1 //! Lints in the Rust compiler.
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main
8 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
9 //! Then add code to emit the new lint in the appropriate circumstances.
10 //! You can do that in an existing `LintPass` if it makes sense, or in a
11 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
12 //! compiler. Only do the latter if the check can't be written cleanly as a
13 //! `LintPass` (also, note that such lints will need to be defined in
14 //! `rustc::lint::builtin`, not here).
16 //! If you define a new `EarlyLintPass`, you will also need to add it to the
17 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
18 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
19 //! with a `pub fn new()`.
21 //! If you define a new `LateLintPass`, you will also need to add it to the
22 //! `late_lint_methods!` invocation in `lib.rs`.
24 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
25 use rustc::hir::map::Map;
26 use rustc::lint::LintDiagnosticBuilder;
27 use rustc::ty::{self, layout::VariantIdx, Ty, TyCtxt};
28 use rustc_ast::ast::{self, Expr};
29 use rustc_ast::attr::{self, HasAttrs};
30 use rustc_ast::tokenstream::{TokenStream, TokenTree};
31 use rustc_ast::visit::{FnCtxt, FnKind};
32 use rustc_ast_pretty::pprust::{self, expr_to_string};
33 use rustc_data_structures::fx::FxHashSet;
34 use rustc_errors::{Applicability, DiagnosticBuilder};
35 use rustc_feature::Stability;
36 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
38 use rustc_hir::def::{DefKind, Res};
39 use rustc_hir::def_id::DefId;
40 use rustc_hir::{GenericParamKind, PatKind};
41 use rustc_hir::{HirIdSet, Node};
42 use rustc_session::lint::FutureIncompatibleInfo;
43 use rustc_span::edition::Edition;
44 use rustc_span::source_map::Spanned;
45 use rustc_span::symbol::{kw, sym, Symbol};
46 use rustc_span::{BytePos, Span};
47 use rustc_trait_selection::traits::misc::can_type_implement_copy;
49 use crate::nonstandard_style::{method_context, MethodLateContext};
54 // hardwired lints from librustc
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().def_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_ty in ty.walk() {
109 if leaf_ty.is_box() {
110 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
111 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
118 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
119 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
121 hir::ItemKind::Fn(..)
122 | hir::ItemKind::TyAlias(..)
123 | hir::ItemKind::Enum(..)
124 | hir::ItemKind::Struct(..)
125 | hir::ItemKind::Union(..) => {
126 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
127 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
132 // If it's a struct, we also have to check the fields' types
134 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
135 for struct_field in struct_def.fields() {
136 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
137 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
144 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
145 let ty = cx.tables.node_type(e.hir_id);
146 self.check_heap_type(cx, e.span, ty);
151 NON_SHORTHAND_FIELD_PATTERNS,
153 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
156 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
158 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
159 fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat<'_>) {
160 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
165 .expect("struct pattern type is not an ADT")
166 .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
167 for fieldpat in field_pats {
168 if fieldpat.is_shorthand {
171 if fieldpat.span.from_expansion() {
172 // Don't lint if this is a macro expansion: macro authors
173 // shouldn't have to worry about this kind of style issue
177 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
178 if cx.tcx.find_field_index(ident, &variant)
179 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables))
181 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
183 .build(&format!("the `{}:` in this pattern is redundant", ident));
184 let binding = match binding_annot {
185 hir::BindingAnnotation::Unannotated => None,
186 hir::BindingAnnotation::Mutable => Some("mut"),
187 hir::BindingAnnotation::Ref => Some("ref"),
188 hir::BindingAnnotation::RefMut => Some("ref mut"),
190 let ident = if let Some(binding) = binding {
191 format!("{} {}", binding, ident)
197 "use shorthand field pattern",
199 Applicability::MachineApplicable,
213 "usage of `unsafe` code"
216 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
221 cx: &EarlyContext<'_>,
223 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
225 // This comes from a macro that has `#[allow_internal_unsafe]`.
226 if span.allows_unsafe() {
230 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
234 impl EarlyLintPass for UnsafeCode {
235 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
236 if attr.check_name(sym::allow_internal_unsafe) {
237 self.report_unsafe(cx, attr.span, |lint| {
239 "`allow_internal_unsafe` allows defining \
240 macros using unsafe without triggering \
241 the `unsafe_code` lint at their call site",
248 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
249 if let ast::ExprKind::Block(ref blk, _) = e.kind {
250 // Don't warn about generated blocks; that'll just pollute the output.
251 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
252 self.report_unsafe(cx, blk.span, |lint| {
253 lint.build("usage of an `unsafe` block").emit()
259 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
261 ast::ItemKind::Trait(_, ast::Unsafe::Yes(_), ..) => {
262 self.report_unsafe(cx, it.span, |lint| {
263 lint.build("declaration of an `unsafe` trait").emit()
267 ast::ItemKind::Impl { unsafety: ast::Unsafe::Yes(_), .. } => {
268 self.report_unsafe(cx, it.span, |lint| {
269 lint.build("implementation of an `unsafe` trait").emit()
277 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
281 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
286 let msg = match ctxt {
287 FnCtxt::Foreign => return,
288 FnCtxt::Free => "declaration of an `unsafe` function",
289 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
290 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
292 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
300 "detects missing documentation for public members",
301 report_in_external_macro
304 pub struct MissingDoc {
305 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
306 doc_hidden_stack: Vec<bool>,
308 /// Private traits or trait items that leaked through. Don't check their methods.
309 private_traits: FxHashSet<hir::HirId>,
312 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
314 fn has_doc(attr: &ast::Attribute) -> bool {
315 if attr.is_doc_comment() {
319 if !attr.check_name(sym::doc) {
323 if attr.is_value_str() {
327 if let Some(list) = attr.meta_item_list() {
329 if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
339 pub fn new() -> MissingDoc {
340 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
343 fn doc_hidden(&self) -> bool {
344 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
347 fn check_missing_docs_attrs(
349 cx: &LateContext<'_, '_>,
350 id: Option<hir::HirId>,
351 attrs: &[ast::Attribute],
355 // If we're building a test harness, then warning about
356 // documentation is probably not really relevant right now.
357 if cx.sess().opts.test {
361 // `#[doc(hidden)]` disables missing_docs check.
362 if self.doc_hidden() {
366 // Only check publicly-visible items, using the result from the privacy pass.
367 // It's an option so the crate root can also use this function (it doesn't
369 if let Some(id) = id {
370 if !cx.access_levels.is_exported(id) {
375 let has_doc = attrs.iter().any(|a| has_doc(a));
377 cx.struct_span_lint(MISSING_DOCS, cx.tcx.sess.source_map().def_span(sp), |lint| {
378 lint.build(&format!("missing documentation for {}", desc)).emit()
384 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
385 fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
386 let doc_hidden = self.doc_hidden()
387 || attrs.iter().any(|attr| {
388 attr.check_name(sym::doc)
389 && match attr.meta_item_list() {
391 Some(l) => attr::list_contains_name(&l, sym::hidden),
394 self.doc_hidden_stack.push(doc_hidden);
397 fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
398 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
401 fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate<'_>) {
402 self.check_missing_docs_attrs(cx, None, &krate.item.attrs, krate.item.span, "crate");
404 for macro_def in krate.exported_macros {
405 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
409 cx.tcx.sess.source_map().def_span(macro_def.span),
410 |lint| lint.build("missing documentation for macro").emit(),
416 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
417 let desc = match it.kind {
418 hir::ItemKind::Fn(..) => "a function",
419 hir::ItemKind::Mod(..) => "a module",
420 hir::ItemKind::Enum(..) => "an enum",
421 hir::ItemKind::Struct(..) => "a struct",
422 hir::ItemKind::Union(..) => "a union",
423 hir::ItemKind::Trait(.., trait_item_refs) => {
424 // Issue #11592: traits are always considered exported, even when private.
425 if let hir::VisibilityKind::Inherited = it.vis.node {
426 self.private_traits.insert(it.hir_id);
427 for trait_item_ref in trait_item_refs {
428 self.private_traits.insert(trait_item_ref.id.hir_id);
434 hir::ItemKind::TyAlias(..) => "a type alias",
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(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
440 match cx.tcx.hir().find(hir_id) {
441 Some(Node::Item(item)) => {
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);
453 hir::ItemKind::Const(..) => "a constant",
454 hir::ItemKind::Static(..) => "a static",
458 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
461 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem<'_>) {
462 if self.private_traits.contains(&trait_item.hir_id) {
466 let desc = match trait_item.kind {
467 hir::TraitItemKind::Const(..) => "an associated constant",
468 hir::TraitItemKind::Fn(..) => "a trait method",
469 hir::TraitItemKind::Type(..) => "an associated type",
472 self.check_missing_docs_attrs(
474 Some(trait_item.hir_id),
481 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
482 // If the method is an impl for a trait, don't doc.
483 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
487 let desc = match impl_item.kind {
488 hir::ImplItemKind::Const(..) => "an associated constant",
489 hir::ImplItemKind::Method(..) => "a method",
490 hir::ImplItemKind::TyAlias(_) => "an associated type",
491 hir::ImplItemKind::OpaqueTy(_) => "an associated `impl Trait` type",
493 self.check_missing_docs_attrs(
495 Some(impl_item.hir_id),
502 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField<'_>) {
503 if !sf.is_positional() {
504 self.check_missing_docs_attrs(cx, Some(sf.hir_id), &sf.attrs, sf.span, "a struct field")
508 fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant<'_>) {
509 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a variant");
514 pub MISSING_COPY_IMPLEMENTATIONS,
516 "detects potentially-forgotten implementations of `Copy`"
519 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
521 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
522 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
523 if !cx.access_levels.is_reachable(item.hir_id) {
526 let (def, ty) = match item.kind {
527 hir::ItemKind::Struct(_, ref ast_generics) => {
528 if !ast_generics.params.is_empty() {
531 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
532 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
534 hir::ItemKind::Union(_, ref ast_generics) => {
535 if !ast_generics.params.is_empty() {
538 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
539 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
541 hir::ItemKind::Enum(_, ref ast_generics) => {
542 if !ast_generics.params.is_empty() {
545 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
546 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
550 if def.has_dtor(cx.tcx) {
553 let param_env = ty::ParamEnv::empty();
554 if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
557 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
558 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
560 "type could implement `Copy`; consider adding `impl \
570 MISSING_DEBUG_IMPLEMENTATIONS,
572 "detects missing implementations of Debug"
576 pub struct MissingDebugImplementations {
577 impling_types: Option<HirIdSet>,
580 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
582 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
583 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
584 if !cx.access_levels.is_reachable(item.hir_id) {
589 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
593 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
594 Some(debug) => debug,
598 if self.impling_types.is_none() {
599 let mut impls = HirIdSet::default();
600 cx.tcx.for_each_impl(debug, |d| {
601 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
602 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
603 impls.insert(hir_id);
608 self.impling_types = Some(impls);
609 debug!("{:?}", self.impling_types);
612 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
613 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
615 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
616 or a manual implementation",
617 cx.tcx.def_path_str(debug)
626 pub ANONYMOUS_PARAMETERS,
628 "detects anonymous parameters",
629 @future_incompatible = FutureIncompatibleInfo {
630 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
631 edition: Some(Edition::Edition2018),
636 /// Checks for use of anonymous parameters (RFC 1685).
637 AnonymousParameters => [ANONYMOUS_PARAMETERS]
640 impl EarlyLintPass for AnonymousParameters {
641 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
643 ast::AssocItemKind::Fn(_, ref sig, _, _) => {
644 for arg in sig.decl.inputs.iter() {
646 ast::PatKind::Ident(_, ident, None) => {
647 if ident.name == kw::Invalid {
648 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
649 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
651 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
652 (snip.as_str(), Applicability::MachineApplicable)
654 ("<type>", Applicability::HasPlaceholders)
658 "anonymous parameters are deprecated and will be \
659 removed in the next edition.",
663 "try naming the parameter or explicitly \
665 format!("_: {}", ty_snip),
681 /// Check for use of attributes which have been deprecated.
683 pub struct DeprecatedAttr {
684 // This is not free to compute, so we want to keep it around, rather than
685 // compute it for every attribute.
686 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
689 impl_lint_pass!(DeprecatedAttr => []);
691 impl DeprecatedAttr {
692 pub fn new() -> DeprecatedAttr {
693 DeprecatedAttr { depr_attrs: deprecated_attributes() }
697 fn lint_deprecated_attr(
698 cx: &EarlyContext<'_>,
699 attr: &ast::Attribute,
701 suggestion: Option<&str>,
703 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
705 .span_suggestion_short(
707 suggestion.unwrap_or("remove this attribute"),
709 Applicability::MachineApplicable,
715 impl EarlyLintPass for DeprecatedAttr {
716 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
717 for &&(n, _, _, ref g) in &self.depr_attrs {
718 if attr.ident().map(|ident| ident.name) == Some(n) {
719 if let &AttributeGate::Gated(
720 Stability::Deprecated(link, suggestion),
727 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
728 lint_deprecated_attr(cx, attr, &msg, suggestion);
733 if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
734 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
735 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
736 lint_deprecated_attr(cx, attr, &msg, None);
741 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
742 let mut attrs = attrs.iter().peekable();
744 // Accumulate a single span for sugared doc comments.
745 let mut sugared_span: Option<Span> = None;
747 while let Some(attr) = attrs.next() {
748 if attr.is_doc_comment() {
750 Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
753 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
757 let span = sugared_span.take().unwrap_or_else(|| attr.span);
759 if attr.is_doc_comment() || attr.check_name(sym::doc) {
760 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
761 let mut err = lint.build("unused doc comment");
764 format!("rustdoc does not generate documentation for {}", node_kind),
772 impl EarlyLintPass for UnusedDocComment {
773 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
774 let kind = match stmt.kind {
775 ast::StmtKind::Local(..) => "statements",
776 ast::StmtKind::Item(..) => "inner items",
777 // expressions will be reported by `check_expr`.
779 | ast::StmtKind::Semi(_)
780 | ast::StmtKind::Expr(_)
781 | ast::StmtKind::Mac(_) => return,
784 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
787 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
788 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
789 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
792 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
793 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
798 NO_MANGLE_CONST_ITEMS,
800 "const items will not have their symbols exported"
804 NO_MANGLE_GENERIC_ITEMS,
806 "generic items must be mangled"
809 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
811 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
812 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
814 hir::ItemKind::Fn(.., ref generics, _) => {
815 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
816 for param in generics.params {
818 GenericParamKind::Lifetime { .. } => {}
819 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
820 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
822 "functions generic over types or consts must be mangled",
824 .span_suggestion_short(
826 "remove this attribute",
828 // Use of `#[no_mangle]` suggests FFI intent; correct
829 // fix may be to monomorphize source by hand
830 Applicability::MaybeIncorrect,
840 hir::ItemKind::Const(..) => {
841 if attr::contains_name(&it.attrs, sym::no_mangle) {
842 // Const items do not refer to a particular location in memory, and therefore
843 // don't have anything to attach a symbol to
844 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
845 let msg = "const items should never be `#[no_mangle]`";
846 let mut err = lint.build(msg);
848 // account for "pub const" (#45562)
853 .span_to_snippet(it.span)
854 .map(|snippet| snippet.find("const").unwrap_or(0))
855 .unwrap_or(0) as u32;
856 // `const` is 5 chars
857 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
860 "try a static value",
861 "pub static".to_owned(),
862 Applicability::MachineApplicable,
876 "mutating transmuted &mut T from &T may cause undefined behavior"
879 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
881 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
882 fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
883 use rustc_target::spec::abi::Abi::RustIntrinsic;
885 match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind)) {
886 Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
887 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
888 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
889 consider instead using an UnsafeCell";
890 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
891 lint.build(msg).emit()
898 fn get_transmute_from_to<'a, 'tcx>(
899 cx: &LateContext<'a, 'tcx>,
900 expr: &hir::Expr<'_>,
901 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
902 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
903 cx.tables.qpath_res(qpath, expr.hir_id)
907 if let Res::Def(DefKind::Fn, did) = def {
908 if !def_id_is_transmute(cx, did) {
911 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
912 let from = sig.inputs().skip_binder()[0];
913 let to = *sig.output().skip_binder();
914 return Some((from, to));
919 fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
920 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
921 && cx.tcx.item_name(def_id) == sym::transmute
929 "enabling unstable features (deprecated. do not use)"
933 /// Forbids using the `#[feature(...)]` attribute
934 UnstableFeatures => [UNSTABLE_FEATURES]
937 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
938 fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
939 if attr.check_name(sym::feature) {
940 if let Some(items) = attr.meta_item_list() {
942 ctx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
943 lint.build("unstable feature").emit()
954 "`pub` items not reachable from crate root"
958 /// Lint for items marked `pub` that aren't reachable from other crates.
959 UnreachablePub => [UNREACHABLE_PUB]
962 impl UnreachablePub {
965 cx: &LateContext<'_, '_>,
968 vis: &hir::Visibility<'_>,
972 let mut applicability = Applicability::MachineApplicable;
974 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
975 if span.from_expansion() {
976 applicability = Applicability::MaybeIncorrect;
978 let def_span = cx.tcx.sess.source_map().def_span(span);
979 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
980 let mut err = lint.build(&format!("unreachable `pub` {}", what));
981 let replacement = if cx.tcx.features().crate_visibility_modifier {
990 "consider restricting its visibility",
995 err.help("or consider exporting it for use by other crates");
1005 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1006 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1007 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1010 fn check_foreign_item(
1012 cx: &LateContext<'_, '_>,
1013 foreign_item: &hir::ForeignItem<'tcx>,
1018 foreign_item.hir_id,
1025 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1026 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1029 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1030 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1037 "bounds in type aliases are not enforced"
1041 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1042 /// They are relevant when using associated types, but otherwise neither checked
1043 /// at definition site nor enforced at use site.
1044 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1047 impl TypeAliasBounds {
1048 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1050 hir::QPath::TypeRelative(ref ty, _) => {
1051 // If this is a type variable, we found a `T::Assoc`.
1053 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1054 Res::Def(DefKind::TyParam, _) => true,
1060 hir::QPath::Resolved(..) => false,
1064 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1065 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1066 // bound. Let's see if this type does that.
1068 // We use a HIR visitor to walk the type.
1069 use rustc_hir::intravisit::{self, Visitor};
1070 struct WalkAssocTypes<'a, 'db> {
1071 err: &'a mut DiagnosticBuilder<'db>,
1073 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1076 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1077 intravisit::NestedVisitorMap::None
1080 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1081 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1084 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1085 associated types in type aliases",
1088 intravisit::walk_qpath(self, qpath, id, span)
1092 // Let's go for a walk!
1093 let mut visitor = WalkAssocTypes { err };
1094 visitor.visit_ty(ty);
1098 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1099 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1100 let (ty, type_alias_generics) = match item.kind {
1101 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1104 let mut suggested_changing_assoc_types = false;
1105 // There must not be a where clause
1106 if !type_alias_generics.where_clause.predicates.is_empty() {
1110 let mut err = lint.build("where clauses are not enforced in type aliases");
1111 let spans: Vec<_> = type_alias_generics
1115 .map(|pred| pred.span())
1117 err.set_span(spans);
1118 err.span_suggestion(
1119 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1120 "the clause will not be checked when the type alias is used, and should be removed",
1122 Applicability::MachineApplicable,
1124 if !suggested_changing_assoc_types {
1125 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1126 suggested_changing_assoc_types = true;
1132 // The parameters must not have bounds
1133 for param in type_alias_generics.params.iter() {
1134 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1135 let suggestion = spans
1138 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1139 (start.to(*sp), String::new())
1142 if !spans.is_empty() {
1143 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1145 lint.build("bounds on generic parameters are not enforced in type aliases");
1146 let msg = "the bound will not be checked when the type alias is used, \
1147 and should be removed";
1148 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1149 if !suggested_changing_assoc_types {
1150 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1151 suggested_changing_assoc_types = true;
1161 /// Lint constants that are erroneous.
1162 /// Without this lint, we might not get any diagnostic if the constant is
1163 /// unused within this crate, even though downstream crates can't use it
1164 /// without producing an error.
1165 UnusedBrokenConst => []
1168 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1169 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1170 // trigger the query once for all constants since that will already report the errors
1171 // FIXME: Use ensure here
1172 let _ = cx.tcx.const_eval_poly(def_id);
1175 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1176 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1178 hir::ItemKind::Const(_, body_id) => {
1179 check_const(cx, body_id);
1181 hir::ItemKind::Static(_, _, body_id) => {
1182 check_const(cx, body_id);
1192 "these bounds don't depend on an type parameters"
1196 /// Lint for trait and lifetime bounds that don't depend on type parameters
1197 /// which either do nothing, or stop the item from being used.
1198 TrivialConstraints => [TRIVIAL_BOUNDS]
1201 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1202 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1203 use rustc::ty::fold::TypeFoldable;
1204 use rustc::ty::Predicate::*;
1206 if cx.tcx.features().trivial_bounds {
1207 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1208 let predicates = cx.tcx.predicates_of(def_id);
1209 for &(predicate, span) in predicates.predicates {
1210 let predicate_kind_name = match predicate {
1211 Trait(..) => "Trait",
1213 RegionOutlives(..) => "Lifetime",
1215 // Ignore projections, as they can only be global
1216 // if the trait bound is global
1218 // Ignore bounds that a user can't type
1223 ConstEvaluatable(..) => continue,
1225 if predicate.is_global() {
1226 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1227 lint.build(&format!(
1228 "{} bound {} does not depend on any type \
1229 or lifetime parameters",
1230 predicate_kind_name, predicate
1241 /// Does nothing as a lint pass, but registers some `Lint`s
1242 /// which are used by other parts of the compiler.
1246 NON_SHORTHAND_FIELD_PATTERNS,
1249 MISSING_COPY_IMPLEMENTATIONS,
1250 MISSING_DEBUG_IMPLEMENTATIONS,
1251 ANONYMOUS_PARAMETERS,
1252 UNUSED_DOC_COMMENTS,
1253 NO_MANGLE_CONST_ITEMS,
1254 NO_MANGLE_GENERIC_ITEMS,
1264 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1266 "`...` range patterns are deprecated"
1270 pub struct EllipsisInclusiveRangePatterns {
1271 /// If `Some(_)`, suppress all subsequent pattern
1272 /// warnings for better diagnostics.
1273 node_id: Option<ast::NodeId>,
1276 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1278 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1279 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1280 if self.node_id.is_some() {
1281 // Don't recursively warn about patterns inside range endpoints.
1285 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1287 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1288 /// corresponding to the ellipsis.
1289 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1294 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1295 ) => Some((a.as_deref(), b, *span)),
1300 let (parenthesise, endpoints) = match &pat.kind {
1301 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1302 _ => (false, matches_ellipsis_pat(pat)),
1305 if let Some((start, end, join)) = endpoints {
1306 let msg = "`...` range patterns are deprecated";
1307 let suggestion = "use `..=` for an inclusive range";
1309 self.node_id = Some(pat.id);
1310 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1311 let end = expr_to_string(&end);
1312 let replace = match start {
1313 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1314 None => format!("&(..={})", end),
1321 Applicability::MachineApplicable,
1326 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1328 .span_suggestion_short(
1332 Applicability::MachineApplicable,
1340 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1341 if let Some(node_id) = self.node_id {
1342 if pat.id == node_id {
1350 UNNAMEABLE_TEST_ITEMS,
1352 "detects an item that cannot be named being marked as `#[test_case]`",
1353 report_in_external_macro
1356 pub struct UnnameableTestItems {
1357 boundary: hir::HirId, // HirId of the item under which things are not nameable
1358 items_nameable: bool,
1361 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1363 impl UnnameableTestItems {
1364 pub fn new() -> Self {
1365 Self { boundary: hir::DUMMY_HIR_ID, items_nameable: true }
1369 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1370 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1371 if self.items_nameable {
1372 if let hir::ItemKind::Mod(..) = it.kind {
1374 self.items_nameable = false;
1375 self.boundary = it.hir_id;
1380 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1381 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1382 lint.build("cannot test inner items").emit()
1387 fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1388 if !self.items_nameable && self.boundary == it.hir_id {
1389 self.items_nameable = true;
1397 "detects edition keywords being used as an identifier",
1398 @future_incompatible = FutureIncompatibleInfo {
1399 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1400 edition: Some(Edition::Edition2018),
1405 /// Check for uses of edition keywords used as an identifier.
1406 KeywordIdents => [KEYWORD_IDENTS]
1409 struct UnderMacro(bool);
1411 impl KeywordIdents {
1412 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1413 for tt in tokens.into_trees() {
1415 // Only report non-raw idents.
1416 TokenTree::Token(token) => {
1417 if let Some((ident, false)) = token.ident() {
1418 self.check_ident_token(cx, UnderMacro(true), ident);
1421 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1426 fn check_ident_token(
1428 cx: &EarlyContext<'_>,
1429 UnderMacro(under_macro): UnderMacro,
1432 let next_edition = match cx.sess.edition() {
1433 Edition::Edition2015 => {
1435 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1437 // rust-lang/rust#56327: Conservatively do not
1438 // attempt to report occurrences of `dyn` within
1439 // macro definitions or invocations, because `dyn`
1440 // can legitimately occur as a contextual keyword
1441 // in 2015 code denoting its 2018 meaning, and we
1442 // do not want rustfix to inject bugs into working
1443 // code by rewriting such occurrences.
1445 // But if we see `dyn` outside of a macro, we know
1446 // its precise role in the parsed AST and thus are
1447 // assured this is truly an attempt to use it as
1449 kw::Dyn if !under_macro => Edition::Edition2018,
1455 // There are no new keywords yet for the 2018 edition and beyond.
1459 // Don't lint `r#foo`.
1460 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1464 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1465 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1468 "you can use a raw identifier to stay compatible",
1469 format!("r#{}", ident),
1470 Applicability::MachineApplicable,
1477 impl EarlyLintPass for KeywordIdents {
1478 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1479 self.check_tokens(cx, mac_def.body.inner_tokens());
1481 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1482 self.check_tokens(cx, mac.args.inner_tokens());
1484 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1485 self.check_ident_token(cx, UnderMacro(false), ident);
1489 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1491 impl ExplicitOutlivesRequirements {
1492 fn lifetimes_outliving_lifetime<'tcx>(
1493 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1495 ) -> Vec<ty::Region<'tcx>> {
1498 .filter_map(|(pred, _)| match pred {
1499 ty::Predicate::RegionOutlives(outlives) => {
1500 let outlives = outlives.skip_binder();
1502 ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1511 fn lifetimes_outliving_type<'tcx>(
1512 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1514 ) -> Vec<ty::Region<'tcx>> {
1517 .filter_map(|(pred, _)| match pred {
1518 ty::Predicate::TypeOutlives(outlives) => {
1519 let outlives = outlives.skip_binder();
1520 outlives.0.is_param(index).then_some(outlives.1)
1527 fn collect_outlived_lifetimes<'tcx>(
1529 param: &'tcx hir::GenericParam<'tcx>,
1531 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1532 ty_generics: &'tcx ty::Generics,
1533 ) -> Vec<ty::Region<'tcx>> {
1534 let index = ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id)];
1537 hir::GenericParamKind::Lifetime { .. } => {
1538 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1540 hir::GenericParamKind::Type { .. } => {
1541 Self::lifetimes_outliving_type(inferred_outlives, index)
1543 hir::GenericParamKind::Const { .. } => Vec::new(),
1547 fn collect_outlives_bound_spans<'tcx>(
1550 bounds: &hir::GenericBounds<'_>,
1551 inferred_outlives: &[ty::Region<'tcx>],
1553 ) -> Vec<(usize, Span)> {
1554 use rustc::middle::resolve_lifetime::Region;
1559 .filter_map(|(i, bound)| {
1560 if let hir::GenericBound::Outlives(lifetime) = bound {
1561 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1562 Some(Region::Static) if infer_static => inferred_outlives
1564 .any(|r| if let ty::ReStatic = r { true } else { false }),
1565 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1566 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1570 is_inferred.then_some((i, bound.span()))
1578 fn consolidate_outlives_bound_spans(
1581 bounds: &hir::GenericBounds<'_>,
1582 bound_spans: Vec<(usize, Span)>,
1584 if bounds.is_empty() {
1587 if bound_spans.len() == bounds.len() {
1588 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1589 // If all bounds are inferable, we want to delete the colon, so
1590 // start from just after the parameter (span passed as argument)
1591 vec![lo.to(last_bound_span)]
1593 let mut merged = Vec::new();
1594 let mut last_merged_i = None;
1596 let mut from_start = true;
1597 for (i, bound_span) in bound_spans {
1598 match last_merged_i {
1599 // If the first bound is inferable, our span should also eat the leading `+`.
1601 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1602 last_merged_i = Some(0);
1604 // If consecutive bounds are inferable, merge their spans
1605 Some(h) if i == h + 1 => {
1606 if let Some(tail) = merged.last_mut() {
1607 // Also eat the trailing `+` if the first
1608 // more-than-one bound is inferable
1609 let to_span = if from_start && i < bounds.len() {
1610 bounds[i + 1].span().shrink_to_lo()
1614 *tail = tail.to(to_span);
1615 last_merged_i = Some(i);
1617 bug!("another bound-span visited earlier");
1621 // When we find a non-inferable bound, subsequent inferable bounds
1622 // won't be consecutive from the start (and we'll eat the leading
1623 // `+` rather than the trailing one)
1625 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1626 last_merged_i = Some(i);
1635 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1636 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1637 use rustc::middle::resolve_lifetime::Region;
1639 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1640 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1641 if let hir::ItemKind::Struct(_, ref hir_generics)
1642 | hir::ItemKind::Enum(_, ref hir_generics)
1643 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1645 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1646 if inferred_outlives.is_empty() {
1650 let ty_generics = cx.tcx.generics_of(def_id);
1652 let mut bound_count = 0;
1653 let mut lint_spans = Vec::new();
1655 for param in hir_generics.params {
1656 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1657 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1659 if !has_lifetime_bounds {
1663 let relevant_lifetimes =
1664 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1665 if relevant_lifetimes.is_empty() {
1669 let bound_spans = self.collect_outlives_bound_spans(
1672 &relevant_lifetimes,
1675 bound_count += bound_spans.len();
1676 lint_spans.extend(self.consolidate_outlives_bound_spans(
1677 param.span.shrink_to_hi(),
1683 let mut where_lint_spans = Vec::new();
1684 let mut dropped_predicate_count = 0;
1685 let num_predicates = hir_generics.where_clause.predicates.len();
1686 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1687 let (relevant_lifetimes, bounds, span) = match where_predicate {
1688 hir::WherePredicate::RegionPredicate(predicate) => {
1689 if let Some(Region::EarlyBound(index, ..)) =
1690 cx.tcx.named_region(predicate.lifetime.hir_id)
1693 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1701 hir::WherePredicate::BoundPredicate(predicate) => {
1702 // FIXME we can also infer bounds on associated types,
1703 // and should check for them here.
1704 match predicate.bounded_ty.kind {
1705 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1706 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1707 let index = ty_generics.param_def_id_to_index[&def_id];
1709 Self::lifetimes_outliving_type(inferred_outlives, index),
1724 if relevant_lifetimes.is_empty() {
1728 let bound_spans = self.collect_outlives_bound_spans(
1731 &relevant_lifetimes,
1734 bound_count += bound_spans.len();
1736 let drop_predicate = bound_spans.len() == bounds.len();
1738 dropped_predicate_count += 1;
1741 // If all the bounds on a predicate were inferable and there are
1742 // further predicates, we want to eat the trailing comma.
1743 if drop_predicate && i + 1 < num_predicates {
1744 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1745 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1747 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1748 span.shrink_to_lo(),
1755 // If all predicates are inferable, drop the entire clause
1756 // (including the `where`)
1757 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1758 let where_span = hir_generics
1761 .expect("span of (nonempty) where clause should exist");
1762 // Extend the where clause back to the closing `>` of the
1763 // generics, except for tuple struct, which have the `where`
1764 // after the fields of the struct.
1765 let full_where_span =
1766 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1769 hir_generics.span.shrink_to_hi().to(where_span)
1771 lint_spans.push(full_where_span);
1773 lint_spans.extend(where_lint_spans);
1776 if !lint_spans.is_empty() {
1777 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1778 lint.build("outlives requirements can be inferred")
1779 .multipart_suggestion(
1780 if bound_count == 1 {
1783 "remove these bounds"
1787 .map(|span| (span, "".to_owned()))
1788 .collect::<Vec<_>>(),
1789 Applicability::MachineApplicable,
1799 pub INCOMPLETE_FEATURES,
1801 "incomplete features that may function improperly in some or all cases"
1805 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1806 IncompleteFeatures => [INCOMPLETE_FEATURES]
1809 impl EarlyLintPass for IncompleteFeatures {
1810 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1811 let features = cx.sess.features_untracked();
1813 .declared_lang_features
1815 .map(|(name, span, _)| (name, span))
1816 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1817 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1818 .for_each(|(name, &span)| {
1819 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1820 lint.build(&format!(
1821 "the feature `{}` is incomplete and may cause the compiler to crash",
1833 "an invalid value is being created (such as a NULL reference)"
1836 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1838 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1839 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1840 #[derive(Debug, Copy, Clone, PartialEq)]
1846 /// Information about why a type cannot be initialized this way.
1847 /// Contains an error message and optionally a span to point at.
1848 type InitError = (String, Option<Span>);
1850 /// Test if this constant is all-0.
1851 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1852 use hir::ExprKind::*;
1853 use rustc_ast::ast::LitKind::*;
1856 if let Int(i, _) = lit.node {
1862 Tup(tup) => tup.iter().all(is_zero),
1867 /// Determine if this expression is a "dangerous initialization".
1868 fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1869 // `transmute` is inside an anonymous module (the `extern` block?);
1870 // `Invalid` represents the empty string and matches that.
1871 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1872 // on intrinsics right now.
1873 const TRANSMUTE_PATH: &[Symbol] =
1874 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1876 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1877 // Find calls to `mem::{uninitialized,zeroed}` methods.
1878 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1879 let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1881 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1882 return Some(InitKind::Zeroed);
1883 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1884 return Some(InitKind::Uninit);
1885 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1886 if is_zero(&args[0]) {
1887 return Some(InitKind::Zeroed);
1891 } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
1892 // Find problematic calls to `MaybeUninit::assume_init`.
1893 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1894 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1895 // This is a call to *some* method named `assume_init`.
1896 // See if the `self` parameter is one of the dangerous constructors.
1897 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1898 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1900 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1902 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1903 return Some(InitKind::Zeroed);
1904 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1905 return Some(InitKind::Uninit);
1915 /// Return `Some` only if we are sure this type does *not*
1916 /// allow zero initialization.
1917 fn ty_find_init_error<'tcx>(
1921 ) -> Option<InitError> {
1922 use rustc::ty::TyKind::*;
1924 // Primitive types that don't like 0 as a value.
1925 Ref(..) => Some(("references must be non-null".to_string(), None)),
1926 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
1927 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
1928 Never => Some(("the `!` type has no valid value".to_string(), None)),
1929 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1930 // raw ptr to dyn Trait
1932 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
1934 // Primitive types with other constraints.
1935 Bool if init == InitKind::Uninit => {
1936 Some(("booleans must be either `true` or `false`".to_string(), None))
1938 Char if init == InitKind::Uninit => {
1939 Some(("characters must be a valid Unicode codepoint".to_string(), None))
1941 // Recurse and checks for some compound types.
1942 Adt(adt_def, substs) if !adt_def.is_union() => {
1943 // First check f this ADT has a layout attribute (like `NonNull` and friends).
1944 use std::ops::Bound;
1945 match tcx.layout_scalar_valid_range(adt_def.did) {
1946 // We exploit here that `layout_scalar_valid_range` will never
1947 // return `Bound::Excluded`. (And we have tests checking that we
1948 // handle the attribute correctly.)
1949 (Bound::Included(lo), _) if lo > 0 => {
1950 return Some((format!("`{}` must be non-null", ty), None));
1952 (Bound::Included(_), _) | (_, Bound::Included(_))
1953 if init == InitKind::Uninit =>
1957 "`{}` must be initialized inside its custom valid range",
1966 match adt_def.variants.len() {
1967 0 => Some(("enums with no variants have no valid value".to_string(), None)),
1969 // Struct, or enum with exactly one variant.
1970 // Proceed recursively, check all fields.
1971 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1972 variant.fields.iter().find_map(|field| {
1973 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1976 // Point to this field, should be helpful for figuring
1977 // out where the source of the error is.
1978 let span = tcx.def_span(field.did);
1981 " (in this {} field)",
1994 // Multi-variant enums are tricky: if all but one variant are
1995 // uninhabited, we might actually do layout like for a single-variant
1996 // enum, and then even leaving them uninitialized could be okay.
1997 _ => None, // Conservative fallback for multi-variant enum.
2001 // Proceed recursively, check all fields.
2002 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2004 // Conservative fallback.
2009 if let Some(init) = is_dangerous_init(cx, expr) {
2010 // This conjures an instance of a type out of nothing,
2011 // using zeroed or uninitialized memory.
2012 // We are extremely conservative with what we warn about.
2013 let conjured_ty = cx.tables.expr_ty(expr);
2014 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2015 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2016 let mut err = lint.build(&format!(
2017 "the type `{}` does not permit {}",
2020 InitKind::Zeroed => "zero-initialization",
2021 InitKind::Uninit => "being left uninitialized",
2024 err.span_label(expr.span, "this code causes undefined behavior when executed");
2027 "help: use `MaybeUninit<T>` instead, \
2028 and only call `assume_init` after initialization is done",
2030 if let Some(span) = span {
2031 err.span_note(span, &msg);