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`.
23 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
24 use rustc_ast::ast::{self, Expr};
25 use rustc_ast::attr::{self, HasAttrs};
26 use rustc_ast::tokenstream::{TokenStream, TokenTree};
27 use rustc_ast::visit::{FnCtxt, FnKind};
28 use rustc_ast_pretty::pprust::{self, expr_to_string};
29 use rustc_data_structures::fx::FxHashSet;
30 use rustc_errors::{Applicability, DiagnosticBuilder};
31 use rustc_feature::Stability;
32 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
34 use rustc_hir::def::{DefKind, Res};
35 use rustc_hir::def_id::DefId;
36 use rustc_hir::{GenericParamKind, PatKind};
37 use rustc_hir::{HirIdSet, Node};
38 use rustc_middle::lint::LintDiagnosticBuilder;
39 use rustc_middle::ty::{self, Ty, TyCtxt};
40 use rustc_session::lint::FutureIncompatibleInfo;
41 use rustc_span::edition::Edition;
42 use rustc_span::source_map::Spanned;
43 use rustc_span::symbol::{kw, sym, Symbol};
44 use rustc_span::{BytePos, Span};
45 use rustc_target::abi::VariantIdx;
46 use rustc_trait_selection::traits::misc::can_type_implement_copy;
48 use crate::nonstandard_style::{method_context, MethodLateContext};
53 // hardwired lints from librustc_middle
54 pub use rustc_session::lint::builtin::*;
59 "suggest using `loop { }` instead of `while true { }`"
62 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
64 /// Traverse through any amount of parenthesis and return the first non-parens expression.
65 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
66 while let ast::ExprKind::Paren(sub) = &expr.kind {
72 impl EarlyLintPass for WhileTrue {
73 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
74 if let ast::ExprKind::While(cond, ..) = &e.kind {
75 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
76 if let ast::LitKind::Bool(true) = lit.kind {
77 if !lit.span.from_expansion() {
78 let msg = "denote infinite loops with `loop { ... }`";
79 let condition_span = cx.sess.source_map().guess_head_span(e.span);
80 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
82 .span_suggestion_short(
86 Applicability::MachineApplicable,
100 "use of owned (Box type) heap memory"
103 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
106 fn check_heap_type(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
107 for leaf_ty in ty.walk() {
108 if leaf_ty.is_box() {
109 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
110 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
117 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
118 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
120 hir::ItemKind::Fn(..)
121 | hir::ItemKind::TyAlias(..)
122 | hir::ItemKind::Enum(..)
123 | hir::ItemKind::Struct(..)
124 | hir::ItemKind::Union(..) => {
125 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
126 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
131 // If it's a struct, we also have to check the fields' types
133 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
134 for struct_field in struct_def.fields() {
135 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
136 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
143 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
144 let ty = cx.tables.node_type(e.hir_id);
145 self.check_heap_type(cx, e.span, ty);
150 NON_SHORTHAND_FIELD_PATTERNS,
152 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
155 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
157 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
158 fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat<'_>) {
159 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
164 .expect("struct pattern type is not an ADT")
165 .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
166 for fieldpat in field_pats {
167 if fieldpat.is_shorthand {
170 if fieldpat.span.from_expansion() {
171 // Don't lint if this is a macro expansion: macro authors
172 // shouldn't have to worry about this kind of style issue
176 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
177 if cx.tcx.find_field_index(ident, &variant)
178 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables))
180 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
182 .build(&format!("the `{}:` in this pattern is redundant", ident));
183 let binding = match binding_annot {
184 hir::BindingAnnotation::Unannotated => None,
185 hir::BindingAnnotation::Mutable => Some("mut"),
186 hir::BindingAnnotation::Ref => Some("ref"),
187 hir::BindingAnnotation::RefMut => Some("ref mut"),
189 let ident = if let Some(binding) = binding {
190 format!("{} {}", binding, ident)
196 "use shorthand field pattern",
198 Applicability::MachineApplicable,
212 "usage of `unsafe` code"
215 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
220 cx: &EarlyContext<'_>,
222 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
224 // This comes from a macro that has `#[allow_internal_unsafe]`.
225 if span.allows_unsafe() {
229 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
233 impl EarlyLintPass for UnsafeCode {
234 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
235 if attr.check_name(sym::allow_internal_unsafe) {
236 self.report_unsafe(cx, attr.span, |lint| {
238 "`allow_internal_unsafe` allows defining \
239 macros using unsafe without triggering \
240 the `unsafe_code` lint at their call site",
247 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
248 if let ast::ExprKind::Block(ref blk, _) = e.kind {
249 // Don't warn about generated blocks; that'll just pollute the output.
250 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
251 self.report_unsafe(cx, blk.span, |lint| {
252 lint.build("usage of an `unsafe` block").emit()
258 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
260 ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
261 self.report_unsafe(cx, it.span, |lint| {
262 lint.build("declaration of an `unsafe` trait").emit()
266 ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
267 self.report_unsafe(cx, it.span, |lint| {
268 lint.build("implementation of an `unsafe` trait").emit()
276 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
280 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
285 let msg = match ctxt {
286 FnCtxt::Foreign => return,
287 FnCtxt::Free => "declaration of an `unsafe` function",
288 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
289 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
291 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
299 "detects missing documentation for public members",
300 report_in_external_macro
303 pub struct MissingDoc {
304 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
305 doc_hidden_stack: Vec<bool>,
307 /// Private traits or trait items that leaked through. Don't check their methods.
308 private_traits: FxHashSet<hir::HirId>,
311 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
313 fn has_doc(attr: &ast::Attribute) -> bool {
314 if attr.is_doc_comment() {
318 if !attr.check_name(sym::doc) {
322 if attr.is_value_str() {
326 if let Some(list) = attr.meta_item_list() {
328 if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
338 pub fn new() -> MissingDoc {
339 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
342 fn doc_hidden(&self) -> bool {
343 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
346 fn check_missing_docs_attrs(
348 cx: &LateContext<'_, '_>,
349 id: Option<hir::HirId>,
350 attrs: &[ast::Attribute],
352 article: &'static str,
355 // If we're building a test harness, then warning about
356 // documentation is probably not really relevant right now.
357 if cx.sess().opts.test {
361 // `#[doc(hidden)]` disables missing_docs check.
362 if self.doc_hidden() {
366 // Only check publicly-visible items, using the result from the privacy pass.
367 // It's an option so the crate root can also use this function (it doesn't
369 if let Some(id) = id {
370 if !cx.access_levels.is_exported(id) {
375 let has_doc = attrs.iter().any(|a| has_doc(a));
379 cx.tcx.sess.source_map().guess_head_span(sp),
381 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
388 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
389 fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
390 let doc_hidden = self.doc_hidden()
391 || attrs.iter().any(|attr| {
392 attr.check_name(sym::doc)
393 && match attr.meta_item_list() {
395 Some(l) => attr::list_contains_name(&l, sym::hidden),
398 self.doc_hidden_stack.push(doc_hidden);
401 fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
402 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
405 fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate<'_>) {
406 self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
408 for macro_def in krate.exported_macros {
409 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
413 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
414 |lint| lint.build("missing documentation for macro").emit(),
420 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
422 hir::ItemKind::Trait(.., trait_item_refs) => {
423 // Issue #11592: traits are always considered exported, even when private.
424 if let hir::VisibilityKind::Inherited = it.vis.node {
425 self.private_traits.insert(it.hir_id);
426 for trait_item_ref in trait_item_refs {
427 self.private_traits.insert(trait_item_ref.id.hir_id);
432 hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
433 // If the trait is private, add the impl items to `private_traits` so they don't get
434 // reported for missing docs.
435 let real_trait = trait_ref.path.res.def_id();
436 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
437 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
438 if let hir::VisibilityKind::Inherited = item.vis.node {
439 for impl_item_ref in items {
440 self.private_traits.insert(impl_item_ref.id.hir_id);
448 hir::ItemKind::TyAlias(..)
449 | hir::ItemKind::Fn(..)
450 | hir::ItemKind::Mod(..)
451 | hir::ItemKind::Enum(..)
452 | hir::ItemKind::Struct(..)
453 | hir::ItemKind::Union(..)
454 | hir::ItemKind::Const(..)
455 | hir::ItemKind::Static(..) => {}
460 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
461 let (article, desc) = cx.tcx.article_and_description(def_id);
463 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
466 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem<'_>) {
467 if self.private_traits.contains(&trait_item.hir_id) {
471 let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
472 let (article, desc) = cx.tcx.article_and_description(def_id);
474 self.check_missing_docs_attrs(
476 Some(trait_item.hir_id),
484 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
485 // If the method is an impl for a trait, don't doc.
486 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
490 let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
491 let (article, desc) = cx.tcx.article_and_description(def_id);
492 self.check_missing_docs_attrs(
494 Some(impl_item.hir_id),
502 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField<'_>) {
503 if !sf.is_positional() {
504 self.check_missing_docs_attrs(
515 fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant<'_>) {
516 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
521 pub MISSING_COPY_IMPLEMENTATIONS,
523 "detects potentially-forgotten implementations of `Copy`"
526 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
528 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
529 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
530 if !cx.access_levels.is_reachable(item.hir_id) {
533 let (def, ty) = match item.kind {
534 hir::ItemKind::Struct(_, ref ast_generics) => {
535 if !ast_generics.params.is_empty() {
538 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
539 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
541 hir::ItemKind::Union(_, 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::Enum(_, 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(&[])))
557 if def.has_dtor(cx.tcx) {
560 let param_env = ty::ParamEnv::empty();
561 if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
564 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
565 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
567 "type could implement `Copy`; consider adding `impl \
577 MISSING_DEBUG_IMPLEMENTATIONS,
579 "detects missing implementations of Debug"
583 pub struct MissingDebugImplementations {
584 impling_types: Option<HirIdSet>,
587 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
589 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
590 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
591 if !cx.access_levels.is_reachable(item.hir_id) {
596 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
600 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
601 Some(debug) => debug,
605 if self.impling_types.is_none() {
606 let mut impls = HirIdSet::default();
607 cx.tcx.for_each_impl(debug, |d| {
608 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
609 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
610 impls.insert(hir_id);
615 self.impling_types = Some(impls);
616 debug!("{:?}", self.impling_types);
619 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
620 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
622 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
623 or a manual implementation",
624 cx.tcx.def_path_str(debug)
633 pub ANONYMOUS_PARAMETERS,
635 "detects anonymous parameters",
636 @future_incompatible = FutureIncompatibleInfo {
637 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
638 edition: Some(Edition::Edition2018),
643 /// Checks for use of anonymous parameters (RFC 1685).
644 AnonymousParameters => [ANONYMOUS_PARAMETERS]
647 impl EarlyLintPass for AnonymousParameters {
648 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
649 if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
650 for arg in sig.decl.inputs.iter() {
651 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
652 if ident.name == kw::Invalid {
653 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
654 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
656 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
657 (snip.as_str(), Applicability::MachineApplicable)
659 ("<type>", Applicability::HasPlaceholders)
663 "anonymous parameters are deprecated and will be \
664 removed in the next edition.",
668 "try naming the parameter or explicitly \
670 format!("_: {}", ty_snip),
682 /// Check for use of attributes which have been deprecated.
684 pub struct DeprecatedAttr {
685 // This is not free to compute, so we want to keep it around, rather than
686 // compute it for every attribute.
687 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
690 impl_lint_pass!(DeprecatedAttr => []);
692 impl DeprecatedAttr {
693 pub fn new() -> DeprecatedAttr {
694 DeprecatedAttr { depr_attrs: deprecated_attributes() }
698 fn lint_deprecated_attr(
699 cx: &EarlyContext<'_>,
700 attr: &ast::Attribute,
702 suggestion: Option<&str>,
704 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
706 .span_suggestion_short(
708 suggestion.unwrap_or("remove this attribute"),
710 Applicability::MachineApplicable,
716 impl EarlyLintPass for DeprecatedAttr {
717 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
718 for &&(n, _, _, ref g) in &self.depr_attrs {
719 if attr.ident().map(|ident| ident.name) == Some(n) {
720 if let &AttributeGate::Gated(
721 Stability::Deprecated(link, suggestion),
728 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
729 lint_deprecated_attr(cx, attr, &msg, suggestion);
734 if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
735 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
736 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
737 lint_deprecated_attr(cx, attr, &msg, None);
742 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
743 let mut attrs = attrs.iter().peekable();
745 // Accumulate a single span for sugared doc comments.
746 let mut sugared_span: Option<Span> = None;
748 while let Some(attr) = attrs.next() {
749 if attr.is_doc_comment() {
751 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
754 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
758 let span = sugared_span.take().unwrap_or_else(|| attr.span);
760 if attr.is_doc_comment() || attr.check_name(sym::doc) {
761 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
762 let mut err = lint.build("unused doc comment");
765 format!("rustdoc does not generate documentation for {}", node_kind),
773 impl EarlyLintPass for UnusedDocComment {
774 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
775 let kind = match stmt.kind {
776 ast::StmtKind::Local(..) => "statements",
777 ast::StmtKind::Item(..) => "inner items",
778 // expressions will be reported by `check_expr`.
780 | ast::StmtKind::Semi(_)
781 | ast::StmtKind::Expr(_)
782 | ast::StmtKind::MacCall(_) => return,
785 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
788 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
789 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
790 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
793 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
794 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
799 NO_MANGLE_CONST_ITEMS,
801 "const items will not have their symbols exported"
805 NO_MANGLE_GENERIC_ITEMS,
807 "generic items must be mangled"
810 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
812 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
813 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
815 hir::ItemKind::Fn(.., ref generics, _) => {
816 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
817 for param in generics.params {
819 GenericParamKind::Lifetime { .. } => {}
820 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
821 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
823 "functions generic over types or consts must be mangled",
825 .span_suggestion_short(
827 "remove this attribute",
829 // Use of `#[no_mangle]` suggests FFI intent; correct
830 // fix may be to monomorphize source by hand
831 Applicability::MaybeIncorrect,
841 hir::ItemKind::Const(..) => {
842 if attr::contains_name(&it.attrs, sym::no_mangle) {
843 // Const items do not refer to a particular location in memory, and therefore
844 // don't have anything to attach a symbol to
845 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
846 let msg = "const items should never be `#[no_mangle]`";
847 let mut err = lint.build(msg);
849 // account for "pub const" (#45562)
854 .span_to_snippet(it.span)
855 .map(|snippet| snippet.find("const").unwrap_or(0))
856 .unwrap_or(0) as u32;
857 // `const` is 5 chars
858 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
861 "try a static value",
862 "pub static".to_owned(),
863 Applicability::MachineApplicable,
877 "mutating transmuted &mut T from &T may cause undefined behavior"
880 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
882 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
883 fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
884 use rustc_target::spec::abi::Abi::RustIntrinsic;
885 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
886 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind))
888 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
889 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
890 consider instead using an UnsafeCell";
891 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
895 fn get_transmute_from_to<'a, 'tcx>(
896 cx: &LateContext<'a, 'tcx>,
897 expr: &hir::Expr<'_>,
898 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
899 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
900 cx.tables.qpath_res(qpath, expr.hir_id)
904 if let Res::Def(DefKind::Fn, did) = def {
905 if !def_id_is_transmute(cx, did) {
908 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
909 let from = sig.inputs().skip_binder()[0];
910 let to = *sig.output().skip_binder();
911 return Some((from, to));
916 fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
917 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
918 && cx.tcx.item_name(def_id) == sym::transmute
926 "enabling unstable features (deprecated. do not use)"
930 /// Forbids using the `#[feature(...)]` attribute
931 UnstableFeatures => [UNSTABLE_FEATURES]
934 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
935 fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
936 if attr.check_name(sym::feature) {
937 if let Some(items) = attr.meta_item_list() {
939 ctx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
940 lint.build("unstable feature").emit()
951 "`pub` items not reachable from crate root"
955 /// Lint for items marked `pub` that aren't reachable from other crates.
956 UnreachablePub => [UNREACHABLE_PUB]
959 impl UnreachablePub {
962 cx: &LateContext<'_, '_>,
965 vis: &hir::Visibility<'_>,
969 let mut applicability = Applicability::MachineApplicable;
971 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
972 if span.from_expansion() {
973 applicability = Applicability::MaybeIncorrect;
975 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
976 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
977 let mut err = lint.build(&format!("unreachable `pub` {}", what));
978 let replacement = if cx.tcx.features().crate_visibility_modifier {
987 "consider restricting its visibility",
992 err.help("or consider exporting it for use by other crates");
1002 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1003 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1004 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1007 fn check_foreign_item(
1009 cx: &LateContext<'_, '_>,
1010 foreign_item: &hir::ForeignItem<'tcx>,
1015 foreign_item.hir_id,
1022 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1023 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1026 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1027 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1034 "bounds in type aliases are not enforced"
1038 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1039 /// They are relevant when using associated types, but otherwise neither checked
1040 /// at definition site nor enforced at use site.
1041 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1044 impl TypeAliasBounds {
1045 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1047 hir::QPath::TypeRelative(ref ty, _) => {
1048 // If this is a type variable, we found a `T::Assoc`.
1050 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1051 Res::Def(DefKind::TyParam, _) => true,
1057 hir::QPath::Resolved(..) => false,
1061 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1062 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1063 // bound. Let's see if this type does that.
1065 // We use a HIR visitor to walk the type.
1066 use rustc_hir::intravisit::{self, Visitor};
1067 struct WalkAssocTypes<'a, 'db> {
1068 err: &'a mut DiagnosticBuilder<'db>,
1070 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1071 type Map = intravisit::ErasedMap<'v>;
1073 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1074 intravisit::NestedVisitorMap::None
1077 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1078 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1081 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1082 associated types in type aliases",
1085 intravisit::walk_qpath(self, qpath, id, span)
1089 // Let's go for a walk!
1090 let mut visitor = WalkAssocTypes { err };
1091 visitor.visit_ty(ty);
1095 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1096 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1097 let (ty, type_alias_generics) = match item.kind {
1098 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1101 let mut suggested_changing_assoc_types = false;
1102 // There must not be a where clause
1103 if !type_alias_generics.where_clause.predicates.is_empty() {
1107 let mut err = lint.build("where clauses are not enforced in type aliases");
1108 let spans: Vec<_> = type_alias_generics
1112 .map(|pred| pred.span())
1114 err.set_span(spans);
1115 err.span_suggestion(
1116 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1117 "the clause will not be checked when the type alias is used, and should be removed",
1119 Applicability::MachineApplicable,
1121 if !suggested_changing_assoc_types {
1122 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1123 suggested_changing_assoc_types = true;
1129 // The parameters must not have bounds
1130 for param in type_alias_generics.params.iter() {
1131 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1132 let suggestion = spans
1135 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1136 (start.to(*sp), String::new())
1139 if !spans.is_empty() {
1140 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1142 lint.build("bounds on generic parameters are not enforced in type aliases");
1143 let msg = "the bound will not be checked when the type alias is used, \
1144 and should be removed";
1145 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1146 if !suggested_changing_assoc_types {
1147 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1148 suggested_changing_assoc_types = true;
1158 /// Lint constants that are erroneous.
1159 /// Without this lint, we might not get any diagnostic if the constant is
1160 /// unused within this crate, even though downstream crates can't use it
1161 /// without producing an error.
1162 UnusedBrokenConst => []
1165 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1166 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1167 // trigger the query once for all constants since that will already report the errors
1168 // FIXME: Use ensure here
1169 let _ = cx.tcx.const_eval_poly(def_id);
1172 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1173 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1175 hir::ItemKind::Const(_, body_id) => {
1176 check_const(cx, body_id);
1178 hir::ItemKind::Static(_, _, body_id) => {
1179 check_const(cx, body_id);
1189 "these bounds don't depend on an type parameters"
1193 /// Lint for trait and lifetime bounds that don't depend on type parameters
1194 /// which either do nothing, or stop the item from being used.
1195 TrivialConstraints => [TRIVIAL_BOUNDS]
1198 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1199 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1200 use rustc_middle::ty::fold::TypeFoldable;
1201 use rustc_middle::ty::Predicate::*;
1203 if cx.tcx.features().trivial_bounds {
1204 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1205 let predicates = cx.tcx.predicates_of(def_id);
1206 for &(predicate, span) in predicates.predicates {
1207 let predicate_kind_name = match predicate {
1208 Trait(..) => "Trait",
1210 RegionOutlives(..) => "Lifetime",
1212 // Ignore projections, as they can only be global
1213 // if the trait bound is global
1215 // Ignore bounds that a user can't type
1220 ConstEvaluatable(..) => continue,
1222 if predicate.is_global() {
1223 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1224 lint.build(&format!(
1225 "{} bound {} does not depend on any type \
1226 or lifetime parameters",
1227 predicate_kind_name, predicate
1238 /// Does nothing as a lint pass, but registers some `Lint`s
1239 /// which are used by other parts of the compiler.
1243 NON_SHORTHAND_FIELD_PATTERNS,
1246 MISSING_COPY_IMPLEMENTATIONS,
1247 MISSING_DEBUG_IMPLEMENTATIONS,
1248 ANONYMOUS_PARAMETERS,
1249 UNUSED_DOC_COMMENTS,
1250 NO_MANGLE_CONST_ITEMS,
1251 NO_MANGLE_GENERIC_ITEMS,
1261 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1263 "`...` range patterns are deprecated"
1267 pub struct EllipsisInclusiveRangePatterns {
1268 /// If `Some(_)`, suppress all subsequent pattern
1269 /// warnings for better diagnostics.
1270 node_id: Option<ast::NodeId>,
1273 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1275 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1276 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1277 if self.node_id.is_some() {
1278 // Don't recursively warn about patterns inside range endpoints.
1282 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1284 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1285 /// corresponding to the ellipsis.
1286 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1291 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1292 ) => Some((a.as_deref(), b, *span)),
1297 let (parenthesise, endpoints) = match &pat.kind {
1298 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1299 _ => (false, matches_ellipsis_pat(pat)),
1302 if let Some((start, end, join)) = endpoints {
1303 let msg = "`...` range patterns are deprecated";
1304 let suggestion = "use `..=` for an inclusive range";
1306 self.node_id = Some(pat.id);
1307 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1308 let end = expr_to_string(&end);
1309 let replace = match start {
1310 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1311 None => format!("&(..={})", end),
1318 Applicability::MachineApplicable,
1323 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1325 .span_suggestion_short(
1329 Applicability::MachineApplicable,
1337 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1338 if let Some(node_id) = self.node_id {
1339 if pat.id == node_id {
1347 UNNAMEABLE_TEST_ITEMS,
1349 "detects an item that cannot be named being marked as `#[test_case]`",
1350 report_in_external_macro
1353 pub struct UnnameableTestItems {
1354 boundary: hir::HirId, // HirId of the item under which things are not nameable
1355 items_nameable: bool,
1358 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1360 impl UnnameableTestItems {
1361 pub fn new() -> Self {
1362 Self { boundary: hir::DUMMY_HIR_ID, items_nameable: true }
1366 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1367 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1368 if self.items_nameable {
1369 if let hir::ItemKind::Mod(..) = it.kind {
1371 self.items_nameable = false;
1372 self.boundary = it.hir_id;
1377 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1378 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1379 lint.build("cannot test inner items").emit()
1384 fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1385 if !self.items_nameable && self.boundary == it.hir_id {
1386 self.items_nameable = true;
1394 "detects edition keywords being used as an identifier",
1395 @future_incompatible = FutureIncompatibleInfo {
1396 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1397 edition: Some(Edition::Edition2018),
1402 /// Check for uses of edition keywords used as an identifier.
1403 KeywordIdents => [KEYWORD_IDENTS]
1406 struct UnderMacro(bool);
1408 impl KeywordIdents {
1409 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1410 for tt in tokens.into_trees() {
1412 // Only report non-raw idents.
1413 TokenTree::Token(token) => {
1414 if let Some((ident, false)) = token.ident() {
1415 self.check_ident_token(cx, UnderMacro(true), ident);
1418 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1423 fn check_ident_token(
1425 cx: &EarlyContext<'_>,
1426 UnderMacro(under_macro): UnderMacro,
1429 let next_edition = match cx.sess.edition() {
1430 Edition::Edition2015 => {
1432 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1434 // rust-lang/rust#56327: Conservatively do not
1435 // attempt to report occurrences of `dyn` within
1436 // macro definitions or invocations, because `dyn`
1437 // can legitimately occur as a contextual keyword
1438 // in 2015 code denoting its 2018 meaning, and we
1439 // do not want rustfix to inject bugs into working
1440 // code by rewriting such occurrences.
1442 // But if we see `dyn` outside of a macro, we know
1443 // its precise role in the parsed AST and thus are
1444 // assured this is truly an attempt to use it as
1446 kw::Dyn if !under_macro => Edition::Edition2018,
1452 // There are no new keywords yet for the 2018 edition and beyond.
1456 // Don't lint `r#foo`.
1457 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1461 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1462 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1465 "you can use a raw identifier to stay compatible",
1466 format!("r#{}", ident),
1467 Applicability::MachineApplicable,
1474 impl EarlyLintPass for KeywordIdents {
1475 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1476 self.check_tokens(cx, mac_def.body.inner_tokens());
1478 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1479 self.check_tokens(cx, mac.args.inner_tokens());
1481 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1482 self.check_ident_token(cx, UnderMacro(false), ident);
1486 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1488 impl ExplicitOutlivesRequirements {
1489 fn lifetimes_outliving_lifetime<'tcx>(
1490 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1492 ) -> Vec<ty::Region<'tcx>> {
1495 .filter_map(|(pred, _)| match pred {
1496 ty::Predicate::RegionOutlives(outlives) => {
1497 let outlives = outlives.skip_binder();
1499 ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1508 fn lifetimes_outliving_type<'tcx>(
1509 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1511 ) -> Vec<ty::Region<'tcx>> {
1514 .filter_map(|(pred, _)| match pred {
1515 ty::Predicate::TypeOutlives(outlives) => {
1516 let outlives = outlives.skip_binder();
1517 outlives.0.is_param(index).then_some(outlives.1)
1524 fn collect_outlived_lifetimes<'tcx>(
1526 param: &'tcx hir::GenericParam<'tcx>,
1528 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1529 ty_generics: &'tcx ty::Generics,
1530 ) -> Vec<ty::Region<'tcx>> {
1531 let index = ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id)];
1534 hir::GenericParamKind::Lifetime { .. } => {
1535 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1537 hir::GenericParamKind::Type { .. } => {
1538 Self::lifetimes_outliving_type(inferred_outlives, index)
1540 hir::GenericParamKind::Const { .. } => Vec::new(),
1544 fn collect_outlives_bound_spans<'tcx>(
1547 bounds: &hir::GenericBounds<'_>,
1548 inferred_outlives: &[ty::Region<'tcx>],
1550 ) -> Vec<(usize, Span)> {
1551 use rustc_middle::middle::resolve_lifetime::Region;
1556 .filter_map(|(i, bound)| {
1557 if let hir::GenericBound::Outlives(lifetime) = bound {
1558 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1559 Some(Region::Static) if infer_static => inferred_outlives
1561 .any(|r| if let ty::ReStatic = r { true } else { false }),
1562 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1563 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1567 is_inferred.then_some((i, bound.span()))
1575 fn consolidate_outlives_bound_spans(
1578 bounds: &hir::GenericBounds<'_>,
1579 bound_spans: Vec<(usize, Span)>,
1581 if bounds.is_empty() {
1584 if bound_spans.len() == bounds.len() {
1585 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1586 // If all bounds are inferable, we want to delete the colon, so
1587 // start from just after the parameter (span passed as argument)
1588 vec![lo.to(last_bound_span)]
1590 let mut merged = Vec::new();
1591 let mut last_merged_i = None;
1593 let mut from_start = true;
1594 for (i, bound_span) in bound_spans {
1595 match last_merged_i {
1596 // If the first bound is inferable, our span should also eat the leading `+`.
1598 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1599 last_merged_i = Some(0);
1601 // If consecutive bounds are inferable, merge their spans
1602 Some(h) if i == h + 1 => {
1603 if let Some(tail) = merged.last_mut() {
1604 // Also eat the trailing `+` if the first
1605 // more-than-one bound is inferable
1606 let to_span = if from_start && i < bounds.len() {
1607 bounds[i + 1].span().shrink_to_lo()
1611 *tail = tail.to(to_span);
1612 last_merged_i = Some(i);
1614 bug!("another bound-span visited earlier");
1618 // When we find a non-inferable bound, subsequent inferable bounds
1619 // won't be consecutive from the start (and we'll eat the leading
1620 // `+` rather than the trailing one)
1622 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1623 last_merged_i = Some(i);
1632 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1633 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1634 use rustc_middle::middle::resolve_lifetime::Region;
1636 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1637 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1638 if let hir::ItemKind::Struct(_, ref hir_generics)
1639 | hir::ItemKind::Enum(_, ref hir_generics)
1640 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1642 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1643 if inferred_outlives.is_empty() {
1647 let ty_generics = cx.tcx.generics_of(def_id);
1649 let mut bound_count = 0;
1650 let mut lint_spans = Vec::new();
1652 for param in hir_generics.params {
1653 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1654 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1656 if !has_lifetime_bounds {
1660 let relevant_lifetimes =
1661 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1662 if relevant_lifetimes.is_empty() {
1666 let bound_spans = self.collect_outlives_bound_spans(
1669 &relevant_lifetimes,
1672 bound_count += bound_spans.len();
1673 lint_spans.extend(self.consolidate_outlives_bound_spans(
1674 param.span.shrink_to_hi(),
1680 let mut where_lint_spans = Vec::new();
1681 let mut dropped_predicate_count = 0;
1682 let num_predicates = hir_generics.where_clause.predicates.len();
1683 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1684 let (relevant_lifetimes, bounds, span) = match where_predicate {
1685 hir::WherePredicate::RegionPredicate(predicate) => {
1686 if let Some(Region::EarlyBound(index, ..)) =
1687 cx.tcx.named_region(predicate.lifetime.hir_id)
1690 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1698 hir::WherePredicate::BoundPredicate(predicate) => {
1699 // FIXME we can also infer bounds on associated types,
1700 // and should check for them here.
1701 match predicate.bounded_ty.kind {
1702 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1703 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1704 let index = ty_generics.param_def_id_to_index[&def_id];
1706 Self::lifetimes_outliving_type(inferred_outlives, index),
1721 if relevant_lifetimes.is_empty() {
1725 let bound_spans = self.collect_outlives_bound_spans(
1728 &relevant_lifetimes,
1731 bound_count += bound_spans.len();
1733 let drop_predicate = bound_spans.len() == bounds.len();
1735 dropped_predicate_count += 1;
1738 // If all the bounds on a predicate were inferable and there are
1739 // further predicates, we want to eat the trailing comma.
1740 if drop_predicate && i + 1 < num_predicates {
1741 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1742 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1744 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1745 span.shrink_to_lo(),
1752 // If all predicates are inferable, drop the entire clause
1753 // (including the `where`)
1754 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1755 let where_span = hir_generics
1758 .expect("span of (nonempty) where clause should exist");
1759 // Extend the where clause back to the closing `>` of the
1760 // generics, except for tuple struct, which have the `where`
1761 // after the fields of the struct.
1762 let full_where_span =
1763 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1766 hir_generics.span.shrink_to_hi().to(where_span)
1768 lint_spans.push(full_where_span);
1770 lint_spans.extend(where_lint_spans);
1773 if !lint_spans.is_empty() {
1774 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1775 lint.build("outlives requirements can be inferred")
1776 .multipart_suggestion(
1777 if bound_count == 1 {
1780 "remove these bounds"
1784 .map(|span| (span, "".to_owned()))
1785 .collect::<Vec<_>>(),
1786 Applicability::MachineApplicable,
1796 pub INCOMPLETE_FEATURES,
1798 "incomplete features that may function improperly in some or all cases"
1802 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1803 IncompleteFeatures => [INCOMPLETE_FEATURES]
1806 impl EarlyLintPass for IncompleteFeatures {
1807 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1808 let features = cx.sess.features_untracked();
1810 .declared_lang_features
1812 .map(|(name, span, _)| (name, span))
1813 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1814 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1815 .for_each(|(name, &span)| {
1816 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1817 lint.build(&format!(
1818 "the feature `{}` is incomplete and may cause the compiler to crash",
1830 "an invalid value is being created (such as a NULL reference)"
1833 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1835 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1836 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1837 #[derive(Debug, Copy, Clone, PartialEq)]
1843 /// Information about why a type cannot be initialized this way.
1844 /// Contains an error message and optionally a span to point at.
1845 type InitError = (String, Option<Span>);
1847 /// Test if this constant is all-0.
1848 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1849 use hir::ExprKind::*;
1850 use rustc_ast::ast::LitKind::*;
1853 if let Int(i, _) = lit.node {
1859 Tup(tup) => tup.iter().all(is_zero),
1864 /// Determine if this expression is a "dangerous initialization".
1865 fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1866 // `transmute` is inside an anonymous module (the `extern` block?);
1867 // `Invalid` represents the empty string and matches that.
1868 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1869 // on intrinsics right now.
1870 const TRANSMUTE_PATH: &[Symbol] =
1871 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1873 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1874 // Find calls to `mem::{uninitialized,zeroed}` methods.
1875 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1876 let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1878 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1879 return Some(InitKind::Zeroed);
1880 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1881 return Some(InitKind::Uninit);
1882 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1883 if is_zero(&args[0]) {
1884 return Some(InitKind::Zeroed);
1888 } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
1889 // Find problematic calls to `MaybeUninit::assume_init`.
1890 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1891 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1892 // This is a call to *some* method named `assume_init`.
1893 // See if the `self` parameter is one of the dangerous constructors.
1894 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1895 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1897 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1899 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1900 return Some(InitKind::Zeroed);
1901 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1902 return Some(InitKind::Uninit);
1912 /// Return `Some` only if we are sure this type does *not*
1913 /// allow zero initialization.
1914 fn ty_find_init_error<'tcx>(
1918 ) -> Option<InitError> {
1919 use rustc_middle::ty::TyKind::*;
1921 // Primitive types that don't like 0 as a value.
1922 Ref(..) => Some(("references must be non-null".to_string(), None)),
1923 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1924 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1925 Never => Some(("the `!` type has no valid value".to_string(), None)),
1926 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1927 // raw ptr to dyn Trait
1929 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1931 // Primitive types with other constraints.
1932 Bool if init == InitKind::Uninit => {
1933 Some(("booleans must be either `true` or `false`".to_string(), None))
1935 Char if init == InitKind::Uninit => {
1936 Some(("characters must be a valid Unicode codepoint".to_string(), None))
1938 // Recurse and checks for some compound types.
1939 Adt(adt_def, substs) if !adt_def.is_union() => {
1940 // First check f this ADT has a layout attribute (like `NonNull` and friends).
1941 use std::ops::Bound;
1942 match tcx.layout_scalar_valid_range(adt_def.did) {
1943 // We exploit here that `layout_scalar_valid_range` will never
1944 // return `Bound::Excluded`. (And we have tests checking that we
1945 // handle the attribute correctly.)
1946 (Bound::Included(lo), _) if lo > 0 => {
1947 return Some((format!("`{}` must be non-null", ty), None));
1949 (Bound::Included(_), _) | (_, Bound::Included(_))
1950 if init == InitKind::Uninit =>
1954 "`{}` must be initialized inside its custom valid range",
1963 match adt_def.variants.len() {
1964 0 => Some(("enums with no variants have no valid value".to_string(), None)),
1966 // Struct, or enum with exactly one variant.
1967 // Proceed recursively, check all fields.
1968 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1969 variant.fields.iter().find_map(|field| {
1970 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1973 // Point to this field, should be helpful for figuring
1974 // out where the source of the error is.
1975 let span = tcx.def_span(field.did);
1978 " (in this {} field)",
1991 // Multi-variant enums are tricky: if all but one variant are
1992 // uninhabited, we might actually do layout like for a single-variant
1993 // enum, and then even leaving them uninitialized could be okay.
1994 _ => None, // Conservative fallback for multi-variant enum.
1998 // Proceed recursively, check all fields.
1999 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2001 // Conservative fallback.
2006 if let Some(init) = is_dangerous_init(cx, expr) {
2007 // This conjures an instance of a type out of nothing,
2008 // using zeroed or uninitialized memory.
2009 // We are extremely conservative with what we warn about.
2010 let conjured_ty = cx.tables.expr_ty(expr);
2011 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2012 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2013 let mut err = lint.build(&format!(
2014 "the type `{}` does not permit {}",
2017 InitKind::Zeroed => "zero-initialization",
2018 InitKind::Uninit => "being left uninitialized",
2021 err.span_label(expr.span, "this code causes undefined behavior when executed");
2024 "help: use `MaybeUninit<T>` instead, \
2025 and only call `assume_init` after initialization is done",
2027 if let Some(span) = span {
2028 err.span_note(span, &msg);