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1 //! Lints in the Rust compiler.
2 //!
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main compiler.
6 //!
7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
8 //! Then add code to emit the new lint in the appropriate circumstances.
9 //! You can do that in an existing `LintPass` if it makes sense, or in a
10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
11 //! compiler. Only do the latter if the check can't be written cleanly as a
12 //! `LintPass` (also, note that such lints will need to be defined in
13 //! `rustc_session::lint::builtin`, not here).
14 //!
15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
18 //! with a `pub fn new()`.
19 //!
20 //! If you define a new `LateLintPass`, you will also need to add it to the
21 //! `late_lint_methods!` invocation in `lib.rs`.
22
23 use crate::{
24     errors::BuiltinEllpisisInclusiveRangePatterns,
25     types::{transparent_newtype_field, CItemKind},
26     EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
27 };
28 use rustc_ast::attr;
29 use rustc_ast::tokenstream::{TokenStream, TokenTree};
30 use rustc_ast::visit::{FnCtxt, FnKind};
31 use rustc_ast::{self as ast, *};
32 use rustc_ast_pretty::pprust::{self, expr_to_string};
33 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
34 use rustc_data_structures::stack::ensure_sufficient_stack;
35 use rustc_errors::{
36     fluent, Applicability, DelayDm, Diagnostic, DiagnosticBuilder, DiagnosticMessage,
37     DiagnosticStyledString, MultiSpan,
38 };
39 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
40 use rustc_hir as hir;
41 use rustc_hir::def::{DefKind, Res};
42 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
43 use rustc_hir::{ForeignItemKind, GenericParamKind, HirId, Node, PatKind, PredicateOrigin};
44 use rustc_index::vec::Idx;
45 use rustc_middle::lint::in_external_macro;
46 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
47 use rustc_middle::ty::print::with_no_trimmed_paths;
48 use rustc_middle::ty::subst::GenericArgKind;
49 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, VariantDef};
50 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
51 use rustc_span::edition::Edition;
52 use rustc_span::source_map::Spanned;
53 use rustc_span::symbol::{kw, sym, Ident, Symbol};
54 use rustc_span::{BytePos, InnerSpan, Span};
55 use rustc_target::abi::{Abi, VariantIdx};
56 use rustc_trait_selection::traits::{self, misc::can_type_implement_copy};
57
58 use crate::nonstandard_style::{method_context, MethodLateContext};
59
60 use std::fmt::Write;
61
62 // hardwired lints from librustc_middle
63 pub use rustc_session::lint::builtin::*;
64
65 declare_lint! {
66     /// The `while_true` lint detects `while true { }`.
67     ///
68     /// ### Example
69     ///
70     /// ```rust,no_run
71     /// while true {
72     ///
73     /// }
74     /// ```
75     ///
76     /// {{produces}}
77     ///
78     /// ### Explanation
79     ///
80     /// `while true` should be replaced with `loop`. A `loop` expression is
81     /// the preferred way to write an infinite loop because it more directly
82     /// expresses the intent of the loop.
83     WHILE_TRUE,
84     Warn,
85     "suggest using `loop { }` instead of `while true { }`"
86 }
87
88 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
89
90 /// Traverse through any amount of parenthesis and return the first non-parens expression.
91 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
92     while let ast::ExprKind::Paren(sub) = &expr.kind {
93         expr = sub;
94     }
95     expr
96 }
97
98 impl EarlyLintPass for WhileTrue {
99     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
100         if let ast::ExprKind::While(cond, _, label) = &e.kind
101             && let cond = pierce_parens(cond)
102             && let ast::ExprKind::Lit(token_lit) = cond.kind
103             && let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
104             && !cond.span.from_expansion()
105         {
106             let condition_span = e.span.with_hi(cond.span.hi());
107             cx.struct_span_lint(
108                             WHILE_TRUE,
109                             condition_span,
110                 fluent::lint_builtin_while_true,
111                             |lint| {
112                     lint.span_suggestion_short(
113                         condition_span,
114                         fluent::suggestion,
115                         format!(
116                             "{}loop",
117                             label.map_or_else(String::new, |label| format!(
118                                 "{}: ",
119                                 label.ident,
120                             ))
121                         ),
122                         Applicability::MachineApplicable,
123                     )
124                 },
125             )
126         }
127     }
128 }
129
130 declare_lint! {
131     /// The `box_pointers` lints use of the Box type.
132     ///
133     /// ### Example
134     ///
135     /// ```rust,compile_fail
136     /// #![deny(box_pointers)]
137     /// struct Foo {
138     ///     x: Box<isize>,
139     /// }
140     /// ```
141     ///
142     /// {{produces}}
143     ///
144     /// ### Explanation
145     ///
146     /// This lint is mostly historical, and not particularly useful. `Box<T>`
147     /// used to be built into the language, and the only way to do heap
148     /// allocation. Today's Rust can call into other allocators, etc.
149     BOX_POINTERS,
150     Allow,
151     "use of owned (Box type) heap memory"
152 }
153
154 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
155
156 impl BoxPointers {
157     fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
158         for leaf in ty.walk() {
159             if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
160                 if leaf_ty.is_box() {
161                     cx.struct_span_lint(
162                         BOX_POINTERS,
163                         span,
164                         fluent::lint_builtin_box_pointers,
165                         |lint| lint.set_arg("ty", ty),
166                     );
167                 }
168             }
169         }
170     }
171 }
172
173 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
174     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
175         match it.kind {
176             hir::ItemKind::Fn(..)
177             | hir::ItemKind::TyAlias(..)
178             | hir::ItemKind::Enum(..)
179             | hir::ItemKind::Struct(..)
180             | hir::ItemKind::Union(..) => {
181                 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.owner_id))
182             }
183             _ => (),
184         }
185
186         // If it's a struct, we also have to check the fields' types
187         match it.kind {
188             hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
189                 for field in struct_def.fields() {
190                     self.check_heap_type(cx, field.span, cx.tcx.type_of(field.def_id));
191                 }
192             }
193             _ => (),
194         }
195     }
196
197     fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
198         let ty = cx.typeck_results().node_type(e.hir_id);
199         self.check_heap_type(cx, e.span, ty);
200     }
201 }
202
203 declare_lint! {
204     /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
205     /// instead of `Struct { x }` in a pattern.
206     ///
207     /// ### Example
208     ///
209     /// ```rust
210     /// struct Point {
211     ///     x: i32,
212     ///     y: i32,
213     /// }
214     ///
215     ///
216     /// fn main() {
217     ///     let p = Point {
218     ///         x: 5,
219     ///         y: 5,
220     ///     };
221     ///
222     ///     match p {
223     ///         Point { x: x, y: y } => (),
224     ///     }
225     /// }
226     /// ```
227     ///
228     /// {{produces}}
229     ///
230     /// ### Explanation
231     ///
232     /// The preferred style is to avoid the repetition of specifying both the
233     /// field name and the binding name if both identifiers are the same.
234     NON_SHORTHAND_FIELD_PATTERNS,
235     Warn,
236     "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
237 }
238
239 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
240
241 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
242     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
243         if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
244             let variant = cx
245                 .typeck_results()
246                 .pat_ty(pat)
247                 .ty_adt_def()
248                 .expect("struct pattern type is not an ADT")
249                 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
250             for fieldpat in field_pats {
251                 if fieldpat.is_shorthand {
252                     continue;
253                 }
254                 if fieldpat.span.from_expansion() {
255                     // Don't lint if this is a macro expansion: macro authors
256                     // shouldn't have to worry about this kind of style issue
257                     // (Issue #49588)
258                     continue;
259                 }
260                 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
261                     if cx.tcx.find_field_index(ident, &variant)
262                         == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
263                     {
264                         cx.struct_span_lint(
265                             NON_SHORTHAND_FIELD_PATTERNS,
266                             fieldpat.span,
267                             fluent::lint_builtin_non_shorthand_field_patterns,
268                             |lint| {
269                                 let suggested_ident =
270                                     format!("{}{}", binding_annot.prefix_str(), ident);
271                                 lint.set_arg("ident", ident.clone()).span_suggestion(
272                                     fieldpat.span,
273                                     fluent::suggestion,
274                                     suggested_ident,
275                                     Applicability::MachineApplicable,
276                                 )
277                             },
278                         );
279                     }
280                 }
281             }
282         }
283     }
284 }
285
286 declare_lint! {
287     /// The `unsafe_code` lint catches usage of `unsafe` code.
288     ///
289     /// ### Example
290     ///
291     /// ```rust,compile_fail
292     /// #![deny(unsafe_code)]
293     /// fn main() {
294     ///     unsafe {
295     ///
296     ///     }
297     /// }
298     /// ```
299     ///
300     /// {{produces}}
301     ///
302     /// ### Explanation
303     ///
304     /// This lint is intended to restrict the usage of `unsafe`, which can be
305     /// difficult to use correctly.
306     UNSAFE_CODE,
307     Allow,
308     "usage of `unsafe` code"
309 }
310
311 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
312
313 impl UnsafeCode {
314     fn report_unsafe(
315         &self,
316         cx: &EarlyContext<'_>,
317         span: Span,
318         msg: impl Into<DiagnosticMessage>,
319         decorate: impl for<'a, 'b> FnOnce(
320             &'b mut DiagnosticBuilder<'a, ()>,
321         ) -> &'b mut DiagnosticBuilder<'a, ()>,
322     ) {
323         // This comes from a macro that has `#[allow_internal_unsafe]`.
324         if span.allows_unsafe() {
325             return;
326         }
327
328         cx.struct_span_lint(UNSAFE_CODE, span, msg, decorate);
329     }
330
331     fn report_overridden_symbol_name(
332         &self,
333         cx: &EarlyContext<'_>,
334         span: Span,
335         msg: DiagnosticMessage,
336     ) {
337         self.report_unsafe(cx, span, msg, |lint| {
338             lint.note(fluent::lint_builtin_overridden_symbol_name)
339         })
340     }
341
342     fn report_overridden_symbol_section(
343         &self,
344         cx: &EarlyContext<'_>,
345         span: Span,
346         msg: DiagnosticMessage,
347     ) {
348         self.report_unsafe(cx, span, msg, |lint| {
349             lint.note(fluent::lint_builtin_overridden_symbol_section)
350         })
351     }
352 }
353
354 impl EarlyLintPass for UnsafeCode {
355     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
356         if attr.has_name(sym::allow_internal_unsafe) {
357             self.report_unsafe(cx, attr.span, fluent::lint_builtin_allow_internal_unsafe, |lint| {
358                 lint
359             });
360         }
361     }
362
363     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
364         if let ast::ExprKind::Block(ref blk, _) = e.kind {
365             // Don't warn about generated blocks; that'll just pollute the output.
366             if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
367                 self.report_unsafe(cx, blk.span, fluent::lint_builtin_unsafe_block, |lint| lint);
368             }
369         }
370     }
371
372     fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
373         match it.kind {
374             ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => {
375                 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_trait, |lint| lint)
376             }
377
378             ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => {
379                 self.report_unsafe(cx, it.span, fluent::lint_builtin_unsafe_impl, |lint| lint)
380             }
381
382             ast::ItemKind::Fn(..) => {
383                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
384                     self.report_overridden_symbol_name(
385                         cx,
386                         attr.span,
387                         fluent::lint_builtin_no_mangle_fn,
388                     );
389                 }
390
391                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
392                     self.report_overridden_symbol_name(
393                         cx,
394                         attr.span,
395                         fluent::lint_builtin_export_name_fn,
396                     );
397                 }
398
399                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
400                     self.report_overridden_symbol_section(
401                         cx,
402                         attr.span,
403                         fluent::lint_builtin_link_section_fn,
404                     );
405                 }
406             }
407
408             ast::ItemKind::Static(..) => {
409                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
410                     self.report_overridden_symbol_name(
411                         cx,
412                         attr.span,
413                         fluent::lint_builtin_no_mangle_static,
414                     );
415                 }
416
417                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
418                     self.report_overridden_symbol_name(
419                         cx,
420                         attr.span,
421                         fluent::lint_builtin_export_name_static,
422                     );
423                 }
424
425                 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
426                     self.report_overridden_symbol_section(
427                         cx,
428                         attr.span,
429                         fluent::lint_builtin_link_section_static,
430                     );
431                 }
432             }
433
434             _ => {}
435         }
436     }
437
438     fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
439         if let ast::AssocItemKind::Fn(..) = it.kind {
440             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
441                 self.report_overridden_symbol_name(
442                     cx,
443                     attr.span,
444                     fluent::lint_builtin_no_mangle_method,
445                 );
446             }
447             if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
448                 self.report_overridden_symbol_name(
449                     cx,
450                     attr.span,
451                     fluent::lint_builtin_export_name_method,
452                 );
453             }
454         }
455     }
456
457     fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
458         if let FnKind::Fn(
459             ctxt,
460             _,
461             ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
462             _,
463             _,
464             body,
465         ) = fk
466         {
467             let msg = match ctxt {
468                 FnCtxt::Foreign => return,
469                 FnCtxt::Free => fluent::lint_builtin_decl_unsafe_fn,
470                 FnCtxt::Assoc(_) if body.is_none() => fluent::lint_builtin_decl_unsafe_method,
471                 FnCtxt::Assoc(_) => fluent::lint_builtin_impl_unsafe_method,
472             };
473             self.report_unsafe(cx, span, msg, |lint| lint);
474         }
475     }
476 }
477
478 declare_lint! {
479     /// The `missing_docs` lint detects missing documentation for public items.
480     ///
481     /// ### Example
482     ///
483     /// ```rust,compile_fail
484     /// #![deny(missing_docs)]
485     /// pub fn foo() {}
486     /// ```
487     ///
488     /// {{produces}}
489     ///
490     /// ### Explanation
491     ///
492     /// This lint is intended to ensure that a library is well-documented.
493     /// Items without documentation can be difficult for users to understand
494     /// how to use properly.
495     ///
496     /// This lint is "allow" by default because it can be noisy, and not all
497     /// projects may want to enforce everything to be documented.
498     pub MISSING_DOCS,
499     Allow,
500     "detects missing documentation for public members",
501     report_in_external_macro
502 }
503
504 pub struct MissingDoc {
505     /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
506     doc_hidden_stack: Vec<bool>,
507 }
508
509 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
510
511 fn has_doc(attr: &ast::Attribute) -> bool {
512     if attr.is_doc_comment() {
513         return true;
514     }
515
516     if !attr.has_name(sym::doc) {
517         return false;
518     }
519
520     if attr.value_str().is_some() {
521         return true;
522     }
523
524     if let Some(list) = attr.meta_item_list() {
525         for meta in list {
526             if meta.has_name(sym::hidden) {
527                 return true;
528             }
529         }
530     }
531
532     false
533 }
534
535 impl MissingDoc {
536     pub fn new() -> MissingDoc {
537         MissingDoc { doc_hidden_stack: vec![false] }
538     }
539
540     fn doc_hidden(&self) -> bool {
541         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
542     }
543
544     fn check_missing_docs_attrs(
545         &self,
546         cx: &LateContext<'_>,
547         def_id: LocalDefId,
548         article: &'static str,
549         desc: &'static str,
550     ) {
551         // If we're building a test harness, then warning about
552         // documentation is probably not really relevant right now.
553         if cx.sess().opts.test {
554             return;
555         }
556
557         // `#[doc(hidden)]` disables missing_docs check.
558         if self.doc_hidden() {
559             return;
560         }
561
562         // Only check publicly-visible items, using the result from the privacy pass.
563         // It's an option so the crate root can also use this function (it doesn't
564         // have a `NodeId`).
565         if def_id != CRATE_DEF_ID {
566             if !cx.effective_visibilities.is_exported(def_id) {
567                 return;
568             }
569         }
570
571         let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
572         let has_doc = attrs.iter().any(has_doc);
573         if !has_doc {
574             cx.struct_span_lint(
575                 MISSING_DOCS,
576                 cx.tcx.def_span(def_id),
577                 fluent::lint_builtin_missing_doc,
578                 |lint| lint.set_arg("article", article).set_arg("desc", desc),
579             );
580         }
581     }
582 }
583
584 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
585     fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
586         let doc_hidden = self.doc_hidden()
587             || attrs.iter().any(|attr| {
588                 attr.has_name(sym::doc)
589                     && match attr.meta_item_list() {
590                         None => false,
591                         Some(l) => attr::list_contains_name(&l, sym::hidden),
592                     }
593             });
594         self.doc_hidden_stack.push(doc_hidden);
595     }
596
597     fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
598         self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
599     }
600
601     fn check_crate(&mut self, cx: &LateContext<'_>) {
602         self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
603     }
604
605     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
606         match it.kind {
607             hir::ItemKind::Trait(..) => {
608                 // Issue #11592: traits are always considered exported, even when private.
609                 if cx.tcx.visibility(it.owner_id)
610                     == ty::Visibility::Restricted(
611                         cx.tcx.parent_module_from_def_id(it.owner_id.def_id).to_def_id(),
612                     )
613                 {
614                     return;
615                 }
616             }
617             hir::ItemKind::TyAlias(..)
618             | hir::ItemKind::Fn(..)
619             | hir::ItemKind::Macro(..)
620             | hir::ItemKind::Mod(..)
621             | hir::ItemKind::Enum(..)
622             | hir::ItemKind::Struct(..)
623             | hir::ItemKind::Union(..)
624             | hir::ItemKind::Const(..)
625             | hir::ItemKind::Static(..) => {}
626
627             _ => return,
628         };
629
630         let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
631
632         self.check_missing_docs_attrs(cx, it.owner_id.def_id, article, desc);
633     }
634
635     fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
636         let (article, desc) = cx.tcx.article_and_description(trait_item.owner_id.to_def_id());
637
638         self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, article, desc);
639     }
640
641     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
642         // If the method is an impl for a trait, don't doc.
643         if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
644             return;
645         }
646
647         // If the method is an impl for an item with docs_hidden, don't doc.
648         if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
649             let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
650             let impl_ty = cx.tcx.type_of(parent);
651             let outerdef = match impl_ty.kind() {
652                 ty::Adt(def, _) => Some(def.did()),
653                 ty::Foreign(def_id) => Some(*def_id),
654                 _ => None,
655             };
656             let is_hidden = match outerdef {
657                 Some(id) => cx.tcx.is_doc_hidden(id),
658                 None => false,
659             };
660             if is_hidden {
661                 return;
662             }
663         }
664
665         let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
666         self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);
667     }
668
669     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
670         let (article, desc) = cx.tcx.article_and_description(foreign_item.owner_id.to_def_id());
671         self.check_missing_docs_attrs(cx, foreign_item.owner_id.def_id, article, desc);
672     }
673
674     fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
675         if !sf.is_positional() {
676             self.check_missing_docs_attrs(cx, sf.def_id, "a", "struct field")
677         }
678     }
679
680     fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
681         self.check_missing_docs_attrs(cx, v.def_id, "a", "variant");
682     }
683 }
684
685 declare_lint! {
686     /// The `missing_copy_implementations` lint detects potentially-forgotten
687     /// implementations of [`Copy`].
688     ///
689     /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
690     ///
691     /// ### Example
692     ///
693     /// ```rust,compile_fail
694     /// #![deny(missing_copy_implementations)]
695     /// pub struct Foo {
696     ///     pub field: i32
697     /// }
698     /// # fn main() {}
699     /// ```
700     ///
701     /// {{produces}}
702     ///
703     /// ### Explanation
704     ///
705     /// Historically (before 1.0), types were automatically marked as `Copy`
706     /// if possible. This was changed so that it required an explicit opt-in
707     /// by implementing the `Copy` trait. As part of this change, a lint was
708     /// added to alert if a copyable type was not marked `Copy`.
709     ///
710     /// This lint is "allow" by default because this code isn't bad; it is
711     /// common to write newtypes like this specifically so that a `Copy` type
712     /// is no longer `Copy`. `Copy` types can result in unintended copies of
713     /// large data which can impact performance.
714     pub MISSING_COPY_IMPLEMENTATIONS,
715     Allow,
716     "detects potentially-forgotten implementations of `Copy`"
717 }
718
719 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
720
721 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
722     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
723         if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
724             return;
725         }
726         let (def, ty) = match item.kind {
727             hir::ItemKind::Struct(_, ref ast_generics) => {
728                 if !ast_generics.params.is_empty() {
729                     return;
730                 }
731                 let def = cx.tcx.adt_def(item.owner_id);
732                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
733             }
734             hir::ItemKind::Union(_, ref ast_generics) => {
735                 if !ast_generics.params.is_empty() {
736                     return;
737                 }
738                 let def = cx.tcx.adt_def(item.owner_id);
739                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
740             }
741             hir::ItemKind::Enum(_, ref ast_generics) => {
742                 if !ast_generics.params.is_empty() {
743                     return;
744                 }
745                 let def = cx.tcx.adt_def(item.owner_id);
746                 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
747             }
748             _ => return,
749         };
750         if def.has_dtor(cx.tcx) {
751             return;
752         }
753         let param_env = ty::ParamEnv::empty();
754         if ty.is_copy_modulo_regions(cx.tcx, param_env) {
755             return;
756         }
757         if can_type_implement_copy(
758             cx.tcx,
759             param_env,
760             ty,
761             traits::ObligationCause::misc(item.span, item.hir_id()),
762         )
763         .is_ok()
764         {
765             cx.struct_span_lint(
766                 MISSING_COPY_IMPLEMENTATIONS,
767                 item.span,
768                 fluent::lint_builtin_missing_copy_impl,
769                 |lint| lint,
770             )
771         }
772     }
773 }
774
775 declare_lint! {
776     /// The `missing_debug_implementations` lint detects missing
777     /// implementations of [`fmt::Debug`].
778     ///
779     /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
780     ///
781     /// ### Example
782     ///
783     /// ```rust,compile_fail
784     /// #![deny(missing_debug_implementations)]
785     /// pub struct Foo;
786     /// # fn main() {}
787     /// ```
788     ///
789     /// {{produces}}
790     ///
791     /// ### Explanation
792     ///
793     /// Having a `Debug` implementation on all types can assist with
794     /// debugging, as it provides a convenient way to format and display a
795     /// value. Using the `#[derive(Debug)]` attribute will automatically
796     /// generate a typical implementation, or a custom implementation can be
797     /// added by manually implementing the `Debug` trait.
798     ///
799     /// This lint is "allow" by default because adding `Debug` to all types can
800     /// have a negative impact on compile time and code size. It also requires
801     /// boilerplate to be added to every type, which can be an impediment.
802     MISSING_DEBUG_IMPLEMENTATIONS,
803     Allow,
804     "detects missing implementations of Debug"
805 }
806
807 #[derive(Default)]
808 pub struct MissingDebugImplementations {
809     impling_types: Option<LocalDefIdSet>,
810 }
811
812 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
813
814 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
815     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
816         if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
817             return;
818         }
819
820         match item.kind {
821             hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
822             _ => return,
823         }
824
825         let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
826             return
827         };
828
829         if self.impling_types.is_none() {
830             let mut impls = LocalDefIdSet::default();
831             cx.tcx.for_each_impl(debug, |d| {
832                 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
833                     if let Some(def_id) = ty_def.did().as_local() {
834                         impls.insert(def_id);
835                     }
836                 }
837             });
838
839             self.impling_types = Some(impls);
840             debug!("{:?}", self.impling_types);
841         }
842
843         if !self.impling_types.as_ref().unwrap().contains(&item.owner_id.def_id) {
844             cx.struct_span_lint(
845                 MISSING_DEBUG_IMPLEMENTATIONS,
846                 item.span,
847                 fluent::lint_builtin_missing_debug_impl,
848                 |lint| lint.set_arg("debug", cx.tcx.def_path_str(debug)),
849             );
850         }
851     }
852 }
853
854 declare_lint! {
855     /// The `anonymous_parameters` lint detects anonymous parameters in trait
856     /// definitions.
857     ///
858     /// ### Example
859     ///
860     /// ```rust,edition2015,compile_fail
861     /// #![deny(anonymous_parameters)]
862     /// // edition 2015
863     /// pub trait Foo {
864     ///     fn foo(usize);
865     /// }
866     /// fn main() {}
867     /// ```
868     ///
869     /// {{produces}}
870     ///
871     /// ### Explanation
872     ///
873     /// This syntax is mostly a historical accident, and can be worked around
874     /// quite easily by adding an `_` pattern or a descriptive identifier:
875     ///
876     /// ```rust
877     /// trait Foo {
878     ///     fn foo(_: usize);
879     /// }
880     /// ```
881     ///
882     /// This syntax is now a hard error in the 2018 edition. In the 2015
883     /// edition, this lint is "warn" by default. This lint
884     /// enables the [`cargo fix`] tool with the `--edition` flag to
885     /// automatically transition old code from the 2015 edition to 2018. The
886     /// tool will run this lint and automatically apply the
887     /// suggested fix from the compiler (which is to add `_` to each
888     /// parameter). This provides a completely automated way to update old
889     /// code for a new edition. See [issue #41686] for more details.
890     ///
891     /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
892     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
893     pub ANONYMOUS_PARAMETERS,
894     Warn,
895     "detects anonymous parameters",
896     @future_incompatible = FutureIncompatibleInfo {
897         reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
898         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
899     };
900 }
901
902 declare_lint_pass!(
903     /// Checks for use of anonymous parameters (RFC 1685).
904     AnonymousParameters => [ANONYMOUS_PARAMETERS]
905 );
906
907 impl EarlyLintPass for AnonymousParameters {
908     fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
909         if cx.sess().edition() != Edition::Edition2015 {
910             // This is a hard error in future editions; avoid linting and erroring
911             return;
912         }
913         if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
914             for arg in sig.decl.inputs.iter() {
915                 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
916                     if ident.name == kw::Empty {
917                         let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
918
919                         let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
920                             (snip.as_str(), Applicability::MachineApplicable)
921                         } else {
922                             ("<type>", Applicability::HasPlaceholders)
923                         };
924                         cx.struct_span_lint(
925                             ANONYMOUS_PARAMETERS,
926                             arg.pat.span,
927                             fluent::lint_builtin_anonymous_params,
928                             |lint| {
929                                 lint.span_suggestion(
930                                     arg.pat.span,
931                                     fluent::suggestion,
932                                     format!("_: {}", ty_snip),
933                                     appl,
934                                 )
935                             },
936                         )
937                     }
938                 }
939             }
940         }
941     }
942 }
943
944 /// Check for use of attributes which have been deprecated.
945 #[derive(Clone)]
946 pub struct DeprecatedAttr {
947     // This is not free to compute, so we want to keep it around, rather than
948     // compute it for every attribute.
949     depr_attrs: Vec<&'static BuiltinAttribute>,
950 }
951
952 impl_lint_pass!(DeprecatedAttr => []);
953
954 impl DeprecatedAttr {
955     pub fn new() -> DeprecatedAttr {
956         DeprecatedAttr { depr_attrs: deprecated_attributes() }
957     }
958 }
959
960 impl EarlyLintPass for DeprecatedAttr {
961     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
962         for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
963             if attr.ident().map(|ident| ident.name) == Some(*name) {
964                 if let &AttributeGate::Gated(
965                     Stability::Deprecated(link, suggestion),
966                     name,
967                     reason,
968                     _,
969                 ) = gate
970                 {
971                     // FIXME(davidtwco) translatable deprecated attr
972                     cx.struct_span_lint(
973                         DEPRECATED,
974                         attr.span,
975                         fluent::lint_builtin_deprecated_attr_link,
976                         |lint| {
977                             lint.set_arg("name", name)
978                                 .set_arg("reason", reason)
979                                 .set_arg("link", link)
980                                 .span_suggestion_short(
981                                     attr.span,
982                                     suggestion.map(|s| s.into()).unwrap_or(
983                                         fluent::lint_builtin_deprecated_attr_default_suggestion,
984                                     ),
985                                     "",
986                                     Applicability::MachineApplicable,
987                                 )
988                         },
989                     );
990                 }
991                 return;
992             }
993         }
994         if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
995             cx.struct_span_lint(
996                 DEPRECATED,
997                 attr.span,
998                 fluent::lint_builtin_deprecated_attr_used,
999                 |lint| {
1000                     lint.set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
1001                         .span_suggestion_short(
1002                             attr.span,
1003                             fluent::lint_builtin_deprecated_attr_default_suggestion,
1004                             "",
1005                             Applicability::MachineApplicable,
1006                         )
1007                 },
1008             );
1009         }
1010     }
1011 }
1012
1013 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1014     use rustc_ast::token::CommentKind;
1015
1016     let mut attrs = attrs.iter().peekable();
1017
1018     // Accumulate a single span for sugared doc comments.
1019     let mut sugared_span: Option<Span> = None;
1020
1021     while let Some(attr) = attrs.next() {
1022         let is_doc_comment = attr.is_doc_comment();
1023         if is_doc_comment {
1024             sugared_span =
1025                 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1026         }
1027
1028         if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1029             continue;
1030         }
1031
1032         let span = sugared_span.take().unwrap_or(attr.span);
1033
1034         if is_doc_comment || attr.has_name(sym::doc) {
1035             cx.struct_span_lint(
1036                 UNUSED_DOC_COMMENTS,
1037                 span,
1038                 fluent::lint_builtin_unused_doc_comment,
1039                 |lint| {
1040                     lint.set_arg("kind", node_kind).span_label(node_span, fluent::label).help(
1041                         match attr.kind {
1042                             AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1043                                 fluent::plain_help
1044                             }
1045                             AttrKind::DocComment(CommentKind::Block, _) => fluent::block_help,
1046                         },
1047                     )
1048                 },
1049             );
1050         }
1051     }
1052 }
1053
1054 impl EarlyLintPass for UnusedDocComment {
1055     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1056         let kind = match stmt.kind {
1057             ast::StmtKind::Local(..) => "statements",
1058             // Disabled pending discussion in #78306
1059             ast::StmtKind::Item(..) => return,
1060             // expressions will be reported by `check_expr`.
1061             ast::StmtKind::Empty
1062             | ast::StmtKind::Semi(_)
1063             | ast::StmtKind::Expr(_)
1064             | ast::StmtKind::MacCall(_) => return,
1065         };
1066
1067         warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1068     }
1069
1070     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1071         let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1072         warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1073     }
1074
1075     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1076         warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1077     }
1078
1079     fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1080         warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
1081     }
1082
1083     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1084         warn_if_doc(cx, block.span, "blocks", &block.attrs());
1085     }
1086
1087     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1088         if let ast::ItemKind::ForeignMod(_) = item.kind {
1089             warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1090         }
1091     }
1092 }
1093
1094 declare_lint! {
1095     /// The `no_mangle_const_items` lint detects any `const` items with the
1096     /// [`no_mangle` attribute].
1097     ///
1098     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1099     ///
1100     /// ### Example
1101     ///
1102     /// ```rust,compile_fail
1103     /// #[no_mangle]
1104     /// const FOO: i32 = 5;
1105     /// ```
1106     ///
1107     /// {{produces}}
1108     ///
1109     /// ### Explanation
1110     ///
1111     /// Constants do not have their symbols exported, and therefore, this
1112     /// probably means you meant to use a [`static`], not a [`const`].
1113     ///
1114     /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1115     /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1116     NO_MANGLE_CONST_ITEMS,
1117     Deny,
1118     "const items will not have their symbols exported"
1119 }
1120
1121 declare_lint! {
1122     /// The `no_mangle_generic_items` lint detects generic items that must be
1123     /// mangled.
1124     ///
1125     /// ### Example
1126     ///
1127     /// ```rust
1128     /// #[no_mangle]
1129     /// fn foo<T>(t: T) {
1130     ///
1131     /// }
1132     /// ```
1133     ///
1134     /// {{produces}}
1135     ///
1136     /// ### Explanation
1137     ///
1138     /// A function with generics must have its symbol mangled to accommodate
1139     /// the generic parameter. The [`no_mangle` attribute] has no effect in
1140     /// this situation, and should be removed.
1141     ///
1142     /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1143     NO_MANGLE_GENERIC_ITEMS,
1144     Warn,
1145     "generic items must be mangled"
1146 }
1147
1148 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1149
1150 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1151     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1152         let attrs = cx.tcx.hir().attrs(it.hir_id());
1153         let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1154                                              impl_generics: Option<&hir::Generics<'_>>,
1155                                              generics: &hir::Generics<'_>,
1156                                              span| {
1157             for param in
1158                 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1159             {
1160                 match param.kind {
1161                     GenericParamKind::Lifetime { .. } => {}
1162                     GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1163                         cx.struct_span_lint(
1164                             NO_MANGLE_GENERIC_ITEMS,
1165                             span,
1166                             fluent::lint_builtin_no_mangle_generic,
1167                             |lint| {
1168                                 lint.span_suggestion_short(
1169                                     no_mangle_attr.span,
1170                                     fluent::suggestion,
1171                                     "",
1172                                     // Use of `#[no_mangle]` suggests FFI intent; correct
1173                                     // fix may be to monomorphize source by hand
1174                                     Applicability::MaybeIncorrect,
1175                                 )
1176                             },
1177                         );
1178                         break;
1179                     }
1180                 }
1181             }
1182         };
1183         match it.kind {
1184             hir::ItemKind::Fn(.., ref generics, _) => {
1185                 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1186                     check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1187                 }
1188             }
1189             hir::ItemKind::Const(..) => {
1190                 if cx.sess().contains_name(attrs, sym::no_mangle) {
1191                     // Const items do not refer to a particular location in memory, and therefore
1192                     // don't have anything to attach a symbol to
1193                     cx.struct_span_lint(
1194                         NO_MANGLE_CONST_ITEMS,
1195                         it.span,
1196                         fluent::lint_builtin_const_no_mangle,
1197                         |lint| {
1198                             // account for "pub const" (#45562)
1199                             let start = cx
1200                                 .tcx
1201                                 .sess
1202                                 .source_map()
1203                                 .span_to_snippet(it.span)
1204                                 .map(|snippet| snippet.find("const").unwrap_or(0))
1205                                 .unwrap_or(0) as u32;
1206                             // `const` is 5 chars
1207                             let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1208                             lint.span_suggestion(
1209                                 const_span,
1210                                 fluent::suggestion,
1211                                 "pub static",
1212                                 Applicability::MachineApplicable,
1213                             )
1214                         },
1215                     );
1216                 }
1217             }
1218             hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1219                 for it in *items {
1220                     if let hir::AssocItemKind::Fn { .. } = it.kind {
1221                         if let Some(no_mangle_attr) = cx
1222                             .sess()
1223                             .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1224                         {
1225                             check_no_mangle_on_generic_fn(
1226                                 no_mangle_attr,
1227                                 Some(generics),
1228                                 cx.tcx.hir().get_generics(it.id.owner_id.def_id).unwrap(),
1229                                 it.span,
1230                             );
1231                         }
1232                     }
1233                 }
1234             }
1235             _ => {}
1236         }
1237     }
1238 }
1239
1240 declare_lint! {
1241     /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1242     /// T` because it is [undefined behavior].
1243     ///
1244     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1245     ///
1246     /// ### Example
1247     ///
1248     /// ```rust,compile_fail
1249     /// unsafe {
1250     ///     let y = std::mem::transmute::<&i32, &mut i32>(&5);
1251     /// }
1252     /// ```
1253     ///
1254     /// {{produces}}
1255     ///
1256     /// ### Explanation
1257     ///
1258     /// Certain assumptions are made about aliasing of data, and this transmute
1259     /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1260     ///
1261     /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1262     MUTABLE_TRANSMUTES,
1263     Deny,
1264     "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1265 }
1266
1267 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1268
1269 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1270     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1271         if let Some((&ty::Ref(_, _, from_mutbl), &ty::Ref(_, _, to_mutbl))) =
1272             get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1273         {
1274             if from_mutbl < to_mutbl {
1275                 cx.struct_span_lint(
1276                     MUTABLE_TRANSMUTES,
1277                     expr.span,
1278                     fluent::lint_builtin_mutable_transmutes,
1279                     |lint| lint,
1280                 );
1281             }
1282         }
1283
1284         fn get_transmute_from_to<'tcx>(
1285             cx: &LateContext<'tcx>,
1286             expr: &hir::Expr<'_>,
1287         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1288             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1289                 cx.qpath_res(qpath, expr.hir_id)
1290             } else {
1291                 return None;
1292             };
1293             if let Res::Def(DefKind::Fn, did) = def {
1294                 if !def_id_is_transmute(cx, did) {
1295                     return None;
1296                 }
1297                 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1298                 let from = sig.inputs().skip_binder()[0];
1299                 let to = sig.output().skip_binder();
1300                 return Some((from, to));
1301             }
1302             None
1303         }
1304
1305         fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1306             cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1307         }
1308     }
1309 }
1310
1311 declare_lint! {
1312     /// The `unstable_features` is deprecated and should no longer be used.
1313     UNSTABLE_FEATURES,
1314     Allow,
1315     "enabling unstable features (deprecated. do not use)"
1316 }
1317
1318 declare_lint_pass!(
1319     /// Forbids using the `#[feature(...)]` attribute
1320     UnstableFeatures => [UNSTABLE_FEATURES]
1321 );
1322
1323 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1324     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1325         if attr.has_name(sym::feature) {
1326             if let Some(items) = attr.meta_item_list() {
1327                 for item in items {
1328                     cx.struct_span_lint(
1329                         UNSTABLE_FEATURES,
1330                         item.span(),
1331                         fluent::lint_builtin_unstable_features,
1332                         |lint| lint,
1333                     );
1334                 }
1335             }
1336         }
1337     }
1338 }
1339
1340 declare_lint! {
1341     /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1342     /// the crate root.
1343     ///
1344     /// ### Example
1345     ///
1346     /// ```rust,compile_fail
1347     /// #![deny(unreachable_pub)]
1348     /// mod foo {
1349     ///     pub mod bar {
1350     ///
1351     ///     }
1352     /// }
1353     /// ```
1354     ///
1355     /// {{produces}}
1356     ///
1357     /// ### Explanation
1358     ///
1359     /// A bare `pub` visibility may be misleading if the item is not actually
1360     /// publicly exported from the crate. The `pub(crate)` visibility is
1361     /// recommended to be used instead, which more clearly expresses the intent
1362     /// that the item is only visible within its own crate.
1363     ///
1364     /// This lint is "allow" by default because it will trigger for a large
1365     /// amount existing Rust code, and has some false-positives. Eventually it
1366     /// is desired for this to become warn-by-default.
1367     pub UNREACHABLE_PUB,
1368     Allow,
1369     "`pub` items not reachable from crate root"
1370 }
1371
1372 declare_lint_pass!(
1373     /// Lint for items marked `pub` that aren't reachable from other crates.
1374     UnreachablePub => [UNREACHABLE_PUB]
1375 );
1376
1377 impl UnreachablePub {
1378     fn perform_lint(
1379         &self,
1380         cx: &LateContext<'_>,
1381         what: &str,
1382         def_id: LocalDefId,
1383         vis_span: Span,
1384         exportable: bool,
1385     ) {
1386         let mut applicability = Applicability::MachineApplicable;
1387         if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
1388         {
1389             if vis_span.from_expansion() {
1390                 applicability = Applicability::MaybeIncorrect;
1391             }
1392             let def_span = cx.tcx.def_span(def_id);
1393             cx.struct_span_lint(
1394                 UNREACHABLE_PUB,
1395                 def_span,
1396                 fluent::lint_builtin_unreachable_pub,
1397                 |lint| {
1398                     lint.set_arg("what", what);
1399
1400                     lint.span_suggestion(vis_span, fluent::suggestion, "pub(crate)", applicability);
1401                     if exportable {
1402                         lint.help(fluent::help);
1403                     }
1404                     lint
1405                 },
1406             );
1407         }
1408     }
1409 }
1410
1411 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1412     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1413         // Do not warn for fake `use` statements.
1414         if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1415             return;
1416         }
1417         self.perform_lint(cx, "item", item.owner_id.def_id, item.vis_span, true);
1418     }
1419
1420     fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1421         self.perform_lint(cx, "item", foreign_item.owner_id.def_id, foreign_item.vis_span, true);
1422     }
1423
1424     fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1425         let map = cx.tcx.hir();
1426         if matches!(map.get(map.get_parent_node(field.hir_id)), Node::Variant(_)) {
1427             return;
1428         }
1429         self.perform_lint(cx, "field", field.def_id, field.vis_span, false);
1430     }
1431
1432     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1433         // Only lint inherent impl items.
1434         if cx.tcx.associated_item(impl_item.owner_id).trait_item_def_id.is_none() {
1435             self.perform_lint(cx, "item", impl_item.owner_id.def_id, impl_item.vis_span, false);
1436         }
1437     }
1438 }
1439
1440 declare_lint! {
1441     /// The `type_alias_bounds` lint detects bounds in type aliases.
1442     ///
1443     /// ### Example
1444     ///
1445     /// ```rust
1446     /// type SendVec<T: Send> = Vec<T>;
1447     /// ```
1448     ///
1449     /// {{produces}}
1450     ///
1451     /// ### Explanation
1452     ///
1453     /// The trait bounds in a type alias are currently ignored, and should not
1454     /// be included to avoid confusion. This was previously allowed
1455     /// unintentionally; this may become a hard error in the future.
1456     TYPE_ALIAS_BOUNDS,
1457     Warn,
1458     "bounds in type aliases are not enforced"
1459 }
1460
1461 declare_lint_pass!(
1462     /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1463     /// They are relevant when using associated types, but otherwise neither checked
1464     /// at definition site nor enforced at use site.
1465     TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1466 );
1467
1468 impl TypeAliasBounds {
1469     fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1470         match *qpath {
1471             hir::QPath::TypeRelative(ref ty, _) => {
1472                 // If this is a type variable, we found a `T::Assoc`.
1473                 match ty.kind {
1474                     hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1475                         matches!(path.res, Res::Def(DefKind::TyParam, _))
1476                     }
1477                     _ => false,
1478                 }
1479             }
1480             hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1481         }
1482     }
1483
1484     fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
1485         // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1486         // bound.  Let's see if this type does that.
1487
1488         // We use a HIR visitor to walk the type.
1489         use rustc_hir::intravisit::{self, Visitor};
1490         struct WalkAssocTypes<'a> {
1491             err: &'a mut Diagnostic,
1492         }
1493         impl Visitor<'_> for WalkAssocTypes<'_> {
1494             fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
1495                 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1496                     self.err.span_help(span, fluent::lint_builtin_type_alias_bounds_help);
1497                 }
1498                 intravisit::walk_qpath(self, qpath, id)
1499             }
1500         }
1501
1502         // Let's go for a walk!
1503         let mut visitor = WalkAssocTypes { err };
1504         visitor.visit_ty(ty);
1505     }
1506 }
1507
1508 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1509     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1510         let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1511             return
1512         };
1513         if let hir::TyKind::OpaqueDef(..) = ty.kind {
1514             // Bounds are respected for `type X = impl Trait`
1515             return;
1516         }
1517         // There must not be a where clause
1518         if type_alias_generics.predicates.is_empty() {
1519             return;
1520         }
1521
1522         let mut where_spans = Vec::new();
1523         let mut inline_spans = Vec::new();
1524         let mut inline_sugg = Vec::new();
1525         for p in type_alias_generics.predicates {
1526             let span = p.span();
1527             if p.in_where_clause() {
1528                 where_spans.push(span);
1529             } else {
1530                 for b in p.bounds() {
1531                     inline_spans.push(b.span());
1532                 }
1533                 inline_sugg.push((span, String::new()));
1534             }
1535         }
1536
1537         let mut suggested_changing_assoc_types = false;
1538         if !where_spans.is_empty() {
1539             cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_where_clause, |lint| {
1540                 lint.set_span(where_spans);
1541                 lint.span_suggestion(
1542                     type_alias_generics.where_clause_span,
1543                     fluent::suggestion,
1544                     "",
1545                     Applicability::MachineApplicable,
1546                 );
1547                 if !suggested_changing_assoc_types {
1548                     TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1549                     suggested_changing_assoc_types = true;
1550                 }
1551                 lint
1552             });
1553         }
1554
1555         if !inline_spans.is_empty() {
1556             cx.lint(TYPE_ALIAS_BOUNDS, fluent::lint_builtin_type_alias_generic_bounds, |lint| {
1557                 lint.set_span(inline_spans);
1558                 lint.multipart_suggestion(
1559                     fluent::suggestion,
1560                     inline_sugg,
1561                     Applicability::MachineApplicable,
1562                 );
1563                 if !suggested_changing_assoc_types {
1564                     TypeAliasBounds::suggest_changing_assoc_types(ty, lint);
1565                 }
1566                 lint
1567             });
1568         }
1569     }
1570 }
1571
1572 declare_lint_pass!(
1573     /// Lint constants that are erroneous.
1574     /// Without this lint, we might not get any diagnostic if the constant is
1575     /// unused within this crate, even though downstream crates can't use it
1576     /// without producing an error.
1577     UnusedBrokenConst => []
1578 );
1579
1580 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
1581     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1582         match it.kind {
1583             hir::ItemKind::Const(_, body_id) => {
1584                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1585                 // trigger the query once for all constants since that will already report the errors
1586                 cx.tcx.ensure().const_eval_poly(def_id);
1587             }
1588             hir::ItemKind::Static(_, _, body_id) => {
1589                 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1590                 cx.tcx.ensure().eval_static_initializer(def_id);
1591             }
1592             _ => {}
1593         }
1594     }
1595 }
1596
1597 declare_lint! {
1598     /// The `trivial_bounds` lint detects trait bounds that don't depend on
1599     /// any type parameters.
1600     ///
1601     /// ### Example
1602     ///
1603     /// ```rust
1604     /// #![feature(trivial_bounds)]
1605     /// pub struct A where i32: Copy;
1606     /// ```
1607     ///
1608     /// {{produces}}
1609     ///
1610     /// ### Explanation
1611     ///
1612     /// Usually you would not write a trait bound that you know is always
1613     /// true, or never true. However, when using macros, the macro may not
1614     /// know whether or not the constraint would hold or not at the time when
1615     /// generating the code. Currently, the compiler does not alert you if the
1616     /// constraint is always true, and generates an error if it is never true.
1617     /// The `trivial_bounds` feature changes this to be a warning in both
1618     /// cases, giving macros more freedom and flexibility to generate code,
1619     /// while still providing a signal when writing non-macro code that
1620     /// something is amiss.
1621     ///
1622     /// See [RFC 2056] for more details. This feature is currently only
1623     /// available on the nightly channel, see [tracking issue #48214].
1624     ///
1625     /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1626     /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1627     TRIVIAL_BOUNDS,
1628     Warn,
1629     "these bounds don't depend on an type parameters"
1630 }
1631
1632 declare_lint_pass!(
1633     /// Lint for trait and lifetime bounds that don't depend on type parameters
1634     /// which either do nothing, or stop the item from being used.
1635     TrivialConstraints => [TRIVIAL_BOUNDS]
1636 );
1637
1638 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1639     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1640         use rustc_middle::ty::visit::TypeVisitable;
1641         use rustc_middle::ty::Clause;
1642         use rustc_middle::ty::PredicateKind::*;
1643
1644         if cx.tcx.features().trivial_bounds {
1645             let predicates = cx.tcx.predicates_of(item.owner_id);
1646             for &(predicate, span) in predicates.predicates {
1647                 let predicate_kind_name = match predicate.kind().skip_binder() {
1648                     Clause(Clause::Trait(..)) => "trait",
1649                     Clause(Clause::TypeOutlives(..)) |
1650                     Clause(Clause::RegionOutlives(..)) => "lifetime",
1651
1652                     // Ignore projections, as they can only be global
1653                     // if the trait bound is global
1654                     Clause(Clause::Projection(..)) |
1655                     // Ignore bounds that a user can't type
1656                     WellFormed(..) |
1657                     ObjectSafe(..) |
1658                     ClosureKind(..) |
1659                     Subtype(..) |
1660                     Coerce(..) |
1661                     ConstEvaluatable(..) |
1662                     ConstEquate(..) |
1663                     Ambiguous |
1664                     TypeWellFormedFromEnv(..) => continue,
1665                 };
1666                 if predicate.is_global() {
1667                     cx.struct_span_lint(
1668                         TRIVIAL_BOUNDS,
1669                         span,
1670                         fluent::lint_builtin_trivial_bounds,
1671                         |lint| {
1672                             lint.set_arg("predicate_kind_name", predicate_kind_name)
1673                                 .set_arg("predicate", predicate)
1674                         },
1675                     );
1676                 }
1677             }
1678         }
1679     }
1680 }
1681
1682 declare_lint_pass!(
1683     /// Does nothing as a lint pass, but registers some `Lint`s
1684     /// which are used by other parts of the compiler.
1685     SoftLints => [
1686         WHILE_TRUE,
1687         BOX_POINTERS,
1688         NON_SHORTHAND_FIELD_PATTERNS,
1689         UNSAFE_CODE,
1690         MISSING_DOCS,
1691         MISSING_COPY_IMPLEMENTATIONS,
1692         MISSING_DEBUG_IMPLEMENTATIONS,
1693         ANONYMOUS_PARAMETERS,
1694         UNUSED_DOC_COMMENTS,
1695         NO_MANGLE_CONST_ITEMS,
1696         NO_MANGLE_GENERIC_ITEMS,
1697         MUTABLE_TRANSMUTES,
1698         UNSTABLE_FEATURES,
1699         UNREACHABLE_PUB,
1700         TYPE_ALIAS_BOUNDS,
1701         TRIVIAL_BOUNDS
1702     ]
1703 );
1704
1705 declare_lint! {
1706     /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1707     /// pattern], which is deprecated.
1708     ///
1709     /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1710     ///
1711     /// ### Example
1712     ///
1713     /// ```rust,edition2018
1714     /// let x = 123;
1715     /// match x {
1716     ///     0...100 => {}
1717     ///     _ => {}
1718     /// }
1719     /// ```
1720     ///
1721     /// {{produces}}
1722     ///
1723     /// ### Explanation
1724     ///
1725     /// The `...` range pattern syntax was changed to `..=` to avoid potential
1726     /// confusion with the [`..` range expression]. Use the new form instead.
1727     ///
1728     /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1729     pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1730     Warn,
1731     "`...` range patterns are deprecated",
1732     @future_incompatible = FutureIncompatibleInfo {
1733         reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1734         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1735     };
1736 }
1737
1738 #[derive(Default)]
1739 pub struct EllipsisInclusiveRangePatterns {
1740     /// If `Some(_)`, suppress all subsequent pattern
1741     /// warnings for better diagnostics.
1742     node_id: Option<ast::NodeId>,
1743 }
1744
1745 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1746
1747 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1748     fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1749         if self.node_id.is_some() {
1750             // Don't recursively warn about patterns inside range endpoints.
1751             return;
1752         }
1753
1754         use self::ast::{PatKind, RangeSyntax::DotDotDot};
1755
1756         /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1757         /// corresponding to the ellipsis.
1758         fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1759             match &pat.kind {
1760                 PatKind::Range(
1761                     a,
1762                     Some(b),
1763                     Spanned { span, node: RangeEnd::Included(DotDotDot) },
1764                 ) => Some((a.as_deref(), b, *span)),
1765                 _ => None,
1766             }
1767         }
1768
1769         let (parenthesise, endpoints) = match &pat.kind {
1770             PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1771             _ => (false, matches_ellipsis_pat(pat)),
1772         };
1773
1774         if let Some((start, end, join)) = endpoints {
1775             let msg = fluent::lint_builtin_ellipsis_inclusive_range_patterns;
1776             let suggestion = fluent::suggestion;
1777             if parenthesise {
1778                 self.node_id = Some(pat.id);
1779                 let end = expr_to_string(&end);
1780                 let replace = match start {
1781                     Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1782                     None => format!("&(..={})", end),
1783                 };
1784                 if join.edition() >= Edition::Edition2021 {
1785                     cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1786                         span: pat.span,
1787                         suggestion: pat.span,
1788                         replace,
1789                     });
1790                 } else {
1791                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, msg, |lint| {
1792                         lint.span_suggestion(
1793                             pat.span,
1794                             suggestion,
1795                             replace,
1796                             Applicability::MachineApplicable,
1797                         )
1798                     });
1799                 }
1800             } else {
1801                 let replace = "..=";
1802                 if join.edition() >= Edition::Edition2021 {
1803                     cx.sess().emit_err(BuiltinEllpisisInclusiveRangePatterns {
1804                         span: pat.span,
1805                         suggestion: join,
1806                         replace: replace.to_string(),
1807                     });
1808                 } else {
1809                     cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, msg, |lint| {
1810                         lint.span_suggestion_short(
1811                             join,
1812                             suggestion,
1813                             replace,
1814                             Applicability::MachineApplicable,
1815                         )
1816                     });
1817                 }
1818             };
1819         }
1820     }
1821
1822     fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1823         if let Some(node_id) = self.node_id {
1824             if pat.id == node_id {
1825                 self.node_id = None
1826             }
1827         }
1828     }
1829 }
1830
1831 declare_lint! {
1832     /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1833     /// that are not able to be run by the test harness because they are in a
1834     /// position where they are not nameable.
1835     ///
1836     /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1837     ///
1838     /// ### Example
1839     ///
1840     /// ```rust,test
1841     /// fn main() {
1842     ///     #[test]
1843     ///     fn foo() {
1844     ///         // This test will not fail because it does not run.
1845     ///         assert_eq!(1, 2);
1846     ///     }
1847     /// }
1848     /// ```
1849     ///
1850     /// {{produces}}
1851     ///
1852     /// ### Explanation
1853     ///
1854     /// In order for the test harness to run a test, the test function must be
1855     /// located in a position where it can be accessed from the crate root.
1856     /// This generally means it must be defined in a module, and not anywhere
1857     /// else such as inside another function. The compiler previously allowed
1858     /// this without an error, so a lint was added as an alert that a test is
1859     /// not being used. Whether or not this should be allowed has not yet been
1860     /// decided, see [RFC 2471] and [issue #36629].
1861     ///
1862     /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1863     /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1864     UNNAMEABLE_TEST_ITEMS,
1865     Warn,
1866     "detects an item that cannot be named being marked as `#[test_case]`",
1867     report_in_external_macro
1868 }
1869
1870 pub struct UnnameableTestItems {
1871     boundary: Option<hir::OwnerId>, // Id of the item under which things are not nameable
1872     items_nameable: bool,
1873 }
1874
1875 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1876
1877 impl UnnameableTestItems {
1878     pub fn new() -> Self {
1879         Self { boundary: None, items_nameable: true }
1880     }
1881 }
1882
1883 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
1884     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1885         if self.items_nameable {
1886             if let hir::ItemKind::Mod(..) = it.kind {
1887             } else {
1888                 self.items_nameable = false;
1889                 self.boundary = Some(it.owner_id);
1890             }
1891             return;
1892         }
1893
1894         let attrs = cx.tcx.hir().attrs(it.hir_id());
1895         if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1896             cx.struct_span_lint(
1897                 UNNAMEABLE_TEST_ITEMS,
1898                 attr.span,
1899                 fluent::lint_builtin_unnameable_test_items,
1900                 |lint| lint,
1901             );
1902         }
1903     }
1904
1905     fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1906         if !self.items_nameable && self.boundary == Some(it.owner_id) {
1907             self.items_nameable = true;
1908         }
1909     }
1910 }
1911
1912 declare_lint! {
1913     /// The `keyword_idents` lint detects edition keywords being used as an
1914     /// identifier.
1915     ///
1916     /// ### Example
1917     ///
1918     /// ```rust,edition2015,compile_fail
1919     /// #![deny(keyword_idents)]
1920     /// // edition 2015
1921     /// fn dyn() {}
1922     /// ```
1923     ///
1924     /// {{produces}}
1925     ///
1926     /// ### Explanation
1927     ///
1928     /// Rust [editions] allow the language to evolve without breaking
1929     /// backwards compatibility. This lint catches code that uses new keywords
1930     /// that are added to the language that are used as identifiers (such as a
1931     /// variable name, function name, etc.). If you switch the compiler to a
1932     /// new edition without updating the code, then it will fail to compile if
1933     /// you are using a new keyword as an identifier.
1934     ///
1935     /// You can manually change the identifiers to a non-keyword, or use a
1936     /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1937     ///
1938     /// This lint solves the problem automatically. It is "allow" by default
1939     /// because the code is perfectly valid in older editions. The [`cargo
1940     /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1941     /// and automatically apply the suggested fix from the compiler (which is
1942     /// to use a raw identifier). This provides a completely automated way to
1943     /// update old code for a new edition.
1944     ///
1945     /// [editions]: https://doc.rust-lang.org/edition-guide/
1946     /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1947     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1948     pub KEYWORD_IDENTS,
1949     Allow,
1950     "detects edition keywords being used as an identifier",
1951     @future_incompatible = FutureIncompatibleInfo {
1952         reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1953         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1954     };
1955 }
1956
1957 declare_lint_pass!(
1958     /// Check for uses of edition keywords used as an identifier.
1959     KeywordIdents => [KEYWORD_IDENTS]
1960 );
1961
1962 struct UnderMacro(bool);
1963
1964 impl KeywordIdents {
1965     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1966         for tt in tokens.into_trees() {
1967             match tt {
1968                 // Only report non-raw idents.
1969                 TokenTree::Token(token, _) => {
1970                     if let Some((ident, false)) = token.ident() {
1971                         self.check_ident_token(cx, UnderMacro(true), ident);
1972                     }
1973                 }
1974                 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1975             }
1976         }
1977     }
1978
1979     fn check_ident_token(
1980         &mut self,
1981         cx: &EarlyContext<'_>,
1982         UnderMacro(under_macro): UnderMacro,
1983         ident: Ident,
1984     ) {
1985         let next_edition = match cx.sess().edition() {
1986             Edition::Edition2015 => {
1987                 match ident.name {
1988                     kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1989
1990                     // rust-lang/rust#56327: Conservatively do not
1991                     // attempt to report occurrences of `dyn` within
1992                     // macro definitions or invocations, because `dyn`
1993                     // can legitimately occur as a contextual keyword
1994                     // in 2015 code denoting its 2018 meaning, and we
1995                     // do not want rustfix to inject bugs into working
1996                     // code by rewriting such occurrences.
1997                     //
1998                     // But if we see `dyn` outside of a macro, we know
1999                     // its precise role in the parsed AST and thus are
2000                     // assured this is truly an attempt to use it as
2001                     // an identifier.
2002                     kw::Dyn if !under_macro => Edition::Edition2018,
2003
2004                     _ => return,
2005                 }
2006             }
2007
2008             // There are no new keywords yet for the 2018 edition and beyond.
2009             _ => return,
2010         };
2011
2012         // Don't lint `r#foo`.
2013         if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2014             return;
2015         }
2016
2017         cx.struct_span_lint(
2018             KEYWORD_IDENTS,
2019             ident.span,
2020             fluent::lint_builtin_keyword_idents,
2021             |lint| {
2022                 lint.set_arg("kw", ident.clone()).set_arg("next", next_edition).span_suggestion(
2023                     ident.span,
2024                     fluent::suggestion,
2025                     format!("r#{}", ident),
2026                     Applicability::MachineApplicable,
2027                 )
2028             },
2029         );
2030     }
2031 }
2032
2033 impl EarlyLintPass for KeywordIdents {
2034     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
2035         self.check_tokens(cx, mac_def.body.tokens.clone());
2036     }
2037     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2038         self.check_tokens(cx, mac.args.tokens.clone());
2039     }
2040     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2041         self.check_ident_token(cx, UnderMacro(false), ident);
2042     }
2043 }
2044
2045 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2046
2047 impl ExplicitOutlivesRequirements {
2048     fn lifetimes_outliving_lifetime<'tcx>(
2049         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2050         def_id: DefId,
2051     ) -> Vec<ty::Region<'tcx>> {
2052         inferred_outlives
2053             .iter()
2054             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2055                 ty::PredicateKind::Clause(ty::Clause::RegionOutlives(ty::OutlivesPredicate(
2056                     a,
2057                     b,
2058                 ))) => match *a {
2059                     ty::ReEarlyBound(ebr) if ebr.def_id == def_id => Some(b),
2060                     _ => None,
2061                 },
2062                 _ => None,
2063             })
2064             .collect()
2065     }
2066
2067     fn lifetimes_outliving_type<'tcx>(
2068         inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2069         index: u32,
2070     ) -> Vec<ty::Region<'tcx>> {
2071         inferred_outlives
2072             .iter()
2073             .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2074                 ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
2075                     a,
2076                     b,
2077                 ))) => a.is_param(index).then_some(b),
2078                 _ => None,
2079             })
2080             .collect()
2081     }
2082
2083     fn collect_outlives_bound_spans<'tcx>(
2084         &self,
2085         tcx: TyCtxt<'tcx>,
2086         bounds: &hir::GenericBounds<'_>,
2087         inferred_outlives: &[ty::Region<'tcx>],
2088     ) -> Vec<(usize, Span)> {
2089         use rustc_middle::middle::resolve_lifetime::Region;
2090
2091         bounds
2092             .iter()
2093             .enumerate()
2094             .filter_map(|(i, bound)| {
2095                 if let hir::GenericBound::Outlives(lifetime) = bound {
2096                     let is_inferred = match tcx.named_region(lifetime.hir_id) {
2097                         Some(Region::EarlyBound(def_id)) => inferred_outlives.iter().any(|r| {
2098                             if let ty::ReEarlyBound(ebr) = **r {
2099                                 ebr.def_id == def_id
2100                             } else {
2101                                 false
2102                             }
2103                         }),
2104                         _ => false,
2105                     };
2106                     is_inferred.then_some((i, bound.span()))
2107                 } else {
2108                     None
2109                 }
2110             })
2111             .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
2112             .collect()
2113     }
2114
2115     fn consolidate_outlives_bound_spans(
2116         &self,
2117         lo: Span,
2118         bounds: &hir::GenericBounds<'_>,
2119         bound_spans: Vec<(usize, Span)>,
2120     ) -> Vec<Span> {
2121         if bounds.is_empty() {
2122             return Vec::new();
2123         }
2124         if bound_spans.len() == bounds.len() {
2125             let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2126             // If all bounds are inferable, we want to delete the colon, so
2127             // start from just after the parameter (span passed as argument)
2128             vec![lo.to(last_bound_span)]
2129         } else {
2130             let mut merged = Vec::new();
2131             let mut last_merged_i = None;
2132
2133             let mut from_start = true;
2134             for (i, bound_span) in bound_spans {
2135                 match last_merged_i {
2136                     // If the first bound is inferable, our span should also eat the leading `+`.
2137                     None if i == 0 => {
2138                         merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2139                         last_merged_i = Some(0);
2140                     }
2141                     // If consecutive bounds are inferable, merge their spans
2142                     Some(h) if i == h + 1 => {
2143                         if let Some(tail) = merged.last_mut() {
2144                             // Also eat the trailing `+` if the first
2145                             // more-than-one bound is inferable
2146                             let to_span = if from_start && i < bounds.len() {
2147                                 bounds[i + 1].span().shrink_to_lo()
2148                             } else {
2149                                 bound_span
2150                             };
2151                             *tail = tail.to(to_span);
2152                             last_merged_i = Some(i);
2153                         } else {
2154                             bug!("another bound-span visited earlier");
2155                         }
2156                     }
2157                     _ => {
2158                         // When we find a non-inferable bound, subsequent inferable bounds
2159                         // won't be consecutive from the start (and we'll eat the leading
2160                         // `+` rather than the trailing one)
2161                         from_start = false;
2162                         merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2163                         last_merged_i = Some(i);
2164                     }
2165                 }
2166             }
2167             merged
2168         }
2169     }
2170 }
2171
2172 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2173     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2174         use rustc_middle::middle::resolve_lifetime::Region;
2175
2176         let def_id = item.owner_id.def_id;
2177         if let hir::ItemKind::Struct(_, ref hir_generics)
2178         | hir::ItemKind::Enum(_, ref hir_generics)
2179         | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2180         {
2181             let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2182             if inferred_outlives.is_empty() {
2183                 return;
2184             }
2185
2186             let ty_generics = cx.tcx.generics_of(def_id);
2187
2188             let mut bound_count = 0;
2189             let mut lint_spans = Vec::new();
2190             let mut where_lint_spans = Vec::new();
2191             let mut dropped_predicate_count = 0;
2192             let num_predicates = hir_generics.predicates.len();
2193             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2194                 let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
2195                     hir::WherePredicate::RegionPredicate(predicate) => {
2196                         if let Some(Region::EarlyBound(region_def_id)) =
2197                             cx.tcx.named_region(predicate.lifetime.hir_id)
2198                         {
2199                             (
2200                                 Self::lifetimes_outliving_lifetime(
2201                                     inferred_outlives,
2202                                     region_def_id,
2203                                 ),
2204                                 &predicate.bounds,
2205                                 predicate.span,
2206                                 predicate.in_where_clause,
2207                             )
2208                         } else {
2209                             continue;
2210                         }
2211                     }
2212                     hir::WherePredicate::BoundPredicate(predicate) => {
2213                         // FIXME we can also infer bounds on associated types,
2214                         // and should check for them here.
2215                         match predicate.bounded_ty.kind {
2216                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2217                                 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2218                                     continue
2219                                 };
2220                                 let index = ty_generics.param_def_id_to_index[&def_id];
2221                                 (
2222                                     Self::lifetimes_outliving_type(inferred_outlives, index),
2223                                     &predicate.bounds,
2224                                     predicate.span,
2225                                     predicate.origin == PredicateOrigin::WhereClause,
2226                                 )
2227                             }
2228                             _ => {
2229                                 continue;
2230                             }
2231                         }
2232                     }
2233                     _ => continue,
2234                 };
2235                 if relevant_lifetimes.is_empty() {
2236                     continue;
2237                 }
2238
2239                 let bound_spans =
2240                     self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
2241                 bound_count += bound_spans.len();
2242
2243                 let drop_predicate = bound_spans.len() == bounds.len();
2244                 if drop_predicate {
2245                     dropped_predicate_count += 1;
2246                 }
2247
2248                 if drop_predicate && !in_where_clause {
2249                     lint_spans.push(span);
2250                 } else if drop_predicate && i + 1 < num_predicates {
2251                     // If all the bounds on a predicate were inferable and there are
2252                     // further predicates, we want to eat the trailing comma.
2253                     let next_predicate_span = hir_generics.predicates[i + 1].span();
2254                     where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2255                 } else {
2256                     where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2257                         span.shrink_to_lo(),
2258                         bounds,
2259                         bound_spans,
2260                     ));
2261                 }
2262             }
2263
2264             // If all predicates are inferable, drop the entire clause
2265             // (including the `where`)
2266             if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
2267             {
2268                 let where_span = hir_generics.where_clause_span;
2269                 // Extend the where clause back to the closing `>` of the
2270                 // generics, except for tuple struct, which have the `where`
2271                 // after the fields of the struct.
2272                 let full_where_span =
2273                     if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2274                         where_span
2275                     } else {
2276                         hir_generics.span.shrink_to_hi().to(where_span)
2277                     };
2278                 lint_spans.push(full_where_span);
2279             } else {
2280                 lint_spans.extend(where_lint_spans);
2281             }
2282
2283             if !lint_spans.is_empty() {
2284                 cx.struct_span_lint(
2285                     EXPLICIT_OUTLIVES_REQUIREMENTS,
2286                     lint_spans.clone(),
2287                     fluent::lint_builtin_explicit_outlives,
2288                     |lint| {
2289                         lint.set_arg("count", bound_count).multipart_suggestion(
2290                             fluent::suggestion,
2291                             lint_spans
2292                                 .into_iter()
2293                                 .map(|span| (span, String::new()))
2294                                 .collect::<Vec<_>>(),
2295                             Applicability::MachineApplicable,
2296                         )
2297                     },
2298                 );
2299             }
2300         }
2301     }
2302 }
2303
2304 declare_lint! {
2305     /// The `incomplete_features` lint detects unstable features enabled with
2306     /// the [`feature` attribute] that may function improperly in some or all
2307     /// cases.
2308     ///
2309     /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2310     ///
2311     /// ### Example
2312     ///
2313     /// ```rust
2314     /// #![feature(generic_const_exprs)]
2315     /// ```
2316     ///
2317     /// {{produces}}
2318     ///
2319     /// ### Explanation
2320     ///
2321     /// Although it is encouraged for people to experiment with unstable
2322     /// features, some of them are known to be incomplete or faulty. This lint
2323     /// is a signal that the feature has not yet been finished, and you may
2324     /// experience problems with it.
2325     pub INCOMPLETE_FEATURES,
2326     Warn,
2327     "incomplete features that may function improperly in some or all cases"
2328 }
2329
2330 declare_lint_pass!(
2331     /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2332     IncompleteFeatures => [INCOMPLETE_FEATURES]
2333 );
2334
2335 impl EarlyLintPass for IncompleteFeatures {
2336     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2337         let features = cx.sess().features_untracked();
2338         features
2339             .declared_lang_features
2340             .iter()
2341             .map(|(name, span, _)| (name, span))
2342             .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2343             .filter(|(&name, _)| features.incomplete(name))
2344             .for_each(|(&name, &span)| {
2345                 cx.struct_span_lint(
2346                     INCOMPLETE_FEATURES,
2347                     span,
2348                     fluent::lint_builtin_incomplete_features,
2349                     |lint| {
2350                         lint.set_arg("name", name);
2351                         if let Some(n) =
2352                             rustc_feature::find_feature_issue(name, GateIssue::Language)
2353                         {
2354                             lint.set_arg("n", n);
2355                             lint.note(fluent::note);
2356                         }
2357                         if HAS_MIN_FEATURES.contains(&name) {
2358                             lint.help(fluent::help);
2359                         }
2360                         lint
2361                     },
2362                 )
2363             });
2364     }
2365 }
2366
2367 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2368
2369 declare_lint! {
2370     /// The `invalid_value` lint detects creating a value that is not valid,
2371     /// such as a null reference.
2372     ///
2373     /// ### Example
2374     ///
2375     /// ```rust,no_run
2376     /// # #![allow(unused)]
2377     /// unsafe {
2378     ///     let x: &'static i32 = std::mem::zeroed();
2379     /// }
2380     /// ```
2381     ///
2382     /// {{produces}}
2383     ///
2384     /// ### Explanation
2385     ///
2386     /// In some situations the compiler can detect that the code is creating
2387     /// an invalid value, which should be avoided.
2388     ///
2389     /// In particular, this lint will check for improper use of
2390     /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2391     /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2392     /// lint should provide extra information to indicate what the problem is
2393     /// and a possible solution.
2394     ///
2395     /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2396     /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2397     /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2398     /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2399     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2400     pub INVALID_VALUE,
2401     Warn,
2402     "an invalid value is being created (such as a null reference)"
2403 }
2404
2405 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2406
2407 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2408     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2409         #[derive(Debug, Copy, Clone, PartialEq)]
2410         enum InitKind {
2411             Zeroed,
2412             Uninit,
2413         }
2414
2415         /// Information about why a type cannot be initialized this way.
2416         struct InitError {
2417             message: String,
2418             /// Spans from struct fields and similar that can be obtained from just the type.
2419             span: Option<Span>,
2420             /// Used to report a trace through adts.
2421             nested: Option<Box<InitError>>,
2422         }
2423         impl InitError {
2424             fn spanned(self, span: Span) -> InitError {
2425                 Self { span: Some(span), ..self }
2426             }
2427
2428             fn nested(self, nested: impl Into<Option<InitError>>) -> InitError {
2429                 assert!(self.nested.is_none());
2430                 Self { nested: nested.into().map(Box::new), ..self }
2431             }
2432         }
2433
2434         impl<'a> From<&'a str> for InitError {
2435             fn from(s: &'a str) -> Self {
2436                 s.to_owned().into()
2437             }
2438         }
2439         impl From<String> for InitError {
2440             fn from(message: String) -> Self {
2441                 Self { message, span: None, nested: None }
2442             }
2443         }
2444
2445         /// Test if this constant is all-0.
2446         fn is_zero(expr: &hir::Expr<'_>) -> bool {
2447             use hir::ExprKind::*;
2448             use rustc_ast::LitKind::*;
2449             match &expr.kind {
2450                 Lit(lit) => {
2451                     if let Int(i, _) = lit.node {
2452                         i == 0
2453                     } else {
2454                         false
2455                     }
2456                 }
2457                 Tup(tup) => tup.iter().all(is_zero),
2458                 _ => false,
2459             }
2460         }
2461
2462         /// Determine if this expression is a "dangerous initialization".
2463         fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2464             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2465                 // Find calls to `mem::{uninitialized,zeroed}` methods.
2466                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2467                     let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2468                     match cx.tcx.get_diagnostic_name(def_id) {
2469                         Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2470                         Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2471                         Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2472                         _ => {}
2473                     }
2474                 }
2475             } else if let hir::ExprKind::MethodCall(_, receiver, ..) = expr.kind {
2476                 // Find problematic calls to `MaybeUninit::assume_init`.
2477                 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2478                 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2479                     // This is a call to *some* method named `assume_init`.
2480                     // See if the `self` parameter is one of the dangerous constructors.
2481                     if let hir::ExprKind::Call(ref path_expr, _) = receiver.kind {
2482                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2483                             let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2484                             match cx.tcx.get_diagnostic_name(def_id) {
2485                                 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2486                                 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2487                                 _ => {}
2488                             }
2489                         }
2490                     }
2491                 }
2492             }
2493
2494             None
2495         }
2496
2497         fn variant_find_init_error<'tcx>(
2498             cx: &LateContext<'tcx>,
2499             ty: Ty<'tcx>,
2500             variant: &VariantDef,
2501             substs: ty::SubstsRef<'tcx>,
2502             descr: &str,
2503             init: InitKind,
2504         ) -> Option<InitError> {
2505             let mut field_err = variant.fields.iter().find_map(|field| {
2506                 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|mut err| {
2507                     if !field.did.is_local() {
2508                         err
2509                     } else if err.span.is_none() {
2510                         err.span = Some(cx.tcx.def_span(field.did));
2511                         write!(&mut err.message, " (in this {descr})").unwrap();
2512                         err
2513                     } else {
2514                         InitError::from(format!("in this {descr}"))
2515                             .spanned(cx.tcx.def_span(field.did))
2516                             .nested(err)
2517                     }
2518                 })
2519             });
2520
2521             // Check if this ADT has a constrained layout (like `NonNull` and friends).
2522             if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty)) {
2523                 if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &layout.abi {
2524                     let range = scalar.valid_range(cx);
2525                     let msg = if !range.contains(0) {
2526                         "must be non-null"
2527                     } else if init == InitKind::Uninit && !scalar.is_always_valid(cx) {
2528                         // Prefer reporting on the fields over the entire struct for uninit,
2529                         // as the information bubbles out and it may be unclear why the type can't
2530                         // be null from just its outside signature.
2531
2532                         "must be initialized inside its custom valid range"
2533                     } else {
2534                         return field_err;
2535                     };
2536                     if let Some(field_err) = &mut field_err {
2537                         // Most of the time, if the field error is the same as the struct error,
2538                         // the struct error only happens because of the field error.
2539                         if field_err.message.contains(msg) {
2540                             field_err.message = format!("because {}", field_err.message);
2541                         }
2542                     }
2543                     return Some(InitError::from(format!("`{ty}` {msg}")).nested(field_err));
2544                 }
2545             }
2546             field_err
2547         }
2548
2549         /// Return `Some` only if we are sure this type does *not*
2550         /// allow zero initialization.
2551         fn ty_find_init_error<'tcx>(
2552             cx: &LateContext<'tcx>,
2553             ty: Ty<'tcx>,
2554             init: InitKind,
2555         ) -> Option<InitError> {
2556             use rustc_type_ir::sty::TyKind::*;
2557             match ty.kind() {
2558                 // Primitive types that don't like 0 as a value.
2559                 Ref(..) => Some("references must be non-null".into()),
2560                 Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),
2561                 FnPtr(..) => Some("function pointers must be non-null".into()),
2562                 Never => Some("the `!` type has no valid value".into()),
2563                 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2564                 // raw ptr to dyn Trait
2565                 {
2566                     Some("the vtable of a wide raw pointer must be non-null".into())
2567                 }
2568                 // Primitive types with other constraints.
2569                 Bool if init == InitKind::Uninit => {
2570                     Some("booleans must be either `true` or `false`".into())
2571                 }
2572                 Char if init == InitKind::Uninit => {
2573                     Some("characters must be a valid Unicode codepoint".into())
2574                 }
2575                 Int(_) | Uint(_) if init == InitKind::Uninit => {
2576                     Some("integers must be initialized".into())
2577                 }
2578                 Float(_) if init == InitKind::Uninit => Some("floats must be initialized".into()),
2579                 RawPtr(_) if init == InitKind::Uninit => {
2580                     Some("raw pointers must be initialized".into())
2581                 }
2582                 // Recurse and checks for some compound types. (but not unions)
2583                 Adt(adt_def, substs) if !adt_def.is_union() => {
2584                     // Handle structs.
2585                     if adt_def.is_struct() {
2586                         return variant_find_init_error(
2587                             cx,
2588                             ty,
2589                             adt_def.non_enum_variant(),
2590                             substs,
2591                             "struct field",
2592                             init,
2593                         );
2594                     }
2595                     // And now, enums.
2596                     let span = cx.tcx.def_span(adt_def.did());
2597                     let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
2598                         let definitely_inhabited = match variant
2599                             .inhabited_predicate(cx.tcx, *adt_def)
2600                             .subst(cx.tcx, substs)
2601                             .apply_any_module(cx.tcx, cx.param_env)
2602                         {
2603                             // Entirely skip uninhbaited variants.
2604                             Some(false) => return None,
2605                             // Forward the others, but remember which ones are definitely inhabited.
2606                             Some(true) => true,
2607                             None => false,
2608                         };
2609                         Some((variant, definitely_inhabited))
2610                     });
2611                     let Some(first_variant) = potential_variants.next() else {
2612                         return Some(InitError::from("enums with no inhabited variants have no valid value").spanned(span));
2613                     };
2614                     // So we have at least one potentially inhabited variant. Might we have two?
2615                     let Some(second_variant) = potential_variants.next() else {
2616                         // There is only one potentially inhabited variant. So we can recursively check that variant!
2617                         return variant_find_init_error(
2618                             cx,
2619                             ty,
2620                             &first_variant.0,
2621                             substs,
2622                             "field of the only potentially inhabited enum variant",
2623                             init,
2624                         );
2625                     };
2626                     // So we have at least two potentially inhabited variants.
2627                     // If we can prove that we have at least two *definitely* inhabited variants,
2628                     // then we have a tag and hence leaving this uninit is definitely disallowed.
2629                     // (Leaving it zeroed could be okay, depending on which variant is encoded as zero tag.)
2630                     if init == InitKind::Uninit {
2631                         let definitely_inhabited = (first_variant.1 as usize)
2632                             + (second_variant.1 as usize)
2633                             + potential_variants
2634                                 .filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
2635                                 .count();
2636                         if definitely_inhabited > 1 {
2637                             return Some(InitError::from(
2638                                 "enums with multiple inhabited variants have to be initialized to a variant",
2639                             ).spanned(span));
2640                         }
2641                     }
2642                     // We couldn't find anything wrong here.
2643                     None
2644                 }
2645                 Tuple(..) => {
2646                     // Proceed recursively, check all fields.
2647                     ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2648                 }
2649                 Array(ty, len) => {
2650                     if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2651                         // Array length known at array non-empty -- recurse.
2652                         ty_find_init_error(cx, *ty, init)
2653                     } else {
2654                         // Empty array or size unknown.
2655                         None
2656                     }
2657                 }
2658                 // Conservative fallback.
2659                 _ => None,
2660             }
2661         }
2662
2663         if let Some(init) = is_dangerous_init(cx, expr) {
2664             // This conjures an instance of a type out of nothing,
2665             // using zeroed or uninitialized memory.
2666             // We are extremely conservative with what we warn about.
2667             let conjured_ty = cx.typeck_results().expr_ty(expr);
2668             if let Some(mut err) = with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
2669             {
2670                 // FIXME(davidtwco): make translatable
2671                 cx.struct_span_lint(
2672                     INVALID_VALUE,
2673                     expr.span,
2674                     DelayDm(|| {
2675                         format!(
2676                             "the type `{}` does not permit {}",
2677                             conjured_ty,
2678                             match init {
2679                                 InitKind::Zeroed => "zero-initialization",
2680                                 InitKind::Uninit => "being left uninitialized",
2681                             },
2682                         )
2683                     }),
2684                     |lint| {
2685                         lint.span_label(
2686                             expr.span,
2687                             "this code causes undefined behavior when executed",
2688                         );
2689                         lint.span_label(
2690                             expr.span,
2691                             "help: use `MaybeUninit<T>` instead, \
2692                             and only call `assume_init` after initialization is done",
2693                         );
2694                         loop {
2695                             if let Some(span) = err.span {
2696                                 lint.span_note(span, &err.message);
2697                             } else {
2698                                 lint.note(&err.message);
2699                             }
2700                             if let Some(e) = err.nested {
2701                                 err = *e;
2702                             } else {
2703                                 break;
2704                             }
2705                         }
2706                         lint
2707                     },
2708                 );
2709             }
2710         }
2711     }
2712 }
2713
2714 declare_lint! {
2715     /// The `clashing_extern_declarations` lint detects when an `extern fn`
2716     /// has been declared with the same name but different types.
2717     ///
2718     /// ### Example
2719     ///
2720     /// ```rust
2721     /// mod m {
2722     ///     extern "C" {
2723     ///         fn foo();
2724     ///     }
2725     /// }
2726     ///
2727     /// extern "C" {
2728     ///     fn foo(_: u32);
2729     /// }
2730     /// ```
2731     ///
2732     /// {{produces}}
2733     ///
2734     /// ### Explanation
2735     ///
2736     /// Because two symbols of the same name cannot be resolved to two
2737     /// different functions at link time, and one function cannot possibly
2738     /// have two types, a clashing extern declaration is almost certainly a
2739     /// mistake. Check to make sure that the `extern` definitions are correct
2740     /// and equivalent, and possibly consider unifying them in one location.
2741     ///
2742     /// This lint does not run between crates because a project may have
2743     /// dependencies which both rely on the same extern function, but declare
2744     /// it in a different (but valid) way. For example, they may both declare
2745     /// an opaque type for one or more of the arguments (which would end up
2746     /// distinct types), or use types that are valid conversions in the
2747     /// language the `extern fn` is defined in. In these cases, the compiler
2748     /// can't say that the clashing declaration is incorrect.
2749     pub CLASHING_EXTERN_DECLARATIONS,
2750     Warn,
2751     "detects when an extern fn has been declared with the same name but different types"
2752 }
2753
2754 pub struct ClashingExternDeclarations {
2755     /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2756     /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2757     /// the symbol should be reported as a clashing declaration.
2758     // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2759     // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2760     seen_decls: FxHashMap<Symbol, HirId>,
2761 }
2762
2763 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2764 /// just from declaration itself. This is important because we don't want to report clashes on
2765 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2766 /// different name.
2767 enum SymbolName {
2768     /// The name of the symbol + the span of the annotation which introduced the link name.
2769     Link(Symbol, Span),
2770     /// No link name, so just the name of the symbol.
2771     Normal(Symbol),
2772 }
2773
2774 impl SymbolName {
2775     fn get_name(&self) -> Symbol {
2776         match self {
2777             SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2778         }
2779     }
2780 }
2781
2782 impl ClashingExternDeclarations {
2783     pub(crate) fn new() -> Self {
2784         ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2785     }
2786     /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2787     /// for the item, return its HirId without updating the set.
2788     fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2789         let did = fi.owner_id.to_def_id();
2790         let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2791         let name = Symbol::intern(tcx.symbol_name(instance).name);
2792         if let Some(&hir_id) = self.seen_decls.get(&name) {
2793             // Avoid updating the map with the new entry when we do find a collision. We want to
2794             // make sure we're always pointing to the first definition as the previous declaration.
2795             // This lets us avoid emitting "knock-on" diagnostics.
2796             Some(hir_id)
2797         } else {
2798             self.seen_decls.insert(name, fi.hir_id())
2799         }
2800     }
2801
2802     /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2803     /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2804     /// symbol's name.
2805     fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2806         if let Some((overridden_link_name, overridden_link_name_span)) =
2807             tcx.codegen_fn_attrs(fi.owner_id).link_name.map(|overridden_link_name| {
2808                 // FIXME: Instead of searching through the attributes again to get span
2809                 // information, we could have codegen_fn_attrs also give span information back for
2810                 // where the attribute was defined. However, until this is found to be a
2811                 // bottleneck, this does just fine.
2812                 (
2813                     overridden_link_name,
2814                     tcx.get_attr(fi.owner_id.to_def_id(), sym::link_name).unwrap().span,
2815                 )
2816             })
2817         {
2818             SymbolName::Link(overridden_link_name, overridden_link_name_span)
2819         } else {
2820             SymbolName::Normal(fi.ident.name)
2821         }
2822     }
2823
2824     /// Checks whether two types are structurally the same enough that the declarations shouldn't
2825     /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2826     /// with the same members (as the declarations shouldn't clash).
2827     fn structurally_same_type<'tcx>(
2828         cx: &LateContext<'tcx>,
2829         a: Ty<'tcx>,
2830         b: Ty<'tcx>,
2831         ckind: CItemKind,
2832     ) -> bool {
2833         fn structurally_same_type_impl<'tcx>(
2834             seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2835             cx: &LateContext<'tcx>,
2836             a: Ty<'tcx>,
2837             b: Ty<'tcx>,
2838             ckind: CItemKind,
2839         ) -> bool {
2840             debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2841             let tcx = cx.tcx;
2842
2843             // Given a transparent newtype, reach through and grab the inner
2844             // type unless the newtype makes the type non-null.
2845             let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2846                 let mut ty = ty;
2847                 loop {
2848                     if let ty::Adt(def, substs) = *ty.kind() {
2849                         let is_transparent = def.repr().transparent();
2850                         let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2851                         debug!(
2852                             "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2853                             ty, is_transparent, is_non_null
2854                         );
2855                         if is_transparent && !is_non_null {
2856                             debug_assert!(def.variants().len() == 1);
2857                             let v = &def.variant(VariantIdx::new(0));
2858                             ty = transparent_newtype_field(tcx, v)
2859                                 .expect(
2860                                     "single-variant transparent structure with zero-sized field",
2861                                 )
2862                                 .ty(tcx, substs);
2863                             continue;
2864                         }
2865                     }
2866                     debug!("non_transparent_ty -> {:?}", ty);
2867                     return ty;
2868                 }
2869             };
2870
2871             let a = non_transparent_ty(a);
2872             let b = non_transparent_ty(b);
2873
2874             if !seen_types.insert((a, b)) {
2875                 // We've encountered a cycle. There's no point going any further -- the types are
2876                 // structurally the same.
2877                 return true;
2878             }
2879             let tcx = cx.tcx;
2880             if a == b {
2881                 // All nominally-same types are structurally same, too.
2882                 true
2883             } else {
2884                 // Do a full, depth-first comparison between the two.
2885                 use rustc_type_ir::sty::TyKind::*;
2886                 let a_kind = a.kind();
2887                 let b_kind = b.kind();
2888
2889                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2890                     debug!("compare_layouts({:?}, {:?})", a, b);
2891                     let a_layout = &cx.layout_of(a)?.layout.abi();
2892                     let b_layout = &cx.layout_of(b)?.layout.abi();
2893                     debug!(
2894                         "comparing layouts: {:?} == {:?} = {}",
2895                         a_layout,
2896                         b_layout,
2897                         a_layout == b_layout
2898                     );
2899                     Ok(a_layout == b_layout)
2900                 };
2901
2902                 #[allow(rustc::usage_of_ty_tykind)]
2903                 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2904                     kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2905                 };
2906
2907                 ensure_sufficient_stack(|| {
2908                     match (a_kind, b_kind) {
2909                         (Adt(a_def, _), Adt(b_def, _)) => {
2910                             // We can immediately rule out these types as structurally same if
2911                             // their layouts differ.
2912                             match compare_layouts(a, b) {
2913                                 Ok(false) => return false,
2914                                 _ => (), // otherwise, continue onto the full, fields comparison
2915                             }
2916
2917                             // Grab a flattened representation of all fields.
2918                             let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2919                             let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2920
2921                             // Perform a structural comparison for each field.
2922                             a_fields.eq_by(
2923                                 b_fields,
2924                                 |&ty::FieldDef { did: a_did, .. },
2925                                  &ty::FieldDef { did: b_did, .. }| {
2926                                     structurally_same_type_impl(
2927                                         seen_types,
2928                                         cx,
2929                                         tcx.type_of(a_did),
2930                                         tcx.type_of(b_did),
2931                                         ckind,
2932                                     )
2933                                 },
2934                             )
2935                         }
2936                         (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2937                             // For arrays, we also check the constness of the type.
2938                             a_const.kind() == b_const.kind()
2939                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2940                         }
2941                         (Slice(a_ty), Slice(b_ty)) => {
2942                             structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2943                         }
2944                         (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2945                             a_tymut.mutbl == b_tymut.mutbl
2946                                 && structurally_same_type_impl(
2947                                     seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2948                                 )
2949                         }
2950                         (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2951                             // For structural sameness, we don't need the region to be same.
2952                             a_mut == b_mut
2953                                 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2954                         }
2955                         (FnDef(..), FnDef(..)) => {
2956                             let a_poly_sig = a.fn_sig(tcx);
2957                             let b_poly_sig = b.fn_sig(tcx);
2958
2959                             // We don't compare regions, but leaving bound regions around ICEs, so
2960                             // we erase them.
2961                             let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
2962                             let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
2963
2964                             (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2965                                 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2966                                 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2967                                     structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2968                                 })
2969                                 && structurally_same_type_impl(
2970                                     seen_types,
2971                                     cx,
2972                                     a_sig.output(),
2973                                     b_sig.output(),
2974                                     ckind,
2975                                 )
2976                         }
2977                         (Tuple(a_substs), Tuple(b_substs)) => {
2978                             a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2979                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2980                             })
2981                         }
2982                         // For these, it's not quite as easy to define structural-sameness quite so easily.
2983                         // For the purposes of this lint, take the conservative approach and mark them as
2984                         // not structurally same.
2985                         (Dynamic(..), Dynamic(..))
2986                         | (Error(..), Error(..))
2987                         | (Closure(..), Closure(..))
2988                         | (Generator(..), Generator(..))
2989                         | (GeneratorWitness(..), GeneratorWitness(..))
2990                         | (Projection(..), Projection(..))
2991                         | (Opaque(..), Opaque(..)) => false,
2992
2993                         // These definitely should have been caught above.
2994                         (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2995
2996                         // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2997                         // enum layout optimisation is being applied.
2998                         (Adt(..), other_kind) | (other_kind, Adt(..))
2999                             if is_primitive_or_pointer(other_kind) =>
3000                         {
3001                             let (primitive, adt) =
3002                                 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
3003                             if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
3004                                 ty == primitive
3005                             } else {
3006                                 compare_layouts(a, b).unwrap_or(false)
3007                             }
3008                         }
3009                         // Otherwise, just compare the layouts. This may fail to lint for some
3010                         // incompatible types, but at the very least, will stop reads into
3011                         // uninitialised memory.
3012                         _ => compare_layouts(a, b).unwrap_or(false),
3013                     }
3014                 })
3015             }
3016         }
3017         let mut seen_types = FxHashSet::default();
3018         structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
3019     }
3020 }
3021
3022 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
3023
3024 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
3025     fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
3026         trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
3027         if let ForeignItemKind::Fn(..) = this_fi.kind {
3028             let tcx = cx.tcx;
3029             if let Some(existing_hid) = self.insert(tcx, this_fi) {
3030                 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
3031                 let this_decl_ty = tcx.type_of(this_fi.owner_id);
3032                 debug!(
3033                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
3034                     existing_hid, existing_decl_ty, this_fi.owner_id, this_decl_ty
3035                 );
3036                 // Check that the declarations match.
3037                 if !Self::structurally_same_type(
3038                     cx,
3039                     existing_decl_ty,
3040                     this_decl_ty,
3041                     CItemKind::Declaration,
3042                 ) {
3043                     let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
3044                     let orig = Self::name_of_extern_decl(tcx, orig_fi);
3045
3046                     // We want to ensure that we use spans for both decls that include where the
3047                     // name was defined, whether that was from the link_name attribute or not.
3048                     let get_relevant_span =
3049                         |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
3050                             SymbolName::Normal(_) => fi.span,
3051                             SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
3052                         };
3053                     // Finally, emit the diagnostic.
3054
3055                     let msg = if orig.get_name() == this_fi.ident.name {
3056                         fluent::lint_builtin_clashing_extern_same_name
3057                     } else {
3058                         fluent::lint_builtin_clashing_extern_diff_name
3059                     };
3060                     tcx.struct_span_lint_hir(
3061                         CLASHING_EXTERN_DECLARATIONS,
3062                         this_fi.hir_id(),
3063                         get_relevant_span(this_fi),
3064                         msg,
3065                         |lint| {
3066                             let mut expected_str = DiagnosticStyledString::new();
3067                             expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
3068                             let mut found_str = DiagnosticStyledString::new();
3069                             found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3070
3071                             lint.set_arg("this_fi", this_fi.ident.name)
3072                                 .set_arg("orig", orig.get_name())
3073                                 .span_label(get_relevant_span(orig_fi), fluent::previous_decl_label)
3074                                 .span_label(get_relevant_span(this_fi), fluent::mismatch_label)
3075                                 // FIXME(davidtwco): translatable expected/found
3076                                 .note_expected_found(&"", expected_str, &"", found_str)
3077                         },
3078                     );
3079                 }
3080             }
3081         }
3082     }
3083 }
3084
3085 declare_lint! {
3086     /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3087     /// which causes [undefined behavior].
3088     ///
3089     /// ### Example
3090     ///
3091     /// ```rust,no_run
3092     /// # #![allow(unused)]
3093     /// use std::ptr;
3094     /// unsafe {
3095     ///     let x = &*ptr::null::<i32>();
3096     ///     let x = ptr::addr_of!(*ptr::null::<i32>());
3097     ///     let x = *(0 as *const i32);
3098     /// }
3099     /// ```
3100     ///
3101     /// {{produces}}
3102     ///
3103     /// ### Explanation
3104     ///
3105     /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3106     /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3107     ///
3108     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3109     pub DEREF_NULLPTR,
3110     Warn,
3111     "detects when an null pointer is dereferenced"
3112 }
3113
3114 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3115
3116 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
3117     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3118         /// test if expression is a null ptr
3119         fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3120             match &expr.kind {
3121                 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3122                     if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3123                         return is_zero(expr) || is_null_ptr(cx, expr);
3124                     }
3125                 }
3126                 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3127                 rustc_hir::ExprKind::Call(ref path, _) => {
3128                     if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3129                         if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3130                             return matches!(
3131                                 cx.tcx.get_diagnostic_name(def_id),
3132                                 Some(sym::ptr_null | sym::ptr_null_mut)
3133                             );
3134                         }
3135                     }
3136                 }
3137                 _ => {}
3138             }
3139             false
3140         }
3141
3142         /// test if expression is the literal `0`
3143         fn is_zero(expr: &hir::Expr<'_>) -> bool {
3144             match &expr.kind {
3145                 rustc_hir::ExprKind::Lit(ref lit) => {
3146                     if let LitKind::Int(a, _) = lit.node {
3147                         return a == 0;
3148                     }
3149                 }
3150                 _ => {}
3151             }
3152             false
3153         }
3154
3155         if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3156             if is_null_ptr(cx, expr_deref) {
3157                 cx.struct_span_lint(
3158                     DEREF_NULLPTR,
3159                     expr.span,
3160                     fluent::lint_builtin_deref_nullptr,
3161                     |lint| lint.span_label(expr.span, fluent::label),
3162                 );
3163             }
3164         }
3165     }
3166 }
3167
3168 declare_lint! {
3169     /// The `named_asm_labels` lint detects the use of named labels in the
3170     /// inline `asm!` macro.
3171     ///
3172     /// ### Example
3173     ///
3174     /// ```rust,compile_fail
3175     /// # #![feature(asm_experimental_arch)]
3176     /// use std::arch::asm;
3177     ///
3178     /// fn main() {
3179     ///     unsafe {
3180     ///         asm!("foo: bar");
3181     ///     }
3182     /// }
3183     /// ```
3184     ///
3185     /// {{produces}}
3186     ///
3187     /// ### Explanation
3188     ///
3189     /// LLVM is allowed to duplicate inline assembly blocks for any
3190     /// reason, for example when it is in a function that gets inlined. Because
3191     /// of this, GNU assembler [local labels] *must* be used instead of labels
3192     /// with a name. Using named labels might cause assembler or linker errors.
3193     ///
3194     /// See the explanation in [Rust By Example] for more details.
3195     ///
3196     /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3197     /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3198     pub NAMED_ASM_LABELS,
3199     Deny,
3200     "named labels in inline assembly",
3201 }
3202
3203 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3204
3205 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3206     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3207         if let hir::Expr {
3208             kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3209             ..
3210         } = expr
3211         {
3212             for (template_sym, template_snippet, template_span) in template_strs.iter() {
3213                 let template_str = template_sym.as_str();
3214                 let find_label_span = |needle: &str| -> Option<Span> {
3215                     if let Some(template_snippet) = template_snippet {
3216                         let snippet = template_snippet.as_str();
3217                         if let Some(pos) = snippet.find(needle) {
3218                             let end = pos
3219                                 + snippet[pos..]
3220                                     .find(|c| c == ':')
3221                                     .unwrap_or(snippet[pos..].len() - 1);
3222                             let inner = InnerSpan::new(pos, end);
3223                             return Some(template_span.from_inner(inner));
3224                         }
3225                     }
3226
3227                     None
3228                 };
3229
3230                 let mut found_labels = Vec::new();
3231
3232                 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3233                 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3234                 for statement in statements {
3235                     // If there's a comment, trim it from the statement
3236                     let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3237                     let mut start_idx = 0;
3238                     for (idx, _) in statement.match_indices(':') {
3239                         let possible_label = statement[start_idx..idx].trim();
3240                         let mut chars = possible_label.chars();
3241                         let Some(c) = chars.next() else {
3242                             // Empty string means a leading ':' in this section, which is not a label
3243                             break
3244                         };
3245                         // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3246                         if (c.is_alphabetic() || matches!(c, '.' | '_'))
3247                             && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3248                         {
3249                             found_labels.push(possible_label);
3250                         } else {
3251                             // If we encounter a non-label, there cannot be any further labels, so stop checking
3252                             break;
3253                         }
3254
3255                         start_idx = idx + 1;
3256                     }
3257                 }
3258
3259                 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3260
3261                 if found_labels.len() > 0 {
3262                     let spans = found_labels
3263                         .into_iter()
3264                         .filter_map(|label| find_label_span(label))
3265                         .collect::<Vec<Span>>();
3266                     // If there were labels but we couldn't find a span, combine the warnings and use the template span
3267                     let target_spans: MultiSpan =
3268                         if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3269
3270                     cx.lookup_with_diagnostics(
3271                             NAMED_ASM_LABELS,
3272                             Some(target_spans),
3273                             fluent::lint_builtin_asm_labels,
3274                             |lint| lint,
3275                             BuiltinLintDiagnostics::NamedAsmLabel(
3276                                 "only local labels of the form `<number>:` should be used in inline asm"
3277                                     .to_string(),
3278                             ),
3279                         );
3280                 }
3281             }
3282         }
3283     }
3284 }
3285
3286 declare_lint! {
3287     /// The `special_module_name` lint detects module
3288     /// declarations for files that have a special meaning.
3289     ///
3290     /// ### Example
3291     ///
3292     /// ```rust,compile_fail
3293     /// mod lib;
3294     ///
3295     /// fn main() {
3296     ///     lib::run();
3297     /// }
3298     /// ```
3299     ///
3300     /// {{produces}}
3301     ///
3302     /// ### Explanation
3303     ///
3304     /// Cargo recognizes `lib.rs` and `main.rs` as the root of a
3305     /// library or binary crate, so declaring them as modules
3306     /// will lead to miscompilation of the crate unless configured
3307     /// explicitly.
3308     ///
3309     /// To access a library from a binary target within the same crate,
3310     /// use `your_crate_name::` as the path instead of `lib::`:
3311     ///
3312     /// ```rust,compile_fail
3313     /// // bar/src/lib.rs
3314     /// fn run() {
3315     ///     // ...
3316     /// }
3317     ///
3318     /// // bar/src/main.rs
3319     /// fn main() {
3320     ///     bar::run();
3321     /// }
3322     /// ```
3323     ///
3324     /// Binary targets cannot be used as libraries and so declaring
3325     /// one as a module is not allowed.
3326     pub SPECIAL_MODULE_NAME,
3327     Warn,
3328     "module declarations for files with a special meaning",
3329 }
3330
3331 declare_lint_pass!(SpecialModuleName => [SPECIAL_MODULE_NAME]);
3332
3333 impl EarlyLintPass for SpecialModuleName {
3334     fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
3335         for item in &krate.items {
3336             if let ast::ItemKind::Mod(
3337                 _,
3338                 ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _),
3339             ) = item.kind
3340             {
3341                 if item.attrs.iter().any(|a| a.has_name(sym::path)) {
3342                     continue;
3343                 }
3344
3345                 match item.ident.name.as_str() {
3346                     "lib" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for lib.rs", |lint| {
3347                         lint
3348                             .note("lib.rs is the root of this crate's library target")
3349                             .help("to refer to it from other targets, use the library's name as the path")
3350                     }),
3351                     "main" => cx.struct_span_lint(SPECIAL_MODULE_NAME, item.span, "found module declaration for main.rs", |lint| {
3352                         lint
3353                             .note("a binary crate cannot be used as library")
3354                     }),
3355                     _ => continue
3356                 }
3357             }
3358         }
3359     }
3360 }
3361
3362 pub use rustc_session::lint::builtin::UNEXPECTED_CFGS;
3363
3364 declare_lint_pass!(UnexpectedCfgs => [UNEXPECTED_CFGS]);
3365
3366 impl EarlyLintPass for UnexpectedCfgs {
3367     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
3368         let cfg = &cx.sess().parse_sess.config;
3369         let check_cfg = &cx.sess().parse_sess.check_config;
3370         for &(name, value) in cfg {
3371             if let Some(names_valid) = &check_cfg.names_valid {
3372                 if !names_valid.contains(&name) {
3373                     cx.lookup(
3374                         UNEXPECTED_CFGS,
3375                         None::<MultiSpan>,
3376                         fluent::lint_builtin_unexpected_cli_config_name,
3377                         |diag| diag.help(fluent::help).set_arg("name", name),
3378                     );
3379                 }
3380             }
3381             if let Some(value) = value {
3382                 if let Some(values) = &check_cfg.values_valid.get(&name) {
3383                     if !values.contains(&value) {
3384                         cx.lookup(
3385                             UNEXPECTED_CFGS,
3386                             None::<MultiSpan>,
3387                             fluent::lint_builtin_unexpected_cli_config_value,
3388                             |diag| {
3389                                 diag.help(fluent::help)
3390                                     .set_arg("name", name)
3391                                     .set_arg("value", value)
3392                             },
3393                         );
3394                     }
3395                 }
3396             }
3397         }
3398     }
3399 }