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::CItemKind, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
26 use rustc_ast::ast::{self, Expr};
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_pretty::pprust::{self, expr_to_string};
31 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
32 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
33 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
34 use rustc_feature::{GateIssue, Stability};
36 use rustc_hir::def::{DefKind, Res};
37 use rustc_hir::def_id::DefId;
38 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
39 use rustc_hir::{HirId, HirIdSet, Node};
40 use rustc_middle::lint::LintDiagnosticBuilder;
41 use rustc_middle::ty::subst::{GenericArgKind, Subst};
42 use rustc_middle::ty::{self, Ty, TyCtxt};
43 use rustc_session::lint::FutureIncompatibleInfo;
44 use rustc_session::Session;
45 use rustc_span::edition::Edition;
46 use rustc_span::source_map::Spanned;
47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
48 use rustc_span::{BytePos, Span};
49 use rustc_target::abi::{LayoutOf, VariantIdx};
50 use rustc_trait_selection::traits::misc::can_type_implement_copy;
52 use crate::nonstandard_style::{method_context, MethodLateContext};
54 use log::{debug, trace};
57 // hardwired lints from librustc_middle
58 pub use rustc_session::lint::builtin::*;
63 "suggest using `loop { }` instead of `while true { }`"
66 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
68 /// Traverse through any amount of parenthesis and return the first non-parens expression.
69 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
70 while let ast::ExprKind::Paren(sub) = &expr.kind {
76 impl EarlyLintPass for WhileTrue {
77 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
78 if let ast::ExprKind::While(cond, ..) = &e.kind {
79 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
80 if let ast::LitKind::Bool(true) = lit.kind {
81 if !lit.span.from_expansion() {
82 let msg = "denote infinite loops with `loop { ... }`";
83 let condition_span = cx.sess.source_map().guess_head_span(e.span);
84 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
86 .span_suggestion_short(
90 Applicability::MachineApplicable,
104 "use of owned (Box type) heap memory"
107 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
110 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
111 for leaf in ty.walk() {
112 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
113 if leaf_ty.is_box() {
114 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
115 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
123 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
124 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
126 hir::ItemKind::Fn(..)
127 | hir::ItemKind::TyAlias(..)
128 | hir::ItemKind::Enum(..)
129 | hir::ItemKind::Struct(..)
130 | hir::ItemKind::Union(..) => {
131 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
132 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
137 // If it's a struct, we also have to check the fields' types
139 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
140 for struct_field in struct_def.fields() {
141 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
142 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
149 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
150 let ty = cx.typeck_results().node_type(e.hir_id);
151 self.check_heap_type(cx, e.span, ty);
156 NON_SHORTHAND_FIELD_PATTERNS,
158 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
161 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
163 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
164 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
165 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
170 .expect("struct pattern type is not an ADT")
171 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
172 for fieldpat in field_pats {
173 if fieldpat.is_shorthand {
176 if fieldpat.span.from_expansion() {
177 // Don't lint if this is a macro expansion: macro authors
178 // shouldn't have to worry about this kind of style issue
182 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
183 if cx.tcx.find_field_index(ident, &variant)
184 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
186 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
188 .build(&format!("the `{}:` in this pattern is redundant", ident));
189 let binding = match binding_annot {
190 hir::BindingAnnotation::Unannotated => None,
191 hir::BindingAnnotation::Mutable => Some("mut"),
192 hir::BindingAnnotation::Ref => Some("ref"),
193 hir::BindingAnnotation::RefMut => Some("ref mut"),
195 let ident = if let Some(binding) = binding {
196 format!("{} {}", binding, ident)
202 "use shorthand field pattern",
204 Applicability::MachineApplicable,
218 "usage of `unsafe` code"
221 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
226 cx: &EarlyContext<'_>,
228 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
230 // This comes from a macro that has `#[allow_internal_unsafe]`.
231 if span.allows_unsafe() {
235 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
239 impl EarlyLintPass for UnsafeCode {
240 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
241 if cx.sess().check_name(attr, sym::allow_internal_unsafe) {
242 self.report_unsafe(cx, attr.span, |lint| {
244 "`allow_internal_unsafe` allows defining \
245 macros using unsafe without triggering \
246 the `unsafe_code` lint at their call site",
253 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
254 if let ast::ExprKind::Block(ref blk, _) = e.kind {
255 // Don't warn about generated blocks; that'll just pollute the output.
256 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
257 self.report_unsafe(cx, blk.span, |lint| {
258 lint.build("usage of an `unsafe` block").emit()
264 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
266 ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
267 self.report_unsafe(cx, it.span, |lint| {
268 lint.build("declaration of an `unsafe` trait").emit()
272 ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
273 self.report_unsafe(cx, it.span, |lint| {
274 lint.build("implementation of an `unsafe` trait").emit()
282 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
286 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
291 let msg = match ctxt {
292 FnCtxt::Foreign => return,
293 FnCtxt::Free => "declaration of an `unsafe` function",
294 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
295 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
297 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
305 "detects missing documentation for public members",
306 report_in_external_macro
309 pub struct MissingDoc {
310 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
311 doc_hidden_stack: Vec<bool>,
313 /// Private traits or trait items that leaked through. Don't check their methods.
314 private_traits: FxHashSet<hir::HirId>,
317 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
319 fn has_doc(sess: &Session, attr: &ast::Attribute) -> bool {
320 if attr.is_doc_comment() {
324 if !sess.check_name(attr, sym::doc) {
328 if attr.is_value_str() {
332 if let Some(list) = attr.meta_item_list() {
334 if meta.has_name(sym::include) || meta.has_name(sym::hidden) {
344 pub fn new() -> MissingDoc {
345 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
348 fn doc_hidden(&self) -> bool {
349 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
352 fn check_missing_docs_attrs(
354 cx: &LateContext<'_>,
355 id: Option<hir::HirId>,
356 attrs: &[ast::Attribute],
358 article: &'static str,
361 // If we're building a test harness, then warning about
362 // documentation is probably not really relevant right now.
363 if cx.sess().opts.test {
367 // `#[doc(hidden)]` disables missing_docs check.
368 if self.doc_hidden() {
372 // Only check publicly-visible items, using the result from the privacy pass.
373 // It's an option so the crate root can also use this function (it doesn't
375 if let Some(id) = id {
376 if !cx.access_levels.is_exported(id) {
381 let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
385 cx.tcx.sess.source_map().guess_head_span(sp),
387 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
394 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
395 fn enter_lint_attrs(&mut self, cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
396 let doc_hidden = self.doc_hidden()
397 || attrs.iter().any(|attr| {
398 cx.sess().check_name(attr, sym::doc)
399 && match attr.meta_item_list() {
401 Some(l) => attr::list_contains_name(&l, sym::hidden),
404 self.doc_hidden_stack.push(doc_hidden);
407 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
408 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
411 fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
412 self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
414 for macro_def in krate.exported_macros {
415 let has_doc = macro_def.attrs.iter().any(|a| has_doc(cx.sess(), a));
419 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
420 |lint| lint.build("missing documentation for macro").emit(),
426 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
428 hir::ItemKind::Trait(.., trait_item_refs) => {
429 // Issue #11592: traits are always considered exported, even when private.
430 if let hir::VisibilityKind::Inherited = it.vis.node {
431 self.private_traits.insert(it.hir_id);
432 for trait_item_ref in trait_item_refs {
433 self.private_traits.insert(trait_item_ref.id.hir_id);
438 hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
439 // If the trait is private, add the impl items to `private_traits` so they don't get
440 // reported for missing docs.
441 let real_trait = trait_ref.path.res.def_id();
442 if let Some(def_id) = real_trait.as_local() {
443 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
444 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
445 if let hir::VisibilityKind::Inherited = item.vis.node {
446 for impl_item_ref in items {
447 self.private_traits.insert(impl_item_ref.id.hir_id);
455 hir::ItemKind::TyAlias(..)
456 | hir::ItemKind::Fn(..)
457 | hir::ItemKind::Mod(..)
458 | hir::ItemKind::Enum(..)
459 | hir::ItemKind::Struct(..)
460 | hir::ItemKind::Union(..)
461 | hir::ItemKind::Const(..)
462 | hir::ItemKind::Static(..) => {}
467 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
468 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
470 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
473 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
474 if self.private_traits.contains(&trait_item.hir_id) {
478 let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
479 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
481 self.check_missing_docs_attrs(
483 Some(trait_item.hir_id),
491 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
492 // If the method is an impl for a trait, don't doc.
493 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
497 let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
498 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
499 self.check_missing_docs_attrs(
501 Some(impl_item.hir_id),
509 fn check_struct_field(&mut self, cx: &LateContext<'_>, sf: &hir::StructField<'_>) {
510 if !sf.is_positional() {
511 self.check_missing_docs_attrs(
522 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
523 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
528 pub MISSING_COPY_IMPLEMENTATIONS,
530 "detects potentially-forgotten implementations of `Copy`"
533 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
535 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
536 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
537 if !cx.access_levels.is_reachable(item.hir_id) {
540 let (def, ty) = match item.kind {
541 hir::ItemKind::Struct(_, ref ast_generics) => {
542 if !ast_generics.params.is_empty() {
545 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
546 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
548 hir::ItemKind::Union(_, ref ast_generics) => {
549 if !ast_generics.params.is_empty() {
552 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
553 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
555 hir::ItemKind::Enum(_, ref ast_generics) => {
556 if !ast_generics.params.is_empty() {
559 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
560 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
564 if def.has_dtor(cx.tcx) {
567 let param_env = ty::ParamEnv::empty();
568 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
571 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
572 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
574 "type could implement `Copy`; consider adding `impl \
584 MISSING_DEBUG_IMPLEMENTATIONS,
586 "detects missing implementations of Debug"
590 pub struct MissingDebugImplementations {
591 impling_types: Option<HirIdSet>,
594 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
596 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
597 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
598 if !cx.access_levels.is_reachable(item.hir_id) {
603 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
607 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
608 Some(debug) => debug,
612 if self.impling_types.is_none() {
613 let mut impls = HirIdSet::default();
614 cx.tcx.for_each_impl(debug, |d| {
615 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
616 if let Some(def_id) = ty_def.did.as_local() {
617 impls.insert(cx.tcx.hir().local_def_id_to_hir_id(def_id));
622 self.impling_types = Some(impls);
623 debug!("{:?}", self.impling_types);
626 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
627 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
629 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
630 or a manual implementation",
631 cx.tcx.def_path_str(debug)
640 pub ANONYMOUS_PARAMETERS,
642 "detects anonymous parameters",
643 @future_incompatible = FutureIncompatibleInfo {
644 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
645 edition: Some(Edition::Edition2018),
650 /// Checks for use of anonymous parameters (RFC 1685).
651 AnonymousParameters => [ANONYMOUS_PARAMETERS]
654 impl EarlyLintPass for AnonymousParameters {
655 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
656 if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
657 for arg in sig.decl.inputs.iter() {
658 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
659 if ident.name == kw::Invalid {
660 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
661 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
663 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
664 (snip.as_str(), Applicability::MachineApplicable)
666 ("<type>", Applicability::HasPlaceholders)
670 "anonymous parameters are deprecated and will be \
671 removed in the next edition.",
675 "try naming the parameter or explicitly \
677 format!("_: {}", ty_snip),
689 /// Check for use of attributes which have been deprecated.
691 pub struct DeprecatedAttr {
692 // This is not free to compute, so we want to keep it around, rather than
693 // compute it for every attribute.
694 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
697 impl_lint_pass!(DeprecatedAttr => []);
699 impl DeprecatedAttr {
700 pub fn new() -> DeprecatedAttr {
701 DeprecatedAttr { depr_attrs: deprecated_attributes() }
705 fn lint_deprecated_attr(
706 cx: &EarlyContext<'_>,
707 attr: &ast::Attribute,
709 suggestion: Option<&str>,
711 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
713 .span_suggestion_short(
715 suggestion.unwrap_or("remove this attribute"),
717 Applicability::MachineApplicable,
723 impl EarlyLintPass for DeprecatedAttr {
724 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
725 for &&(n, _, _, ref g) in &self.depr_attrs {
726 if attr.ident().map(|ident| ident.name) == Some(n) {
727 if let &AttributeGate::Gated(
728 Stability::Deprecated(link, suggestion),
735 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
736 lint_deprecated_attr(cx, attr, &msg, suggestion);
741 if cx.sess().check_name(attr, sym::no_start) || cx.sess().check_name(attr, sym::crate_id) {
742 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
743 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
744 lint_deprecated_attr(cx, attr, &msg, None);
749 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
750 let mut attrs = attrs.iter().peekable();
752 // Accumulate a single span for sugared doc comments.
753 let mut sugared_span: Option<Span> = None;
755 while let Some(attr) = attrs.next() {
756 if attr.is_doc_comment() {
758 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
761 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
765 let span = sugared_span.take().unwrap_or_else(|| attr.span);
767 if attr.is_doc_comment() || cx.sess().check_name(attr, sym::doc) {
768 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
769 let mut err = lint.build("unused doc comment");
772 format!("rustdoc does not generate documentation for {}", node_kind),
780 impl EarlyLintPass for UnusedDocComment {
781 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
782 let kind = match stmt.kind {
783 ast::StmtKind::Local(..) => "statements",
784 ast::StmtKind::Item(..) => "inner items",
785 // expressions will be reported by `check_expr`.
787 | ast::StmtKind::Semi(_)
788 | ast::StmtKind::Expr(_)
789 | ast::StmtKind::MacCall(_) => return,
792 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
795 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
796 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
797 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
800 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
801 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
806 NO_MANGLE_CONST_ITEMS,
808 "const items will not have their symbols exported"
812 NO_MANGLE_GENERIC_ITEMS,
814 "generic items must be mangled"
817 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
819 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
820 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
822 hir::ItemKind::Fn(.., ref generics, _) => {
823 if let Some(no_mangle_attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
824 for param in generics.params {
826 GenericParamKind::Lifetime { .. } => {}
827 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
828 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
830 "functions generic over types or consts must be mangled",
832 .span_suggestion_short(
834 "remove this attribute",
836 // Use of `#[no_mangle]` suggests FFI intent; correct
837 // fix may be to monomorphize source by hand
838 Applicability::MaybeIncorrect,
848 hir::ItemKind::Const(..) => {
849 if cx.sess().contains_name(&it.attrs, sym::no_mangle) {
850 // Const items do not refer to a particular location in memory, and therefore
851 // don't have anything to attach a symbol to
852 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
853 let msg = "const items should never be `#[no_mangle]`";
854 let mut err = lint.build(msg);
856 // account for "pub const" (#45562)
861 .span_to_snippet(it.span)
862 .map(|snippet| snippet.find("const").unwrap_or(0))
863 .unwrap_or(0) as u32;
864 // `const` is 5 chars
865 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
868 "try a static value",
869 "pub static".to_owned(),
870 Applicability::MachineApplicable,
884 "mutating transmuted &mut T from &T may cause undefined behavior"
887 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
889 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
890 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
891 use rustc_target::spec::abi::Abi::RustIntrinsic;
892 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
893 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind))
895 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
896 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
897 consider instead using an UnsafeCell";
898 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
902 fn get_transmute_from_to<'tcx>(
903 cx: &LateContext<'tcx>,
904 expr: &hir::Expr<'_>,
905 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
906 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
907 cx.qpath_res(qpath, expr.hir_id)
911 if let Res::Def(DefKind::Fn, did) = def {
912 if !def_id_is_transmute(cx, did) {
915 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
916 let from = sig.inputs().skip_binder()[0];
917 let to = sig.output().skip_binder();
918 return Some((from, to));
923 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
924 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
925 && cx.tcx.item_name(def_id) == sym::transmute
933 "enabling unstable features (deprecated. do not use)"
937 /// Forbids using the `#[feature(...)]` attribute
938 UnstableFeatures => [UNSTABLE_FEATURES]
941 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
942 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
943 if cx.sess().check_name(attr, sym::feature) {
944 if let Some(items) = attr.meta_item_list() {
946 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
947 lint.build("unstable feature").emit()
958 "`pub` items not reachable from crate root"
962 /// Lint for items marked `pub` that aren't reachable from other crates.
963 UnreachablePub => [UNREACHABLE_PUB]
966 impl UnreachablePub {
969 cx: &LateContext<'_>,
972 vis: &hir::Visibility<'_>,
976 let mut applicability = Applicability::MachineApplicable;
978 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
979 if span.from_expansion() {
980 applicability = Applicability::MaybeIncorrect;
982 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
983 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
984 let mut err = lint.build(&format!("unreachable `pub` {}", what));
985 let replacement = if cx.tcx.features().crate_visibility_modifier {
994 "consider restricting its visibility",
999 err.help("or consider exporting it for use by other crates");
1009 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1010 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1011 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1014 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1018 foreign_item.hir_id,
1025 fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
1026 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1029 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1030 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1037 "bounds in type aliases are not enforced"
1041 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1042 /// They are relevant when using associated types, but otherwise neither checked
1043 /// at definition site nor enforced at use site.
1044 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1047 impl TypeAliasBounds {
1048 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1050 hir::QPath::TypeRelative(ref ty, _) => {
1051 // If this is a type variable, we found a `T::Assoc`.
1053 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1054 Res::Def(DefKind::TyParam, _) => true,
1060 hir::QPath::Resolved(..) => false,
1064 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1065 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1066 // bound. Let's see if this type does that.
1068 // We use a HIR visitor to walk the type.
1069 use rustc_hir::intravisit::{self, Visitor};
1070 struct WalkAssocTypes<'a, 'db> {
1071 err: &'a mut DiagnosticBuilder<'db>,
1073 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1074 type Map = intravisit::ErasedMap<'v>;
1076 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1077 intravisit::NestedVisitorMap::None
1080 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1081 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1084 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1085 associated types in type aliases",
1088 intravisit::walk_qpath(self, qpath, id, span)
1092 // Let's go for a walk!
1093 let mut visitor = WalkAssocTypes { err };
1094 visitor.visit_ty(ty);
1098 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1099 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1100 let (ty, type_alias_generics) = match item.kind {
1101 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1104 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1105 // Bounds are respected for `type X = impl Trait`
1108 let mut suggested_changing_assoc_types = false;
1109 // There must not be a where clause
1110 if !type_alias_generics.where_clause.predicates.is_empty() {
1114 let mut err = lint.build("where clauses are not enforced in type aliases");
1115 let spans: Vec<_> = type_alias_generics
1119 .map(|pred| pred.span())
1121 err.set_span(spans);
1122 err.span_suggestion(
1123 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1124 "the clause will not be checked when the type alias is used, and should be removed",
1126 Applicability::MachineApplicable,
1128 if !suggested_changing_assoc_types {
1129 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1130 suggested_changing_assoc_types = true;
1136 // The parameters must not have bounds
1137 for param in type_alias_generics.params.iter() {
1138 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1139 let suggestion = spans
1142 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1143 (start.to(*sp), String::new())
1146 if !spans.is_empty() {
1147 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1149 lint.build("bounds on generic parameters are not enforced in type aliases");
1150 let msg = "the bound will not be checked when the type alias is used, \
1151 and should be removed";
1152 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1153 if !suggested_changing_assoc_types {
1154 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1155 suggested_changing_assoc_types = true;
1165 /// Lint constants that are erroneous.
1166 /// Without this lint, we might not get any diagnostic if the constant is
1167 /// unused within this crate, even though downstream crates can't use it
1168 /// without producing an error.
1169 UnusedBrokenConst => []
1172 fn check_const(cx: &LateContext<'_>, body_id: hir::BodyId) {
1173 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1174 // trigger the query once for all constants since that will already report the errors
1175 // FIXME: Use ensure here
1176 let _ = cx.tcx.const_eval_poly(def_id);
1179 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1180 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1182 hir::ItemKind::Const(_, body_id) => {
1183 check_const(cx, body_id);
1185 hir::ItemKind::Static(_, _, body_id) => {
1186 check_const(cx, body_id);
1196 "these bounds don't depend on an type parameters"
1200 /// Lint for trait and lifetime bounds that don't depend on type parameters
1201 /// which either do nothing, or stop the item from being used.
1202 TrivialConstraints => [TRIVIAL_BOUNDS]
1205 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1206 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1207 use rustc_middle::ty::fold::TypeFoldable;
1208 use rustc_middle::ty::PredicateAtom::*;
1210 if cx.tcx.features().trivial_bounds {
1211 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1212 let predicates = cx.tcx.predicates_of(def_id);
1213 for &(predicate, span) in predicates.predicates {
1214 let predicate_kind_name = match predicate.skip_binders() {
1215 Trait(..) => "Trait",
1217 RegionOutlives(..) => "Lifetime",
1219 // Ignore projections, as they can only be global
1220 // if the trait bound is global
1222 // Ignore bounds that a user can't type
1227 ConstEvaluatable(..) |
1228 ConstEquate(..) => continue,
1230 if predicate.is_global() {
1231 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1232 lint.build(&format!(
1233 "{} bound {} does not depend on any type \
1234 or lifetime parameters",
1235 predicate_kind_name, predicate
1246 /// Does nothing as a lint pass, but registers some `Lint`s
1247 /// which are used by other parts of the compiler.
1251 NON_SHORTHAND_FIELD_PATTERNS,
1254 MISSING_COPY_IMPLEMENTATIONS,
1255 MISSING_DEBUG_IMPLEMENTATIONS,
1256 ANONYMOUS_PARAMETERS,
1257 UNUSED_DOC_COMMENTS,
1258 NO_MANGLE_CONST_ITEMS,
1259 NO_MANGLE_GENERIC_ITEMS,
1269 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1271 "`...` range patterns are deprecated"
1275 pub struct EllipsisInclusiveRangePatterns {
1276 /// If `Some(_)`, suppress all subsequent pattern
1277 /// warnings for better diagnostics.
1278 node_id: Option<ast::NodeId>,
1281 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1283 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1284 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1285 if self.node_id.is_some() {
1286 // Don't recursively warn about patterns inside range endpoints.
1290 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1292 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1293 /// corresponding to the ellipsis.
1294 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1299 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1300 ) => Some((a.as_deref(), b, *span)),
1305 let (parenthesise, endpoints) = match &pat.kind {
1306 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1307 _ => (false, matches_ellipsis_pat(pat)),
1310 if let Some((start, end, join)) = endpoints {
1311 let msg = "`...` range patterns are deprecated";
1312 let suggestion = "use `..=` for an inclusive range";
1314 self.node_id = Some(pat.id);
1315 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1316 let end = expr_to_string(&end);
1317 let replace = match start {
1318 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1319 None => format!("&(..={})", end),
1326 Applicability::MachineApplicable,
1331 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1333 .span_suggestion_short(
1337 Applicability::MachineApplicable,
1345 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1346 if let Some(node_id) = self.node_id {
1347 if pat.id == node_id {
1355 UNNAMEABLE_TEST_ITEMS,
1357 "detects an item that cannot be named being marked as `#[test_case]`",
1358 report_in_external_macro
1361 pub struct UnnameableTestItems {
1362 boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1363 items_nameable: bool,
1366 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1368 impl UnnameableTestItems {
1369 pub fn new() -> Self {
1370 Self { boundary: None, items_nameable: true }
1374 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1375 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1376 if self.items_nameable {
1377 if let hir::ItemKind::Mod(..) = it.kind {
1379 self.items_nameable = false;
1380 self.boundary = Some(it.hir_id);
1385 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::rustc_test_marker) {
1386 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1387 lint.build("cannot test inner items").emit()
1392 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1393 if !self.items_nameable && self.boundary == Some(it.hir_id) {
1394 self.items_nameable = true;
1402 "detects edition keywords being used as an identifier",
1403 @future_incompatible = FutureIncompatibleInfo {
1404 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1405 edition: Some(Edition::Edition2018),
1410 /// Check for uses of edition keywords used as an identifier.
1411 KeywordIdents => [KEYWORD_IDENTS]
1414 struct UnderMacro(bool);
1416 impl KeywordIdents {
1417 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1418 for tt in tokens.into_trees() {
1420 // Only report non-raw idents.
1421 TokenTree::Token(token) => {
1422 if let Some((ident, false)) = token.ident() {
1423 self.check_ident_token(cx, UnderMacro(true), ident);
1426 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1431 fn check_ident_token(
1433 cx: &EarlyContext<'_>,
1434 UnderMacro(under_macro): UnderMacro,
1437 let next_edition = match cx.sess.edition() {
1438 Edition::Edition2015 => {
1440 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1442 // rust-lang/rust#56327: Conservatively do not
1443 // attempt to report occurrences of `dyn` within
1444 // macro definitions or invocations, because `dyn`
1445 // can legitimately occur as a contextual keyword
1446 // in 2015 code denoting its 2018 meaning, and we
1447 // do not want rustfix to inject bugs into working
1448 // code by rewriting such occurrences.
1450 // But if we see `dyn` outside of a macro, we know
1451 // its precise role in the parsed AST and thus are
1452 // assured this is truly an attempt to use it as
1454 kw::Dyn if !under_macro => Edition::Edition2018,
1460 // There are no new keywords yet for the 2018 edition and beyond.
1464 // Don't lint `r#foo`.
1465 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1469 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1470 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1473 "you can use a raw identifier to stay compatible",
1474 format!("r#{}", ident),
1475 Applicability::MachineApplicable,
1482 impl EarlyLintPass for KeywordIdents {
1483 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1484 self.check_tokens(cx, mac_def.body.inner_tokens());
1486 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1487 self.check_tokens(cx, mac.args.inner_tokens());
1489 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1490 self.check_ident_token(cx, UnderMacro(false), ident);
1494 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1496 impl ExplicitOutlivesRequirements {
1497 fn lifetimes_outliving_lifetime<'tcx>(
1498 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1500 ) -> Vec<ty::Region<'tcx>> {
1503 .filter_map(|(pred, _)| match pred.skip_binders() {
1504 ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
1505 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
1513 fn lifetimes_outliving_type<'tcx>(
1514 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1516 ) -> Vec<ty::Region<'tcx>> {
1519 .filter_map(|(pred, _)| match pred.skip_binders() {
1520 ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
1521 a.is_param(index).then_some(b)
1528 fn collect_outlived_lifetimes<'tcx>(
1530 param: &'tcx hir::GenericParam<'tcx>,
1532 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1533 ty_generics: &'tcx ty::Generics,
1534 ) -> Vec<ty::Region<'tcx>> {
1536 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1539 hir::GenericParamKind::Lifetime { .. } => {
1540 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1542 hir::GenericParamKind::Type { .. } => {
1543 Self::lifetimes_outliving_type(inferred_outlives, index)
1545 hir::GenericParamKind::Const { .. } => Vec::new(),
1549 fn collect_outlives_bound_spans<'tcx>(
1552 bounds: &hir::GenericBounds<'_>,
1553 inferred_outlives: &[ty::Region<'tcx>],
1555 ) -> Vec<(usize, Span)> {
1556 use rustc_middle::middle::resolve_lifetime::Region;
1561 .filter_map(|(i, bound)| {
1562 if let hir::GenericBound::Outlives(lifetime) = bound {
1563 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1564 Some(Region::Static) if infer_static => inferred_outlives
1566 .any(|r| if let ty::ReStatic = r { true } else { false }),
1567 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1568 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1572 is_inferred.then_some((i, bound.span()))
1580 fn consolidate_outlives_bound_spans(
1583 bounds: &hir::GenericBounds<'_>,
1584 bound_spans: Vec<(usize, Span)>,
1586 if bounds.is_empty() {
1589 if bound_spans.len() == bounds.len() {
1590 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1591 // If all bounds are inferable, we want to delete the colon, so
1592 // start from just after the parameter (span passed as argument)
1593 vec![lo.to(last_bound_span)]
1595 let mut merged = Vec::new();
1596 let mut last_merged_i = None;
1598 let mut from_start = true;
1599 for (i, bound_span) in bound_spans {
1600 match last_merged_i {
1601 // If the first bound is inferable, our span should also eat the leading `+`.
1603 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1604 last_merged_i = Some(0);
1606 // If consecutive bounds are inferable, merge their spans
1607 Some(h) if i == h + 1 => {
1608 if let Some(tail) = merged.last_mut() {
1609 // Also eat the trailing `+` if the first
1610 // more-than-one bound is inferable
1611 let to_span = if from_start && i < bounds.len() {
1612 bounds[i + 1].span().shrink_to_lo()
1616 *tail = tail.to(to_span);
1617 last_merged_i = Some(i);
1619 bug!("another bound-span visited earlier");
1623 // When we find a non-inferable bound, subsequent inferable bounds
1624 // won't be consecutive from the start (and we'll eat the leading
1625 // `+` rather than the trailing one)
1627 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1628 last_merged_i = Some(i);
1637 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
1638 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
1639 use rustc_middle::middle::resolve_lifetime::Region;
1641 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1642 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1643 if let hir::ItemKind::Struct(_, ref hir_generics)
1644 | hir::ItemKind::Enum(_, ref hir_generics)
1645 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1647 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1648 if inferred_outlives.is_empty() {
1652 let ty_generics = cx.tcx.generics_of(def_id);
1654 let mut bound_count = 0;
1655 let mut lint_spans = Vec::new();
1657 for param in hir_generics.params {
1658 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1659 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1661 if !has_lifetime_bounds {
1665 let relevant_lifetimes =
1666 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1667 if relevant_lifetimes.is_empty() {
1671 let bound_spans = self.collect_outlives_bound_spans(
1674 &relevant_lifetimes,
1677 bound_count += bound_spans.len();
1678 lint_spans.extend(self.consolidate_outlives_bound_spans(
1679 param.span.shrink_to_hi(),
1685 let mut where_lint_spans = Vec::new();
1686 let mut dropped_predicate_count = 0;
1687 let num_predicates = hir_generics.where_clause.predicates.len();
1688 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1689 let (relevant_lifetimes, bounds, span) = match where_predicate {
1690 hir::WherePredicate::RegionPredicate(predicate) => {
1691 if let Some(Region::EarlyBound(index, ..)) =
1692 cx.tcx.named_region(predicate.lifetime.hir_id)
1695 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1703 hir::WherePredicate::BoundPredicate(predicate) => {
1704 // FIXME we can also infer bounds on associated types,
1705 // and should check for them here.
1706 match predicate.bounded_ty.kind {
1707 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1708 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1709 let index = ty_generics.param_def_id_to_index[&def_id];
1711 Self::lifetimes_outliving_type(inferred_outlives, index),
1726 if relevant_lifetimes.is_empty() {
1730 let bound_spans = self.collect_outlives_bound_spans(
1733 &relevant_lifetimes,
1736 bound_count += bound_spans.len();
1738 let drop_predicate = bound_spans.len() == bounds.len();
1740 dropped_predicate_count += 1;
1743 // If all the bounds on a predicate were inferable and there are
1744 // further predicates, we want to eat the trailing comma.
1745 if drop_predicate && i + 1 < num_predicates {
1746 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1747 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1749 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1750 span.shrink_to_lo(),
1757 // If all predicates are inferable, drop the entire clause
1758 // (including the `where`)
1759 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1760 let where_span = hir_generics
1763 .expect("span of (nonempty) where clause should exist");
1764 // Extend the where clause back to the closing `>` of the
1765 // generics, except for tuple struct, which have the `where`
1766 // after the fields of the struct.
1767 let full_where_span =
1768 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1771 hir_generics.span.shrink_to_hi().to(where_span)
1773 lint_spans.push(full_where_span);
1775 lint_spans.extend(where_lint_spans);
1778 if !lint_spans.is_empty() {
1779 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1780 lint.build("outlives requirements can be inferred")
1781 .multipart_suggestion(
1782 if bound_count == 1 {
1785 "remove these bounds"
1789 .map(|span| (span, "".to_owned()))
1790 .collect::<Vec<_>>(),
1791 Applicability::MachineApplicable,
1801 pub INCOMPLETE_FEATURES,
1803 "incomplete features that may function improperly in some or all cases"
1807 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1808 IncompleteFeatures => [INCOMPLETE_FEATURES]
1811 impl EarlyLintPass for IncompleteFeatures {
1812 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1813 let features = cx.sess.features_untracked();
1815 .declared_lang_features
1817 .map(|(name, span, _)| (name, span))
1818 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1819 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1820 .for_each(|(&name, &span)| {
1821 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1822 let mut builder = lint.build(&format!(
1823 "the feature `{}` is incomplete and may not be safe to use \
1824 and/or cause compiler crashes",
1827 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
1828 builder.note(&format!(
1829 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
1830 for more information",
1843 "an invalid value is being created (such as a NULL reference)"
1846 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1848 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
1849 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
1850 #[derive(Debug, Copy, Clone, PartialEq)]
1856 /// Information about why a type cannot be initialized this way.
1857 /// Contains an error message and optionally a span to point at.
1858 type InitError = (String, Option<Span>);
1860 /// Test if this constant is all-0.
1861 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1862 use hir::ExprKind::*;
1863 use rustc_ast::ast::LitKind::*;
1866 if let Int(i, _) = lit.node {
1872 Tup(tup) => tup.iter().all(is_zero),
1877 /// Determine if this expression is a "dangerous initialization".
1878 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1879 // `transmute` is inside an anonymous module (the `extern` block?);
1880 // `Invalid` represents the empty string and matches that.
1881 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1882 // on intrinsics right now.
1883 const TRANSMUTE_PATH: &[Symbol] =
1884 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1886 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1887 // Find calls to `mem::{uninitialized,zeroed}` methods.
1888 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1889 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1891 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1892 return Some(InitKind::Zeroed);
1893 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1894 return Some(InitKind::Uninit);
1895 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1896 if is_zero(&args[0]) {
1897 return Some(InitKind::Zeroed);
1901 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
1902 // Find problematic calls to `MaybeUninit::assume_init`.
1903 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
1904 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1905 // This is a call to *some* method named `assume_init`.
1906 // See if the `self` parameter is one of the dangerous constructors.
1907 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1908 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1909 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1911 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1912 return Some(InitKind::Zeroed);
1913 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1914 return Some(InitKind::Uninit);
1924 /// Test if this enum has several actually "existing" variants.
1925 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
1926 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
1927 // As an approximation, we only count dataless variants. Those are definitely inhabited.
1928 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
1929 existing_variants > 1
1932 /// Return `Some` only if we are sure this type does *not*
1933 /// allow zero initialization.
1934 fn ty_find_init_error<'tcx>(
1938 ) -> Option<InitError> {
1939 use rustc_middle::ty::TyKind::*;
1941 // Primitive types that don't like 0 as a value.
1942 Ref(..) => Some(("references must be non-null".to_string(), None)),
1943 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1944 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1945 Never => Some(("the `!` type has no valid value".to_string(), None)),
1946 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1947 // raw ptr to dyn Trait
1949 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1951 // Primitive types with other constraints.
1952 Bool if init == InitKind::Uninit => {
1953 Some(("booleans must be either `true` or `false`".to_string(), None))
1955 Char if init == InitKind::Uninit => {
1956 Some(("characters must be a valid Unicode codepoint".to_string(), None))
1958 // Recurse and checks for some compound types.
1959 Adt(adt_def, substs) if !adt_def.is_union() => {
1960 // First check if this ADT has a layout attribute (like `NonNull` and friends).
1961 use std::ops::Bound;
1962 match tcx.layout_scalar_valid_range(adt_def.did) {
1963 // We exploit here that `layout_scalar_valid_range` will never
1964 // return `Bound::Excluded`. (And we have tests checking that we
1965 // handle the attribute correctly.)
1966 (Bound::Included(lo), _) if lo > 0 => {
1967 return Some((format!("`{}` must be non-null", ty), None));
1969 (Bound::Included(_), _) | (_, Bound::Included(_))
1970 if init == InitKind::Uninit =>
1974 "`{}` must be initialized inside its custom valid range",
1983 match adt_def.variants.len() {
1984 0 => Some(("enums with no variants have no valid value".to_string(), None)),
1986 // Struct, or enum with exactly one variant.
1987 // Proceed recursively, check all fields.
1988 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1989 variant.fields.iter().find_map(|field| {
1990 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1993 // Point to this field, should be helpful for figuring
1994 // out where the source of the error is.
1995 let span = tcx.def_span(field.did);
1998 " (in this {} field)",
2011 // Multi-variant enum.
2013 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2014 let span = tcx.def_span(adt_def.did);
2016 "enums have to be initialized to a variant".to_string(),
2020 // In principle, for zero-initialization we could figure out which variant corresponds
2021 // to tag 0, and check that... but for now we just accept all zero-initializations.
2028 // Proceed recursively, check all fields.
2029 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2031 // Conservative fallback.
2036 if let Some(init) = is_dangerous_init(cx, expr) {
2037 // This conjures an instance of a type out of nothing,
2038 // using zeroed or uninitialized memory.
2039 // We are extremely conservative with what we warn about.
2040 let conjured_ty = cx.typeck_results().expr_ty(expr);
2041 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2042 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2043 let mut err = lint.build(&format!(
2044 "the type `{}` does not permit {}",
2047 InitKind::Zeroed => "zero-initialization",
2048 InitKind::Uninit => "being left uninitialized",
2051 err.span_label(expr.span, "this code causes undefined behavior when executed");
2054 "help: use `MaybeUninit<T>` instead, \
2055 and only call `assume_init` after initialization is done",
2057 if let Some(span) = span {
2058 err.span_note(span, &msg);
2070 pub CLASHING_EXTERN_DECLARATIONS,
2072 "detects when an extern fn has been declared with the same name but different types"
2075 pub struct ClashingExternDeclarations {
2076 seen_decls: FxHashMap<Symbol, HirId>,
2079 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2080 /// just from declaration itself. This is important because we don't want to report clashes on
2081 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2084 /// The name of the symbol + the span of the annotation which introduced the link name.
2086 /// No link name, so just the name of the symbol.
2091 fn get_name(&self) -> Symbol {
2093 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2098 impl ClashingExternDeclarations {
2099 crate fn new() -> Self {
2100 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2102 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2103 /// for the item, return its HirId without updating the set.
2104 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2105 let hid = fi.hir_id;
2108 &tcx.codegen_fn_attrs(tcx.hir().local_def_id(hid)).link_name.unwrap_or(fi.ident.name);
2110 if self.seen_decls.contains_key(name) {
2111 // Avoid updating the map with the new entry when we do find a collision. We want to
2112 // make sure we're always pointing to the first definition as the previous declaration.
2113 // This lets us avoid emitting "knock-on" diagnostics.
2114 Some(*self.seen_decls.get(name).unwrap())
2116 self.seen_decls.insert(*name, hid)
2120 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2121 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2123 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2124 let did = tcx.hir().local_def_id(fi.hir_id);
2125 if let Some((overridden_link_name, overridden_link_name_span)) =
2126 tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2127 // FIXME: Instead of searching through the attributes again to get span
2128 // information, we could have codegen_fn_attrs also give span information back for
2129 // where the attribute was defined. However, until this is found to be a
2130 // bottleneck, this does just fine.
2132 overridden_link_name,
2133 tcx.get_attrs(did.to_def_id())
2135 .find(|at| tcx.sess.check_name(at, sym::link_name))
2141 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2143 SymbolName::Normal(fi.ident.name)
2147 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2148 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2149 /// with the same members (as the declarations shouldn't clash).
2150 fn structurally_same_type<'tcx>(
2151 cx: &LateContext<'tcx>,
2156 debug!("structurally_same_type(cx, a = {:?}, b = {:?})", a, b);
2158 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2159 // All nominally-same types are structurally same, too.
2162 // Do a full, depth-first comparison between the two.
2163 use rustc_middle::ty::TyKind::*;
2164 let a_kind = &a.kind;
2165 let b_kind = &b.kind;
2167 let compare_layouts = |a, b| -> bool {
2168 let a_layout = &cx.layout_of(a).unwrap().layout.abi;
2169 let b_layout = &cx.layout_of(b).unwrap().layout.abi;
2170 debug!("{:?} == {:?} = {}", a_layout, b_layout, a_layout == b_layout);
2171 a_layout == b_layout
2174 #[allow(rustc::usage_of_ty_tykind)]
2175 let is_primitive_or_pointer =
2176 |kind: &ty::TyKind<'_>| kind.is_primitive() || matches!(kind, RawPtr(..));
2178 match (a_kind, b_kind) {
2179 (Adt(_, a_substs), Adt(_, b_substs)) => {
2180 let a = a.subst(cx.tcx, a_substs);
2181 let b = b.subst(cx.tcx, b_substs);
2182 debug!("Comparing {:?} and {:?}", a, b);
2184 if let (Adt(a_def, ..), Adt(b_def, ..)) = (&a.kind, &b.kind) {
2185 // Grab a flattened representation of all fields.
2186 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2187 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2188 compare_layouts(a, b)
2191 |&ty::FieldDef { did: a_did, .. },
2192 &ty::FieldDef { did: b_did, .. }| {
2193 Self::structurally_same_type(
2205 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2206 // For arrays, we also check the constness of the type.
2207 a_const.val == b_const.val
2208 && Self::structurally_same_type(cx, a_const.ty, b_const.ty, ckind)
2209 && Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2211 (Slice(a_ty), Slice(b_ty)) => Self::structurally_same_type(cx, a_ty, b_ty, ckind),
2212 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2213 a_tymut.mutbl == b_tymut.mutbl
2214 && Self::structurally_same_type(cx, &a_tymut.ty, &b_tymut.ty, ckind)
2216 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2217 // For structural sameness, we don't need the region to be same.
2218 a_mut == b_mut && Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2220 (FnDef(..), FnDef(..)) => {
2221 let a_poly_sig = a.fn_sig(tcx);
2222 let b_poly_sig = b.fn_sig(tcx);
2224 // As we don't compare regions, skip_binder is fine.
2225 let a_sig = a_poly_sig.skip_binder();
2226 let b_sig = b_poly_sig.skip_binder();
2228 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2229 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2230 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2231 Self::structurally_same_type(cx, a, b, ckind)
2233 && Self::structurally_same_type(cx, a_sig.output(), b_sig.output(), ckind)
2235 (Tuple(a_substs), Tuple(b_substs)) => {
2236 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2237 Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2240 // For these, it's not quite as easy to define structural-sameness quite so easily.
2241 // For the purposes of this lint, take the conservative approach and mark them as
2242 // not structurally same.
2243 (Dynamic(..), Dynamic(..))
2244 | (Error(..), Error(..))
2245 | (Closure(..), Closure(..))
2246 | (Generator(..), Generator(..))
2247 | (GeneratorWitness(..), GeneratorWitness(..))
2248 | (Projection(..), Projection(..))
2249 | (Opaque(..), Opaque(..)) => false,
2251 // These definitely should have been caught above.
2252 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2254 // An Adt and a primitive type. This can be FFI-safe is the ADT is an enum with a
2256 (Adt(..), other_kind) | (other_kind, Adt(..))
2257 if is_primitive_or_pointer(other_kind) =>
2259 let (primitive, adt) =
2260 if is_primitive_or_pointer(&a.kind) { (a, b) } else { (b, a) };
2261 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2264 compare_layouts(a, b)
2267 // Otherwise, just compare the layouts. This may fail to lint for some
2268 // incompatible types, but at the very least, will stop reads into
2269 // uninitialised memory.
2270 _ => compare_layouts(a, b),
2276 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2278 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2279 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2280 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2281 if let ForeignItemKind::Fn(..) = this_fi.kind {
2283 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2284 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2285 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2287 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2288 existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2290 // Check that the declarations match.
2291 if !Self::structurally_same_type(
2295 CItemKind::Declaration,
2297 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2298 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2300 // We want to ensure that we use spans for both decls that include where the
2301 // name was defined, whether that was from the link_name attribute or not.
2302 let get_relevant_span =
2303 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2304 SymbolName::Normal(_) => fi.span,
2305 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2307 // Finally, emit the diagnostic.
2308 tcx.struct_span_lint_hir(
2309 CLASHING_EXTERN_DECLARATIONS,
2311 get_relevant_span(this_fi),
2313 let mut expected_str = DiagnosticStyledString::new();
2314 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2315 let mut found_str = DiagnosticStyledString::new();
2316 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2318 lint.build(&format!(
2319 "`{}` redeclare{} with a different signature",
2321 if orig.get_name() == this_fi.ident.name {
2324 format!("s `{}`", orig.get_name())
2328 get_relevant_span(orig_fi),
2329 &format!("`{}` previously declared here", orig.get_name()),
2332 get_relevant_span(this_fi),
2333 "this signature doesn't match the previous declaration",
2335 .note_expected_found(&"", expected_str, &"", found_str)