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 `LintPass`, you will also need to add it to the
17 //! `add_builtin!` or `add_builtin_with_new!` invocation in `lib.rs`.
18 //! Use the former for unit-like structs and the latter for structs with
21 use rustc::hir::def::Def;
22 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
23 use rustc::ty::{self, Ty};
24 use rustc::{lint, util};
26 use util::nodemap::NodeSet;
27 use lint::{LateContext, LintContext, LintArray};
28 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
30 use rustc::util::nodemap::FxHashSet;
32 use syntax::tokenstream::{TokenTree, TokenStream};
35 use syntax::ast::Expr;
37 use syntax::source_map::Spanned;
38 use syntax::edition::Edition;
39 use syntax::feature_gate::{AttributeGate, AttributeTemplate, AttributeType};
40 use syntax::feature_gate::{Stability, deprecated_attributes};
41 use syntax_pos::{BytePos, Span, SyntaxContext};
42 use syntax::symbol::keywords;
43 use syntax::errors::{Applicability, DiagnosticBuilder};
44 use syntax::print::pprust::expr_to_string;
45 use syntax::visit::FnKind;
46 use syntax::struct_span_err;
48 use rustc::hir::{self, GenericParamKind, PatKind};
50 use crate::nonstandard_style::{MethodLateContext, method_context};
54 // hardwired lints from librustc
55 pub use lint::builtin::*;
60 "suggest using `loop { }` instead of `while true { }`"
63 #[derive(Copy, Clone)]
66 impl LintPass for WhileTrue {
67 fn name(&self) -> &'static str {
71 fn get_lints(&self) -> LintArray {
72 lint_array!(WHILE_TRUE)
76 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for WhileTrue {
77 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
78 if let hir::ExprKind::While(ref cond, ..) = e.node {
79 if let hir::ExprKind::Lit(ref lit) = cond.node {
80 if let ast::LitKind::Bool(true) = lit.node {
81 if lit.span.ctxt() == SyntaxContext::empty() {
82 let msg = "denote infinite loops with `loop { ... }`";
83 let condition_span = cx.tcx.sess.source_map().def_span(e.span);
84 let mut err = cx.struct_span_lint(WHILE_TRUE, condition_span, msg);
85 err.span_suggestion_short(
89 Applicability::MachineApplicable
102 "use of owned (Box type) heap memory"
105 #[derive(Copy, Clone)]
106 pub struct BoxPointers;
109 fn check_heap_type<'a, 'tcx>(&self, cx: &LateContext<'_, '_>, span: Span, ty: Ty<'_>) {
110 for leaf_ty in ty.walk() {
111 if leaf_ty.is_box() {
112 let m = format!("type uses owned (Box type) pointers: {}", ty);
113 cx.span_lint(BOX_POINTERS, span, &m);
119 impl LintPass for BoxPointers {
120 fn name(&self) -> &'static str {
124 fn get_lints(&self) -> LintArray {
125 lint_array!(BOX_POINTERS)
129 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoxPointers {
130 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
132 hir::ItemKind::Fn(..) |
133 hir::ItemKind::Ty(..) |
134 hir::ItemKind::Enum(..) |
135 hir::ItemKind::Struct(..) |
136 hir::ItemKind::Union(..) => {
137 let def_id = cx.tcx.hir().local_def_id(it.id);
138 self.check_heap_type(cx, it.span, cx.tcx.type_of(def_id))
143 // If it's a struct, we also have to check the fields' types
145 hir::ItemKind::Struct(ref struct_def, _) |
146 hir::ItemKind::Union(ref struct_def, _) => {
147 for struct_field in struct_def.fields() {
148 let def_id = cx.tcx.hir().local_def_id(struct_field.id);
149 self.check_heap_type(cx, struct_field.span,
150 cx.tcx.type_of(def_id));
157 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
158 let ty = cx.tables.node_id_to_type(e.hir_id);
159 self.check_heap_type(cx, e.span, ty);
164 NON_SHORTHAND_FIELD_PATTERNS,
166 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
169 #[derive(Copy, Clone)]
170 pub struct NonShorthandFieldPatterns;
172 impl LintPass for NonShorthandFieldPatterns {
173 fn name(&self) -> &'static str {
174 "NonShorthandFieldPatterns"
177 fn get_lints(&self) -> LintArray {
178 lint_array!(NON_SHORTHAND_FIELD_PATTERNS)
182 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
183 fn check_pat(&mut self, cx: &LateContext<'_, '_>, pat: &hir::Pat) {
184 if let PatKind::Struct(ref qpath, ref field_pats, _) = pat.node {
185 let variant = cx.tables.pat_ty(pat).ty_adt_def()
186 .expect("struct pattern type is not an ADT")
187 .variant_of_def(cx.tables.qpath_def(qpath, pat.hir_id));
188 for fieldpat in field_pats {
189 if fieldpat.node.is_shorthand {
192 if fieldpat.span.ctxt().outer().expn_info().is_some() {
193 // Don't lint if this is a macro expansion: macro authors
194 // shouldn't have to worry about this kind of style issue
198 if let PatKind::Binding(_, _, _, ident, None) = fieldpat.node.pat.node {
199 if cx.tcx.find_field_index(ident, &variant) ==
200 Some(cx.tcx.field_index(fieldpat.node.id, cx.tables)) {
201 let mut err = cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS,
203 &format!("the `{}:` in this pattern is redundant", ident));
204 let subspan = cx.tcx.sess.source_map().span_through_char(fieldpat.span,
206 err.span_suggestion_short(
210 Applicability::MachineApplicable
223 "usage of `unsafe` code"
226 #[derive(Copy, Clone)]
227 pub struct UnsafeCode;
229 impl LintPass for UnsafeCode {
230 fn name(&self) -> &'static str {
234 fn get_lints(&self) -> LintArray {
235 lint_array!(UNSAFE_CODE)
240 fn report_unsafe(&self, cx: &EarlyContext<'_>, span: Span, desc: &'static str) {
241 // This comes from a macro that has #[allow_internal_unsafe].
242 if span.allows_unsafe() {
246 cx.span_lint(UNSAFE_CODE, span, desc);
250 impl EarlyLintPass for UnsafeCode {
251 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
252 if attr.check_name("allow_internal_unsafe") {
253 self.report_unsafe(cx, attr.span, "`allow_internal_unsafe` allows defining \
254 macros using unsafe without triggering \
255 the `unsafe_code` lint at their call site");
259 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
260 if let ast::ExprKind::Block(ref blk, _) = e.node {
261 // Don't warn about generated blocks, that'll just pollute the output.
262 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
263 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");
268 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
270 ast::ItemKind::Trait(_, ast::Unsafety::Unsafe, ..) => {
271 self.report_unsafe(cx, it.span, "declaration of an `unsafe` trait")
274 ast::ItemKind::Impl(ast::Unsafety::Unsafe, ..) => {
275 self.report_unsafe(cx, it.span, "implementation of an `unsafe` trait")
282 fn check_fn(&mut self,
283 cx: &EarlyContext<'_>,
289 FnKind::ItemFn(_, ast::FnHeader { unsafety: ast::Unsafety::Unsafe, .. }, ..) => {
290 self.report_unsafe(cx, span, "declaration of an `unsafe` function")
293 FnKind::Method(_, sig, ..) => {
294 if sig.header.unsafety == ast::Unsafety::Unsafe {
295 self.report_unsafe(cx, span, "implementation of an `unsafe` method")
303 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, item: &ast::TraitItem) {
304 if let ast::TraitItemKind::Method(ref sig, None) = item.node {
305 if sig.header.unsafety == ast::Unsafety::Unsafe {
306 self.report_unsafe(cx, item.span, "declaration of an `unsafe` method")
315 "detects missing documentation for public members",
316 report_in_external_macro: true
319 pub struct MissingDoc {
320 /// Stack of whether #[doc(hidden)] is set
321 /// at each level which has lint attributes.
322 doc_hidden_stack: Vec<bool>,
324 /// Private traits or trait items that leaked through. Don't check their methods.
325 private_traits: FxHashSet<ast::NodeId>,
328 fn has_doc(attr: &ast::Attribute) -> bool {
329 if !attr.check_name("doc") {
333 if attr.is_value_str() {
337 if let Some(list) = attr.meta_item_list() {
339 if meta.check_name("include") || meta.check_name("hidden") {
349 pub fn new() -> MissingDoc {
351 doc_hidden_stack: vec![false],
352 private_traits: FxHashSet::default(),
356 fn doc_hidden(&self) -> bool {
357 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
360 fn check_missing_docs_attrs(&self,
361 cx: &LateContext<'_, '_>,
362 id: Option<ast::NodeId>,
363 attrs: &[ast::Attribute],
365 desc: &'static str) {
366 // If we're building a test harness, then warning about
367 // documentation is probably not really relevant right now.
368 if cx.sess().opts.test {
372 // `#[doc(hidden)]` disables missing_docs check.
373 if self.doc_hidden() {
377 // Only check publicly-visible items, using the result from the privacy pass.
378 // It's an option so the crate root can also use this function (it doesn't
380 if let Some(id) = id {
381 if !cx.access_levels.is_exported(id) {
386 let has_doc = attrs.iter().any(|a| has_doc(a));
388 cx.span_lint(MISSING_DOCS,
389 cx.tcx.sess.source_map().def_span(sp),
390 &format!("missing documentation for {}", desc));
395 impl LintPass for MissingDoc {
396 fn name(&self) -> &'static str {
400 fn get_lints(&self) -> LintArray {
401 lint_array!(MISSING_DOCS)
405 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDoc {
406 fn enter_lint_attrs(&mut self, _: &LateContext<'_, '_>, attrs: &[ast::Attribute]) {
407 let doc_hidden = self.doc_hidden() ||
408 attrs.iter().any(|attr| {
409 attr.check_name("doc") &&
410 match attr.meta_item_list() {
412 Some(l) => attr::list_contains_name(&l, "hidden"),
415 self.doc_hidden_stack.push(doc_hidden);
418 fn exit_lint_attrs(&mut self, _: &LateContext<'_, '_>, _attrs: &[ast::Attribute]) {
419 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
422 fn check_crate(&mut self, cx: &LateContext<'_, '_>, krate: &hir::Crate) {
423 self.check_missing_docs_attrs(cx, None, &krate.attrs, krate.span, "crate");
425 for macro_def in &krate.exported_macros {
426 let has_doc = macro_def.attrs.iter().any(|a| has_doc(a));
428 cx.span_lint(MISSING_DOCS,
429 cx.tcx.sess.source_map().def_span(macro_def.span),
430 "missing documentation for macro");
435 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
436 let desc = match it.node {
437 hir::ItemKind::Fn(..) => "a function",
438 hir::ItemKind::Mod(..) => "a module",
439 hir::ItemKind::Enum(..) => "an enum",
440 hir::ItemKind::Struct(..) => "a struct",
441 hir::ItemKind::Union(..) => "a union",
442 hir::ItemKind::Trait(.., ref trait_item_refs) => {
443 // Issue #11592, traits are always considered exported, even when private.
444 if let hir::VisibilityKind::Inherited = it.vis.node {
445 self.private_traits.insert(it.id);
446 for trait_item_ref in trait_item_refs {
447 self.private_traits.insert(trait_item_ref.id.node_id);
453 hir::ItemKind::Ty(..) => "a type alias",
454 hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) => {
455 // If the trait is private, add the impl items to private_traits so they don't get
456 // reported for missing docs.
457 let real_trait = trait_ref.path.def.def_id();
458 if let Some(node_id) = cx.tcx.hir().as_local_node_id(real_trait) {
459 match cx.tcx.hir().find(node_id) {
460 Some(Node::Item(item)) => {
461 if let hir::VisibilityKind::Inherited = item.vis.node {
462 for impl_item_ref in impl_item_refs {
463 self.private_traits.insert(impl_item_ref.id.node_id);
472 hir::ItemKind::Const(..) => "a constant",
473 hir::ItemKind::Static(..) => "a static",
477 self.check_missing_docs_attrs(cx, Some(it.id), &it.attrs, it.span, desc);
480 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, trait_item: &hir::TraitItem) {
481 if self.private_traits.contains(&trait_item.id) {
485 let desc = match trait_item.node {
486 hir::TraitItemKind::Const(..) => "an associated constant",
487 hir::TraitItemKind::Method(..) => "a trait method",
488 hir::TraitItemKind::Type(..) => "an associated type",
491 self.check_missing_docs_attrs(cx,
498 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
499 // If the method is an impl for a trait, don't doc.
500 if method_context(cx, impl_item.id) == MethodLateContext::TraitImpl {
504 let desc = match impl_item.node {
505 hir::ImplItemKind::Const(..) => "an associated constant",
506 hir::ImplItemKind::Method(..) => "a method",
507 hir::ImplItemKind::Type(_) => "an associated type",
508 hir::ImplItemKind::Existential(_) => "an associated existential type",
510 self.check_missing_docs_attrs(cx,
517 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, sf: &hir::StructField) {
518 if !sf.is_positional() {
519 self.check_missing_docs_attrs(cx,
527 fn check_variant(&mut self, cx: &LateContext<'_, '_>, v: &hir::Variant, _: &hir::Generics) {
528 self.check_missing_docs_attrs(cx,
529 Some(v.node.data.id()),
537 pub MISSING_COPY_IMPLEMENTATIONS,
539 "detects potentially-forgotten implementations of `Copy`"
542 #[derive(Copy, Clone)]
543 pub struct MissingCopyImplementations;
545 impl LintPass for MissingCopyImplementations {
546 fn name(&self) -> &'static str {
547 "MissingCopyImplementations"
550 fn get_lints(&self) -> LintArray {
551 lint_array!(MISSING_COPY_IMPLEMENTATIONS)
555 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
556 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
557 if !cx.access_levels.is_reachable(item.id) {
560 let (def, ty) = match item.node {
561 hir::ItemKind::Struct(_, ref ast_generics) => {
562 if !ast_generics.params.is_empty() {
565 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.id));
566 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
568 hir::ItemKind::Union(_, ref ast_generics) => {
569 if !ast_generics.params.is_empty() {
572 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.id));
573 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
575 hir::ItemKind::Enum(_, ref ast_generics) => {
576 if !ast_generics.params.is_empty() {
579 let def = cx.tcx.adt_def(cx.tcx.hir().local_def_id(item.id));
580 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
584 if def.has_dtor(cx.tcx) {
587 let param_env = ty::ParamEnv::empty();
588 if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
591 if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
592 cx.span_lint(MISSING_COPY_IMPLEMENTATIONS,
594 "type could implement `Copy`; consider adding `impl \
601 MISSING_DEBUG_IMPLEMENTATIONS,
603 "detects missing implementations of fmt::Debug"
606 pub struct MissingDebugImplementations {
607 impling_types: Option<NodeSet>,
610 impl MissingDebugImplementations {
611 pub fn new() -> MissingDebugImplementations {
612 MissingDebugImplementations { impling_types: None }
616 impl LintPass for MissingDebugImplementations {
617 fn name(&self) -> &'static str {
618 "MissingDebugImplementations"
621 fn get_lints(&self) -> LintArray {
622 lint_array!(MISSING_DEBUG_IMPLEMENTATIONS)
626 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
627 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
628 if !cx.access_levels.is_reachable(item.id) {
633 hir::ItemKind::Struct(..) |
634 hir::ItemKind::Union(..) |
635 hir::ItemKind::Enum(..) => {}
639 let debug = match cx.tcx.lang_items().debug_trait() {
640 Some(debug) => debug,
644 if self.impling_types.is_none() {
645 let mut impls = NodeSet::default();
646 cx.tcx.for_each_impl(debug, |d| {
647 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
648 if let Some(node_id) = cx.tcx.hir().as_local_node_id(ty_def.did) {
649 impls.insert(node_id);
654 self.impling_types = Some(impls);
655 debug!("{:?}", self.impling_types);
658 if !self.impling_types.as_ref().unwrap().contains(&item.id) {
659 cx.span_lint(MISSING_DEBUG_IMPLEMENTATIONS,
661 "type does not implement `fmt::Debug`; consider adding #[derive(Debug)] \
662 or a manual implementation")
668 pub ANONYMOUS_PARAMETERS,
670 "detects anonymous parameters"
673 /// Checks for use of anonymous parameters (RFC 1685)
675 pub struct AnonymousParameters;
677 impl LintPass for AnonymousParameters {
678 fn name(&self) -> &'static str {
679 "AnonymousParameters"
682 fn get_lints(&self) -> LintArray {
683 lint_array!(ANONYMOUS_PARAMETERS)
687 impl EarlyLintPass for AnonymousParameters {
688 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::TraitItem) {
690 ast::TraitItemKind::Method(ref sig, _) => {
691 for arg in sig.decl.inputs.iter() {
693 ast::PatKind::Ident(_, ident, None) => {
694 if ident.name == keywords::Invalid.name() {
698 .span_to_snippet(arg.ty.span);
700 let (ty_snip, appl) = if let Ok(snip) = ty_snip {
701 (snip, Applicability::MachineApplicable)
703 ("<type>".to_owned(), Applicability::HasPlaceholders)
707 ANONYMOUS_PARAMETERS,
709 "anonymous parameters are deprecated and will be \
710 removed in the next edition."
713 "Try naming the parameter or explicitly \
715 format!("_: {}", ty_snip),
729 /// Checks for use of attributes which have been deprecated.
731 pub struct DeprecatedAttr {
732 // This is not free to compute, so we want to keep it around, rather than
733 // compute it for every attribute.
734 depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeTemplate, AttributeGate)>,
737 impl DeprecatedAttr {
738 pub fn new() -> DeprecatedAttr {
740 depr_attrs: deprecated_attributes(),
745 impl LintPass for DeprecatedAttr {
746 fn name(&self) -> &'static str {
750 fn get_lints(&self) -> LintArray {
755 impl EarlyLintPass for DeprecatedAttr {
756 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
757 for &&(n, _, _, ref g) in &self.depr_attrs {
758 if attr.name() == n {
759 if let &AttributeGate::Gated(Stability::Deprecated(link, suggestion),
763 let msg = format!("use of deprecated attribute `{}`: {}. See {}",
765 let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
766 err.span_suggestion_short(
768 suggestion.unwrap_or("remove this attribute"),
770 Applicability::MachineApplicable
781 pub UNUSED_DOC_COMMENTS,
783 "detects doc comments that aren't used by rustdoc"
786 #[derive(Copy, Clone)]
787 pub struct UnusedDocComment;
789 impl LintPass for UnusedDocComment {
790 fn name(&self) -> &'static str {
794 fn get_lints(&self) -> LintArray {
795 lint_array![UNUSED_DOC_COMMENTS]
799 impl UnusedDocComment {
800 fn warn_if_doc<'a, 'tcx,
801 I: Iterator<Item=&'a ast::Attribute>,
802 C: LintContext<'tcx>>(&self, mut attrs: I, cx: &C) {
803 if let Some(attr) = attrs.find(|a| a.is_value_str() && a.check_name("doc")) {
804 cx.struct_span_lint(UNUSED_DOC_COMMENTS, attr.span, "doc comment not used by rustdoc")
810 impl EarlyLintPass for UnusedDocComment {
811 fn check_local(&mut self, cx: &EarlyContext<'_>, decl: &ast::Local) {
812 self.warn_if_doc(decl.attrs.iter(), cx);
815 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
816 self.warn_if_doc(arm.attrs.iter(), cx);
819 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
820 self.warn_if_doc(expr.attrs.iter(), cx);
827 "compiler plugin used as ordinary library in non-plugin crate"
830 #[derive(Copy, Clone)]
831 pub struct PluginAsLibrary;
833 impl LintPass for PluginAsLibrary {
834 fn name(&self) -> &'static str {
838 fn get_lints(&self) -> LintArray {
839 lint_array![PLUGIN_AS_LIBRARY]
843 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
844 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
845 if cx.tcx.plugin_registrar_fn(LOCAL_CRATE).is_some() {
846 // We're compiling a plugin; it's fine to link other plugins.
851 hir::ItemKind::ExternCrate(..) => (),
855 let def_id = cx.tcx.hir().local_def_id(it.id);
856 let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
857 Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
859 // Probably means we aren't linking the crate for some reason.
861 // Not sure if / when this could happen.
867 cx.span_lint(PLUGIN_AS_LIBRARY,
869 "compiler plugin used as an ordinary library");
875 NO_MANGLE_CONST_ITEMS,
877 "const items will not have their symbols exported"
881 NO_MANGLE_GENERIC_ITEMS,
883 "generic items must be mangled"
886 #[derive(Copy, Clone)]
887 pub struct InvalidNoMangleItems;
889 impl LintPass for InvalidNoMangleItems {
890 fn name(&self) -> &'static str {
891 "InvalidNoMangleItems"
894 fn get_lints(&self) -> LintArray {
895 lint_array!(NO_MANGLE_CONST_ITEMS,
896 NO_MANGLE_GENERIC_ITEMS)
900 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
901 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
903 hir::ItemKind::Fn(.., ref generics, _) => {
904 if let Some(no_mangle_attr) = attr::find_by_name(&it.attrs, "no_mangle") {
905 for param in &generics.params {
907 GenericParamKind::Lifetime { .. } => {}
908 GenericParamKind::Type { .. } => {
909 let mut err = cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS,
911 "functions generic over \
912 types must be mangled");
913 err.span_suggestion_short(
915 "remove this attribute",
917 // Use of `#[no_mangle]` suggests FFI intent; correct
918 // fix may be to monomorphize source by hand
919 Applicability::MaybeIncorrect
928 hir::ItemKind::Const(..) => {
929 if attr::contains_name(&it.attrs, "no_mangle") {
930 // Const items do not refer to a particular location in memory, and therefore
931 // don't have anything to attach a symbol to
932 let msg = "const items should never be #[no_mangle]";
933 let mut err = cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, msg);
935 // account for "pub const" (#45562)
936 let start = cx.tcx.sess.source_map().span_to_snippet(it.span)
937 .map(|snippet| snippet.find("const").unwrap_or(0))
938 .unwrap_or(0) as u32;
939 // `const` is 5 chars
940 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
943 "try a static value",
944 "pub static".to_owned(),
945 Applicability::MachineApplicable
955 #[derive(Clone, Copy)]
956 pub struct MutableTransmutes;
961 "mutating transmuted &mut T from &T may cause undefined behavior"
964 impl LintPass for MutableTransmutes {
965 fn name(&self) -> &'static str {
969 fn get_lints(&self) -> LintArray {
970 lint_array!(MUTABLE_TRANSMUTES)
974 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
975 fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &hir::Expr) {
976 use rustc_target::spec::abi::Abi::RustIntrinsic;
978 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
979 consider instead using an UnsafeCell";
980 match get_transmute_from_to(cx, expr) {
981 Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) => {
982 if to_mt == hir::Mutability::MutMutable &&
983 from_mt == hir::Mutability::MutImmutable {
984 cx.span_lint(MUTABLE_TRANSMUTES, expr.span, msg);
990 fn get_transmute_from_to<'a, 'tcx>
991 (cx: &LateContext<'a, 'tcx>,
993 -> Option<(&'tcx ty::TyKind<'tcx>, &'tcx ty::TyKind<'tcx>)> {
994 let def = if let hir::ExprKind::Path(ref qpath) = expr.node {
995 cx.tables.qpath_def(qpath, expr.hir_id)
999 if let Def::Fn(did) = def {
1000 if !def_id_is_transmute(cx, did) {
1003 let sig = cx.tables.node_id_to_type(expr.hir_id).fn_sig(cx.tcx);
1004 let from = sig.inputs().skip_binder()[0];
1005 let to = *sig.output().skip_binder();
1006 return Some((&from.sty, &to.sty));
1011 fn def_id_is_transmute(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
1012 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic &&
1013 cx.tcx.item_name(def_id) == "transmute"
1018 /// Forbids using the `#[feature(...)]` attribute
1019 #[derive(Copy, Clone)]
1020 pub struct UnstableFeatures;
1025 "enabling unstable features (deprecated. do not use)"
1028 impl LintPass for UnstableFeatures {
1029 fn name(&self) -> &'static str {
1033 fn get_lints(&self) -> LintArray {
1034 lint_array!(UNSTABLE_FEATURES)
1038 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnstableFeatures {
1039 fn check_attribute(&mut self, ctx: &LateContext<'_, '_>, attr: &ast::Attribute) {
1040 if attr.check_name("feature") {
1041 if let Some(items) = attr.meta_item_list() {
1043 ctx.span_lint(UNSTABLE_FEATURES, item.span(), "unstable feature");
1050 /// Lint for unions that contain fields with possibly non-trivial destructors.
1051 pub struct UnionsWithDropFields;
1054 UNIONS_WITH_DROP_FIELDS,
1056 "use of unions that contain fields with possibly non-trivial drop code"
1059 impl LintPass for UnionsWithDropFields {
1060 fn name(&self) -> &'static str {
1061 "UnionsWithDropFields"
1064 fn get_lints(&self) -> LintArray {
1065 lint_array!(UNIONS_WITH_DROP_FIELDS)
1069 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
1070 fn check_item(&mut self, ctx: &LateContext<'_, '_>, item: &hir::Item) {
1071 if let hir::ItemKind::Union(ref vdata, _) = item.node {
1072 for field in vdata.fields() {
1073 let field_ty = ctx.tcx.type_of(ctx.tcx.hir().local_def_id(field.id));
1074 if field_ty.needs_drop(ctx.tcx, ctx.param_env) {
1075 ctx.span_lint(UNIONS_WITH_DROP_FIELDS,
1077 "union contains a field with possibly non-trivial drop code, \
1078 drop code of union fields is ignored when dropping the union");
1086 /// Lint for items marked `pub` that aren't reachable from other crates
1087 pub struct UnreachablePub;
1090 pub UNREACHABLE_PUB,
1092 "`pub` items not reachable from crate root"
1095 impl LintPass for UnreachablePub {
1096 fn name(&self) -> &'static str {
1100 fn get_lints(&self) -> LintArray {
1101 lint_array!(UNREACHABLE_PUB)
1105 impl UnreachablePub {
1106 fn perform_lint(&self, cx: &LateContext<'_, '_>, what: &str, id: ast::NodeId,
1107 vis: &hir::Visibility, span: Span, exportable: bool) {
1108 let mut applicability = Applicability::MachineApplicable;
1110 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
1111 if span.ctxt().outer().expn_info().is_some() {
1112 applicability = Applicability::MaybeIncorrect;
1114 let def_span = cx.tcx.sess.source_map().def_span(span);
1115 let mut err = cx.struct_span_lint(UNREACHABLE_PUB, def_span,
1116 &format!("unreachable `pub` {}", what));
1117 let replacement = if cx.tcx.features().crate_visibility_modifier {
1123 err.span_suggestion(
1125 "consider restricting its visibility",
1130 err.help("or consider exporting it for use by other crates");
1140 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnreachablePub {
1141 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1142 self.perform_lint(cx, "item", item.id, &item.vis, item.span, true);
1145 fn check_foreign_item(&mut self, cx: &LateContext<'_, '_>, foreign_item: &hir::ForeignItem) {
1146 self.perform_lint(cx, "item", foreign_item.id, &foreign_item.vis,
1147 foreign_item.span, true);
1150 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
1151 self.perform_lint(cx, "field", field.id, &field.vis, field.span, false);
1154 fn check_impl_item(&mut self, cx: &LateContext<'_, '_>, impl_item: &hir::ImplItem) {
1155 self.perform_lint(cx, "item", impl_item.id, &impl_item.vis, impl_item.span, false);
1159 /// Lint for trait and lifetime bounds in type aliases being mostly ignored:
1160 /// They are relevant when using associated types, but otherwise neither checked
1161 /// at definition site nor enforced at use site.
1163 pub struct TypeAliasBounds;
1168 "bounds in type aliases are not enforced"
1171 impl LintPass for TypeAliasBounds {
1172 fn name(&self) -> &'static str {
1176 fn get_lints(&self) -> LintArray {
1177 lint_array!(TYPE_ALIAS_BOUNDS)
1181 impl TypeAliasBounds {
1182 fn is_type_variable_assoc(qpath: &hir::QPath) -> bool {
1184 hir::QPath::TypeRelative(ref ty, _) => {
1185 // If this is a type variable, we found a `T::Assoc`.
1187 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1189 Def::TyParam(_) => true,
1196 hir::QPath::Resolved(..) => false,
1200 fn suggest_changing_assoc_types(ty: &hir::Ty, err: &mut DiagnosticBuilder<'_>) {
1201 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1202 // bound. Let's see if this type does that.
1204 // We use a HIR visitor to walk the type.
1205 use rustc::hir::intravisit::{self, Visitor};
1206 struct WalkAssocTypes<'a, 'db> where 'db: 'a {
1207 err: &'a mut DiagnosticBuilder<'db>
1209 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1210 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v>
1212 intravisit::NestedVisitorMap::None
1215 fn visit_qpath(&mut self, qpath: &'v hir::QPath, id: hir::HirId, span: Span) {
1216 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1217 self.err.span_help(span,
1218 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1219 associated types in type aliases");
1221 intravisit::walk_qpath(self, qpath, id, span)
1225 // Let's go for a walk!
1226 let mut visitor = WalkAssocTypes { err };
1227 visitor.visit_ty(ty);
1231 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeAliasBounds {
1232 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &hir::Item) {
1233 let (ty, type_alias_generics) = match item.node {
1234 hir::ItemKind::Ty(ref ty, ref generics) => (&*ty, generics),
1237 let mut suggested_changing_assoc_types = false;
1238 // There must not be a where clause
1239 if !type_alias_generics.where_clause.predicates.is_empty() {
1240 let spans : Vec<_> = type_alias_generics.where_clause.predicates.iter()
1241 .map(|pred| pred.span()).collect();
1242 let mut err = cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans,
1243 "where clauses are not enforced in type aliases");
1244 err.help("the clause will not be checked when the type alias is used, \
1245 and should be removed");
1246 if !suggested_changing_assoc_types {
1247 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1248 suggested_changing_assoc_types = true;
1252 // The parameters must not have bounds
1253 for param in type_alias_generics.params.iter() {
1254 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1255 if !spans.is_empty() {
1256 let mut err = cx.struct_span_lint(
1259 "bounds on generic parameters are not enforced in type aliases",
1261 err.help("the bound will not be checked when the type alias is used, \
1262 and should be removed");
1263 if !suggested_changing_assoc_types {
1264 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1265 suggested_changing_assoc_types = true;
1273 /// Lint constants that are erroneous.
1274 /// Without this lint, we might not get any diagnostic if the constant is
1275 /// unused within this crate, even though downstream crates can't use it
1276 /// without producing an error.
1277 pub struct UnusedBrokenConst;
1279 impl LintPass for UnusedBrokenConst {
1280 fn name(&self) -> &'static str {
1284 fn get_lints(&self) -> LintArray {
1288 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
1289 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
1290 let is_static = cx.tcx.is_static(def_id).is_some();
1291 let param_env = if is_static {
1292 // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
1293 ty::ParamEnv::reveal_all()
1295 cx.tcx.param_env(def_id)
1297 let cid = ::rustc::mir::interpret::GlobalId {
1298 instance: ty::Instance::mono(cx.tcx, def_id),
1301 // trigger the query once for all constants since that will already report the errors
1302 let _ = cx.tcx.const_eval(param_env.and(cid));
1305 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
1306 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1308 hir::ItemKind::Const(_, body_id) => {
1309 check_const(cx, body_id);
1311 hir::ItemKind::Static(_, _, body_id) => {
1312 check_const(cx, body_id);
1319 /// Lint for trait and lifetime bounds that don't depend on type parameters
1320 /// which either do nothing, or stop the item from being used.
1321 pub struct TrivialConstraints;
1326 "these bounds don't depend on an type parameters"
1329 impl LintPass for TrivialConstraints {
1330 fn name(&self) -> &'static str {
1331 "TrivialConstraints"
1334 fn get_lints(&self) -> LintArray {
1335 lint_array!(TRIVIAL_BOUNDS)
1339 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
1342 cx: &LateContext<'a, 'tcx>,
1343 item: &'tcx hir::Item,
1345 use rustc::ty::fold::TypeFoldable;
1346 use rustc::ty::Predicate::*;
1349 if cx.tcx.features().trivial_bounds {
1350 let def_id = cx.tcx.hir().local_def_id(item.id);
1351 let predicates = cx.tcx.predicates_of(def_id);
1352 for &(predicate, span) in &predicates.predicates {
1353 let predicate_kind_name = match predicate {
1354 Trait(..) => "Trait",
1356 RegionOutlives(..) => "Lifetime",
1358 // Ignore projections, as they can only be global
1359 // if the trait bound is global
1361 // Ignore bounds that a user can't type
1366 ConstEvaluatable(..) => continue,
1368 if predicate.is_global() {
1372 &format!("{} bound {} does not depend on any type \
1373 or lifetime parameters", predicate_kind_name, predicate),
1382 /// Does nothing as a lint pass, but registers some `Lint`s
1383 /// which are used by other parts of the compiler.
1384 #[derive(Copy, Clone)]
1385 pub struct SoftLints;
1387 impl LintPass for SoftLints {
1388 fn name(&self) -> &'static str {
1392 fn get_lints(&self) -> LintArray {
1396 NON_SHORTHAND_FIELD_PATTERNS,
1399 MISSING_COPY_IMPLEMENTATIONS,
1400 MISSING_DEBUG_IMPLEMENTATIONS,
1401 ANONYMOUS_PARAMETERS,
1402 UNUSED_DOC_COMMENTS,
1404 NO_MANGLE_CONST_ITEMS,
1405 NO_MANGLE_GENERIC_ITEMS,
1408 UNIONS_WITH_DROP_FIELDS,
1417 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1419 "`...` range patterns are deprecated"
1423 pub struct EllipsisInclusiveRangePatterns;
1425 impl LintPass for EllipsisInclusiveRangePatterns {
1426 fn name(&self) -> &'static str {
1427 "EllipsisInclusiveRangePatterns"
1430 fn get_lints(&self) -> LintArray {
1431 lint_array!(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS)
1435 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1436 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat, visit_subpats: &mut bool) {
1437 use self::ast::{PatKind, RangeEnd, RangeSyntax::DotDotDot};
1439 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1440 /// corresponding to the ellipsis.
1441 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(&P<Expr>, &P<Expr>, Span)> {
1443 PatKind::Range(a, b, Spanned { span, node: RangeEnd::Included(DotDotDot), .. }) => {
1450 let (parenthesise, endpoints) = match &pat.node {
1451 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1452 _ => (false, matches_ellipsis_pat(pat)),
1455 if let Some((start, end, join)) = endpoints {
1456 let msg = "`...` range patterns are deprecated";
1457 let suggestion = "use `..=` for an inclusive range";
1459 *visit_subpats = false;
1460 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg);
1461 err.span_suggestion(
1464 format!("&({}..={})", expr_to_string(&start), expr_to_string(&end)),
1465 Applicability::MachineApplicable,
1469 let mut err = cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg);
1470 err.span_suggestion_short(
1474 Applicability::MachineApplicable,
1483 UNNAMEABLE_TEST_ITEMS,
1485 "detects an item that cannot be named being marked as #[test_case]",
1486 report_in_external_macro: true
1489 pub struct UnnameableTestItems {
1490 boundary: ast::NodeId, // NodeId of the item under which things are not nameable
1491 items_nameable: bool,
1494 impl UnnameableTestItems {
1495 pub fn new() -> Self {
1497 boundary: ast::DUMMY_NODE_ID,
1498 items_nameable: true
1503 impl LintPass for UnnameableTestItems {
1504 fn name(&self) -> &'static str {
1505 "UnnameableTestItems"
1508 fn get_lints(&self) -> LintArray {
1509 lint_array!(UNNAMEABLE_TEST_ITEMS)
1513 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
1514 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1515 if self.items_nameable {
1516 if let hir::ItemKind::Mod(..) = it.node {}
1518 self.items_nameable = false;
1519 self.boundary = it.id;
1524 if let Some(attr) = attr::find_by_name(&it.attrs, "rustc_test_marker") {
1525 cx.struct_span_lint(
1526 UNNAMEABLE_TEST_ITEMS,
1528 "cannot test inner items",
1533 fn check_item_post(&mut self, _cx: &LateContext<'_, '_>, it: &hir::Item) {
1534 if !self.items_nameable && self.boundary == it.id {
1535 self.items_nameable = true;
1543 "detects edition keywords being used as an identifier"
1546 /// Checks for uses of edition keywords used as an identifier
1548 pub struct KeywordIdents;
1550 impl LintPass for KeywordIdents {
1551 fn name(&self) -> &'static str {
1555 fn get_lints(&self) -> LintArray {
1556 lint_array!(KEYWORD_IDENTS)
1560 impl KeywordIdents {
1561 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1562 for tt in tokens.into_trees() {
1564 TokenTree::Token(span, tok) => match tok.ident() {
1565 // only report non-raw idents
1566 Some((ident, false)) => {
1567 self.check_ident(cx, ast::Ident {
1568 span: span.substitute_dummy(ident.span),
1574 TokenTree::Delimited(_, _, tts) => {
1575 self.check_tokens(cx, tts)
1582 impl EarlyLintPass for KeywordIdents {
1583 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
1584 self.check_tokens(cx, mac_def.stream());
1586 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
1587 self.check_tokens(cx, mac.node.tts.clone().into());
1589 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: ast::Ident) {
1590 let ident_str = &ident.as_str()[..];
1591 let cur_edition = cx.sess.edition();
1592 let is_raw_ident = |ident: ast::Ident| {
1593 cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span)
1595 let next_edition = match cur_edition {
1596 Edition::Edition2015 => {
1598 "async" | "try" | "dyn" => Edition::Edition2018,
1599 // Only issue warnings for `await` if the `async_await`
1600 // feature isn't being used. Otherwise, users need
1601 // to keep using `await` for the macro exposed by std.
1602 "await" if !cx.sess.features_untracked().async_await => Edition::Edition2018,
1607 // There are no new keywords yet for the 2018 edition and beyond.
1608 // However, `await` is a "false" keyword in the 2018 edition,
1609 // and can only be used if the `async_await` feature is enabled.
1610 // Otherwise, we emit an error.
1612 if "await" == ident_str
1613 && !cx.sess.features_untracked().async_await
1614 && !is_raw_ident(ident)
1616 let mut err = struct_span_err!(
1620 "`await` is a keyword in the {} edition", cur_edition,
1622 err.span_suggestion(
1624 "you can use a raw identifier to stay compatible",
1625 "r#await".to_string(),
1626 Applicability::MachineApplicable,
1634 // don't lint `r#foo`
1635 if is_raw_ident(ident) {
1639 let mut lint = cx.struct_span_lint(
1642 &format!("`{}` is a keyword in the {} edition",
1646 lint.span_suggestion(
1648 "you can use a raw identifier to stay compatible",
1649 format!("r#{}", ident.as_str()),
1650 Applicability::MachineApplicable,
1657 pub struct ExplicitOutlivesRequirements;
1659 impl LintPass for ExplicitOutlivesRequirements {
1660 fn name(&self) -> &'static str {
1661 "ExplicitOutlivesRequirements"
1664 fn get_lints(&self) -> LintArray {
1665 lint_array![EXPLICIT_OUTLIVES_REQUIREMENTS]
1669 impl ExplicitOutlivesRequirements {
1670 fn collect_outlives_bound_spans(
1672 cx: &LateContext<'_, '_>,
1675 bounds: &hir::GenericBounds,
1677 ) -> Vec<(usize, Span)> {
1678 // For lack of a more elegant strategy for comparing the `ty::Predicate`s
1679 // returned by this query with the params/bounds grabbed from the HIR—and
1680 // with some regrets—we're going to covert the param/lifetime names to
1682 let inferred_outlives = cx.tcx.inferred_outlives_of(item_def_id);
1684 let ty_lt_names = inferred_outlives.iter().filter_map(|pred| {
1685 let binder = match pred {
1686 ty::Predicate::TypeOutlives(binder) => binder,
1687 _ => { return None; }
1689 let ty_outlives_pred = binder.skip_binder();
1690 let ty_name = match ty_outlives_pred.0.sty {
1691 ty::Param(param) => param.name.to_string(),
1692 _ => { return None; }
1694 let lt_name = match ty_outlives_pred.1 {
1695 ty::RegionKind::ReEarlyBound(region) => {
1696 region.name.to_string()
1698 _ => { return None; }
1700 Some((ty_name, lt_name))
1701 }).collect::<Vec<_>>();
1703 let mut bound_spans = Vec::new();
1704 for (i, bound) in bounds.iter().enumerate() {
1705 if let hir::GenericBound::Outlives(lifetime) = bound {
1706 let is_static = match lifetime.name {
1707 hir::LifetimeName::Static => true,
1710 if is_static && !infer_static {
1711 // infer-outlives for 'static is still feature-gated (tracking issue #44493)
1715 let lt_name = &lifetime.name.ident().to_string();
1716 if ty_lt_names.contains(&(param_name.to_owned(), lt_name.to_owned())) {
1717 bound_spans.push((i, bound.span()));
1724 fn consolidate_outlives_bound_spans(
1727 bounds: &hir::GenericBounds,
1728 bound_spans: Vec<(usize, Span)>
1730 if bounds.is_empty() {
1733 if bound_spans.len() == bounds.len() {
1734 let (_, last_bound_span) = bound_spans[bound_spans.len()-1];
1735 // If all bounds are inferable, we want to delete the colon, so
1736 // start from just after the parameter (span passed as argument)
1737 vec![lo.to(last_bound_span)]
1739 let mut merged = Vec::new();
1740 let mut last_merged_i = None;
1742 let mut from_start = true;
1743 for (i, bound_span) in bound_spans {
1744 match last_merged_i {
1745 // If the first bound is inferable, our span should also eat the trailing `+`
1747 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
1748 last_merged_i = Some(0);
1750 // If consecutive bounds are inferable, merge their spans
1751 Some(h) if i == h+1 => {
1752 if let Some(tail) = merged.last_mut() {
1753 // Also eat the trailing `+` if the first
1754 // more-than-one bound is inferable
1755 let to_span = if from_start && i < bounds.len() {
1756 bounds[i+1].span().shrink_to_lo()
1760 *tail = tail.to(to_span);
1761 last_merged_i = Some(i);
1763 bug!("another bound-span visited earlier");
1767 // When we find a non-inferable bound, subsequent inferable bounds
1768 // won't be consecutive from the start (and we'll eat the leading
1769 // `+` rather than the trailing one)
1771 merged.push(bounds[i-1].span().shrink_to_hi().to(bound_span));
1772 last_merged_i = Some(i);
1781 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
1782 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
1783 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
1784 let def_id = cx.tcx.hir().local_def_id(item.id);
1785 if let hir::ItemKind::Struct(_, ref generics) = item.node {
1786 let mut bound_count = 0;
1787 let mut lint_spans = Vec::new();
1789 for param in &generics.params {
1790 let param_name = match param.kind {
1791 hir::GenericParamKind::Lifetime { .. } => { continue; },
1792 hir::GenericParamKind::Type { .. } => {
1794 hir::ParamName::Fresh(_) => { continue; },
1795 hir::ParamName::Error => { continue; },
1796 hir::ParamName::Plain(name) => name.to_string()
1800 let bound_spans = self.collect_outlives_bound_spans(
1801 cx, def_id, ¶m_name, ¶m.bounds, infer_static
1803 bound_count += bound_spans.len();
1805 self.consolidate_outlives_bound_spans(
1806 param.span.shrink_to_hi(), ¶m.bounds, bound_spans
1811 let mut where_lint_spans = Vec::new();
1812 let mut dropped_predicate_count = 0;
1813 let num_predicates = generics.where_clause.predicates.len();
1814 for (i, where_predicate) in generics.where_clause.predicates.iter().enumerate() {
1815 if let hir::WherePredicate::BoundPredicate(predicate) = where_predicate {
1816 let param_name = match predicate.bounded_ty.node {
1817 hir::TyKind::Path(ref qpath) => {
1818 if let hir::QPath::Resolved(None, ty_param_path) = qpath {
1819 ty_param_path.segments[0].ident.to_string()
1826 let bound_spans = self.collect_outlives_bound_spans(
1827 cx, def_id, ¶m_name, &predicate.bounds, infer_static
1829 bound_count += bound_spans.len();
1831 let drop_predicate = bound_spans.len() == predicate.bounds.len();
1833 dropped_predicate_count += 1;
1836 // If all the bounds on a predicate were inferable and there are
1837 // further predicates, we want to eat the trailing comma
1838 if drop_predicate && i + 1 < num_predicates {
1839 let next_predicate_span = generics.where_clause.predicates[i+1].span();
1840 where_lint_spans.push(
1841 predicate.span.to(next_predicate_span.shrink_to_lo())
1844 where_lint_spans.extend(
1845 self.consolidate_outlives_bound_spans(
1846 predicate.span.shrink_to_lo(),
1855 // If all predicates are inferable, drop the entire clause
1856 // (including the `where`)
1857 if num_predicates > 0 && dropped_predicate_count == num_predicates {
1858 let full_where_span = generics.span.shrink_to_hi()
1859 .to(generics.where_clause.span()
1860 .expect("span of (nonempty) where clause should exist"));
1865 lint_spans.extend(where_lint_spans);
1868 if !lint_spans.is_empty() {
1869 let mut err = cx.struct_span_lint(
1870 EXPLICIT_OUTLIVES_REQUIREMENTS,
1872 "outlives requirements can be inferred"
1874 err.multipart_suggestion(
1875 if bound_count == 1 {
1878 "remove these bounds"
1880 lint_spans.into_iter().map(|span| (span, "".to_owned())).collect::<Vec<_>>(),
1881 Applicability::MachineApplicable