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::{FxHashMap, FxHashSet};
30 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
31 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
32 use rustc_feature::{GateIssue, Stability};
34 use rustc_hir::def::{DefKind, Res};
35 use rustc_hir::def_id::DefId;
36 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
37 use rustc_hir::{HirId, HirIdSet, Node};
38 use rustc_middle::lint::LintDiagnosticBuilder;
39 use rustc_middle::ty::subst::GenericArgKind;
40 use rustc_middle::ty::{self, Ty, TyCtxt};
41 use rustc_session::lint::FutureIncompatibleInfo;
42 use rustc_span::edition::Edition;
43 use rustc_span::source_map::Spanned;
44 use rustc_span::symbol::{kw, sym, Ident, Symbol};
45 use rustc_span::{BytePos, Span};
46 use rustc_target::abi::VariantIdx;
47 use rustc_trait_selection::traits::misc::can_type_implement_copy;
49 use crate::nonstandard_style::{method_context, MethodLateContext};
51 use log::{debug, trace};
54 // hardwired lints from librustc_middle
55 pub use rustc_session::lint::builtin::*;
60 "suggest using `loop { }` instead of `while true { }`"
63 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
65 /// Traverse through any amount of parenthesis and return the first non-parens expression.
66 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
67 while let ast::ExprKind::Paren(sub) = &expr.kind {
73 impl EarlyLintPass for WhileTrue {
74 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
75 if let ast::ExprKind::While(cond, ..) = &e.kind {
76 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
77 if let ast::LitKind::Bool(true) = lit.kind {
78 if !lit.span.from_expansion() {
79 let msg = "denote infinite loops with `loop { ... }`";
80 let condition_span = cx.sess.source_map().guess_head_span(e.span);
81 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
83 .span_suggestion_short(
87 Applicability::MachineApplicable,
101 "use of owned (Box type) heap memory"
104 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
107 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
108 for leaf in ty.walk() {
109 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
110 if leaf_ty.is_box() {
111 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
112 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
120 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
121 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
123 hir::ItemKind::Fn(..)
124 | hir::ItemKind::TyAlias(..)
125 | hir::ItemKind::Enum(..)
126 | hir::ItemKind::Struct(..)
127 | hir::ItemKind::Union(..) => {
128 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
129 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
134 // If it's a struct, we also have to check the fields' types
136 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
137 for struct_field in struct_def.fields() {
138 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
139 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
146 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
147 let ty = cx.tables().node_type(e.hir_id);
148 self.check_heap_type(cx, e.span, ty);
153 NON_SHORTHAND_FIELD_PATTERNS,
155 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
158 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
160 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
161 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
162 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
167 .expect("struct pattern type is not an ADT")
168 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
169 for fieldpat in field_pats {
170 if fieldpat.is_shorthand {
173 if fieldpat.span.from_expansion() {
174 // Don't lint if this is a macro expansion: macro authors
175 // shouldn't have to worry about this kind of style issue
179 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
180 if cx.tcx.find_field_index(ident, &variant)
181 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables()))
183 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
185 .build(&format!("the `{}:` in this pattern is redundant", ident));
186 let binding = match binding_annot {
187 hir::BindingAnnotation::Unannotated => None,
188 hir::BindingAnnotation::Mutable => Some("mut"),
189 hir::BindingAnnotation::Ref => Some("ref"),
190 hir::BindingAnnotation::RefMut => Some("ref mut"),
192 let ident = if let Some(binding) = binding {
193 format!("{} {}", binding, ident)
199 "use shorthand field pattern",
201 Applicability::MachineApplicable,
215 "usage of `unsafe` code"
218 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
223 cx: &EarlyContext<'_>,
225 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
227 // This comes from a macro that has `#[allow_internal_unsafe]`.
228 if span.allows_unsafe() {
232 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
236 impl EarlyLintPass for UnsafeCode {
237 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
238 if attr.check_name(sym::allow_internal_unsafe) {
239 self.report_unsafe(cx, attr.span, |lint| {
241 "`allow_internal_unsafe` allows defining \
242 macros using unsafe without triggering \
243 the `unsafe_code` lint at their call site",
250 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
251 if let ast::ExprKind::Block(ref blk, _) = e.kind {
252 // Don't warn about generated blocks; that'll just pollute the output.
253 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
254 self.report_unsafe(cx, blk.span, |lint| {
255 lint.build("usage of an `unsafe` block").emit()
261 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
263 ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
264 self.report_unsafe(cx, it.span, |lint| {
265 lint.build("declaration of an `unsafe` trait").emit()
269 ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
270 self.report_unsafe(cx, it.span, |lint| {
271 lint.build("implementation of an `unsafe` trait").emit()
279 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
283 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
288 let msg = match ctxt {
289 FnCtxt::Foreign => return,
290 FnCtxt::Free => "declaration of an `unsafe` function",
291 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
292 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
294 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
302 "detects missing documentation for public members",
303 report_in_external_macro
306 pub struct MissingDoc {
307 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
308 doc_hidden_stack: Vec<bool>,
310 /// Private traits or trait items that leaked through. Don't check their methods.
311 private_traits: FxHashSet<hir::HirId>,
314 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
316 fn has_doc(attr: &ast::Attribute) -> bool {
317 if attr.is_doc_comment() {
321 if !attr.check_name(sym::doc) {
325 if attr.is_value_str() {
329 if let Some(list) = attr.meta_item_list() {
331 if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
341 pub fn new() -> MissingDoc {
342 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
345 fn doc_hidden(&self) -> bool {
346 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
349 fn check_missing_docs_attrs(
351 cx: &LateContext<'_>,
352 id: Option<hir::HirId>,
353 attrs: &[ast::Attribute],
355 article: &'static str,
358 // If we're building a test harness, then warning about
359 // documentation is probably not really relevant right now.
360 if cx.sess().opts.test {
364 // `#[doc(hidden)]` disables missing_docs check.
365 if self.doc_hidden() {
369 // Only check publicly-visible items, using the result from the privacy pass.
370 // It's an option so the crate root can also use this function (it doesn't
372 if let Some(id) = id {
373 if !cx.access_levels.is_exported(id) {
378 let has_doc = attrs.iter().any(|a| has_doc(a));
382 cx.tcx.sess.source_map().guess_head_span(sp),
384 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
391 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
392 fn enter_lint_attrs(&mut self, _: &LateContext<'_>, attrs: &[ast::Attribute]) {
393 let doc_hidden = self.doc_hidden()
394 || attrs.iter().any(|attr| {
395 attr.check_name(sym::doc)
396 && match attr.meta_item_list() {
398 Some(l) => attr::list_contains_name(&l, sym::hidden),
401 self.doc_hidden_stack.push(doc_hidden);
404 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
405 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
408 fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
409 self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
411 for macro_def in krate.exported_macros {
412 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
416 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
417 |lint| lint.build("missing documentation for macro").emit(),
423 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
425 hir::ItemKind::Trait(.., trait_item_refs) => {
426 // Issue #11592: traits are always considered exported, even when private.
427 if let hir::VisibilityKind::Inherited = it.vis.node {
428 self.private_traits.insert(it.hir_id);
429 for trait_item_ref in trait_item_refs {
430 self.private_traits.insert(trait_item_ref.id.hir_id);
435 hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
436 // If the trait is private, add the impl items to `private_traits` so they don't get
437 // reported for missing docs.
438 let real_trait = trait_ref.path.res.def_id();
439 if let Some(def_id) = real_trait.as_local() {
440 let hir_id = cx.tcx.hir().as_local_hir_id(def_id);
441 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
442 if let hir::VisibilityKind::Inherited = item.vis.node {
443 for impl_item_ref in items {
444 self.private_traits.insert(impl_item_ref.id.hir_id);
452 hir::ItemKind::TyAlias(..)
453 | hir::ItemKind::Fn(..)
454 | hir::ItemKind::Mod(..)
455 | hir::ItemKind::Enum(..)
456 | hir::ItemKind::Struct(..)
457 | hir::ItemKind::Union(..)
458 | hir::ItemKind::Const(..)
459 | hir::ItemKind::Static(..) => {}
464 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
465 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
467 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
470 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
471 if self.private_traits.contains(&trait_item.hir_id) {
475 let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
476 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
478 self.check_missing_docs_attrs(
480 Some(trait_item.hir_id),
488 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
489 // If the method is an impl for a trait, don't doc.
490 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
494 let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
495 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
496 self.check_missing_docs_attrs(
498 Some(impl_item.hir_id),
506 fn check_struct_field(&mut self, cx: &LateContext<'_>, sf: &hir::StructField<'_>) {
507 if !sf.is_positional() {
508 self.check_missing_docs_attrs(
519 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
520 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
525 pub MISSING_COPY_IMPLEMENTATIONS,
527 "detects potentially-forgotten implementations of `Copy`"
530 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
532 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
533 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
534 if !cx.access_levels.is_reachable(item.hir_id) {
537 let (def, ty) = match item.kind {
538 hir::ItemKind::Struct(_, ref ast_generics) => {
539 if !ast_generics.params.is_empty() {
542 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
543 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
545 hir::ItemKind::Union(_, ref ast_generics) => {
546 if !ast_generics.params.is_empty() {
549 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
550 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
552 hir::ItemKind::Enum(_, ref ast_generics) => {
553 if !ast_generics.params.is_empty() {
556 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
557 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
561 if def.has_dtor(cx.tcx) {
564 let param_env = ty::ParamEnv::empty();
565 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
568 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
569 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
571 "type could implement `Copy`; consider adding `impl \
581 MISSING_DEBUG_IMPLEMENTATIONS,
583 "detects missing implementations of Debug"
587 pub struct MissingDebugImplementations {
588 impling_types: Option<HirIdSet>,
591 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
593 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
594 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
595 if !cx.access_levels.is_reachable(item.hir_id) {
600 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
604 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
605 Some(debug) => debug,
609 if self.impling_types.is_none() {
610 let mut impls = HirIdSet::default();
611 cx.tcx.for_each_impl(debug, |d| {
612 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
613 if let Some(def_id) = ty_def.did.as_local() {
614 impls.insert(cx.tcx.hir().as_local_hir_id(def_id));
619 self.impling_types = Some(impls);
620 debug!("{:?}", self.impling_types);
623 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
624 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
626 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
627 or a manual implementation",
628 cx.tcx.def_path_str(debug)
637 pub ANONYMOUS_PARAMETERS,
639 "detects anonymous parameters",
640 @future_incompatible = FutureIncompatibleInfo {
641 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
642 edition: Some(Edition::Edition2018),
647 /// Checks for use of anonymous parameters (RFC 1685).
648 AnonymousParameters => [ANONYMOUS_PARAMETERS]
651 impl EarlyLintPass for AnonymousParameters {
652 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
653 if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
654 for arg in sig.decl.inputs.iter() {
655 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
656 if ident.name == kw::Invalid {
657 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
658 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
660 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
661 (snip.as_str(), Applicability::MachineApplicable)
663 ("<type>", Applicability::HasPlaceholders)
667 "anonymous parameters are deprecated and will be \
668 removed in the next edition.",
672 "try naming the parameter or explicitly \
674 format!("_: {}", ty_snip),
686 /// Check for use of attributes which have been deprecated.
688 pub struct DeprecatedAttr {
689 // This is not free to compute, so we want to keep it around, rather than
690 // compute it for every attribute.
691 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
694 impl_lint_pass!(DeprecatedAttr => []);
696 impl DeprecatedAttr {
697 pub fn new() -> DeprecatedAttr {
698 DeprecatedAttr { depr_attrs: deprecated_attributes() }
702 fn lint_deprecated_attr(
703 cx: &EarlyContext<'_>,
704 attr: &ast::Attribute,
706 suggestion: Option<&str>,
708 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
710 .span_suggestion_short(
712 suggestion.unwrap_or("remove this attribute"),
714 Applicability::MachineApplicable,
720 impl EarlyLintPass for DeprecatedAttr {
721 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
722 for &&(n, _, _, ref g) in &self.depr_attrs {
723 if attr.ident().map(|ident| ident.name) == Some(n) {
724 if let &AttributeGate::Gated(
725 Stability::Deprecated(link, suggestion),
732 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
733 lint_deprecated_attr(cx, attr, &msg, suggestion);
738 if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
739 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
740 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
741 lint_deprecated_attr(cx, attr, &msg, None);
746 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
747 let mut attrs = attrs.iter().peekable();
749 // Accumulate a single span for sugared doc comments.
750 let mut sugared_span: Option<Span> = None;
752 while let Some(attr) = attrs.next() {
753 if attr.is_doc_comment() {
755 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
758 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
762 let span = sugared_span.take().unwrap_or_else(|| attr.span);
764 if attr.is_doc_comment() || attr.check_name(sym::doc) {
765 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
766 let mut err = lint.build("unused doc comment");
769 format!("rustdoc does not generate documentation for {}", node_kind),
777 impl EarlyLintPass for UnusedDocComment {
778 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
779 let kind = match stmt.kind {
780 ast::StmtKind::Local(..) => "statements",
781 ast::StmtKind::Item(..) => "inner items",
782 // expressions will be reported by `check_expr`.
784 | ast::StmtKind::Semi(_)
785 | ast::StmtKind::Expr(_)
786 | ast::StmtKind::MacCall(_) => return,
789 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
792 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
793 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
794 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
797 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
798 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
803 NO_MANGLE_CONST_ITEMS,
805 "const items will not have their symbols exported"
809 NO_MANGLE_GENERIC_ITEMS,
811 "generic items must be mangled"
814 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
816 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
817 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
819 hir::ItemKind::Fn(.., ref generics, _) => {
820 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
821 for param in generics.params {
823 GenericParamKind::Lifetime { .. } => {}
824 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
825 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
827 "functions generic over types or consts must be mangled",
829 .span_suggestion_short(
831 "remove this attribute",
833 // Use of `#[no_mangle]` suggests FFI intent; correct
834 // fix may be to monomorphize source by hand
835 Applicability::MaybeIncorrect,
845 hir::ItemKind::Const(..) => {
846 if attr::contains_name(&it.attrs, sym::no_mangle) {
847 // Const items do not refer to a particular location in memory, and therefore
848 // don't have anything to attach a symbol to
849 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
850 let msg = "const items should never be `#[no_mangle]`";
851 let mut err = lint.build(msg);
853 // account for "pub const" (#45562)
858 .span_to_snippet(it.span)
859 .map(|snippet| snippet.find("const").unwrap_or(0))
860 .unwrap_or(0) as u32;
861 // `const` is 5 chars
862 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
865 "try a static value",
866 "pub static".to_owned(),
867 Applicability::MachineApplicable,
881 "mutating transmuted &mut T from &T may cause undefined behavior"
884 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
886 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
887 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
888 use rustc_target::spec::abi::Abi::RustIntrinsic;
889 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
890 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind))
892 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
893 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
894 consider instead using an UnsafeCell";
895 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
899 fn get_transmute_from_to<'tcx>(
900 cx: &LateContext<'tcx>,
901 expr: &hir::Expr<'_>,
902 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
903 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
904 cx.qpath_res(qpath, expr.hir_id)
908 if let Res::Def(DefKind::Fn, did) = def {
909 if !def_id_is_transmute(cx, did) {
912 let sig = cx.tables().node_type(expr.hir_id).fn_sig(cx.tcx);
913 let from = sig.inputs().skip_binder()[0];
914 let to = sig.output().skip_binder();
915 return Some((from, to));
920 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
921 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
922 && cx.tcx.item_name(def_id) == sym::transmute
930 "enabling unstable features (deprecated. do not use)"
934 /// Forbids using the `#[feature(...)]` attribute
935 UnstableFeatures => [UNSTABLE_FEATURES]
938 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
939 fn check_attribute(&mut self, ctx: &LateContext<'_>, attr: &ast::Attribute) {
940 if attr.check_name(sym::feature) {
941 if let Some(items) = attr.meta_item_list() {
943 ctx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
944 lint.build("unstable feature").emit()
955 "`pub` items not reachable from crate root"
959 /// Lint for items marked `pub` that aren't reachable from other crates.
960 UnreachablePub => [UNREACHABLE_PUB]
963 impl UnreachablePub {
966 cx: &LateContext<'_>,
969 vis: &hir::Visibility<'_>,
973 let mut applicability = Applicability::MachineApplicable;
975 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
976 if span.from_expansion() {
977 applicability = Applicability::MaybeIncorrect;
979 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
980 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
981 let mut err = lint.build(&format!("unreachable `pub` {}", what));
982 let replacement = if cx.tcx.features().crate_visibility_modifier {
991 "consider restricting its visibility",
996 err.help("or consider exporting it for use by other crates");
1006 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1007 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1008 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1011 fn check_foreign_item(&mut self, cx: &LateContext<'_>, 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<'tcx> LateLintPass<'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 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1102 // Bounds are respected for `type X = impl Trait`
1105 let mut suggested_changing_assoc_types = false;
1106 // There must not be a where clause
1107 if !type_alias_generics.where_clause.predicates.is_empty() {
1111 let mut err = lint.build("where clauses are not enforced in type aliases");
1112 let spans: Vec<_> = type_alias_generics
1116 .map(|pred| pred.span())
1118 err.set_span(spans);
1119 err.span_suggestion(
1120 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1121 "the clause will not be checked when the type alias is used, and should be removed",
1123 Applicability::MachineApplicable,
1125 if !suggested_changing_assoc_types {
1126 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1127 suggested_changing_assoc_types = true;
1133 // The parameters must not have bounds
1134 for param in type_alias_generics.params.iter() {
1135 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1136 let suggestion = spans
1139 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1140 (start.to(*sp), String::new())
1143 if !spans.is_empty() {
1144 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1146 lint.build("bounds on generic parameters are not enforced in type aliases");
1147 let msg = "the bound will not be checked when the type alias is used, \
1148 and should be removed";
1149 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1150 if !suggested_changing_assoc_types {
1151 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1152 suggested_changing_assoc_types = true;
1162 /// Lint constants that are erroneous.
1163 /// Without this lint, we might not get any diagnostic if the constant is
1164 /// unused within this crate, even though downstream crates can't use it
1165 /// without producing an error.
1166 UnusedBrokenConst => []
1169 fn check_const(cx: &LateContext<'_>, body_id: hir::BodyId) {
1170 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1171 // trigger the query once for all constants since that will already report the errors
1172 // FIXME: Use ensure here
1173 let _ = cx.tcx.const_eval_poly(def_id);
1176 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1177 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1179 hir::ItemKind::Const(_, body_id) => {
1180 check_const(cx, body_id);
1182 hir::ItemKind::Static(_, _, body_id) => {
1183 check_const(cx, body_id);
1193 "these bounds don't depend on an type parameters"
1197 /// Lint for trait and lifetime bounds that don't depend on type parameters
1198 /// which either do nothing, or stop the item from being used.
1199 TrivialConstraints => [TRIVIAL_BOUNDS]
1202 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1203 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1204 use rustc_middle::ty::fold::TypeFoldable;
1205 use rustc_middle::ty::PredicateKind::*;
1207 if cx.tcx.features().trivial_bounds {
1208 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1209 let predicates = cx.tcx.predicates_of(def_id);
1210 for &(predicate, span) in predicates.predicates {
1211 let predicate_kind_name = match predicate.kind() {
1212 Trait(..) => "Trait",
1214 RegionOutlives(..) => "Lifetime",
1216 // Ignore projections, as they can only be global
1217 // if the trait bound is global
1219 // Ignore bounds that a user can't type
1224 ConstEvaluatable(..) |
1225 ConstEquate(..) => continue,
1227 if predicate.is_global() {
1228 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1229 lint.build(&format!(
1230 "{} bound {} does not depend on any type \
1231 or lifetime parameters",
1232 predicate_kind_name, predicate
1243 /// Does nothing as a lint pass, but registers some `Lint`s
1244 /// which are used by other parts of the compiler.
1248 NON_SHORTHAND_FIELD_PATTERNS,
1251 MISSING_COPY_IMPLEMENTATIONS,
1252 MISSING_DEBUG_IMPLEMENTATIONS,
1253 ANONYMOUS_PARAMETERS,
1254 UNUSED_DOC_COMMENTS,
1255 NO_MANGLE_CONST_ITEMS,
1256 NO_MANGLE_GENERIC_ITEMS,
1266 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1268 "`...` range patterns are deprecated"
1272 pub struct EllipsisInclusiveRangePatterns {
1273 /// If `Some(_)`, suppress all subsequent pattern
1274 /// warnings for better diagnostics.
1275 node_id: Option<ast::NodeId>,
1278 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1280 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1281 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1282 if self.node_id.is_some() {
1283 // Don't recursively warn about patterns inside range endpoints.
1287 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1289 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1290 /// corresponding to the ellipsis.
1291 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1296 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1297 ) => Some((a.as_deref(), b, *span)),
1302 let (parenthesise, endpoints) = match &pat.kind {
1303 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1304 _ => (false, matches_ellipsis_pat(pat)),
1307 if let Some((start, end, join)) = endpoints {
1308 let msg = "`...` range patterns are deprecated";
1309 let suggestion = "use `..=` for an inclusive range";
1311 self.node_id = Some(pat.id);
1312 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1313 let end = expr_to_string(&end);
1314 let replace = match start {
1315 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1316 None => format!("&(..={})", end),
1323 Applicability::MachineApplicable,
1328 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1330 .span_suggestion_short(
1334 Applicability::MachineApplicable,
1342 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1343 if let Some(node_id) = self.node_id {
1344 if pat.id == node_id {
1352 UNNAMEABLE_TEST_ITEMS,
1354 "detects an item that cannot be named being marked as `#[test_case]`",
1355 report_in_external_macro
1358 pub struct UnnameableTestItems {
1359 boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1360 items_nameable: bool,
1363 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1365 impl UnnameableTestItems {
1366 pub fn new() -> Self {
1367 Self { boundary: None, items_nameable: true }
1371 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1372 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1373 if self.items_nameable {
1374 if let hir::ItemKind::Mod(..) = it.kind {
1376 self.items_nameable = false;
1377 self.boundary = Some(it.hir_id);
1382 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1383 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1384 lint.build("cannot test inner items").emit()
1389 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1390 if !self.items_nameable && self.boundary == Some(it.hir_id) {
1391 self.items_nameable = true;
1399 "detects edition keywords being used as an identifier",
1400 @future_incompatible = FutureIncompatibleInfo {
1401 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1402 edition: Some(Edition::Edition2018),
1407 /// Check for uses of edition keywords used as an identifier.
1408 KeywordIdents => [KEYWORD_IDENTS]
1411 struct UnderMacro(bool);
1413 impl KeywordIdents {
1414 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1415 for tt in tokens.into_trees() {
1417 // Only report non-raw idents.
1418 TokenTree::Token(token) => {
1419 if let Some((ident, false)) = token.ident() {
1420 self.check_ident_token(cx, UnderMacro(true), ident);
1423 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1428 fn check_ident_token(
1430 cx: &EarlyContext<'_>,
1431 UnderMacro(under_macro): UnderMacro,
1434 let next_edition = match cx.sess.edition() {
1435 Edition::Edition2015 => {
1437 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1439 // rust-lang/rust#56327: Conservatively do not
1440 // attempt to report occurrences of `dyn` within
1441 // macro definitions or invocations, because `dyn`
1442 // can legitimately occur as a contextual keyword
1443 // in 2015 code denoting its 2018 meaning, and we
1444 // do not want rustfix to inject bugs into working
1445 // code by rewriting such occurrences.
1447 // But if we see `dyn` outside of a macro, we know
1448 // its precise role in the parsed AST and thus are
1449 // assured this is truly an attempt to use it as
1451 kw::Dyn if !under_macro => Edition::Edition2018,
1457 // There are no new keywords yet for the 2018 edition and beyond.
1461 // Don't lint `r#foo`.
1462 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1466 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1467 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1470 "you can use a raw identifier to stay compatible",
1471 format!("r#{}", ident),
1472 Applicability::MachineApplicable,
1479 impl EarlyLintPass for KeywordIdents {
1480 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1481 self.check_tokens(cx, mac_def.body.inner_tokens());
1483 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1484 self.check_tokens(cx, mac.args.inner_tokens());
1486 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1487 self.check_ident_token(cx, UnderMacro(false), ident);
1491 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1493 impl ExplicitOutlivesRequirements {
1494 fn lifetimes_outliving_lifetime<'tcx>(
1495 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1497 ) -> Vec<ty::Region<'tcx>> {
1500 .filter_map(|(pred, _)| match pred.kind() {
1501 ty::PredicateKind::RegionOutlives(outlives) => {
1502 let outlives = outlives.skip_binder();
1504 ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1513 fn lifetimes_outliving_type<'tcx>(
1514 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1516 ) -> Vec<ty::Region<'tcx>> {
1519 .filter_map(|(pred, _)| match pred.kind() {
1520 ty::PredicateKind::TypeOutlives(outlives) => {
1521 let outlives = outlives.skip_binder();
1522 outlives.0.is_param(index).then_some(outlives.1)
1529 fn collect_outlived_lifetimes<'tcx>(
1531 param: &'tcx hir::GenericParam<'tcx>,
1533 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1534 ty_generics: &'tcx ty::Generics,
1535 ) -> Vec<ty::Region<'tcx>> {
1537 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1540 hir::GenericParamKind::Lifetime { .. } => {
1541 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1543 hir::GenericParamKind::Type { .. } => {
1544 Self::lifetimes_outliving_type(inferred_outlives, index)
1546 hir::GenericParamKind::Const { .. } => Vec::new(),
1550 fn collect_outlives_bound_spans<'tcx>(
1553 bounds: &hir::GenericBounds<'_>,
1554 inferred_outlives: &[ty::Region<'tcx>],
1556 ) -> Vec<(usize, Span)> {
1557 use rustc_middle::middle::resolve_lifetime::Region;
1562 .filter_map(|(i, bound)| {
1563 if let hir::GenericBound::Outlives(lifetime) = bound {
1564 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1565 Some(Region::Static) if infer_static => inferred_outlives
1567 .any(|r| if let ty::ReStatic = r { true } else { false }),
1568 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1569 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1573 is_inferred.then_some((i, bound.span()))
1581 fn consolidate_outlives_bound_spans(
1584 bounds: &hir::GenericBounds<'_>,
1585 bound_spans: Vec<(usize, Span)>,
1587 if bounds.is_empty() {
1590 if bound_spans.len() == bounds.len() {
1591 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1592 // If all bounds are inferable, we want to delete the colon, so
1593 // start from just after the parameter (span passed as argument)
1594 vec![lo.to(last_bound_span)]
1596 let mut merged = Vec::new();
1597 let mut last_merged_i = None;
1599 let mut from_start = true;
1600 for (i, bound_span) in bound_spans {
1601 match last_merged_i {
1602 // If the first bound is inferable, our span should also eat the leading `+`.
1604 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1605 last_merged_i = Some(0);
1607 // If consecutive bounds are inferable, merge their spans
1608 Some(h) if i == h + 1 => {
1609 if let Some(tail) = merged.last_mut() {
1610 // Also eat the trailing `+` if the first
1611 // more-than-one bound is inferable
1612 let to_span = if from_start && i < bounds.len() {
1613 bounds[i + 1].span().shrink_to_lo()
1617 *tail = tail.to(to_span);
1618 last_merged_i = Some(i);
1620 bug!("another bound-span visited earlier");
1624 // When we find a non-inferable bound, subsequent inferable bounds
1625 // won't be consecutive from the start (and we'll eat the leading
1626 // `+` rather than the trailing one)
1628 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1629 last_merged_i = Some(i);
1638 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
1639 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
1640 use rustc_middle::middle::resolve_lifetime::Region;
1642 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1643 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1644 if let hir::ItemKind::Struct(_, ref hir_generics)
1645 | hir::ItemKind::Enum(_, ref hir_generics)
1646 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1648 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1649 if inferred_outlives.is_empty() {
1653 let ty_generics = cx.tcx.generics_of(def_id);
1655 let mut bound_count = 0;
1656 let mut lint_spans = Vec::new();
1658 for param in hir_generics.params {
1659 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1660 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1662 if !has_lifetime_bounds {
1666 let relevant_lifetimes =
1667 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1668 if relevant_lifetimes.is_empty() {
1672 let bound_spans = self.collect_outlives_bound_spans(
1675 &relevant_lifetimes,
1678 bound_count += bound_spans.len();
1679 lint_spans.extend(self.consolidate_outlives_bound_spans(
1680 param.span.shrink_to_hi(),
1686 let mut where_lint_spans = Vec::new();
1687 let mut dropped_predicate_count = 0;
1688 let num_predicates = hir_generics.where_clause.predicates.len();
1689 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1690 let (relevant_lifetimes, bounds, span) = match where_predicate {
1691 hir::WherePredicate::RegionPredicate(predicate) => {
1692 if let Some(Region::EarlyBound(index, ..)) =
1693 cx.tcx.named_region(predicate.lifetime.hir_id)
1696 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1704 hir::WherePredicate::BoundPredicate(predicate) => {
1705 // FIXME we can also infer bounds on associated types,
1706 // and should check for them here.
1707 match predicate.bounded_ty.kind {
1708 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1709 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1710 let index = ty_generics.param_def_id_to_index[&def_id];
1712 Self::lifetimes_outliving_type(inferred_outlives, index),
1727 if relevant_lifetimes.is_empty() {
1731 let bound_spans = self.collect_outlives_bound_spans(
1734 &relevant_lifetimes,
1737 bound_count += bound_spans.len();
1739 let drop_predicate = bound_spans.len() == bounds.len();
1741 dropped_predicate_count += 1;
1744 // If all the bounds on a predicate were inferable and there are
1745 // further predicates, we want to eat the trailing comma.
1746 if drop_predicate && i + 1 < num_predicates {
1747 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1748 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1750 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1751 span.shrink_to_lo(),
1758 // If all predicates are inferable, drop the entire clause
1759 // (including the `where`)
1760 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1761 let where_span = hir_generics
1764 .expect("span of (nonempty) where clause should exist");
1765 // Extend the where clause back to the closing `>` of the
1766 // generics, except for tuple struct, which have the `where`
1767 // after the fields of the struct.
1768 let full_where_span =
1769 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1772 hir_generics.span.shrink_to_hi().to(where_span)
1774 lint_spans.push(full_where_span);
1776 lint_spans.extend(where_lint_spans);
1779 if !lint_spans.is_empty() {
1780 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1781 lint.build("outlives requirements can be inferred")
1782 .multipart_suggestion(
1783 if bound_count == 1 {
1786 "remove these bounds"
1790 .map(|span| (span, "".to_owned()))
1791 .collect::<Vec<_>>(),
1792 Applicability::MachineApplicable,
1802 pub INCOMPLETE_FEATURES,
1804 "incomplete features that may function improperly in some or all cases"
1808 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1809 IncompleteFeatures => [INCOMPLETE_FEATURES]
1812 impl EarlyLintPass for IncompleteFeatures {
1813 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1814 let features = cx.sess.features_untracked();
1816 .declared_lang_features
1818 .map(|(name, span, _)| (name, span))
1819 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1820 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1821 .for_each(|(&name, &span)| {
1822 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1823 let mut builder = lint.build(&format!(
1824 "the feature `{}` is incomplete and may not be safe to use \
1825 and/or cause compiler crashes",
1828 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
1829 builder.note(&format!(
1830 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
1831 for more information",
1844 "an invalid value is being created (such as a NULL reference)"
1847 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1849 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
1850 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
1851 #[derive(Debug, Copy, Clone, PartialEq)]
1857 /// Information about why a type cannot be initialized this way.
1858 /// Contains an error message and optionally a span to point at.
1859 type InitError = (String, Option<Span>);
1861 /// Test if this constant is all-0.
1862 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1863 use hir::ExprKind::*;
1864 use rustc_ast::ast::LitKind::*;
1867 if let Int(i, _) = lit.node {
1873 Tup(tup) => tup.iter().all(is_zero),
1878 /// Determine if this expression is a "dangerous initialization".
1879 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1880 // `transmute` is inside an anonymous module (the `extern` block?);
1881 // `Invalid` represents the empty string and matches that.
1882 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1883 // on intrinsics right now.
1884 const TRANSMUTE_PATH: &[Symbol] =
1885 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1887 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1888 // Find calls to `mem::{uninitialized,zeroed}` methods.
1889 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1890 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1892 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1893 return Some(InitKind::Zeroed);
1894 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1895 return Some(InitKind::Uninit);
1896 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1897 if is_zero(&args[0]) {
1898 return Some(InitKind::Zeroed);
1902 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
1903 // Find problematic calls to `MaybeUninit::assume_init`.
1904 let def_id = cx.tables().type_dependent_def_id(expr.hir_id)?;
1905 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1906 // This is a call to *some* method named `assume_init`.
1907 // See if the `self` parameter is one of the dangerous constructors.
1908 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1909 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1910 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1912 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1913 return Some(InitKind::Zeroed);
1914 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1915 return Some(InitKind::Uninit);
1925 /// Return `Some` only if we are sure this type does *not*
1926 /// allow zero initialization.
1927 fn ty_find_init_error<'tcx>(
1931 ) -> Option<InitError> {
1932 use rustc_middle::ty::TyKind::*;
1934 // Primitive types that don't like 0 as a value.
1935 Ref(..) => Some(("references must be non-null".to_string(), None)),
1936 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1937 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1938 Never => Some(("the `!` type has no valid value".to_string(), None)),
1939 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1940 // raw ptr to dyn Trait
1942 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1944 // Primitive types with other constraints.
1945 Bool if init == InitKind::Uninit => {
1946 Some(("booleans must be either `true` or `false`".to_string(), None))
1948 Char if init == InitKind::Uninit => {
1949 Some(("characters must be a valid Unicode codepoint".to_string(), None))
1951 // Recurse and checks for some compound types.
1952 Adt(adt_def, substs) if !adt_def.is_union() => {
1953 // First check f this ADT has a layout attribute (like `NonNull` and friends).
1954 use std::ops::Bound;
1955 match tcx.layout_scalar_valid_range(adt_def.did) {
1956 // We exploit here that `layout_scalar_valid_range` will never
1957 // return `Bound::Excluded`. (And we have tests checking that we
1958 // handle the attribute correctly.)
1959 (Bound::Included(lo), _) if lo > 0 => {
1960 return Some((format!("`{}` must be non-null", ty), None));
1962 (Bound::Included(_), _) | (_, Bound::Included(_))
1963 if init == InitKind::Uninit =>
1967 "`{}` must be initialized inside its custom valid range",
1976 match adt_def.variants.len() {
1977 0 => Some(("enums with no variants have no valid value".to_string(), None)),
1979 // Struct, or enum with exactly one variant.
1980 // Proceed recursively, check all fields.
1981 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1982 variant.fields.iter().find_map(|field| {
1983 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1986 // Point to this field, should be helpful for figuring
1987 // out where the source of the error is.
1988 let span = tcx.def_span(field.did);
1991 " (in this {} field)",
2004 // Multi-variant enums are tricky: if all but one variant are
2005 // uninhabited, we might actually do layout like for a single-variant
2006 // enum, and then even leaving them uninitialized could be okay.
2007 _ => None, // Conservative fallback for multi-variant enum.
2011 // Proceed recursively, check all fields.
2012 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2014 // Conservative fallback.
2019 if let Some(init) = is_dangerous_init(cx, expr) {
2020 // This conjures an instance of a type out of nothing,
2021 // using zeroed or uninitialized memory.
2022 // We are extremely conservative with what we warn about.
2023 let conjured_ty = cx.tables().expr_ty(expr);
2024 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2025 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2026 let mut err = lint.build(&format!(
2027 "the type `{}` does not permit {}",
2030 InitKind::Zeroed => "zero-initialization",
2031 InitKind::Uninit => "being left uninitialized",
2034 err.span_label(expr.span, "this code causes undefined behavior when executed");
2037 "help: use `MaybeUninit<T>` instead, \
2038 and only call `assume_init` after initialization is done",
2040 if let Some(span) = span {
2041 err.span_note(span, &msg);
2053 pub CLASHING_EXTERN_DECLARATIONS,
2055 "detects when an extern fn has been declared with the same name but different types"
2058 pub struct ClashingExternDeclarations {
2059 seen_decls: FxHashMap<Symbol, HirId>,
2062 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2063 /// just from declaration itself. This is important because we don't want to report clashes on
2064 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2067 /// The name of the symbol + the span of the annotation which introduced the link name.
2069 /// No link name, so just the name of the symbol.
2074 fn get_name(&self) -> Symbol {
2076 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2081 impl ClashingExternDeclarations {
2082 crate fn new() -> Self {
2083 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2085 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2086 /// for the item, return its HirId without updating the set.
2087 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2088 let hid = fi.hir_id;
2091 &tcx.codegen_fn_attrs(tcx.hir().local_def_id(hid)).link_name.unwrap_or(fi.ident.name);
2093 if self.seen_decls.contains_key(name) {
2094 // Avoid updating the map with the new entry when we do find a collision. We want to
2095 // make sure we're always pointing to the first definition as the previous declaration.
2096 // This lets us avoid emitting "knock-on" diagnostics.
2097 Some(*self.seen_decls.get(name).unwrap())
2099 self.seen_decls.insert(*name, hid)
2103 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2104 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2106 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2107 let did = tcx.hir().local_def_id(fi.hir_id);
2108 if let Some((overridden_link_name, overridden_link_name_span)) =
2109 tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2110 // FIXME: Instead of searching through the attributes again to get span
2111 // information, we could have codegen_fn_attrs also give span information back for
2112 // where the attribute was defined. However, until this is found to be a
2113 // bottleneck, this does just fine.
2115 overridden_link_name,
2116 tcx.get_attrs(did.to_def_id())
2118 .find(|at| at.check_name(sym::link_name))
2124 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2126 SymbolName::Normal(fi.ident.name)
2130 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2131 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2132 /// with the same members (as the declarations shouldn't clash).
2133 fn structurally_same_type<'tcx>(cx: &LateContext<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
2135 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2136 // All nominally-same types are structurally same, too.
2139 // Do a full, depth-first comparison between the two.
2140 use rustc_middle::ty::TyKind::*;
2141 let a_kind = &a.kind;
2142 let b_kind = &b.kind;
2144 match (a_kind, b_kind) {
2145 (Adt(..), Adt(..)) => {
2146 // Adts are pretty straightforward: just compare the layouts.
2147 use rustc_target::abi::LayoutOf;
2148 let a_layout = cx.layout_of(a).unwrap().layout;
2149 let b_layout = cx.layout_of(b).unwrap().layout;
2150 a_layout == b_layout
2152 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2153 // For arrays, we also check the constness of the type.
2154 a_const.val == b_const.val
2155 && Self::structurally_same_type(cx, a_const.ty, b_const.ty)
2156 && Self::structurally_same_type(cx, a_ty, b_ty)
2158 (Slice(a_ty), Slice(b_ty)) => Self::structurally_same_type(cx, a_ty, b_ty),
2159 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2160 a_tymut.mutbl == a_tymut.mutbl
2161 && Self::structurally_same_type(cx, &a_tymut.ty, &b_tymut.ty)
2163 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2164 // For structural sameness, we don't need the region to be same.
2165 a_mut == b_mut && Self::structurally_same_type(cx, a_ty, b_ty)
2167 (FnDef(..), FnDef(..)) => {
2168 // As we don't compare regions, skip_binder is fine.
2169 let a_poly_sig = a.fn_sig(tcx);
2170 let b_poly_sig = b.fn_sig(tcx);
2172 let a_sig = a_poly_sig.skip_binder();
2173 let b_sig = b_poly_sig.skip_binder();
2175 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2176 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2177 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2178 Self::structurally_same_type(cx, a, b)
2180 && Self::structurally_same_type(cx, a_sig.output(), b_sig.output())
2182 (Tuple(a_substs), Tuple(b_substs)) => {
2183 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2184 Self::structurally_same_type(cx, a_ty, b_ty)
2187 // For these, it's not quite as easy to define structural-sameness quite so easily.
2188 // For the purposes of this lint, take the conservative approach and mark them as
2189 // not structurally same.
2190 (Dynamic(..), Dynamic(..))
2191 | (Error(..), Error(..))
2192 | (Closure(..), Closure(..))
2193 | (Generator(..), Generator(..))
2194 | (GeneratorWitness(..), GeneratorWitness(..))
2195 | (Projection(..), Projection(..))
2196 | (Opaque(..), Opaque(..)) => false,
2197 // These definitely should have been caught above.
2198 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2205 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2207 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2208 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2209 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2210 if let ForeignItemKind::Fn(..) = this_fi.kind {
2212 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2213 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2214 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2216 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2217 existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2219 // Check that the declarations match.
2220 if !Self::structurally_same_type(cx, existing_decl_ty, this_decl_ty) {
2221 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2222 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2224 // We want to ensure that we use spans for both decls that include where the
2225 // name was defined, whether that was from the link_name attribute or not.
2226 let get_relevant_span =
2227 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2228 SymbolName::Normal(_) => fi.span,
2229 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2231 // Finally, emit the diagnostic.
2232 tcx.struct_span_lint_hir(
2233 CLASHING_EXTERN_DECLARATIONS,
2235 get_relevant_span(this_fi),
2237 let mut expected_str = DiagnosticStyledString::new();
2238 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2239 let mut found_str = DiagnosticStyledString::new();
2240 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2242 lint.build(&format!(
2243 "`{}` redeclare{} with a different signature",
2245 if orig.get_name() == this_fi.ident.name {
2248 format!("s `{}`", orig.get_name())
2252 get_relevant_span(orig_fi),
2253 &format!("`{}` previously declared here", orig.get_name()),
2256 get_relevant_span(this_fi),
2257 "this signature doesn't match the previous declaration",
2259 .note_expected_found(&"", expected_str, &"", found_str)