1 //! Lints in the Rust compiler.
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main compiler.
7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
8 //! Then add code to emit the new lint in the appropriate circumstances.
9 //! You can do that in an existing `LintPass` if it makes sense, or in a
10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
11 //! compiler. Only do the latter if the check can't be written cleanly as a
12 //! `LintPass` (also, note that such lints will need to be defined in
13 //! `rustc_session::lint::builtin`, not here).
15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
18 //! with a `pub fn new()`.
20 //! If you define a new `LateLintPass`, you will also need to add it to the
21 //! `late_lint_methods!` invocation in `lib.rs`.
24 types::CItemKind, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
26 use rustc_ast::attr::{self, HasAttrs};
27 use rustc_ast::tokenstream::{TokenStream, TokenTree};
28 use rustc_ast::visit::{FnCtxt, FnKind};
29 use rustc_ast::{self as ast, *};
30 use rustc_ast_pretty::pprust::{self, expr_to_string};
31 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
32 use rustc_data_structures::stack::ensure_sufficient_stack;
33 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
34 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
35 use rustc_feature::{GateIssue, Stability};
37 use rustc_hir::def::{DefKind, Res};
38 use rustc_hir::def_id::DefId;
39 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
40 use rustc_hir::{HirId, HirIdSet, Node};
41 use rustc_index::vec::Idx;
42 use rustc_middle::lint::LintDiagnosticBuilder;
43 use rustc_middle::ty::print::with_no_trimmed_paths;
44 use rustc_middle::ty::subst::{GenericArgKind, Subst};
45 use rustc_middle::ty::{self, layout::LayoutError, Ty, TyCtxt};
46 use rustc_session::lint::FutureIncompatibleInfo;
47 use rustc_session::Session;
48 use rustc_span::edition::Edition;
49 use rustc_span::source_map::Spanned;
50 use rustc_span::symbol::{kw, sym, Ident, Symbol};
51 use rustc_span::{BytePos, Span};
52 use rustc_target::abi::{LayoutOf, VariantIdx};
53 use rustc_trait_selection::traits::misc::can_type_implement_copy;
55 use crate::nonstandard_style::{method_context, MethodLateContext};
58 use tracing::{debug, trace};
60 // hardwired lints from librustc_middle
61 pub use rustc_session::lint::builtin::*;
66 "suggest using `loop { }` instead of `while true { }`"
69 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
71 /// Traverse through any amount of parenthesis and return the first non-parens expression.
72 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
73 while let ast::ExprKind::Paren(sub) = &expr.kind {
79 impl EarlyLintPass for WhileTrue {
80 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
81 if let ast::ExprKind::While(cond, ..) = &e.kind {
82 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
83 if let ast::LitKind::Bool(true) = lit.kind {
84 if !lit.span.from_expansion() {
85 let msg = "denote infinite loops with `loop { ... }`";
86 let condition_span = cx.sess.source_map().guess_head_span(e.span);
87 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
89 .span_suggestion_short(
93 Applicability::MachineApplicable,
107 "use of owned (Box type) heap memory"
110 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
113 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
114 for leaf in ty.walk() {
115 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
116 if leaf_ty.is_box() {
117 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
118 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
126 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
127 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
129 hir::ItemKind::Fn(..)
130 | hir::ItemKind::TyAlias(..)
131 | hir::ItemKind::Enum(..)
132 | hir::ItemKind::Struct(..)
133 | hir::ItemKind::Union(..) => {
134 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
135 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
140 // If it's a struct, we also have to check the fields' types
142 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
143 for struct_field in struct_def.fields() {
144 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
145 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
152 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
153 let ty = cx.typeck_results().node_type(e.hir_id);
154 self.check_heap_type(cx, e.span, ty);
159 NON_SHORTHAND_FIELD_PATTERNS,
161 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
164 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
166 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
167 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
168 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
173 .expect("struct pattern type is not an ADT")
174 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
175 for fieldpat in field_pats {
176 if fieldpat.is_shorthand {
179 if fieldpat.span.from_expansion() {
180 // Don't lint if this is a macro expansion: macro authors
181 // shouldn't have to worry about this kind of style issue
185 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
186 if cx.tcx.find_field_index(ident, &variant)
187 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
189 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
191 .build(&format!("the `{}:` in this pattern is redundant", ident));
192 let binding = match binding_annot {
193 hir::BindingAnnotation::Unannotated => None,
194 hir::BindingAnnotation::Mutable => Some("mut"),
195 hir::BindingAnnotation::Ref => Some("ref"),
196 hir::BindingAnnotation::RefMut => Some("ref mut"),
198 let ident = if let Some(binding) = binding {
199 format!("{} {}", binding, ident)
205 "use shorthand field pattern",
207 Applicability::MachineApplicable,
221 "usage of `unsafe` code"
224 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
229 cx: &EarlyContext<'_>,
231 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
233 // This comes from a macro that has `#[allow_internal_unsafe]`.
234 if span.allows_unsafe() {
238 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
242 impl EarlyLintPass for UnsafeCode {
243 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
244 if cx.sess().check_name(attr, sym::allow_internal_unsafe) {
245 self.report_unsafe(cx, attr.span, |lint| {
247 "`allow_internal_unsafe` allows defining \
248 macros using unsafe without triggering \
249 the `unsafe_code` lint at their call site",
256 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
257 if let ast::ExprKind::Block(ref blk, _) = e.kind {
258 // Don't warn about generated blocks; that'll just pollute the output.
259 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
260 self.report_unsafe(cx, blk.span, |lint| {
261 lint.build("usage of an `unsafe` block").emit()
267 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
269 ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
270 self.report_unsafe(cx, it.span, |lint| {
271 lint.build("declaration of an `unsafe` trait").emit()
275 ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
276 self.report_unsafe(cx, it.span, |lint| {
277 lint.build("implementation of an `unsafe` trait").emit()
285 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
289 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
294 let msg = match ctxt {
295 FnCtxt::Foreign => return,
296 FnCtxt::Free => "declaration of an `unsafe` function",
297 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
298 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
300 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
308 "detects missing documentation for public members",
309 report_in_external_macro
312 pub struct MissingDoc {
313 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
314 doc_hidden_stack: Vec<bool>,
316 /// Private traits or trait items that leaked through. Don't check their methods.
317 private_traits: FxHashSet<hir::HirId>,
320 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
322 fn has_doc(sess: &Session, attr: &ast::Attribute) -> bool {
323 if attr.is_doc_comment() {
327 if !sess.check_name(attr, sym::doc) {
331 if attr.is_value_str() {
335 if let Some(list) = attr.meta_item_list() {
337 if meta.has_name(sym::include) || meta.has_name(sym::hidden) {
347 pub fn new() -> MissingDoc {
348 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
351 fn doc_hidden(&self) -> bool {
352 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
355 fn check_missing_docs_attrs(
357 cx: &LateContext<'_>,
358 id: Option<hir::HirId>,
359 attrs: &[ast::Attribute],
361 article: &'static str,
364 // If we're building a test harness, then warning about
365 // documentation is probably not really relevant right now.
366 if cx.sess().opts.test {
370 // `#[doc(hidden)]` disables missing_docs check.
371 if self.doc_hidden() {
375 // Only check publicly-visible items, using the result from the privacy pass.
376 // It's an option so the crate root can also use this function (it doesn't
378 if let Some(id) = id {
379 if !cx.access_levels.is_exported(id) {
384 let has_doc = attrs.iter().any(|a| has_doc(cx.sess(), a));
388 cx.tcx.sess.source_map().guess_head_span(sp),
390 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
397 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
398 fn enter_lint_attrs(&mut self, cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
399 let doc_hidden = self.doc_hidden()
400 || attrs.iter().any(|attr| {
401 cx.sess().check_name(attr, sym::doc)
402 && match attr.meta_item_list() {
404 Some(l) => attr::list_contains_name(&l, sym::hidden),
407 self.doc_hidden_stack.push(doc_hidden);
410 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
411 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
414 fn check_crate(&mut self, cx: &LateContext<'_>, krate: &hir::Crate<'_>) {
415 self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "the", "crate");
417 for macro_def in krate.exported_macros {
418 let has_doc = macro_def.attrs.iter().any(|a| has_doc(cx.sess(), a));
422 cx.tcx.sess.source_map().guess_head_span(macro_def.span),
423 |lint| lint.build("missing documentation for macro").emit(),
429 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
431 hir::ItemKind::Trait(.., trait_item_refs) => {
432 // Issue #11592: traits are always considered exported, even when private.
433 if let hir::VisibilityKind::Inherited = it.vis.node {
434 self.private_traits.insert(it.hir_id);
435 for trait_item_ref in trait_item_refs {
436 self.private_traits.insert(trait_item_ref.id.hir_id);
441 hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
442 // If the trait is private, add the impl items to `private_traits` so they don't get
443 // reported for missing docs.
444 let real_trait = trait_ref.path.res.def_id();
445 if let Some(def_id) = real_trait.as_local() {
446 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
447 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
448 if let hir::VisibilityKind::Inherited = item.vis.node {
449 for impl_item_ref in items {
450 self.private_traits.insert(impl_item_ref.id.hir_id);
458 hir::ItemKind::TyAlias(..)
459 | hir::ItemKind::Fn(..)
460 | hir::ItemKind::Mod(..)
461 | hir::ItemKind::Enum(..)
462 | hir::ItemKind::Struct(..)
463 | hir::ItemKind::Union(..)
464 | hir::ItemKind::Const(..)
465 | hir::ItemKind::Static(..) => {}
470 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
471 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
473 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, article, desc);
476 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
477 if self.private_traits.contains(&trait_item.hir_id) {
481 let def_id = cx.tcx.hir().local_def_id(trait_item.hir_id);
482 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
484 self.check_missing_docs_attrs(
486 Some(trait_item.hir_id),
494 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
495 // If the method is an impl for a trait, don't doc.
496 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
500 let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
501 let (article, desc) = cx.tcx.article_and_description(def_id.to_def_id());
502 self.check_missing_docs_attrs(
504 Some(impl_item.hir_id),
512 fn check_struct_field(&mut self, cx: &LateContext<'_>, sf: &hir::StructField<'_>) {
513 if !sf.is_positional() {
514 self.check_missing_docs_attrs(
525 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
526 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a", "variant");
531 pub MISSING_COPY_IMPLEMENTATIONS,
533 "detects potentially-forgotten implementations of `Copy`"
536 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
538 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
539 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
540 if !cx.access_levels.is_reachable(item.hir_id) {
543 let (def, ty) = match item.kind {
544 hir::ItemKind::Struct(_, ref ast_generics) => {
545 if !ast_generics.params.is_empty() {
548 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
549 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
551 hir::ItemKind::Union(_, ref ast_generics) => {
552 if !ast_generics.params.is_empty() {
555 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
556 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
558 hir::ItemKind::Enum(_, ref ast_generics) => {
559 if !ast_generics.params.is_empty() {
562 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
563 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
567 if def.has_dtor(cx.tcx) {
570 let param_env = ty::ParamEnv::empty();
571 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
574 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
575 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
577 "type could implement `Copy`; consider adding `impl \
587 MISSING_DEBUG_IMPLEMENTATIONS,
589 "detects missing implementations of Debug"
593 pub struct MissingDebugImplementations {
594 impling_types: Option<HirIdSet>,
597 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
599 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
600 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
601 if !cx.access_levels.is_reachable(item.hir_id) {
606 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
610 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
611 Some(debug) => debug,
615 if self.impling_types.is_none() {
616 let mut impls = HirIdSet::default();
617 cx.tcx.for_each_impl(debug, |d| {
618 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
619 if let Some(def_id) = ty_def.did.as_local() {
620 impls.insert(cx.tcx.hir().local_def_id_to_hir_id(def_id));
625 self.impling_types = Some(impls);
626 debug!("{:?}", self.impling_types);
629 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
630 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
632 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
633 or a manual implementation",
634 cx.tcx.def_path_str(debug)
643 pub ANONYMOUS_PARAMETERS,
645 "detects anonymous parameters",
646 @future_incompatible = FutureIncompatibleInfo {
647 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
648 edition: Some(Edition::Edition2018),
653 /// Checks for use of anonymous parameters (RFC 1685).
654 AnonymousParameters => [ANONYMOUS_PARAMETERS]
657 impl EarlyLintPass for AnonymousParameters {
658 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
659 if let ast::AssocItemKind::Fn(_, ref sig, _, _) = it.kind {
660 for arg in sig.decl.inputs.iter() {
661 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
662 if ident.name == kw::Invalid {
663 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
664 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
666 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
667 (snip.as_str(), Applicability::MachineApplicable)
669 ("<type>", Applicability::HasPlaceholders)
673 "anonymous parameters are deprecated and will be \
674 removed in the next edition.",
678 "try naming the parameter or explicitly \
680 format!("_: {}", ty_snip),
692 /// Check for use of attributes which have been deprecated.
694 pub struct DeprecatedAttr {
695 // This is not free to compute, so we want to keep it around, rather than
696 // compute it for every attribute.
697 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
700 impl_lint_pass!(DeprecatedAttr => []);
702 impl DeprecatedAttr {
703 pub fn new() -> DeprecatedAttr {
704 DeprecatedAttr { depr_attrs: deprecated_attributes() }
708 fn lint_deprecated_attr(
709 cx: &EarlyContext<'_>,
710 attr: &ast::Attribute,
712 suggestion: Option<&str>,
714 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
716 .span_suggestion_short(
718 suggestion.unwrap_or("remove this attribute"),
720 Applicability::MachineApplicable,
726 impl EarlyLintPass for DeprecatedAttr {
727 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
728 for &&(n, _, _, ref g) in &self.depr_attrs {
729 if attr.ident().map(|ident| ident.name) == Some(n) {
730 if let &AttributeGate::Gated(
731 Stability::Deprecated(link, suggestion),
738 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
739 lint_deprecated_attr(cx, attr, &msg, suggestion);
744 if cx.sess().check_name(attr, sym::no_start) || cx.sess().check_name(attr, sym::crate_id) {
745 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
746 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
747 lint_deprecated_attr(cx, attr, &msg, None);
752 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
753 let mut attrs = attrs.iter().peekable();
755 // Accumulate a single span for sugared doc comments.
756 let mut sugared_span: Option<Span> = None;
758 while let Some(attr) = attrs.next() {
759 if attr.is_doc_comment() {
761 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
764 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
768 let span = sugared_span.take().unwrap_or_else(|| attr.span);
770 if attr.is_doc_comment() || cx.sess().check_name(attr, sym::doc) {
771 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
772 let mut err = lint.build("unused doc comment");
775 format!("rustdoc does not generate documentation for {}", node_kind),
783 impl EarlyLintPass for UnusedDocComment {
784 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
785 let kind = match stmt.kind {
786 ast::StmtKind::Local(..) => "statements",
787 ast::StmtKind::Item(..) => "inner items",
788 // expressions will be reported by `check_expr`.
790 | ast::StmtKind::Semi(_)
791 | ast::StmtKind::Expr(_)
792 | ast::StmtKind::MacCall(_) => return,
795 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
798 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
799 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
800 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
803 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
804 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
809 NO_MANGLE_CONST_ITEMS,
811 "const items will not have their symbols exported"
815 NO_MANGLE_GENERIC_ITEMS,
817 "generic items must be mangled"
820 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
822 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
823 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
825 hir::ItemKind::Fn(.., ref generics, _) => {
826 if let Some(no_mangle_attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
827 for param in generics.params {
829 GenericParamKind::Lifetime { .. } => {}
830 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
831 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
833 "functions generic over types or consts must be mangled",
835 .span_suggestion_short(
837 "remove this attribute",
839 // Use of `#[no_mangle]` suggests FFI intent; correct
840 // fix may be to monomorphize source by hand
841 Applicability::MaybeIncorrect,
851 hir::ItemKind::Const(..) => {
852 if cx.sess().contains_name(&it.attrs, sym::no_mangle) {
853 // Const items do not refer to a particular location in memory, and therefore
854 // don't have anything to attach a symbol to
855 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
856 let msg = "const items should never be `#[no_mangle]`";
857 let mut err = lint.build(msg);
859 // account for "pub const" (#45562)
864 .span_to_snippet(it.span)
865 .map(|snippet| snippet.find("const").unwrap_or(0))
866 .unwrap_or(0) as u32;
867 // `const` is 5 chars
868 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
871 "try a static value",
872 "pub static".to_owned(),
873 Applicability::MachineApplicable,
887 "mutating transmuted &mut T from &T may cause undefined behavior"
890 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
892 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
893 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
894 use rustc_target::spec::abi::Abi::RustIntrinsic;
895 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
896 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
898 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
899 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
900 consider instead using an UnsafeCell";
901 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
905 fn get_transmute_from_to<'tcx>(
906 cx: &LateContext<'tcx>,
907 expr: &hir::Expr<'_>,
908 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
909 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
910 cx.qpath_res(qpath, expr.hir_id)
914 if let Res::Def(DefKind::Fn, did) = def {
915 if !def_id_is_transmute(cx, did) {
918 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
919 let from = sig.inputs().skip_binder()[0];
920 let to = sig.output().skip_binder();
921 return Some((from, to));
926 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
927 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
928 && cx.tcx.item_name(def_id) == sym::transmute
936 "enabling unstable features (deprecated. do not use)"
940 /// Forbids using the `#[feature(...)]` attribute
941 UnstableFeatures => [UNSTABLE_FEATURES]
944 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
945 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
946 if cx.sess().check_name(attr, sym::feature) {
947 if let Some(items) = attr.meta_item_list() {
949 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
950 lint.build("unstable feature").emit()
961 "`pub` items not reachable from crate root"
965 /// Lint for items marked `pub` that aren't reachable from other crates.
966 UnreachablePub => [UNREACHABLE_PUB]
969 impl UnreachablePub {
972 cx: &LateContext<'_>,
975 vis: &hir::Visibility<'_>,
979 let mut applicability = Applicability::MachineApplicable;
981 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
982 if span.from_expansion() {
983 applicability = Applicability::MaybeIncorrect;
985 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
986 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
987 let mut err = lint.build(&format!("unreachable `pub` {}", what));
988 let replacement = if cx.tcx.features().crate_visibility_modifier {
997 "consider restricting its visibility",
1002 err.help("or consider exporting it for use by other crates");
1012 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1013 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1014 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1017 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1021 foreign_item.hir_id,
1028 fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
1029 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1032 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1033 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1040 "bounds in type aliases are not enforced"
1044 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1045 /// They are relevant when using associated types, but otherwise neither checked
1046 /// at definition site nor enforced at use site.
1047 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1050 impl TypeAliasBounds {
1051 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1053 hir::QPath::TypeRelative(ref ty, _) => {
1054 // If this is a type variable, we found a `T::Assoc`.
1056 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1057 Res::Def(DefKind::TyParam, _) => true,
1063 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1067 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1068 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1069 // bound. Let's see if this type does that.
1071 // We use a HIR visitor to walk the type.
1072 use rustc_hir::intravisit::{self, Visitor};
1073 struct WalkAssocTypes<'a, 'db> {
1074 err: &'a mut DiagnosticBuilder<'db>,
1076 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1077 type Map = intravisit::ErasedMap<'v>;
1079 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1080 intravisit::NestedVisitorMap::None
1083 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1084 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1087 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1088 associated types in type aliases",
1091 intravisit::walk_qpath(self, qpath, id, span)
1095 // Let's go for a walk!
1096 let mut visitor = WalkAssocTypes { err };
1097 visitor.visit_ty(ty);
1101 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1102 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1103 let (ty, type_alias_generics) = match item.kind {
1104 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1107 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1108 // Bounds are respected for `type X = impl Trait`
1111 let mut suggested_changing_assoc_types = false;
1112 // There must not be a where clause
1113 if !type_alias_generics.where_clause.predicates.is_empty() {
1117 let mut err = lint.build("where clauses are not enforced in type aliases");
1118 let spans: Vec<_> = type_alias_generics
1122 .map(|pred| pred.span())
1124 err.set_span(spans);
1125 err.span_suggestion(
1126 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1127 "the clause will not be checked when the type alias is used, and should be removed",
1129 Applicability::MachineApplicable,
1131 if !suggested_changing_assoc_types {
1132 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1133 suggested_changing_assoc_types = true;
1139 // The parameters must not have bounds
1140 for param in type_alias_generics.params.iter() {
1141 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1142 let suggestion = spans
1145 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1146 (start.to(*sp), String::new())
1149 if !spans.is_empty() {
1150 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1152 lint.build("bounds on generic parameters are not enforced in type aliases");
1153 let msg = "the bound will not be checked when the type alias is used, \
1154 and should be removed";
1155 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1156 if !suggested_changing_assoc_types {
1157 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1158 suggested_changing_assoc_types = true;
1168 /// Lint constants that are erroneous.
1169 /// Without this lint, we might not get any diagnostic if the constant is
1170 /// unused within this crate, even though downstream crates can't use it
1171 /// without producing an error.
1172 UnusedBrokenConst => []
1175 fn check_const(cx: &LateContext<'_>, body_id: hir::BodyId) {
1176 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1177 // trigger the query once for all constants since that will already report the errors
1178 // FIXME: Use ensure here
1179 let _ = cx.tcx.const_eval_poly(def_id);
1182 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1183 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1185 hir::ItemKind::Const(_, body_id) => {
1186 check_const(cx, body_id);
1188 hir::ItemKind::Static(_, _, body_id) => {
1189 check_const(cx, body_id);
1199 "these bounds don't depend on an type parameters"
1203 /// Lint for trait and lifetime bounds that don't depend on type parameters
1204 /// which either do nothing, or stop the item from being used.
1205 TrivialConstraints => [TRIVIAL_BOUNDS]
1208 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1209 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1210 use rustc_middle::ty::fold::TypeFoldable;
1211 use rustc_middle::ty::PredicateAtom::*;
1213 if cx.tcx.features().trivial_bounds {
1214 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1215 let predicates = cx.tcx.predicates_of(def_id);
1216 for &(predicate, span) in predicates.predicates {
1217 let predicate_kind_name = match predicate.skip_binders() {
1218 Trait(..) => "Trait",
1220 RegionOutlives(..) => "Lifetime",
1222 // Ignore projections, as they can only be global
1223 // if the trait bound is global
1225 // Ignore bounds that a user can't type
1230 ConstEvaluatable(..) |
1232 TypeWellFormedFromEnv(..) => continue,
1234 if predicate.is_global() {
1235 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1236 lint.build(&format!(
1237 "{} bound {} does not depend on any type \
1238 or lifetime parameters",
1239 predicate_kind_name, predicate
1250 /// Does nothing as a lint pass, but registers some `Lint`s
1251 /// which are used by other parts of the compiler.
1255 NON_SHORTHAND_FIELD_PATTERNS,
1258 MISSING_COPY_IMPLEMENTATIONS,
1259 MISSING_DEBUG_IMPLEMENTATIONS,
1260 ANONYMOUS_PARAMETERS,
1261 UNUSED_DOC_COMMENTS,
1262 NO_MANGLE_CONST_ITEMS,
1263 NO_MANGLE_GENERIC_ITEMS,
1273 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1275 "`...` range patterns are deprecated"
1279 pub struct EllipsisInclusiveRangePatterns {
1280 /// If `Some(_)`, suppress all subsequent pattern
1281 /// warnings for better diagnostics.
1282 node_id: Option<ast::NodeId>,
1285 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1287 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1288 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1289 if self.node_id.is_some() {
1290 // Don't recursively warn about patterns inside range endpoints.
1294 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1296 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1297 /// corresponding to the ellipsis.
1298 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1303 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1304 ) => Some((a.as_deref(), b, *span)),
1309 let (parenthesise, endpoints) = match &pat.kind {
1310 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1311 _ => (false, matches_ellipsis_pat(pat)),
1314 if let Some((start, end, join)) = endpoints {
1315 let msg = "`...` range patterns are deprecated";
1316 let suggestion = "use `..=` for an inclusive range";
1318 self.node_id = Some(pat.id);
1319 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1320 let end = expr_to_string(&end);
1321 let replace = match start {
1322 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1323 None => format!("&(..={})", end),
1330 Applicability::MachineApplicable,
1335 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1337 .span_suggestion_short(
1341 Applicability::MachineApplicable,
1349 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1350 if let Some(node_id) = self.node_id {
1351 if pat.id == node_id {
1359 UNNAMEABLE_TEST_ITEMS,
1361 "detects an item that cannot be named being marked as `#[test_case]`",
1362 report_in_external_macro
1365 pub struct UnnameableTestItems {
1366 boundary: Option<hir::HirId>, // HirId of the item under which things are not nameable
1367 items_nameable: bool,
1370 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1372 impl UnnameableTestItems {
1373 pub fn new() -> Self {
1374 Self { boundary: None, items_nameable: true }
1378 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1379 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1380 if self.items_nameable {
1381 if let hir::ItemKind::Mod(..) = it.kind {
1383 self.items_nameable = false;
1384 self.boundary = Some(it.hir_id);
1389 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::rustc_test_marker) {
1390 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1391 lint.build("cannot test inner items").emit()
1396 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1397 if !self.items_nameable && self.boundary == Some(it.hir_id) {
1398 self.items_nameable = true;
1406 "detects edition keywords being used as an identifier",
1407 @future_incompatible = FutureIncompatibleInfo {
1408 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1409 edition: Some(Edition::Edition2018),
1414 /// Check for uses of edition keywords used as an identifier.
1415 KeywordIdents => [KEYWORD_IDENTS]
1418 struct UnderMacro(bool);
1420 impl KeywordIdents {
1421 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1422 for tt in tokens.into_trees() {
1424 // Only report non-raw idents.
1425 TokenTree::Token(token) => {
1426 if let Some((ident, false)) = token.ident() {
1427 self.check_ident_token(cx, UnderMacro(true), ident);
1430 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1435 fn check_ident_token(
1437 cx: &EarlyContext<'_>,
1438 UnderMacro(under_macro): UnderMacro,
1441 let next_edition = match cx.sess.edition() {
1442 Edition::Edition2015 => {
1444 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1446 // rust-lang/rust#56327: Conservatively do not
1447 // attempt to report occurrences of `dyn` within
1448 // macro definitions or invocations, because `dyn`
1449 // can legitimately occur as a contextual keyword
1450 // in 2015 code denoting its 2018 meaning, and we
1451 // do not want rustfix to inject bugs into working
1452 // code by rewriting such occurrences.
1454 // But if we see `dyn` outside of a macro, we know
1455 // its precise role in the parsed AST and thus are
1456 // assured this is truly an attempt to use it as
1458 kw::Dyn if !under_macro => Edition::Edition2018,
1464 // There are no new keywords yet for the 2018 edition and beyond.
1468 // Don't lint `r#foo`.
1469 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1473 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1474 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1477 "you can use a raw identifier to stay compatible",
1478 format!("r#{}", ident),
1479 Applicability::MachineApplicable,
1486 impl EarlyLintPass for KeywordIdents {
1487 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1488 self.check_tokens(cx, mac_def.body.inner_tokens());
1490 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1491 self.check_tokens(cx, mac.args.inner_tokens());
1493 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1494 self.check_ident_token(cx, UnderMacro(false), ident);
1498 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1500 impl ExplicitOutlivesRequirements {
1501 fn lifetimes_outliving_lifetime<'tcx>(
1502 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1504 ) -> Vec<ty::Region<'tcx>> {
1507 .filter_map(|(pred, _)| match pred.skip_binders() {
1508 ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
1509 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
1517 fn lifetimes_outliving_type<'tcx>(
1518 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1520 ) -> Vec<ty::Region<'tcx>> {
1523 .filter_map(|(pred, _)| match pred.skip_binders() {
1524 ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
1525 a.is_param(index).then_some(b)
1532 fn collect_outlived_lifetimes<'tcx>(
1534 param: &'tcx hir::GenericParam<'tcx>,
1536 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1537 ty_generics: &'tcx ty::Generics,
1538 ) -> Vec<ty::Region<'tcx>> {
1540 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
1543 hir::GenericParamKind::Lifetime { .. } => {
1544 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1546 hir::GenericParamKind::Type { .. } => {
1547 Self::lifetimes_outliving_type(inferred_outlives, index)
1549 hir::GenericParamKind::Const { .. } => Vec::new(),
1553 fn collect_outlives_bound_spans<'tcx>(
1556 bounds: &hir::GenericBounds<'_>,
1557 inferred_outlives: &[ty::Region<'tcx>],
1559 ) -> Vec<(usize, Span)> {
1560 use rustc_middle::middle::resolve_lifetime::Region;
1565 .filter_map(|(i, bound)| {
1566 if let hir::GenericBound::Outlives(lifetime) = bound {
1567 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1568 Some(Region::Static) if infer_static => inferred_outlives
1570 .any(|r| if let ty::ReStatic = r { true } else { false }),
1571 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1572 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1576 is_inferred.then_some((i, bound.span()))
1584 fn consolidate_outlives_bound_spans(
1587 bounds: &hir::GenericBounds<'_>,
1588 bound_spans: Vec<(usize, Span)>,
1590 if bounds.is_empty() {
1593 if bound_spans.len() == bounds.len() {
1594 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1595 // If all bounds are inferable, we want to delete the colon, so
1596 // start from just after the parameter (span passed as argument)
1597 vec![lo.to(last_bound_span)]
1599 let mut merged = Vec::new();
1600 let mut last_merged_i = None;
1602 let mut from_start = true;
1603 for (i, bound_span) in bound_spans {
1604 match last_merged_i {
1605 // If the first bound is inferable, our span should also eat the leading `+`.
1607 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1608 last_merged_i = Some(0);
1610 // If consecutive bounds are inferable, merge their spans
1611 Some(h) if i == h + 1 => {
1612 if let Some(tail) = merged.last_mut() {
1613 // Also eat the trailing `+` if the first
1614 // more-than-one bound is inferable
1615 let to_span = if from_start && i < bounds.len() {
1616 bounds[i + 1].span().shrink_to_lo()
1620 *tail = tail.to(to_span);
1621 last_merged_i = Some(i);
1623 bug!("another bound-span visited earlier");
1627 // When we find a non-inferable bound, subsequent inferable bounds
1628 // won't be consecutive from the start (and we'll eat the leading
1629 // `+` rather than the trailing one)
1631 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1632 last_merged_i = Some(i);
1641 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
1642 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
1643 use rustc_middle::middle::resolve_lifetime::Region;
1645 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1646 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1647 if let hir::ItemKind::Struct(_, ref hir_generics)
1648 | hir::ItemKind::Enum(_, ref hir_generics)
1649 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1651 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1652 if inferred_outlives.is_empty() {
1656 let ty_generics = cx.tcx.generics_of(def_id);
1658 let mut bound_count = 0;
1659 let mut lint_spans = Vec::new();
1661 for param in hir_generics.params {
1662 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1663 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1665 if !has_lifetime_bounds {
1669 let relevant_lifetimes =
1670 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1671 if relevant_lifetimes.is_empty() {
1675 let bound_spans = self.collect_outlives_bound_spans(
1678 &relevant_lifetimes,
1681 bound_count += bound_spans.len();
1682 lint_spans.extend(self.consolidate_outlives_bound_spans(
1683 param.span.shrink_to_hi(),
1689 let mut where_lint_spans = Vec::new();
1690 let mut dropped_predicate_count = 0;
1691 let num_predicates = hir_generics.where_clause.predicates.len();
1692 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1693 let (relevant_lifetimes, bounds, span) = match where_predicate {
1694 hir::WherePredicate::RegionPredicate(predicate) => {
1695 if let Some(Region::EarlyBound(index, ..)) =
1696 cx.tcx.named_region(predicate.lifetime.hir_id)
1699 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1707 hir::WherePredicate::BoundPredicate(predicate) => {
1708 // FIXME we can also infer bounds on associated types,
1709 // and should check for them here.
1710 match predicate.bounded_ty.kind {
1711 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1712 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1713 let index = ty_generics.param_def_id_to_index[&def_id];
1715 Self::lifetimes_outliving_type(inferred_outlives, index),
1730 if relevant_lifetimes.is_empty() {
1734 let bound_spans = self.collect_outlives_bound_spans(
1737 &relevant_lifetimes,
1740 bound_count += bound_spans.len();
1742 let drop_predicate = bound_spans.len() == bounds.len();
1744 dropped_predicate_count += 1;
1747 // If all the bounds on a predicate were inferable and there are
1748 // further predicates, we want to eat the trailing comma.
1749 if drop_predicate && i + 1 < num_predicates {
1750 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1751 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1753 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1754 span.shrink_to_lo(),
1761 // If all predicates are inferable, drop the entire clause
1762 // (including the `where`)
1763 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1764 let where_span = hir_generics
1767 .expect("span of (nonempty) where clause should exist");
1768 // Extend the where clause back to the closing `>` of the
1769 // generics, except for tuple struct, which have the `where`
1770 // after the fields of the struct.
1771 let full_where_span =
1772 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1775 hir_generics.span.shrink_to_hi().to(where_span)
1777 lint_spans.push(full_where_span);
1779 lint_spans.extend(where_lint_spans);
1782 if !lint_spans.is_empty() {
1783 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1784 lint.build("outlives requirements can be inferred")
1785 .multipart_suggestion(
1786 if bound_count == 1 {
1789 "remove these bounds"
1793 .map(|span| (span, "".to_owned()))
1794 .collect::<Vec<_>>(),
1795 Applicability::MachineApplicable,
1805 pub INCOMPLETE_FEATURES,
1807 "incomplete features that may function improperly in some or all cases"
1811 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1812 IncompleteFeatures => [INCOMPLETE_FEATURES]
1815 impl EarlyLintPass for IncompleteFeatures {
1816 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1817 let features = cx.sess.features_untracked();
1819 .declared_lang_features
1821 .map(|(name, span, _)| (name, span))
1822 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1823 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1824 .for_each(|(&name, &span)| {
1825 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1826 let mut builder = lint.build(&format!(
1827 "the feature `{}` is incomplete and may not be safe to use \
1828 and/or cause compiler crashes",
1831 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
1832 builder.note(&format!(
1833 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
1834 for more information",
1847 "an invalid value is being created (such as a NULL reference)"
1850 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1852 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
1853 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
1854 #[derive(Debug, Copy, Clone, PartialEq)]
1860 /// Information about why a type cannot be initialized this way.
1861 /// Contains an error message and optionally a span to point at.
1862 type InitError = (String, Option<Span>);
1864 /// Test if this constant is all-0.
1865 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1866 use hir::ExprKind::*;
1867 use rustc_ast::LitKind::*;
1870 if let Int(i, _) = lit.node {
1876 Tup(tup) => tup.iter().all(is_zero),
1881 /// Determine if this expression is a "dangerous initialization".
1882 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1883 // `transmute` is inside an anonymous module (the `extern` block?);
1884 // `Invalid` represents the empty string and matches that.
1885 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1886 // on intrinsics right now.
1887 const TRANSMUTE_PATH: &[Symbol] =
1888 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1890 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1891 // Find calls to `mem::{uninitialized,zeroed}` methods.
1892 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1893 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1895 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1896 return Some(InitKind::Zeroed);
1897 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1898 return Some(InitKind::Uninit);
1899 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1900 if is_zero(&args[0]) {
1901 return Some(InitKind::Zeroed);
1905 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
1906 // Find problematic calls to `MaybeUninit::assume_init`.
1907 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
1908 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1909 // This is a call to *some* method named `assume_init`.
1910 // See if the `self` parameter is one of the dangerous constructors.
1911 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1912 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1913 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1915 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1916 return Some(InitKind::Zeroed);
1917 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1918 return Some(InitKind::Uninit);
1928 /// Test if this enum has several actually "existing" variants.
1929 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
1930 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
1931 // As an approximation, we only count dataless variants. Those are definitely inhabited.
1932 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
1933 existing_variants > 1
1936 /// Return `Some` only if we are sure this type does *not*
1937 /// allow zero initialization.
1938 fn ty_find_init_error<'tcx>(
1942 ) -> Option<InitError> {
1943 use rustc_middle::ty::TyKind::*;
1945 // Primitive types that don't like 0 as a value.
1946 Ref(..) => Some(("references must be non-null".to_string(), None)),
1947 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1948 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1949 Never => Some(("the `!` type has no valid value".to_string(), None)),
1950 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
1951 // raw ptr to dyn Trait
1953 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1955 // Primitive types with other constraints.
1956 Bool if init == InitKind::Uninit => {
1957 Some(("booleans must be either `true` or `false`".to_string(), None))
1959 Char if init == InitKind::Uninit => {
1960 Some(("characters must be a valid Unicode codepoint".to_string(), None))
1962 // Recurse and checks for some compound types.
1963 Adt(adt_def, substs) if !adt_def.is_union() => {
1964 // First check if this ADT has a layout attribute (like `NonNull` and friends).
1965 use std::ops::Bound;
1966 match tcx.layout_scalar_valid_range(adt_def.did) {
1967 // We exploit here that `layout_scalar_valid_range` will never
1968 // return `Bound::Excluded`. (And we have tests checking that we
1969 // handle the attribute correctly.)
1970 (Bound::Included(lo), _) if lo > 0 => {
1971 return Some((format!("`{}` must be non-null", ty), None));
1973 (Bound::Included(_), _) | (_, Bound::Included(_))
1974 if init == InitKind::Uninit =>
1978 "`{}` must be initialized inside its custom valid range",
1987 match adt_def.variants.len() {
1988 0 => Some(("enums with no variants have no valid value".to_string(), None)),
1990 // Struct, or enum with exactly one variant.
1991 // Proceed recursively, check all fields.
1992 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1993 variant.fields.iter().find_map(|field| {
1994 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1997 // Point to this field, should be helpful for figuring
1998 // out where the source of the error is.
1999 let span = tcx.def_span(field.did);
2002 " (in this {} field)",
2015 // Multi-variant enum.
2017 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2018 let span = tcx.def_span(adt_def.did);
2020 "enums have to be initialized to a variant".to_string(),
2024 // In principle, for zero-initialization we could figure out which variant corresponds
2025 // to tag 0, and check that... but for now we just accept all zero-initializations.
2032 // Proceed recursively, check all fields.
2033 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2035 // Conservative fallback.
2040 if let Some(init) = is_dangerous_init(cx, expr) {
2041 // This conjures an instance of a type out of nothing,
2042 // using zeroed or uninitialized memory.
2043 // We are extremely conservative with what we warn about.
2044 let conjured_ty = cx.typeck_results().expr_ty(expr);
2045 if let Some((msg, span)) =
2046 with_no_trimmed_paths(|| ty_find_init_error(cx.tcx, conjured_ty, init))
2048 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2049 let mut err = lint.build(&format!(
2050 "the type `{}` does not permit {}",
2053 InitKind::Zeroed => "zero-initialization",
2054 InitKind::Uninit => "being left uninitialized",
2057 err.span_label(expr.span, "this code causes undefined behavior when executed");
2060 "help: use `MaybeUninit<T>` instead, \
2061 and only call `assume_init` after initialization is done",
2063 if let Some(span) = span {
2064 err.span_note(span, &msg);
2076 pub CLASHING_EXTERN_DECLARATIONS,
2078 "detects when an extern fn has been declared with the same name but different types"
2081 pub struct ClashingExternDeclarations {
2082 seen_decls: FxHashMap<Symbol, HirId>,
2085 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2086 /// just from declaration itself. This is important because we don't want to report clashes on
2087 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2090 /// The name of the symbol + the span of the annotation which introduced the link name.
2092 /// No link name, so just the name of the symbol.
2097 fn get_name(&self) -> Symbol {
2099 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2104 impl ClashingExternDeclarations {
2105 crate fn new() -> Self {
2106 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2108 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2109 /// for the item, return its HirId without updating the set.
2110 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2111 let hid = fi.hir_id;
2114 &tcx.codegen_fn_attrs(tcx.hir().local_def_id(hid)).link_name.unwrap_or(fi.ident.name);
2116 if self.seen_decls.contains_key(name) {
2117 // Avoid updating the map with the new entry when we do find a collision. We want to
2118 // make sure we're always pointing to the first definition as the previous declaration.
2119 // This lets us avoid emitting "knock-on" diagnostics.
2120 Some(*self.seen_decls.get(name).unwrap())
2122 self.seen_decls.insert(*name, hid)
2126 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2127 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2129 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2130 let did = tcx.hir().local_def_id(fi.hir_id);
2131 if let Some((overridden_link_name, overridden_link_name_span)) =
2132 tcx.codegen_fn_attrs(did).link_name.map(|overridden_link_name| {
2133 // FIXME: Instead of searching through the attributes again to get span
2134 // information, we could have codegen_fn_attrs also give span information back for
2135 // where the attribute was defined. However, until this is found to be a
2136 // bottleneck, this does just fine.
2138 overridden_link_name,
2139 tcx.get_attrs(did.to_def_id())
2141 .find(|at| tcx.sess.check_name(at, sym::link_name))
2147 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2149 SymbolName::Normal(fi.ident.name)
2153 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2154 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2155 /// with the same members (as the declarations shouldn't clash).
2156 fn structurally_same_type<'tcx>(
2157 cx: &LateContext<'tcx>,
2162 fn structurally_same_type_impl<'tcx>(
2163 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2164 cx: &LateContext<'tcx>,
2169 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2172 // Given a transparent newtype, reach through and grab the inner
2173 // type unless the newtype makes the type non-null.
2174 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2177 if let ty::Adt(def, substs) = *ty.kind() {
2178 let is_transparent = def.subst(tcx, substs).repr.transparent();
2179 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, &def);
2181 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2182 ty, is_transparent, is_non_null
2184 if is_transparent && !is_non_null {
2185 debug_assert!(def.variants.len() == 1);
2186 let v = &def.variants[VariantIdx::new(0)];
2188 .transparent_newtype_field(tcx)
2190 "single-variant transparent structure with zero-sized field",
2196 debug!("non_transparent_ty -> {:?}", ty);
2201 let a = non_transparent_ty(a);
2202 let b = non_transparent_ty(b);
2204 if !seen_types.insert((a, b)) {
2205 // We've encountered a cycle. There's no point going any further -- the types are
2206 // structurally the same.
2210 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2211 // All nominally-same types are structurally same, too.
2214 // Do a full, depth-first comparison between the two.
2215 use rustc_middle::ty::TyKind::*;
2216 let a_kind = a.kind();
2217 let b_kind = b.kind();
2219 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2220 debug!("compare_layouts({:?}, {:?})", a, b);
2221 let a_layout = &cx.layout_of(a)?.layout.abi;
2222 let b_layout = &cx.layout_of(b)?.layout.abi;
2224 "comparing layouts: {:?} == {:?} = {}",
2227 a_layout == b_layout
2229 Ok(a_layout == b_layout)
2232 #[allow(rustc::usage_of_ty_tykind)]
2233 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2234 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2237 ensure_sufficient_stack(|| {
2238 match (a_kind, b_kind) {
2239 (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2240 let a = a.subst(cx.tcx, a_substs);
2241 let b = b.subst(cx.tcx, b_substs);
2242 debug!("Comparing {:?} and {:?}", a, b);
2244 // We can immediately rule out these types as structurally same if
2245 // their layouts differ.
2246 match compare_layouts(a, b) {
2247 Ok(false) => return false,
2248 _ => (), // otherwise, continue onto the full, fields comparison
2251 // Grab a flattened representation of all fields.
2252 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2253 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2255 // Perform a structural comparison for each field.
2258 |&ty::FieldDef { did: a_did, .. },
2259 &ty::FieldDef { did: b_did, .. }| {
2260 structurally_same_type_impl(
2270 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2271 // For arrays, we also check the constness of the type.
2272 a_const.val == b_const.val
2273 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2275 (Slice(a_ty), Slice(b_ty)) => {
2276 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2278 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2279 a_tymut.mutbl == b_tymut.mutbl
2280 && structurally_same_type_impl(
2288 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2289 // For structural sameness, we don't need the region to be same.
2291 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2293 (FnDef(..), FnDef(..)) => {
2294 let a_poly_sig = a.fn_sig(tcx);
2295 let b_poly_sig = b.fn_sig(tcx);
2297 // As we don't compare regions, skip_binder is fine.
2298 let a_sig = a_poly_sig.skip_binder();
2299 let b_sig = b_poly_sig.skip_binder();
2301 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2302 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2303 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2304 structurally_same_type_impl(seen_types, cx, a, b, ckind)
2306 && structurally_same_type_impl(
2314 (Tuple(a_substs), Tuple(b_substs)) => {
2315 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2316 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2319 // For these, it's not quite as easy to define structural-sameness quite so easily.
2320 // For the purposes of this lint, take the conservative approach and mark them as
2321 // not structurally same.
2322 (Dynamic(..), Dynamic(..))
2323 | (Error(..), Error(..))
2324 | (Closure(..), Closure(..))
2325 | (Generator(..), Generator(..))
2326 | (GeneratorWitness(..), GeneratorWitness(..))
2327 | (Projection(..), Projection(..))
2328 | (Opaque(..), Opaque(..)) => false,
2330 // These definitely should have been caught above.
2331 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2333 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2334 // enum layout optimisation is being applied.
2335 (Adt(..), other_kind) | (other_kind, Adt(..))
2336 if is_primitive_or_pointer(other_kind) =>
2338 let (primitive, adt) =
2339 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2340 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2343 compare_layouts(a, b).unwrap_or(false)
2346 // Otherwise, just compare the layouts. This may fail to lint for some
2347 // incompatible types, but at the very least, will stop reads into
2348 // uninitialised memory.
2349 _ => compare_layouts(a, b).unwrap_or(false),
2354 let mut seen_types = FxHashSet::default();
2355 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2359 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2361 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2362 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2363 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2364 if let ForeignItemKind::Fn(..) = this_fi.kind {
2366 if let Some(existing_hid) = self.insert(tcx, this_fi) {
2367 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
2368 let this_decl_ty = tcx.type_of(tcx.hir().local_def_id(this_fi.hir_id));
2370 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2371 existing_hid, existing_decl_ty, this_fi.hir_id, this_decl_ty
2373 // Check that the declarations match.
2374 if !Self::structurally_same_type(
2378 CItemKind::Declaration,
2380 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
2381 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2383 // We want to ensure that we use spans for both decls that include where the
2384 // name was defined, whether that was from the link_name attribute or not.
2385 let get_relevant_span =
2386 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2387 SymbolName::Normal(_) => fi.span,
2388 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2390 // Finally, emit the diagnostic.
2391 tcx.struct_span_lint_hir(
2392 CLASHING_EXTERN_DECLARATIONS,
2394 get_relevant_span(this_fi),
2396 let mut expected_str = DiagnosticStyledString::new();
2397 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
2398 let mut found_str = DiagnosticStyledString::new();
2399 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
2401 lint.build(&format!(
2402 "`{}` redeclare{} with a different signature",
2404 if orig.get_name() == this_fi.ident.name {
2407 format!("s `{}`", orig.get_name())
2411 get_relevant_span(orig_fi),
2412 &format!("`{}` previously declared here", orig.get_name()),
2415 get_relevant_span(this_fi),
2416 "this signature doesn't match the previous declaration",
2418 .note_expected_found(&"", expected_str, &"", found_str)