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};
29 use rustc::lint::FutureIncompatibleInfo;
30 use rustc::ty::{self, layout::VariantIdx, Ty, TyCtxt};
31 use rustc_data_structures::fx::FxHashSet;
32 use rustc_feature::Stability;
33 use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
35 use rustc_hir::def::{DefKind, Res};
36 use rustc_hir::def_id::DefId;
37 use rustc_hir::{GenericParamKind, PatKind};
38 use rustc_hir::{HirIdSet, Node};
39 use rustc_span::edition::Edition;
40 use rustc_span::source_map::Spanned;
41 use rustc_span::symbol::{kw, sym, Symbol};
42 use rustc_span::{BytePos, Span};
43 use syntax::ast::{self, Expr};
44 use syntax::attr::{self, HasAttrs};
45 use syntax::errors::{Applicability, DiagnosticBuilder};
46 use syntax::print::pprust::{self, expr_to_string};
48 use syntax::tokenstream::{TokenStream, TokenTree};
49 use syntax::visit::FnKind;
51 use crate::nonstandard_style::{method_context, MethodLateContext};
55 // hardwired lints from librustc
56 pub use lint::builtin::*;
61 "suggest using `loop { }` instead of `while true { }`"
64 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
66 /// Traverse through any amount of parenthesis and return the first non-parens expression.
67 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
68 while let ast::ExprKind::Paren(sub) = &expr.kind {
74 impl EarlyLintPass for WhileTrue {
75 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
76 if let ast::ExprKind::While(cond, ..) = &e.kind {
77 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
78 if let ast::LitKind::Bool(true) = lit.kind {
79 if !lit.span.from_expansion() {
80 let msg = "denote infinite loops with `loop { ... }`";
81 let condition_span = cx.sess.source_map().def_span(e.span);
82 cx.struct_span_lint(WHILE_TRUE, condition_span, msg)
83 .span_suggestion_short(
87 Applicability::MachineApplicable,
100 "use of owned (Box type) heap memory"
103 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
106 fn check_heap_type(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
107 for leaf_ty in ty.walk() {
108 if leaf_ty.is_box() {
109 let m = format!("type uses owned (Box type) pointers: {}", ty);
110 cx.span_lint(BOX_POINTERS, span, &m);
116 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
117 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
119 hir::ItemKind::Fn(..)
120 | hir::ItemKind::TyAlias(..)
121 | hir::ItemKind::Enum(..)
122 | hir::ItemKind::Struct(..)
123 | hir::ItemKind::Union(..) => {
124 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
125 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
130 // If it's a struct, we also have to check the fields' types
132 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
133 for struct_field in struct_def.fields() {
134 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
135 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
142 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
143 let ty = cx.tables.node_type(e.hir_id);
144 self.check_heap_type(cx, e.span, ty);
149 NON_SHORTHAND_FIELD_PATTERNS,
151 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
154 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
156 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
157 fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat<'_>) {
158 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
163 .expect("struct pattern type is not an ADT")
164 .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
165 for fieldpat in field_pats {
166 if fieldpat.is_shorthand {
169 if fieldpat.span.from_expansion() {
170 // Don't lint if this is a macro expansion: macro authors
171 // shouldn't have to worry about this kind of style issue
175 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
176 if cx.tcx.find_field_index(ident, &variant)
177 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables))
179 let mut err = cx.struct_span_lint(
180 NON_SHORTHAND_FIELD_PATTERNS,
182 &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,
212 "usage of `unsafe` code"
215 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
218 fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
219 // This comes from a macro that has `#[allow_internal_unsafe]`.
220 if span.allows_unsafe() {
224 cx.span_lint(UNSAFE_CODE, span, desc);
228 impl EarlyLintPass for UnsafeCode {
229 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
230 if attr.check_name(sym::allow_internal_unsafe) {
234 "`allow_internal_unsafe` allows defining \
235 macros using unsafe without triggering \
236 the `unsafe_code` lint at their call site",
241 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
242 if let ast::ExprKind::Block(ref blk, _) = e.kind {
243 // Don't warn about generated blocks; that'll just pollute the output.
244 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
245 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
250 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
252 ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
253 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
256 ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
257 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
266 cx: &EarlyContext<'_>,
273 FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
274 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
277 FnKind::Method(_, sig, ..) => {
278 if sig.header.unsafety == ast::Unsafety::Unsafe {
279 self.report_unsafe(cx, span, "implementation of an `unsafe` method")
287 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::AssocItem) {
288 if let ast::AssocItemKind::Fn(ref sig, None) = item.kind {
289 if sig.header.unsafety == ast::Unsafety::Unsafe {
290 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
299 "detects missing documentation for public members",
300 report_in_external_macro
303 pub struct MissingDoc {
304 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
305 doc_hidden_stack: Vec<bool>,
307 /// Private traits or trait items that leaked through. Don't check their methods.
308 private_traits: FxHashSet<hir::HirId>,
311 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
313 fn has_doc(attr: &ast::Attribute) -> bool {
314 if attr.is_doc_comment() {
318 if !attr.check_name(sym::doc) {
322 if attr.is_value_str() {
326 if let Some(list) = attr.meta_item_list() {
328 if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
338 pub fn new() -> MissingDoc {
339 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
342 fn doc_hidden(&self) -> bool {
343 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
346 fn check_missing_docs_attrs(
348 cx: &LateContext<'_, '_>,
349 id: Option<hir::HirId>,
350 attrs: &[ast::Attribute],
354 // If we're building a test harness, then warning about
355 // documentation is probably not really relevant right now.
356 if cx.sess().opts.test {
360 // `#[doc(hidden)]` disables missing_docs check.
361 if self.doc_hidden() {
365 // Only check publicly-visible items, using the result from the privacy pass.
366 // It's an option so the crate root can also use this function (it doesn't
368 if let Some(id) = id {
369 if !cx.access_levels.is_exported(id) {
374 let has_doc = attrs.iter().any(|a| has_doc(a));
378 cx.tcx.sess.source_map().def_span(sp),
379 &format!("missing documentation for {}", desc),
385 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
386 fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
387 let doc_hidden = self.doc_hidden()
388 || attrs.iter().any(|attr| {
389 attr.check_name(sym::doc)
390 && match attr.meta_item_list() {
392 Some(l) => attr::list_contains_name(&l, sym::hidden),
395 self.doc_hidden_stack.push(doc_hidden);
398 fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
399 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
402 fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate<'_>) {
403 self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
405 for macro_def in krate.exported_macros {
406 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
410 cx.tcx.sess.source_map().def_span(macro_def.span),
411 "missing documentation for macro",
417 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
418 let desc = match it.kind {
419 hir::ItemKind::Fn(..) => "a function",
420 hir::ItemKind::Mod(..) => "a module",
421 hir::ItemKind::Enum(..) => "an enum",
422 hir::ItemKind::Struct(..) => "a struct",
423 hir::ItemKind::Union(..) => "a union",
424 hir::ItemKind::Trait(.., trait_item_refs) => {
425 // Issue #11592: traits are always considered exported, even when private.
426 if let hir::VisibilityKind::Inherited = it.vis.node {
427 self.private_traits.insert(it.hir_id);
428 for trait_item_ref in trait_item_refs {
429 self.private_traits.insert(trait_item_ref.id.hir_id);
435 hir::ItemKind::TyAlias(..) => "a type alias",
436 hir::ItemKind::Impl(.., Some(ref trait_ref), _, impl_item_refs) => {
437 // If the trait is private, add the impl items to `private_traits` so they don't get
438 // reported for missing docs.
439 let real_trait = trait_ref.path.res.def_id();
440 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
441 match cx.tcx.hir().find(hir_id) {
442 Some(Node::Item(item)) => {
443 if let hir::VisibilityKind::Inherited = item.vis.node {
444 for impl_item_ref in impl_item_refs {
445 self.private_traits.insert(impl_item_ref.id.hir_id);
454 hir::ItemKind::Const(..) => "a constant",
455 hir::ItemKind::Static(..) => "a static",
459 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
462 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem<'_>) {
463 if self.private_traits.contains(&trait_item.hir_id) {
467 let desc = match trait_item.kind {
468 hir::TraitItemKind::Const(..) => "an associated constant",
469 hir::TraitItemKind::Method(..) => "a trait method",
470 hir::TraitItemKind::Type(..) => "an associated type",
473 self.check_missing_docs_attrs(
475 Some(trait_item.hir_id),
482 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
483 // If the method is an impl for a trait, don't doc.
484 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
488 let desc = match impl_item.kind {
489 hir::ImplItemKind::Const(..) => "an associated constant",
490 hir::ImplItemKind::Method(..) => "a method",
491 hir::ImplItemKind::TyAlias(_) => "an associated type",
492 hir::ImplItemKind::OpaqueTy(_) => "an associated `impl Trait` type",
494 self.check_missing_docs_attrs(
496 Some(impl_item.hir_id),
503 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField<'_>) {
504 if !sf.is_positional() {
505 self.check_missing_docs_attrs(cx, Some(sf.hir_id), &sf.attrs, sf.span, "a struct field")
509 fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant<'_>) {
510 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a variant");
515 pub MISSING_COPY_IMPLEMENTATIONS,
517 "detects potentially-forgotten implementations of `Copy`"
520 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
522 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
523 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
524 if !cx.access_levels.is_reachable(item.hir_id) {
527 let (def, ty) = match item.kind {
528 hir::ItemKind::Struct(_, ref ast_generics) => {
529 if !ast_generics.params.is_empty() {
532 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
533 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
535 hir::ItemKind::Union(_, ref ast_generics) => {
536 if !ast_generics.params.is_empty() {
539 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
540 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
542 hir::ItemKind::Enum(_, ref ast_generics) => {
543 if !ast_generics.params.is_empty() {
546 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
547 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
551 if def.has_dtor(cx.tcx) {
554 let param_env = ty::ParamEnv::empty();
555 if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
558 if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
560 MISSING_COPY_IMPLEMENTATIONS,
562 "type could implement `Copy`; consider adding `impl \
570 MISSING_DEBUG_IMPLEMENTATIONS,
572 "detects missing implementations of fmt::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) {
614 MISSING_DEBUG_IMPLEMENTATIONS,
616 "type does not implement `fmt::Debug`; consider adding `#[derive(Debug)]` \
617 or a manual implementation",
624 pub ANONYMOUS_PARAMETERS,
626 "detects anonymous parameters",
627 @future_incompatible = FutureIncompatibleInfo {
628 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
629 edition: Some(Edition::Edition2018),
634 /// Checks for use of anonymous parameters (RFC 1685).
635 AnonymousParameters => [ANONYMOUS_PARAMETERS]
638 impl EarlyLintPass for AnonymousParameters {
639 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
641 ast::AssocItemKind::Fn(ref sig, _) => {
642 for arg in sig.decl.inputs.iter() {
644 ast::PatKind::Ident(_, ident, None) => {
645 if ident.name == kw::Invalid {
646 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
648 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
649 (snip, Applicability::MachineApplicable)
651 ("<type>".to_owned(), Applicability::HasPlaceholders)
655 ANONYMOUS_PARAMETERS,
657 "anonymous parameters are deprecated and will be \
658 removed in the next edition.",
662 "Try naming the parameter or explicitly \
664 format!("_: {}", ty_snip),
679 /// Check for use of attributes which have been deprecated.
681 pub struct DeprecatedAttr {
682 // This is not free to compute, so we want to keep it around, rather than
683 // compute it for every attribute.
684 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
687 impl_lint_pass!(DeprecatedAttr => []);
689 impl DeprecatedAttr {
690 pub fn new() -> DeprecatedAttr {
691 DeprecatedAttr { depr_attrs: deprecated_attributes() }
695 fn lint_deprecated_attr(
696 cx: &EarlyContext<'_>,
697 attr: &ast::Attribute,
699 suggestion: Option<&str>,
701 cx.struct_span_lint(DEPRECATED, attr.span, &msg)
702 .span_suggestion_short(
704 suggestion.unwrap_or("remove this attribute"),
706 Applicability::MachineApplicable,
711 impl EarlyLintPass for DeprecatedAttr {
712 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
713 for &&(n, _, _, ref g) in &self.depr_attrs {
714 if attr.ident().map(|ident| ident.name) == Some(n) {
715 if let &AttributeGate::Gated(
716 Stability::Deprecated(link, suggestion),
723 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
724 lint_deprecated_attr(cx, attr, &msg, suggestion);
729 if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
730 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
731 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
732 lint_deprecated_attr(cx, attr, &msg, None);
738 pub UNUSED_DOC_COMMENTS,
740 "detects doc comments that aren't used by rustdoc"
743 declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
745 impl UnusedDocComment {
748 cx: &EarlyContext<'_>,
751 is_macro_expansion: bool,
752 attrs: &[ast::Attribute],
754 let mut attrs = attrs.into_iter().peekable();
756 // Accumulate a single span for sugared doc comments.
757 let mut sugared_span: Option<Span> = None;
759 while let Some(attr) = attrs.next() {
760 if attr.is_doc_comment() {
762 sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())),
766 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
770 let span = sugared_span.take().unwrap_or_else(|| attr.span);
772 if attr.is_doc_comment() || attr.check_name(sym::doc) {
773 let mut err = cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, "unused doc comment");
777 format!("rustdoc does not generate documentation for {}", node_kind),
780 if is_macro_expansion {
782 "to document an item produced by a macro, \
783 the macro must produce the documentation as part of its expansion",
793 impl EarlyLintPass for UnusedDocComment {
794 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
795 if let ast::ItemKind::Mac(..) = item.kind {
796 self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
800 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
801 let (kind, is_macro_expansion) = match stmt.kind {
802 ast::StmtKind::Local(..) => ("statements", false),
803 ast::StmtKind::Item(..) => ("inner items", false),
804 ast::StmtKind::Mac(..) => ("macro expansions", true),
805 // expressions will be reported by `check_expr`.
806 ast::StmtKind::Semi(..) | ast::StmtKind::Expr(..) => return,
809 self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.kind.attrs());
812 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
813 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
814 self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
817 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
818 self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
823 NO_MANGLE_CONST_ITEMS,
825 "const items will not have their symbols exported"
829 NO_MANGLE_GENERIC_ITEMS,
831 "generic items must be mangled"
834 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
836 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
837 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
839 hir::ItemKind::Fn(.., ref generics, _) => {
840 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
841 for param in generics.params {
843 GenericParamKind::Lifetime { .. } => {}
844 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
845 let mut err = cx.struct_span_lint(
846 NO_MANGLE_GENERIC_ITEMS,
848 "functions generic over types or consts must be mangled",
850 err.span_suggestion_short(
852 "remove this attribute",
854 // Use of `#[no_mangle]` suggests FFI intent; correct
855 // fix may be to monomorphize source by hand
856 Applicability::MaybeIncorrect,
865 hir::ItemKind::Const(..) => {
866 if attr::contains_name(&it.attrs, sym::no_mangle) {
867 // Const items do not refer to a particular location in memory, and therefore
868 // don't have anything to attach a symbol to
869 let msg = "const items should never be `#[no_mangle]`";
870 let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
872 // account for "pub const" (#45562)
877 .span_to_snippet(it.span)
878 .map(|snippet| snippet.find("const").unwrap_or(0))
879 .unwrap_or(0) as u32;
880 // `const` is 5 chars
881 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
884 "try a static value",
885 "pub static".to_owned(),
886 Applicability::MachineApplicable,
899 "mutating transmuted &mut T from &T may cause undefined behavior"
902 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
904 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
905 fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
906 use rustc_target::spec::abi::Abi::RustIntrinsic;
908 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
909 consider instead using an UnsafeCell";
910 match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind)) {
911 Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
912 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
913 cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
919 fn get_transmute_from_to<'a, 'tcx>(
920 cx: &LateContext<'a, 'tcx>,
921 expr: &hir::Expr<'_>,
922 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
923 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
924 cx.tables.qpath_res(qpath, expr.hir_id)
928 if let Res::Def(DefKind::Fn, did) = def {
929 if !def_id_is_transmute(cx, did) {
932 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
933 let from = sig.inputs().skip_binder()[0];
934 let to = *sig.output().skip_binder();
935 return Some((from, to));
940 fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
941 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
942 && cx.tcx.item_name(def_id) == sym::transmute
950 "enabling unstable features (deprecated. do not use)"
954 /// Forbids using the `#[feature(...)]` attribute
955 UnstableFeatures => [UNSTABLE_FEATURES]
958 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
959 fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
960 if attr.check_name(sym::feature) {
961 if let Some(items) = attr.meta_item_list() {
963 ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
973 "`pub` items not reachable from crate root"
977 /// Lint for items marked `pub` that aren't reachable from other crates.
978 UnreachablePub => [UNREACHABLE_PUB]
981 impl UnreachablePub {
984 cx: &LateContext<'_, '_>,
987 vis: &hir::Visibility<'_>,
991 let mut applicability = Applicability::MachineApplicable;
993 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
994 if span.from_expansion() {
995 applicability = Applicability::MaybeIncorrect;
997 let def_span = cx.tcx.sess.source_map().def_span(span);
998 let mut err = cx.struct_span_lint(
1001 &format!("unreachable `pub` {}", what),
1003 let replacement = if cx.tcx.features().crate_visibility_modifier {
1010 err.span_suggestion(
1012 "consider restricting its visibility",
1017 err.help("or consider exporting it for use by other crates");
1026 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1027 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1028 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1031 fn check_foreign_item(
1033 cx: &LateContext<'_, '_>,
1034 foreign_item: &hir::ForeignItem<'tcx>,
1039 foreign_item.hir_id,
1046 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1047 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1050 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1051 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1058 "bounds in type aliases are not enforced"
1062 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1063 /// They are relevant when using associated types, but otherwise neither checked
1064 /// at definition site nor enforced at use site.
1065 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1068 impl TypeAliasBounds {
1069 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1071 hir::QPath::TypeRelative(ref ty, _) => {
1072 // If this is a type variable, we found a `T::Assoc`.
1074 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1075 Res::Def(DefKind::TyParam, _) => true,
1081 hir::QPath::Resolved(..) => false,
1085 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1086 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1087 // bound. Let's see if this type does that.
1089 // We use a HIR visitor to walk the type.
1090 use rustc::hir::intravisit::{self, Visitor};
1091 struct WalkAssocTypes<'a, 'db> {
1092 err: &'a mut DiagnosticBuilder<'db>,
1094 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1095 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v> {
1096 intravisit::NestedVisitorMap::None
1099 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1100 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1103 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1104 associated types in type aliases",
1107 intravisit::walk_qpath(self, qpath, id, span)
1111 // Let's go for a walk!
1112 let mut visitor = WalkAssocTypes { err };
1113 visitor.visit_ty(ty);
1117 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1118 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1119 let (ty, type_alias_generics) = match item.kind {
1120 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1123 let mut suggested_changing_assoc_types = false;
1124 // There must not be a where clause
1125 if !type_alias_generics.where_clause.predicates.is_empty() {
1126 let spans: Vec<_> = type_alias_generics
1130 .map(|pred| pred.span())
1132 let mut err = cx.struct_span_lint(
1135 "where clauses are not enforced in type aliases",
1137 err.span_suggestion(
1138 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1139 "the clause will not be checked when the type alias is used, and should be removed",
1141 Applicability::MachineApplicable,
1143 if !suggested_changing_assoc_types {
1144 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1145 suggested_changing_assoc_types = true;
1149 // The parameters must not have bounds
1150 for param in type_alias_generics.params.iter() {
1151 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1152 let suggestion = spans
1155 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1156 (start.to(*sp), String::new())
1159 if !spans.is_empty() {
1160 let mut err = cx.struct_span_lint(
1163 "bounds on generic parameters are not enforced in type aliases",
1165 let msg = "the bound will not be checked when the type alias is used, \
1166 and should be removed";
1167 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1168 if !suggested_changing_assoc_types {
1169 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1170 suggested_changing_assoc_types = true;
1179 /// Lint constants that are erroneous.
1180 /// Without this lint, we might not get any diagnostic if the constant is
1181 /// unused within this crate, even though downstream crates can't use it
1182 /// without producing an error.
1183 UnusedBrokenConst => []
1186 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1187 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1188 // trigger the query once for all constants since that will already report the errors
1189 // FIXME: Use ensure here
1190 let _ = cx.tcx.const_eval_poly(def_id);
1193 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1194 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1196 hir::ItemKind::Const(_, body_id) => {
1197 check_const(cx, body_id);
1199 hir::ItemKind::Static(_, _, body_id) => {
1200 check_const(cx, body_id);
1210 "these bounds don't depend on an type parameters"
1214 /// Lint for trait and lifetime bounds that don't depend on type parameters
1215 /// which either do nothing, or stop the item from being used.
1216 TrivialConstraints => [TRIVIAL_BOUNDS]
1219 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1220 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1221 use rustc::ty::fold::TypeFoldable;
1222 use rustc::ty::Predicate::*;
1224 if cx.tcx.features().trivial_bounds {
1225 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1226 let predicates = cx.tcx.predicates_of(def_id);
1227 for &(predicate, span) in predicates.predicates {
1228 let predicate_kind_name = match predicate {
1229 Trait(..) => "Trait",
1231 RegionOutlives(..) => "Lifetime",
1233 // Ignore projections, as they can only be global
1234 // if the trait bound is global
1236 // Ignore bounds that a user can't type
1241 ConstEvaluatable(..) => continue,
1243 if predicate.is_global() {
1248 "{} bound {} does not depend on any type \
1249 or lifetime parameters",
1250 predicate_kind_name, predicate
1260 /// Does nothing as a lint pass, but registers some `Lint`s
1261 /// which are used by other parts of the compiler.
1265 NON_SHORTHAND_FIELD_PATTERNS,
1268 MISSING_COPY_IMPLEMENTATIONS,
1269 MISSING_DEBUG_IMPLEMENTATIONS,
1270 ANONYMOUS_PARAMETERS,
1271 UNUSED_DOC_COMMENTS,
1272 NO_MANGLE_CONST_ITEMS,
1273 NO_MANGLE_GENERIC_ITEMS,
1283 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1285 "`...` range patterns are deprecated"
1289 pub struct EllipsisInclusiveRangePatterns {
1290 /// If `Some(_)`, suppress all subsequent pattern
1291 /// warnings for better diagnostics.
1292 node_id: Option<ast::NodeId>,
1295 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1297 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1298 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1299 if self.node_id.is_some() {
1300 // Don't recursively warn about patterns inside range endpoints.
1304 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1306 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1307 /// corresponding to the ellipsis.
1308 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(&P<Expr>, &P<Expr>, Span)> {
1310 PatKind::Range(a, b, Spanned { span, node: RangeEnd::Included(DotDotDot), .. }) => {
1317 let (parenthesise, endpoints) = match &pat.kind {
1318 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1319 _ => (false, matches_ellipsis_pat(pat)),
1322 if let Some((start, end, join)) = endpoints {
1323 let msg = "`...` range patterns are deprecated";
1324 let suggestion = "use `..=` for an inclusive range";
1326 self.node_id = Some(pat.id);
1327 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1328 err.span_suggestion(
1331 format!("&({}..={})", expr_to_string(&start), expr_to_string(&end)),
1332 Applicability::MachineApplicable,
1336 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1337 err.span_suggestion_short(
1341 Applicability::MachineApplicable,
1348 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1349 if let Some(node_id) = self.node_id {
1350 if pat.id == node_id {
1358 UNNAMEABLE_TEST_ITEMS,
1360 "detects an item that cannot be named being marked as `#[test_case]`",
1361 report_in_external_macro
1364 pub struct UnnameableTestItems {
1365 boundary: hir::HirId, // HirId of the item under which things are not nameable
1366 items_nameable: bool,
1369 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1371 impl UnnameableTestItems {
1372 pub fn new() -> Self {
1373 Self { boundary: hir::DUMMY_HIR_ID, items_nameable: true }
1377 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1378 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1379 if self.items_nameable {
1380 if let hir::ItemKind::Mod(..) = it.kind {
1382 self.items_nameable = false;
1383 self.boundary = it.hir_id;
1388 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1389 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, "cannot test inner items").emit();
1393 fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1394 if !self.items_nameable && self.boundary == it.hir_id {
1395 self.items_nameable = true;
1403 "detects edition keywords being used as an identifier",
1404 @future_incompatible = FutureIncompatibleInfo {
1405 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1406 edition: Some(Edition::Edition2018),
1411 /// Check for uses of edition keywords used as an identifier.
1412 KeywordIdents => [KEYWORD_IDENTS]
1415 struct UnderMacro(bool);
1417 impl KeywordIdents {
1418 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1419 for tt in tokens.into_trees() {
1421 // Only report non-raw idents.
1422 TokenTree::Token(token) => {
1423 if let Some((ident, false)) = token.ident() {
1424 self.check_ident_token(cx, UnderMacro(true), ident);
1427 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1432 fn check_ident_token(
1434 cx: &EarlyContext<'_>,
1435 UnderMacro(under_macro): UnderMacro,
1438 let next_edition = match cx.sess.edition() {
1439 Edition::Edition2015 => {
1441 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1443 // rust-lang/rust#56327: Conservatively do not
1444 // attempt to report occurrences of `dyn` within
1445 // macro definitions or invocations, because `dyn`
1446 // can legitimately occur as a contextual keyword
1447 // in 2015 code denoting its 2018 meaning, and we
1448 // do not want rustfix to inject bugs into working
1449 // code by rewriting such occurrences.
1451 // But if we see `dyn` outside of a macro, we know
1452 // its precise role in the parsed AST and thus are
1453 // assured this is truly an attempt to use it as
1455 kw::Dyn if !under_macro => Edition::Edition2018,
1461 // There are no new keywords yet for the 2018 edition and beyond.
1465 // Don't lint `r#foo`.
1466 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1470 let mut lint = cx.struct_span_lint(
1473 &format!("`{}` is a keyword in the {} edition", ident, next_edition),
1475 lint.span_suggestion(
1477 "you can use a raw identifier to stay compatible",
1478 format!("r#{}", ident),
1479 Applicability::MachineApplicable,
1485 impl EarlyLintPass for KeywordIdents {
1486 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1487 self.check_tokens(cx, mac_def.body.inner_tokens());
1489 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1490 self.check_tokens(cx, mac.args.inner_tokens());
1492 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1493 self.check_ident_token(cx, UnderMacro(false), ident);
1497 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1499 impl ExplicitOutlivesRequirements {
1500 fn lifetimes_outliving_lifetime<'tcx>(
1501 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1503 ) -> Vec<ty::Region<'tcx>> {
1506 .filter_map(|(pred, _)| match pred {
1507 ty::Predicate::RegionOutlives(outlives) => {
1508 let outlives = outlives.skip_binder();
1510 ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1519 fn lifetimes_outliving_type<'tcx>(
1520 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1522 ) -> Vec<ty::Region<'tcx>> {
1525 .filter_map(|(pred, _)| match pred {
1526 ty::Predicate::TypeOutlives(outlives) => {
1527 let outlives = outlives.skip_binder();
1528 outlives.0.is_param(index).then_some(outlives.1)
1535 fn collect_outlived_lifetimes<'tcx>(
1537 param: &'tcx hir::GenericParam<'tcx>,
1539 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1540 ty_generics: &'tcx ty::Generics,
1541 ) -> Vec<ty::Region<'tcx>> {
1542 let index = ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id)];
1545 hir::GenericParamKind::Lifetime { .. } => {
1546 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1548 hir::GenericParamKind::Type { .. } => {
1549 Self::lifetimes_outliving_type(inferred_outlives, index)
1551 hir::GenericParamKind::Const { .. } => Vec::new(),
1555 fn collect_outlives_bound_spans<'tcx>(
1558 bounds: &hir::GenericBounds<'_>,
1559 inferred_outlives: &[ty::Region<'tcx>],
1561 ) -> Vec<(usize, Span)> {
1562 use rustc::middle::resolve_lifetime::Region;
1567 .filter_map(|(i, bound)| {
1568 if let hir::GenericBound::Outlives(lifetime) = bound {
1569 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1570 Some(Region::Static) if infer_static => inferred_outlives
1572 .any(|r| if let ty::ReStatic = r { true } else { false }),
1573 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1574 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1578 is_inferred.then_some((i, bound.span()))
1586 fn consolidate_outlives_bound_spans(
1589 bounds: &hir::GenericBounds<'_>,
1590 bound_spans: Vec<(usize, Span)>,
1592 if bounds.is_empty() {
1595 if bound_spans.len() == bounds.len() {
1596 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1597 // If all bounds are inferable, we want to delete the colon, so
1598 // start from just after the parameter (span passed as argument)
1599 vec![lo.to(last_bound_span)]
1601 let mut merged = Vec::new();
1602 let mut last_merged_i = None;
1604 let mut from_start = true;
1605 for (i, bound_span) in bound_spans {
1606 match last_merged_i {
1607 // If the first bound is inferable, our span should also eat the leading `+`.
1609 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1610 last_merged_i = Some(0);
1612 // If consecutive bounds are inferable, merge their spans
1613 Some(h) if i == h + 1 => {
1614 if let Some(tail) = merged.last_mut() {
1615 // Also eat the trailing `+` if the first
1616 // more-than-one bound is inferable
1617 let to_span = if from_start && i < bounds.len() {
1618 bounds[i + 1].span().shrink_to_lo()
1622 *tail = tail.to(to_span);
1623 last_merged_i = Some(i);
1625 bug!("another bound-span visited earlier");
1629 // When we find a non-inferable bound, subsequent inferable bounds
1630 // won't be consecutive from the start (and we'll eat the leading
1631 // `+` rather than the trailing one)
1633 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1634 last_merged_i = Some(i);
1643 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1644 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1645 use rustc::middle::resolve_lifetime::Region;
1647 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1648 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1649 if let hir::ItemKind::Struct(_, ref hir_generics)
1650 | hir::ItemKind::Enum(_, ref hir_generics)
1651 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1653 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1654 if inferred_outlives.is_empty() {
1658 let ty_generics = cx.tcx.generics_of(def_id);
1660 let mut bound_count = 0;
1661 let mut lint_spans = Vec::new();
1663 for param in hir_generics.params {
1664 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1665 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1667 if !has_lifetime_bounds {
1671 let relevant_lifetimes =
1672 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1673 if relevant_lifetimes.is_empty() {
1677 let bound_spans = self.collect_outlives_bound_spans(
1680 &relevant_lifetimes,
1683 bound_count += bound_spans.len();
1684 lint_spans.extend(self.consolidate_outlives_bound_spans(
1685 param.span.shrink_to_hi(),
1691 let mut where_lint_spans = Vec::new();
1692 let mut dropped_predicate_count = 0;
1693 let num_predicates = hir_generics.where_clause.predicates.len();
1694 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1695 let (relevant_lifetimes, bounds, span) = match where_predicate {
1696 hir::WherePredicate::RegionPredicate(predicate) => {
1697 if let Some(Region::EarlyBound(index, ..)) =
1698 cx.tcx.named_region(predicate.lifetime.hir_id)
1701 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1709 hir::WherePredicate::BoundPredicate(predicate) => {
1710 // FIXME we can also infer bounds on associated types,
1711 // and should check for them here.
1712 match predicate.bounded_ty.kind {
1713 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1714 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1715 let index = ty_generics.param_def_id_to_index[&def_id];
1717 Self::lifetimes_outliving_type(inferred_outlives, index),
1732 if relevant_lifetimes.is_empty() {
1736 let bound_spans = self.collect_outlives_bound_spans(
1739 &relevant_lifetimes,
1742 bound_count += bound_spans.len();
1744 let drop_predicate = bound_spans.len() == bounds.len();
1746 dropped_predicate_count += 1;
1749 // If all the bounds on a predicate were inferable and there are
1750 // further predicates, we want to eat the trailing comma.
1751 if drop_predicate && i + 1 < num_predicates {
1752 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1753 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1755 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1756 span.shrink_to_lo(),
1763 // If all predicates are inferable, drop the entire clause
1764 // (including the `where`)
1765 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1766 let where_span = hir_generics
1769 .expect("span of (nonempty) where clause should exist");
1770 // Extend the where clause back to the closing `>` of the
1771 // generics, except for tuple struct, which have the `where`
1772 // after the fields of the struct.
1773 let full_where_span =
1774 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1777 hir_generics.span.shrink_to_hi().to(where_span)
1779 lint_spans.push(full_where_span);
1781 lint_spans.extend(where_lint_spans);
1784 if !lint_spans.is_empty() {
1785 let mut err = cx.struct_span_lint(
1786 EXPLICIT_OUTLIVES_REQUIREMENTS,
1788 "outlives requirements can be inferred",
1790 err.multipart_suggestion(
1791 if bound_count == 1 { "remove this bound" } else { "remove these bounds" },
1792 lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1793 Applicability::MachineApplicable,
1802 pub INCOMPLETE_FEATURES,
1804 "incomplete features that may function improperly in some or all cases"
1808 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `feature_gate.rs`.
1809 IncompleteFeatures => [INCOMPLETE_FEATURES]
1812 impl EarlyLintPass for IncompleteFeatures {
1813 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1814 let features = cx.sess.features_untracked();
1816 .declared_lang_features
1818 .map(|(name, span, _)| (name, span))
1819 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1820 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1821 .for_each(|(name, &span)| {
1822 cx.struct_span_lint(
1823 INCOMPLETE_FEATURES,
1826 "the feature `{}` is incomplete and may cause the compiler to crash",
1838 "an invalid value is being created (such as a NULL reference)"
1841 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1843 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1844 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1845 #[derive(Debug, Copy, Clone, PartialEq)]
1851 /// Information about why a type cannot be initialized this way.
1852 /// Contains an error message and optionally a span to point at.
1853 type InitError = (String, Option<Span>);
1855 /// Test if this constant is all-0.
1856 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1857 use hir::ExprKind::*;
1858 use syntax::ast::LitKind::*;
1861 if let Int(i, _) = lit.node {
1867 Tup(tup) => tup.iter().all(is_zero),
1872 /// Determine if this expression is a "dangerous initialization".
1873 fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1874 // `transmute` is inside an anonymous module (the `extern` block?);
1875 // `Invalid` represents the empty string and matches that.
1876 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1877 // on intrinsics right now.
1878 const TRANSMUTE_PATH: &[Symbol] =
1879 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1881 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1882 // Find calls to `mem::{uninitialized,zeroed}` methods.
1883 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1884 let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1886 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1887 return Some(InitKind::Zeroed);
1888 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1889 return Some(InitKind::Uninit);
1890 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1891 if is_zero(&args[0]) {
1892 return Some(InitKind::Zeroed);
1896 } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
1897 // Find problematic calls to `MaybeUninit::assume_init`.
1898 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1899 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1900 // This is a call to *some* method named `assume_init`.
1901 // See if the `self` parameter is one of the dangerous constructors.
1902 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1903 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1905 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1907 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1908 return Some(InitKind::Zeroed);
1909 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1910 return Some(InitKind::Uninit);
1920 /// Return `Some` only if we are sure this type does *not*
1921 /// allow zero initialization.
1922 fn ty_find_init_error<'tcx>(
1926 ) -> Option<InitError> {
1927 use rustc::ty::TyKind::*;
1929 // Primitive types that don't like 0 as a value.
1930 Ref(..) => Some((format!("References must be non-null"), None)),
1931 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
1932 FnPtr(..) => Some((format!("Function pointers must be non-null"), None)),
1933 Never => Some((format!("The never type (`!`) has no valid value"), None)),
1934 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1935 // raw ptr to dyn Trait
1937 Some((format!("The vtable of a wide raw pointer must be non-null"), None))
1939 // Primitive types with other constraints.
1940 Bool if init == InitKind::Uninit => {
1941 Some((format!("Booleans must be `true` or `false`"), None))
1943 Char if init == InitKind::Uninit => {
1944 Some((format!("Characters must be a valid unicode codepoint"), None))
1946 // Recurse and checks for some compound types.
1947 Adt(adt_def, substs) if !adt_def.is_union() => {
1948 // First check f this ADT has a layout attribute (like `NonNull` and friends).
1949 use std::ops::Bound;
1950 match tcx.layout_scalar_valid_range(adt_def.did) {
1951 // We exploit here that `layout_scalar_valid_range` will never
1952 // return `Bound::Excluded`. (And we have tests checking that we
1953 // handle the attribute correctly.)
1954 (Bound::Included(lo), _) if lo > 0 => {
1955 return Some((format!("{} must be non-null", ty), None));
1957 (Bound::Included(_), _) | (_, Bound::Included(_))
1958 if init == InitKind::Uninit =>
1961 format!("{} must be initialized inside its custom valid range", ty),
1968 match adt_def.variants.len() {
1969 0 => Some((format!("0-variant enums have no valid value"), None)),
1971 // Struct, or enum with exactly one variant.
1972 // Proceed recursively, check all fields.
1973 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
1974 variant.fields.iter().find_map(|field| {
1975 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
1978 // Point to this field, should be helpful for figuring
1979 // out where the source of the error is.
1980 let span = tcx.def_span(field.did);
1983 " (in this {} field)",
1996 // Multi-variant enums are tricky: if all but one variant are
1997 // uninhabited, we might actually do layout like for a single-variant
1998 // enum, and then even leaving them uninitialized could be okay.
1999 _ => None, // Conservative fallback for multi-variant enum.
2003 // Proceed recursively, check all fields.
2004 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2006 // Conservative fallback.
2011 if let Some(init) = is_dangerous_init(cx, expr) {
2012 // This conjures an instance of a type out of nothing,
2013 // using zeroed or uninitialized memory.
2014 // We are extremely conservative with what we warn about.
2015 let conjured_ty = cx.tables.expr_ty(expr);
2016 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2017 let mut err = cx.struct_span_lint(
2021 "the type `{}` does not permit {}",
2024 InitKind::Zeroed => "zero-initialization",
2025 InitKind::Uninit => "being left uninitialized",
2029 err.span_label(expr.span, "this code causes undefined behavior when executed");
2032 "help: use `MaybeUninit<T>` instead, \
2033 and only call `assume_init` after initialization is done",
2035 if let Some(span) = span {
2036 err.span_note(span, &msg);