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`.
26 use lint::{EarlyContext, EarlyLintPass, LateLintPass, LintPass};
27 use lint::{LateContext, LintArray, LintContext};
28 use rustc::hir::map::Map;
30 use rustc::lint::FutureIncompatibleInfo;
31 use rustc::traits::misc::can_type_implement_copy;
32 use rustc::ty::{self, layout::VariantIdx, Ty, TyCtxt};
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_span::edition::Edition;
43 use rustc_span::source_map::Spanned;
44 use rustc_span::symbol::{kw, sym, Symbol};
45 use rustc_span::{BytePos, Span};
46 use syntax::ast::{self, Expr};
47 use syntax::attr::{self, HasAttrs};
48 use syntax::print::pprust::{self, expr_to_string};
49 use syntax::tokenstream::{TokenStream, TokenTree};
50 use syntax::visit::FnKind;
52 use crate::nonstandard_style::{method_context, MethodLateContext};
56 // hardwired lints from librustc
57 pub use lint::builtin::*;
62 "suggest using `loop { }` instead of `while true { }`"
65 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
67 /// Traverse through any amount of parenthesis and return the first non-parens expression.
68 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
69 while let ast::ExprKind::Paren(sub) = &expr.kind {
75 impl EarlyLintPass for WhileTrue {
76 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
77 if let ast::ExprKind::While(cond, ..) = &e.kind {
78 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
79 if let ast::LitKind::Bool(true) = lit.kind {
80 if !lit.span.from_expansion() {
81 let msg = "denote infinite loops with `loop { ... }`";
82 let condition_span = cx.sess.source_map().def_span(e.span);
83 cx.struct_span_lint(WHILE_TRUE, condition_span, msg)
84 .span_suggestion_short(
88 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 let m = format!("type uses owned (Box type) pointers: {}", ty);
111 cx.span_lint(BOX_POINTERS, span, &m);
117 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
118 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
120 hir::ItemKind::Fn(..)
121 | hir::ItemKind::TyAlias(..)
122 | hir::ItemKind::Enum(..)
123 | hir::ItemKind::Struct(..)
124 | hir::ItemKind::Union(..) => {
125 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
126 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
131 // If it's a struct, we also have to check the fields' types
133 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
134 for struct_field in struct_def.fields() {
135 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
136 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
143 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
144 let ty = cx.tables.node_type(e.hir_id);
145 self.check_heap_type(cx, e.span, ty);
150 NON_SHORTHAND_FIELD_PATTERNS,
152 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
155 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
157 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
158 fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat<'_>) {
159 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
164 .expect("struct pattern type is not an ADT")
165 .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
166 for fieldpat in field_pats {
167 if fieldpat.is_shorthand {
170 if fieldpat.span.from_expansion() {
171 // Don't lint if this is a macro expansion: macro authors
172 // shouldn't have to worry about this kind of style issue
176 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
177 if cx.tcx.find_field_index(ident, &variant)
178 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables))
180 let mut err = cx.struct_span_lint(
181 NON_SHORTHAND_FIELD_PATTERNS,
183 &format!("the `{}:` in this pattern is redundant", ident),
185 let binding = match binding_annot {
186 hir::BindingAnnotation::Unannotated => None,
187 hir::BindingAnnotation::Mutable => Some("mut"),
188 hir::BindingAnnotation::Ref => Some("ref"),
189 hir::BindingAnnotation::RefMut => Some("ref mut"),
191 let ident = if let Some(binding) = binding {
192 format!("{} {}", binding, ident)
198 "use shorthand field pattern",
200 Applicability::MachineApplicable,
213 "usage of `unsafe` code"
216 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
219 fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
220 // This comes from a macro that has `#[allow_internal_unsafe]`.
221 if span.allows_unsafe() {
225 cx.span_lint(UNSAFE_CODE, span, desc);
229 impl EarlyLintPass for UnsafeCode {
230 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
231 if attr.check_name(sym::allow_internal_unsafe) {
235 "`allow_internal_unsafe` allows defining \
236 macros using unsafe without triggering \
237 the `unsafe_code` lint at their call site",
242 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
243 if let ast::ExprKind::Block(ref blk, _) = e.kind {
244 // Don't warn about generated blocks; that'll just pollute the output.
245 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
246 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
251 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
253 ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
254 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
257 ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
258 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
267 cx: &EarlyContext<'_>,
274 FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
275 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
278 FnKind::Method(_, sig, ..) => {
279 if sig.header.unsafety == ast::Unsafety::Unsafe {
280 self.report_unsafe(cx, span, "implementation of an `unsafe` method")
288 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::AssocItem) {
289 if let ast::AssocItemKind::Fn(ref sig, None) = item.kind {
290 if sig.header.unsafety == ast::Unsafety::Unsafe {
291 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
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));
379 cx.tcx.sess.source_map().def_span(sp),
380 &format!("missing documentation for {}", desc),
386 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
387 fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
388 let doc_hidden = self.doc_hidden()
389 || attrs.iter().any(|attr| {
390 attr.check_name(sym::doc)
391 && match attr.meta_item_list() {
393 Some(l) => attr::list_contains_name(&l, sym::hidden),
396 self.doc_hidden_stack.push(doc_hidden);
399 fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
400 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
403 fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate<'_>) {
404 self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
406 for macro_def in krate.exported_macros {
407 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
411 cx.tcx.sess.source_map().def_span(macro_def.span),
412 "missing documentation for macro",
418 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
419 let desc = match it.kind {
420 hir::ItemKind::Fn(..) => "a function",
421 hir::ItemKind::Mod(..) => "a module",
422 hir::ItemKind::Enum(..) => "an enum",
423 hir::ItemKind::Struct(..) => "a struct",
424 hir::ItemKind::Union(..) => "a union",
425 hir::ItemKind::Trait(.., trait_item_refs) => {
426 // Issue #11592: traits are always considered exported, even when private.
427 if let hir::VisibilityKind::Inherited = it.vis.node {
428 self.private_traits.insert(it.hir_id);
429 for trait_item_ref in trait_item_refs {
430 self.private_traits.insert(trait_item_ref.id.hir_id);
436 hir::ItemKind::TyAlias(..) => "a type alias",
437 hir::ItemKind::Impl(.., Some(ref trait_ref), _, impl_item_refs) => {
438 // If the trait is private, add the impl items to `private_traits` so they don't get
439 // reported for missing docs.
440 let real_trait = trait_ref.path.res.def_id();
441 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
442 match cx.tcx.hir().find(hir_id) {
443 Some(Node::Item(item)) => {
444 if let hir::VisibilityKind::Inherited = item.vis.node {
445 for impl_item_ref in impl_item_refs {
446 self.private_traits.insert(impl_item_ref.id.hir_id);
455 hir::ItemKind::Const(..) => "a constant",
456 hir::ItemKind::Static(..) => "a static",
460 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
463 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem<'_>) {
464 if self.private_traits.contains(&trait_item.hir_id) {
468 let desc = match trait_item.kind {
469 hir::TraitItemKind::Const(..) => "an associated constant",
470 hir::TraitItemKind::Method(..) => "a trait method",
471 hir::TraitItemKind::Type(..) => "an associated type",
474 self.check_missing_docs_attrs(
476 Some(trait_item.hir_id),
483 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
484 // If the method is an impl for a trait, don't doc.
485 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
489 let desc = match impl_item.kind {
490 hir::ImplItemKind::Const(..) => "an associated constant",
491 hir::ImplItemKind::Method(..) => "a method",
492 hir::ImplItemKind::TyAlias(_) => "an associated type",
493 hir::ImplItemKind::OpaqueTy(_) => "an associated `impl Trait` type",
495 self.check_missing_docs_attrs(
497 Some(impl_item.hir_id),
504 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField<'_>) {
505 if !sf.is_positional() {
506 self.check_missing_docs_attrs(cx, Some(sf.hir_id), &sf.attrs, sf.span, "a struct field")
510 fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant<'_>) {
511 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a variant");
516 pub MISSING_COPY_IMPLEMENTATIONS,
518 "detects potentially-forgotten implementations of `Copy`"
521 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
523 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
524 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
525 if !cx.access_levels.is_reachable(item.hir_id) {
528 let (def, ty) = match item.kind {
529 hir::ItemKind::Struct(_, ref ast_generics) => {
530 if !ast_generics.params.is_empty() {
533 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
534 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
536 hir::ItemKind::Union(_, ref ast_generics) => {
537 if !ast_generics.params.is_empty() {
540 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
541 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
543 hir::ItemKind::Enum(_, ref ast_generics) => {
544 if !ast_generics.params.is_empty() {
547 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
548 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
552 if def.has_dtor(cx.tcx) {
555 let param_env = ty::ParamEnv::empty();
556 if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
559 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
561 MISSING_COPY_IMPLEMENTATIONS,
563 "type could implement `Copy`; consider adding `impl \
571 MISSING_DEBUG_IMPLEMENTATIONS,
573 "detects missing implementations of fmt::Debug"
577 pub struct MissingDebugImplementations {
578 impling_types: Option<HirIdSet>,
581 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
583 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
584 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
585 if !cx.access_levels.is_reachable(item.hir_id) {
590 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
594 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
595 Some(debug) => debug,
599 if self.impling_types.is_none() {
600 let mut impls = HirIdSet::default();
601 cx.tcx.for_each_impl(debug, |d| {
602 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
603 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
604 impls.insert(hir_id);
609 self.impling_types = Some(impls);
610 debug!("{:?}", self.impling_types);
613 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
615 MISSING_DEBUG_IMPLEMENTATIONS,
617 "type does not implement `fmt::Debug`; consider adding `#[derive(Debug)]` \
618 or a manual implementation",
625 pub ANONYMOUS_PARAMETERS,
627 "detects anonymous parameters",
628 @future_incompatible = FutureIncompatibleInfo {
629 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
630 edition: Some(Edition::Edition2018),
635 /// Checks for use of anonymous parameters (RFC 1685).
636 AnonymousParameters => [ANONYMOUS_PARAMETERS]
639 impl EarlyLintPass for AnonymousParameters {
640 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
642 ast::AssocItemKind::Fn(ref sig, _) => {
643 for arg in sig.decl.inputs.iter() {
645 ast::PatKind::Ident(_, ident, None) => {
646 if ident.name == kw::Invalid {
647 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
649 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
650 (snip, Applicability::MachineApplicable)
652 ("<type>".to_owned(), Applicability::HasPlaceholders)
656 ANONYMOUS_PARAMETERS,
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),
680 /// Check for use of attributes which have been deprecated.
682 pub struct DeprecatedAttr {
683 // This is not free to compute, so we want to keep it around, rather than
684 // compute it for every attribute.
685 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
688 impl_lint_pass!(DeprecatedAttr => []);
690 impl DeprecatedAttr {
691 pub fn new() -> DeprecatedAttr {
692 DeprecatedAttr { depr_attrs: deprecated_attributes() }
696 fn lint_deprecated_attr(
697 cx: &EarlyContext<'_>,
698 attr: &ast::Attribute,
700 suggestion: Option<&str>,
702 cx.struct_span_lint(DEPRECATED, attr.span, &msg)
703 .span_suggestion_short(
705 suggestion.unwrap_or("remove this attribute"),
707 Applicability::MachineApplicable,
712 impl EarlyLintPass for DeprecatedAttr {
713 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
714 for &&(n, _, _, ref g) in &self.depr_attrs {
715 if attr.ident().map(|ident| ident.name) == Some(n) {
716 if let &AttributeGate::Gated(
717 Stability::Deprecated(link, suggestion),
724 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
725 lint_deprecated_attr(cx, attr, &msg, suggestion);
730 if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
731 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
732 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
733 lint_deprecated_attr(cx, attr, &msg, None);
739 pub UNUSED_DOC_COMMENTS,
741 "detects doc comments that aren't used by rustdoc"
744 declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
746 impl UnusedDocComment {
749 cx: &EarlyContext<'_>,
752 is_macro_expansion: bool,
753 attrs: &[ast::Attribute],
755 let mut attrs = attrs.into_iter().peekable();
757 // Accumulate a single span for sugared doc comments.
758 let mut sugared_span: Option<Span> = None;
760 while let Some(attr) = attrs.next() {
761 if attr.is_doc_comment() {
763 sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())),
767 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
771 let span = sugared_span.take().unwrap_or_else(|| attr.span);
773 if attr.is_doc_comment() || attr.check_name(sym::doc) {
774 let mut err = cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, "unused doc comment");
778 format!("rustdoc does not generate documentation for {}", node_kind),
781 if is_macro_expansion {
783 "to document an item produced by a macro, \
784 the macro must produce the documentation as part of its expansion",
794 impl EarlyLintPass for UnusedDocComment {
795 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
796 if let ast::ItemKind::Mac(..) = item.kind {
797 self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
801 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
802 let (kind, is_macro_expansion) = match stmt.kind {
803 ast::StmtKind::Local(..) => ("statements", false),
804 ast::StmtKind::Item(..) => ("inner items", false),
805 ast::StmtKind::Mac(..) => ("macro expansions", true),
806 // expressions will be reported by `check_expr`.
807 ast::StmtKind::Semi(..) | ast::StmtKind::Expr(..) => return,
810 self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.kind.attrs());
813 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
814 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
815 self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
818 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
819 self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
824 NO_MANGLE_CONST_ITEMS,
826 "const items will not have their symbols exported"
830 NO_MANGLE_GENERIC_ITEMS,
832 "generic items must be mangled"
835 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
837 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
838 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
840 hir::ItemKind::Fn(.., ref generics, _) => {
841 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
842 for param in generics.params {
844 GenericParamKind::Lifetime { .. } => {}
845 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
846 let mut err = cx.struct_span_lint(
847 NO_MANGLE_GENERIC_ITEMS,
849 "functions generic over types or consts must be mangled",
851 err.span_suggestion_short(
853 "remove this attribute",
855 // Use of `#[no_mangle]` suggests FFI intent; correct
856 // fix may be to monomorphize source by hand
857 Applicability::MaybeIncorrect,
866 hir::ItemKind::Const(..) => {
867 if attr::contains_name(&it.attrs, sym::no_mangle) {
868 // Const items do not refer to a particular location in memory, and therefore
869 // don't have anything to attach a symbol to
870 let msg = "const items should never be `#[no_mangle]`";
871 let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
873 // account for "pub const" (#45562)
878 .span_to_snippet(it.span)
879 .map(|snippet| snippet.find("const").unwrap_or(0))
880 .unwrap_or(0) as u32;
881 // `const` is 5 chars
882 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
885 "try a static value",
886 "pub static".to_owned(),
887 Applicability::MachineApplicable,
900 "mutating transmuted &mut T from &T may cause undefined behavior"
903 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
905 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
906 fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
907 use rustc_target::spec::abi::Abi::RustIntrinsic;
909 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
910 consider instead using an UnsafeCell";
911 match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind)) {
912 Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
913 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
914 cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
920 fn get_transmute_from_to<'a, 'tcx>(
921 cx: &LateContext<'a, 'tcx>,
922 expr: &hir::Expr<'_>,
923 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
924 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
925 cx.tables.qpath_res(qpath, expr.hir_id)
929 if let Res::Def(DefKind::Fn, did) = def {
930 if !def_id_is_transmute(cx, did) {
933 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
934 let from = sig.inputs().skip_binder()[0];
935 let to = *sig.output().skip_binder();
936 return Some((from, to));
941 fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
942 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
943 && cx.tcx.item_name(def_id) == sym::transmute
951 "enabling unstable features (deprecated. do not use)"
955 /// Forbids using the `#[feature(...)]` attribute
956 UnstableFeatures => [UNSTABLE_FEATURES]
959 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
960 fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
961 if attr.check_name(sym::feature) {
962 if let Some(items) = attr.meta_item_list() {
964 ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
974 "`pub` items not reachable from crate root"
978 /// Lint for items marked `pub` that aren't reachable from other crates.
979 UnreachablePub => [UNREACHABLE_PUB]
982 impl UnreachablePub {
985 cx: &LateContext<'_, '_>,
988 vis: &hir::Visibility<'_>,
992 let mut applicability = Applicability::MachineApplicable;
994 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
995 if span.from_expansion() {
996 applicability = Applicability::MaybeIncorrect;
998 let def_span = cx.tcx.sess.source_map().def_span(span);
999 let mut err = cx.struct_span_lint(
1002 &format!("unreachable `pub` {}", what),
1004 let replacement = if cx.tcx.features().crate_visibility_modifier {
1011 err.span_suggestion(
1013 "consider restricting its visibility",
1018 err.help("or consider exporting it for use by other crates");
1027 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1028 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1029 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1032 fn check_foreign_item(
1034 cx: &LateContext<'_, '_>,
1035 foreign_item: &hir::ForeignItem<'tcx>,
1040 foreign_item.hir_id,
1047 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1048 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1051 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1052 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1059 "bounds in type aliases are not enforced"
1063 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1064 /// They are relevant when using associated types, but otherwise neither checked
1065 /// at definition site nor enforced at use site.
1066 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1069 impl TypeAliasBounds {
1070 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1072 hir::QPath::TypeRelative(ref ty, _) => {
1073 // If this is a type variable, we found a `T::Assoc`.
1075 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1076 Res::Def(DefKind::TyParam, _) => true,
1082 hir::QPath::Resolved(..) => false,
1086 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1087 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1088 // bound. Let's see if this type does that.
1090 // We use a HIR visitor to walk the type.
1091 use rustc_hir::intravisit::{self, Visitor};
1092 struct WalkAssocTypes<'a, 'db> {
1093 err: &'a mut DiagnosticBuilder<'db>,
1095 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1098 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1099 intravisit::NestedVisitorMap::None
1102 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1103 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1106 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1107 associated types in type aliases",
1110 intravisit::walk_qpath(self, qpath, id, span)
1114 // Let's go for a walk!
1115 let mut visitor = WalkAssocTypes { err };
1116 visitor.visit_ty(ty);
1120 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1121 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1122 let (ty, type_alias_generics) = match item.kind {
1123 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1126 let mut suggested_changing_assoc_types = false;
1127 // There must not be a where clause
1128 if !type_alias_generics.where_clause.predicates.is_empty() {
1129 let spans: Vec<_> = type_alias_generics
1133 .map(|pred| pred.span())
1135 let mut err = cx.struct_span_lint(
1138 "where clauses are not enforced in type aliases",
1140 err.span_suggestion(
1141 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1142 "the clause will not be checked when the type alias is used, and should be removed",
1144 Applicability::MachineApplicable,
1146 if !suggested_changing_assoc_types {
1147 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1148 suggested_changing_assoc_types = true;
1152 // The parameters must not have bounds
1153 for param in type_alias_generics.params.iter() {
1154 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1155 let suggestion = spans
1158 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1159 (start.to(*sp), String::new())
1162 if !spans.is_empty() {
1163 let mut err = cx.struct_span_lint(
1166 "bounds on generic parameters are not enforced in type aliases",
1168 let msg = "the bound will not be checked when the type alias is used, \
1169 and should be removed";
1170 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1171 if !suggested_changing_assoc_types {
1172 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1173 suggested_changing_assoc_types = true;
1182 /// Lint constants that are erroneous.
1183 /// Without this lint, we might not get any diagnostic if the constant is
1184 /// unused within this crate, even though downstream crates can't use it
1185 /// without producing an error.
1186 UnusedBrokenConst => []
1189 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1190 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1191 // trigger the query once for all constants since that will already report the errors
1192 // FIXME: Use ensure here
1193 let _ = cx.tcx.const_eval_poly(def_id);
1196 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1197 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1199 hir::ItemKind::Const(_, body_id) => {
1200 check_const(cx, body_id);
1202 hir::ItemKind::Static(_, _, body_id) => {
1203 check_const(cx, body_id);
1213 "these bounds don't depend on an type parameters"
1217 /// Lint for trait and lifetime bounds that don't depend on type parameters
1218 /// which either do nothing, or stop the item from being used.
1219 TrivialConstraints => [TRIVIAL_BOUNDS]
1222 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1223 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1224 use rustc::ty::fold::TypeFoldable;
1225 use rustc::ty::Predicate::*;
1227 if cx.tcx.features().trivial_bounds {
1228 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1229 let predicates = cx.tcx.predicates_of(def_id);
1230 for &(predicate, span) in predicates.predicates {
1231 let predicate_kind_name = match predicate {
1232 Trait(..) => "Trait",
1234 RegionOutlives(..) => "Lifetime",
1236 // Ignore projections, as they can only be global
1237 // if the trait bound is global
1239 // Ignore bounds that a user can't type
1244 ConstEvaluatable(..) => continue,
1246 if predicate.is_global() {
1251 "{} bound {} does not depend on any type \
1252 or lifetime parameters",
1253 predicate_kind_name, predicate
1263 /// Does nothing as a lint pass, but registers some `Lint`s
1264 /// which are used by other parts of the compiler.
1268 NON_SHORTHAND_FIELD_PATTERNS,
1271 MISSING_COPY_IMPLEMENTATIONS,
1272 MISSING_DEBUG_IMPLEMENTATIONS,
1273 ANONYMOUS_PARAMETERS,
1274 UNUSED_DOC_COMMENTS,
1275 NO_MANGLE_CONST_ITEMS,
1276 NO_MANGLE_GENERIC_ITEMS,
1286 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1288 "`...` range patterns are deprecated"
1292 pub struct EllipsisInclusiveRangePatterns {
1293 /// If `Some(_)`, suppress all subsequent pattern
1294 /// warnings for better diagnostics.
1295 node_id: Option<ast::NodeId>,
1298 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1300 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1301 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1302 if self.node_id.is_some() {
1303 // Don't recursively warn about patterns inside range endpoints.
1307 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1309 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1310 /// corresponding to the ellipsis.
1311 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1316 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1317 ) => Some((a.as_deref(), b, *span)),
1322 let (parenthesise, endpoints) = match &pat.kind {
1323 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1324 _ => (false, matches_ellipsis_pat(pat)),
1327 if let Some((start, end, join)) = endpoints {
1328 let msg = "`...` range patterns are deprecated";
1329 let suggestion = "use `..=` for an inclusive range";
1331 self.node_id = Some(pat.id);
1332 let end = expr_to_string(&end);
1333 let replace = match start {
1334 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1335 None => format!("&(..={})", end),
1337 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1338 err.span_suggestion(
1342 Applicability::MachineApplicable,
1346 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1347 err.span_suggestion_short(
1351 Applicability::MachineApplicable,
1358 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1359 if let Some(node_id) = self.node_id {
1360 if pat.id == node_id {
1368 UNNAMEABLE_TEST_ITEMS,
1370 "detects an item that cannot be named being marked as `#[test_case]`",
1371 report_in_external_macro
1374 pub struct UnnameableTestItems {
1375 boundary: hir::HirId, // HirId of the item under which things are not nameable
1376 items_nameable: bool,
1379 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1381 impl UnnameableTestItems {
1382 pub fn new() -> Self {
1383 Self { boundary: hir::DUMMY_HIR_ID, items_nameable: true }
1387 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1388 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1389 if self.items_nameable {
1390 if let hir::ItemKind::Mod(..) = it.kind {
1392 self.items_nameable = false;
1393 self.boundary = it.hir_id;
1398 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1399 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, "cannot test inner items").emit();
1403 fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1404 if !self.items_nameable && self.boundary == it.hir_id {
1405 self.items_nameable = true;
1413 "detects edition keywords being used as an identifier",
1414 @future_incompatible = FutureIncompatibleInfo {
1415 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1416 edition: Some(Edition::Edition2018),
1421 /// Check for uses of edition keywords used as an identifier.
1422 KeywordIdents => [KEYWORD_IDENTS]
1425 struct UnderMacro(bool);
1427 impl KeywordIdents {
1428 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1429 for tt in tokens.into_trees() {
1431 // Only report non-raw idents.
1432 TokenTree::Token(token) => {
1433 if let Some((ident, false)) = token.ident() {
1434 self.check_ident_token(cx, UnderMacro(true), ident);
1437 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1442 fn check_ident_token(
1444 cx: &EarlyContext<'_>,
1445 UnderMacro(under_macro): UnderMacro,
1448 let next_edition = match cx.sess.edition() {
1449 Edition::Edition2015 => {
1451 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1453 // rust-lang/rust#56327: Conservatively do not
1454 // attempt to report occurrences of `dyn` within
1455 // macro definitions or invocations, because `dyn`
1456 // can legitimately occur as a contextual keyword
1457 // in 2015 code denoting its 2018 meaning, and we
1458 // do not want rustfix to inject bugs into working
1459 // code by rewriting such occurrences.
1461 // But if we see `dyn` outside of a macro, we know
1462 // its precise role in the parsed AST and thus are
1463 // assured this is truly an attempt to use it as
1465 kw::Dyn if !under_macro => Edition::Edition2018,
1471 // There are no new keywords yet for the 2018 edition and beyond.
1475 // Don't lint `r#foo`.
1476 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1480 let mut lint = cx.struct_span_lint(
1483 &format!("`{}` is a keyword in the {} edition", ident, next_edition),
1485 lint.span_suggestion(
1487 "you can use a raw identifier to stay compatible",
1488 format!("r#{}", ident),
1489 Applicability::MachineApplicable,
1495 impl EarlyLintPass for KeywordIdents {
1496 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1497 self.check_tokens(cx, mac_def.body.inner_tokens());
1499 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1500 self.check_tokens(cx, mac.args.inner_tokens());
1502 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1503 self.check_ident_token(cx, UnderMacro(false), ident);
1507 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1509 impl ExplicitOutlivesRequirements {
1510 fn lifetimes_outliving_lifetime<'tcx>(
1511 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1513 ) -> Vec<ty::Region<'tcx>> {
1516 .filter_map(|(pred, _)| match pred {
1517 ty::Predicate::RegionOutlives(outlives) => {
1518 let outlives = outlives.skip_binder();
1520 ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1529 fn lifetimes_outliving_type<'tcx>(
1530 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1532 ) -> Vec<ty::Region<'tcx>> {
1535 .filter_map(|(pred, _)| match pred {
1536 ty::Predicate::TypeOutlives(outlives) => {
1537 let outlives = outlives.skip_binder();
1538 outlives.0.is_param(index).then_some(outlives.1)
1545 fn collect_outlived_lifetimes<'tcx>(
1547 param: &'tcx hir::GenericParam<'tcx>,
1549 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1550 ty_generics: &'tcx ty::Generics,
1551 ) -> Vec<ty::Region<'tcx>> {
1552 let index = ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id)];
1555 hir::GenericParamKind::Lifetime { .. } => {
1556 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1558 hir::GenericParamKind::Type { .. } => {
1559 Self::lifetimes_outliving_type(inferred_outlives, index)
1561 hir::GenericParamKind::Const { .. } => Vec::new(),
1565 fn collect_outlives_bound_spans<'tcx>(
1568 bounds: &hir::GenericBounds<'_>,
1569 inferred_outlives: &[ty::Region<'tcx>],
1571 ) -> Vec<(usize, Span)> {
1572 use rustc::middle::resolve_lifetime::Region;
1577 .filter_map(|(i, bound)| {
1578 if let hir::GenericBound::Outlives(lifetime) = bound {
1579 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1580 Some(Region::Static) if infer_static => inferred_outlives
1582 .any(|r| if let ty::ReStatic = r { true } else { false }),
1583 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1584 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1588 is_inferred.then_some((i, bound.span()))
1596 fn consolidate_outlives_bound_spans(
1599 bounds: &hir::GenericBounds<'_>,
1600 bound_spans: Vec<(usize, Span)>,
1602 if bounds.is_empty() {
1605 if bound_spans.len() == bounds.len() {
1606 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1607 // If all bounds are inferable, we want to delete the colon, so
1608 // start from just after the parameter (span passed as argument)
1609 vec![lo.to(last_bound_span)]
1611 let mut merged = Vec::new();
1612 let mut last_merged_i = None;
1614 let mut from_start = true;
1615 for (i, bound_span) in bound_spans {
1616 match last_merged_i {
1617 // If the first bound is inferable, our span should also eat the leading `+`.
1619 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1620 last_merged_i = Some(0);
1622 // If consecutive bounds are inferable, merge their spans
1623 Some(h) if i == h + 1 => {
1624 if let Some(tail) = merged.last_mut() {
1625 // Also eat the trailing `+` if the first
1626 // more-than-one bound is inferable
1627 let to_span = if from_start && i < bounds.len() {
1628 bounds[i + 1].span().shrink_to_lo()
1632 *tail = tail.to(to_span);
1633 last_merged_i = Some(i);
1635 bug!("another bound-span visited earlier");
1639 // When we find a non-inferable bound, subsequent inferable bounds
1640 // won't be consecutive from the start (and we'll eat the leading
1641 // `+` rather than the trailing one)
1643 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1644 last_merged_i = Some(i);
1653 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1654 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1655 use rustc::middle::resolve_lifetime::Region;
1657 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1658 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1659 if let hir::ItemKind::Struct(_, ref hir_generics)
1660 | hir::ItemKind::Enum(_, ref hir_generics)
1661 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1663 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1664 if inferred_outlives.is_empty() {
1668 let ty_generics = cx.tcx.generics_of(def_id);
1670 let mut bound_count = 0;
1671 let mut lint_spans = Vec::new();
1673 for param in hir_generics.params {
1674 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1675 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1677 if !has_lifetime_bounds {
1681 let relevant_lifetimes =
1682 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1683 if relevant_lifetimes.is_empty() {
1687 let bound_spans = self.collect_outlives_bound_spans(
1690 &relevant_lifetimes,
1693 bound_count += bound_spans.len();
1694 lint_spans.extend(self.consolidate_outlives_bound_spans(
1695 param.span.shrink_to_hi(),
1701 let mut where_lint_spans = Vec::new();
1702 let mut dropped_predicate_count = 0;
1703 let num_predicates = hir_generics.where_clause.predicates.len();
1704 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1705 let (relevant_lifetimes, bounds, span) = match where_predicate {
1706 hir::WherePredicate::RegionPredicate(predicate) => {
1707 if let Some(Region::EarlyBound(index, ..)) =
1708 cx.tcx.named_region(predicate.lifetime.hir_id)
1711 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1719 hir::WherePredicate::BoundPredicate(predicate) => {
1720 // FIXME we can also infer bounds on associated types,
1721 // and should check for them here.
1722 match predicate.bounded_ty.kind {
1723 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1724 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1725 let index = ty_generics.param_def_id_to_index[&def_id];
1727 Self::lifetimes_outliving_type(inferred_outlives, index),
1742 if relevant_lifetimes.is_empty() {
1746 let bound_spans = self.collect_outlives_bound_spans(
1749 &relevant_lifetimes,
1752 bound_count += bound_spans.len();
1754 let drop_predicate = bound_spans.len() == bounds.len();
1756 dropped_predicate_count += 1;
1759 // If all the bounds on a predicate were inferable and there are
1760 // further predicates, we want to eat the trailing comma.
1761 if drop_predicate && i + 1 < num_predicates {
1762 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1763 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1765 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1766 span.shrink_to_lo(),
1773 // If all predicates are inferable, drop the entire clause
1774 // (including the `where`)
1775 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1776 let where_span = hir_generics
1779 .expect("span of (nonempty) where clause should exist");
1780 // Extend the where clause back to the closing `>` of the
1781 // generics, except for tuple struct, which have the `where`
1782 // after the fields of the struct.
1783 let full_where_span =
1784 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1787 hir_generics.span.shrink_to_hi().to(where_span)
1789 lint_spans.push(full_where_span);
1791 lint_spans.extend(where_lint_spans);
1794 if !lint_spans.is_empty() {
1795 let mut err = cx.struct_span_lint(
1796 EXPLICIT_OUTLIVES_REQUIREMENTS,
1798 "outlives requirements can be inferred",
1800 err.multipart_suggestion(
1801 if bound_count == 1 { "remove this bound" } else { "remove these bounds" },
1802 lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1803 Applicability::MachineApplicable,
1812 pub INCOMPLETE_FEATURES,
1814 "incomplete features that may function improperly in some or all cases"
1818 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `feature_gate.rs`.
1819 IncompleteFeatures => [INCOMPLETE_FEATURES]
1822 impl EarlyLintPass for IncompleteFeatures {
1823 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1824 let features = cx.sess.features_untracked();
1826 .declared_lang_features
1828 .map(|(name, span, _)| (name, span))
1829 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1830 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1831 .for_each(|(name, &span)| {
1832 cx.struct_span_lint(
1833 INCOMPLETE_FEATURES,
1836 "the feature `{}` is incomplete and may cause the compiler to crash",
1848 "an invalid value is being created (such as a NULL reference)"
1851 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1853 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1854 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1855 #[derive(Debug, Copy, Clone, PartialEq)]
1861 /// Information about why a type cannot be initialized this way.
1862 /// Contains an error message and optionally a span to point at.
1863 type InitError = (String, Option<Span>);
1865 /// Test if this constant is all-0.
1866 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1867 use hir::ExprKind::*;
1868 use syntax::ast::LitKind::*;
1871 if let Int(i, _) = lit.node {
1877 Tup(tup) => tup.iter().all(is_zero),
1882 /// Determine if this expression is a "dangerous initialization".
1883 fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1884 // `transmute` is inside an anonymous module (the `extern` block?);
1885 // `Invalid` represents the empty string and matches that.
1886 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1887 // on intrinsics right now.
1888 const TRANSMUTE_PATH: &[Symbol] =
1889 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1891 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1892 // Find calls to `mem::{uninitialized,zeroed}` methods.
1893 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1894 let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1896 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1897 return Some(InitKind::Zeroed);
1898 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1899 return Some(InitKind::Uninit);
1900 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1901 if is_zero(&args[0]) {
1902 return Some(InitKind::Zeroed);
1906 } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
1907 // Find problematic calls to `MaybeUninit::assume_init`.
1908 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1909 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1910 // This is a call to *some* method named `assume_init`.
1911 // See if the `self` parameter is one of the dangerous constructors.
1912 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1913 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1915 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1917 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1918 return Some(InitKind::Zeroed);
1919 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1920 return Some(InitKind::Uninit);
1930 /// Return `Some` only if we are sure this type does *not*
1931 /// allow zero initialization.
1932 fn ty_find_init_error<'tcx>(
1936 ) -> Option<InitError> {
1937 use rustc::ty::TyKind::*;
1939 // Primitive types that don't like 0 as a value.
1940 Ref(..) => Some((format!("References must be non-null"), None)),
1941 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
1942 FnPtr(..) => Some((format!("Function pointers must be non-null"), None)),
1943 Never => Some((format!("The never type (`!`) has no valid value"), None)),
1944 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1945 // raw ptr to dyn Trait
1947 Some((format!("The vtable of a wide raw pointer must be non-null"), None))
1949 // Primitive types with other constraints.
1950 Bool if init == InitKind::Uninit => {
1951 Some((format!("Booleans must be `true` or `false`"), None))
1953 Char if init == InitKind::Uninit => {
1954 Some((format!("Characters must be a valid unicode codepoint"), None))
1956 // Recurse and checks for some compound types.
1957 Adt(adt_def, substs) if !adt_def.is_union() => {
1958 // First check f this ADT has a layout attribute (like `NonNull` and friends).
1959 use std::ops::Bound;
1960 match tcx.layout_scalar_valid_range(adt_def.did) {
1961 // We exploit here that `layout_scalar_valid_range` will never
1962 // return `Bound::Excluded`. (And we have tests checking that we
1963 // handle the attribute correctly.)
1964 (Bound::Included(lo), _) if lo > 0 => {
1965 return Some((format!("{} must be non-null", ty), None));
1967 (Bound::Included(_), _) | (_, Bound::Included(_))
1968 if init == InitKind::Uninit =>
1971 format!("{} must be initialized inside its custom valid range", ty),
1978 match adt_def.variants.len() {
1979 0 => Some((format!("0-variant enums have no valid value"), None)),
1981 // Struct, or enum with exactly one variant.
1982 // Proceed recursively, check all fields.
1983 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1984 variant.fields.iter().find_map(|field| {
1985 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1988 // Point to this field, should be helpful for figuring
1989 // out where the source of the error is.
1990 let span = tcx.def_span(field.did);
1993 " (in this {} field)",
2006 // Multi-variant enums are tricky: if all but one variant are
2007 // uninhabited, we might actually do layout like for a single-variant
2008 // enum, and then even leaving them uninitialized could be okay.
2009 _ => None, // Conservative fallback for multi-variant enum.
2013 // Proceed recursively, check all fields.
2014 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2016 // Conservative fallback.
2021 if let Some(init) = is_dangerous_init(cx, expr) {
2022 // This conjures an instance of a type out of nothing,
2023 // using zeroed or uninitialized memory.
2024 // We are extremely conservative with what we warn about.
2025 let conjured_ty = cx.tables.expr_ty(expr);
2026 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2027 let mut err = cx.struct_span_lint(
2031 "the type `{}` does not permit {}",
2034 InitKind::Zeroed => "zero-initialization",
2035 InitKind::Uninit => "being left uninitialized",
2039 err.span_label(expr.span, "this code causes undefined behavior when executed");
2042 "help: use `MaybeUninit<T>` instead, \
2043 and only call `assume_init` after initialization is done",
2045 if let Some(span) = span {
2046 err.span_note(span, &msg);