rustc_lint/builtin.rs
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//!
10//! If you define a new [`EarlyLintPass`], you will also need to add it to the
11//! [`crate::early_lint_methods!`] invocation in `lib.rs`.
12//!
13//! If you define a new [`LateLintPass`], you will also need to add it to the
14//! [`crate::late_lint_methods!`] invocation in `lib.rs`.
15
16use std::fmt::Write;
17
18use ast::token::TokenKind;
19use rustc_abi::BackendRepr;
20use rustc_ast::tokenstream::{TokenStream, TokenTree};
21use rustc_ast::visit::{FnCtxt, FnKind};
22use rustc_ast::{self as ast, *};
23use rustc_ast_pretty::pprust::expr_to_string;
24use rustc_errors::{Applicability, LintDiagnostic};
25use rustc_feature::{AttributeGate, BuiltinAttribute, GateIssue, Stability, deprecated_attributes};
26use rustc_hir as hir;
27use rustc_hir::def::{DefKind, Res};
28use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
29use rustc_hir::intravisit::FnKind as HirFnKind;
30use rustc_hir::{Body, FnDecl, GenericParamKind, PatKind, PredicateOrigin};
31use rustc_middle::bug;
32use rustc_middle::lint::LevelAndSource;
33use rustc_middle::ty::layout::LayoutOf;
34use rustc_middle::ty::print::with_no_trimmed_paths;
35use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt, Upcast, VariantDef};
36use rustc_session::lint::FutureIncompatibilityReason;
37// hardwired lints from rustc_lint_defs
38pub use rustc_session::lint::builtin::*;
39use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
40use rustc_span::edition::Edition;
41use rustc_span::source_map::Spanned;
42use rustc_span::{BytePos, Ident, InnerSpan, Span, Symbol, kw, sym};
43use rustc_target::asm::InlineAsmArch;
44use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
45use rustc_trait_selection::traits::misc::type_allowed_to_implement_copy;
46use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
47use rustc_trait_selection::traits::{self};
48
49use crate::errors::BuiltinEllipsisInclusiveRangePatterns;
50use crate::lints::{
51 BuiltinAnonymousParams, BuiltinConstNoMangle, BuiltinDeprecatedAttrLink,
52 BuiltinDeprecatedAttrLinkSuggestion, BuiltinDerefNullptr, BuiltinDoubleNegations,
53 BuiltinDoubleNegationsAddParens, BuiltinEllipsisInclusiveRangePatternsLint,
54 BuiltinExplicitOutlives, BuiltinExplicitOutlivesSuggestion, BuiltinFeatureIssueNote,
55 BuiltinIncompleteFeatures, BuiltinIncompleteFeaturesHelp, BuiltinInternalFeatures,
56 BuiltinKeywordIdents, BuiltinMissingCopyImpl, BuiltinMissingDebugImpl, BuiltinMissingDoc,
57 BuiltinMutablesTransmutes, BuiltinNoMangleGeneric, BuiltinNonShorthandFieldPatterns,
58 BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasBounds,
59 BuiltinUngatedAsyncFnTrackCaller, BuiltinUnpermittedTypeInit, BuiltinUnpermittedTypeInitSub,
60 BuiltinUnreachablePub, BuiltinUnsafe, BuiltinUnstableFeatures, BuiltinUnusedDocComment,
61 BuiltinUnusedDocCommentSub, BuiltinWhileTrue, InvalidAsmLabel,
62};
63use crate::nonstandard_style::{MethodLateContext, method_context};
64use crate::{
65 EarlyContext, EarlyLintPass, LateContext, LateLintPass, Level, LintContext,
66 fluent_generated as fluent,
67};
68declare_lint! {
69 /// The `while_true` lint detects `while true { }`.
70 ///
71 /// ### Example
72 ///
73 /// ```rust,no_run
74 /// while true {
75 ///
76 /// }
77 /// ```
78 ///
79 /// {{produces}}
80 ///
81 /// ### Explanation
82 ///
83 /// `while true` should be replaced with `loop`. A `loop` expression is
84 /// the preferred way to write an infinite loop because it more directly
85 /// expresses the intent of the loop.
86 WHILE_TRUE,
87 Warn,
88 "suggest using `loop { }` instead of `while true { }`"
89}
90
91declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
92
93impl EarlyLintPass for WhileTrue {
94 #[inline]
95 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
96 if let ast::ExprKind::While(cond, _, label) = &e.kind
97 && let ast::ExprKind::Lit(token_lit) = cond.peel_parens().kind
98 && let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
99 && !cond.span.from_expansion()
100 {
101 let condition_span = e.span.with_hi(cond.span.hi());
102 let replace = format!(
103 "{}loop",
104 label.map_or_else(String::new, |label| format!("{}: ", label.ident,))
105 );
106 cx.emit_span_lint(
107 WHILE_TRUE,
108 condition_span,
109 BuiltinWhileTrue { suggestion: condition_span, replace },
110 );
111 }
112 }
113}
114
115declare_lint! {
116 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
117 /// instead of `Struct { x }` in a pattern.
118 ///
119 /// ### Example
120 ///
121 /// ```rust
122 /// struct Point {
123 /// x: i32,
124 /// y: i32,
125 /// }
126 ///
127 ///
128 /// fn main() {
129 /// let p = Point {
130 /// x: 5,
131 /// y: 5,
132 /// };
133 ///
134 /// match p {
135 /// Point { x: x, y: y } => (),
136 /// }
137 /// }
138 /// ```
139 ///
140 /// {{produces}}
141 ///
142 /// ### Explanation
143 ///
144 /// The preferred style is to avoid the repetition of specifying both the
145 /// field name and the binding name if both identifiers are the same.
146 NON_SHORTHAND_FIELD_PATTERNS,
147 Warn,
148 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
149}
150
151declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
152
153impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
154 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
155 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
156 let variant = cx
157 .typeck_results()
158 .pat_ty(pat)
159 .ty_adt_def()
160 .expect("struct pattern type is not an ADT")
161 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
162 for fieldpat in field_pats {
163 if fieldpat.is_shorthand {
164 continue;
165 }
166 if fieldpat.span.from_expansion() {
167 // Don't lint if this is a macro expansion: macro authors
168 // shouldn't have to worry about this kind of style issue
169 // (Issue #49588)
170 continue;
171 }
172 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
173 if cx.tcx.find_field_index(ident, variant)
174 == Some(cx.typeck_results().field_index(fieldpat.hir_id))
175 {
176 cx.emit_span_lint(
177 NON_SHORTHAND_FIELD_PATTERNS,
178 fieldpat.span,
179 BuiltinNonShorthandFieldPatterns {
180 ident,
181 suggestion: fieldpat.span,
182 prefix: binding_annot.prefix_str(),
183 },
184 );
185 }
186 }
187 }
188 }
189 }
190}
191
192declare_lint! {
193 /// The `unsafe_code` lint catches usage of `unsafe` code and other
194 /// potentially unsound constructs like `no_mangle`, `export_name`,
195 /// and `link_section`.
196 ///
197 /// ### Example
198 ///
199 /// ```rust,compile_fail
200 /// #![deny(unsafe_code)]
201 /// fn main() {
202 /// unsafe {
203 ///
204 /// }
205 /// }
206 ///
207 /// #[no_mangle]
208 /// fn func_0() { }
209 ///
210 /// #[export_name = "exported_symbol_name"]
211 /// pub fn name_in_rust() { }
212 ///
213 /// #[no_mangle]
214 /// #[link_section = ".example_section"]
215 /// pub static VAR1: u32 = 1;
216 /// ```
217 ///
218 /// {{produces}}
219 ///
220 /// ### Explanation
221 ///
222 /// This lint is intended to restrict the usage of `unsafe` blocks and other
223 /// constructs (including, but not limited to `no_mangle`, `link_section`
224 /// and `export_name` attributes) wrong usage of which causes undefined
225 /// behavior.
226 UNSAFE_CODE,
227 Allow,
228 "usage of `unsafe` code and other potentially unsound constructs",
229 @eval_always = true
230}
231
232declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
233
234impl UnsafeCode {
235 fn report_unsafe(
236 &self,
237 cx: &EarlyContext<'_>,
238 span: Span,
239 decorate: impl for<'a> LintDiagnostic<'a, ()>,
240 ) {
241 // This comes from a macro that has `#[allow_internal_unsafe]`.
242 if span.allows_unsafe() {
243 return;
244 }
245
246 cx.emit_span_lint(UNSAFE_CODE, span, decorate);
247 }
248}
249
250impl EarlyLintPass for UnsafeCode {
251 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
252 if attr.has_name(sym::allow_internal_unsafe) {
253 self.report_unsafe(cx, attr.span, BuiltinUnsafe::AllowInternalUnsafe);
254 }
255 }
256
257 #[inline]
258 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
259 if let ast::ExprKind::Block(ref blk, _) = e.kind {
260 // Don't warn about generated blocks; that'll just pollute the output.
261 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
262 self.report_unsafe(cx, blk.span, BuiltinUnsafe::UnsafeBlock);
263 }
264 }
265 }
266
267 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
268 match it.kind {
269 ast::ItemKind::Trait(box ast::Trait { safety: ast::Safety::Unsafe(_), .. }) => {
270 self.report_unsafe(cx, it.span, BuiltinUnsafe::UnsafeTrait);
271 }
272
273 ast::ItemKind::Impl(box ast::Impl { safety: ast::Safety::Unsafe(_), .. }) => {
274 self.report_unsafe(cx, it.span, BuiltinUnsafe::UnsafeImpl);
275 }
276
277 ast::ItemKind::Fn(..) => {
278 if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
279 self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleFn);
280 }
281
282 if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
283 self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameFn);
284 }
285
286 if let Some(attr) = attr::find_by_name(&it.attrs, sym::link_section) {
287 self.report_unsafe(cx, attr.span, BuiltinUnsafe::LinkSectionFn);
288 }
289 }
290
291 ast::ItemKind::Static(..) => {
292 if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
293 self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleStatic);
294 }
295
296 if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
297 self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameStatic);
298 }
299
300 if let Some(attr) = attr::find_by_name(&it.attrs, sym::link_section) {
301 self.report_unsafe(cx, attr.span, BuiltinUnsafe::LinkSectionStatic);
302 }
303 }
304
305 ast::ItemKind::GlobalAsm(..) => {
306 self.report_unsafe(cx, it.span, BuiltinUnsafe::GlobalAsm);
307 }
308
309 ast::ItemKind::ForeignMod(ForeignMod { safety, .. }) => {
310 if let Safety::Unsafe(_) = safety {
311 self.report_unsafe(cx, it.span, BuiltinUnsafe::UnsafeExternBlock);
312 }
313 }
314
315 _ => {}
316 }
317 }
318
319 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
320 if let ast::AssocItemKind::Fn(..) = it.kind {
321 if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
322 self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleMethod);
323 }
324 if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
325 self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameMethod);
326 }
327 }
328 }
329
330 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
331 if let FnKind::Fn(
332 ctxt,
333 _,
334 ast::Fn {
335 sig: ast::FnSig { header: ast::FnHeader { safety: ast::Safety::Unsafe(_), .. }, .. },
336 body,
337 ..
338 },
339 ) = fk
340 {
341 let decorator = match ctxt {
342 FnCtxt::Foreign => return,
343 FnCtxt::Free => BuiltinUnsafe::DeclUnsafeFn,
344 FnCtxt::Assoc(_) if body.is_none() => BuiltinUnsafe::DeclUnsafeMethod,
345 FnCtxt::Assoc(_) => BuiltinUnsafe::ImplUnsafeMethod,
346 };
347 self.report_unsafe(cx, span, decorator);
348 }
349 }
350}
351
352declare_lint! {
353 /// The `missing_docs` lint detects missing documentation for public items.
354 ///
355 /// ### Example
356 ///
357 /// ```rust,compile_fail
358 /// #![deny(missing_docs)]
359 /// pub fn foo() {}
360 /// ```
361 ///
362 /// {{produces}}
363 ///
364 /// ### Explanation
365 ///
366 /// This lint is intended to ensure that a library is well-documented.
367 /// Items without documentation can be difficult for users to understand
368 /// how to use properly.
369 ///
370 /// This lint is "allow" by default because it can be noisy, and not all
371 /// projects may want to enforce everything to be documented.
372 pub MISSING_DOCS,
373 Allow,
374 "detects missing documentation for public members",
375 report_in_external_macro
376}
377
378#[derive(Default)]
379pub struct MissingDoc;
380
381impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
382
383fn has_doc(attr: &hir::Attribute) -> bool {
384 if attr.is_doc_comment() {
385 return true;
386 }
387
388 if !attr.has_name(sym::doc) {
389 return false;
390 }
391
392 if attr.value_str().is_some() {
393 return true;
394 }
395
396 if let Some(list) = attr.meta_item_list() {
397 for meta in list {
398 if meta.has_name(sym::hidden) {
399 return true;
400 }
401 }
402 }
403
404 false
405}
406
407impl MissingDoc {
408 fn check_missing_docs_attrs(
409 &self,
410 cx: &LateContext<'_>,
411 def_id: LocalDefId,
412 article: &'static str,
413 desc: &'static str,
414 ) {
415 // Only check publicly-visible items, using the result from the privacy pass.
416 // It's an option so the crate root can also use this function (it doesn't
417 // have a `NodeId`).
418 if def_id != CRATE_DEF_ID && !cx.effective_visibilities.is_exported(def_id) {
419 return;
420 }
421
422 let attrs = cx.tcx.hir_attrs(cx.tcx.local_def_id_to_hir_id(def_id));
423 let has_doc = attrs.iter().any(has_doc);
424 if !has_doc {
425 cx.emit_span_lint(
426 MISSING_DOCS,
427 cx.tcx.def_span(def_id),
428 BuiltinMissingDoc { article, desc },
429 );
430 }
431 }
432}
433
434impl<'tcx> LateLintPass<'tcx> for MissingDoc {
435 fn check_crate(&mut self, cx: &LateContext<'_>) {
436 self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
437 }
438
439 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
440 // Previously the Impl and Use types have been excluded from missing docs,
441 // so we will continue to exclude them for compatibility.
442 //
443 // The documentation on `ExternCrate` is not used at the moment so no need to warn for it.
444 if let hir::ItemKind::Impl(..) | hir::ItemKind::Use(..) | hir::ItemKind::ExternCrate(..) =
445 it.kind
446 {
447 return;
448 }
449
450 let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
451 self.check_missing_docs_attrs(cx, it.owner_id.def_id, article, desc);
452 }
453
454 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
455 let (article, desc) = cx.tcx.article_and_description(trait_item.owner_id.to_def_id());
456
457 self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, article, desc);
458 }
459
460 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
461 let context = method_context(cx, impl_item.owner_id.def_id);
462
463 match context {
464 // If the method is an impl for a trait, don't doc.
465 MethodLateContext::TraitImpl => return,
466 MethodLateContext::TraitAutoImpl => {}
467 // If the method is an impl for an item with docs_hidden, don't doc.
468 MethodLateContext::PlainImpl => {
469 let parent = cx.tcx.hir_get_parent_item(impl_item.hir_id());
470 let impl_ty = cx.tcx.type_of(parent).instantiate_identity();
471 let outerdef = match impl_ty.kind() {
472 ty::Adt(def, _) => Some(def.did()),
473 ty::Foreign(def_id) => Some(*def_id),
474 _ => None,
475 };
476 let is_hidden = match outerdef {
477 Some(id) => cx.tcx.is_doc_hidden(id),
478 None => false,
479 };
480 if is_hidden {
481 return;
482 }
483 }
484 }
485
486 let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
487 self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);
488 }
489
490 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
491 let (article, desc) = cx.tcx.article_and_description(foreign_item.owner_id.to_def_id());
492 self.check_missing_docs_attrs(cx, foreign_item.owner_id.def_id, article, desc);
493 }
494
495 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
496 if !sf.is_positional() {
497 self.check_missing_docs_attrs(cx, sf.def_id, "a", "struct field")
498 }
499 }
500
501 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
502 self.check_missing_docs_attrs(cx, v.def_id, "a", "variant");
503 }
504}
505
506declare_lint! {
507 /// The `missing_copy_implementations` lint detects potentially-forgotten
508 /// implementations of [`Copy`] for public types.
509 ///
510 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
511 ///
512 /// ### Example
513 ///
514 /// ```rust,compile_fail
515 /// #![deny(missing_copy_implementations)]
516 /// pub struct Foo {
517 /// pub field: i32
518 /// }
519 /// # fn main() {}
520 /// ```
521 ///
522 /// {{produces}}
523 ///
524 /// ### Explanation
525 ///
526 /// Historically (before 1.0), types were automatically marked as `Copy`
527 /// if possible. This was changed so that it required an explicit opt-in
528 /// by implementing the `Copy` trait. As part of this change, a lint was
529 /// added to alert if a copyable type was not marked `Copy`.
530 ///
531 /// This lint is "allow" by default because this code isn't bad; it is
532 /// common to write newtypes like this specifically so that a `Copy` type
533 /// is no longer `Copy`. `Copy` types can result in unintended copies of
534 /// large data which can impact performance.
535 pub MISSING_COPY_IMPLEMENTATIONS,
536 Allow,
537 "detects potentially-forgotten implementations of `Copy`"
538}
539
540declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
541
542impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
543 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
544 if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
545 return;
546 }
547 let (def, ty) = match item.kind {
548 hir::ItemKind::Struct(_, generics, _) => {
549 if !generics.params.is_empty() {
550 return;
551 }
552 let def = cx.tcx.adt_def(item.owner_id);
553 (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
554 }
555 hir::ItemKind::Union(_, generics, _) => {
556 if !generics.params.is_empty() {
557 return;
558 }
559 let def = cx.tcx.adt_def(item.owner_id);
560 (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
561 }
562 hir::ItemKind::Enum(_, generics, _) => {
563 if !generics.params.is_empty() {
564 return;
565 }
566 let def = cx.tcx.adt_def(item.owner_id);
567 (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
568 }
569 _ => return,
570 };
571 if def.has_dtor(cx.tcx) {
572 return;
573 }
574
575 // If the type contains a raw pointer, it may represent something like a handle,
576 // and recommending Copy might be a bad idea.
577 for field in def.all_fields() {
578 let did = field.did;
579 if cx.tcx.type_of(did).instantiate_identity().is_raw_ptr() {
580 return;
581 }
582 }
583 if cx.type_is_copy_modulo_regions(ty) {
584 return;
585 }
586 if type_implements_negative_copy_modulo_regions(cx.tcx, ty, cx.typing_env()) {
587 return;
588 }
589 if def.is_variant_list_non_exhaustive()
590 || def.variants().iter().any(|variant| variant.is_field_list_non_exhaustive())
591 {
592 return;
593 }
594
595 // We shouldn't recommend implementing `Copy` on stateful things,
596 // such as iterators.
597 if let Some(iter_trait) = cx.tcx.get_diagnostic_item(sym::Iterator)
598 && cx
599 .tcx
600 .infer_ctxt()
601 .build(cx.typing_mode())
602 .type_implements_trait(iter_trait, [ty], cx.param_env)
603 .must_apply_modulo_regions()
604 {
605 return;
606 }
607
608 // Default value of clippy::trivially_copy_pass_by_ref
609 const MAX_SIZE: u64 = 256;
610
611 if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes()) {
612 if size > MAX_SIZE {
613 return;
614 }
615 }
616
617 if type_allowed_to_implement_copy(
618 cx.tcx,
619 cx.param_env,
620 ty,
621 traits::ObligationCause::misc(item.span, item.owner_id.def_id),
622 hir::Safety::Safe,
623 )
624 .is_ok()
625 {
626 cx.emit_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, BuiltinMissingCopyImpl);
627 }
628 }
629}
630
631/// Check whether a `ty` has a negative `Copy` implementation, ignoring outlives constraints.
632fn type_implements_negative_copy_modulo_regions<'tcx>(
633 tcx: TyCtxt<'tcx>,
634 ty: Ty<'tcx>,
635 typing_env: ty::TypingEnv<'tcx>,
636) -> bool {
637 let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
638 let trait_ref = ty::TraitRef::new(tcx, tcx.require_lang_item(hir::LangItem::Copy, None), [ty]);
639 let pred = ty::TraitPredicate { trait_ref, polarity: ty::PredicatePolarity::Negative };
640 let obligation = traits::Obligation {
641 cause: traits::ObligationCause::dummy(),
642 param_env,
643 recursion_depth: 0,
644 predicate: pred.upcast(tcx),
645 };
646 infcx.predicate_must_hold_modulo_regions(&obligation)
647}
648
649declare_lint! {
650 /// The `missing_debug_implementations` lint detects missing
651 /// implementations of [`fmt::Debug`] for public types.
652 ///
653 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
654 ///
655 /// ### Example
656 ///
657 /// ```rust,compile_fail
658 /// #![deny(missing_debug_implementations)]
659 /// pub struct Foo;
660 /// # fn main() {}
661 /// ```
662 ///
663 /// {{produces}}
664 ///
665 /// ### Explanation
666 ///
667 /// Having a `Debug` implementation on all types can assist with
668 /// debugging, as it provides a convenient way to format and display a
669 /// value. Using the `#[derive(Debug)]` attribute will automatically
670 /// generate a typical implementation, or a custom implementation can be
671 /// added by manually implementing the `Debug` trait.
672 ///
673 /// This lint is "allow" by default because adding `Debug` to all types can
674 /// have a negative impact on compile time and code size. It also requires
675 /// boilerplate to be added to every type, which can be an impediment.
676 MISSING_DEBUG_IMPLEMENTATIONS,
677 Allow,
678 "detects missing implementations of Debug"
679}
680
681#[derive(Default)]
682pub(crate) struct MissingDebugImplementations;
683
684impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
685
686impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
687 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
688 if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
689 return;
690 }
691
692 match item.kind {
693 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
694 _ => return,
695 }
696
697 // Avoid listing trait impls if the trait is allowed.
698 let LevelAndSource { level, .. } =
699 cx.tcx.lint_level_at_node(MISSING_DEBUG_IMPLEMENTATIONS, item.hir_id());
700 if level == Level::Allow {
701 return;
702 }
703
704 let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else { return };
705
706 let has_impl = cx
707 .tcx
708 .non_blanket_impls_for_ty(debug, cx.tcx.type_of(item.owner_id).instantiate_identity())
709 .next()
710 .is_some();
711 if !has_impl {
712 cx.emit_span_lint(
713 MISSING_DEBUG_IMPLEMENTATIONS,
714 item.span,
715 BuiltinMissingDebugImpl { tcx: cx.tcx, def_id: debug },
716 );
717 }
718 }
719}
720
721declare_lint! {
722 /// The `anonymous_parameters` lint detects anonymous parameters in trait
723 /// definitions.
724 ///
725 /// ### Example
726 ///
727 /// ```rust,edition2015,compile_fail
728 /// #![deny(anonymous_parameters)]
729 /// // edition 2015
730 /// pub trait Foo {
731 /// fn foo(usize);
732 /// }
733 /// fn main() {}
734 /// ```
735 ///
736 /// {{produces}}
737 ///
738 /// ### Explanation
739 ///
740 /// This syntax is mostly a historical accident, and can be worked around
741 /// quite easily by adding an `_` pattern or a descriptive identifier:
742 ///
743 /// ```rust
744 /// trait Foo {
745 /// fn foo(_: usize);
746 /// }
747 /// ```
748 ///
749 /// This syntax is now a hard error in the 2018 edition. In the 2015
750 /// edition, this lint is "warn" by default. This lint
751 /// enables the [`cargo fix`] tool with the `--edition` flag to
752 /// automatically transition old code from the 2015 edition to 2018. The
753 /// tool will run this lint and automatically apply the
754 /// suggested fix from the compiler (which is to add `_` to each
755 /// parameter). This provides a completely automated way to update old
756 /// code for a new edition. See [issue #41686] for more details.
757 ///
758 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
759 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
760 pub ANONYMOUS_PARAMETERS,
761 Warn,
762 "detects anonymous parameters",
763 @future_incompatible = FutureIncompatibleInfo {
764 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
765 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
766 };
767}
768
769declare_lint_pass!(
770 /// Checks for use of anonymous parameters (RFC 1685).
771 AnonymousParameters => [ANONYMOUS_PARAMETERS]
772);
773
774impl EarlyLintPass for AnonymousParameters {
775 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
776 if cx.sess().edition() != Edition::Edition2015 {
777 // This is a hard error in future editions; avoid linting and erroring
778 return;
779 }
780 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
781 for arg in sig.decl.inputs.iter() {
782 if let ast::PatKind::Missing = arg.pat.kind {
783 let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
784
785 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
786 (snip.as_str(), Applicability::MachineApplicable)
787 } else {
788 ("<type>", Applicability::HasPlaceholders)
789 };
790 cx.emit_span_lint(
791 ANONYMOUS_PARAMETERS,
792 arg.pat.span,
793 BuiltinAnonymousParams { suggestion: (arg.pat.span, appl), ty_snip },
794 );
795 }
796 }
797 }
798 }
799}
800
801/// Check for use of attributes which have been deprecated.
802#[derive(Clone)]
803pub struct DeprecatedAttr {
804 // This is not free to compute, so we want to keep it around, rather than
805 // compute it for every attribute.
806 depr_attrs: Vec<&'static BuiltinAttribute>,
807}
808
809impl_lint_pass!(DeprecatedAttr => []);
810
811impl Default for DeprecatedAttr {
812 fn default() -> Self {
813 DeprecatedAttr { depr_attrs: deprecated_attributes() }
814 }
815}
816
817impl EarlyLintPass for DeprecatedAttr {
818 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
819 for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
820 if attr.ident().map(|ident| ident.name) == Some(*name) {
821 if let &AttributeGate::Gated(
822 Stability::Deprecated(link, suggestion),
823 name,
824 reason,
825 _,
826 ) = gate
827 {
828 let suggestion = match suggestion {
829 Some(msg) => {
830 BuiltinDeprecatedAttrLinkSuggestion::Msg { suggestion: attr.span, msg }
831 }
832 None => {
833 BuiltinDeprecatedAttrLinkSuggestion::Default { suggestion: attr.span }
834 }
835 };
836 cx.emit_span_lint(
837 DEPRECATED,
838 attr.span,
839 BuiltinDeprecatedAttrLink { name, reason, link, suggestion },
840 );
841 }
842 return;
843 }
844 }
845 }
846}
847
848fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
849 use rustc_ast::token::CommentKind;
850
851 let mut attrs = attrs.iter().peekable();
852
853 // Accumulate a single span for sugared doc comments.
854 let mut sugared_span: Option<Span> = None;
855
856 while let Some(attr) = attrs.next() {
857 let is_doc_comment = attr.is_doc_comment();
858 if is_doc_comment {
859 sugared_span =
860 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
861 }
862
863 if attrs.peek().is_some_and(|next_attr| next_attr.is_doc_comment()) {
864 continue;
865 }
866
867 let span = sugared_span.take().unwrap_or(attr.span);
868
869 if is_doc_comment || attr.has_name(sym::doc) {
870 let sub = match attr.kind {
871 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
872 BuiltinUnusedDocCommentSub::PlainHelp
873 }
874 AttrKind::DocComment(CommentKind::Block, _) => {
875 BuiltinUnusedDocCommentSub::BlockHelp
876 }
877 };
878 cx.emit_span_lint(
879 UNUSED_DOC_COMMENTS,
880 span,
881 BuiltinUnusedDocComment { kind: node_kind, label: node_span, sub },
882 );
883 }
884 }
885}
886
887impl EarlyLintPass for UnusedDocComment {
888 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
889 let kind = match stmt.kind {
890 ast::StmtKind::Let(..) => "statements",
891 // Disabled pending discussion in #78306
892 ast::StmtKind::Item(..) => return,
893 // expressions will be reported by `check_expr`.
894 ast::StmtKind::Empty
895 | ast::StmtKind::Semi(_)
896 | ast::StmtKind::Expr(_)
897 | ast::StmtKind::MacCall(_) => return,
898 };
899
900 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
901 }
902
903 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
904 if let Some(body) = &arm.body {
905 let arm_span = arm.pat.span.with_hi(body.span.hi());
906 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
907 }
908 }
909
910 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
911 if let ast::PatKind::Struct(_, _, fields, _) = &pat.kind {
912 for field in fields {
913 warn_if_doc(cx, field.span, "pattern fields", &field.attrs);
914 }
915 }
916 }
917
918 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
919 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
920
921 if let ExprKind::Struct(s) = &expr.kind {
922 for field in &s.fields {
923 warn_if_doc(cx, field.span, "expression fields", &field.attrs);
924 }
925 }
926 }
927
928 fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
929 warn_if_doc(cx, param.ident.span, "generic parameters", ¶m.attrs);
930 }
931
932 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
933 warn_if_doc(cx, block.span, "blocks", block.attrs());
934 }
935
936 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
937 if let ast::ItemKind::ForeignMod(_) = item.kind {
938 warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
939 }
940 }
941}
942
943declare_lint! {
944 /// The `no_mangle_const_items` lint detects any `const` items with the
945 /// [`no_mangle` attribute].
946 ///
947 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
948 ///
949 /// ### Example
950 ///
951 /// ```rust,compile_fail,edition2021
952 /// #[no_mangle]
953 /// const FOO: i32 = 5;
954 /// ```
955 ///
956 /// {{produces}}
957 ///
958 /// ### Explanation
959 ///
960 /// Constants do not have their symbols exported, and therefore, this
961 /// probably means you meant to use a [`static`], not a [`const`].
962 ///
963 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
964 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
965 NO_MANGLE_CONST_ITEMS,
966 Deny,
967 "const items will not have their symbols exported"
968}
969
970declare_lint! {
971 /// The `no_mangle_generic_items` lint detects generic items that must be
972 /// mangled.
973 ///
974 /// ### Example
975 ///
976 /// ```rust
977 /// #[unsafe(no_mangle)]
978 /// fn foo<T>(t: T) {}
979 ///
980 /// #[unsafe(export_name = "bar")]
981 /// fn bar<T>(t: T) {}
982 /// ```
983 ///
984 /// {{produces}}
985 ///
986 /// ### Explanation
987 ///
988 /// A function with generics must have its symbol mangled to accommodate
989 /// the generic parameter. The [`no_mangle`] and [`export_name`] attributes
990 /// have no effect in this situation, and should be removed.
991 ///
992 /// [`no_mangle`]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
993 /// [`export_name`]: https://doc.rust-lang.org/reference/abi.html#the-export_name-attribute
994 NO_MANGLE_GENERIC_ITEMS,
995 Warn,
996 "generic items must be mangled"
997}
998
999declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1000
1001impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
1002 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1003 let attrs = cx.tcx.hir_attrs(it.hir_id());
1004 let check_no_mangle_on_generic_fn = |attr: &hir::Attribute,
1005 impl_generics: Option<&hir::Generics<'_>>,
1006 generics: &hir::Generics<'_>,
1007 span| {
1008 for param in
1009 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1010 {
1011 match param.kind {
1012 GenericParamKind::Lifetime { .. } => {}
1013 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1014 cx.emit_span_lint(
1015 NO_MANGLE_GENERIC_ITEMS,
1016 span,
1017 BuiltinNoMangleGeneric { suggestion: attr.span() },
1018 );
1019 break;
1020 }
1021 }
1022 }
1023 };
1024 match it.kind {
1025 hir::ItemKind::Fn { generics, .. } => {
1026 if let Some(attr) = attr::find_by_name(attrs, sym::export_name)
1027 .or_else(|| attr::find_by_name(attrs, sym::no_mangle))
1028 {
1029 check_no_mangle_on_generic_fn(attr, None, generics, it.span);
1030 }
1031 }
1032 hir::ItemKind::Const(..) => {
1033 if attr::contains_name(attrs, sym::no_mangle) {
1034 // account for "pub const" (#45562)
1035 let start = cx
1036 .tcx
1037 .sess
1038 .source_map()
1039 .span_to_snippet(it.span)
1040 .map(|snippet| snippet.find("const").unwrap_or(0))
1041 .unwrap_or(0) as u32;
1042 // `const` is 5 chars
1043 let suggestion = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1044
1045 // Const items do not refer to a particular location in memory, and therefore
1046 // don't have anything to attach a symbol to
1047 cx.emit_span_lint(
1048 NO_MANGLE_CONST_ITEMS,
1049 it.span,
1050 BuiltinConstNoMangle { suggestion },
1051 );
1052 }
1053 }
1054 hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1055 for it in *items {
1056 if let hir::AssocItemKind::Fn { .. } = it.kind {
1057 let attrs = cx.tcx.hir_attrs(it.id.hir_id());
1058 if let Some(attr) = attr::find_by_name(attrs, sym::export_name)
1059 .or_else(|| attr::find_by_name(attrs, sym::no_mangle))
1060 {
1061 check_no_mangle_on_generic_fn(
1062 attr,
1063 Some(generics),
1064 cx.tcx.hir_get_generics(it.id.owner_id.def_id).unwrap(),
1065 it.span,
1066 );
1067 }
1068 }
1069 }
1070 }
1071 _ => {}
1072 }
1073 }
1074}
1075
1076declare_lint! {
1077 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1078 /// T` because it is [undefined behavior].
1079 ///
1080 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1081 ///
1082 /// ### Example
1083 ///
1084 /// ```rust,compile_fail
1085 /// unsafe {
1086 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1087 /// }
1088 /// ```
1089 ///
1090 /// {{produces}}
1091 ///
1092 /// ### Explanation
1093 ///
1094 /// Certain assumptions are made about aliasing of data, and this transmute
1095 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1096 ///
1097 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1098 MUTABLE_TRANSMUTES,
1099 Deny,
1100 "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1101}
1102
1103declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1104
1105impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
1106 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1107 if let Some((&ty::Ref(_, _, from_mutbl), &ty::Ref(_, _, to_mutbl))) =
1108 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1109 {
1110 if from_mutbl < to_mutbl {
1111 cx.emit_span_lint(MUTABLE_TRANSMUTES, expr.span, BuiltinMutablesTransmutes);
1112 }
1113 }
1114
1115 fn get_transmute_from_to<'tcx>(
1116 cx: &LateContext<'tcx>,
1117 expr: &hir::Expr<'_>,
1118 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1119 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1120 cx.qpath_res(qpath, expr.hir_id)
1121 } else {
1122 return None;
1123 };
1124 if let Res::Def(DefKind::Fn, did) = def {
1125 if !def_id_is_transmute(cx, did) {
1126 return None;
1127 }
1128 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1129 let from = sig.inputs().skip_binder()[0];
1130 let to = sig.output().skip_binder();
1131 return Some((from, to));
1132 }
1133 None
1134 }
1135
1136 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1137 cx.tcx.is_intrinsic(def_id, sym::transmute)
1138 }
1139 }
1140}
1141
1142declare_lint! {
1143 /// The `unstable_features` lint detects uses of `#![feature]`.
1144 ///
1145 /// ### Example
1146 ///
1147 /// ```rust,compile_fail
1148 /// #![deny(unstable_features)]
1149 /// #![feature(test)]
1150 /// ```
1151 ///
1152 /// {{produces}}
1153 ///
1154 /// ### Explanation
1155 ///
1156 /// In larger nightly-based projects which
1157 ///
1158 /// * consist of a multitude of crates where a subset of crates has to compile on
1159 /// stable either unconditionally or depending on a `cfg` flag to for example
1160 /// allow stable users to depend on them,
1161 /// * don't use nightly for experimental features but for, e.g., unstable options only,
1162 ///
1163 /// this lint may come in handy to enforce policies of these kinds.
1164 UNSTABLE_FEATURES,
1165 Allow,
1166 "enabling unstable features"
1167}
1168
1169declare_lint_pass!(
1170 /// Forbids using the `#[feature(...)]` attribute
1171 UnstableFeatures => [UNSTABLE_FEATURES]
1172);
1173
1174impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
1175 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &hir::Attribute) {
1176 if attr.has_name(sym::feature)
1177 && let Some(items) = attr.meta_item_list()
1178 {
1179 for item in items {
1180 cx.emit_span_lint(UNSTABLE_FEATURES, item.span(), BuiltinUnstableFeatures);
1181 }
1182 }
1183 }
1184}
1185
1186declare_lint! {
1187 /// The `ungated_async_fn_track_caller` lint warns when the
1188 /// `#[track_caller]` attribute is used on an async function
1189 /// without enabling the corresponding unstable feature flag.
1190 ///
1191 /// ### Example
1192 ///
1193 /// ```rust
1194 /// #[track_caller]
1195 /// async fn foo() {}
1196 /// ```
1197 ///
1198 /// {{produces}}
1199 ///
1200 /// ### Explanation
1201 ///
1202 /// The attribute must be used in conjunction with the
1203 /// [`async_fn_track_caller` feature flag]. Otherwise, the `#[track_caller]`
1204 /// annotation will function as a no-op.
1205 ///
1206 /// [`async_fn_track_caller` feature flag]: https://doc.rust-lang.org/beta/unstable-book/language-features/async-fn-track-caller.html
1207 UNGATED_ASYNC_FN_TRACK_CALLER,
1208 Warn,
1209 "enabling track_caller on an async fn is a no-op unless the async_fn_track_caller feature is enabled"
1210}
1211
1212declare_lint_pass!(
1213 /// Explains corresponding feature flag must be enabled for the `#[track_caller]` attribute to
1214 /// do anything
1215 UngatedAsyncFnTrackCaller => [UNGATED_ASYNC_FN_TRACK_CALLER]
1216);
1217
1218impl<'tcx> LateLintPass<'tcx> for UngatedAsyncFnTrackCaller {
1219 fn check_fn(
1220 &mut self,
1221 cx: &LateContext<'_>,
1222 fn_kind: HirFnKind<'_>,
1223 _: &'tcx FnDecl<'_>,
1224 _: &'tcx Body<'_>,
1225 span: Span,
1226 def_id: LocalDefId,
1227 ) {
1228 if fn_kind.asyncness().is_async()
1229 && !cx.tcx.features().async_fn_track_caller()
1230 // Now, check if the function has the `#[track_caller]` attribute
1231 && let Some(attr) = cx.tcx.get_attr(def_id, sym::track_caller)
1232 {
1233 cx.emit_span_lint(
1234 UNGATED_ASYNC_FN_TRACK_CALLER,
1235 attr.span(),
1236 BuiltinUngatedAsyncFnTrackCaller { label: span, session: &cx.tcx.sess },
1237 );
1238 }
1239 }
1240}
1241
1242declare_lint! {
1243 /// The `unreachable_pub` lint triggers for `pub` items not reachable from other crates - that
1244 /// means neither directly accessible, nor reexported (with `pub use`), nor leaked through
1245 /// things like return types (which the [`unnameable_types`] lint can detect if desired).
1246 ///
1247 /// ### Example
1248 ///
1249 /// ```rust,compile_fail
1250 /// #![deny(unreachable_pub)]
1251 /// mod foo {
1252 /// pub mod bar {
1253 ///
1254 /// }
1255 /// }
1256 /// ```
1257 ///
1258 /// {{produces}}
1259 ///
1260 /// ### Explanation
1261 ///
1262 /// The `pub` keyword both expresses an intent for an item to be publicly available, and also
1263 /// signals to the compiler to make the item publicly accessible. The intent can only be
1264 /// satisfied, however, if all items which contain this item are *also* publicly accessible.
1265 /// Thus, this lint serves to identify situations where the intent does not match the reality.
1266 ///
1267 /// If you wish the item to be accessible elsewhere within the crate, but not outside it, the
1268 /// `pub(crate)` visibility is recommended to be used instead. This more clearly expresses the
1269 /// intent that the item is only visible within its own crate.
1270 ///
1271 /// This lint is "allow" by default because it will trigger for a large amount of existing Rust code.
1272 /// Eventually it is desired for this to become warn-by-default.
1273 ///
1274 /// [`unnameable_types`]: #unnameable-types
1275 pub UNREACHABLE_PUB,
1276 Allow,
1277 "`pub` items not reachable from crate root"
1278}
1279
1280declare_lint_pass!(
1281 /// Lint for items marked `pub` that aren't reachable from other crates.
1282 UnreachablePub => [UNREACHABLE_PUB]
1283);
1284
1285impl UnreachablePub {
1286 fn perform_lint(
1287 &self,
1288 cx: &LateContext<'_>,
1289 what: &str,
1290 def_id: LocalDefId,
1291 vis_span: Span,
1292 exportable: bool,
1293 ) {
1294 let mut applicability = Applicability::MachineApplicable;
1295 if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
1296 {
1297 // prefer suggesting `pub(super)` instead of `pub(crate)` when possible,
1298 // except when `pub(super) == pub(crate)`
1299 let new_vis = if let Some(ty::Visibility::Restricted(restricted_did)) =
1300 cx.effective_visibilities.effective_vis(def_id).map(|effective_vis| {
1301 effective_vis.at_level(rustc_middle::middle::privacy::Level::Reachable)
1302 })
1303 && let parent_parent = cx
1304 .tcx
1305 .parent_module_from_def_id(cx.tcx.parent_module_from_def_id(def_id).into())
1306 && *restricted_did == parent_parent.to_local_def_id()
1307 && !restricted_did.to_def_id().is_crate_root()
1308 {
1309 "pub(super)"
1310 } else {
1311 "pub(crate)"
1312 };
1313
1314 if vis_span.from_expansion() {
1315 applicability = Applicability::MaybeIncorrect;
1316 }
1317 let def_span = cx.tcx.def_span(def_id);
1318 cx.emit_span_lint(
1319 UNREACHABLE_PUB,
1320 def_span,
1321 BuiltinUnreachablePub {
1322 what,
1323 new_vis,
1324 suggestion: (vis_span, applicability),
1325 help: exportable,
1326 },
1327 );
1328 }
1329 }
1330}
1331
1332impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
1333 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1334 // Do not warn for fake `use` statements.
1335 if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1336 return;
1337 }
1338 self.perform_lint(cx, "item", item.owner_id.def_id, item.vis_span, true);
1339 }
1340
1341 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1342 self.perform_lint(cx, "item", foreign_item.owner_id.def_id, foreign_item.vis_span, true);
1343 }
1344
1345 fn check_field_def(&mut self, _cx: &LateContext<'_>, _field: &hir::FieldDef<'_>) {
1346 // - If an ADT definition is reported then we don't need to check fields
1347 // (as it would add unnecessary complexity to the source code, the struct
1348 // definition is in the immediate proximity to give the "real" visibility).
1349 // - If an ADT is not reported because it's not `pub` - we don't need to
1350 // check fields.
1351 // - If an ADT is not reported because it's reachable - we also don't need
1352 // to check fields because then they are reachable by construction if they
1353 // are pub.
1354 //
1355 // Therefore in no case we check the fields.
1356 //
1357 // cf. https://github.com/rust-lang/rust/pull/126013#issuecomment-2152839205
1358 // cf. https://github.com/rust-lang/rust/pull/126040#issuecomment-2152944506
1359 }
1360
1361 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1362 // Only lint inherent impl items.
1363 if cx.tcx.associated_item(impl_item.owner_id).trait_item_def_id.is_none() {
1364 self.perform_lint(cx, "item", impl_item.owner_id.def_id, impl_item.vis_span, false);
1365 }
1366 }
1367}
1368
1369declare_lint! {
1370 /// The `type_alias_bounds` lint detects bounds in type aliases.
1371 ///
1372 /// ### Example
1373 ///
1374 /// ```rust
1375 /// type SendVec<T: Send> = Vec<T>;
1376 /// ```
1377 ///
1378 /// {{produces}}
1379 ///
1380 /// ### Explanation
1381 ///
1382 /// Trait and lifetime bounds on generic parameters and in where clauses of
1383 /// type aliases are not checked at usage sites of the type alias. Moreover,
1384 /// they are not thoroughly checked for correctness at their definition site
1385 /// either similar to the aliased type.
1386 ///
1387 /// This is a known limitation of the type checker that may be lifted in a
1388 /// future edition. Permitting such bounds in light of this was unintentional.
1389 ///
1390 /// While these bounds may have secondary effects such as enabling the use of
1391 /// "shorthand" associated type paths[^1] and affecting the default trait
1392 /// object lifetime[^2] of trait object types passed to the type alias, this
1393 /// should not have been allowed until the aforementioned restrictions of the
1394 /// type checker have been lifted.
1395 ///
1396 /// Using such bounds is highly discouraged as they are actively misleading.
1397 ///
1398 /// [^1]: I.e., paths of the form `T::Assoc` where `T` is a type parameter
1399 /// bounded by trait `Trait` which defines an associated type called `Assoc`
1400 /// as opposed to a fully qualified path of the form `<T as Trait>::Assoc`.
1401 /// [^2]: <https://doc.rust-lang.org/reference/lifetime-elision.html#default-trait-object-lifetimes>
1402 TYPE_ALIAS_BOUNDS,
1403 Warn,
1404 "bounds in type aliases are not enforced"
1405}
1406
1407declare_lint_pass!(TypeAliasBounds => [TYPE_ALIAS_BOUNDS]);
1408
1409impl TypeAliasBounds {
1410 pub(crate) fn affects_object_lifetime_defaults(pred: &hir::WherePredicate<'_>) -> bool {
1411 // Bounds of the form `T: 'a` with `T` type param affect object lifetime defaults.
1412 if let hir::WherePredicateKind::BoundPredicate(pred) = pred.kind
1413 && pred.bounds.iter().any(|bound| matches!(bound, hir::GenericBound::Outlives(_)))
1414 && pred.bound_generic_params.is_empty() // indeed, even if absent from the RHS
1415 && pred.bounded_ty.as_generic_param().is_some()
1416 {
1417 return true;
1418 }
1419 false
1420 }
1421}
1422
1423impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
1424 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1425 let hir::ItemKind::TyAlias(_, generics, hir_ty) = item.kind else { return };
1426
1427 // There must not be a where clause.
1428 if generics.predicates.is_empty() {
1429 return;
1430 }
1431
1432 // Bounds of lazy type aliases and TAITs are respected.
1433 if cx.tcx.type_alias_is_lazy(item.owner_id) {
1434 return;
1435 }
1436
1437 // FIXME(generic_const_exprs): Revisit this before stabilization.
1438 // See also `tests/ui/const-generics/generic_const_exprs/type-alias-bounds.rs`.
1439 let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
1440 if ty.has_type_flags(ty::TypeFlags::HAS_CT_PROJECTION)
1441 && cx.tcx.features().generic_const_exprs()
1442 {
1443 return;
1444 }
1445
1446 // NOTE(inherent_associated_types): While we currently do take some bounds in type
1447 // aliases into consideration during IAT *selection*, we don't perform full use+def
1448 // site wfchecking for such type aliases. Therefore TAB should still trigger.
1449 // See also `tests/ui/associated-inherent-types/type-alias-bounds.rs`.
1450
1451 let mut where_spans = Vec::new();
1452 let mut inline_spans = Vec::new();
1453 let mut inline_sugg = Vec::new();
1454
1455 for p in generics.predicates {
1456 let span = p.span;
1457 if p.kind.in_where_clause() {
1458 where_spans.push(span);
1459 } else {
1460 for b in p.kind.bounds() {
1461 inline_spans.push(b.span());
1462 }
1463 inline_sugg.push((span, String::new()));
1464 }
1465 }
1466
1467 let mut ty = Some(hir_ty);
1468 let enable_feat_help = cx.tcx.sess.is_nightly_build();
1469
1470 if let [.., label_sp] = *where_spans {
1471 cx.emit_span_lint(
1472 TYPE_ALIAS_BOUNDS,
1473 where_spans,
1474 BuiltinTypeAliasBounds {
1475 in_where_clause: true,
1476 label: label_sp,
1477 enable_feat_help,
1478 suggestions: vec![(generics.where_clause_span, String::new())],
1479 preds: generics.predicates,
1480 ty: ty.take(),
1481 },
1482 );
1483 }
1484 if let [.., label_sp] = *inline_spans {
1485 cx.emit_span_lint(
1486 TYPE_ALIAS_BOUNDS,
1487 inline_spans,
1488 BuiltinTypeAliasBounds {
1489 in_where_clause: false,
1490 label: label_sp,
1491 enable_feat_help,
1492 suggestions: inline_sugg,
1493 preds: generics.predicates,
1494 ty,
1495 },
1496 );
1497 }
1498 }
1499}
1500
1501pub(crate) struct ShorthandAssocTyCollector {
1502 pub(crate) qselves: Vec<Span>,
1503}
1504
1505impl hir::intravisit::Visitor<'_> for ShorthandAssocTyCollector {
1506 fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, _: Span) {
1507 // Look for "type-parameter shorthand-associated-types". I.e., paths of the
1508 // form `T::Assoc` with `T` type param. These are reliant on trait bounds.
1509 if let hir::QPath::TypeRelative(qself, _) = qpath
1510 && qself.as_generic_param().is_some()
1511 {
1512 self.qselves.push(qself.span);
1513 }
1514 hir::intravisit::walk_qpath(self, qpath, id)
1515 }
1516}
1517
1518declare_lint! {
1519 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1520 /// any type parameters.
1521 ///
1522 /// ### Example
1523 ///
1524 /// ```rust
1525 /// #![feature(trivial_bounds)]
1526 /// pub struct A where i32: Copy;
1527 /// ```
1528 ///
1529 /// {{produces}}
1530 ///
1531 /// ### Explanation
1532 ///
1533 /// Usually you would not write a trait bound that you know is always
1534 /// true, or never true. However, when using macros, the macro may not
1535 /// know whether or not the constraint would hold or not at the time when
1536 /// generating the code. Currently, the compiler does not alert you if the
1537 /// constraint is always true, and generates an error if it is never true.
1538 /// The `trivial_bounds` feature changes this to be a warning in both
1539 /// cases, giving macros more freedom and flexibility to generate code,
1540 /// while still providing a signal when writing non-macro code that
1541 /// something is amiss.
1542 ///
1543 /// See [RFC 2056] for more details. This feature is currently only
1544 /// available on the nightly channel, see [tracking issue #48214].
1545 ///
1546 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1547 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1548 TRIVIAL_BOUNDS,
1549 Warn,
1550 "these bounds don't depend on an type parameters"
1551}
1552
1553declare_lint_pass!(
1554 /// Lint for trait and lifetime bounds that don't depend on type parameters
1555 /// which either do nothing, or stop the item from being used.
1556 TrivialConstraints => [TRIVIAL_BOUNDS]
1557);
1558
1559impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
1560 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1561 use rustc_middle::ty::ClauseKind;
1562
1563 if cx.tcx.features().trivial_bounds() {
1564 let predicates = cx.tcx.predicates_of(item.owner_id);
1565 for &(predicate, span) in predicates.predicates {
1566 let predicate_kind_name = match predicate.kind().skip_binder() {
1567 ClauseKind::Trait(..) => "trait",
1568 ClauseKind::TypeOutlives(..) |
1569 ClauseKind::RegionOutlives(..) => "lifetime",
1570
1571 // `ConstArgHasType` is never global as `ct` is always a param
1572 ClauseKind::ConstArgHasType(..)
1573 // Ignore projections, as they can only be global
1574 // if the trait bound is global
1575 | ClauseKind::Projection(..)
1576 // Ignore bounds that a user can't type
1577 | ClauseKind::WellFormed(..)
1578 // FIXME(generic_const_exprs): `ConstEvaluatable` can be written
1579 | ClauseKind::ConstEvaluatable(..)
1580 // Users don't write this directly, only via another trait ref.
1581 | ty::ClauseKind::HostEffect(..) => continue,
1582 };
1583 if predicate.is_global() {
1584 cx.emit_span_lint(
1585 TRIVIAL_BOUNDS,
1586 span,
1587 BuiltinTrivialBounds { predicate_kind_name, predicate },
1588 );
1589 }
1590 }
1591 }
1592 }
1593}
1594
1595declare_lint! {
1596 /// The `double_negations` lint detects expressions of the form `--x`.
1597 ///
1598 /// ### Example
1599 ///
1600 /// ```rust
1601 /// fn main() {
1602 /// let x = 1;
1603 /// let _b = --x;
1604 /// }
1605 /// ```
1606 ///
1607 /// {{produces}}
1608 ///
1609 /// ### Explanation
1610 ///
1611 /// Negating something twice is usually the same as not negating it at all.
1612 /// However, a double negation in Rust can easily be confused with the
1613 /// prefix decrement operator that exists in many languages derived from C.
1614 /// Use `-(-x)` if you really wanted to negate the value twice.
1615 ///
1616 /// To decrement a value, use `x -= 1` instead.
1617 pub DOUBLE_NEGATIONS,
1618 Warn,
1619 "detects expressions of the form `--x`"
1620}
1621
1622declare_lint_pass!(
1623 /// Lint for expressions of the form `--x` that can be confused with C's
1624 /// prefix decrement operator.
1625 DoubleNegations => [DOUBLE_NEGATIONS]
1626);
1627
1628impl EarlyLintPass for DoubleNegations {
1629 #[inline]
1630 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1631 // only lint on the innermost `--` in a chain of `-` operators,
1632 // even if there are 3 or more negations
1633 if let ExprKind::Unary(UnOp::Neg, ref inner) = expr.kind
1634 && let ExprKind::Unary(UnOp::Neg, ref inner2) = inner.kind
1635 && !matches!(inner2.kind, ExprKind::Unary(UnOp::Neg, _))
1636 {
1637 cx.emit_span_lint(
1638 DOUBLE_NEGATIONS,
1639 expr.span,
1640 BuiltinDoubleNegations {
1641 add_parens: BuiltinDoubleNegationsAddParens {
1642 start_span: inner.span.shrink_to_lo(),
1643 end_span: inner.span.shrink_to_hi(),
1644 },
1645 },
1646 );
1647 }
1648 }
1649}
1650
1651declare_lint_pass!(
1652 /// Does nothing as a lint pass, but registers some `Lint`s
1653 /// which are used by other parts of the compiler.
1654 SoftLints => [
1655 WHILE_TRUE,
1656 NON_SHORTHAND_FIELD_PATTERNS,
1657 UNSAFE_CODE,
1658 MISSING_DOCS,
1659 MISSING_COPY_IMPLEMENTATIONS,
1660 MISSING_DEBUG_IMPLEMENTATIONS,
1661 ANONYMOUS_PARAMETERS,
1662 UNUSED_DOC_COMMENTS,
1663 NO_MANGLE_CONST_ITEMS,
1664 NO_MANGLE_GENERIC_ITEMS,
1665 MUTABLE_TRANSMUTES,
1666 UNSTABLE_FEATURES,
1667 UNREACHABLE_PUB,
1668 TYPE_ALIAS_BOUNDS,
1669 TRIVIAL_BOUNDS,
1670 DOUBLE_NEGATIONS
1671 ]
1672);
1673
1674declare_lint! {
1675 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1676 /// pattern], which is deprecated.
1677 ///
1678 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1679 ///
1680 /// ### Example
1681 ///
1682 /// ```rust,edition2018
1683 /// let x = 123;
1684 /// match x {
1685 /// 0...100 => {}
1686 /// _ => {}
1687 /// }
1688 /// ```
1689 ///
1690 /// {{produces}}
1691 ///
1692 /// ### Explanation
1693 ///
1694 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1695 /// confusion with the [`..` range expression]. Use the new form instead.
1696 ///
1697 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1698 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1699 Warn,
1700 "`...` range patterns are deprecated",
1701 @future_incompatible = FutureIncompatibleInfo {
1702 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1703 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1704 };
1705}
1706
1707#[derive(Default)]
1708pub struct EllipsisInclusiveRangePatterns {
1709 /// If `Some(_)`, suppress all subsequent pattern
1710 /// warnings for better diagnostics.
1711 node_id: Option<ast::NodeId>,
1712}
1713
1714impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1715
1716impl EarlyLintPass for EllipsisInclusiveRangePatterns {
1717 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1718 if self.node_id.is_some() {
1719 // Don't recursively warn about patterns inside range endpoints.
1720 return;
1721 }
1722
1723 use self::ast::PatKind;
1724 use self::ast::RangeSyntax::DotDotDot;
1725
1726 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1727 /// corresponding to the ellipsis.
1728 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1729 match &pat.kind {
1730 PatKind::Range(
1731 a,
1732 Some(b),
1733 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1734 ) => Some((a.as_deref(), b, *span)),
1735 _ => None,
1736 }
1737 }
1738
1739 let (parentheses, endpoints) = match &pat.kind {
1740 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(subpat)),
1741 _ => (false, matches_ellipsis_pat(pat)),
1742 };
1743
1744 if let Some((start, end, join)) = endpoints {
1745 if parentheses {
1746 self.node_id = Some(pat.id);
1747 let end = expr_to_string(end);
1748 let replace = match start {
1749 Some(start) => format!("&({}..={})", expr_to_string(start), end),
1750 None => format!("&(..={end})"),
1751 };
1752 if join.edition() >= Edition::Edition2021 {
1753 cx.sess().dcx().emit_err(BuiltinEllipsisInclusiveRangePatterns {
1754 span: pat.span,
1755 suggestion: pat.span,
1756 replace,
1757 });
1758 } else {
1759 cx.emit_span_lint(
1760 ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1761 pat.span,
1762 BuiltinEllipsisInclusiveRangePatternsLint::Parenthesise {
1763 suggestion: pat.span,
1764 replace,
1765 },
1766 );
1767 }
1768 } else {
1769 let replace = "..=";
1770 if join.edition() >= Edition::Edition2021 {
1771 cx.sess().dcx().emit_err(BuiltinEllipsisInclusiveRangePatterns {
1772 span: pat.span,
1773 suggestion: join,
1774 replace: replace.to_string(),
1775 });
1776 } else {
1777 cx.emit_span_lint(
1778 ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1779 join,
1780 BuiltinEllipsisInclusiveRangePatternsLint::NonParenthesise {
1781 suggestion: join,
1782 },
1783 );
1784 }
1785 };
1786 }
1787 }
1788
1789 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1790 if let Some(node_id) = self.node_id {
1791 if pat.id == node_id {
1792 self.node_id = None
1793 }
1794 }
1795 }
1796}
1797
1798declare_lint! {
1799 /// The `keyword_idents_2018` lint detects edition keywords being used as an
1800 /// identifier.
1801 ///
1802 /// ### Example
1803 ///
1804 /// ```rust,edition2015,compile_fail
1805 /// #![deny(keyword_idents_2018)]
1806 /// // edition 2015
1807 /// fn dyn() {}
1808 /// ```
1809 ///
1810 /// {{produces}}
1811 ///
1812 /// ### Explanation
1813 ///
1814 /// Rust [editions] allow the language to evolve without breaking
1815 /// backwards compatibility. This lint catches code that uses new keywords
1816 /// that are added to the language that are used as identifiers (such as a
1817 /// variable name, function name, etc.). If you switch the compiler to a
1818 /// new edition without updating the code, then it will fail to compile if
1819 /// you are using a new keyword as an identifier.
1820 ///
1821 /// You can manually change the identifiers to a non-keyword, or use a
1822 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1823 ///
1824 /// This lint solves the problem automatically. It is "allow" by default
1825 /// because the code is perfectly valid in older editions. The [`cargo
1826 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1827 /// and automatically apply the suggested fix from the compiler (which is
1828 /// to use a raw identifier). This provides a completely automated way to
1829 /// update old code for a new edition.
1830 ///
1831 /// [editions]: https://doc.rust-lang.org/edition-guide/
1832 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1833 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1834 pub KEYWORD_IDENTS_2018,
1835 Allow,
1836 "detects edition keywords being used as an identifier",
1837 @future_incompatible = FutureIncompatibleInfo {
1838 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1839 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1840 };
1841}
1842
1843declare_lint! {
1844 /// The `keyword_idents_2024` lint detects edition keywords being used as an
1845 /// identifier.
1846 ///
1847 /// ### Example
1848 ///
1849 /// ```rust,edition2015,compile_fail
1850 /// #![deny(keyword_idents_2024)]
1851 /// // edition 2015
1852 /// fn gen() {}
1853 /// ```
1854 ///
1855 /// {{produces}}
1856 ///
1857 /// ### Explanation
1858 ///
1859 /// Rust [editions] allow the language to evolve without breaking
1860 /// backwards compatibility. This lint catches code that uses new keywords
1861 /// that are added to the language that are used as identifiers (such as a
1862 /// variable name, function name, etc.). If you switch the compiler to a
1863 /// new edition without updating the code, then it will fail to compile if
1864 /// you are using a new keyword as an identifier.
1865 ///
1866 /// You can manually change the identifiers to a non-keyword, or use a
1867 /// [raw identifier], for example `r#gen`, to transition to a new edition.
1868 ///
1869 /// This lint solves the problem automatically. It is "allow" by default
1870 /// because the code is perfectly valid in older editions. The [`cargo
1871 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1872 /// and automatically apply the suggested fix from the compiler (which is
1873 /// to use a raw identifier). This provides a completely automated way to
1874 /// update old code for a new edition.
1875 ///
1876 /// [editions]: https://doc.rust-lang.org/edition-guide/
1877 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1878 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1879 pub KEYWORD_IDENTS_2024,
1880 Allow,
1881 "detects edition keywords being used as an identifier",
1882 @future_incompatible = FutureIncompatibleInfo {
1883 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
1884 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/gen-keyword.html>",
1885 };
1886}
1887
1888declare_lint_pass!(
1889 /// Check for uses of edition keywords used as an identifier.
1890 KeywordIdents => [KEYWORD_IDENTS_2018, KEYWORD_IDENTS_2024]
1891);
1892
1893struct UnderMacro(bool);
1894
1895impl KeywordIdents {
1896 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: &TokenStream) {
1897 // Check if the preceding token is `$`, because we want to allow `$async`, etc.
1898 let mut prev_dollar = false;
1899 for tt in tokens.iter() {
1900 match tt {
1901 // Only report non-raw idents.
1902 TokenTree::Token(token, _) => {
1903 if let Some((ident, token::IdentIsRaw::No)) = token.ident() {
1904 if !prev_dollar {
1905 self.check_ident_token(cx, UnderMacro(true), ident, "");
1906 }
1907 } else if let Some((ident, token::IdentIsRaw::No)) = token.lifetime() {
1908 self.check_ident_token(
1909 cx,
1910 UnderMacro(true),
1911 ident.without_first_quote(),
1912 "'",
1913 );
1914 } else if token.kind == TokenKind::Dollar {
1915 prev_dollar = true;
1916 continue;
1917 }
1918 }
1919 TokenTree::Delimited(.., tts) => self.check_tokens(cx, tts),
1920 }
1921 prev_dollar = false;
1922 }
1923 }
1924
1925 fn check_ident_token(
1926 &mut self,
1927 cx: &EarlyContext<'_>,
1928 UnderMacro(under_macro): UnderMacro,
1929 ident: Ident,
1930 prefix: &'static str,
1931 ) {
1932 let (lint, edition) = match ident.name {
1933 kw::Async | kw::Await | kw::Try => (KEYWORD_IDENTS_2018, Edition::Edition2018),
1934
1935 // rust-lang/rust#56327: Conservatively do not
1936 // attempt to report occurrences of `dyn` within
1937 // macro definitions or invocations, because `dyn`
1938 // can legitimately occur as a contextual keyword
1939 // in 2015 code denoting its 2018 meaning, and we
1940 // do not want rustfix to inject bugs into working
1941 // code by rewriting such occurrences.
1942 //
1943 // But if we see `dyn` outside of a macro, we know
1944 // its precise role in the parsed AST and thus are
1945 // assured this is truly an attempt to use it as
1946 // an identifier.
1947 kw::Dyn if !under_macro => (KEYWORD_IDENTS_2018, Edition::Edition2018),
1948
1949 kw::Gen => (KEYWORD_IDENTS_2024, Edition::Edition2024),
1950
1951 _ => return,
1952 };
1953
1954 // Don't lint `r#foo`.
1955 if ident.span.edition() >= edition
1956 || cx.sess().psess.raw_identifier_spans.contains(ident.span)
1957 {
1958 return;
1959 }
1960
1961 cx.emit_span_lint(
1962 lint,
1963 ident.span,
1964 BuiltinKeywordIdents { kw: ident, next: edition, suggestion: ident.span, prefix },
1965 );
1966 }
1967}
1968
1969impl EarlyLintPass for KeywordIdents {
1970 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
1971 self.check_tokens(cx, &mac_def.body.tokens);
1972 }
1973 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1974 self.check_tokens(cx, &mac.args.tokens);
1975 }
1976 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: &Ident) {
1977 if ident.name.as_str().starts_with('\'') {
1978 self.check_ident_token(cx, UnderMacro(false), ident.without_first_quote(), "'");
1979 } else {
1980 self.check_ident_token(cx, UnderMacro(false), *ident, "");
1981 }
1982 }
1983}
1984
1985declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1986
1987impl ExplicitOutlivesRequirements {
1988 fn lifetimes_outliving_lifetime<'tcx>(
1989 tcx: TyCtxt<'tcx>,
1990 inferred_outlives: impl Iterator<Item = &'tcx (ty::Clause<'tcx>, Span)>,
1991 item: LocalDefId,
1992 lifetime: LocalDefId,
1993 ) -> Vec<ty::Region<'tcx>> {
1994 let item_generics = tcx.generics_of(item);
1995
1996 inferred_outlives
1997 .filter_map(|(clause, _)| match clause.kind().skip_binder() {
1998 ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a.kind() {
1999 ty::ReEarlyParam(ebr)
2000 if item_generics.region_param(ebr, tcx).def_id == lifetime.to_def_id() =>
2001 {
2002 Some(b)
2003 }
2004 _ => None,
2005 },
2006 _ => None,
2007 })
2008 .collect()
2009 }
2010
2011 fn lifetimes_outliving_type<'tcx>(
2012 inferred_outlives: impl Iterator<Item = &'tcx (ty::Clause<'tcx>, Span)>,
2013 index: u32,
2014 ) -> Vec<ty::Region<'tcx>> {
2015 inferred_outlives
2016 .filter_map(|(clause, _)| match clause.kind().skip_binder() {
2017 ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2018 a.is_param(index).then_some(b)
2019 }
2020 _ => None,
2021 })
2022 .collect()
2023 }
2024
2025 fn collect_outlives_bound_spans<'tcx>(
2026 &self,
2027 tcx: TyCtxt<'tcx>,
2028 bounds: &hir::GenericBounds<'_>,
2029 inferred_outlives: &[ty::Region<'tcx>],
2030 predicate_span: Span,
2031 item: DefId,
2032 ) -> Vec<(usize, Span)> {
2033 use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
2034
2035 let item_generics = tcx.generics_of(item);
2036
2037 bounds
2038 .iter()
2039 .enumerate()
2040 .filter_map(|(i, bound)| {
2041 let hir::GenericBound::Outlives(lifetime) = bound else {
2042 return None;
2043 };
2044
2045 let is_inferred = match tcx.named_bound_var(lifetime.hir_id) {
2046 Some(ResolvedArg::EarlyBound(def_id)) => inferred_outlives
2047 .iter()
2048 .any(|r| matches!(r.kind(), ty::ReEarlyParam(ebr) if { item_generics.region_param(ebr, tcx).def_id == def_id.to_def_id() })),
2049 _ => false,
2050 };
2051
2052 if !is_inferred {
2053 return None;
2054 }
2055
2056 let span = bound.span().find_ancestor_inside(predicate_span)?;
2057 if span.in_external_macro(tcx.sess.source_map()) {
2058 return None;
2059 }
2060
2061 Some((i, span))
2062 })
2063 .collect()
2064 }
2065
2066 fn consolidate_outlives_bound_spans(
2067 &self,
2068 lo: Span,
2069 bounds: &hir::GenericBounds<'_>,
2070 bound_spans: Vec<(usize, Span)>,
2071 ) -> Vec<Span> {
2072 if bounds.is_empty() {
2073 return Vec::new();
2074 }
2075 if bound_spans.len() == bounds.len() {
2076 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2077 // If all bounds are inferable, we want to delete the colon, so
2078 // start from just after the parameter (span passed as argument)
2079 vec![lo.to(last_bound_span)]
2080 } else {
2081 let mut merged = Vec::new();
2082 let mut last_merged_i = None;
2083
2084 let mut from_start = true;
2085 for (i, bound_span) in bound_spans {
2086 match last_merged_i {
2087 // If the first bound is inferable, our span should also eat the leading `+`.
2088 None if i == 0 => {
2089 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2090 last_merged_i = Some(0);
2091 }
2092 // If consecutive bounds are inferable, merge their spans
2093 Some(h) if i == h + 1 => {
2094 if let Some(tail) = merged.last_mut() {
2095 // Also eat the trailing `+` if the first
2096 // more-than-one bound is inferable
2097 let to_span = if from_start && i < bounds.len() {
2098 bounds[i + 1].span().shrink_to_lo()
2099 } else {
2100 bound_span
2101 };
2102 *tail = tail.to(to_span);
2103 last_merged_i = Some(i);
2104 } else {
2105 bug!("another bound-span visited earlier");
2106 }
2107 }
2108 _ => {
2109 // When we find a non-inferable bound, subsequent inferable bounds
2110 // won't be consecutive from the start (and we'll eat the leading
2111 // `+` rather than the trailing one)
2112 from_start = false;
2113 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2114 last_merged_i = Some(i);
2115 }
2116 }
2117 }
2118 merged
2119 }
2120 }
2121}
2122
2123impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
2124 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2125 use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
2126
2127 let def_id = item.owner_id.def_id;
2128 if let hir::ItemKind::Struct(_, generics, _)
2129 | hir::ItemKind::Enum(_, generics, _)
2130 | hir::ItemKind::Union(_, generics, _) = item.kind
2131 {
2132 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2133 if inferred_outlives.is_empty() {
2134 return;
2135 }
2136
2137 let ty_generics = cx.tcx.generics_of(def_id);
2138 let num_where_predicates = generics
2139 .predicates
2140 .iter()
2141 .filter(|predicate| predicate.kind.in_where_clause())
2142 .count();
2143
2144 let mut bound_count = 0;
2145 let mut lint_spans = Vec::new();
2146 let mut where_lint_spans = Vec::new();
2147 let mut dropped_where_predicate_count = 0;
2148 for (i, where_predicate) in generics.predicates.iter().enumerate() {
2149 let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
2150 match where_predicate.kind {
2151 hir::WherePredicateKind::RegionPredicate(predicate) => {
2152 if let Some(ResolvedArg::EarlyBound(region_def_id)) =
2153 cx.tcx.named_bound_var(predicate.lifetime.hir_id)
2154 {
2155 (
2156 Self::lifetimes_outliving_lifetime(
2157 cx.tcx,
2158 // don't warn if the inferred span actually came from the predicate we're looking at
2159 // this happens if the type is recursively defined
2160 inferred_outlives.iter().filter(|(_, span)| {
2161 !where_predicate.span.contains(*span)
2162 }),
2163 item.owner_id.def_id,
2164 region_def_id,
2165 ),
2166 &predicate.bounds,
2167 where_predicate.span,
2168 predicate.in_where_clause,
2169 )
2170 } else {
2171 continue;
2172 }
2173 }
2174 hir::WherePredicateKind::BoundPredicate(predicate) => {
2175 // FIXME we can also infer bounds on associated types,
2176 // and should check for them here.
2177 match predicate.bounded_ty.kind {
2178 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => {
2179 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2180 continue;
2181 };
2182 let index = ty_generics.param_def_id_to_index[&def_id];
2183 (
2184 Self::lifetimes_outliving_type(
2185 // don't warn if the inferred span actually came from the predicate we're looking at
2186 // this happens if the type is recursively defined
2187 inferred_outlives.iter().filter(|(_, span)| {
2188 !where_predicate.span.contains(*span)
2189 }),
2190 index,
2191 ),
2192 &predicate.bounds,
2193 where_predicate.span,
2194 predicate.origin == PredicateOrigin::WhereClause,
2195 )
2196 }
2197 _ => {
2198 continue;
2199 }
2200 }
2201 }
2202 _ => continue,
2203 };
2204 if relevant_lifetimes.is_empty() {
2205 continue;
2206 }
2207
2208 let bound_spans = self.collect_outlives_bound_spans(
2209 cx.tcx,
2210 bounds,
2211 &relevant_lifetimes,
2212 predicate_span,
2213 item.owner_id.to_def_id(),
2214 );
2215 bound_count += bound_spans.len();
2216
2217 let drop_predicate = bound_spans.len() == bounds.len();
2218 if drop_predicate && in_where_clause {
2219 dropped_where_predicate_count += 1;
2220 }
2221
2222 if drop_predicate {
2223 if !in_where_clause {
2224 lint_spans.push(predicate_span);
2225 } else if predicate_span.from_expansion() {
2226 // Don't try to extend the span if it comes from a macro expansion.
2227 where_lint_spans.push(predicate_span);
2228 } else if i + 1 < num_where_predicates {
2229 // If all the bounds on a predicate were inferable and there are
2230 // further predicates, we want to eat the trailing comma.
2231 let next_predicate_span = generics.predicates[i + 1].span;
2232 if next_predicate_span.from_expansion() {
2233 where_lint_spans.push(predicate_span);
2234 } else {
2235 where_lint_spans
2236 .push(predicate_span.to(next_predicate_span.shrink_to_lo()));
2237 }
2238 } else {
2239 // Eat the optional trailing comma after the last predicate.
2240 let where_span = generics.where_clause_span;
2241 if where_span.from_expansion() {
2242 where_lint_spans.push(predicate_span);
2243 } else {
2244 where_lint_spans.push(predicate_span.to(where_span.shrink_to_hi()));
2245 }
2246 }
2247 } else {
2248 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2249 predicate_span.shrink_to_lo(),
2250 bounds,
2251 bound_spans,
2252 ));
2253 }
2254 }
2255
2256 // If all predicates in where clause are inferable, drop the entire clause
2257 // (including the `where`)
2258 if generics.has_where_clause_predicates
2259 && dropped_where_predicate_count == num_where_predicates
2260 {
2261 let where_span = generics.where_clause_span;
2262 // Extend the where clause back to the closing `>` of the
2263 // generics, except for tuple struct, which have the `where`
2264 // after the fields of the struct.
2265 let full_where_span =
2266 if let hir::ItemKind::Struct(_, _, hir::VariantData::Tuple(..)) = item.kind {
2267 where_span
2268 } else {
2269 generics.span.shrink_to_hi().to(where_span)
2270 };
2271
2272 // Due to macro expansions, the `full_where_span` might not actually contain all
2273 // predicates.
2274 if where_lint_spans.iter().all(|&sp| full_where_span.contains(sp)) {
2275 lint_spans.push(full_where_span);
2276 } else {
2277 lint_spans.extend(where_lint_spans);
2278 }
2279 } else {
2280 lint_spans.extend(where_lint_spans);
2281 }
2282
2283 if !lint_spans.is_empty() {
2284 // Do not automatically delete outlives requirements from macros.
2285 let applicability = if lint_spans.iter().all(|sp| sp.can_be_used_for_suggestions())
2286 {
2287 Applicability::MachineApplicable
2288 } else {
2289 Applicability::MaybeIncorrect
2290 };
2291
2292 // Due to macros, there might be several predicates with the same span
2293 // and we only want to suggest removing them once.
2294 lint_spans.sort_unstable();
2295 lint_spans.dedup();
2296
2297 cx.emit_span_lint(
2298 EXPLICIT_OUTLIVES_REQUIREMENTS,
2299 lint_spans.clone(),
2300 BuiltinExplicitOutlives {
2301 count: bound_count,
2302 suggestion: BuiltinExplicitOutlivesSuggestion {
2303 spans: lint_spans,
2304 applicability,
2305 },
2306 },
2307 );
2308 }
2309 }
2310 }
2311}
2312
2313declare_lint! {
2314 /// The `incomplete_features` lint detects unstable features enabled with
2315 /// the [`feature` attribute] that may function improperly in some or all
2316 /// cases.
2317 ///
2318 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2319 ///
2320 /// ### Example
2321 ///
2322 /// ```rust
2323 /// #![feature(generic_const_exprs)]
2324 /// ```
2325 ///
2326 /// {{produces}}
2327 ///
2328 /// ### Explanation
2329 ///
2330 /// Although it is encouraged for people to experiment with unstable
2331 /// features, some of them are known to be incomplete or faulty. This lint
2332 /// is a signal that the feature has not yet been finished, and you may
2333 /// experience problems with it.
2334 pub INCOMPLETE_FEATURES,
2335 Warn,
2336 "incomplete features that may function improperly in some or all cases"
2337}
2338
2339declare_lint! {
2340 /// The `internal_features` lint detects unstable features enabled with
2341 /// the [`feature` attribute] that are internal to the compiler or standard
2342 /// library.
2343 ///
2344 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2345 ///
2346 /// ### Example
2347 ///
2348 /// ```rust
2349 /// #![feature(rustc_attrs)]
2350 /// ```
2351 ///
2352 /// {{produces}}
2353 ///
2354 /// ### Explanation
2355 ///
2356 /// These features are an implementation detail of the compiler and standard
2357 /// library and are not supposed to be used in user code.
2358 pub INTERNAL_FEATURES,
2359 Warn,
2360 "internal features are not supposed to be used"
2361}
2362
2363declare_lint_pass!(
2364 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/unstable.rs`.
2365 IncompleteInternalFeatures => [INCOMPLETE_FEATURES, INTERNAL_FEATURES]
2366);
2367
2368impl EarlyLintPass for IncompleteInternalFeatures {
2369 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2370 let features = cx.builder.features();
2371 let lang_features =
2372 features.enabled_lang_features().iter().map(|feat| (feat.gate_name, feat.attr_sp));
2373 let lib_features =
2374 features.enabled_lib_features().iter().map(|feat| (feat.gate_name, feat.attr_sp));
2375
2376 lang_features
2377 .chain(lib_features)
2378 .filter(|(name, _)| features.incomplete(*name) || features.internal(*name))
2379 .for_each(|(name, span)| {
2380 if features.incomplete(name) {
2381 let note = rustc_feature::find_feature_issue(name, GateIssue::Language)
2382 .map(|n| BuiltinFeatureIssueNote { n });
2383 let help =
2384 HAS_MIN_FEATURES.contains(&name).then_some(BuiltinIncompleteFeaturesHelp);
2385
2386 cx.emit_span_lint(
2387 INCOMPLETE_FEATURES,
2388 span,
2389 BuiltinIncompleteFeatures { name, note, help },
2390 );
2391 } else {
2392 cx.emit_span_lint(INTERNAL_FEATURES, span, BuiltinInternalFeatures { name });
2393 }
2394 });
2395 }
2396}
2397
2398const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2399
2400declare_lint! {
2401 /// The `invalid_value` lint detects creating a value that is not valid,
2402 /// such as a null reference.
2403 ///
2404 /// ### Example
2405 ///
2406 /// ```rust,no_run
2407 /// # #![allow(unused)]
2408 /// unsafe {
2409 /// let x: &'static i32 = std::mem::zeroed();
2410 /// }
2411 /// ```
2412 ///
2413 /// {{produces}}
2414 ///
2415 /// ### Explanation
2416 ///
2417 /// In some situations the compiler can detect that the code is creating
2418 /// an invalid value, which should be avoided.
2419 ///
2420 /// In particular, this lint will check for improper use of
2421 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2422 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2423 /// lint should provide extra information to indicate what the problem is
2424 /// and a possible solution.
2425 ///
2426 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2427 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2428 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2429 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2430 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2431 pub INVALID_VALUE,
2432 Warn,
2433 "an invalid value is being created (such as a null reference)"
2434}
2435
2436declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2437
2438/// Information about why a type cannot be initialized this way.
2439pub struct InitError {
2440 pub(crate) message: String,
2441 /// Spans from struct fields and similar that can be obtained from just the type.
2442 pub(crate) span: Option<Span>,
2443 /// Used to report a trace through adts.
2444 pub(crate) nested: Option<Box<InitError>>,
2445}
2446impl InitError {
2447 fn spanned(self, span: Span) -> InitError {
2448 Self { span: Some(span), ..self }
2449 }
2450
2451 fn nested(self, nested: impl Into<Option<InitError>>) -> InitError {
2452 assert!(self.nested.is_none());
2453 Self { nested: nested.into().map(Box::new), ..self }
2454 }
2455}
2456
2457impl<'a> From<&'a str> for InitError {
2458 fn from(s: &'a str) -> Self {
2459 s.to_owned().into()
2460 }
2461}
2462impl From<String> for InitError {
2463 fn from(message: String) -> Self {
2464 Self { message, span: None, nested: None }
2465 }
2466}
2467
2468impl<'tcx> LateLintPass<'tcx> for InvalidValue {
2469 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2470 #[derive(Debug, Copy, Clone, PartialEq)]
2471 enum InitKind {
2472 Zeroed,
2473 Uninit,
2474 }
2475
2476 /// Test if this constant is all-0.
2477 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2478 use hir::ExprKind::*;
2479 use rustc_ast::LitKind::*;
2480 match &expr.kind {
2481 Lit(lit) => {
2482 if let Int(i, _) = lit.node {
2483 i == 0
2484 } else {
2485 false
2486 }
2487 }
2488 Tup(tup) => tup.iter().all(is_zero),
2489 _ => false,
2490 }
2491 }
2492
2493 /// Determine if this expression is a "dangerous initialization".
2494 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2495 if let hir::ExprKind::Call(path_expr, args) = expr.kind {
2496 // Find calls to `mem::{uninitialized,zeroed}` methods.
2497 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2498 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2499 match cx.tcx.get_diagnostic_name(def_id) {
2500 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2501 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2502 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2503 _ => {}
2504 }
2505 }
2506 } else if let hir::ExprKind::MethodCall(_, receiver, ..) = expr.kind {
2507 // Find problematic calls to `MaybeUninit::assume_init`.
2508 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2509 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2510 // This is a call to *some* method named `assume_init`.
2511 // See if the `self` parameter is one of the dangerous constructors.
2512 if let hir::ExprKind::Call(path_expr, _) = receiver.kind {
2513 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2514 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2515 match cx.tcx.get_diagnostic_name(def_id) {
2516 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2517 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2518 _ => {}
2519 }
2520 }
2521 }
2522 }
2523 }
2524
2525 None
2526 }
2527
2528 fn variant_find_init_error<'tcx>(
2529 cx: &LateContext<'tcx>,
2530 ty: Ty<'tcx>,
2531 variant: &VariantDef,
2532 args: ty::GenericArgsRef<'tcx>,
2533 descr: &str,
2534 init: InitKind,
2535 ) -> Option<InitError> {
2536 let mut field_err = variant.fields.iter().find_map(|field| {
2537 ty_find_init_error(cx, field.ty(cx.tcx, args), init).map(|mut err| {
2538 if !field.did.is_local() {
2539 err
2540 } else if err.span.is_none() {
2541 err.span = Some(cx.tcx.def_span(field.did));
2542 write!(&mut err.message, " (in this {descr})").unwrap();
2543 err
2544 } else {
2545 InitError::from(format!("in this {descr}"))
2546 .spanned(cx.tcx.def_span(field.did))
2547 .nested(err)
2548 }
2549 })
2550 });
2551
2552 // Check if this ADT has a constrained layout (like `NonNull` and friends).
2553 if let Ok(layout) = cx.tcx.layout_of(cx.typing_env().as_query_input(ty)) {
2554 if let BackendRepr::Scalar(scalar) | BackendRepr::ScalarPair(scalar, _) =
2555 &layout.backend_repr
2556 {
2557 let range = scalar.valid_range(cx);
2558 let msg = if !range.contains(0) {
2559 "must be non-null"
2560 } else if init == InitKind::Uninit && !scalar.is_always_valid(cx) {
2561 // Prefer reporting on the fields over the entire struct for uninit,
2562 // as the information bubbles out and it may be unclear why the type can't
2563 // be null from just its outside signature.
2564
2565 "must be initialized inside its custom valid range"
2566 } else {
2567 return field_err;
2568 };
2569 if let Some(field_err) = &mut field_err {
2570 // Most of the time, if the field error is the same as the struct error,
2571 // the struct error only happens because of the field error.
2572 if field_err.message.contains(msg) {
2573 field_err.message = format!("because {}", field_err.message);
2574 }
2575 }
2576 return Some(InitError::from(format!("`{ty}` {msg}")).nested(field_err));
2577 }
2578 }
2579 field_err
2580 }
2581
2582 /// Return `Some` only if we are sure this type does *not*
2583 /// allow zero initialization.
2584 fn ty_find_init_error<'tcx>(
2585 cx: &LateContext<'tcx>,
2586 ty: Ty<'tcx>,
2587 init: InitKind,
2588 ) -> Option<InitError> {
2589 let ty = cx.tcx.try_normalize_erasing_regions(cx.typing_env(), ty).unwrap_or(ty);
2590
2591 match ty.kind() {
2592 // Primitive types that don't like 0 as a value.
2593 ty::Ref(..) => Some("references must be non-null".into()),
2594 ty::Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),
2595 ty::FnPtr(..) => Some("function pointers must be non-null".into()),
2596 ty::Never => Some("the `!` type has no valid value".into()),
2597 ty::RawPtr(ty, _) if matches!(ty.kind(), ty::Dynamic(..)) =>
2598 // raw ptr to dyn Trait
2599 {
2600 Some("the vtable of a wide raw pointer must be non-null".into())
2601 }
2602 // Primitive types with other constraints.
2603 ty::Bool if init == InitKind::Uninit => {
2604 Some("booleans must be either `true` or `false`".into())
2605 }
2606 ty::Char if init == InitKind::Uninit => {
2607 Some("characters must be a valid Unicode codepoint".into())
2608 }
2609 ty::Int(_) | ty::Uint(_) if init == InitKind::Uninit => {
2610 Some("integers must be initialized".into())
2611 }
2612 ty::Float(_) if init == InitKind::Uninit => {
2613 Some("floats must be initialized".into())
2614 }
2615 ty::RawPtr(_, _) if init == InitKind::Uninit => {
2616 Some("raw pointers must be initialized".into())
2617 }
2618 // Recurse and checks for some compound types. (but not unions)
2619 ty::Adt(adt_def, args) if !adt_def.is_union() => {
2620 // Handle structs.
2621 if adt_def.is_struct() {
2622 return variant_find_init_error(
2623 cx,
2624 ty,
2625 adt_def.non_enum_variant(),
2626 args,
2627 "struct field",
2628 init,
2629 );
2630 }
2631 // And now, enums.
2632 let span = cx.tcx.def_span(adt_def.did());
2633 let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
2634 let definitely_inhabited = match variant
2635 .inhabited_predicate(cx.tcx, *adt_def)
2636 .instantiate(cx.tcx, args)
2637 .apply_any_module(cx.tcx, cx.typing_env())
2638 {
2639 // Entirely skip uninhabited variants.
2640 Some(false) => return None,
2641 // Forward the others, but remember which ones are definitely inhabited.
2642 Some(true) => true,
2643 None => false,
2644 };
2645 Some((variant, definitely_inhabited))
2646 });
2647 let Some(first_variant) = potential_variants.next() else {
2648 return Some(
2649 InitError::from("enums with no inhabited variants have no valid value")
2650 .spanned(span),
2651 );
2652 };
2653 // So we have at least one potentially inhabited variant. Might we have two?
2654 let Some(second_variant) = potential_variants.next() else {
2655 // There is only one potentially inhabited variant. So we can recursively
2656 // check that variant!
2657 return variant_find_init_error(
2658 cx,
2659 ty,
2660 first_variant.0,
2661 args,
2662 "field of the only potentially inhabited enum variant",
2663 init,
2664 );
2665 };
2666 // So we have at least two potentially inhabited variants. If we can prove that
2667 // we have at least two *definitely* inhabited variants, then we have a tag and
2668 // hence leaving this uninit is definitely disallowed. (Leaving it zeroed could
2669 // be okay, depending on which variant is encoded as zero tag.)
2670 if init == InitKind::Uninit {
2671 let definitely_inhabited = (first_variant.1 as usize)
2672 + (second_variant.1 as usize)
2673 + potential_variants
2674 .filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
2675 .count();
2676 if definitely_inhabited > 1 {
2677 return Some(InitError::from(
2678 "enums with multiple inhabited variants have to be initialized to a variant",
2679 ).spanned(span));
2680 }
2681 }
2682 // We couldn't find anything wrong here.
2683 None
2684 }
2685 ty::Tuple(..) => {
2686 // Proceed recursively, check all fields.
2687 ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2688 }
2689 ty::Array(ty, len) => {
2690 if matches!(len.try_to_target_usize(cx.tcx), Some(v) if v > 0) {
2691 // Array length known at array non-empty -- recurse.
2692 ty_find_init_error(cx, *ty, init)
2693 } else {
2694 // Empty array or size unknown.
2695 None
2696 }
2697 }
2698 // Conservative fallback.
2699 _ => None,
2700 }
2701 }
2702
2703 if let Some(init) = is_dangerous_init(cx, expr) {
2704 // This conjures an instance of a type out of nothing,
2705 // using zeroed or uninitialized memory.
2706 // We are extremely conservative with what we warn about.
2707 let conjured_ty = cx.typeck_results().expr_ty(expr);
2708 if let Some(err) = with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init)) {
2709 let msg = match init {
2710 InitKind::Zeroed => fluent::lint_builtin_unpermitted_type_init_zeroed,
2711 InitKind::Uninit => fluent::lint_builtin_unpermitted_type_init_uninit,
2712 };
2713 let sub = BuiltinUnpermittedTypeInitSub { err };
2714 cx.emit_span_lint(
2715 INVALID_VALUE,
2716 expr.span,
2717 BuiltinUnpermittedTypeInit {
2718 msg,
2719 ty: conjured_ty,
2720 label: expr.span,
2721 sub,
2722 tcx: cx.tcx,
2723 },
2724 );
2725 }
2726 }
2727 }
2728}
2729
2730declare_lint! {
2731 /// The `deref_nullptr` lint detects when a null pointer is dereferenced,
2732 /// which causes [undefined behavior].
2733 ///
2734 /// ### Example
2735 ///
2736 /// ```rust,no_run
2737 /// # #![allow(unused)]
2738 /// use std::ptr;
2739 /// unsafe {
2740 /// let x = &*ptr::null::<i32>();
2741 /// let x = ptr::addr_of!(*ptr::null::<i32>());
2742 /// let x = *(0 as *const i32);
2743 /// }
2744 /// ```
2745 ///
2746 /// {{produces}}
2747 ///
2748 /// ### Explanation
2749 ///
2750 /// Dereferencing a null pointer causes [undefined behavior] if it is accessed
2751 /// (loaded from or stored to).
2752 ///
2753 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2754 pub DEREF_NULLPTR,
2755 Warn,
2756 "detects when an null pointer is dereferenced"
2757}
2758
2759declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
2760
2761impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
2762 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2763 /// test if expression is a null ptr
2764 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
2765 match &expr.kind {
2766 hir::ExprKind::Cast(expr, ty) => {
2767 if let hir::TyKind::Ptr(_) = ty.kind {
2768 return is_zero(expr) || is_null_ptr(cx, expr);
2769 }
2770 }
2771 // check for call to `core::ptr::null` or `core::ptr::null_mut`
2772 hir::ExprKind::Call(path, _) => {
2773 if let hir::ExprKind::Path(ref qpath) = path.kind {
2774 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
2775 return matches!(
2776 cx.tcx.get_diagnostic_name(def_id),
2777 Some(sym::ptr_null | sym::ptr_null_mut)
2778 );
2779 }
2780 }
2781 }
2782 _ => {}
2783 }
2784 false
2785 }
2786
2787 /// test if expression is the literal `0`
2788 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2789 match &expr.kind {
2790 hir::ExprKind::Lit(lit) => {
2791 if let LitKind::Int(a, _) = lit.node {
2792 return a == 0;
2793 }
2794 }
2795 _ => {}
2796 }
2797 false
2798 }
2799
2800 if let hir::ExprKind::Unary(hir::UnOp::Deref, expr_deref) = expr.kind
2801 && is_null_ptr(cx, expr_deref)
2802 {
2803 if let hir::Node::Expr(hir::Expr {
2804 kind: hir::ExprKind::AddrOf(hir::BorrowKind::Raw, ..),
2805 ..
2806 }) = cx.tcx.parent_hir_node(expr.hir_id)
2807 {
2808 // `&raw *NULL` is ok.
2809 } else {
2810 cx.emit_span_lint(
2811 DEREF_NULLPTR,
2812 expr.span,
2813 BuiltinDerefNullptr { label: expr.span },
2814 );
2815 }
2816 }
2817 }
2818}
2819
2820declare_lint! {
2821 /// The `named_asm_labels` lint detects the use of named labels in the
2822 /// inline `asm!` macro.
2823 ///
2824 /// ### Example
2825 ///
2826 /// ```rust,compile_fail
2827 /// # #![feature(asm_experimental_arch)]
2828 /// use std::arch::asm;
2829 ///
2830 /// fn main() {
2831 /// unsafe {
2832 /// asm!("foo: bar");
2833 /// }
2834 /// }
2835 /// ```
2836 ///
2837 /// {{produces}}
2838 ///
2839 /// ### Explanation
2840 ///
2841 /// LLVM is allowed to duplicate inline assembly blocks for any
2842 /// reason, for example when it is in a function that gets inlined. Because
2843 /// of this, GNU assembler [local labels] *must* be used instead of labels
2844 /// with a name. Using named labels might cause assembler or linker errors.
2845 ///
2846 /// See the explanation in [Rust By Example] for more details.
2847 ///
2848 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
2849 /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
2850 pub NAMED_ASM_LABELS,
2851 Deny,
2852 "named labels in inline assembly",
2853}
2854
2855declare_lint! {
2856 /// The `binary_asm_labels` lint detects the use of numeric labels containing only binary
2857 /// digits in the inline `asm!` macro.
2858 ///
2859 /// ### Example
2860 ///
2861 /// ```rust,ignore (fails on non-x86_64)
2862 /// #![cfg(target_arch = "x86_64")]
2863 ///
2864 /// use std::arch::asm;
2865 ///
2866 /// fn main() {
2867 /// unsafe {
2868 /// asm!("0: jmp 0b");
2869 /// }
2870 /// }
2871 /// ```
2872 ///
2873 /// This will produce:
2874 ///
2875 /// ```text
2876 /// error: avoid using labels containing only the digits `0` and `1` in inline assembly
2877 /// --> <source>:7:15
2878 /// |
2879 /// 7 | asm!("0: jmp 0b");
2880 /// | ^ use a different label that doesn't start with `0` or `1`
2881 /// |
2882 /// = help: start numbering with `2` instead
2883 /// = note: an LLVM bug makes these labels ambiguous with a binary literal number on x86
2884 /// = note: see <https://github.com/llvm/llvm-project/issues/99547> for more information
2885 /// = note: `#[deny(binary_asm_labels)]` on by default
2886 /// ```
2887 ///
2888 /// ### Explanation
2889 ///
2890 /// An [LLVM bug] causes this code to fail to compile because it interprets the `0b` as a binary
2891 /// literal instead of a reference to the previous local label `0`. To work around this bug,
2892 /// don't use labels that could be confused with a binary literal.
2893 ///
2894 /// This behavior is platform-specific to x86 and x86-64.
2895 ///
2896 /// See the explanation in [Rust By Example] for more details.
2897 ///
2898 /// [LLVM bug]: https://github.com/llvm/llvm-project/issues/99547
2899 /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
2900 pub BINARY_ASM_LABELS,
2901 Deny,
2902 "labels in inline assembly containing only 0 or 1 digits",
2903}
2904
2905declare_lint_pass!(AsmLabels => [NAMED_ASM_LABELS, BINARY_ASM_LABELS]);
2906
2907#[derive(Debug, Clone, Copy, PartialEq, Eq)]
2908enum AsmLabelKind {
2909 Named,
2910 FormatArg,
2911 Binary,
2912}
2913
2914impl<'tcx> LateLintPass<'tcx> for AsmLabels {
2915 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
2916 if let hir::Expr {
2917 kind:
2918 hir::ExprKind::InlineAsm(hir::InlineAsm {
2919 asm_macro: AsmMacro::Asm | AsmMacro::NakedAsm,
2920 template_strs,
2921 options,
2922 ..
2923 }),
2924 ..
2925 } = expr
2926 {
2927 // asm with `options(raw)` does not do replacement with `{` and `}`.
2928 let raw = options.contains(InlineAsmOptions::RAW);
2929
2930 for (template_sym, template_snippet, template_span) in template_strs.iter() {
2931 let template_str = template_sym.as_str();
2932 let find_label_span = |needle: &str| -> Option<Span> {
2933 if let Some(template_snippet) = template_snippet {
2934 let snippet = template_snippet.as_str();
2935 if let Some(pos) = snippet.find(needle) {
2936 let end = pos
2937 + snippet[pos..]
2938 .find(|c| c == ':')
2939 .unwrap_or(snippet[pos..].len() - 1);
2940 let inner = InnerSpan::new(pos, end);
2941 return Some(template_span.from_inner(inner));
2942 }
2943 }
2944
2945 None
2946 };
2947
2948 // diagnostics are emitted per-template, so this is created here as opposed to the outer loop
2949 let mut spans = Vec::new();
2950
2951 // A semicolon might not actually be specified as a separator for all targets, but
2952 // it seems like LLVM accepts it always.
2953 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
2954 for statement in statements {
2955 // If there's a comment, trim it from the statement
2956 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
2957
2958 // In this loop, if there is ever a non-label, no labels can come after it.
2959 let mut start_idx = 0;
2960 'label_loop: for (idx, _) in statement.match_indices(':') {
2961 let possible_label = statement[start_idx..idx].trim();
2962 let mut chars = possible_label.chars();
2963
2964 let Some(start) = chars.next() else {
2965 // Empty string means a leading ':' in this section, which is not a
2966 // label.
2967 break 'label_loop;
2968 };
2969
2970 // Whether a { bracket has been seen and its } hasn't been found yet.
2971 let mut in_bracket = false;
2972 let mut label_kind = AsmLabelKind::Named;
2973
2974 // A label can also start with a format arg, if it's not a raw asm block.
2975 if !raw && start == '{' {
2976 in_bracket = true;
2977 label_kind = AsmLabelKind::FormatArg;
2978 } else if matches!(start, '0' | '1') {
2979 // Binary labels have only the characters `0` or `1`.
2980 label_kind = AsmLabelKind::Binary;
2981 } else if !(start.is_ascii_alphabetic() || matches!(start, '.' | '_')) {
2982 // Named labels start with ASCII letters, `.` or `_`.
2983 // anything else is not a label
2984 break 'label_loop;
2985 }
2986
2987 for c in chars {
2988 // Inside a template format arg, any character is permitted for the
2989 // puproses of label detection because we assume that it can be
2990 // replaced with some other valid label string later. `options(raw)`
2991 // asm blocks cannot have format args, so they are excluded from this
2992 // special case.
2993 if !raw && in_bracket {
2994 if c == '{' {
2995 // Nested brackets are not allowed in format args, this cannot
2996 // be a label.
2997 break 'label_loop;
2998 }
2999
3000 if c == '}' {
3001 // The end of the format arg.
3002 in_bracket = false;
3003 }
3004 } else if !raw && c == '{' {
3005 // Start of a format arg.
3006 in_bracket = true;
3007 label_kind = AsmLabelKind::FormatArg;
3008 } else {
3009 let can_continue = match label_kind {
3010 // Format arg labels are considered to be named labels for the purposes
3011 // of continuing outside of their {} pair.
3012 AsmLabelKind::Named | AsmLabelKind::FormatArg => {
3013 c.is_ascii_alphanumeric() || matches!(c, '_' | '$')
3014 }
3015 AsmLabelKind::Binary => matches!(c, '0' | '1'),
3016 };
3017
3018 if !can_continue {
3019 // The potential label had an invalid character inside it, it
3020 // cannot be a label.
3021 break 'label_loop;
3022 }
3023 }
3024 }
3025
3026 // If all characters passed the label checks, this is a label.
3027 spans.push((find_label_span(possible_label), label_kind));
3028 start_idx = idx + 1;
3029 }
3030 }
3031
3032 for (span, label_kind) in spans {
3033 let missing_precise_span = span.is_none();
3034 let span = span.unwrap_or(*template_span);
3035 match label_kind {
3036 AsmLabelKind::Named => {
3037 cx.emit_span_lint(
3038 NAMED_ASM_LABELS,
3039 span,
3040 InvalidAsmLabel::Named { missing_precise_span },
3041 );
3042 }
3043 AsmLabelKind::FormatArg => {
3044 cx.emit_span_lint(
3045 NAMED_ASM_LABELS,
3046 span,
3047 InvalidAsmLabel::FormatArg { missing_precise_span },
3048 );
3049 }
3050 // the binary asm issue only occurs when using intel syntax on x86 targets
3051 AsmLabelKind::Binary
3052 if !options.contains(InlineAsmOptions::ATT_SYNTAX)
3053 && matches!(
3054 cx.tcx.sess.asm_arch,
3055 Some(InlineAsmArch::X86 | InlineAsmArch::X86_64) | None
3056 ) =>
3057 {
3058 cx.emit_span_lint(
3059 BINARY_ASM_LABELS,
3060 span,
3061 InvalidAsmLabel::Binary { missing_precise_span, span },
3062 )
3063 }
3064 // No lint on anything other than x86
3065 AsmLabelKind::Binary => (),
3066 };
3067 }
3068 }
3069 }
3070 }
3071}
3072
3073declare_lint! {
3074 /// The `special_module_name` lint detects module
3075 /// declarations for files that have a special meaning.
3076 ///
3077 /// ### Example
3078 ///
3079 /// ```rust,compile_fail
3080 /// mod lib;
3081 ///
3082 /// fn main() {
3083 /// lib::run();
3084 /// }
3085 /// ```
3086 ///
3087 /// {{produces}}
3088 ///
3089 /// ### Explanation
3090 ///
3091 /// Cargo recognizes `lib.rs` and `main.rs` as the root of a
3092 /// library or binary crate, so declaring them as modules
3093 /// will lead to miscompilation of the crate unless configured
3094 /// explicitly.
3095 ///
3096 /// To access a library from a binary target within the same crate,
3097 /// use `your_crate_name::` as the path instead of `lib::`:
3098 ///
3099 /// ```rust,compile_fail
3100 /// // bar/src/lib.rs
3101 /// fn run() {
3102 /// // ...
3103 /// }
3104 ///
3105 /// // bar/src/main.rs
3106 /// fn main() {
3107 /// bar::run();
3108 /// }
3109 /// ```
3110 ///
3111 /// Binary targets cannot be used as libraries and so declaring
3112 /// one as a module is not allowed.
3113 pub SPECIAL_MODULE_NAME,
3114 Warn,
3115 "module declarations for files with a special meaning",
3116}
3117
3118declare_lint_pass!(SpecialModuleName => [SPECIAL_MODULE_NAME]);
3119
3120impl EarlyLintPass for SpecialModuleName {
3121 fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
3122 for item in &krate.items {
3123 if let ast::ItemKind::Mod(
3124 _,
3125 ident,
3126 ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _, _),
3127 ) = item.kind
3128 {
3129 if item.attrs.iter().any(|a| a.has_name(sym::path)) {
3130 continue;
3131 }
3132
3133 match ident.name.as_str() {
3134 "lib" => cx.emit_span_lint(
3135 SPECIAL_MODULE_NAME,
3136 item.span,
3137 BuiltinSpecialModuleNameUsed::Lib,
3138 ),
3139 "main" => cx.emit_span_lint(
3140 SPECIAL_MODULE_NAME,
3141 item.span,
3142 BuiltinSpecialModuleNameUsed::Main,
3143 ),
3144 _ => continue,
3145 }
3146 }
3147 }
3148 }
3149}