1 //! Lints in the Rust compiler.
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main
8 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
9 //! Then add code to emit the new lint in the appropriate circumstances.
10 //! You can do that in an existing `LintPass` if it makes sense, or in a
11 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
12 //! compiler. Only do the latter if the check can't be written cleanly as a
13 //! `LintPass` (also, note that such lints will need to be defined in
14 //! `rustc::lint::builtin`, not here).
16 //! If you define a new `EarlyLintPass`, you will also need to add it to the
17 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
18 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
19 //! with a `pub fn new()`.
21 //! If you define a new `LateLintPass`, you will also need to add it to the
22 //! `late_lint_methods!` invocation in `lib.rs`.
24 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
25 use rustc::hir::map::Map;
26 use rustc::lint::LintDiagnosticBuilder;
27 use rustc::traits::misc::can_type_implement_copy;
28 use rustc::ty::{self, layout::VariantIdx, Ty, TyCtxt};
29 use rustc_ast_pretty::pprust::{self, expr_to_string};
30 use rustc_data_structures::fx::FxHashSet;
31 use rustc_errors::{Applicability, DiagnosticBuilder};
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_session::lint::FutureIncompatibleInfo;
40 use rustc_span::edition::Edition;
41 use rustc_span::source_map::Spanned;
42 use rustc_span::symbol::{kw, sym, Symbol};
43 use rustc_span::{BytePos, Span};
44 use syntax::ast::{self, Expr};
45 use syntax::attr::{self, HasAttrs};
46 use syntax::tokenstream::{TokenStream, TokenTree};
47 use syntax::visit::{FnCtxt, FnKind};
49 use crate::nonstandard_style::{method_context, MethodLateContext};
54 // hardwired lints from librustc
55 pub use rustc_session::lint::builtin::*;
60 "suggest using `loop { }` instead of `while true { }`"
63 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
65 /// Traverse through any amount of parenthesis and return the first non-parens expression.
66 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
67 while let ast::ExprKind::Paren(sub) = &expr.kind {
73 impl EarlyLintPass for WhileTrue {
74 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
75 if let ast::ExprKind::While(cond, ..) = &e.kind {
76 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
77 if let ast::LitKind::Bool(true) = lit.kind {
78 if !lit.span.from_expansion() {
79 let msg = "denote infinite loops with `loop { ... }`";
80 let condition_span = cx.sess.source_map().def_span(e.span);
81 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
83 .span_suggestion_short(
87 Applicability::MachineApplicable,
101 "use of owned (Box type) heap memory"
104 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
107 fn check_heap_type(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
108 for leaf_ty in ty.walk() {
109 if leaf_ty.is_box() {
110 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
111 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
118 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
119 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
121 hir::ItemKind::Fn(..)
122 | hir::ItemKind::TyAlias(..)
123 | hir::ItemKind::Enum(..)
124 | hir::ItemKind::Struct(..)
125 | hir::ItemKind::Union(..) => {
126 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
127 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
132 // If it's a struct, we also have to check the fields' types
134 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
135 for struct_field in struct_def.fields() {
136 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
137 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
144 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
145 let ty = cx.tables.node_type(e.hir_id);
146 self.check_heap_type(cx, e.span, ty);
151 NON_SHORTHAND_FIELD_PATTERNS,
153 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
156 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
158 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
159 fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat<'_>) {
160 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
165 .expect("struct pattern type is not an ADT")
166 .variant_of_res(cx.tables.qpath_res(qpath, pat.hir_id));
167 for fieldpat in field_pats {
168 if fieldpat.is_shorthand {
171 if fieldpat.span.from_expansion() {
172 // Don't lint if this is a macro expansion: macro authors
173 // shouldn't have to worry about this kind of style issue
177 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
178 if cx.tcx.find_field_index(ident, &variant)
179 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.tables))
181 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
183 .build(&format!("the `{}:` in this pattern is redundant", ident));
184 let binding = match binding_annot {
185 hir::BindingAnnotation::Unannotated => None,
186 hir::BindingAnnotation::Mutable => Some("mut"),
187 hir::BindingAnnotation::Ref => Some("ref"),
188 hir::BindingAnnotation::RefMut => Some("ref mut"),
190 let ident = if let Some(binding) = binding {
191 format!("{} {}", binding, ident)
197 "use shorthand field pattern",
199 Applicability::MachineApplicable,
213 "usage of `unsafe` code"
216 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
221 cx: &EarlyContext<'_>,
223 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
225 // This comes from a macro that has `#[allow_internal_unsafe]`.
226 if span.allows_unsafe() {
230 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
234 impl EarlyLintPass for UnsafeCode {
235 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
236 if attr.check_name(sym::allow_internal_unsafe) {
237 self.report_unsafe(cx, attr.span, |lint| {
239 "`allow_internal_unsafe` allows defining \
240 macros using unsafe without triggering \
241 the `unsafe_code` lint at their call site",
248 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
249 if let ast::ExprKind::Block(ref blk, _) = e.kind {
250 // Don't warn about generated blocks; that'll just pollute the output.
251 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
252 self.report_unsafe(cx, blk.span, |lint| {
253 lint.build("usage of an `unsafe` block").emit()
259 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
261 ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
262 self.report_unsafe(cx, it.span, |lint| {
263 lint.build("declaration of an `unsafe` trait").emit()
267 ast::ItemKind::Impl { unsafety: ast::Unsafety::Unsafe, .. } => {
268 self.report_unsafe(cx, it.span, |lint| {
269 lint.build("implementation of an `unsafe` trait").emit()
277 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
281 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, .. },
286 let msg = match ctxt {
287 FnCtxt::Foreign => return,
288 FnCtxt::Free => "declaration of an `unsafe` function",
289 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
290 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
292 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
300 "detects missing documentation for public members",
301 report_in_external_macro
304 pub struct MissingDoc {
305 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
306 doc_hidden_stack: Vec<bool>,
308 /// Private traits or trait items that leaked through. Don't check their methods.
309 private_traits: FxHashSet<hir::HirId>,
312 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
314 fn has_doc(attr: &ast::Attribute) -> bool {
315 if attr.is_doc_comment() {
319 if !attr.check_name(sym::doc) {
323 if attr.is_value_str() {
327 if let Some(list) = attr.meta_item_list() {
329 if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
339 pub fn new() -> MissingDoc {
340 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
343 fn doc_hidden(&self) -> bool {
344 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
347 fn check_missing_docs_attrs(
349 cx: &LateContext<'_, '_>,
350 id: Option<hir::HirId>,
351 attrs: &[ast::Attribute],
355 // If we're building a test harness, then warning about
356 // documentation is probably not really relevant right now.
357 if cx.sess().opts.test {
361 // `#[doc(hidden)]` disables missing_docs check.
362 if self.doc_hidden() {
366 // Only check publicly-visible items, using the result from the privacy pass.
367 // It's an option so the crate root can also use this function (it doesn't
369 if let Some(id) = id {
370 if !cx.access_levels.is_exported(id) {
375 let has_doc = attrs.iter().any(|a| has_doc(a));
377 cx.struct_span_lint(MISSING_DOCS, cx.tcx.sess.source_map().def_span(sp), |lint| {
378 lint.build(&format!("missing documentation for {}", desc)).emit()
384 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
385 fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
386 let doc_hidden = self.doc_hidden()
387 || attrs.iter().any(|attr| {
388 attr.check_name(sym::doc)
389 && match attr.meta_item_list() {
391 Some(l) => attr::list_contains_name(&l, sym::hidden),
394 self.doc_hidden_stack.push(doc_hidden);
397 fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
398 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
401 fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate<'_>) {
402 self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
404 for macro_def in krate.exported_macros {
405 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
409 cx.tcx.sess.source_map().def_span(macro_def.span),
410 |lint| lint.build("missing documentation for macro").emit(),
416 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
417 let desc = match it.kind {
418 hir::ItemKind::Fn(..) => "a function",
419 hir::ItemKind::Mod(..) => "a module",
420 hir::ItemKind::Enum(..) => "an enum",
421 hir::ItemKind::Struct(..) => "a struct",
422 hir::ItemKind::Union(..) => "a union",
423 hir::ItemKind::Trait(.., trait_item_refs) => {
424 // Issue #11592: traits are always considered exported, even when private.
425 if let hir::VisibilityKind::Inherited = it.vis.node {
426 self.private_traits.insert(it.hir_id);
427 for trait_item_ref in trait_item_refs {
428 self.private_traits.insert(trait_item_ref.id.hir_id);
434 hir::ItemKind::TyAlias(..) => "a type alias",
435 hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
436 // If the trait is private, add the impl items to `private_traits` so they don't get
437 // reported for missing docs.
438 let real_trait = trait_ref.path.res.def_id();
439 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
440 match cx.tcx.hir().find(hir_id) {
441 Some(Node::Item(item)) => {
442 if let hir::VisibilityKind::Inherited = item.vis.node {
443 for impl_item_ref in items {
444 self.private_traits.insert(impl_item_ref.id.hir_id);
453 hir::ItemKind::Const(..) => "a constant",
454 hir::ItemKind::Static(..) => "a static",
458 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
461 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem<'_>) {
462 if self.private_traits.contains(&trait_item.hir_id) {
466 let desc = match trait_item.kind {
467 hir::TraitItemKind::Const(..) => "an associated constant",
468 hir::TraitItemKind::Method(..) => "a trait method",
469 hir::TraitItemKind::Type(..) => "an associated type",
472 self.check_missing_docs_attrs(
474 Some(trait_item.hir_id),
481 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
482 // If the method is an impl for a trait, don't doc.
483 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
487 let desc = match impl_item.kind {
488 hir::ImplItemKind::Const(..) => "an associated constant",
489 hir::ImplItemKind::Method(..) => "a method",
490 hir::ImplItemKind::TyAlias(_) => "an associated type",
491 hir::ImplItemKind::OpaqueTy(_) => "an associated `impl Trait` type",
493 self.check_missing_docs_attrs(
495 Some(impl_item.hir_id),
502 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField<'_>) {
503 if !sf.is_positional() {
504 self.check_missing_docs_attrs(cx, Some(sf.hir_id), &sf.attrs, sf.span, "a struct field")
508 fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant<'_>) {
509 self.check_missing_docs_attrs(cx, Some(v.id), &v.attrs, v.span, "a variant");
514 pub MISSING_COPY_IMPLEMENTATIONS,
516 "detects potentially-forgotten implementations of `Copy`"
519 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
521 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
522 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
523 if !cx.access_levels.is_reachable(item.hir_id) {
526 let (def, ty) = match item.kind {
527 hir::ItemKind::Struct(_, ref ast_generics) => {
528 if !ast_generics.params.is_empty() {
531 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
532 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
534 hir::ItemKind::Union(_, ref ast_generics) => {
535 if !ast_generics.params.is_empty() {
538 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
539 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
541 hir::ItemKind::Enum(_, ref ast_generics) => {
542 if !ast_generics.params.is_empty() {
545 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
546 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
550 if def.has_dtor(cx.tcx) {
553 let param_env = ty::ParamEnv::empty();
554 if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
557 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
558 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
560 "type could implement `Copy`; consider adding `impl \
570 MISSING_DEBUG_IMPLEMENTATIONS,
572 "detects missing implementations of Debug"
576 pub struct MissingDebugImplementations {
577 impling_types: Option<HirIdSet>,
580 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
582 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
583 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
584 if !cx.access_levels.is_reachable(item.hir_id) {
589 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
593 let debug = match cx.tcx.get_diagnostic_item(sym::debug_trait) {
594 Some(debug) => debug,
598 if self.impling_types.is_none() {
599 let mut impls = HirIdSet::default();
600 cx.tcx.for_each_impl(debug, |d| {
601 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
602 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
603 impls.insert(hir_id);
608 self.impling_types = Some(impls);
609 debug!("{:?}", self.impling_types);
612 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
613 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
615 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
616 or a manual implementation",
617 cx.tcx.def_path_str(debug)
626 pub ANONYMOUS_PARAMETERS,
628 "detects anonymous parameters",
629 @future_incompatible = FutureIncompatibleInfo {
630 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
631 edition: Some(Edition::Edition2018),
636 /// Checks for use of anonymous parameters (RFC 1685).
637 AnonymousParameters => [ANONYMOUS_PARAMETERS]
640 impl EarlyLintPass for AnonymousParameters {
641 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
643 ast::AssocItemKind::Fn(ref sig, _) => {
644 for arg in sig.decl.inputs.iter() {
646 ast::PatKind::Ident(_, ident, None) => {
647 if ident.name == kw::Invalid {
648 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
649 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
651 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
652 (snip.as_str(), Applicability::MachineApplicable)
654 ("<type>", Applicability::HasPlaceholders)
658 "anonymous parameters are deprecated and will be \
659 removed in the next edition.",
663 "try naming the parameter or explicitly \
665 format!("_: {}", ty_snip),
681 /// Check for use of attributes which have been deprecated.
683 pub struct DeprecatedAttr {
684 // This is not free to compute, so we want to keep it around, rather than
685 // compute it for every attribute.
686 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
689 impl_lint_pass!(DeprecatedAttr => []);
691 impl DeprecatedAttr {
692 pub fn new() -> DeprecatedAttr {
693 DeprecatedAttr { depr_attrs: deprecated_attributes() }
697 fn lint_deprecated_attr(
698 cx: &EarlyContext<'_>,
699 attr: &ast::Attribute,
701 suggestion: Option<&str>,
703 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
705 .span_suggestion_short(
707 suggestion.unwrap_or("remove this attribute"),
709 Applicability::MachineApplicable,
715 impl EarlyLintPass for DeprecatedAttr {
716 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
717 for &&(n, _, _, ref g) in &self.depr_attrs {
718 if attr.ident().map(|ident| ident.name) == Some(n) {
719 if let &AttributeGate::Gated(
720 Stability::Deprecated(link, suggestion),
727 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
728 lint_deprecated_attr(cx, attr, &msg, suggestion);
733 if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
734 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
735 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
736 lint_deprecated_attr(cx, attr, &msg, None);
742 pub UNUSED_DOC_COMMENTS,
744 "detects doc comments that aren't used by rustdoc"
747 declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
749 impl UnusedDocComment {
752 cx: &EarlyContext<'_>,
755 is_macro_expansion: bool,
756 attrs: &[ast::Attribute],
758 let mut attrs = attrs.into_iter().peekable();
760 // Accumulate a single span for sugared doc comments.
761 let mut sugared_span: Option<Span> = None;
763 while let Some(attr) = attrs.next() {
764 if attr.is_doc_comment() {
766 sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())),
770 if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {
774 let span = sugared_span.take().unwrap_or_else(|| attr.span);
776 if attr.is_doc_comment() || attr.check_name(sym::doc) {
777 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
778 let mut err = lint.build("unused doc comment");
781 format!("rustdoc does not generate documentation for {}", node_kind),
783 if is_macro_expansion {
785 "to document an item produced by a macro, \
786 the macro must produce the documentation as part of its expansion",
796 impl EarlyLintPass for UnusedDocComment {
797 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
798 if let ast::ItemKind::Mac(..) = item.kind {
799 self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
803 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
804 let (kind, is_macro_expansion) = match stmt.kind {
805 ast::StmtKind::Local(..) => ("statements", false),
806 ast::StmtKind::Item(..) => ("inner items", false),
807 ast::StmtKind::Mac(..) => ("macro expansions", true),
808 // expressions will be reported by `check_expr`.
809 ast::StmtKind::Semi(..) | ast::StmtKind::Expr(..) => return,
812 self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.kind.attrs());
815 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
816 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
817 self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
820 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
821 self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
826 NO_MANGLE_CONST_ITEMS,
828 "const items will not have their symbols exported"
832 NO_MANGLE_GENERIC_ITEMS,
834 "generic items must be mangled"
837 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
839 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
840 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
842 hir::ItemKind::Fn(.., ref generics, _) => {
843 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
844 for param in generics.params {
846 GenericParamKind::Lifetime { .. } => {}
847 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
848 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, it.span, |lint| {
850 "functions generic over types or consts must be mangled",
852 .span_suggestion_short(
854 "remove this attribute",
856 // Use of `#[no_mangle]` suggests FFI intent; correct
857 // fix may be to monomorphize source by hand
858 Applicability::MaybeIncorrect,
868 hir::ItemKind::Const(..) => {
869 if attr::contains_name(&it.attrs, sym::no_mangle) {
870 // Const items do not refer to a particular location in memory, and therefore
871 // don't have anything to attach a symbol to
872 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
873 let msg = "const items should never be `#[no_mangle]`";
874 let mut err = lint.build(msg);
876 // account for "pub const" (#45562)
881 .span_to_snippet(it.span)
882 .map(|snippet| snippet.find("const").unwrap_or(0))
883 .unwrap_or(0) as u32;
884 // `const` is 5 chars
885 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
888 "try a static value",
889 "pub static".to_owned(),
890 Applicability::MachineApplicable,
904 "mutating transmuted &mut T from &T may cause undefined behavior"
907 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
909 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
910 fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
911 use rustc_target::spec::abi::Abi::RustIntrinsic;
913 match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.kind, &ty2.kind)) {
914 Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
915 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
916 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
917 consider instead using an UnsafeCell";
918 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
919 lint.build(msg).emit()
926 fn get_transmute_from_to<'a, 'tcx>(
927 cx: &LateContext<'a, 'tcx>,
928 expr: &hir::Expr<'_>,
929 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
930 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
931 cx.tables.qpath_res(qpath, expr.hir_id)
935 if let Res::Def(DefKind::Fn, did) = def {
936 if !def_id_is_transmute(cx, did) {
939 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
940 let from = sig.inputs().skip_binder()[0];
941 let to = *sig.output().skip_binder();
942 return Some((from, to));
947 fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
948 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
949 && cx.tcx.item_name(def_id) == sym::transmute
957 "enabling unstable features (deprecated. do not use)"
961 /// Forbids using the `#[feature(...)]` attribute
962 UnstableFeatures => [UNSTABLE_FEATURES]
965 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
966 fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
967 if attr.check_name(sym::feature) {
968 if let Some(items) = attr.meta_item_list() {
970 ctx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
971 lint.build("unstable feature").emit()
982 "`pub` items not reachable from crate root"
986 /// Lint for items marked `pub` that aren't reachable from other crates.
987 UnreachablePub => [UNREACHABLE_PUB]
990 impl UnreachablePub {
993 cx: &LateContext<'_, '_>,
996 vis: &hir::Visibility<'_>,
1000 let mut applicability = Applicability::MachineApplicable;
1002 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1003 if span.from_expansion() {
1004 applicability = Applicability::MaybeIncorrect;
1006 let def_span = cx.tcx.sess.source_map().def_span(span);
1007 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1008 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1009 let replacement = if cx.tcx.features().crate_visibility_modifier {
1016 err.span_suggestion(
1018 "consider restricting its visibility",
1023 err.help("or consider exporting it for use by other crates");
1033 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1034 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1035 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1038 fn check_foreign_item(
1040 cx: &LateContext<'_, '_>,
1041 foreign_item: &hir::ForeignItem<'tcx>,
1046 foreign_item.hir_id,
1053 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
1054 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1057 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem<'_>) {
1058 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1065 "bounds in type aliases are not enforced"
1069 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1070 /// They are relevant when using associated types, but otherwise neither checked
1071 /// at definition site nor enforced at use site.
1072 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1075 impl TypeAliasBounds {
1076 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1078 hir::QPath::TypeRelative(ref ty, _) => {
1079 // If this is a type variable, we found a `T::Assoc`.
1081 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => match path.res {
1082 Res::Def(DefKind::TyParam, _) => true,
1088 hir::QPath::Resolved(..) => false,
1092 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1093 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1094 // bound. Let's see if this type does that.
1096 // We use a HIR visitor to walk the type.
1097 use rustc_hir::intravisit::{self, Visitor};
1098 struct WalkAssocTypes<'a, 'db> {
1099 err: &'a mut DiagnosticBuilder<'db>,
1101 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1104 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1105 intravisit::NestedVisitorMap::None
1108 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1109 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1112 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1113 associated types in type aliases",
1116 intravisit::walk_qpath(self, qpath, id, span)
1120 // Let's go for a walk!
1121 let mut visitor = WalkAssocTypes { err };
1122 visitor.visit_ty(ty);
1126 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1127 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item<'_>) {
1128 let (ty, type_alias_generics) = match item.kind {
1129 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1132 let mut suggested_changing_assoc_types = false;
1133 // There must not be a where clause
1134 if !type_alias_generics.where_clause.predicates.is_empty() {
1138 let mut err = lint.build("where clauses are not enforced in type aliases");
1139 let spans: Vec<_> = type_alias_generics
1143 .map(|pred| pred.span())
1145 err.set_span(spans);
1146 err.span_suggestion(
1147 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1148 "the clause will not be checked when the type alias is used, and should be removed",
1150 Applicability::MachineApplicable,
1152 if !suggested_changing_assoc_types {
1153 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1154 suggested_changing_assoc_types = true;
1160 // The parameters must not have bounds
1161 for param in type_alias_generics.params.iter() {
1162 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1163 let suggestion = spans
1166 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1167 (start.to(*sp), String::new())
1170 if !spans.is_empty() {
1171 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1173 lint.build("bounds on generic parameters are not enforced in type aliases");
1174 let msg = "the bound will not be checked when the type alias is used, \
1175 and should be removed";
1176 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1177 if !suggested_changing_assoc_types {
1178 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1179 suggested_changing_assoc_types = true;
1189 /// Lint constants that are erroneous.
1190 /// Without this lint, we might not get any diagnostic if the constant is
1191 /// unused within this crate, even though downstream crates can't use it
1192 /// without producing an error.
1193 UnusedBrokenConst => []
1196 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1197 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1198 // trigger the query once for all constants since that will already report the errors
1199 // FIXME: Use ensure here
1200 let _ = cx.tcx.const_eval_poly(def_id);
1203 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1204 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1206 hir::ItemKind::Const(_, body_id) => {
1207 check_const(cx, body_id);
1209 hir::ItemKind::Static(_, _, body_id) => {
1210 check_const(cx, body_id);
1220 "these bounds don't depend on an type parameters"
1224 /// Lint for trait and lifetime bounds that don't depend on type parameters
1225 /// which either do nothing, or stop the item from being used.
1226 TrivialConstraints => [TRIVIAL_BOUNDS]
1229 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1230 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
1231 use rustc::ty::fold::TypeFoldable;
1232 use rustc::ty::Predicate::*;
1234 if cx.tcx.features().trivial_bounds {
1235 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1236 let predicates = cx.tcx.predicates_of(def_id);
1237 for &(predicate, span) in predicates.predicates {
1238 let predicate_kind_name = match predicate {
1239 Trait(..) => "Trait",
1241 RegionOutlives(..) => "Lifetime",
1243 // Ignore projections, as they can only be global
1244 // if the trait bound is global
1246 // Ignore bounds that a user can't type
1251 ConstEvaluatable(..) => continue,
1253 if predicate.is_global() {
1254 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1255 lint.build(&format!(
1256 "{} bound {} does not depend on any type \
1257 or lifetime parameters",
1258 predicate_kind_name, predicate
1269 /// Does nothing as a lint pass, but registers some `Lint`s
1270 /// which are used by other parts of the compiler.
1274 NON_SHORTHAND_FIELD_PATTERNS,
1277 MISSING_COPY_IMPLEMENTATIONS,
1278 MISSING_DEBUG_IMPLEMENTATIONS,
1279 ANONYMOUS_PARAMETERS,
1280 UNUSED_DOC_COMMENTS,
1281 NO_MANGLE_CONST_ITEMS,
1282 NO_MANGLE_GENERIC_ITEMS,
1292 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1294 "`...` range patterns are deprecated"
1298 pub struct EllipsisInclusiveRangePatterns {
1299 /// If `Some(_)`, suppress all subsequent pattern
1300 /// warnings for better diagnostics.
1301 node_id: Option<ast::NodeId>,
1304 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1306 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1307 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1308 if self.node_id.is_some() {
1309 // Don't recursively warn about patterns inside range endpoints.
1313 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1315 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1316 /// corresponding to the ellipsis.
1317 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1322 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1323 ) => Some((a.as_deref(), b, *span)),
1328 let (parenthesise, endpoints) = match &pat.kind {
1329 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1330 _ => (false, matches_ellipsis_pat(pat)),
1333 if let Some((start, end, join)) = endpoints {
1334 let msg = "`...` range patterns are deprecated";
1335 let suggestion = "use `..=` for an inclusive range";
1337 self.node_id = Some(pat.id);
1338 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1339 let end = expr_to_string(&end);
1340 let replace = match start {
1341 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1342 None => format!("&(..={})", end),
1349 Applicability::MachineApplicable,
1354 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1356 .span_suggestion_short(
1360 Applicability::MachineApplicable,
1368 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1369 if let Some(node_id) = self.node_id {
1370 if pat.id == node_id {
1378 UNNAMEABLE_TEST_ITEMS,
1380 "detects an item that cannot be named being marked as `#[test_case]`",
1381 report_in_external_macro
1384 pub struct UnnameableTestItems {
1385 boundary: hir::HirId, // HirId of the item under which things are not nameable
1386 items_nameable: bool,
1389 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1391 impl UnnameableTestItems {
1392 pub fn new() -> Self {
1393 Self { boundary: hir::DUMMY_HIR_ID, items_nameable: true }
1397 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1398 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1399 if self.items_nameable {
1400 if let hir::ItemKind::Mod(..) = it.kind {
1402 self.items_nameable = false;
1403 self.boundary = it.hir_id;
1408 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1409 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1410 lint.build("cannot test inner items").emit()
1415 fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1416 if !self.items_nameable && self.boundary == it.hir_id {
1417 self.items_nameable = true;
1425 "detects edition keywords being used as an identifier",
1426 @future_incompatible = FutureIncompatibleInfo {
1427 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1428 edition: Some(Edition::Edition2018),
1433 /// Check for uses of edition keywords used as an identifier.
1434 KeywordIdents => [KEYWORD_IDENTS]
1437 struct UnderMacro(bool);
1439 impl KeywordIdents {
1440 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1441 for tt in tokens.into_trees() {
1443 // Only report non-raw idents.
1444 TokenTree::Token(token) => {
1445 if let Some((ident, false)) = token.ident() {
1446 self.check_ident_token(cx, UnderMacro(true), ident);
1449 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1454 fn check_ident_token(
1456 cx: &EarlyContext<'_>,
1457 UnderMacro(under_macro): UnderMacro,
1460 let next_edition = match cx.sess.edition() {
1461 Edition::Edition2015 => {
1463 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1465 // rust-lang/rust#56327: Conservatively do not
1466 // attempt to report occurrences of `dyn` within
1467 // macro definitions or invocations, because `dyn`
1468 // can legitimately occur as a contextual keyword
1469 // in 2015 code denoting its 2018 meaning, and we
1470 // do not want rustfix to inject bugs into working
1471 // code by rewriting such occurrences.
1473 // But if we see `dyn` outside of a macro, we know
1474 // its precise role in the parsed AST and thus are
1475 // assured this is truly an attempt to use it as
1477 kw::Dyn if !under_macro => Edition::Edition2018,
1483 // There are no new keywords yet for the 2018 edition and beyond.
1487 // Don't lint `r#foo`.
1488 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1492 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
1493 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
1496 "you can use a raw identifier to stay compatible",
1497 format!("r#{}", ident),
1498 Applicability::MachineApplicable,
1505 impl EarlyLintPass for KeywordIdents {
1506 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1507 self.check_tokens(cx, mac_def.body.inner_tokens());
1509 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1510 self.check_tokens(cx, mac.args.inner_tokens());
1512 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1513 self.check_ident_token(cx, UnderMacro(false), ident);
1517 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1519 impl ExplicitOutlivesRequirements {
1520 fn lifetimes_outliving_lifetime<'tcx>(
1521 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1523 ) -> Vec<ty::Region<'tcx>> {
1526 .filter_map(|(pred, _)| match pred {
1527 ty::Predicate::RegionOutlives(outlives) => {
1528 let outlives = outlives.skip_binder();
1530 ty::ReEarlyBound(ebr) if ebr.index == index => Some(outlives.1),
1539 fn lifetimes_outliving_type<'tcx>(
1540 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1542 ) -> Vec<ty::Region<'tcx>> {
1545 .filter_map(|(pred, _)| match pred {
1546 ty::Predicate::TypeOutlives(outlives) => {
1547 let outlives = outlives.skip_binder();
1548 outlives.0.is_param(index).then_some(outlives.1)
1555 fn collect_outlived_lifetimes<'tcx>(
1557 param: &'tcx hir::GenericParam<'tcx>,
1559 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
1560 ty_generics: &'tcx ty::Generics,
1561 ) -> Vec<ty::Region<'tcx>> {
1562 let index = ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id)];
1565 hir::GenericParamKind::Lifetime { .. } => {
1566 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1568 hir::GenericParamKind::Type { .. } => {
1569 Self::lifetimes_outliving_type(inferred_outlives, index)
1571 hir::GenericParamKind::Const { .. } => Vec::new(),
1575 fn collect_outlives_bound_spans<'tcx>(
1578 bounds: &hir::GenericBounds<'_>,
1579 inferred_outlives: &[ty::Region<'tcx>],
1581 ) -> Vec<(usize, Span)> {
1582 use rustc::middle::resolve_lifetime::Region;
1587 .filter_map(|(i, bound)| {
1588 if let hir::GenericBound::Outlives(lifetime) = bound {
1589 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1590 Some(Region::Static) if infer_static => inferred_outlives
1592 .any(|r| if let ty::ReStatic = r { true } else { false }),
1593 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
1594 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
1598 is_inferred.then_some((i, bound.span()))
1606 fn consolidate_outlives_bound_spans(
1609 bounds: &hir::GenericBounds<'_>,
1610 bound_spans: Vec<(usize, Span)>,
1612 if bounds.is_empty() {
1615 if bound_spans.len() == bounds.len() {
1616 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
1617 // If all bounds are inferable, we want to delete the colon, so
1618 // start from just after the parameter (span passed as argument)
1619 vec![lo.to(last_bound_span)]
1621 let mut merged = Vec::new();
1622 let mut last_merged_i = None;
1624 let mut from_start = true;
1625 for (i, bound_span) in bound_spans {
1626 match last_merged_i {
1627 // If the first bound is inferable, our span should also eat the leading `+`.
1629 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1630 last_merged_i = Some(0);
1632 // If consecutive bounds are inferable, merge their spans
1633 Some(h) if i == h + 1 => {
1634 if let Some(tail) = merged.last_mut() {
1635 // Also eat the trailing `+` if the first
1636 // more-than-one bound is inferable
1637 let to_span = if from_start && i < bounds.len() {
1638 bounds[i + 1].span().shrink_to_lo()
1642 *tail = tail.to(to_span);
1643 last_merged_i = Some(i);
1645 bug!("another bound-span visited earlier");
1649 // When we find a non-inferable bound, subsequent inferable bounds
1650 // won't be consecutive from the start (and we'll eat the leading
1651 // `+` rather than the trailing one)
1653 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
1654 last_merged_i = Some(i);
1663 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1664 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'_>) {
1665 use rustc::middle::resolve_lifetime::Region;
1667 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1668 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1669 if let hir::ItemKind::Struct(_, ref hir_generics)
1670 | hir::ItemKind::Enum(_, ref hir_generics)
1671 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
1673 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1674 if inferred_outlives.is_empty() {
1678 let ty_generics = cx.tcx.generics_of(def_id);
1680 let mut bound_count = 0;
1681 let mut lint_spans = Vec::new();
1683 for param in hir_generics.params {
1684 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1685 if let hir::GenericBound::Outlives(_) = bound { true } else { false }
1687 if !has_lifetime_bounds {
1691 let relevant_lifetimes =
1692 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
1693 if relevant_lifetimes.is_empty() {
1697 let bound_spans = self.collect_outlives_bound_spans(
1700 &relevant_lifetimes,
1703 bound_count += bound_spans.len();
1704 lint_spans.extend(self.consolidate_outlives_bound_spans(
1705 param.span.shrink_to_hi(),
1711 let mut where_lint_spans = Vec::new();
1712 let mut dropped_predicate_count = 0;
1713 let num_predicates = hir_generics.where_clause.predicates.len();
1714 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1715 let (relevant_lifetimes, bounds, span) = match where_predicate {
1716 hir::WherePredicate::RegionPredicate(predicate) => {
1717 if let Some(Region::EarlyBound(index, ..)) =
1718 cx.tcx.named_region(predicate.lifetime.hir_id)
1721 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1729 hir::WherePredicate::BoundPredicate(predicate) => {
1730 // FIXME we can also infer bounds on associated types,
1731 // and should check for them here.
1732 match predicate.bounded_ty.kind {
1733 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1734 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1735 let index = ty_generics.param_def_id_to_index[&def_id];
1737 Self::lifetimes_outliving_type(inferred_outlives, index),
1752 if relevant_lifetimes.is_empty() {
1756 let bound_spans = self.collect_outlives_bound_spans(
1759 &relevant_lifetimes,
1762 bound_count += bound_spans.len();
1764 let drop_predicate = bound_spans.len() == bounds.len();
1766 dropped_predicate_count += 1;
1769 // If all the bounds on a predicate were inferable and there are
1770 // further predicates, we want to eat the trailing comma.
1771 if drop_predicate && i + 1 < num_predicates {
1772 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1773 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
1775 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
1776 span.shrink_to_lo(),
1783 // If all predicates are inferable, drop the entire clause
1784 // (including the `where`)
1785 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1786 let where_span = hir_generics
1789 .expect("span of (nonempty) where clause should exist");
1790 // Extend the where clause back to the closing `>` of the
1791 // generics, except for tuple struct, which have the `where`
1792 // after the fields of the struct.
1793 let full_where_span =
1794 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
1797 hir_generics.span.shrink_to_hi().to(where_span)
1799 lint_spans.push(full_where_span);
1801 lint_spans.extend(where_lint_spans);
1804 if !lint_spans.is_empty() {
1805 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
1806 lint.build("outlives requirements can be inferred")
1807 .multipart_suggestion(
1808 if bound_count == 1 {
1811 "remove these bounds"
1815 .map(|span| (span, "".to_owned()))
1816 .collect::<Vec<_>>(),
1817 Applicability::MachineApplicable,
1827 pub INCOMPLETE_FEATURES,
1829 "incomplete features that may function improperly in some or all cases"
1833 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `librustc_feature/active.rs`.
1834 IncompleteFeatures => [INCOMPLETE_FEATURES]
1837 impl EarlyLintPass for IncompleteFeatures {
1838 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
1839 let features = cx.sess.features_untracked();
1841 .declared_lang_features
1843 .map(|(name, span, _)| (name, span))
1844 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
1845 .filter(|(name, _)| rustc_feature::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
1846 .for_each(|(name, &span)| {
1847 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
1848 lint.build(&format!(
1849 "the feature `{}` is incomplete and may cause the compiler to crash",
1861 "an invalid value is being created (such as a NULL reference)"
1864 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
1866 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
1867 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>) {
1868 #[derive(Debug, Copy, Clone, PartialEq)]
1874 /// Information about why a type cannot be initialized this way.
1875 /// Contains an error message and optionally a span to point at.
1876 type InitError = (String, Option<Span>);
1878 /// Test if this constant is all-0.
1879 fn is_zero(expr: &hir::Expr<'_>) -> bool {
1880 use hir::ExprKind::*;
1881 use syntax::ast::LitKind::*;
1884 if let Int(i, _) = lit.node {
1890 Tup(tup) => tup.iter().all(is_zero),
1895 /// Determine if this expression is a "dangerous initialization".
1896 fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
1897 // `transmute` is inside an anonymous module (the `extern` block?);
1898 // `Invalid` represents the empty string and matches that.
1899 // FIXME(#66075): use diagnostic items. Somehow, that does not seem to work
1900 // on intrinsics right now.
1901 const TRANSMUTE_PATH: &[Symbol] =
1902 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
1904 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
1905 // Find calls to `mem::{uninitialized,zeroed}` methods.
1906 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1907 let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1909 if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
1910 return Some(InitKind::Zeroed);
1911 } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
1912 return Some(InitKind::Uninit);
1913 } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
1914 if is_zero(&args[0]) {
1915 return Some(InitKind::Zeroed);
1919 } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
1920 // Find problematic calls to `MaybeUninit::assume_init`.
1921 let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
1922 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
1923 // This is a call to *some* method named `assume_init`.
1924 // See if the `self` parameter is one of the dangerous constructors.
1925 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
1926 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
1928 cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
1930 if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
1931 return Some(InitKind::Zeroed);
1932 } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
1933 return Some(InitKind::Uninit);
1943 /// Return `Some` only if we are sure this type does *not*
1944 /// allow zero initialization.
1945 fn ty_find_init_error<'tcx>(
1949 ) -> Option<InitError> {
1950 use rustc::ty::TyKind::*;
1952 // Primitive types that don't like 0 as a value.
1953 Ref(..) => Some((format!("references must be non-null"), None)),
1954 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
1955 FnPtr(..) => Some((format!("function pointers must be non-null"), None)),
1956 Never => Some((format!("the `!` type has no valid value"), None)),
1957 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
1958 // raw ptr to dyn Trait
1960 Some((format!("the vtable of a wide raw pointer must be non-null"), None))
1962 // Primitive types with other constraints.
1963 Bool if init == InitKind::Uninit => {
1964 Some((format!("booleans must be either `true` or `false`"), None))
1966 Char if init == InitKind::Uninit => {
1967 Some((format!("characters must be a valid Unicode codepoint"), None))
1969 // Recurse and checks for some compound types.
1970 Adt(adt_def, substs) if !adt_def.is_union() => {
1971 // First check f this ADT has a layout attribute (like `NonNull` and friends).
1972 use std::ops::Bound;
1973 match tcx.layout_scalar_valid_range(adt_def.did) {
1974 // We exploit here that `layout_scalar_valid_range` will never
1975 // return `Bound::Excluded`. (And we have tests checking that we
1976 // handle the attribute correctly.)
1977 (Bound::Included(lo), _) if lo > 0 => {
1978 return Some((format!("`{}` must be non-null", ty), None));
1980 (Bound::Included(_), _) | (_, Bound::Included(_))
1981 if init == InitKind::Uninit =>
1985 "`{}` must be initialized inside its custom valid range",
1994 match adt_def.variants.len() {
1995 0 => Some((format!("enums with no variants have no valid value"), None)),
1997 // Struct, or enum with exactly one variant.
1998 // Proceed recursively, check all fields.
1999 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2000 variant.fields.iter().find_map(|field| {
2001 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2004 // Point to this field, should be helpful for figuring
2005 // out where the source of the error is.
2006 let span = tcx.def_span(field.did);
2009 " (in this {} field)",
2022 // Multi-variant enums are tricky: if all but one variant are
2023 // uninhabited, we might actually do layout like for a single-variant
2024 // enum, and then even leaving them uninitialized could be okay.
2025 _ => None, // Conservative fallback for multi-variant enum.
2029 // Proceed recursively, check all fields.
2030 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2032 // Conservative fallback.
2037 if let Some(init) = is_dangerous_init(cx, expr) {
2038 // This conjures an instance of a type out of nothing,
2039 // using zeroed or uninitialized memory.
2040 // We are extremely conservative with what we warn about.
2041 let conjured_ty = cx.tables.expr_ty(expr);
2042 if let Some((msg, span)) = ty_find_init_error(cx.tcx, conjured_ty, init) {
2043 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2044 let mut err = lint.build(&format!(
2045 "the type `{}` does not permit {}",
2048 InitKind::Zeroed => "zero-initialization",
2049 InitKind::Uninit => "being left uninitialized",
2052 err.span_label(expr.span, "this code causes undefined behavior when executed");
2055 "help: use `MaybeUninit<T>` instead, \
2056 and only call `assume_init` after initialization is done",
2058 if let Some(span) = span {
2059 err.span_note(span, &msg);