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 rustc::hir::def::{Res, DefKind};
25 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
26 use rustc::ty::{self, Ty, TyCtxt};
27 use rustc::{lint, util};
29 use util::nodemap::HirIdSet;
30 use lint::{LateContext, LintContext, LintArray};
31 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
33 use rustc::util::nodemap::FxHashSet;
35 use syntax::tokenstream::{TokenTree, TokenStream};
38 use syntax::ast::Expr;
39 use syntax::attr::{self, HasAttrs, AttributeTemplate};
40 use syntax::source_map::Spanned;
41 use syntax::edition::Edition;
42 use syntax::feature_gate::{AttributeGate, AttributeType};
43 use syntax::feature_gate::{Stability, deprecated_attributes};
44 use syntax_pos::{BytePos, Span, SyntaxContext};
45 use syntax::symbol::{Symbol, kw, sym};
46 use syntax::errors::{Applicability, DiagnosticBuilder};
47 use syntax::print::pprust::expr_to_string;
48 use syntax::visit::FnKind;
50 use rustc::hir::{self, GenericParamKind, PatKind};
52 use crate::nonstandard_style::{MethodLateContext, method_context};
56 // hardwired lints from librustc
57 pub use lint::builtin::*;
62 "suggest using `loop { }` instead of `while true { }`"
65 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
67 /// Traverse through any amount of parenthesis and return the first non-parens expression.
68 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
69 while let ast::ExprKind::Paren(sub) = &expr.node {
75 impl EarlyLintPass for WhileTrue {
76 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
77 if let ast::ExprKind::While(cond, ..) = &e.node {
78 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).node {
79 if let ast::LitKind::Bool(true) = lit.node {
80 if lit.span.ctxt() == SyntaxContext::empty() {
81 let msg = "denote infinite loops with `loop { ... }`";
82 let condition_span = cx.sess.source_map().def_span(e.span);
83 cx.struct_span_lint(WHILE_TRUE, condition_span, msg)
84 .span_suggestion_short(
88 Applicability::MachineApplicable
101 "use of owned (Box type) heap memory"
104 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
107 fn check_heap_type(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
108 for leaf_ty in ty.walk() {
109 if leaf_ty.is_box() {
110 let m = format!("type uses owned (Box type) pointers: {}", ty);
111 cx.span_lint(BOX_POINTERS, span, &m);
117 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
118 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
120 hir::ItemKind::Fn(..) |
121 hir::ItemKind::Ty(..) |
122 hir::ItemKind::Enum(..) |
123 hir::ItemKind::Struct(..) |
124 hir::ItemKind::Union(..) => {
125 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
126 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
131 // If it's a struct, we also have to check the fields' types
133 hir::ItemKind::Struct(ref struct_def, _) |
134 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,
138 cx.tcx.type_of(def_id));
145 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
146 let ty = cx.tables.node_type(e.hir_id);
147 self.check_heap_type(cx, e.span, ty);
152 NON_SHORTHAND_FIELD_PATTERNS,
154 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
157 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
159 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
160 fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat) {
161 if let PatKind::Struct(ref qpath, ref field_pats, _) = pat.node {
162 let variant = cx.tables.pat_ty(pat).ty_adt_def()
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.node.is_shorthand {
169 if fieldpat.span.ctxt().outer_expn_info().is_some() {
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(_, _, ident, None) = fieldpat.node.pat.node {
176 if cx.tcx.find_field_index(ident, &variant) ==
177 Some(cx.tcx.field_index(fieldpat.node.hir_id, cx.tables)) {
178 let mut err = cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS,
180 &format!("the `{}:` in this pattern is redundant", ident));
181 let subspan = cx.tcx.sess.source_map().span_through_char(fieldpat.span,
183 err.span_suggestion_short(
187 Applicability::MachineApplicable
200 "usage of `unsafe` code"
203 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
206 fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
207 // This comes from a macro that has `#[allow_internal_unsafe]`.
208 if span.allows_unsafe() {
212 cx.span_lint(UNSAFE_CODE, span, desc);
216 impl EarlyLintPass for UnsafeCode {
217 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
218 if attr.check_name(sym::allow_internal_unsafe) {
219 self.report_unsafe(cx, attr.span, "`allow_internal_unsafe` allows defining \
220 macros using unsafe without triggering \
221 the `unsafe_code` lint at their call site");
225 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
226 if let ast::ExprKind::Block(ref blk, _) = e.node {
227 // Don't warn about generated blocks; that'll just pollute the output.
228 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
229 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
234 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
236 ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
237 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
240 ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
241 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
248 fn check_fn(&mut self,
249 cx: &EarlyContext<'_>,
255 FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
256 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
259 FnKind::Method(_, sig, ..) => {
260 if sig.header.unsafety == ast::Unsafety::Unsafe {
261 self.report_unsafe(cx, span, "implementation of an `unsafe` method")
269 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::TraitItem) {
270 if let ast::TraitItemKind::Method(ref sig, None) = item.node {
271 if sig.header.unsafety == ast::Unsafety::Unsafe {
272 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
281 "detects missing documentation for public members",
282 report_in_external_macro: true
285 pub struct MissingDoc {
286 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
287 doc_hidden_stack: Vec<bool>,
289 /// Private traits or trait items that leaked through. Don't check their methods.
290 private_traits: FxHashSet<hir::HirId>,
293 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
295 fn has_doc(attr: &ast::Attribute) -> bool {
296 if !attr.check_name(sym::doc) {
300 if attr.is_value_str() {
304 if let Some(list) = attr.meta_item_list() {
306 if meta.check_name(sym::include) || meta.check_name(sym::hidden) {
316 pub fn new() -> MissingDoc {
318 doc_hidden_stack: vec![false],
319 private_traits: FxHashSet::default(),
323 fn doc_hidden(&self) -> bool {
324 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
327 fn check_missing_docs_attrs(&self,
328 cx: &LateContext<'_, '_>,
329 id: Option<hir::HirId>,
330 attrs: &[ast::Attribute],
332 desc: &'static str) {
333 // If we're building a test harness, then warning about
334 // documentation is probably not really relevant right now.
335 if cx.sess().opts.test {
339 // `#[doc(hidden)]` disables missing_docs check.
340 if self.doc_hidden() {
344 // Only check publicly-visible items, using the result from the privacy pass.
345 // It's an option so the crate root can also use this function (it doesn't
347 if let Some(id) = id {
348 if !cx.access_levels.is_exported(id) {
353 let has_doc = attrs.iter().any(|a| has_doc(a));
355 cx.span_lint(MISSING_DOCS,
356 cx.tcx.sess.source_map().def_span(sp),
357 &format!("missing documentation for {}", desc));
362 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
363 fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
364 let doc_hidden = self.doc_hidden() ||
365 attrs.iter().any(|attr| {
366 attr.check_name(sym::doc) &&
367 match attr.meta_item_list() {
369 Some(l) => attr::list_contains_name(&l, sym::hidden),
372 self.doc_hidden_stack.push(doc_hidden);
375 fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
376 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
379 fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate) {
380 self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
382 for macro_def in &krate.exported_macros {
383 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
385 cx.span_lint(MISSING_DOCS,
386 cx.tcx.sess.source_map().def_span(macro_def.span),
387 "missing documentation for macro");
392 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
393 let desc = match it.node {
394 hir::ItemKind::Fn(..) => "a function",
395 hir::ItemKind::Mod(..) => "a module",
396 hir::ItemKind::Enum(..) => "an enum",
397 hir::ItemKind::Struct(..) => "a struct",
398 hir::ItemKind::Union(..) => "a union",
399 hir::ItemKind::Trait(.., ref trait_item_refs) => {
400 // Issue #11592: traits are always considered exported, even when private.
401 if let hir::VisibilityKind::Inherited = it.vis.node {
402 self.private_traits.insert(it.hir_id);
403 for trait_item_ref in trait_item_refs {
404 self.private_traits.insert(trait_item_ref.id.hir_id);
410 hir::ItemKind::Ty(..) => "a type alias",
411 hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
412 // If the trait is private, add the impl items to `private_traits` so they don't get
413 // reported for missing docs.
414 let real_trait = trait_ref.path.res.def_id();
415 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(real_trait) {
416 match cx.tcx.hir().find(hir_id) {
417 Some(Node::Item(item)) => {
418 if let hir::VisibilityKind::Inherited = item.vis.node {
419 for impl_item_ref in impl_item_refs {
420 self.private_traits.insert(impl_item_ref.id.hir_id);
429 hir::ItemKind::Const(..) => "a constant",
430 hir::ItemKind::Static(..) => "a static",
434 self.check_missing_docs_attrs(cx, Some(it.hir_id), &it.attrs, it.span, desc);
437 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem) {
438 if self.private_traits.contains(&trait_item.hir_id) {
442 let desc = match trait_item.node {
443 hir::TraitItemKind::Const(..) => "an associated constant",
444 hir::TraitItemKind::Method(..) => "a trait method",
445 hir::TraitItemKind::Type(..) => "an associated type",
448 self.check_missing_docs_attrs(cx,
449 Some(trait_item.hir_id),
455 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
456 // If the method is an impl for a trait, don't doc.
457 if method_context(cx, impl_item.hir_id) == MethodLateContext::TraitImpl {
461 let desc = match impl_item.node {
462 hir::ImplItemKind::Const(..) => "an associated constant",
463 hir::ImplItemKind::Method(..) => "a method",
464 hir::ImplItemKind::Type(_) => "an associated type",
465 hir::ImplItemKind::Existential(_) => "an associated existential type",
467 self.check_missing_docs_attrs(cx,
468 Some(impl_item.hir_id),
474 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField) {
475 if !sf.is_positional() {
476 self.check_missing_docs_attrs(cx,
484 fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant, _: &hir::Generics) {
485 self.check_missing_docs_attrs(cx,
494 pub MISSING_COPY_IMPLEMENTATIONS,
496 "detects potentially-forgotten implementations of `Copy`"
499 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
501 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
502 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
503 if !cx.access_levels.is_reachable(item.hir_id) {
506 let (def, ty) = match item.node {
507 hir::ItemKind::Struct(_, ref ast_generics) => {
508 if !ast_generics.params.is_empty() {
511 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
512 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
514 hir::ItemKind::Union(_, ref ast_generics) => {
515 if !ast_generics.params.is_empty() {
518 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
519 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
521 hir::ItemKind::Enum(_, ref ast_generics) => {
522 if !ast_generics.params.is_empty() {
525 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.hir_id));
526 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
530 if def.has_dtor(cx.tcx) {
533 let param_env = ty::ParamEnv::empty();
534 if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
537 if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
538 cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
540 "type could implement `Copy`; consider adding `impl \
547 MISSING_DEBUG_IMPLEMENTATIONS,
549 "detects missing implementations of fmt::Debug"
553 pub struct MissingDebugImplementations {
554 impling_types: Option<HirIdSet>,
557 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
559 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
560 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
561 if !cx.access_levels.is_reachable(item.hir_id) {
566 hir::ItemKind::Struct(..) |
567 hir::ItemKind::Union(..) |
568 hir::ItemKind::Enum(..) => {}
572 let debug = match cx.tcx.lang_items().debug_trait() {
573 Some(debug) => debug,
577 if self.impling_types.is_none() {
578 let mut impls = HirIdSet::default();
579 cx.tcx.for_each_impl(debug, |d| {
580 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
581 if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(ty_def.did) {
582 impls.insert(hir_id);
587 self.impling_types = Some(impls);
588 debug!("{:?}", self.impling_types);
591 if !self.impling_types.as_ref().unwrap().contains(&item.hir_id) {
592 cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
594 "type does not implement `fmt::Debug`; consider adding `#[derive(Debug)]` \
595 or a manual implementation")
601 pub ANONYMOUS_PARAMETERS,
603 "detects anonymous parameters"
607 /// Checks for use of anonymous parameters (RFC 1685).
608 AnonymousParameters => [ANONYMOUS_PARAMETERS]
611 impl EarlyLintPass for AnonymousParameters {
612 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::TraitItem) {
614 ast::TraitItemKind::Method(ref sig, _) => {
615 for arg in sig.decl.inputs.iter() {
617 ast::PatKind::Ident(_, ident, None) => {
618 if ident.name == kw::Invalid {
622 .span_to_snippet(arg.ty.span);
624 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
625 (snip, Applicability::MachineApplicable)
627 ("<type>".to_owned(), Applicability::HasPlaceholders)
631 ANONYMOUS_PARAMETERS,
633 "anonymous parameters are deprecated and will be \
634 removed in the next edition."
637 "Try naming the parameter or explicitly \
639 format!("_: {}", ty_snip),
653 /// Check for use of attributes which have been deprecated.
655 pub struct DeprecatedAttr {
656 // This is not free to compute, so we want to keep it around, rather than
657 // compute it for every attribute.
658 depr_attrs: Vec<&'static (Symbol, AttributeType, AttributeTemplate, AttributeGate)>,
661 impl_lint_pass!(DeprecatedAttr => []);
663 impl DeprecatedAttr {
664 pub fn new() -> DeprecatedAttr {
666 depr_attrs: deprecated_attributes(),
671 impl EarlyLintPass for DeprecatedAttr {
672 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
673 for &&(n, _, _, ref g) in &self.depr_attrs {
674 if attr.ident().map(|ident| ident.name) == Some(n) {
675 if let &AttributeGate::Gated(Stability::Deprecated(link, suggestion),
679 let msg = format!("use of deprecated attribute `{}`: {}. See {}",
681 let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
682 err.span_suggestion_short(
684 suggestion.unwrap_or("remove this attribute"),
686 Applicability::MachineApplicable
697 pub UNUSED_DOC_COMMENTS,
699 "detects doc comments that aren't used by rustdoc"
702 declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
704 impl UnusedDocComment {
707 cx: &EarlyContext<'_>,
710 is_macro_expansion: bool,
711 attrs: &[ast::Attribute]
713 let mut attrs = attrs.into_iter().peekable();
715 // Accumulate a single span for sugared doc comments.
716 let mut sugared_span: Option<Span> = None;
718 while let Some(attr) = attrs.next() {
719 if attr.is_sugared_doc {
721 sugared_span.map_or_else(
723 |span| span.with_hi(attr.span.hi()),
728 if attrs.peek().map(|next_attr| next_attr.is_sugared_doc).unwrap_or_default() {
732 let span = sugared_span.take().unwrap_or_else(|| attr.span);
734 if attr.check_name(sym::doc) {
735 let mut err = cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, "unused doc comment");
739 format!("rustdoc does not generate documentation for {}", node_kind)
742 if is_macro_expansion {
743 err.help("to document an item produced by a macro, \
744 the macro must produce the documentation as part of its expansion");
753 impl EarlyLintPass for UnusedDocComment {
754 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
755 if let ast::ItemKind::Mac(..) = item.node {
756 self.warn_if_doc(cx, item.span, "macro expansions", true, &item.attrs);
760 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
761 let (kind, is_macro_expansion) = match stmt.node {
762 ast::StmtKind::Local(..) => ("statements", false),
763 ast::StmtKind::Item(..) => ("inner items", false),
764 ast::StmtKind::Mac(..) => ("macro expansions", true),
765 // expressions will be reported by `check_expr`.
766 ast::StmtKind::Semi(..) |
767 ast::StmtKind::Expr(..) => return,
770 self.warn_if_doc(cx, stmt.span, kind, is_macro_expansion, stmt.node.attrs());
773 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
774 let arm_span = arm.pats[0].span.with_hi(arm.body.span.hi());
775 self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
778 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
779 self.warn_if_doc(cx, expr.span, "expressions", false, &expr.attrs);
786 "compiler plugin used as ordinary library in non-plugin crate"
789 declare_lint_pass!(PluginAsLibrary => [PLUGIN_AS_LIBRARY]);
791 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
792 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
793 if cx.tcx.plugin_registrar_fn(LOCAL_CRATE).is_some() {
794 // We're compiling a plugin; it's fine to link other plugins.
799 hir::ItemKind::ExternCrate(..) => (),
803 let def_id = cx.tcx.hir().local_def_id(it.hir_id);
804 let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
805 Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
807 // Probably means we aren't linking the crate for some reason.
809 // Not sure if / when this could happen.
815 cx.span_lint(PLUGIN_AS_LIBRARY,
817 "compiler plugin used as an ordinary library");
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 { .. } |
845 GenericParamKind::Const { .. } => {
846 let mut err = cx.struct_span_lint(
847 NO_MANGLE_GENERIC_ITEMS,
849 "functions generic over types or consts must be mangled",
851 err.span_suggestion_short(
853 "remove this attribute",
855 // Use of `#[no_mangle]` suggests FFI intent; correct
856 // fix may be to monomorphize source by hand
857 Applicability::MaybeIncorrect
866 hir::ItemKind::Const(..) => {
867 if attr::contains_name(&it.attrs, sym::no_mangle) {
868 // Const items do not refer to a particular location in memory, and therefore
869 // don't have anything to attach a symbol to
870 let msg = "const items should never be `#[no_mangle]`";
871 let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
873 // account for "pub const" (#45562)
874 let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
875 .map(|snippet| snippet.find("const").unwrap_or(0))
876 .unwrap_or(0) as u32;
877 // `const` is 5 chars
878 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
881 "try a static value",
882 "pub static".to_owned(),
883 Applicability::MachineApplicable
896 "mutating transmuted &mut T from &T may cause undefined behavior"
899 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
901 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
902 fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr) {
903 use rustc_target::spec::abi::Abi::RustIntrinsic;
905 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
906 consider instead using an UnsafeCell";
907 match get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (&ty1.sty, &ty2.sty)) {
908 Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
909 if to_mt == hir::Mutability::MutMutable &&
910 from_mt == hir::Mutability::MutImmutable {
911 cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
917 fn get_transmute_from_to<'a, 'tcx>
918 (cx: &LateContext<'a, 'tcx>,
920 -> Option<(Ty<'tcx>, Ty<'tcx>)> {
921 let def = if let hir::ExprKind::Path(ref qpath) = expr.node {
922 cx.tables.qpath_res(qpath, expr.hir_id)
926 if let Res::Def(DefKind::Fn, did) = def {
927 if !def_id_is_transmute(cx, did) {
930 let sig = cx.tables.node_type(expr.hir_id).fn_sig(cx.tcx);
931 let from = sig.inputs().skip_binder()[0];
932 let to = *sig.output().skip_binder();
933 return Some((from, to));
938 fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
939 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
940 cx.tcx.item_name(def_id) == sym::transmute
948 "enabling unstable features (deprecated. do not use)"
952 /// Forbids using the `#[feature(...)]` attribute
953 UnstableFeatures => [UNSTABLE_FEATURES]
956 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
957 fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
958 if attr.check_name(sym::feature) {
959 if let Some(items) = attr.meta_item_list() {
961 ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
969 UNIONS_WITH_DROP_FIELDS,
971 "use of unions that contain fields with possibly non-trivial drop code"
975 /// Lint for unions that contain fields with possibly non-trivial destructors.
976 UnionsWithDropFields => [UNIONS_WITH_DROP_FIELDS]
979 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
980 fn check_item(&mut self, ctx: &LateContext<'_, '_>, item: &hir::Item) {
981 if let hir::ItemKind::Union(ref vdata, _) = item.node {
982 for field in vdata.fields() {
983 let field_ty = ctx.tcx.type_of(
984 ctx.tcx.hir().local_def_id(field.hir_id));
985 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
986 ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
988 "union contains a field with possibly non-trivial drop code, \
989 drop code of union fields is ignored when dropping the union");
1000 "`pub` items not reachable from crate root"
1004 /// Lint for items marked `pub` that aren't reachable from other crates.
1005 UnreachablePub => [UNREACHABLE_PUB]
1008 impl UnreachablePub {
1009 fn perform_lint(&self, cx: &LateContext<'_, '_>, what: &str, id: hir::HirId,
1010 vis: &hir::Visibility, span: Span, exportable: bool) {
1011 let mut applicability = Applicability::MachineApplicable;
1013 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1014 if span.ctxt().outer_expn_info().is_some() {
1015 applicability = Applicability::MaybeIncorrect;
1017 let def_span = cx.tcx.sess.source_map().def_span(span);
1018 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1019 &format!("unreachable `pub` {}", what));
1020 let replacement = if cx.tcx.features().crate_visibility_modifier {
1026 err.span_suggestion(
1028 "consider restricting its visibility",
1033 err.help("or consider exporting it for use by other crates");
1042 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1043 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1044 self.perform_lint(cx, "item", item.hir_id, &item.vis, item.span, true);
1047 fn check_foreign_item(&mut self, cx: &LateContext<'_, '_>, foreign_item: &hir::ForeignItem) {
1048 self.perform_lint(cx, "item", foreign_item.hir_id, &foreign_item.vis,
1049 foreign_item.span, true);
1052 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
1053 self.perform_lint(cx, "field", field.hir_id, &field.vis, field.span, false);
1056 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
1057 self.perform_lint(cx, "item", impl_item.hir_id, &impl_item.vis, impl_item.span, false);
1064 "bounds in type aliases are not enforced"
1068 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1069 /// They are relevant when using associated types, but otherwise neither checked
1070 /// at definition site nor enforced at use site.
1071 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1074 impl TypeAliasBounds {
1075 fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1077 hir::QPath::TypeRelative(ref ty, _) => {
1078 // If this is a type variable, we found a `T::Assoc`.
1080 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1082 Res::Def(DefKind::TyParam, _) => true,
1089 hir::QPath::Resolved(..) => false,
1093 fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder<'_>) {
1094 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1095 // bound. Let's see if this type does that.
1097 // We use a HIR visitor to walk the type.
1098 use rustc::hir::intravisit::{self, Visitor};
1099 struct WalkAssocTypes<'a, 'db> {
1100 err: &'a mut DiagnosticBuilder<'db>
1102 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1103 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v>
1105 intravisit::NestedVisitorMap::None
1108 fn visit_qpath(&mut self, qpath: &'v hir::QPath, id: hir::HirId, span: Span) {
1109 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1110 self.err.span_help(span,
1111 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1112 associated types in type aliases");
1114 intravisit::walk_qpath(self, qpath, id, span)
1118 // Let's go for a walk!
1119 let mut visitor = WalkAssocTypes { err };
1120 visitor.visit_ty(ty);
1124 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1125 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1126 let (ty, type_alias_generics) = match item.node {
1127 hir::ItemKind::Ty(ref ty, ref generics) => (&*ty, generics),
1130 let mut suggested_changing_assoc_types = false;
1131 // There must not be a where clause
1132 if !type_alias_generics.where_clause.predicates.is_empty() {
1133 let spans : Vec<_> = type_alias_generics.where_clause.predicates.iter()
1134 .map(|pred| pred.span()).collect();
1135 let mut err = cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans,
1136 "where clauses are not enforced in type aliases");
1137 err.help("the clause will not be checked when the type alias is used, \
1138 and should be removed");
1139 if !suggested_changing_assoc_types {
1140 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1141 suggested_changing_assoc_types = true;
1145 // The parameters must not have bounds
1146 for param in type_alias_generics.params.iter() {
1147 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1148 if !spans.is_empty() {
1149 let mut err = cx.struct_span_lint(
1152 "bounds on generic parameters are not enforced in type aliases",
1154 err.help("the bound will not be checked when the type alias is used, \
1155 and should be removed");
1156 if !suggested_changing_assoc_types {
1157 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1158 suggested_changing_assoc_types = true;
1167 /// Lint constants that are erroneous.
1168 /// Without this lint, we might not get any diagnostic if the constant is
1169 /// unused within this crate, even though downstream crates can't use it
1170 /// without producing an error.
1171 UnusedBrokenConst => []
1174 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1175 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1176 let param_env = if cx.tcx.is_static(def_id) {
1177 // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
1178 ty::ParamEnv::reveal_all()
1180 cx.tcx.param_env(def_id)
1182 let cid = ::rustc::mir::interpret::GlobalId {
1183 instance: ty::Instance::mono(cx.tcx, def_id),
1186 // trigger the query once for all constants since that will already report the errors
1187 // FIXME: Use ensure here
1188 let _ = cx.tcx.const_eval(param_env.and(cid));
1191 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1192 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1194 hir::ItemKind::Const(_, body_id) => {
1195 check_const(cx, body_id);
1197 hir::ItemKind::Static(_, _, body_id) => {
1198 check_const(cx, body_id);
1208 "these bounds don't depend on an type parameters"
1212 /// Lint for trait and lifetime bounds that don't depend on type parameters
1213 /// which either do nothing, or stop the item from being used.
1214 TrivialConstraints => [TRIVIAL_BOUNDS]
1217 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1220 cx: &LateContext<'a, 'tcx>,
1221 item: &'tcx hir::Item,
1223 use rustc::ty::fold::TypeFoldable;
1224 use rustc::ty::Predicate::*;
1226 if cx.tcx.features().trivial_bounds {
1227 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1228 let predicates = cx.tcx.predicates_of(def_id);
1229 for &(predicate, span) in &predicates.predicates {
1230 let predicate_kind_name = match predicate {
1231 Trait(..) => "Trait",
1233 RegionOutlives(..) => "Lifetime",
1235 // Ignore projections, as they can only be global
1236 // if the trait bound is global
1238 // Ignore bounds that a user can't type
1243 ConstEvaluatable(..) => continue,
1245 if predicate.is_global() {
1249 &format!("{} bound {} does not depend on any type \
1250 or lifetime parameters", predicate_kind_name, predicate),
1259 /// Does nothing as a lint pass, but registers some `Lint`s
1260 /// which are used by other parts of the compiler.
1264 NON_SHORTHAND_FIELD_PATTERNS,
1267 MISSING_COPY_IMPLEMENTATIONS,
1268 MISSING_DEBUG_IMPLEMENTATIONS,
1269 ANONYMOUS_PARAMETERS,
1270 UNUSED_DOC_COMMENTS,
1272 NO_MANGLE_CONST_ITEMS,
1273 NO_MANGLE_GENERIC_ITEMS,
1276 UNIONS_WITH_DROP_FIELDS,
1284 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1286 "`...` range patterns are deprecated"
1290 pub struct EllipsisInclusiveRangePatterns {
1291 /// If `Some(_)`, suppress all subsequent pattern
1292 /// warnings for better diagnostics.
1293 node_id: Option<ast::NodeId>,
1296 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1298 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1299 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1300 if self.node_id.is_some() {
1301 // Don't recursively warn about patterns inside range endpoints.
1305 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1307 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1308 /// corresponding to the ellipsis.
1309 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(&P<Expr>, &P<Expr>, Span)> {
1311 PatKind::Range(a, b, Spanned { span, node: RangeEnd::Included(DotDotDot), .. }) => {
1318 let (parenthesise, endpoints) = match &pat.node {
1319 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1320 _ => (false, matches_ellipsis_pat(pat)),
1323 if let Some((start, end, join)) = endpoints {
1324 let msg = "`...` range patterns are deprecated";
1325 let suggestion = "use `..=` for an inclusive range";
1327 self.node_id = Some(pat.id);
1328 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1329 err.span_suggestion(
1332 format!("&({}..={})", expr_to_string(&start), expr_to_string(&end)),
1333 Applicability::MachineApplicable,
1337 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1338 err.span_suggestion_short(
1342 Applicability::MachineApplicable,
1349 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1350 if let Some(node_id) = self.node_id {
1351 if pat.id == node_id {
1359 UNNAMEABLE_TEST_ITEMS,
1361 "detects an item that cannot be named being marked as `#[test_case]`",
1362 report_in_external_macro: true
1365 pub struct UnnameableTestItems {
1366 boundary: hir::HirId, // HirId of the item under which things are not nameable
1367 items_nameable: bool,
1370 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1372 impl UnnameableTestItems {
1373 pub fn new() -> Self {
1375 boundary: hir::DUMMY_HIR_ID,
1376 items_nameable: true
1381 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1382 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1383 if self.items_nameable {
1384 if let hir::ItemKind::Mod(..) = it.node {}
1386 self.items_nameable = false;
1387 self.boundary = it.hir_id;
1392 if let Some(attr) = attr::find_by_name(&it.attrs, sym::rustc_test_marker) {
1393 cx.struct_span_lint(
1394 UNNAMEABLE_TEST_ITEMS,
1396 "cannot test inner items",
1401 fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item) {
1402 if !self.items_nameable && self.boundary == it.hir_id {
1403 self.items_nameable = true;
1411 "detects edition keywords being used as an identifier"
1415 /// Check for uses of edition keywords used as an identifier.
1416 KeywordIdents => [KEYWORD_IDENTS]
1419 struct UnderMacro(bool);
1421 impl KeywordIdents {
1422 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1423 for tt in tokens.into_trees() {
1425 // Only report non-raw idents.
1426 TokenTree::Token(token) => if let Some((ident, false)) = token.ident() {
1427 self.check_ident_token(cx, UnderMacro(true), ident);
1429 TokenTree::Delimited(_, _, tts) => {
1430 self.check_tokens(cx, tts)
1436 fn check_ident_token(&mut self,
1437 cx: &EarlyContext<'_>,
1438 UnderMacro(under_macro): UnderMacro,
1441 let next_edition = match cx.sess.edition() {
1442 Edition::Edition2015 => {
1444 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1446 // rust-lang/rust#56327: Conservatively do not
1447 // attempt to report occurrences of `dyn` within
1448 // macro definitions or invocations, because `dyn`
1449 // can legitimately occur as a contextual keyword
1450 // in 2015 code denoting its 2018 meaning, and we
1451 // do not want rustfix to inject bugs into working
1452 // code by rewriting such occurrences.
1454 // But if we see `dyn` outside of a macro, we know
1455 // its precise role in the parsed AST and thus are
1456 // assured this is truly an attempt to use it as
1458 kw::Dyn if !under_macro => Edition::Edition2018,
1464 // There are no new keywords yet for the 2018 edition and beyond.
1468 // Don't lint `r#foo`.
1469 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
1473 let mut lint = cx.struct_span_lint(
1476 &format!("`{}` is a keyword in the {} edition",
1480 lint.span_suggestion(
1482 "you can use a raw identifier to stay compatible",
1483 format!("r#{}", ident.as_str()),
1484 Applicability::MachineApplicable,
1490 impl EarlyLintPass for KeywordIdents {
1491 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1492 self.check_tokens(cx, mac_def.stream());
1494 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1495 self.check_tokens(cx, mac.node.tts.clone().into());
1497 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1498 self.check_ident_token(cx, UnderMacro(false), ident);
1502 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1504 impl ExplicitOutlivesRequirements {
1505 fn lifetimes_outliving_lifetime<'tcx>(
1506 inferred_outlives: &'tcx [ty::Predicate<'tcx>],
1508 ) -> Vec<ty::Region<'tcx>> {
1509 inferred_outlives.iter().filter_map(|pred| {
1511 ty::Predicate::RegionOutlives(outlives) => {
1512 let outlives = outlives.skip_binder();
1514 ty::ReEarlyBound(ebr) if ebr.index == index => {
1525 fn lifetimes_outliving_type<'tcx>(
1526 inferred_outlives: &'tcx [ty::Predicate<'tcx>],
1528 ) -> Vec<ty::Region<'tcx>> {
1529 inferred_outlives.iter().filter_map(|pred| {
1531 ty::Predicate::TypeOutlives(outlives) => {
1532 let outlives = outlives.skip_binder();
1533 if outlives.0.is_param(index) {
1544 fn collect_outlived_lifetimes<'tcx>(
1546 param: &'tcx hir::GenericParam,
1548 inferred_outlives: &'tcx [ty::Predicate<'tcx>],
1549 ty_generics: &'tcx ty::Generics,
1550 ) -> Vec<ty::Region<'tcx>> {
1551 let index = ty_generics.param_def_id_to_index[
1552 &tcx.hir().local_def_id(param.hir_id)];
1555 hir::GenericParamKind::Lifetime { .. } => {
1556 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
1558 hir::GenericParamKind::Type { .. } => {
1559 Self::lifetimes_outliving_type(inferred_outlives, index)
1561 hir::GenericParamKind::Const { .. } => Vec::new(),
1566 fn collect_outlives_bound_spans<'tcx>(
1569 bounds: &hir::GenericBounds,
1570 inferred_outlives: &[ty::Region<'tcx>],
1572 ) -> Vec<(usize, Span)> {
1573 use rustc::middle::resolve_lifetime::Region;
1578 .filter_map(|(i, bound)| {
1579 if let hir::GenericBound::Outlives(lifetime) = bound {
1580 let is_inferred = match tcx.named_region(lifetime.hir_id) {
1581 Some(Region::Static) if infer_static => {
1582 inferred_outlives.iter()
1583 .any(|r| if let ty::ReStatic = r { true } else { false })
1585 Some(Region::EarlyBound(index, ..)) => inferred_outlives
1588 if let ty::ReEarlyBound(ebr) = r {
1597 Some((i, bound.span()))
1608 fn consolidate_outlives_bound_spans(
1611 bounds: &hir::GenericBounds,
1612 bound_spans: Vec<(usize, Span)>
1614 if bounds.is_empty() {
1617 if bound_spans.len() == bounds.len() {
1618 let (_, last_bound_span) = bound_spans[bound_spans.len()-1];
1619 // If all bounds are inferable, we want to delete the colon, so
1620 // start from just after the parameter (span passed as argument)
1621 vec![lo.to(last_bound_span)]
1623 let mut merged = Vec::new();
1624 let mut last_merged_i = None;
1626 let mut from_start = true;
1627 for (i, bound_span) in bound_spans {
1628 match last_merged_i {
1629 // If the first bound is inferable, our span should also eat the leading `+`.
1631 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1632 last_merged_i = Some(0);
1634 // If consecutive bounds are inferable, merge their spans
1635 Some(h) if i == h+1 => {
1636 if let Some(tail) = merged.last_mut() {
1637 // Also eat the trailing `+` if the first
1638 // more-than-one bound is inferable
1639 let to_span = if from_start && i < bounds.len() {
1640 bounds[i+1].span().shrink_to_lo()
1644 *tail = tail.to(to_span);
1645 last_merged_i = Some(i);
1647 bug!("another bound-span visited earlier");
1651 // When we find a non-inferable bound, subsequent inferable bounds
1652 // won't be consecutive from the start (and we'll eat the leading
1653 // `+` rather than the trailing one)
1655 merged.push(bounds[i-1].span().shrink_to_hi().to(bound_span));
1656 last_merged_i = Some(i);
1665 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1666 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
1667 use rustc::middle::resolve_lifetime::Region;
1669 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1670 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1671 if let hir::ItemKind::Struct(_, ref hir_generics)
1672 | hir::ItemKind::Enum(_, ref hir_generics)
1673 | hir::ItemKind::Union(_, ref hir_generics) = item.node
1675 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
1676 if inferred_outlives.is_empty() {
1680 let ty_generics = cx.tcx.generics_of(def_id);
1682 let mut bound_count = 0;
1683 let mut lint_spans = Vec::new();
1685 for param in &hir_generics.params {
1686 let has_lifetime_bounds = param.bounds.iter().any(|bound| {
1687 if let hir::GenericBound::Outlives(_) = bound {
1693 if !has_lifetime_bounds {
1697 let relevant_lifetimes = self.collect_outlived_lifetimes(
1703 if relevant_lifetimes.is_empty() {
1707 let bound_spans = self.collect_outlives_bound_spans(
1708 cx.tcx, ¶m.bounds, &relevant_lifetimes, infer_static,
1710 bound_count += bound_spans.len();
1712 self.consolidate_outlives_bound_spans(
1713 param.span.shrink_to_hi(), ¶m.bounds, bound_spans
1718 let mut where_lint_spans = Vec::new();
1719 let mut dropped_predicate_count = 0;
1720 let num_predicates = hir_generics.where_clause.predicates.len();
1721 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
1722 let (relevant_lifetimes, bounds, span) = match where_predicate {
1723 hir::WherePredicate::RegionPredicate(predicate) => {
1724 if let Some(Region::EarlyBound(index, ..))
1725 = cx.tcx.named_region(predicate.lifetime.hir_id)
1728 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
1736 hir::WherePredicate::BoundPredicate(predicate) => {
1737 // FIXME we can also infer bounds on associated types,
1738 // and should check for them here.
1739 match predicate.bounded_ty.node {
1740 hir::TyKind::Path(hir::QPath::Resolved(
1744 if let Res::Def(DefKind::TyParam, def_id) = path.res {
1745 let index = ty_generics.param_def_id_to_index[&def_id];
1747 Self::lifetimes_outliving_type(inferred_outlives, index),
1760 if relevant_lifetimes.is_empty() {
1764 let bound_spans = self.collect_outlives_bound_spans(
1765 cx.tcx, bounds, &relevant_lifetimes, infer_static,
1767 bound_count += bound_spans.len();
1769 let drop_predicate = bound_spans.len() == bounds.len();
1771 dropped_predicate_count += 1;
1774 // If all the bounds on a predicate were inferable and there are
1775 // further predicates, we want to eat the trailing comma.
1776 if drop_predicate && i + 1 < num_predicates {
1777 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
1778 where_lint_spans.push(
1779 span.to(next_predicate_span.shrink_to_lo())
1782 where_lint_spans.extend(
1783 self.consolidate_outlives_bound_spans(
1784 span.shrink_to_lo(),
1792 // If all predicates are inferable, drop the entire clause
1793 // (including the `where`)
1794 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1795 let where_span = hir_generics.where_clause.span()
1796 .expect("span of (nonempty) where clause should exist");
1797 // Extend the where clause back to the closing `>` of the
1798 // generics, except for tuple struct, which have the `where`
1799 // after the fields of the struct.
1800 let full_where_span = if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _)
1805 hir_generics.span.shrink_to_hi().to(where_span)
1811 lint_spans.extend(where_lint_spans);
1814 if !lint_spans.is_empty() {
1815 let mut err = cx.struct_span_lint(
1816 EXPLICIT_OUTLIVES_REQUIREMENTS,
1818 "outlives requirements can be inferred"
1820 err.multipart_suggestion(
1821 if bound_count == 1 {
1824 "remove these bounds"
1826 lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1827 Applicability::MachineApplicable