-variant transparent structure with zero-sized field",
2831 debug!("non_transparent_ty -> {:?}", ty);
2836 let a = non_transparent_ty(a);
2837 let b = non_transparent_ty(b);
2839 if !seen_types.insert((a, b)) {
2840 // We've encountered a cycle. There's no point going any further -- the types are
2841 // structurally the same.
2845 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2846 // All nominally-same types are structurally same, too.
2849 // Do a full, depth-first comparison between the two.
2850 use rustc_middle::ty::TyKind::*;
2851 let a_kind = a.kind();
2852 let b_kind = b.kind();
2854 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2855 debug!("compare_layouts({:?}, {:?})", a, b);
2856 let a_layout = &cx.layout_of(a)?.layout.abi;
2857 let b_layout = &cx.layout_of(b)?.layout.abi;
2859 "comparing layouts: {:?} == {:?} = {}",
2862 a_layout == b_layout
2864 Ok(a_layout == b_layout)
2867 #[allow(rustc::usage_of_ty_tykind)]
2868 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2869 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2872 ensure_sufficient_stack(|| {
2873 match (a_kind, b_kind) {
2874 (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2875 let a = a.subst(cx.tcx, a_substs);
2876 let b = b.subst(cx.tcx, b_substs);
2877 debug!("Comparing {:?} and {:?}", a, b);
2879 // We can immediately rule out these types as structurally same if
2880 // their layouts differ.
2881 match compare_layouts(a, b) {
2882 Ok(false) => return false,
2883 _ => (), // otherwise, continue onto the full, fields comparison
2886 // Grab a flattened representation of all fields.
2887 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2888 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2890 // Perform a structural comparison for each field.
2893 |&ty::FieldDef { did: a_did, .. },
2894 &ty::FieldDef { did: b_did, .. }| {
2895 structurally_same_type_impl(
2905 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2906 // For arrays, we also check the constness of the type.
2907 a_const.val == b_const.val
2908 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2910 (Slice(a_ty), Slice(b_ty)) => {
2911 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2913 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2914 a_tymut.mutbl == b_tymut.mutbl
2915 && structurally_same_type_impl(
2923 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2924 // For structural sameness, we don't need the region to be same.
2926 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2928 (FnDef(..), FnDef(..)) => {
2929 let a_poly_sig = a.fn_sig(tcx);
2930 let b_poly_sig = b.fn_sig(tcx);
2932 // As we don't compare regions, skip_binder is fine.
2933 let a_sig = a_poly_sig.skip_binder();
2934 let b_sig = b_poly_sig.skip_binder();
2936 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2937 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2938 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2939 structurally_same_type_impl(seen_types, cx, a, b, ckind)
2941 && structurally_same_type_impl(
2949 (Tuple(a_substs), Tuple(b_substs)) => {
2950 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2951 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2954 // For these, it's not quite as easy to define structural-sameness quite so easily.
2955 // For the purposes of this lint, take the conservative approach and mark them as
2956 // not structurally same.
2957 (Dynamic(..), Dynamic(..))
2958 | (Error(..), Error(..))
2959 | (Closure(..), Closure(..))
2960 | (Generator(..), Generator(..))
2961 | (GeneratorWitness(..), GeneratorWitness(..))
2962 | (Projection(..), Projection(..))
2963 | (Opaque(..), Opaque(..)) => false,
2965 // These definitely should have been caught above.
2966 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2968 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2969 // enum layout optimisation is being applied.
2970 (Adt(..), other_kind) | (other_kind, Adt(..))
2971 if is_primitive_or_pointer(other_kind) =>
2973 let (primitive, adt) =
2974 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2975 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2978 compare_layouts(a, b).unwrap_or(false)
2981 // Otherwise, just compare the layouts. This may fail to lint for some
2982 // incompatible types, but at the very least, will stop reads into
2983 // uninitialised memory.
2984 _ => compare_layouts(a, b).unwrap_or(false),
2989 let mut seen_types = FxHashSet::default();
2990 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2994 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2996 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2997 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2998 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2999 if let ForeignItemKind::Fn(..) = this_fi.kind {
3001 if let Some(existing_hid) = self.insert(tcx, this_fi) {
3002 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
3003 let this_decl_ty = tcx.type_of(this_fi.def_id);
3005 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
3006 existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
3008 // Check that the declarations match.
3009 if !Self::structurally_same_type(
3013 CItemKind::Declaration,
3015 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
3016 let orig = Self::name_of_extern_decl(tcx, orig_fi);
3018 // We want to ensure that we use spans for both decls that include where the
3019 // name was defined, whether that was from the link_name attribute or not.
3020 let get_relevant_span =
3021 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
3022 SymbolName::Normal(_) => fi.span,
3023 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
3025 // Finally, emit the diagnostic.
3026 tcx.struct_span_lint_hir(
3027 CLASHING_EXTERN_DECLARATIONS,
3029 get_relevant_span(this_fi),
3031 let mut expected_str = DiagnosticStyledString::new();
3032 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
3033 let mut found_str = DiagnosticStyledString::new();
3034 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3036 lint.build(&format!(
3037 "`{}` redeclare{} with a different signature",
3039 if orig.get_name() == this_fi.ident.name {
3042 format!("s `{}`", orig.get_name())
3046 get_relevant_span(orig_fi),
3047 &format!("`{}` previously declared here", orig.get_name()),
3050 get_relevant_span(this_fi),
3051 "this signature doesn't match the previous declaration",
3053 .note_expected_found(&"", expected_str, &"", found_str)
3064 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3065 /// which causes [undefined behavior].
3070 /// # #![allow(unused)]
3073 /// let x = &*ptr::null::<i32>();
3074 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3075 /// let x = *(0 as *const i32);
3083 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3084 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3086 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3089 "detects when an null pointer is dereferenced"
3092 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3094 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3095 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3096 /// test if expression is a null ptr
3097 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3099 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3100 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3101 return is_zero(expr) || is_null_ptr(cx, expr);
3104 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3105 rustc_hir::ExprKind::Call(ref path, _) => {
3106 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3107 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3109 cx.tcx.get_diagnostic_name(def_id),
3110 Some(sym::ptr_null | sym::ptr_null_mut)
3120 /// test if expression is the literal `0`
3121 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3123 rustc_hir::ExprKind::Lit(ref lit) => {
3124 if let LitKind::Int(a, _) = lit.node {
3133 if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3134 if is_null_ptr(cx, expr_deref) {
3135 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3136 let mut err = lint.build("dereferencing a null pointer");
3137 err.span_label(expr.span, "this code causes undefined behavior when executed");
3146 /// The `named_asm_labels` lint detects the use of named labels in the
3147 /// inline `asm!` macro.
3151 /// ```rust,compile_fail
3152 /// #![feature(asm)]
3155 /// asm!("foo: bar");
3164 /// LLVM is allowed to duplicate inline assembly blocks for any
3165 /// reason, for example when it is in a function that gets inlined. Because
3166 /// of this, GNU assembler [local labels] *must* be used instead of labels
3167 /// with a name. Using named labels might cause assembler or linker errors.
3169 /// See the [unstable book] for more details.
3171 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3172 /// [unstable book]: https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels
3173 pub NAMED_ASM_LABELS,
3175 "named labels in inline assembly",
3178 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3180 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3181 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3183 kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3187 for (template_sym, template_snippet, template_span) in template_strs.iter() {
3188 let template_str = &template_sym.as_str();
3189 let find_label_span = |needle: &str| -> Option<Span> {
3190 if let Some(template_snippet) = template_snippet {
3191 let snippet = template_snippet.as_str();
3192 if let Some(pos) = snippet.find(needle) {
3196 .unwrap_or(snippet[pos..].len() - 1);
3197 let inner = InnerSpan::new(pos, end);
3198 return Some(template_span.from_inner(inner));
3205 let mut found_labels = Vec::new();
3207 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3208 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3209 for statement in statements {
3210 // If there's a comment, trim it from the statement
3211 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3212 let mut start_idx = 0;
3213 for (idx, _) in statement.match_indices(':') {
3214 let possible_label = statement[start_idx..idx].trim();
3215 let mut chars = possible_label.chars();
3216 if let Some(c) = chars.next() {
3217 // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3218 if (c.is_alphabetic() || matches!(c, '.' | '_'))
3219 && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3221 found_labels.push(possible_label);
3223 // If we encounter a non-label, there cannot be any further labels, so stop checking
3227 // Empty string means a leading ':' in this section, which is not a label
3231 start_idx = idx + 1;
3235 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3237 if found_labels.len() > 0 {
3238 let spans = found_labels
3240 .filter_map(|label| find_label_span(label))
3241 .collect::<Vec<Span>>();
3242 // If there were labels but we couldn't find a span, combine the warnings and use the template span
3243 let target_spans: MultiSpan =
3244 if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3246 cx.lookup_with_diagnostics(
3251 diag.build("avoid using named labels in inline assembly");
3254 BuiltinLintDiagnostics::NamedAsmLabel(
3255 "only local labels of the form `<number>:` should be used in inline asm"