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_span::edition::Edition;
45 use rustc_span::source_map::Spanned;
46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
47 use rustc_span::{BytePos, Span};
48 use rustc_target::abi::{LayoutOf, VariantIdx};
49 use rustc_trait_selection::traits::misc::can_type_implement_copy;
51 use crate::nonstandard_style::{method_context, MethodLateContext};
53 use log::{debug, trace};
56 // hardwired lints from librustc_middle
57 pub use rustc_session::lint::builtin::*;
62 "suggest using `loop { }` instead of `while true { }`"
65 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
67 /// Traverse through any amount of parenthesis and return the first non-parens expression.
68 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
69 while let ast::ExprKind::Paren(sub) = &expr.kind {
75 impl EarlyLintPass for WhileTrue {
76 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
77 if let ast::ExprKind::While(cond, ..) = &e.kind {
78 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
79 if let ast::LitKind::Bool(true) = lit.kind {
80 if !lit.span.from_expansion() {
81 let msg = "denote infinite loops with `loop { ... }`";
82 let condition_span = cx.sess.source_map().guess_head_span(e.span);
83 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
85 .span_suggestion_short(
89 Applicability::MachineApplicable,
103 "use of owned (Box type) heap memory"
106 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
109 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
110 for leaf in ty.walk() {
111 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
112 if leaf_ty.is_box() {
113 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
114 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
122 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
123 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
125 hir::ItemKind::Fn(..)
126 | hir::ItemKind::TyAlias(..)
127 | hir::ItemKind::Enum(..)
128 | hir::ItemKind::Struct(..)
129 | hir::ItemKind::Union(..) => {
130 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
131 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
136 // If it's a struct, we also have to check the fields' types
138 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
139 for struct_field in struct_def.fields() {
140 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
141 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
148 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
149 let ty = cx.typeck_results().node_type(e.hir_id);
150 self.check_heap_type(cx, e.span, ty);
155 NON_SHORTHAND_FIELD_PATTERNS,
157 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
160 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
162 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
163 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
164 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
169 .expect("struct pattern type is not an ADT")
170 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
171 for fieldpat in field_pats {
172 if fieldpat.is_shorthand {
175 if fieldpat.span.from_expansion() {
176 // Don't lint if this is a macro expansion: macro authors
177 // shouldn't have to worry about this kind of style issue
181 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
182 if cx.tcx.find_field_index(ident, &variant)
183 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
185 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
187 .build(&format!("the `{}:` in this pattern is redundant", ident));
188 let binding = match binding_annot {
189 hir::BindingAnnotation::Unannotated => None,
190 hir::BindingAnnotation::Mutable => Some("mut"),
191 hir::BindingAnnotation::Ref => Some("ref"),
192 hir::BindingAnnotation::RefMut => Some("ref mut"),
194 let ident = if let Some(binding) = binding {
195 format!("{} {}", binding, ident)
201 "use shorthand field pattern",
203 Applicability::MachineApplicable,
217 "usage of `unsafe` code"
220 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
225 cx: &EarlyContext<'_>,
227 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
229 // This comes from a macro that has `#[allow_internal_unsafe]`.
230 if span.allows_unsafe() {
234 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
238 impl EarlyLintPass for UnsafeCode {
239 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
240 if attr.check_name(sym::allow_internal_unsafe) {
241 self.report_unsafe(cx, attr.span, |lint| {
243 "`allow_internal_unsafe` allows defining \
244 macros using unsafe without triggering \
245 the `unsafe_code` lint at their call site",
252 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
253 if let ast::ExprKind::Block(ref blk, _) = e.kind {
254 // Don't warn about generated blocks; that'll just pollute the output.
255 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
256 self.report_unsafe(cx, blk.span, |lint| {
257 lint.build("usage of an `unsafe` block").emit()
263 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
265 ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
266 self.report_unsafe(cx, it.span, |lint| {
267 lint.build("declaration of an `unsafe` trait").emit()
271 ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
272 self.report_unsafe(cx, it.span, |lint| {
273 lint.build("implementation of an `unsafe` trait").emit()
281 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
285 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
290 let msg = match ctxt {
291 FnCtxt::Foreign => return,
292 FnCtxt::Free => "declaration of an `unsafe` function",
293 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
294 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
296 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
304 "detects missing documentation for public members",
305 report_in_external_macro
308 pub struct MissingDoc {
309 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
310 doc_hidden_stack: Vec<bool>,
312 /// Private traits or trait items that leaked through. Don't check their methods.
313 private_traits: FxHashSet<hir::HirId>,
316 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
318 fn has_doc(attr: &ast::Attribute) -> bool {
319 if attr.is_doc_comment() {
323 if !attr.check_name(sym::doc) {
327 if attr.is_value_str() {
331 if let Some(list) = attr.meta_item_list() {
333 if meta.has_name(sym::include) || meta.has_name(sym::hidden) {
343 pub fn new() -> MissingDoc {
344 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
347 fn doc_hidden(&self) -> bool {
348 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
351 fn check_missing_docs_attrs(
353 cx: &LateContext<'_>,
354 id: Option<hir::HirId>,
355 attrs: &[ast::Attribute],
357 article: &'static str,
360 // If we're building a test harness, then warning about
361 // documentation is probably not really relevant right now.
362 if cx.sess().opts.test {
366 // `#[doc(hidden)]` disables missing_docs check.
367 if self.doc_hidden() {
371 // Only check publicly-visible items, using the result from the privacy pass.
372 // It's an option so the crate root can also use this function (it doesn't
374 if let Some(id) = id {
375 if !cx.access_levels.is_exported(id) {
380 let has_doc = attrs.iter().any(|a| has_doc(a));
384 cx.tcx.sess.source_map().guess_head_span(sp),
386 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
393 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
394 fn enter_lint_attrs(&mut self, _: &LateContext<'_>, attrs: &[ast::Attribute]) {
395 let doc_hidden = self.doc_hidden()
396 || attrs.iter().any(|attr| {
397 attr.check_name(sym::doc)
398 && match attr.meta_item_list() {
400 Some(l) => attr::list_contains_name(&l, sym::hidden),
403 self.doc_hidden_stack.push(doc_hidden);
406 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
407 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
410 fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
411 self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
413 for macro_def in krate.exported_macros {
414 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
418 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
419 |lint| lint.build("missing documentation for macro").emit(),
425 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
427 hir::ItemKind::Trait(.., trait_item_refs) => {
428 // Issue #11592: traits are always considered exported, even when private.
429 if let hir::VisibilityKind::Inherited = it.vis.node {
430 self.private_traits.insert(it.hir_id);
431 for trait_item_ref in trait_item_refs {
432 self.private_traits.insert(trait_item_ref.id.hir_id);
437 hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
438 // If the trait is private, add the impl items to `private_traits` so they don't get
439 // reported for missing docs.
440 let real_trait = trait_ref.path.res.def_id();
441 if let Some(def_id) = real_trait.as_local() {
442 let hir_id = cx.tcx.hir().as_local_hir_id(def_id);
443 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
444 if let hir::VisibilityKind::Inherited = item.vis.node {
445 for impl_item_ref in items {
446 self.private_traits.insert(impl_item_ref.id.hir_id);
454 hir::ItemKind::TyAlias(..)
455 | hir::ItemKind::Fn(..)
456 | hir::ItemKind::Mod(..)
457 | hir::ItemKind::Enum(..)
458 | hir::ItemKind::Struct(..)
459 | hir::ItemKind::Union(..)
460 | hir::ItemKind::Const(..)
461 | hir::ItemKind::Static(..) => {}
466 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
467 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
469 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
472 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
473 if self.private_traits.contains(&trait_item.hir_id) {
477 let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
478 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
480 self.check_missing_docs_attrs(
482 Some(trait_item.hir_id),
490 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
491 // If the method is an impl for a trait, don't doc.
492 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
496 let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
497 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
498 self.check_missing_docs_attrs(
500 Some(impl_item.hir_id),
508 fn check_struct_field(&mut self, cx: &LateContext<'_>, sf: &hir::StructField<'_>) {
509 if !sf.is_positional() {
510 self.check_missing_docs_attrs(
521 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
522 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
527 pub MISSING_COPY_IMPLEMENTATIONS,
529 "detects potentially-forgotten implementations of `Copy`"
532 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
534 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
535 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
536 if !cx.access_levels.is_reachable(item.hir_id) {
539 let (def, ty) = match item.kind {
540 hir::ItemKind::Struct(_, ref ast_generics) => {
541 if !ast_generics.params.is_empty() {
544 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
545 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
547 hir::ItemKind::Union(_, ref ast_generics) => {
548 if !ast_generics.params.is_empty() {
551 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
552 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
554 hir::ItemKind::Enum(_, ref ast_generics) => {
555 if !ast_generics.params.is_empty() {
558 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
559 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
563 if def.has_dtor(cx.tcx) {
566 let param_env = ty::ParamEnv::empty();
567 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
570 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
571 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
573 "type could implement `Copy`; consider adding `impl \
583 MISSING_DEBUG_IMPLEMENTATIONS,
585 "detects missing implementations of Debug"
589 pub struct MissingDebugImplementations {
590 impling_types: Option<HirIdSet>,
593 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
595 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
596 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
597 if !cx.access_levels.is_reachable(item.hir_id) {
602 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
606 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
607 Some(debug) => debug,
611 if self.impling_types.is_none() {
612 let mut impls = HirIdSet::default();
613 cx.tcx.for_each_impl(debug, |d| {
614 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
615 if let Some(def_id) = ty_def.did.as_local() {
616 impls.insert(cx.tcx.hir().as_local_hir_id(def_id));
621 self.impling_types = Some(impls);
622 debug!("{:?}", self.impling_types);
625 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
626 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
628 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
629 or a manual implementation",
630 cx.tcx.def_path_str(debug)
639 pub ANONYMOUS_PARAMETERS,
641 "detects anonymous parameters",
642 @future_incompatible = FutureIncompatibleInfo {
643 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
644 edition: Some(Edition::Edition2018),
649 /// Checks for use of anonymous parameters (RFC 1685).
650 AnonymousParameters => [ANONYMOUS_PARAMETERS]
653 impl EarlyLintPass for AnonymousParameters {
654 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
655 if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
656 for arg in sig.decl.inputs.iter() {
657 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
658 if ident.name == kw::Invalid {
659 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
660 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
662 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
663 (snip.as_str(), Applicability::MachineApplicable)
665 ("<type>", Applicability::HasPlaceholders)
669 "anonymous parameters are deprecated and will be \
670 removed in the next edition.",
674 "try naming the parameter or explicitly \
676 format!("_: {}", ty_snip),
688 /// Check for use of attributes which have been deprecated.
690 pub struct DeprecatedAttr {
691 // This is not free to compute, so we want to keep it around, rather than
692 // compute it for every attribute.
693 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
696 impl_lint_pass!(DeprecatedAttr => []);
698 impl DeprecatedAttr {
699 pub fn new() -> DeprecatedAttr {
700 DeprecatedAttr { depr_attrs: deprecated_attributes() }
704 fn lint_deprecated_attr(
705 cx: &EarlyContext<'_>,
706 attr: &ast::Attribute,
708 suggestion: Option<&str>,
710 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
712 .span_suggestion_short(
714 suggestion.unwrap_or("remove this attribute"),
716 Applicability::MachineApplicable,
722 impl EarlyLintPass for DeprecatedAttr {
723 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
724 for &&(n, _, _, ref g) in &self.depr_attrs {
725 if attr.ident().map(|ident| ident.name) == Some(n) {
726 if let &AttributeGate::Gated(
727 Stability::Deprecated(link, suggestion),
734 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
735 lint_deprecated_attr(cx, attr, &msg, suggestion);
740 if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
741 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
742 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
743 lint_deprecated_attr(cx, attr, &msg, None);
748 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
749 let mut attrs = attrs.iter().peekable();
751 // Accumulate a single span for sugared doc comments.
752 let mut sugared_span: Option<Span> = None;
754 while let Some(attr) = attrs.next() {
755 if attr.is_doc_comment() {
757 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
760 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
764 let span = sugared_span.take().unwrap_or_else(|| attr.span);
766 if attr.is_doc_comment() || attr.check_name(sym::doc) {
767 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
768 let mut err = lint.build("unused doc comment");
771 format!("rustdoc does not generate documentation for {}", node_kind),
779 impl EarlyLintPass for UnusedDocComment {
780 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
781 let kind = match stmt.kind {
782 ast::StmtKind::Local(..) => "statements",
783 ast::StmtKind::Item(..) => "inner items",
784 // expressions will be reported by `check_expr`.
786 | ast::StmtKind::Semi(_)
787 | ast::StmtKind::Expr(_)
788 | ast::StmtKind::MacCall(_) => return,
791 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
794 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
795 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
796 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
799 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
800 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
805 NO_MANGLE_CONST_ITEMS,
807 "const items will not have their symbols exported"
811 NO_MANGLE_GENERIC_ITEMS,
813 "generic items must be mangled"
816 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
818 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
819 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
821 hir::ItemKind::Fn(.., ref generics, _) => {
822 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
823 for param in generics.params {
825 GenericParamKind::Lifetime { .. } => {}
826 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
827 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
829 "functions generic over types or consts must be mangled",
831 .span_suggestion_short(
833 "remove this attribute",
835 // Use of `#[no_mangle]` suggests FFI intent; correct
836 // fix may be to monomorphize source by hand
837 Applicability::MaybeIncorrect,
847 hir::ItemKind::Const(..) => {
848 if attr::contains_name(&it.attrs, sym::no_mangle) {
849 // Const items do not refer to a particular location in memory, and therefore
850 // don't have anything to attach a symbol to
851 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
852 let msg = "const items should never be `#[no_mangle]`";
853 let mut err = lint.build(msg);
855 // account for "pub const" (#45562)
860 .span_to_snippet(it.span)
861 .map(|snippet| snippet.find("const").unwrap_or(0))
862 .unwrap_or(0) as u32;
863 // `const` is 5 chars
864 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
867 "try a static value",
868 "pub static".to_owned(),
869 Applicability::MachineApplicable,
883 "mutating transmuted &mut T from &T may cause undefined behavior"
886 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
888 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
889 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
890 use rustc_target::spec::abi::Abi::RustIntrinsic;
891 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
892 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind))
894 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
895 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
896 consider instead using an UnsafeCell";
897 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
901 fn get_transmute_from_to<'tcx>(
902 cx: &LateContext<'tcx>,
903 expr: &hir::Expr<'_>,
904 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
905 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
906 cx.qpath_res(qpath, expr.hir_id)
910 if let Res::Def(DefKind::Fn, did) = def {
911 if !def_id_is_transmute(cx, did) {
914 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
915 let from = sig.inputs().skip_binder()[0];
916 let to = sig.output().skip_binder();
917 return Some((from, to));
922 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
923 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
924 && cx.tcx.item_name(def_id) == sym::transmute
932 "enabling unstable features (deprecated. do not use)"
936 /// Forbids using the `#[feature(...)]` attribute
937 UnstableFeatures => [UNSTABLE_FEATURES]
940 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
941 fn check_attribute(&mut self, ctx: &LateContext<'_>, attr: &ast::Attribute) {
942 if attr.check_name(sym::feature) {
943 if let Some(items) = attr.meta_item_list() {
945 ctx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
946 lint.build("unstable feature").emit()
957 "`pub` items not reachable from crate root"
961 /// Lint for items marked `pub` that aren't reachable from other crates.
962 UnreachablePub => [UNREACHABLE_PUB]
965 impl UnreachablePub {
968 cx: &LateContext<'_>,
971 vis: &hir::Visibility<'_>,
975 let mut applicability = Applicability::MachineApplicable;
977 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
978 if span.from_expansion() {
979 applicability = Applicability::MaybeIncorrect;
981 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
982 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
983 let mut err = lint.build(&format!("unreachable `pub` {}", what));
984 let replacement = if cx.tcx.features().crate_visibility_modifier {
993 "consider restricting its visibility",
998 err.help("or consider exporting it for use by other crates");
1008 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1009 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1010 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1013 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1017 foreign_item.hir_id,
1024 fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
1025 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1028 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1029 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1036 "bounds in type aliases are not enforced"
1040 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1041 /// They are relevant when using associated types, but otherwise neither checked
1042 /// at definition site nor enforced at use site.
1043 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1046 impl TypeAliasBounds {
1047 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1049 hir::QPath::TypeRelative(ref ty, _) => {
1050 // If this is a type variable, we found a `T::Assoc`.
1052 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1053 Res::Def(DefKind::TyParam, _) => true,
1059 hir::QPath::Resolved(..) => false,
1063 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1064 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1065 // bound. Let's see if this type does that.
1067 // We use a HIR visitor to walk the type.
1068 use rustc_hir::intravisit::{self, Visitor};
1069 struct WalkAssocTypes<'a, 'db> {
1070 err: &'a mut DiagnosticBuilder<'db>,
1072 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1073 type Map = intravisit::ErasedMap<'v>;
1075 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1076 intravisit::NestedVisitorMap::None
1079 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1080 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1083 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1084 associated types in type aliases",
1087 intravisit::walk_qpath(self, qpath, id, span)
1091 // Let's go for a walk!
1092 let mut visitor = WalkAssocTypes { err };
1093 visitor.visit_ty(ty);
1097 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1098 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1099 let (ty, type_alias_generics) = match item.kind {
1100 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1103 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1104 // Bounds are respected for `type X = impl Trait`
1107 let mut suggested_changing_assoc_types = false;
1108 // There must not be a where clause
1109 if !type_alias_generics.where_clause.predicates.is_empty() {
1113 let mut err = lint.build("where clauses are not enforced in type aliases");
1114 let spans: Vec<_> = type_alias_generics
1118 .map(|pred| pred.span())
1120 err.set_span(spans);
1121 err.span_suggestion(
1122 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1123 "the clause will not be checked when the type alias is used, and should be removed",
1125 Applicability::MachineApplicable,
1127 if !suggested_changing_assoc_types {
1128 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1129 suggested_changing_assoc_types = true;
1135 // The parameters must not have bounds
1136 for param in type_alias_generics.params.iter() {
1137 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1138 let suggestion = spans
1141 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1142 (start.to(*sp), String::new())
1145 if !spans.is_empty() {
1146 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1148 lint.build("bounds on generic parameters are not enforced in type aliases");
1149 let msg = "the bound will not be checked when the type alias is used, \
1150 and should be removed";
1151 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1152 if !suggested_changing_assoc_types {
1153 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1154 suggested_changing_assoc_types = true;
1164 /// Lint constants that are erroneous.
1165 /// Without this lint, we might not get any diagnostic if the constant is
1166 /// unused within this crate, even though downstream crates can't use it
1167 /// without producing an error.
1168 UnusedBrokenConst => []
1171 fn check_const(cx: &LateContext<'_>, body_id: hir::BodyId) {
1172 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1173 // trigger the query once for all constants since that will already report the errors
1174 // FIXME: Use ensure here
1175 let _ = cx.tcx.const_eval_poly(def_id);
1178 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1179 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1181 hir::ItemKind::Const(_, body_id) => {
1182 check_const(cx, body_id);
1184 hir::ItemKind::Static(_, _, body_id) => {
1185 check_const(cx, body_id);
1195 "these bounds don't depend on an type parameters"
1199 /// Lint for trait and lifetime bounds that don't depend on type parameters
1200 /// which either do nothing, or stop the item from being used.
1201 TrivialConstraints => [TRIVIAL_BOUNDS]
1204 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1205 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1206 use rustc_middle::ty::fold::TypeFoldable;
1207 use rustc_middle::ty::PredicateAtom::*;
1209 if cx.tcx.features().trivial_bounds {
1210 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1211 let predicates = cx.tcx.predicates_of(def_id);
1212 for &(predicate, span) in predicates.predicates {
1213 let predicate_kind_name = match predicate.skip_binders() {
1214 Trait(..) => "Trait",
1216 RegionOutlives(..) => "Lifetime",
1218 // Ignore projections, as they can only be global
1219 // if the trait bound is global
1221 // Ignore bounds that a user can't type
1226 ConstEvaluatable(..) |
1227 ConstEquate(..) => continue,
1229 if predicate.is_global() {
1230 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1231 lint.build(&format!(
1232 "{} bound {} does not depend on any type \
1233 or lifetime parameters",
1234 predicate_kind_name, predicate
1245 /// Does nothing as a lint pass, but registers some `Lint`s
1246 /// which are used by other parts of the compiler.
1250 NON_SHORTHAND_FIELD_PATTERNS,
1253 MISSING_COPY_IMPLEMENTATIONS,
1254 MISSING_DEBUG_IMPLEMENTATIONS,
1255 ANONYMOUS_PARAMETERS,
1256 UNUSED_DOC_COMMENTS,
1257 NO_MANGLE_CONST_ITEMS,
1258 NO_MANGLE_GENERIC_ITEMS,
1268 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1270 "`...` range patterns are deprecated"
1274 pub struct EllipsisInclusiveRangePatterns {
1275 /// If `Some(_)`, suppress all subsequent pattern
1276 /// warnings for better diagnostics.
1277 node_id: Option<ast::NodeId>,
1280 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1282 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1283 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1284 if self.node_id.is_some() {
1285 // Don't recursively warn about patterns inside range endpoints.
1289 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1291 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1292 /// corresponding to the ellipsis.
1293 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1298 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1299 ) => Some((a.as_deref(), b, *span)),
1304 let (parenthesise, endpoints) = match &pat.kind {
1305 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1306 _ => (false, matches_ellipsis_pat(pat)),
1309 if let Some((start, end, join)) = endpoints {
1310 let msg = "`...` range patterns are deprecated";
1311 let suggestion = "use `..=` for an inclusive range";
1313 self.node_id = Some(pat.id);
1314 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1315 let end = expr_to_string(&end);
1316 let replace = match start {
1317 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1318 None => format!("&(..={})", end),
1325 Applicability::MachineApplicable,
1330 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1332 .span_suggestion_short(
1336 Applicability::MachineApplicable,
1344 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1345 if let Some(node_id) = self.node_id {
1346 if pat.id == node_id {
1354 UNNAMEABLE_TEST_ITEMS,
1356 "detects an item that cannot be named being marked as `#[test_case]`",
1357 report_in_external_macro
1360 pub struct UnnameableTestItems {
1361 boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1362 items_nameable: bool,
1365 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1367 impl UnnameableTestItems {
1368 pub fn new() -> Self {
1369 Self { boundary: None, items_nameable: true }
1373 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1374 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1375 if self.items_nameable {
1376 if let hir::ItemKind::Mod(..) = it.kind {
1378 self.items_nameable = false;
1379 self.boundary = Some(it.hir_id);
1384 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1385 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1386 lint.build("cannot test inner items").emit()
1391 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1392 if !self.items_nameable && self.boundary == Some(it.hir_id) {
1393 self.items_nameable = true;
1401 "detects edition keywords being used as an identifier",
1402 @future_incompatible = FutureIncompatibleInfo {
1403 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1404 edition: Some(Edition::Edition2018),
1409 /// Check for uses of edition keywords used as an identifier.
1410 KeywordIdents => [KEYWORD_IDENTS]
1413 struct UnderMacro(bool);
1415 impl KeywordIdents {
1416 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1417 for tt in tokens.into_trees() {
1419 // Only report non-raw idents.
1420 TokenTree::Token(token) => {
1421 if let Some((ident, false)) = token.ident() {
1422 self.check_ident_token(cx, UnderMacro(true), ident);
1425 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1430 fn check_ident_token(
1432 cx: &EarlyContext<'_>,
1433 UnderMacro(under_macro): UnderMacro,
1436 let next_edition = match cx.sess.edition() {
1437 Edition::Edition2015 => {
1439 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1441 // rust-lang/rust#56327: Conservatively do not
1442 // attempt to report occurrences of `dyn` within
1443 // macro definitions or invocations, because `dyn`
1444 // can legitimately occur as a contextual keyword
1445 // in 2015 code denoting its 2018 meaning, and we
1446 // do not want rustfix to inject bugs into working
1447 // code by rewriting such occurrences.
1449 // But if we see `dyn` outside of a macro, we know
1450 // its precise role in the parsed AST and thus are
1451 // assured this is truly an attempt to use it as
1453 kw::Dyn if !under_macro => Edition::Edition2018,
1459 // There are no new keywords yet for the 2018 edition and beyond.
1463 // Don't lint `r#foo`.
1464 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1468 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1469 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1472 "you can use a raw identifier to stay compatible",
1473 format!("r#{}", ident),
1474 Applicability::MachineApplicable,
1481 impl EarlyLintPass for KeywordIdents {
1482 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1483 self.check_tokens(cx, mac_def.body.inner_tokens());
1485 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1486 self.check_tokens(cx, mac.args.inner_tokens());
1488 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1489 self.check_ident_token(cx, UnderMacro(false), ident);
1493 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1495 impl ExplicitOutlivesRequirements {
1496 fn lifetimes_outliving_lifetime<'tcx>(
1497 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1499 ) -> Vec<ty::Region<'tcx>> {
1502 .filter_map(|(pred, _)| match pred.skip_binders() {
1503 ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
1504 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
1512 fn lifetimes_outliving_type<'tcx>(
1513 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1515 ) -> Vec<ty::Region<'tcx>> {
1518 .filter_map(|(pred, _)| match pred.skip_binders() {
1519 ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
1520 a.is_param(index).then_some(b)
1527 fn collect_outlived_lifetimes<'tcx>(
1529 param: &'tcx hir::GenericParam<'tcx>,
1531 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1532 ty_generics: &'tcx ty::Generics,
1533 ) -> Vec<ty::Region<'tcx>> {
1535 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1538 hir::GenericParamKind::Lifetime { .. } => {
1539 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1541 hir::GenericParamKind::Type { .. } => {
1542 Self::lifetimes_outliving_type(inferred_outlives, index)
1544 hir::GenericParamKind::Const { .. } => Vec::new(),
1548 fn collect_outlives_bound_spans<'tcx>(
1551 bounds: &hir::GenericBounds<'_>,
1552 inferred_outlives: &[ty::Region<'tcx>],
1554 ) -> Vec<(usize, Span)> {
1555 use rustc_middle::middle::resolve_lifetime::Region;
1560 .filter_map(|(i, bound)| {
1561 if let hir::GenericBound::Outlives(lifetime) = bound {
1562 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1563 Some(Region::Static) if infer_static => inferred_outlives
1565 .any(|r| if let ty::ReStatic = r { true } else { false }),
1566 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1567 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1571 is_inferred.then_some((i, bound.span()))
1579 fn consolidate_outlives_bound_spans(
1582 bounds: &hir::GenericBounds<'_>,
1583 bound_spans: Vec<(usize, Span)>,
1585 if bounds.is_empty() {
1588 if bound_spans.len() == bounds.len() {
1589 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1590 // If all bounds are inferable, we want to delete the colon, so
1591 // start from just after the parameter (span passed as argument)
1592 vec![lo.to(last_bound_span)]
1594 let mut merged = Vec::new();
1595 let mut last_merged_i = None;
1597 let mut from_start = true;
1598 for (i, bound_span) in bound_spans {
1599 match last_merged_i {
1600 // If the first bound is inferable, our span should also eat the leading `+`.
1602 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1603 last_merged_i = Some(0);
1605 // If consecutive bounds are inferable, merge their spans
1606 Some(h) if i == h + 1 => {
1607 if let Some(tail) = merged.last_mut() {
1608 // Also eat the trailing `+` if the first
1609 // more-than-one bound is inferable
1610 let to_span = if from_start && i < bounds.len() {
1611 bounds[i + 1].span().shrink_to_lo()
1615 *tail = tail.to(to_span);
1616 last_merged_i = Some(i);
1618 bug!("another bound-span visited earlier");
1622 // When we find a non-inferable bound, subsequent inferable bounds
1623 // won't be consecutive from the start (and we'll eat the leading
1624 // `+` rather than the trailing one)
1626 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1627 last_merged_i = Some(i);
1636 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
1637 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
1638 use rustc_middle::middle::resolve_lifetime::Region;
1640 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1641 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1642 if let hir::ItemKind::Struct(_, ref hir_generics)
1643 | hir::ItemKind::Enum(_, ref hir_generics)
1644 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1646 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1647 if inferred_outlives.is_empty() {
1651 let ty_generics = cx.tcx.generics_of(def_id);
1653 let mut bound_count = 0;
1654 let mut lint_spans = Vec::new();
1656 for param in hir_generics.params {
1657 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1658 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1660 if !has_lifetime_bounds {
1664 let relevant_lifetimes =
1665 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1666 if relevant_lifetimes.is_empty() {
1670 let bound_spans = self.collect_outlives_bound_spans(
1673 &relevant_lifetimes,
1676 bound_count += bound_spans.len();
1677 lint_spans.extend(self.consolidate_outlives_bound_spans(
1678 param.span.shrink_to_hi(),
1684 let mut where_lint_spans = Vec::new();
1685 let mut dropped_predicate_count = 0;
1686 let num_predicates = hir_generics.where_clause.predicates.len();
1687 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1688 let (relevant_lifetimes, bounds, span) = match where_predicate {
1689 hir::WherePredicate::RegionPredicate(predicate) => {
1690 if let Some(Region::EarlyBound(index, ..)) =
1691 cx.tcx.named_region(predicate.lifetime.hir_id)
1694 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1702 hir::WherePredicate::BoundPredicate(predicate) => {
1703 // FIXME we can also infer bounds on associated types,
1704 // and should check for them here.
1705 match predicate.bounded_ty.kind {
1706 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1707 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1708 let index = ty_generics.param_def_id_to_index[&def_id];
1710 Self::lifetimes_outliving_type(inferred_outlives, index),
1725 if relevant_lifetimes.is_empty() {
1729 let bound_spans = self.collect_outlives_bound_spans(
1732 &relevant_lifetimes,
1735 bound_count += bound_spans.len();
1737 let drop_predicate = bound_spans.len() == bounds.len();
1739 dropped_predicate_count += 1;
1742 // If all the bounds on a predicate were inferable and there are
1743 // further predicates, we want to eat the trailing comma.
1744 if drop_predicate && i + 1 < num_predicates {
1745 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1746 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1748 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1749 span.shrink_to_lo(),
1756 // If all predicates are inferable, drop the entire clause
1757 // (including the `where`)
1758 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1759 let where_span = hir_generics
1762 .expect("span of (nonempty) where clause should exist");
1763 // Extend the where clause back to the closing `>` of the
1764 // generics, except for tuple struct, which have the `where`
1765 // after the fields of the struct.
1766 let full_where_span =
1767 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1770 hir_generics.span.shrink_to_hi().to(where_span)
1772 lint_spans.push(full_where_span);
1774 lint_spans.extend(where_lint_spans);
1777 if !lint_spans.is_empty() {
1778 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1779 lint.build("outlives requirements can be inferred")
1780 .multipart_suggestion(
1781 if bound_count == 1 {
1784 "remove these bounds"
1788 .map(|span| (span, "".to_owned()))
1789 .collect::<Vec<_>>(),
1790 Applicability::MachineApplicable,
1800 pub INCOMPLETE_FEATURES,
1802 "incomplete features that may function improperly in some or all cases"
1806 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1807 IncompleteFeatures => [INCOMPLETE_FEATURES]
1810 impl EarlyLintPass for IncompleteFeatures {
1811 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1812 let features = cx.sess.features_untracked();
1814 .declared_lang_features
1816 .map(|(name, span, _)| (name, span))
1817 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1818 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1819 .for_each(|(&name, &span)| {
1820 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1821 let mut builder = lint.build(&format!(
1822 "the feature `{}` is incomplete and may not be safe to use \
1823 and/or cause compiler crashes",
1826 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
1827 builder.note(&format!(
1828 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
1829 for more information",
1842 "an invalid value is being created (such as a NULL reference)"
1845 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1847 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
1848 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
1849 #[derive(Debug, Copy, Clone, PartialEq)]
1855 /// Information about why a type cannot be initialized this way.
1856 /// Contains an error message and optionally a span to point at.
1857 type InitError = (String, Option<Span>);
1859 /// Test if this constant is all-0.
1860 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1861 use hir::ExprKind::*;
1862 use rustc_ast::ast::LitKind::*;
1865 if let Int(i, _) = lit.node {
1871 Tup(tup) => tup.iter().all(is_zero),
1876 /// Determine if this expression is a "dangerous initialization".
1877 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1878 // `transmute` is inside an anonymous module (the `extern` block?);
1879 // `Invalid` represents the empty string and matches that.
1880 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1881 // on intrinsics right now.
1882 const TRANSMUTE_PATH: &[Symbol] =
1883 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1885 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1886 // Find calls to `mem::{uninitialized,zeroed}` methods.
1887 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1888 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1890 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1891 return Some(InitKind::Zeroed);
1892 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1893 return Some(InitKind::Uninit);
1894 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1895 if is_zero(&args[0]) {
1896 return Some(InitKind::Zeroed);
1900 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
1901 // Find problematic calls to `MaybeUninit::assume_init`.
1902 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
1903 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1904 // This is a call to *some* method named `assume_init`.
1905 // See if the `self` parameter is one of the dangerous constructors.
1906 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1907 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1908 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1910 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1911 return Some(InitKind::Zeroed);
1912 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1913 return Some(InitKind::Uninit);
1923 /// Test if this enum has several actually "existing" variants.
1924 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
1925 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
1926 // As an approximation, we only count dataless variants. Those are definitely inhabited.
1927 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
1928 existing_variants > 1
1931 /// Return `Some` only if we are sure this type does *not*
1932 /// allow zero initialization.
1933 fn ty_find_init_error<'tcx>(
1937 ) -> Option<InitError> {
1938 use rustc_middle::ty::TyKind::*;
1940 // Primitive types that don't like 0 as a value.
1941 Ref(..) => Some(("references must be non-null".to_string(), None)),
1942 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1943 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1944 Never => Some(("the `!` type has no valid value".to_string(), None)),
1945 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1946 // raw ptr to dyn Trait
1948 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1950 // Primitive types with other constraints.
1951 Bool if init == InitKind::Uninit => {
1952 Some(("booleans must be either `true` or `false`".to_string(), None))
1954 Char if init == InitKind::Uninit => {
1955 Some(("characters must be a valid Unicode codepoint".to_string(), None))
1957 // Recurse and checks for some compound types.
1958 Adt(adt_def, substs) if !adt_def.is_union() => {
1959 // First check if this ADT has a layout attribute (like `NonNull` and friends).
1960 use std::ops::Bound;
1961 match tcx.layout_scalar_valid_range(adt_def.did) {
1962 // We exploit here that `layout_scalar_valid_range` will never
1963 // return `Bound::Excluded`. (And we have tests checking that we
1964 // handle the attribute correctly.)
1965 (Bound::Included(lo), _) if lo > 0 => {
1966 return Some((format!("`{}` must be non-null", ty), None));
1968 (Bound::Included(_), _) | (_, Bound::Included(_))
1969 if init == InitKind::Uninit =>
1973 "`{}` must be initialized inside its custom valid range",
1982 match adt_def.variants.len() {
1983 0 => Some(("enums with no variants have no valid value".to_string(), None)),
1985 // Struct, or enum with exactly one variant.
1986 // Proceed recursively, check all fields.
1987 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1988 variant.fields.iter().find_map(|field| {
1989 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1992 // Point to this field, should be helpful for figuring
1993 // out where the source of the error is.
1994 let span = tcx.def_span(field.did);
1997 " (in this {} field)",
2010 // Multi-variant enum.
2012 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2013 let span = tcx.def_span(adt_def.did);
2015 "enums have to be initialized to a variant".to_string(),
2019 // In principle, for zero-initialization we could figure out which variant corresponds
2020 // to tag 0, and check that... but for now we just accept all zero-initializations.
2027 // Proceed recursively, check all fields.
2028 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2030 // Conservative fallback.
2035 if let Some(init) = is_dangerous_init(cx, expr) {
2036 // This conjures an instance of a type out of nothing,
2037 // using zeroed or uninitialized memory.
2038 // We are extremely conservative with what we warn about.
2039 let conjured_ty = cx.typeck_results().expr_ty(expr);
2040 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2041 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2042 let mut err = lint.build(&format!(
2043 "the type `{}` does not permit {}",
2046 InitKind::Zeroed => "zero-initialization",
2047 InitKind::Uninit => "being left uninitialized",
2050 err.span_label(expr.span, "this code causes undefined behavior when executed");
2053 "help: use `MaybeUninit<T>` instead, \
2054 and only call `assume_init` after initialization is done",
2056 if let Some(span) = span {
2057 err.span_note(span, &msg);
2069 pub CLASHING_EXTERN_DECLARATIONS,
2071 "detects when an extern fn has been declared with the same name but different types"
2074 pub struct ClashingExternDeclarations {
2075 seen_decls: FxHashMap<Symbol, HirId>,
2078 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2079 /// just from declaration itself. This is important because we don't want to report clashes on
2080 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2083 /// The name of the symbol + the span of the annotation which introduced the link name.
2085 /// No link name, so just the name of the symbol.
2090 fn get_name(&self) -> Symbol {
2092 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2097 impl ClashingExternDeclarations {
2098 crate fn new() -> Self {
2099 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2101 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2102 /// for the item, return its HirId without updating the set.
2103 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2104 let hid = fi.hir_id;
2107 &tcx.codegen_fn_attrs(tcx.hir().local_def_id(hid)).link_name.unwrap_or(fi.ident.name);
2109 if self.seen_decls.contains_key(name) {
2110 // Avoid updating the map with the new entry when we do find a collision. We want to
2111 // make sure we're always pointing to the first definition as the previous declaration.
2112 // This lets us avoid emitting "knock-on" diagnostics.
2113 Some(*self.seen_decls.get(name).unwrap())
2115 self.seen_decls.insert(*name, hid)
2119 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2120 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2122 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2123 let did = tcx.hir().local_def_id(fi.hir_id);
2124 if let Some((overridden_link_name, overridden_link_name_span)) =
2125 tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2126 // FIXME: Instead of searching through the attributes again to get span
2127 // information, we could have codegen_fn_attrs also give span information back for
2128 // where the attribute was defined. However, until this is found to be a
2129 // bottleneck, this does just fine.
2131 overridden_link_name,
2132 tcx.get_attrs(did.to_def_id())
2134 .find(|at| at.check_name(sym::link_name))
2140 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2142 SymbolName::Normal(fi.ident.name)
2146 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2147 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2148 /// with the same members (as the declarations shouldn't clash).
2149 fn structurally_same_type<'tcx>(
2150 cx: &LateContext<'tcx>,
2155 debug!("structurally_same_type(cx, a = {:?}, b = {:?})", a, b);
2157 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2158 // All nominally-same types are structurally same, too.
2161 // Do a full, depth-first comparison between the two.
2162 use rustc_middle::ty::TyKind::*;
2163 let a_kind = &a.kind;
2164 let b_kind = &b.kind;
2166 let compare_layouts = |a, b| -> bool {
2167 let a_layout = &cx.layout_of(a).unwrap().layout.abi;
2168 let b_layout = &cx.layout_of(b).unwrap().layout.abi;
2169 debug!("{:?} == {:?} = {}", a_layout, b_layout, a_layout == b_layout);
2170 a_layout == b_layout
2173 #[allow(rustc::usage_of_ty_tykind)]
2174 let is_primitive_or_pointer =
2175 |kind: &ty::TyKind<'_>| kind.is_primitive() || matches!(kind, RawPtr(..));
2177 match (a_kind, b_kind) {
2178 (Adt(_, a_substs), Adt(_, b_substs)) => {
2179 let a = a.subst(cx.tcx, a_substs);
2180 let b = b.subst(cx.tcx, b_substs);
2181 debug!("Comparing {:?} and {:?}", a, b);
2183 if let (Adt(a_def, ..), Adt(b_def, ..)) = (&a.kind, &b.kind) {
2184 // Grab a flattened representation of all fields.
2185 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2186 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2187 compare_layouts(a, b)
2190 |&ty::FieldDef { did: a_did, .. },
2191 &ty::FieldDef { did: b_did, .. }| {
2192 Self::structurally_same_type(
2204 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2205 // For arrays, we also check the constness of the type.
2206 a_const.val == b_const.val
2207 && Self::structurally_same_type(cx, a_const.ty, b_const.ty, ckind)
2208 && Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2210 (Slice(a_ty), Slice(b_ty)) => Self::structurally_same_type(cx, a_ty, b_ty, ckind),
2211 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2212 a_tymut.mutbl == b_tymut.mutbl
2213 && Self::structurally_same_type(cx, &a_tymut.ty, &b_tymut.ty, ckind)
2215 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2216 // For structural sameness, we don't need the region to be same.
2217 a_mut == b_mut && Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2219 (FnDef(..), FnDef(..)) => {
2220 let a_poly_sig = a.fn_sig(tcx);
2221 let b_poly_sig = b.fn_sig(tcx);
2223 // As we don't compare regions, skip_binder is fine.
2224 let a_sig = a_poly_sig.skip_binder();
2225 let b_sig = b_poly_sig.skip_binder();
2227 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2228 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2229 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2230 Self::structurally_same_type(cx, a, b, ckind)
2232 && Self::structurally_same_type(cx, a_sig.output(), b_sig.output(), ckind)
2234 (Tuple(a_substs), Tuple(b_substs)) => {
2235 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2236 Self::structurally_same_type(cx, a_ty, b_ty, ckind)
2239 // For these, it's not quite as easy to define structural-sameness quite so easily.
2240 // For the purposes of this lint, take the conservative approach and mark them as
2241 // not structurally same.
2242 (Dynamic(..), Dynamic(..))
2243 | (Error(..), Error(..))
2244 | (Closure(..), Closure(..))
2245 | (Generator(..), Generator(..))
2246 | (GeneratorWitness(..), GeneratorWitness(..))
2247 | (Projection(..), Projection(..))
2248 | (Opaque(..), Opaque(..)) => false,
2250 // These definitely should have been caught above.
2251 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2253 // An Adt and a primitive type. This can be FFI-safe is the ADT is an enum with a
2255 (Adt(..), other_kind) | (other_kind, Adt(..))
2256 if is_primitive_or_pointer(other_kind) =>
2258 let (primitive, adt) =
2259 if is_primitive_or_pointer(&a.kind) { (a, b) } else { (b, a) };
2260 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2263 compare_layouts(a, b)
2266 // Otherwise, just compare the layouts. This may fail to lint for some
2267 // incompatible types, but at the very least, will stop reads into
2268 // uninitialised memory.
2269 _ => compare_layouts(a, b),
2275 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2277 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2278 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2279 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2280 if let ForeignItemKind::Fn(..) = this_fi.kind {
2282 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2283 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2284 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2286 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2287 existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2289 // Check that the declarations match.
2290 if !Self::structurally_same_type(
2294 CItemKind::Declaration,
2296 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2297 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2299 // We want to ensure that we use spans for both decls that include where the
2300 // name was defined, whether that was from the link_name attribute or not.
2301 let get_relevant_span =
2302 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2303 SymbolName::Normal(_) => fi.span,
2304 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2306 // Finally, emit the diagnostic.
2307 tcx.struct_span_lint_hir(
2308 CLASHING_EXTERN_DECLARATIONS,
2310 get_relevant_span(this_fi),
2312 let mut expected_str = DiagnosticStyledString::new();
2313 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2314 let mut found_str = DiagnosticStyledString::new();
2315 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2317 lint.build(&format!(
2318 "`{}` redeclare{} with a different signature",
2320 if orig.get_name() == this_fi.ident.name {
2323 format!("s `{}`", orig.get_name())
2327 get_relevant_span(orig_fi),
2328 &format!("`{}` previously declared here", orig.get_name()),
2331 get_relevant_span(this_fi),
2332 "this signature doesn't match the previous declaration",
2334 .note_expected_found(&"", expected_str, &"", found_str)