1 //! Lints in the Rust compiler.
2 //!
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main compiler.
6 //!
7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
8 //! Then add code to emit the new lint in the appropriate circumstances.
9 //! You can do that in an existing `LintPass` if it makes sense, or in a
10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
11 //! compiler. Only do the latter if the check can't be written cleanly as a
12 //! `LintPass` (also, note that such lints will need to be defined in
13 //! `rustc_session::lint::builtin`, not here).
14 //!
15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
18 //! with a `pub fn new()`.
19 //!
20 //! If you define a new `LateLintPass`, you will also need to add it to the
21 //! `late_lint_methods!` invocation in `lib.rs`.
22
23 use crate::fluent_generated as fluent;
24 use crate::{
25 errors::BuiltinEllipsisInclusiveRangePatterns,
26 lints::{
27 BuiltinAnonymousParams, BuiltinBoxPointers, BuiltinClashingExtern,
28 BuiltinClashingExternSub, BuiltinConstNoMangle, BuiltinDeprecatedAttrLink,
29 BuiltinDeprecatedAttrLinkSuggestion, BuiltinDeprecatedAttrUsed, BuiltinDerefNullptr,
30 BuiltinEllipsisInclusiveRangePatternsLint, BuiltinExplicitOutlives,
31 BuiltinExplicitOutlivesSuggestion, BuiltinIncompleteFeatures,
32 BuiltinIncompleteFeaturesHelp, BuiltinIncompleteFeaturesNote, BuiltinKeywordIdents,
33 BuiltinMissingCopyImpl, BuiltinMissingDebugImpl, BuiltinMissingDoc,
34 BuiltinMutablesTransmutes, BuiltinNoMangleGeneric, BuiltinNonShorthandFieldPatterns,
35 BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasGenericBounds,
36 BuiltinTypeAliasGenericBoundsSuggestion, BuiltinTypeAliasWhereClause,
37 BuiltinUnexpectedCliConfigName, BuiltinUnexpectedCliConfigValue,
38 BuiltinUngatedAsyncFnTrackCaller, BuiltinUnnameableTestItems, BuiltinUnpermittedTypeInit,
39 BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub, BuiltinUnsafe,
40 BuiltinUnstableFeatures, BuiltinUnusedDocComment, BuiltinUnusedDocCommentSub,
41 BuiltinWhileTrue, SuggestChangingAssocTypes,
42 },
43 types::{transparent_newtype_field, CItemKind},
44 EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
45 };
46 use hir::IsAsync;
47 use rustc_ast::attr;
48 use rustc_ast::tokenstream::{TokenStream, TokenTree};
49 use rustc_ast::visit::{FnCtxt, FnKind};
50 use rustc_ast::{self as ast, *};
51 use rustc_ast_pretty::pprust::{self, expr_to_string};
52 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
53 use rustc_data_structures::stack::ensure_sufficient_stack;
54 use rustc_errors::{Applicability, DecorateLint, MultiSpan};
55 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
56 use rustc_hir as hir;
57 use rustc_hir::def::{DefKind, Res};
58 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
59 use rustc_hir::intravisit::FnKind as HirFnKind;
60 use rustc_hir::{Body, FnDecl, ForeignItemKind, GenericParamKind, Node, PatKind, PredicateOrigin};
61 use rustc_middle::lint::in_external_macro;
62 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
63 use rustc_middle::ty::print::with_no_trimmed_paths;
64 use rustc_middle::ty::subst::GenericArgKind;
65 use rustc_middle::ty::TypeVisitableExt;
66 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, VariantDef};
67 use rustc_session::config::ExpectedValues;
68 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
69 use rustc_span::edition::Edition;
70 use rustc_span::source_map::Spanned;
71 use rustc_span::symbol::{kw, sym, Ident, Symbol};
72 use rustc_span::{BytePos, InnerSpan, Span};
73 use rustc_target::abi::{Abi, FIRST_VARIANT};
74 use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
75 use rustc_trait_selection::traits::{self, misc::type_allowed_to_implement_copy};
76
77 use crate::nonstandard_style::{method_context, MethodLateContext};
78
79 use std::fmt::Write;
80
81 // hardwired lints from librustc_middle
82 pub use rustc_session::lint::builtin::*;
83
84 declare_lint! {
85 /// The `while_true` lint detects `while true { }`.
86 ///
87 /// ### Example
88 ///
89 /// ```rust,no_run
90 /// while true {
91 ///
92 /// }
93 /// ```
94 ///
95 /// {{produces}}
96 ///
97 /// ### Explanation
98 ///
99 /// `while true` should be replaced with `loop`. A `loop` expression is
100 /// the preferred way to write an infinite loop because it more directly
101 /// expresses the intent of the loop.
102 WHILE_TRUE,
103 Warn,
104 "suggest using `loop { }` instead of `while true { }`"
105 }
106
107 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
108
109 /// Traverse through any amount of parenthesis and return the first non-parens expression.
pierce_parens(mut expr: &ast::Expr) -> &ast::Expr110 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
111 while let ast::ExprKind::Paren(sub) = &expr.kind {
112 expr = sub;
113 }
114 expr
115 }
116
117 impl EarlyLintPass for WhileTrue {
118 #[inline]
check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr)119 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
120 if let ast::ExprKind::While(cond, _, label) = &e.kind
121 && let ast::ExprKind::Lit(token_lit) = pierce_parens(cond).kind
122 && let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
123 && !cond.span.from_expansion()
124 {
125 let condition_span = e.span.with_hi(cond.span.hi());
126 let replace = format!(
127 "{}loop",
128 label.map_or_else(String::new, |label| format!(
129 "{}: ",
130 label.ident,
131 ))
132 );
133 cx.emit_spanned_lint(WHILE_TRUE, condition_span, BuiltinWhileTrue {
134 suggestion: condition_span,
135 replace,
136 });
137 }
138 }
139 }
140
141 declare_lint! {
142 /// The `box_pointers` lints use of the Box type.
143 ///
144 /// ### Example
145 ///
146 /// ```rust,compile_fail
147 /// #![deny(box_pointers)]
148 /// struct Foo {
149 /// x: Box<isize>,
150 /// }
151 /// ```
152 ///
153 /// {{produces}}
154 ///
155 /// ### Explanation
156 ///
157 /// This lint is mostly historical, and not particularly useful. `Box<T>`
158 /// used to be built into the language, and the only way to do heap
159 /// allocation. Today's Rust can call into other allocators, etc.
160 BOX_POINTERS,
161 Allow,
162 "use of owned (Box type) heap memory"
163 }
164
165 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
166
167 impl BoxPointers {
check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>)168 fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
169 for leaf in ty.walk() {
170 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() && leaf_ty.is_box() {
171 cx.emit_spanned_lint(BOX_POINTERS, span, BuiltinBoxPointers { ty });
172 }
173 }
174 }
175 }
176
177 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)178 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
179 match it.kind {
180 hir::ItemKind::Fn(..)
181 | hir::ItemKind::TyAlias(..)
182 | hir::ItemKind::Enum(..)
183 | hir::ItemKind::Struct(..)
184 | hir::ItemKind::Union(..) => {
185 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.owner_id).subst_identity())
186 }
187 _ => (),
188 }
189
190 // If it's a struct, we also have to check the fields' types
191 match it.kind {
192 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
193 for field in struct_def.fields() {
194 self.check_heap_type(
195 cx,
196 field.span,
197 cx.tcx.type_of(field.def_id).subst_identity(),
198 );
199 }
200 }
201 _ => (),
202 }
203 }
204
check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>)205 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
206 let ty = cx.typeck_results().node_type(e.hir_id);
207 self.check_heap_type(cx, e.span, ty);
208 }
209 }
210
211 declare_lint! {
212 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
213 /// instead of `Struct { x }` in a pattern.
214 ///
215 /// ### Example
216 ///
217 /// ```rust
218 /// struct Point {
219 /// x: i32,
220 /// y: i32,
221 /// }
222 ///
223 ///
224 /// fn main() {
225 /// let p = Point {
226 /// x: 5,
227 /// y: 5,
228 /// };
229 ///
230 /// match p {
231 /// Point { x: x, y: y } => (),
232 /// }
233 /// }
234 /// ```
235 ///
236 /// {{produces}}
237 ///
238 /// ### Explanation
239 ///
240 /// The preferred style is to avoid the repetition of specifying both the
241 /// field name and the binding name if both identifiers are the same.
242 NON_SHORTHAND_FIELD_PATTERNS,
243 Warn,
244 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
245 }
246
247 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
248
249 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>)250 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
251 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
252 let variant = cx
253 .typeck_results()
254 .pat_ty(pat)
255 .ty_adt_def()
256 .expect("struct pattern type is not an ADT")
257 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
258 for fieldpat in field_pats {
259 if fieldpat.is_shorthand {
260 continue;
261 }
262 if fieldpat.span.from_expansion() {
263 // Don't lint if this is a macro expansion: macro authors
264 // shouldn't have to worry about this kind of style issue
265 // (Issue #49588)
266 continue;
267 }
268 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
269 if cx.tcx.find_field_index(ident, &variant)
270 == Some(cx.typeck_results().field_index(fieldpat.hir_id))
271 {
272 cx.emit_spanned_lint(
273 NON_SHORTHAND_FIELD_PATTERNS,
274 fieldpat.span,
275 BuiltinNonShorthandFieldPatterns {
276 ident,
277 suggestion: fieldpat.span,
278 prefix: binding_annot.prefix_str(),
279 },
280 );
281 }
282 }
283 }
284 }
285 }
286 }
287
288 declare_lint! {
289 /// The `unsafe_code` lint catches usage of `unsafe` code and other
290 /// potentially unsound constructs like `no_mangle`, `export_name`,
291 /// and `link_section`.
292 ///
293 /// ### Example
294 ///
295 /// ```rust,compile_fail
296 /// #![deny(unsafe_code)]
297 /// fn main() {
298 /// unsafe {
299 ///
300 /// }
301 /// }
302 ///
303 /// #[no_mangle]
304 /// fn func_0() { }
305 ///
306 /// #[export_name = "exported_symbol_name"]
307 /// pub fn name_in_rust() { }
308 ///
309 /// #[no_mangle]
310 /// #[link_section = ".example_section"]
311 /// pub static VAR1: u32 = 1;
312 /// ```
313 ///
314 /// {{produces}}
315 ///
316 /// ### Explanation
317 ///
318 /// This lint is intended to restrict the usage of `unsafe` blocks and other
319 /// constructs (including, but not limited to `no_mangle`, `link_section`
320 /// and `export_name` attributes) wrong usage of which causes undefined
321 /// behavior.
322 UNSAFE_CODE,
323 Allow,
324 "usage of `unsafe` code and other potentially unsound constructs"
325 }
326
327 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
328
329 impl UnsafeCode {
report_unsafe( &self, cx: &EarlyContext<'_>, span: Span, decorate: impl for<'a> DecorateLint<'a, ()>, )330 fn report_unsafe(
331 &self,
332 cx: &EarlyContext<'_>,
333 span: Span,
334 decorate: impl for<'a> DecorateLint<'a, ()>,
335 ) {
336 // This comes from a macro that has `#[allow_internal_unsafe]`.
337 if span.allows_unsafe() {
338 return;
339 }
340
341 cx.emit_spanned_lint(UNSAFE_CODE, span, decorate);
342 }
343 }
344
345 impl EarlyLintPass for UnsafeCode {
check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute)346 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
347 if attr.has_name(sym::allow_internal_unsafe) {
348 self.report_unsafe(cx, attr.span, BuiltinUnsafe::AllowInternalUnsafe);
349 }
350 }
351
352 #[inline]
check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr)353 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
354 if let ast::ExprKind::Block(ref blk, _) = e.kind {
355 // Don't warn about generated blocks; that'll just pollute the output.
356 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
357 self.report_unsafe(cx, blk.span, BuiltinUnsafe::UnsafeBlock);
358 }
359 }
360 }
361
check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item)362 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
363 match it.kind {
364 ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => {
365 self.report_unsafe(cx, it.span, BuiltinUnsafe::UnsafeTrait);
366 }
367
368 ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => {
369 self.report_unsafe(cx, it.span, BuiltinUnsafe::UnsafeImpl);
370 }
371
372 ast::ItemKind::Fn(..) => {
373 if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
374 self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleFn);
375 }
376
377 if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
378 self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameFn);
379 }
380
381 if let Some(attr) = attr::find_by_name(&it.attrs, sym::link_section) {
382 self.report_unsafe(cx, attr.span, BuiltinUnsafe::LinkSectionFn);
383 }
384 }
385
386 ast::ItemKind::Static(..) => {
387 if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
388 self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleStatic);
389 }
390
391 if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
392 self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameStatic);
393 }
394
395 if let Some(attr) = attr::find_by_name(&it.attrs, sym::link_section) {
396 self.report_unsafe(cx, attr.span, BuiltinUnsafe::LinkSectionStatic);
397 }
398 }
399
400 _ => {}
401 }
402 }
403
check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem)404 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
405 if let ast::AssocItemKind::Fn(..) = it.kind {
406 if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
407 self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleMethod);
408 }
409 if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
410 self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameMethod);
411 }
412 }
413 }
414
check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId)415 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
416 if let FnKind::Fn(
417 ctxt,
418 _,
419 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
420 _,
421 _,
422 body,
423 ) = fk
424 {
425 let decorator = match ctxt {
426 FnCtxt::Foreign => return,
427 FnCtxt::Free => BuiltinUnsafe::DeclUnsafeFn,
428 FnCtxt::Assoc(_) if body.is_none() => BuiltinUnsafe::DeclUnsafeMethod,
429 FnCtxt::Assoc(_) => BuiltinUnsafe::ImplUnsafeMethod,
430 };
431 self.report_unsafe(cx, span, decorator);
432 }
433 }
434 }
435
436 declare_lint! {
437 /// The `missing_docs` lint detects missing documentation for public items.
438 ///
439 /// ### Example
440 ///
441 /// ```rust,compile_fail
442 /// #![deny(missing_docs)]
443 /// pub fn foo() {}
444 /// ```
445 ///
446 /// {{produces}}
447 ///
448 /// ### Explanation
449 ///
450 /// This lint is intended to ensure that a library is well-documented.
451 /// Items without documentation can be difficult for users to understand
452 /// how to use properly.
453 ///
454 /// This lint is "allow" by default because it can be noisy, and not all
455 /// projects may want to enforce everything to be documented.
456 pub MISSING_DOCS,
457 Allow,
458 "detects missing documentation for public members",
459 report_in_external_macro
460 }
461
462 pub struct MissingDoc {
463 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
464 doc_hidden_stack: Vec<bool>,
465 }
466
467 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
468
has_doc(attr: &ast::Attribute) -> bool469 fn has_doc(attr: &ast::Attribute) -> bool {
470 if attr.is_doc_comment() {
471 return true;
472 }
473
474 if !attr.has_name(sym::doc) {
475 return false;
476 }
477
478 if attr.value_str().is_some() {
479 return true;
480 }
481
482 if let Some(list) = attr.meta_item_list() {
483 for meta in list {
484 if meta.has_name(sym::hidden) {
485 return true;
486 }
487 }
488 }
489
490 false
491 }
492
493 impl MissingDoc {
new() -> MissingDoc494 pub fn new() -> MissingDoc {
495 MissingDoc { doc_hidden_stack: vec![false] }
496 }
497
doc_hidden(&self) -> bool498 fn doc_hidden(&self) -> bool {
499 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
500 }
501
check_missing_docs_attrs( &self, cx: &LateContext<'_>, def_id: LocalDefId, article: &'static str, desc: &'static str, )502 fn check_missing_docs_attrs(
503 &self,
504 cx: &LateContext<'_>,
505 def_id: LocalDefId,
506 article: &'static str,
507 desc: &'static str,
508 ) {
509 // If we're building a test harness, then warning about
510 // documentation is probably not really relevant right now.
511 if cx.sess().opts.test {
512 return;
513 }
514
515 // `#[doc(hidden)]` disables missing_docs check.
516 if self.doc_hidden() {
517 return;
518 }
519
520 // Only check publicly-visible items, using the result from the privacy pass.
521 // It's an option so the crate root can also use this function (it doesn't
522 // have a `NodeId`).
523 if def_id != CRATE_DEF_ID {
524 if !cx.effective_visibilities.is_exported(def_id) {
525 return;
526 }
527 }
528
529 let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
530 let has_doc = attrs.iter().any(has_doc);
531 if !has_doc {
532 cx.emit_spanned_lint(
533 MISSING_DOCS,
534 cx.tcx.def_span(def_id),
535 BuiltinMissingDoc { article, desc },
536 );
537 }
538 }
539 }
540
541 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
542 #[inline]
enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute])543 fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
544 let doc_hidden = self.doc_hidden()
545 || attrs.iter().any(|attr| {
546 attr.has_name(sym::doc)
547 && match attr.meta_item_list() {
548 None => false,
549 Some(l) => attr::list_contains_name(&l, sym::hidden),
550 }
551 });
552 self.doc_hidden_stack.push(doc_hidden);
553 }
554
exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute])555 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
556 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
557 }
558
check_crate(&mut self, cx: &LateContext<'_>)559 fn check_crate(&mut self, cx: &LateContext<'_>) {
560 self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
561 }
562
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)563 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
564 // Previously the Impl and Use types have been excluded from missing docs,
565 // so we will continue to exclude them for compatibility.
566 //
567 // The documentation on `ExternCrate` is not used at the moment so no need to warn for it.
568 if let hir::ItemKind::Impl(..) | hir::ItemKind::Use(..) | hir::ItemKind::ExternCrate(_) =
569 it.kind
570 {
571 return;
572 }
573
574 let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
575 self.check_missing_docs_attrs(cx, it.owner_id.def_id, article, desc);
576 }
577
check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>)578 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
579 let (article, desc) = cx.tcx.article_and_description(trait_item.owner_id.to_def_id());
580
581 self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, article, desc);
582 }
583
check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>)584 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
585 let context = method_context(cx, impl_item.owner_id.def_id);
586
587 match context {
588 // If the method is an impl for a trait, don't doc.
589 MethodLateContext::TraitImpl => return,
590 MethodLateContext::TraitAutoImpl => {}
591 // If the method is an impl for an item with docs_hidden, don't doc.
592 MethodLateContext::PlainImpl => {
593 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
594 let impl_ty = cx.tcx.type_of(parent).subst_identity();
595 let outerdef = match impl_ty.kind() {
596 ty::Adt(def, _) => Some(def.did()),
597 ty::Foreign(def_id) => Some(*def_id),
598 _ => None,
599 };
600 let is_hidden = match outerdef {
601 Some(id) => cx.tcx.is_doc_hidden(id),
602 None => false,
603 };
604 if is_hidden {
605 return;
606 }
607 }
608 }
609
610 let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
611 self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);
612 }
613
check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>)614 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
615 let (article, desc) = cx.tcx.article_and_description(foreign_item.owner_id.to_def_id());
616 self.check_missing_docs_attrs(cx, foreign_item.owner_id.def_id, article, desc);
617 }
618
check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>)619 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
620 if !sf.is_positional() {
621 self.check_missing_docs_attrs(cx, sf.def_id, "a", "struct field")
622 }
623 }
624
check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>)625 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
626 self.check_missing_docs_attrs(cx, v.def_id, "a", "variant");
627 }
628 }
629
630 declare_lint! {
631 /// The `missing_copy_implementations` lint detects potentially-forgotten
632 /// implementations of [`Copy`] for public types.
633 ///
634 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
635 ///
636 /// ### Example
637 ///
638 /// ```rust,compile_fail
639 /// #![deny(missing_copy_implementations)]
640 /// pub struct Foo {
641 /// pub field: i32
642 /// }
643 /// # fn main() {}
644 /// ```
645 ///
646 /// {{produces}}
647 ///
648 /// ### Explanation
649 ///
650 /// Historically (before 1.0), types were automatically marked as `Copy`
651 /// if possible. This was changed so that it required an explicit opt-in
652 /// by implementing the `Copy` trait. As part of this change, a lint was
653 /// added to alert if a copyable type was not marked `Copy`.
654 ///
655 /// This lint is "allow" by default because this code isn't bad; it is
656 /// common to write newtypes like this specifically so that a `Copy` type
657 /// is no longer `Copy`. `Copy` types can result in unintended copies of
658 /// large data which can impact performance.
659 pub MISSING_COPY_IMPLEMENTATIONS,
660 Allow,
661 "detects potentially-forgotten implementations of `Copy`"
662 }
663
664 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
665
666 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)667 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
668 if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
669 return;
670 }
671 let (def, ty) = match item.kind {
672 hir::ItemKind::Struct(_, ref ast_generics) => {
673 if !ast_generics.params.is_empty() {
674 return;
675 }
676 let def = cx.tcx.adt_def(item.owner_id);
677 (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
678 }
679 hir::ItemKind::Union(_, ref ast_generics) => {
680 if !ast_generics.params.is_empty() {
681 return;
682 }
683 let def = cx.tcx.adt_def(item.owner_id);
684 (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
685 }
686 hir::ItemKind::Enum(_, ref ast_generics) => {
687 if !ast_generics.params.is_empty() {
688 return;
689 }
690 let def = cx.tcx.adt_def(item.owner_id);
691 (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
692 }
693 _ => return,
694 };
695 if def.has_dtor(cx.tcx) {
696 return;
697 }
698
699 // If the type contains a raw pointer, it may represent something like a handle,
700 // and recommending Copy might be a bad idea.
701 for field in def.all_fields() {
702 let did = field.did;
703 if cx.tcx.type_of(did).subst_identity().is_unsafe_ptr() {
704 return;
705 }
706 }
707 let param_env = ty::ParamEnv::empty();
708 if ty.is_copy_modulo_regions(cx.tcx, param_env) {
709 return;
710 }
711
712 // We shouldn't recommend implementing `Copy` on stateful things,
713 // such as iterators.
714 if let Some(iter_trait) = cx.tcx.get_diagnostic_item(sym::Iterator)
715 && cx.tcx
716 .infer_ctxt()
717 .build()
718 .type_implements_trait(iter_trait, [ty], param_env)
719 .must_apply_modulo_regions()
720 {
721 return;
722 }
723
724 // Default value of clippy::trivially_copy_pass_by_ref
725 const MAX_SIZE: u64 = 256;
726
727 if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes()) {
728 if size > MAX_SIZE {
729 return;
730 }
731 }
732
733 if type_allowed_to_implement_copy(
734 cx.tcx,
735 param_env,
736 ty,
737 traits::ObligationCause::misc(item.span, item.owner_id.def_id),
738 )
739 .is_ok()
740 {
741 cx.emit_spanned_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, BuiltinMissingCopyImpl);
742 }
743 }
744 }
745
746 declare_lint! {
747 /// The `missing_debug_implementations` lint detects missing
748 /// implementations of [`fmt::Debug`] for public types.
749 ///
750 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
751 ///
752 /// ### Example
753 ///
754 /// ```rust,compile_fail
755 /// #![deny(missing_debug_implementations)]
756 /// pub struct Foo;
757 /// # fn main() {}
758 /// ```
759 ///
760 /// {{produces}}
761 ///
762 /// ### Explanation
763 ///
764 /// Having a `Debug` implementation on all types can assist with
765 /// debugging, as it provides a convenient way to format and display a
766 /// value. Using the `#[derive(Debug)]` attribute will automatically
767 /// generate a typical implementation, or a custom implementation can be
768 /// added by manually implementing the `Debug` trait.
769 ///
770 /// This lint is "allow" by default because adding `Debug` to all types can
771 /// have a negative impact on compile time and code size. It also requires
772 /// boilerplate to be added to every type, which can be an impediment.
773 MISSING_DEBUG_IMPLEMENTATIONS,
774 Allow,
775 "detects missing implementations of Debug"
776 }
777
778 #[derive(Default)]
779 pub struct MissingDebugImplementations {
780 impling_types: Option<LocalDefIdSet>,
781 }
782
783 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
784
785 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)786 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
787 if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
788 return;
789 }
790
791 match item.kind {
792 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
793 _ => return,
794 }
795
796 let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
797 return
798 };
799
800 if self.impling_types.is_none() {
801 let mut impls = LocalDefIdSet::default();
802 cx.tcx.for_each_impl(debug, |d| {
803 if let Some(ty_def) = cx.tcx.type_of(d).subst_identity().ty_adt_def() {
804 if let Some(def_id) = ty_def.did().as_local() {
805 impls.insert(def_id);
806 }
807 }
808 });
809
810 self.impling_types = Some(impls);
811 debug!("{:?}", self.impling_types);
812 }
813
814 if !self.impling_types.as_ref().unwrap().contains(&item.owner_id.def_id) {
815 cx.emit_spanned_lint(
816 MISSING_DEBUG_IMPLEMENTATIONS,
817 item.span,
818 BuiltinMissingDebugImpl { tcx: cx.tcx, def_id: debug },
819 );
820 }
821 }
822 }
823
824 declare_lint! {
825 /// The `anonymous_parameters` lint detects anonymous parameters in trait
826 /// definitions.
827 ///
828 /// ### Example
829 ///
830 /// ```rust,edition2015,compile_fail
831 /// #![deny(anonymous_parameters)]
832 /// // edition 2015
833 /// pub trait Foo {
834 /// fn foo(usize);
835 /// }
836 /// fn main() {}
837 /// ```
838 ///
839 /// {{produces}}
840 ///
841 /// ### Explanation
842 ///
843 /// This syntax is mostly a historical accident, and can be worked around
844 /// quite easily by adding an `_` pattern or a descriptive identifier:
845 ///
846 /// ```rust
847 /// trait Foo {
848 /// fn foo(_: usize);
849 /// }
850 /// ```
851 ///
852 /// This syntax is now a hard error in the 2018 edition. In the 2015
853 /// edition, this lint is "warn" by default. This lint
854 /// enables the [`cargo fix`] tool with the `--edition` flag to
855 /// automatically transition old code from the 2015 edition to 2018. The
856 /// tool will run this lint and automatically apply the
857 /// suggested fix from the compiler (which is to add `_` to each
858 /// parameter). This provides a completely automated way to update old
859 /// code for a new edition. See [issue #41686] for more details.
860 ///
861 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
862 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
863 pub ANONYMOUS_PARAMETERS,
864 Warn,
865 "detects anonymous parameters",
866 @future_incompatible = FutureIncompatibleInfo {
867 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
868 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
869 };
870 }
871
872 declare_lint_pass!(
873 /// Checks for use of anonymous parameters (RFC 1685).
874 AnonymousParameters => [ANONYMOUS_PARAMETERS]
875 );
876
877 impl EarlyLintPass for AnonymousParameters {
check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem)878 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
879 if cx.sess().edition() != Edition::Edition2015 {
880 // This is a hard error in future editions; avoid linting and erroring
881 return;
882 }
883 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
884 for arg in sig.decl.inputs.iter() {
885 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
886 if ident.name == kw::Empty {
887 let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
888
889 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
890 (snip.as_str(), Applicability::MachineApplicable)
891 } else {
892 ("<type>", Applicability::HasPlaceholders)
893 };
894 cx.emit_spanned_lint(
895 ANONYMOUS_PARAMETERS,
896 arg.pat.span,
897 BuiltinAnonymousParams { suggestion: (arg.pat.span, appl), ty_snip },
898 );
899 }
900 }
901 }
902 }
903 }
904 }
905
906 /// Check for use of attributes which have been deprecated.
907 #[derive(Clone)]
908 pub struct DeprecatedAttr {
909 // This is not free to compute, so we want to keep it around, rather than
910 // compute it for every attribute.
911 depr_attrs: Vec<&'static BuiltinAttribute>,
912 }
913
914 impl_lint_pass!(DeprecatedAttr => []);
915
916 impl DeprecatedAttr {
new() -> DeprecatedAttr917 pub fn new() -> DeprecatedAttr {
918 DeprecatedAttr { depr_attrs: deprecated_attributes() }
919 }
920 }
921
922 impl EarlyLintPass for DeprecatedAttr {
check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute)923 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
924 for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
925 if attr.ident().map(|ident| ident.name) == Some(*name) {
926 if let &AttributeGate::Gated(
927 Stability::Deprecated(link, suggestion),
928 name,
929 reason,
930 _,
931 ) = gate
932 {
933 let suggestion = match suggestion {
934 Some(msg) => {
935 BuiltinDeprecatedAttrLinkSuggestion::Msg { suggestion: attr.span, msg }
936 }
937 None => {
938 BuiltinDeprecatedAttrLinkSuggestion::Default { suggestion: attr.span }
939 }
940 };
941 cx.emit_spanned_lint(
942 DEPRECATED,
943 attr.span,
944 BuiltinDeprecatedAttrLink { name, reason, link, suggestion },
945 );
946 }
947 return;
948 }
949 }
950 if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
951 cx.emit_spanned_lint(
952 DEPRECATED,
953 attr.span,
954 BuiltinDeprecatedAttrUsed {
955 name: pprust::path_to_string(&attr.get_normal_item().path),
956 suggestion: attr.span,
957 },
958 );
959 }
960 }
961 }
962
warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute])963 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
964 use rustc_ast::token::CommentKind;
965
966 let mut attrs = attrs.iter().peekable();
967
968 // Accumulate a single span for sugared doc comments.
969 let mut sugared_span: Option<Span> = None;
970
971 while let Some(attr) = attrs.next() {
972 let is_doc_comment = attr.is_doc_comment();
973 if is_doc_comment {
974 sugared_span =
975 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
976 }
977
978 if attrs.peek().is_some_and(|next_attr| next_attr.is_doc_comment()) {
979 continue;
980 }
981
982 let span = sugared_span.take().unwrap_or(attr.span);
983
984 if is_doc_comment || attr.has_name(sym::doc) {
985 let sub = match attr.kind {
986 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
987 BuiltinUnusedDocCommentSub::PlainHelp
988 }
989 AttrKind::DocComment(CommentKind::Block, _) => {
990 BuiltinUnusedDocCommentSub::BlockHelp
991 }
992 };
993 cx.emit_spanned_lint(
994 UNUSED_DOC_COMMENTS,
995 span,
996 BuiltinUnusedDocComment { kind: node_kind, label: node_span, sub },
997 );
998 }
999 }
1000 }
1001
1002 impl EarlyLintPass for UnusedDocComment {
check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt)1003 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1004 let kind = match stmt.kind {
1005 ast::StmtKind::Local(..) => "statements",
1006 // Disabled pending discussion in #78306
1007 ast::StmtKind::Item(..) => return,
1008 // expressions will be reported by `check_expr`.
1009 ast::StmtKind::Empty
1010 | ast::StmtKind::Semi(_)
1011 | ast::StmtKind::Expr(_)
1012 | ast::StmtKind::MacCall(_) => return,
1013 };
1014
1015 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1016 }
1017
check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm)1018 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1019 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1020 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1021 }
1022
check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr)1023 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1024 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1025 }
1026
check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam)1027 fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
1028 warn_if_doc(cx, param.ident.span, "generic parameters", ¶m.attrs);
1029 }
1030
check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block)1031 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
1032 warn_if_doc(cx, block.span, "blocks", &block.attrs());
1033 }
1034
check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item)1035 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
1036 if let ast::ItemKind::ForeignMod(_) = item.kind {
1037 warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
1038 }
1039 }
1040 }
1041
1042 declare_lint! {
1043 /// The `no_mangle_const_items` lint detects any `const` items with the
1044 /// [`no_mangle` attribute].
1045 ///
1046 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1047 ///
1048 /// ### Example
1049 ///
1050 /// ```rust,compile_fail
1051 /// #[no_mangle]
1052 /// const FOO: i32 = 5;
1053 /// ```
1054 ///
1055 /// {{produces}}
1056 ///
1057 /// ### Explanation
1058 ///
1059 /// Constants do not have their symbols exported, and therefore, this
1060 /// probably means you meant to use a [`static`], not a [`const`].
1061 ///
1062 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1063 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1064 NO_MANGLE_CONST_ITEMS,
1065 Deny,
1066 "const items will not have their symbols exported"
1067 }
1068
1069 declare_lint! {
1070 /// The `no_mangle_generic_items` lint detects generic items that must be
1071 /// mangled.
1072 ///
1073 /// ### Example
1074 ///
1075 /// ```rust
1076 /// #[no_mangle]
1077 /// fn foo<T>(t: T) {
1078 ///
1079 /// }
1080 /// ```
1081 ///
1082 /// {{produces}}
1083 ///
1084 /// ### Explanation
1085 ///
1086 /// A function with generics must have its symbol mangled to accommodate
1087 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1088 /// this situation, and should be removed.
1089 ///
1090 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1091 NO_MANGLE_GENERIC_ITEMS,
1092 Warn,
1093 "generic items must be mangled"
1094 }
1095
1096 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1097
1098 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)1099 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1100 let attrs = cx.tcx.hir().attrs(it.hir_id());
1101 let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1102 impl_generics: Option<&hir::Generics<'_>>,
1103 generics: &hir::Generics<'_>,
1104 span| {
1105 for param in
1106 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1107 {
1108 match param.kind {
1109 GenericParamKind::Lifetime { .. } => {}
1110 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1111 cx.emit_spanned_lint(
1112 NO_MANGLE_GENERIC_ITEMS,
1113 span,
1114 BuiltinNoMangleGeneric { suggestion: no_mangle_attr.span },
1115 );
1116 break;
1117 }
1118 }
1119 }
1120 };
1121 match it.kind {
1122 hir::ItemKind::Fn(.., ref generics, _) => {
1123 if let Some(no_mangle_attr) = attr::find_by_name(attrs, sym::no_mangle) {
1124 check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1125 }
1126 }
1127 hir::ItemKind::Const(..) => {
1128 if attr::contains_name(attrs, sym::no_mangle) {
1129 // account for "pub const" (#45562)
1130 let start = cx
1131 .tcx
1132 .sess
1133 .source_map()
1134 .span_to_snippet(it.span)
1135 .map(|snippet| snippet.find("const").unwrap_or(0))
1136 .unwrap_or(0) as u32;
1137 // `const` is 5 chars
1138 let suggestion = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1139
1140 // Const items do not refer to a particular location in memory, and therefore
1141 // don't have anything to attach a symbol to
1142 cx.emit_spanned_lint(
1143 NO_MANGLE_CONST_ITEMS,
1144 it.span,
1145 BuiltinConstNoMangle { suggestion },
1146 );
1147 }
1148 }
1149 hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
1150 for it in *items {
1151 if let hir::AssocItemKind::Fn { .. } = it.kind {
1152 if let Some(no_mangle_attr) =
1153 attr::find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1154 {
1155 check_no_mangle_on_generic_fn(
1156 no_mangle_attr,
1157 Some(generics),
1158 cx.tcx.hir().get_generics(it.id.owner_id.def_id).unwrap(),
1159 it.span,
1160 );
1161 }
1162 }
1163 }
1164 }
1165 _ => {}
1166 }
1167 }
1168 }
1169
1170 declare_lint! {
1171 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1172 /// T` because it is [undefined behavior].
1173 ///
1174 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1175 ///
1176 /// ### Example
1177 ///
1178 /// ```rust,compile_fail
1179 /// unsafe {
1180 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1181 /// }
1182 /// ```
1183 ///
1184 /// {{produces}}
1185 ///
1186 /// ### Explanation
1187 ///
1188 /// Certain assumptions are made about aliasing of data, and this transmute
1189 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1190 ///
1191 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1192 MUTABLE_TRANSMUTES,
1193 Deny,
1194 "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
1195 }
1196
1197 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1198
1199 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>)1200 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1201 if let Some((&ty::Ref(_, _, from_mutbl), &ty::Ref(_, _, to_mutbl))) =
1202 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1203 {
1204 if from_mutbl < to_mutbl {
1205 cx.emit_spanned_lint(MUTABLE_TRANSMUTES, expr.span, BuiltinMutablesTransmutes);
1206 }
1207 }
1208
1209 fn get_transmute_from_to<'tcx>(
1210 cx: &LateContext<'tcx>,
1211 expr: &hir::Expr<'_>,
1212 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1213 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1214 cx.qpath_res(qpath, expr.hir_id)
1215 } else {
1216 return None;
1217 };
1218 if let Res::Def(DefKind::Fn, did) = def {
1219 if !def_id_is_transmute(cx, did) {
1220 return None;
1221 }
1222 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1223 let from = sig.inputs().skip_binder()[0];
1224 let to = sig.output().skip_binder();
1225 return Some((from, to));
1226 }
1227 None
1228 }
1229
1230 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1231 cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
1232 }
1233 }
1234 }
1235
1236 declare_lint! {
1237 /// The `unstable_features` is deprecated and should no longer be used.
1238 UNSTABLE_FEATURES,
1239 Allow,
1240 "enabling unstable features (deprecated. do not use)"
1241 }
1242
1243 declare_lint_pass!(
1244 /// Forbids using the `#[feature(...)]` attribute
1245 UnstableFeatures => [UNSTABLE_FEATURES]
1246 );
1247
1248 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute)1249 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1250 if attr.has_name(sym::feature) {
1251 if let Some(items) = attr.meta_item_list() {
1252 for item in items {
1253 cx.emit_spanned_lint(UNSTABLE_FEATURES, item.span(), BuiltinUnstableFeatures);
1254 }
1255 }
1256 }
1257 }
1258 }
1259
1260 declare_lint! {
1261 /// The `ungated_async_fn_track_caller` lint warns when the
1262 /// `#[track_caller]` attribute is used on an async function, method, or
1263 /// closure, without enabling the corresponding unstable feature flag.
1264 ///
1265 /// ### Example
1266 ///
1267 /// ```rust
1268 /// #[track_caller]
1269 /// async fn foo() {}
1270 /// ```
1271 ///
1272 /// {{produces}}
1273 ///
1274 /// ### Explanation
1275 ///
1276 /// The attribute must be used in conjunction with the
1277 /// [`closure_track_caller` feature flag]. Otherwise, the `#[track_caller]`
1278 /// annotation will function as a no-op.
1279 ///
1280 /// [`closure_track_caller` feature flag]: https://doc.rust-lang.org/beta/unstable-book/language-features/closure-track-caller.html
1281 UNGATED_ASYNC_FN_TRACK_CALLER,
1282 Warn,
1283 "enabling track_caller on an async fn is a no-op unless the closure_track_caller feature is enabled"
1284 }
1285
1286 declare_lint_pass!(
1287 /// Explains corresponding feature flag must be enabled for the `#[track_caller]` attribute to
1288 /// do anything
1289 UngatedAsyncFnTrackCaller => [UNGATED_ASYNC_FN_TRACK_CALLER]
1290 );
1291
1292 impl<'tcx> LateLintPass<'tcx> for UngatedAsyncFnTrackCaller {
check_fn( &mut self, cx: &LateContext<'_>, fn_kind: HirFnKind<'_>, _: &'tcx FnDecl<'_>, _: &'tcx Body<'_>, span: Span, def_id: LocalDefId, )1293 fn check_fn(
1294 &mut self,
1295 cx: &LateContext<'_>,
1296 fn_kind: HirFnKind<'_>,
1297 _: &'tcx FnDecl<'_>,
1298 _: &'tcx Body<'_>,
1299 span: Span,
1300 def_id: LocalDefId,
1301 ) {
1302 if fn_kind.asyncness() == IsAsync::Async
1303 && !cx.tcx.features().closure_track_caller
1304 // Now, check if the function has the `#[track_caller]` attribute
1305 && let Some(attr) = cx.tcx.get_attr(def_id, sym::track_caller)
1306 {
1307 cx.emit_spanned_lint(UNGATED_ASYNC_FN_TRACK_CALLER, attr.span, BuiltinUngatedAsyncFnTrackCaller {
1308 label: span,
1309 parse_sess: &cx.tcx.sess.parse_sess,
1310 });
1311 }
1312 }
1313 }
1314
1315 declare_lint! {
1316 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1317 /// the crate root.
1318 ///
1319 /// ### Example
1320 ///
1321 /// ```rust,compile_fail
1322 /// #![deny(unreachable_pub)]
1323 /// mod foo {
1324 /// pub mod bar {
1325 ///
1326 /// }
1327 /// }
1328 /// ```
1329 ///
1330 /// {{produces}}
1331 ///
1332 /// ### Explanation
1333 ///
1334 /// The `pub` keyword both expresses an intent for an item to be publicly available, and also
1335 /// signals to the compiler to make the item publicly accessible. The intent can only be
1336 /// satisfied, however, if all items which contain this item are *also* publicly accessible.
1337 /// Thus, this lint serves to identify situations where the intent does not match the reality.
1338 ///
1339 /// If you wish the item to be accessible elsewhere within the crate, but not outside it, the
1340 /// `pub(crate)` visibility is recommended to be used instead. This more clearly expresses the
1341 /// intent that the item is only visible within its own crate.
1342 ///
1343 /// This lint is "allow" by default because it will trigger for a large
1344 /// amount existing Rust code, and has some false-positives. Eventually it
1345 /// is desired for this to become warn-by-default.
1346 pub UNREACHABLE_PUB,
1347 Allow,
1348 "`pub` items not reachable from crate root"
1349 }
1350
1351 declare_lint_pass!(
1352 /// Lint for items marked `pub` that aren't reachable from other crates.
1353 UnreachablePub => [UNREACHABLE_PUB]
1354 );
1355
1356 impl UnreachablePub {
perform_lint( &self, cx: &LateContext<'_>, what: &str, def_id: LocalDefId, vis_span: Span, exportable: bool, )1357 fn perform_lint(
1358 &self,
1359 cx: &LateContext<'_>,
1360 what: &str,
1361 def_id: LocalDefId,
1362 vis_span: Span,
1363 exportable: bool,
1364 ) {
1365 let mut applicability = Applicability::MachineApplicable;
1366 if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
1367 {
1368 if vis_span.from_expansion() {
1369 applicability = Applicability::MaybeIncorrect;
1370 }
1371 let def_span = cx.tcx.def_span(def_id);
1372 cx.emit_spanned_lint(
1373 UNREACHABLE_PUB,
1374 def_span,
1375 BuiltinUnreachablePub {
1376 what,
1377 suggestion: (vis_span, applicability),
1378 help: exportable.then_some(()),
1379 },
1380 );
1381 }
1382 }
1383 }
1384
1385 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)1386 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1387 // Do not warn for fake `use` statements.
1388 if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
1389 return;
1390 }
1391 self.perform_lint(cx, "item", item.owner_id.def_id, item.vis_span, true);
1392 }
1393
check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>)1394 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1395 self.perform_lint(cx, "item", foreign_item.owner_id.def_id, foreign_item.vis_span, true);
1396 }
1397
check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>)1398 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1399 let map = cx.tcx.hir();
1400 if matches!(map.get_parent(field.hir_id), Node::Variant(_)) {
1401 return;
1402 }
1403 self.perform_lint(cx, "field", field.def_id, field.vis_span, false);
1404 }
1405
check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>)1406 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1407 // Only lint inherent impl items.
1408 if cx.tcx.associated_item(impl_item.owner_id).trait_item_def_id.is_none() {
1409 self.perform_lint(cx, "item", impl_item.owner_id.def_id, impl_item.vis_span, false);
1410 }
1411 }
1412 }
1413
1414 declare_lint! {
1415 /// The `type_alias_bounds` lint detects bounds in type aliases.
1416 ///
1417 /// ### Example
1418 ///
1419 /// ```rust
1420 /// type SendVec<T: Send> = Vec<T>;
1421 /// ```
1422 ///
1423 /// {{produces}}
1424 ///
1425 /// ### Explanation
1426 ///
1427 /// The trait bounds in a type alias are currently ignored, and should not
1428 /// be included to avoid confusion. This was previously allowed
1429 /// unintentionally; this may become a hard error in the future.
1430 TYPE_ALIAS_BOUNDS,
1431 Warn,
1432 "bounds in type aliases are not enforced"
1433 }
1434
1435 declare_lint_pass!(
1436 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1437 /// They are relevant when using associated types, but otherwise neither checked
1438 /// at definition site nor enforced at use site.
1439 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1440 );
1441
1442 impl TypeAliasBounds {
is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool1443 pub(crate) fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1444 match *qpath {
1445 hir::QPath::TypeRelative(ref ty, _) => {
1446 // If this is a type variable, we found a `T::Assoc`.
1447 match ty.kind {
1448 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1449 matches!(path.res, Res::Def(DefKind::TyParam, _))
1450 }
1451 _ => false,
1452 }
1453 }
1454 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1455 }
1456 }
1457 }
1458
1459 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)1460 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1461 let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
1462 return
1463 };
1464 if cx.tcx.type_of(item.owner_id.def_id).skip_binder().has_opaque_types() {
1465 // Bounds are respected for `type X = impl Trait` and `type X = (impl Trait, Y);`
1466 return;
1467 }
1468 if cx.tcx.type_of(item.owner_id).skip_binder().has_inherent_projections() {
1469 // Bounds are respected for `type X = … Type::Inherent …`
1470 return;
1471 }
1472 // There must not be a where clause
1473 if type_alias_generics.predicates.is_empty() {
1474 return;
1475 }
1476
1477 let mut where_spans = Vec::new();
1478 let mut inline_spans = Vec::new();
1479 let mut inline_sugg = Vec::new();
1480 for p in type_alias_generics.predicates {
1481 let span = p.span();
1482 if p.in_where_clause() {
1483 where_spans.push(span);
1484 } else {
1485 for b in p.bounds() {
1486 inline_spans.push(b.span());
1487 }
1488 inline_sugg.push((span, String::new()));
1489 }
1490 }
1491
1492 let mut suggested_changing_assoc_types = false;
1493 if !where_spans.is_empty() {
1494 let sub = (!suggested_changing_assoc_types).then(|| {
1495 suggested_changing_assoc_types = true;
1496 SuggestChangingAssocTypes { ty }
1497 });
1498 cx.emit_spanned_lint(
1499 TYPE_ALIAS_BOUNDS,
1500 where_spans,
1501 BuiltinTypeAliasWhereClause {
1502 suggestion: type_alias_generics.where_clause_span,
1503 sub,
1504 },
1505 );
1506 }
1507
1508 if !inline_spans.is_empty() {
1509 let suggestion = BuiltinTypeAliasGenericBoundsSuggestion { suggestions: inline_sugg };
1510 let sub = (!suggested_changing_assoc_types).then(|| {
1511 suggested_changing_assoc_types = true;
1512 SuggestChangingAssocTypes { ty }
1513 });
1514 cx.emit_spanned_lint(
1515 TYPE_ALIAS_BOUNDS,
1516 inline_spans,
1517 BuiltinTypeAliasGenericBounds { suggestion, sub },
1518 );
1519 }
1520 }
1521 }
1522
1523 declare_lint_pass!(
1524 /// Lint constants that are erroneous.
1525 /// Without this lint, we might not get any diagnostic if the constant is
1526 /// unused within this crate, even though downstream crates can't use it
1527 /// without producing an error.
1528 UnusedBrokenConst => []
1529 );
1530
1531 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)1532 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1533 match it.kind {
1534 hir::ItemKind::Const(_, body_id) => {
1535 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1536 // trigger the query once for all constants since that will already report the errors
1537 cx.tcx.ensure().const_eval_poly(def_id);
1538 }
1539 hir::ItemKind::Static(_, _, body_id) => {
1540 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1541 cx.tcx.ensure().eval_static_initializer(def_id);
1542 }
1543 _ => {}
1544 }
1545 }
1546 }
1547
1548 declare_lint! {
1549 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1550 /// any type parameters.
1551 ///
1552 /// ### Example
1553 ///
1554 /// ```rust
1555 /// #![feature(trivial_bounds)]
1556 /// pub struct A where i32: Copy;
1557 /// ```
1558 ///
1559 /// {{produces}}
1560 ///
1561 /// ### Explanation
1562 ///
1563 /// Usually you would not write a trait bound that you know is always
1564 /// true, or never true. However, when using macros, the macro may not
1565 /// know whether or not the constraint would hold or not at the time when
1566 /// generating the code. Currently, the compiler does not alert you if the
1567 /// constraint is always true, and generates an error if it is never true.
1568 /// The `trivial_bounds` feature changes this to be a warning in both
1569 /// cases, giving macros more freedom and flexibility to generate code,
1570 /// while still providing a signal when writing non-macro code that
1571 /// something is amiss.
1572 ///
1573 /// See [RFC 2056] for more details. This feature is currently only
1574 /// available on the nightly channel, see [tracking issue #48214].
1575 ///
1576 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1577 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1578 TRIVIAL_BOUNDS,
1579 Warn,
1580 "these bounds don't depend on an type parameters"
1581 }
1582
1583 declare_lint_pass!(
1584 /// Lint for trait and lifetime bounds that don't depend on type parameters
1585 /// which either do nothing, or stop the item from being used.
1586 TrivialConstraints => [TRIVIAL_BOUNDS]
1587 );
1588
1589 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>)1590 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1591 use rustc_middle::ty::ClauseKind;
1592
1593 if cx.tcx.features().trivial_bounds {
1594 let predicates = cx.tcx.predicates_of(item.owner_id);
1595 for &(predicate, span) in predicates.predicates {
1596 let predicate_kind_name = match predicate.kind().skip_binder() {
1597 ClauseKind::Trait(..) => "trait",
1598 ClauseKind::TypeOutlives(..) |
1599 ClauseKind::RegionOutlives(..) => "lifetime",
1600
1601 // `ConstArgHasType` is never global as `ct` is always a param
1602 ClauseKind::ConstArgHasType(..)
1603 // Ignore projections, as they can only be global
1604 // if the trait bound is global
1605 | ClauseKind::Projection(..)
1606 // Ignore bounds that a user can't type
1607 | ClauseKind::WellFormed(..)
1608 // FIXME(generic_const_exprs): `ConstEvaluatable` can be written
1609 | ClauseKind::ConstEvaluatable(..) => continue,
1610 };
1611 if predicate.is_global() {
1612 cx.emit_spanned_lint(
1613 TRIVIAL_BOUNDS,
1614 span,
1615 BuiltinTrivialBounds { predicate_kind_name, predicate },
1616 );
1617 }
1618 }
1619 }
1620 }
1621 }
1622
1623 declare_lint_pass!(
1624 /// Does nothing as a lint pass, but registers some `Lint`s
1625 /// which are used by other parts of the compiler.
1626 SoftLints => [
1627 WHILE_TRUE,
1628 BOX_POINTERS,
1629 NON_SHORTHAND_FIELD_PATTERNS,
1630 UNSAFE_CODE,
1631 MISSING_DOCS,
1632 MISSING_COPY_IMPLEMENTATIONS,
1633 MISSING_DEBUG_IMPLEMENTATIONS,
1634 ANONYMOUS_PARAMETERS,
1635 UNUSED_DOC_COMMENTS,
1636 NO_MANGLE_CONST_ITEMS,
1637 NO_MANGLE_GENERIC_ITEMS,
1638 MUTABLE_TRANSMUTES,
1639 UNSTABLE_FEATURES,
1640 UNREACHABLE_PUB,
1641 TYPE_ALIAS_BOUNDS,
1642 TRIVIAL_BOUNDS
1643 ]
1644 );
1645
1646 declare_lint! {
1647 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1648 /// pattern], which is deprecated.
1649 ///
1650 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1651 ///
1652 /// ### Example
1653 ///
1654 /// ```rust,edition2018
1655 /// let x = 123;
1656 /// match x {
1657 /// 0...100 => {}
1658 /// _ => {}
1659 /// }
1660 /// ```
1661 ///
1662 /// {{produces}}
1663 ///
1664 /// ### Explanation
1665 ///
1666 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1667 /// confusion with the [`..` range expression]. Use the new form instead.
1668 ///
1669 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1670 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1671 Warn,
1672 "`...` range patterns are deprecated",
1673 @future_incompatible = FutureIncompatibleInfo {
1674 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1675 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1676 };
1677 }
1678
1679 #[derive(Default)]
1680 pub struct EllipsisInclusiveRangePatterns {
1681 /// If `Some(_)`, suppress all subsequent pattern
1682 /// warnings for better diagnostics.
1683 node_id: Option<ast::NodeId>,
1684 }
1685
1686 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1687
1688 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat)1689 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1690 if self.node_id.is_some() {
1691 // Don't recursively warn about patterns inside range endpoints.
1692 return;
1693 }
1694
1695 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1696
1697 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1698 /// corresponding to the ellipsis.
1699 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1700 match &pat.kind {
1701 PatKind::Range(
1702 a,
1703 Some(b),
1704 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1705 ) => Some((a.as_deref(), b, *span)),
1706 _ => None,
1707 }
1708 }
1709
1710 let (parentheses, endpoints) = match &pat.kind {
1711 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1712 _ => (false, matches_ellipsis_pat(pat)),
1713 };
1714
1715 if let Some((start, end, join)) = endpoints {
1716 if parentheses {
1717 self.node_id = Some(pat.id);
1718 let end = expr_to_string(&end);
1719 let replace = match start {
1720 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1721 None => format!("&(..={})", end),
1722 };
1723 if join.edition() >= Edition::Edition2021 {
1724 cx.sess().emit_err(BuiltinEllipsisInclusiveRangePatterns {
1725 span: pat.span,
1726 suggestion: pat.span,
1727 replace,
1728 });
1729 } else {
1730 cx.emit_spanned_lint(
1731 ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1732 pat.span,
1733 BuiltinEllipsisInclusiveRangePatternsLint::Parenthesise {
1734 suggestion: pat.span,
1735 replace,
1736 },
1737 );
1738 }
1739 } else {
1740 let replace = "..=";
1741 if join.edition() >= Edition::Edition2021 {
1742 cx.sess().emit_err(BuiltinEllipsisInclusiveRangePatterns {
1743 span: pat.span,
1744 suggestion: join,
1745 replace: replace.to_string(),
1746 });
1747 } else {
1748 cx.emit_spanned_lint(
1749 ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1750 join,
1751 BuiltinEllipsisInclusiveRangePatternsLint::NonParenthesise {
1752 suggestion: join,
1753 },
1754 );
1755 }
1756 };
1757 }
1758 }
1759
check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat)1760 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1761 if let Some(node_id) = self.node_id {
1762 if pat.id == node_id {
1763 self.node_id = None
1764 }
1765 }
1766 }
1767 }
1768
1769 declare_lint! {
1770 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1771 /// that are not able to be run by the test harness because they are in a
1772 /// position where they are not nameable.
1773 ///
1774 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1775 ///
1776 /// ### Example
1777 ///
1778 /// ```rust,test
1779 /// fn main() {
1780 /// #[test]
1781 /// fn foo() {
1782 /// // This test will not fail because it does not run.
1783 /// assert_eq!(1, 2);
1784 /// }
1785 /// }
1786 /// ```
1787 ///
1788 /// {{produces}}
1789 ///
1790 /// ### Explanation
1791 ///
1792 /// In order for the test harness to run a test, the test function must be
1793 /// located in a position where it can be accessed from the crate root.
1794 /// This generally means it must be defined in a module, and not anywhere
1795 /// else such as inside another function. The compiler previously allowed
1796 /// this without an error, so a lint was added as an alert that a test is
1797 /// not being used. Whether or not this should be allowed has not yet been
1798 /// decided, see [RFC 2471] and [issue #36629].
1799 ///
1800 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1801 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1802 UNNAMEABLE_TEST_ITEMS,
1803 Warn,
1804 "detects an item that cannot be named being marked as `#[test_case]`",
1805 report_in_external_macro
1806 }
1807
1808 pub struct UnnameableTestItems {
1809 boundary: Option<hir::OwnerId>, // Id of the item under which things are not nameable
1810 items_nameable: bool,
1811 }
1812
1813 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1814
1815 impl UnnameableTestItems {
new() -> Self1816 pub fn new() -> Self {
1817 Self { boundary: None, items_nameable: true }
1818 }
1819 }
1820
1821 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)1822 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1823 if self.items_nameable {
1824 if let hir::ItemKind::Mod(..) = it.kind {
1825 } else {
1826 self.items_nameable = false;
1827 self.boundary = Some(it.owner_id);
1828 }
1829 return;
1830 }
1831
1832 let attrs = cx.tcx.hir().attrs(it.hir_id());
1833 if let Some(attr) = attr::find_by_name(attrs, sym::rustc_test_marker) {
1834 cx.emit_spanned_lint(UNNAMEABLE_TEST_ITEMS, attr.span, BuiltinUnnameableTestItems);
1835 }
1836 }
1837
check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>)1838 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1839 if !self.items_nameable && self.boundary == Some(it.owner_id) {
1840 self.items_nameable = true;
1841 }
1842 }
1843 }
1844
1845 declare_lint! {
1846 /// The `keyword_idents` lint detects edition keywords being used as an
1847 /// identifier.
1848 ///
1849 /// ### Example
1850 ///
1851 /// ```rust,edition2015,compile_fail
1852 /// #![deny(keyword_idents)]
1853 /// // edition 2015
1854 /// fn dyn() {}
1855 /// ```
1856 ///
1857 /// {{produces}}
1858 ///
1859 /// ### Explanation
1860 ///
1861 /// Rust [editions] allow the language to evolve without breaking
1862 /// backwards compatibility. This lint catches code that uses new keywords
1863 /// that are added to the language that are used as identifiers (such as a
1864 /// variable name, function name, etc.). If you switch the compiler to a
1865 /// new edition without updating the code, then it will fail to compile if
1866 /// you are using a new keyword as an identifier.
1867 ///
1868 /// You can manually change the identifiers to a non-keyword, or use a
1869 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1870 ///
1871 /// This lint solves the problem automatically. It is "allow" by default
1872 /// because the code is perfectly valid in older editions. The [`cargo
1873 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1874 /// and automatically apply the suggested fix from the compiler (which is
1875 /// to use a raw identifier). This provides a completely automated way to
1876 /// update old code for a new edition.
1877 ///
1878 /// [editions]: https://doc.rust-lang.org/edition-guide/
1879 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1880 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1881 pub KEYWORD_IDENTS,
1882 Allow,
1883 "detects edition keywords being used as an identifier",
1884 @future_incompatible = FutureIncompatibleInfo {
1885 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1886 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1887 };
1888 }
1889
1890 declare_lint_pass!(
1891 /// Check for uses of edition keywords used as an identifier.
1892 KeywordIdents => [KEYWORD_IDENTS]
1893 );
1894
1895 struct UnderMacro(bool);
1896
1897 impl KeywordIdents {
check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: &TokenStream)1898 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: &TokenStream) {
1899 for tt in tokens.trees() {
1900 match tt {
1901 // Only report non-raw idents.
1902 TokenTree::Token(token, _) => {
1903 if let Some((ident, false)) = token.ident() {
1904 self.check_ident_token(cx, UnderMacro(true), ident);
1905 }
1906 }
1907 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1908 }
1909 }
1910 }
1911
check_ident_token( &mut self, cx: &EarlyContext<'_>, UnderMacro(under_macro): UnderMacro, ident: Ident, )1912 fn check_ident_token(
1913 &mut self,
1914 cx: &EarlyContext<'_>,
1915 UnderMacro(under_macro): UnderMacro,
1916 ident: Ident,
1917 ) {
1918 let next_edition = match cx.sess().edition() {
1919 Edition::Edition2015 => {
1920 match ident.name {
1921 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1922
1923 // rust-lang/rust#56327: Conservatively do not
1924 // attempt to report occurrences of `dyn` within
1925 // macro definitions or invocations, because `dyn`
1926 // can legitimately occur as a contextual keyword
1927 // in 2015 code denoting its 2018 meaning, and we
1928 // do not want rustfix to inject bugs into working
1929 // code by rewriting such occurrences.
1930 //
1931 // But if we see `dyn` outside of a macro, we know
1932 // its precise role in the parsed AST and thus are
1933 // assured this is truly an attempt to use it as
1934 // an identifier.
1935 kw::Dyn if !under_macro => Edition::Edition2018,
1936
1937 _ => return,
1938 }
1939 }
1940
1941 // There are no new keywords yet for the 2018 edition and beyond.
1942 _ => return,
1943 };
1944
1945 // Don't lint `r#foo`.
1946 if cx.sess().parse_sess.raw_identifier_spans.contains(ident.span) {
1947 return;
1948 }
1949
1950 cx.emit_spanned_lint(
1951 KEYWORD_IDENTS,
1952 ident.span,
1953 BuiltinKeywordIdents { kw: ident, next: next_edition, suggestion: ident.span },
1954 );
1955 }
1956 }
1957
1958 impl EarlyLintPass for KeywordIdents {
check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef)1959 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
1960 self.check_tokens(cx, &mac_def.body.tokens);
1961 }
check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall)1962 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
1963 self.check_tokens(cx, &mac.args.tokens);
1964 }
check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident)1965 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
1966 self.check_ident_token(cx, UnderMacro(false), ident);
1967 }
1968 }
1969
1970 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
1971
1972 impl ExplicitOutlivesRequirements {
lifetimes_outliving_lifetime<'tcx>( inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)], def_id: DefId, ) -> Vec<ty::Region<'tcx>>1973 fn lifetimes_outliving_lifetime<'tcx>(
1974 inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
1975 def_id: DefId,
1976 ) -> Vec<ty::Region<'tcx>> {
1977 inferred_outlives
1978 .iter()
1979 .filter_map(|(clause, _)| match clause.kind().skip_binder() {
1980 ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
1981 ty::ReEarlyBound(ebr) if ebr.def_id == def_id => Some(b),
1982 _ => None,
1983 },
1984 _ => None,
1985 })
1986 .collect()
1987 }
1988
lifetimes_outliving_type<'tcx>( inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)], index: u32, ) -> Vec<ty::Region<'tcx>>1989 fn lifetimes_outliving_type<'tcx>(
1990 inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
1991 index: u32,
1992 ) -> Vec<ty::Region<'tcx>> {
1993 inferred_outlives
1994 .iter()
1995 .filter_map(|(clause, _)| match clause.kind().skip_binder() {
1996 ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
1997 a.is_param(index).then_some(b)
1998 }
1999 _ => None,
2000 })
2001 .collect()
2002 }
2003
collect_outlives_bound_spans<'tcx>( &self, tcx: TyCtxt<'tcx>, bounds: &hir::GenericBounds<'_>, inferred_outlives: &[ty::Region<'tcx>], predicate_span: Span, ) -> Vec<(usize, Span)>2004 fn collect_outlives_bound_spans<'tcx>(
2005 &self,
2006 tcx: TyCtxt<'tcx>,
2007 bounds: &hir::GenericBounds<'_>,
2008 inferred_outlives: &[ty::Region<'tcx>],
2009 predicate_span: Span,
2010 ) -> Vec<(usize, Span)> {
2011 use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
2012
2013 bounds
2014 .iter()
2015 .enumerate()
2016 .filter_map(|(i, bound)| {
2017 let hir::GenericBound::Outlives(lifetime) = bound else {
2018 return None;
2019 };
2020
2021 let is_inferred = match tcx.named_bound_var(lifetime.hir_id) {
2022 Some(ResolvedArg::EarlyBound(def_id)) => inferred_outlives
2023 .iter()
2024 .any(|r| matches!(**r, ty::ReEarlyBound(ebr) if { ebr.def_id == def_id })),
2025 _ => false,
2026 };
2027
2028 if !is_inferred {
2029 return None;
2030 }
2031
2032 let span = bound.span().find_ancestor_inside(predicate_span)?;
2033 if in_external_macro(tcx.sess, span) {
2034 return None;
2035 }
2036
2037 Some((i, span))
2038 })
2039 .collect()
2040 }
2041
consolidate_outlives_bound_spans( &self, lo: Span, bounds: &hir::GenericBounds<'_>, bound_spans: Vec<(usize, Span)>, ) -> Vec<Span>2042 fn consolidate_outlives_bound_spans(
2043 &self,
2044 lo: Span,
2045 bounds: &hir::GenericBounds<'_>,
2046 bound_spans: Vec<(usize, Span)>,
2047 ) -> Vec<Span> {
2048 if bounds.is_empty() {
2049 return Vec::new();
2050 }
2051 if bound_spans.len() == bounds.len() {
2052 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2053 // If all bounds are inferable, we want to delete the colon, so
2054 // start from just after the parameter (span passed as argument)
2055 vec![lo.to(last_bound_span)]
2056 } else {
2057 let mut merged = Vec::new();
2058 let mut last_merged_i = None;
2059
2060 let mut from_start = true;
2061 for (i, bound_span) in bound_spans {
2062 match last_merged_i {
2063 // If the first bound is inferable, our span should also eat the leading `+`.
2064 None if i == 0 => {
2065 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2066 last_merged_i = Some(0);
2067 }
2068 // If consecutive bounds are inferable, merge their spans
2069 Some(h) if i == h + 1 => {
2070 if let Some(tail) = merged.last_mut() {
2071 // Also eat the trailing `+` if the first
2072 // more-than-one bound is inferable
2073 let to_span = if from_start && i < bounds.len() {
2074 bounds[i + 1].span().shrink_to_lo()
2075 } else {
2076 bound_span
2077 };
2078 *tail = tail.to(to_span);
2079 last_merged_i = Some(i);
2080 } else {
2081 bug!("another bound-span visited earlier");
2082 }
2083 }
2084 _ => {
2085 // When we find a non-inferable bound, subsequent inferable bounds
2086 // won't be consecutive from the start (and we'll eat the leading
2087 // `+` rather than the trailing one)
2088 from_start = false;
2089 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2090 last_merged_i = Some(i);
2091 }
2092 }
2093 }
2094 merged
2095 }
2096 }
2097 }
2098
2099 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>)2100 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2101 use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
2102
2103 let def_id = item.owner_id.def_id;
2104 if let hir::ItemKind::Struct(_, hir_generics)
2105 | hir::ItemKind::Enum(_, hir_generics)
2106 | hir::ItemKind::Union(_, hir_generics) = item.kind
2107 {
2108 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2109 if inferred_outlives.is_empty() {
2110 return;
2111 }
2112
2113 let ty_generics = cx.tcx.generics_of(def_id);
2114 let num_where_predicates = hir_generics
2115 .predicates
2116 .iter()
2117 .filter(|predicate| predicate.in_where_clause())
2118 .count();
2119
2120 let mut bound_count = 0;
2121 let mut lint_spans = Vec::new();
2122 let mut where_lint_spans = Vec::new();
2123 let mut dropped_where_predicate_count = 0;
2124 for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
2125 let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
2126 match where_predicate {
2127 hir::WherePredicate::RegionPredicate(predicate) => {
2128 if let Some(ResolvedArg::EarlyBound(region_def_id)) =
2129 cx.tcx.named_bound_var(predicate.lifetime.hir_id)
2130 {
2131 (
2132 Self::lifetimes_outliving_lifetime(
2133 inferred_outlives,
2134 region_def_id,
2135 ),
2136 &predicate.bounds,
2137 predicate.span,
2138 predicate.in_where_clause,
2139 )
2140 } else {
2141 continue;
2142 }
2143 }
2144 hir::WherePredicate::BoundPredicate(predicate) => {
2145 // FIXME we can also infer bounds on associated types,
2146 // and should check for them here.
2147 match predicate.bounded_ty.kind {
2148 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => {
2149 let Res::Def(DefKind::TyParam, def_id) = path.res else {
2150 continue;
2151 };
2152 let index = ty_generics.param_def_id_to_index[&def_id];
2153 (
2154 Self::lifetimes_outliving_type(inferred_outlives, index),
2155 &predicate.bounds,
2156 predicate.span,
2157 predicate.origin == PredicateOrigin::WhereClause,
2158 )
2159 }
2160 _ => {
2161 continue;
2162 }
2163 }
2164 }
2165 _ => continue,
2166 };
2167 if relevant_lifetimes.is_empty() {
2168 continue;
2169 }
2170
2171 let bound_spans = self.collect_outlives_bound_spans(
2172 cx.tcx,
2173 bounds,
2174 &relevant_lifetimes,
2175 predicate_span,
2176 );
2177 bound_count += bound_spans.len();
2178
2179 let drop_predicate = bound_spans.len() == bounds.len();
2180 if drop_predicate && in_where_clause {
2181 dropped_where_predicate_count += 1;
2182 }
2183
2184 if drop_predicate {
2185 if !in_where_clause {
2186 lint_spans.push(predicate_span);
2187 } else if predicate_span.from_expansion() {
2188 // Don't try to extend the span if it comes from a macro expansion.
2189 where_lint_spans.push(predicate_span);
2190 } else if i + 1 < num_where_predicates {
2191 // If all the bounds on a predicate were inferable and there are
2192 // further predicates, we want to eat the trailing comma.
2193 let next_predicate_span = hir_generics.predicates[i + 1].span();
2194 if next_predicate_span.from_expansion() {
2195 where_lint_spans.push(predicate_span);
2196 } else {
2197 where_lint_spans
2198 .push(predicate_span.to(next_predicate_span.shrink_to_lo()));
2199 }
2200 } else {
2201 // Eat the optional trailing comma after the last predicate.
2202 let where_span = hir_generics.where_clause_span;
2203 if where_span.from_expansion() {
2204 where_lint_spans.push(predicate_span);
2205 } else {
2206 where_lint_spans.push(predicate_span.to(where_span.shrink_to_hi()));
2207 }
2208 }
2209 } else {
2210 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2211 predicate_span.shrink_to_lo(),
2212 bounds,
2213 bound_spans,
2214 ));
2215 }
2216 }
2217
2218 // If all predicates in where clause are inferable, drop the entire clause
2219 // (including the `where`)
2220 if hir_generics.has_where_clause_predicates
2221 && dropped_where_predicate_count == num_where_predicates
2222 {
2223 let where_span = hir_generics.where_clause_span;
2224 // Extend the where clause back to the closing `>` of the
2225 // generics, except for tuple struct, which have the `where`
2226 // after the fields of the struct.
2227 let full_where_span =
2228 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2229 where_span
2230 } else {
2231 hir_generics.span.shrink_to_hi().to(where_span)
2232 };
2233
2234 // Due to macro expansions, the `full_where_span` might not actually contain all predicates.
2235 if where_lint_spans.iter().all(|&sp| full_where_span.contains(sp)) {
2236 lint_spans.push(full_where_span);
2237 } else {
2238 lint_spans.extend(where_lint_spans);
2239 }
2240 } else {
2241 lint_spans.extend(where_lint_spans);
2242 }
2243
2244 if !lint_spans.is_empty() {
2245 // Do not automatically delete outlives requirements from macros.
2246 let applicability = if lint_spans.iter().all(|sp| sp.can_be_used_for_suggestions())
2247 {
2248 Applicability::MachineApplicable
2249 } else {
2250 Applicability::MaybeIncorrect
2251 };
2252
2253 // Due to macros, there might be several predicates with the same span
2254 // and we only want to suggest removing them once.
2255 lint_spans.sort_unstable();
2256 lint_spans.dedup();
2257
2258 cx.emit_spanned_lint(
2259 EXPLICIT_OUTLIVES_REQUIREMENTS,
2260 lint_spans.clone(),
2261 BuiltinExplicitOutlives {
2262 count: bound_count,
2263 suggestion: BuiltinExplicitOutlivesSuggestion {
2264 spans: lint_spans,
2265 applicability,
2266 },
2267 },
2268 );
2269 }
2270 }
2271 }
2272 }
2273
2274 declare_lint! {
2275 /// The `incomplete_features` lint detects unstable features enabled with
2276 /// the [`feature` attribute] that may function improperly in some or all
2277 /// cases.
2278 ///
2279 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2280 ///
2281 /// ### Example
2282 ///
2283 /// ```rust
2284 /// #![feature(generic_const_exprs)]
2285 /// ```
2286 ///
2287 /// {{produces}}
2288 ///
2289 /// ### Explanation
2290 ///
2291 /// Although it is encouraged for people to experiment with unstable
2292 /// features, some of them are known to be incomplete or faulty. This lint
2293 /// is a signal that the feature has not yet been finished, and you may
2294 /// experience problems with it.
2295 pub INCOMPLETE_FEATURES,
2296 Warn,
2297 "incomplete features that may function improperly in some or all cases"
2298 }
2299
2300 declare_lint_pass!(
2301 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2302 IncompleteFeatures => [INCOMPLETE_FEATURES]
2303 );
2304
2305 impl EarlyLintPass for IncompleteFeatures {
check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate)2306 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2307 let features = cx.sess().features_untracked();
2308 features
2309 .declared_lang_features
2310 .iter()
2311 .map(|(name, span, _)| (name, span))
2312 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2313 .filter(|(&name, _)| features.incomplete(name))
2314 .for_each(|(&name, &span)| {
2315 let note = rustc_feature::find_feature_issue(name, GateIssue::Language)
2316 .map(|n| BuiltinIncompleteFeaturesNote { n });
2317 let help =
2318 HAS_MIN_FEATURES.contains(&name).then_some(BuiltinIncompleteFeaturesHelp);
2319 cx.emit_spanned_lint(
2320 INCOMPLETE_FEATURES,
2321 span,
2322 BuiltinIncompleteFeatures { name, note, help },
2323 );
2324 });
2325 }
2326 }
2327
2328 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2329
2330 declare_lint! {
2331 /// The `invalid_value` lint detects creating a value that is not valid,
2332 /// such as a null reference.
2333 ///
2334 /// ### Example
2335 ///
2336 /// ```rust,no_run
2337 /// # #![allow(unused)]
2338 /// unsafe {
2339 /// let x: &'static i32 = std::mem::zeroed();
2340 /// }
2341 /// ```
2342 ///
2343 /// {{produces}}
2344 ///
2345 /// ### Explanation
2346 ///
2347 /// In some situations the compiler can detect that the code is creating
2348 /// an invalid value, which should be avoided.
2349 ///
2350 /// In particular, this lint will check for improper use of
2351 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2352 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2353 /// lint should provide extra information to indicate what the problem is
2354 /// and a possible solution.
2355 ///
2356 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2357 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2358 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2359 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2360 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2361 pub INVALID_VALUE,
2362 Warn,
2363 "an invalid value is being created (such as a null reference)"
2364 }
2365
2366 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2367
2368 /// Information about why a type cannot be initialized this way.
2369 pub struct InitError {
2370 pub(crate) message: String,
2371 /// Spans from struct fields and similar that can be obtained from just the type.
2372 pub(crate) span: Option<Span>,
2373 /// Used to report a trace through adts.
2374 pub(crate) nested: Option<Box<InitError>>,
2375 }
2376 impl InitError {
spanned(self, span: Span) -> InitError2377 fn spanned(self, span: Span) -> InitError {
2378 Self { span: Some(span), ..self }
2379 }
2380
nested(self, nested: impl Into<Option<InitError>>) -> InitError2381 fn nested(self, nested: impl Into<Option<InitError>>) -> InitError {
2382 assert!(self.nested.is_none());
2383 Self { nested: nested.into().map(Box::new), ..self }
2384 }
2385 }
2386
2387 impl<'a> From<&'a str> for InitError {
from(s: &'a str) -> Self2388 fn from(s: &'a str) -> Self {
2389 s.to_owned().into()
2390 }
2391 }
2392 impl From<String> for InitError {
from(message: String) -> Self2393 fn from(message: String) -> Self {
2394 Self { message, span: None, nested: None }
2395 }
2396 }
2397
2398 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>)2399 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2400 #[derive(Debug, Copy, Clone, PartialEq)]
2401 enum InitKind {
2402 Zeroed,
2403 Uninit,
2404 }
2405
2406 /// Test if this constant is all-0.
2407 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2408 use hir::ExprKind::*;
2409 use rustc_ast::LitKind::*;
2410 match &expr.kind {
2411 Lit(lit) => {
2412 if let Int(i, _) = lit.node {
2413 i == 0
2414 } else {
2415 false
2416 }
2417 }
2418 Tup(tup) => tup.iter().all(is_zero),
2419 _ => false,
2420 }
2421 }
2422
2423 /// Determine if this expression is a "dangerous initialization".
2424 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2425 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2426 // Find calls to `mem::{uninitialized,zeroed}` methods.
2427 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2428 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2429 match cx.tcx.get_diagnostic_name(def_id) {
2430 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2431 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2432 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2433 _ => {}
2434 }
2435 }
2436 } else if let hir::ExprKind::MethodCall(_, receiver, ..) = expr.kind {
2437 // Find problematic calls to `MaybeUninit::assume_init`.
2438 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2439 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2440 // This is a call to *some* method named `assume_init`.
2441 // See if the `self` parameter is one of the dangerous constructors.
2442 if let hir::ExprKind::Call(ref path_expr, _) = receiver.kind {
2443 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2444 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2445 match cx.tcx.get_diagnostic_name(def_id) {
2446 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2447 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2448 _ => {}
2449 }
2450 }
2451 }
2452 }
2453 }
2454
2455 None
2456 }
2457
2458 fn variant_find_init_error<'tcx>(
2459 cx: &LateContext<'tcx>,
2460 ty: Ty<'tcx>,
2461 variant: &VariantDef,
2462 substs: ty::SubstsRef<'tcx>,
2463 descr: &str,
2464 init: InitKind,
2465 ) -> Option<InitError> {
2466 let mut field_err = variant.fields.iter().find_map(|field| {
2467 ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|mut err| {
2468 if !field.did.is_local() {
2469 err
2470 } else if err.span.is_none() {
2471 err.span = Some(cx.tcx.def_span(field.did));
2472 write!(&mut err.message, " (in this {descr})").unwrap();
2473 err
2474 } else {
2475 InitError::from(format!("in this {descr}"))
2476 .spanned(cx.tcx.def_span(field.did))
2477 .nested(err)
2478 }
2479 })
2480 });
2481
2482 // Check if this ADT has a constrained layout (like `NonNull` and friends).
2483 if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty)) {
2484 if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &layout.abi {
2485 let range = scalar.valid_range(cx);
2486 let msg = if !range.contains(0) {
2487 "must be non-null"
2488 } else if init == InitKind::Uninit && !scalar.is_always_valid(cx) {
2489 // Prefer reporting on the fields over the entire struct for uninit,
2490 // as the information bubbles out and it may be unclear why the type can't
2491 // be null from just its outside signature.
2492
2493 "must be initialized inside its custom valid range"
2494 } else {
2495 return field_err;
2496 };
2497 if let Some(field_err) = &mut field_err {
2498 // Most of the time, if the field error is the same as the struct error,
2499 // the struct error only happens because of the field error.
2500 if field_err.message.contains(msg) {
2501 field_err.message = format!("because {}", field_err.message);
2502 }
2503 }
2504 return Some(InitError::from(format!("`{ty}` {msg}")).nested(field_err));
2505 }
2506 }
2507 field_err
2508 }
2509
2510 /// Return `Some` only if we are sure this type does *not*
2511 /// allow zero initialization.
2512 fn ty_find_init_error<'tcx>(
2513 cx: &LateContext<'tcx>,
2514 ty: Ty<'tcx>,
2515 init: InitKind,
2516 ) -> Option<InitError> {
2517 use rustc_type_ir::sty::TyKind::*;
2518 match ty.kind() {
2519 // Primitive types that don't like 0 as a value.
2520 Ref(..) => Some("references must be non-null".into()),
2521 Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),
2522 FnPtr(..) => Some("function pointers must be non-null".into()),
2523 Never => Some("the `!` type has no valid value".into()),
2524 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2525 // raw ptr to dyn Trait
2526 {
2527 Some("the vtable of a wide raw pointer must be non-null".into())
2528 }
2529 // Primitive types with other constraints.
2530 Bool if init == InitKind::Uninit => {
2531 Some("booleans must be either `true` or `false`".into())
2532 }
2533 Char if init == InitKind::Uninit => {
2534 Some("characters must be a valid Unicode codepoint".into())
2535 }
2536 Int(_) | Uint(_) if init == InitKind::Uninit => {
2537 Some("integers must be initialized".into())
2538 }
2539 Float(_) if init == InitKind::Uninit => Some("floats must be initialized".into()),
2540 RawPtr(_) if init == InitKind::Uninit => {
2541 Some("raw pointers must be initialized".into())
2542 }
2543 // Recurse and checks for some compound types. (but not unions)
2544 Adt(adt_def, substs) if !adt_def.is_union() => {
2545 // Handle structs.
2546 if adt_def.is_struct() {
2547 return variant_find_init_error(
2548 cx,
2549 ty,
2550 adt_def.non_enum_variant(),
2551 substs,
2552 "struct field",
2553 init,
2554 );
2555 }
2556 // And now, enums.
2557 let span = cx.tcx.def_span(adt_def.did());
2558 let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
2559 let definitely_inhabited = match variant
2560 .inhabited_predicate(cx.tcx, *adt_def)
2561 .subst(cx.tcx, substs)
2562 .apply_any_module(cx.tcx, cx.param_env)
2563 {
2564 // Entirely skip uninhabited variants.
2565 Some(false) => return None,
2566 // Forward the others, but remember which ones are definitely inhabited.
2567 Some(true) => true,
2568 None => false,
2569 };
2570 Some((variant, definitely_inhabited))
2571 });
2572 let Some(first_variant) = potential_variants.next() else {
2573 return Some(InitError::from("enums with no inhabited variants have no valid value").spanned(span));
2574 };
2575 // So we have at least one potentially inhabited variant. Might we have two?
2576 let Some(second_variant) = potential_variants.next() else {
2577 // There is only one potentially inhabited variant. So we can recursively check that variant!
2578 return variant_find_init_error(
2579 cx,
2580 ty,
2581 &first_variant.0,
2582 substs,
2583 "field of the only potentially inhabited enum variant",
2584 init,
2585 );
2586 };
2587 // So we have at least two potentially inhabited variants.
2588 // If we can prove that we have at least two *definitely* inhabited variants,
2589 // then we have a tag and hence leaving this uninit is definitely disallowed.
2590 // (Leaving it zeroed could be okay, depending on which variant is encoded as zero tag.)
2591 if init == InitKind::Uninit {
2592 let definitely_inhabited = (first_variant.1 as usize)
2593 + (second_variant.1 as usize)
2594 + potential_variants
2595 .filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
2596 .count();
2597 if definitely_inhabited > 1 {
2598 return Some(InitError::from(
2599 "enums with multiple inhabited variants have to be initialized to a variant",
2600 ).spanned(span));
2601 }
2602 }
2603 // We couldn't find anything wrong here.
2604 None
2605 }
2606 Tuple(..) => {
2607 // Proceed recursively, check all fields.
2608 ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
2609 }
2610 Array(ty, len) => {
2611 if matches!(len.try_eval_target_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
2612 // Array length known at array non-empty -- recurse.
2613 ty_find_init_error(cx, *ty, init)
2614 } else {
2615 // Empty array or size unknown.
2616 None
2617 }
2618 }
2619 // Conservative fallback.
2620 _ => None,
2621 }
2622 }
2623
2624 if let Some(init) = is_dangerous_init(cx, expr) {
2625 // This conjures an instance of a type out of nothing,
2626 // using zeroed or uninitialized memory.
2627 // We are extremely conservative with what we warn about.
2628 let conjured_ty = cx.typeck_results().expr_ty(expr);
2629 if let Some(err) = with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init)) {
2630 let msg = match init {
2631 InitKind::Zeroed => fluent::lint_builtin_unpermitted_type_init_zeroed,
2632 InitKind::Uninit => fluent::lint_builtin_unpermitted_type_init_uninit,
2633 };
2634 let sub = BuiltinUnpermittedTypeInitSub { err };
2635 cx.emit_spanned_lint(
2636 INVALID_VALUE,
2637 expr.span,
2638 BuiltinUnpermittedTypeInit {
2639 msg,
2640 ty: conjured_ty,
2641 label: expr.span,
2642 sub,
2643 tcx: cx.tcx,
2644 },
2645 );
2646 }
2647 }
2648 }
2649 }
2650
2651 declare_lint! {
2652 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2653 /// has been declared with the same name but different types.
2654 ///
2655 /// ### Example
2656 ///
2657 /// ```rust
2658 /// mod m {
2659 /// extern "C" {
2660 /// fn foo();
2661 /// }
2662 /// }
2663 ///
2664 /// extern "C" {
2665 /// fn foo(_: u32);
2666 /// }
2667 /// ```
2668 ///
2669 /// {{produces}}
2670 ///
2671 /// ### Explanation
2672 ///
2673 /// Because two symbols of the same name cannot be resolved to two
2674 /// different functions at link time, and one function cannot possibly
2675 /// have two types, a clashing extern declaration is almost certainly a
2676 /// mistake. Check to make sure that the `extern` definitions are correct
2677 /// and equivalent, and possibly consider unifying them in one location.
2678 ///
2679 /// This lint does not run between crates because a project may have
2680 /// dependencies which both rely on the same extern function, but declare
2681 /// it in a different (but valid) way. For example, they may both declare
2682 /// an opaque type for one or more of the arguments (which would end up
2683 /// distinct types), or use types that are valid conversions in the
2684 /// language the `extern fn` is defined in. In these cases, the compiler
2685 /// can't say that the clashing declaration is incorrect.
2686 pub CLASHING_EXTERN_DECLARATIONS,
2687 Warn,
2688 "detects when an extern fn has been declared with the same name but different types"
2689 }
2690
2691 pub struct ClashingExternDeclarations {
2692 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2693 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2694 /// the symbol should be reported as a clashing declaration.
2695 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2696 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2697 seen_decls: FxHashMap<Symbol, hir::OwnerId>,
2698 }
2699
2700 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2701 /// just from declaration itself. This is important because we don't want to report clashes on
2702 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2703 /// different name.
2704 enum SymbolName {
2705 /// The name of the symbol + the span of the annotation which introduced the link name.
2706 Link(Symbol, Span),
2707 /// No link name, so just the name of the symbol.
2708 Normal(Symbol),
2709 }
2710
2711 impl SymbolName {
get_name(&self) -> Symbol2712 fn get_name(&self) -> Symbol {
2713 match self {
2714 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2715 }
2716 }
2717 }
2718
2719 impl ClashingExternDeclarations {
new() -> Self2720 pub(crate) fn new() -> Self {
2721 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2722 }
2723
2724 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2725 /// for the item, return its HirId without updating the set.
insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<hir::OwnerId>2726 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<hir::OwnerId> {
2727 let did = fi.owner_id.to_def_id();
2728 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2729 let name = Symbol::intern(tcx.symbol_name(instance).name);
2730 if let Some(&existing_id) = self.seen_decls.get(&name) {
2731 // Avoid updating the map with the new entry when we do find a collision. We want to
2732 // make sure we're always pointing to the first definition as the previous declaration.
2733 // This lets us avoid emitting "knock-on" diagnostics.
2734 Some(existing_id)
2735 } else {
2736 self.seen_decls.insert(name, fi.owner_id)
2737 }
2738 }
2739
2740 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2741 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2742 /// symbol's name.
name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName2743 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2744 if let Some((overridden_link_name, overridden_link_name_span)) =
2745 tcx.codegen_fn_attrs(fi.owner_id).link_name.map(|overridden_link_name| {
2746 // FIXME: Instead of searching through the attributes again to get span
2747 // information, we could have codegen_fn_attrs also give span information back for
2748 // where the attribute was defined. However, until this is found to be a
2749 // bottleneck, this does just fine.
2750 (overridden_link_name, tcx.get_attr(fi.owner_id, sym::link_name).unwrap().span)
2751 })
2752 {
2753 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2754 } else {
2755 SymbolName::Normal(fi.ident.name)
2756 }
2757 }
2758
2759 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2760 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2761 /// with the same members (as the declarations shouldn't clash).
structurally_same_type<'tcx>( cx: &LateContext<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>, ckind: CItemKind, ) -> bool2762 fn structurally_same_type<'tcx>(
2763 cx: &LateContext<'tcx>,
2764 a: Ty<'tcx>,
2765 b: Ty<'tcx>,
2766 ckind: CItemKind,
2767 ) -> bool {
2768 fn structurally_same_type_impl<'tcx>(
2769 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2770 cx: &LateContext<'tcx>,
2771 a: Ty<'tcx>,
2772 b: Ty<'tcx>,
2773 ckind: CItemKind,
2774 ) -> bool {
2775 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2776 let tcx = cx.tcx;
2777
2778 // Given a transparent newtype, reach through and grab the inner
2779 // type unless the newtype makes the type non-null.
2780 let non_transparent_ty = |mut ty: Ty<'tcx>| -> Ty<'tcx> {
2781 loop {
2782 if let ty::Adt(def, substs) = *ty.kind() {
2783 let is_transparent = def.repr().transparent();
2784 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
2785 debug!(
2786 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2787 ty, is_transparent, is_non_null
2788 );
2789 if is_transparent && !is_non_null {
2790 debug_assert_eq!(def.variants().len(), 1);
2791 let v = &def.variant(FIRST_VARIANT);
2792 // continue with `ty`'s non-ZST field,
2793 // otherwise `ty` is a ZST and we can return
2794 if let Some(field) = transparent_newtype_field(tcx, v) {
2795 ty = field.ty(tcx, substs);
2796 continue;
2797 }
2798 }
2799 }
2800 debug!("non_transparent_ty -> {:?}", ty);
2801 return ty;
2802 }
2803 };
2804
2805 let a = non_transparent_ty(a);
2806 let b = non_transparent_ty(b);
2807
2808 if !seen_types.insert((a, b)) {
2809 // We've encountered a cycle. There's no point going any further -- the types are
2810 // structurally the same.
2811 true
2812 } else if a == b {
2813 // All nominally-same types are structurally same, too.
2814 true
2815 } else {
2816 // Do a full, depth-first comparison between the two.
2817 use rustc_type_ir::sty::TyKind::*;
2818 let a_kind = a.kind();
2819 let b_kind = b.kind();
2820
2821 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2822 debug!("compare_layouts({:?}, {:?})", a, b);
2823 let a_layout = &cx.layout_of(a)?.layout.abi();
2824 let b_layout = &cx.layout_of(b)?.layout.abi();
2825 debug!(
2826 "comparing layouts: {:?} == {:?} = {}",
2827 a_layout,
2828 b_layout,
2829 a_layout == b_layout
2830 );
2831 Ok(a_layout == b_layout)
2832 };
2833
2834 #[allow(rustc::usage_of_ty_tykind)]
2835 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2836 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2837 };
2838
2839 ensure_sufficient_stack(|| {
2840 match (a_kind, b_kind) {
2841 (Adt(a_def, _), Adt(b_def, _)) => {
2842 // We can immediately rule out these types as structurally same if
2843 // their layouts differ.
2844 match compare_layouts(a, b) {
2845 Ok(false) => return false,
2846 _ => (), // otherwise, continue onto the full, fields comparison
2847 }
2848
2849 // Grab a flattened representation of all fields.
2850 let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
2851 let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
2852
2853 // Perform a structural comparison for each field.
2854 a_fields.eq_by(
2855 b_fields,
2856 |&ty::FieldDef { did: a_did, .. },
2857 &ty::FieldDef { did: b_did, .. }| {
2858 structurally_same_type_impl(
2859 seen_types,
2860 cx,
2861 tcx.type_of(a_did).subst_identity(),
2862 tcx.type_of(b_did).subst_identity(),
2863 ckind,
2864 )
2865 },
2866 )
2867 }
2868 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2869 // For arrays, we also check the constness of the type.
2870 a_const.kind() == b_const.kind()
2871 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2872 }
2873 (Slice(a_ty), Slice(b_ty)) => {
2874 structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2875 }
2876 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2877 a_tymut.mutbl == b_tymut.mutbl
2878 && structurally_same_type_impl(
2879 seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
2880 )
2881 }
2882 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2883 // For structural sameness, we don't need the region to be same.
2884 a_mut == b_mut
2885 && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
2886 }
2887 (FnDef(..), FnDef(..)) => {
2888 let a_poly_sig = a.fn_sig(tcx);
2889 let b_poly_sig = b.fn_sig(tcx);
2890
2891 // We don't compare regions, but leaving bound regions around ICEs, so
2892 // we erase them.
2893 let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
2894 let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
2895
2896 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2897 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2898 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2899 structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
2900 })
2901 && structurally_same_type_impl(
2902 seen_types,
2903 cx,
2904 a_sig.output(),
2905 b_sig.output(),
2906 ckind,
2907 )
2908 }
2909 (Tuple(a_substs), Tuple(b_substs)) => {
2910 a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
2911 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2912 })
2913 }
2914 // For these, it's not quite as easy to define structural-sameness quite so easily.
2915 // For the purposes of this lint, take the conservative approach and mark them as
2916 // not structurally same.
2917 (Dynamic(..), Dynamic(..))
2918 | (Error(..), Error(..))
2919 | (Closure(..), Closure(..))
2920 | (Generator(..), Generator(..))
2921 | (GeneratorWitness(..), GeneratorWitness(..))
2922 | (Alias(ty::Projection, ..), Alias(ty::Projection, ..))
2923 | (Alias(ty::Inherent, ..), Alias(ty::Inherent, ..))
2924 | (Alias(ty::Opaque, ..), Alias(ty::Opaque, ..)) => false,
2925
2926 // These definitely should have been caught above.
2927 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2928
2929 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2930 // enum layout optimisation is being applied.
2931 (Adt(..), other_kind) | (other_kind, Adt(..))
2932 if is_primitive_or_pointer(other_kind) =>
2933 {
2934 let (primitive, adt) =
2935 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2936 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2937 ty == primitive
2938 } else {
2939 compare_layouts(a, b).unwrap_or(false)
2940 }
2941 }
2942 // Otherwise, just compare the layouts. This may fail to lint for some
2943 // incompatible types, but at the very least, will stop reads into
2944 // uninitialised memory.
2945 _ => compare_layouts(a, b).unwrap_or(false),
2946 }
2947 })
2948 }
2949 }
2950 let mut seen_types = FxHashSet::default();
2951 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2952 }
2953 }
2954
2955 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2956
2957 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
2958 #[instrument(level = "trace", skip(self, cx))]
check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>)2959 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2960 if let ForeignItemKind::Fn(..) = this_fi.kind {
2961 let tcx = cx.tcx;
2962 if let Some(existing_did) = self.insert(tcx, this_fi) {
2963 let existing_decl_ty = tcx.type_of(existing_did).skip_binder();
2964 let this_decl_ty = tcx.type_of(this_fi.owner_id).subst_identity();
2965 debug!(
2966 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
2967 existing_did, existing_decl_ty, this_fi.owner_id, this_decl_ty
2968 );
2969 // Check that the declarations match.
2970 if !Self::structurally_same_type(
2971 cx,
2972 existing_decl_ty,
2973 this_decl_ty,
2974 CItemKind::Declaration,
2975 ) {
2976 let orig_fi = tcx.hir().expect_foreign_item(existing_did);
2977 let orig = Self::name_of_extern_decl(tcx, orig_fi);
2978
2979 // We want to ensure that we use spans for both decls that include where the
2980 // name was defined, whether that was from the link_name attribute or not.
2981 let get_relevant_span =
2982 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
2983 SymbolName::Normal(_) => fi.span,
2984 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
2985 };
2986
2987 // Finally, emit the diagnostic.
2988 let this = this_fi.ident.name;
2989 let orig = orig.get_name();
2990 let previous_decl_label = get_relevant_span(orig_fi);
2991 let mismatch_label = get_relevant_span(this_fi);
2992 let sub = BuiltinClashingExternSub {
2993 tcx,
2994 expected: existing_decl_ty,
2995 found: this_decl_ty,
2996 };
2997 let decorator = if orig == this {
2998 BuiltinClashingExtern::SameName {
2999 this,
3000 orig,
3001 previous_decl_label,
3002 mismatch_label,
3003 sub,
3004 }
3005 } else {
3006 BuiltinClashingExtern::DiffName {
3007 this,
3008 orig,
3009 previous_decl_label,
3010 mismatch_label,
3011 sub,
3012 }
3013 };
3014 tcx.emit_spanned_lint(
3015 CLASHING_EXTERN_DECLARATIONS,
3016 this_fi.hir_id(),
3017 get_relevant_span(this_fi),
3018 decorator,
3019 );
3020 }
3021 }
3022 }
3023 }
3024 }
3025
3026 declare_lint! {
3027 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3028 /// which causes [undefined behavior].
3029 ///
3030 /// ### Example
3031 ///
3032 /// ```rust,no_run
3033 /// # #![allow(unused)]
3034 /// use std::ptr;
3035 /// unsafe {
3036 /// let x = &*ptr::null::<i32>();
3037 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3038 /// let x = *(0 as *const i32);
3039 /// }
3040 /// ```
3041 ///
3042 /// {{produces}}
3043 ///
3044 /// ### Explanation
3045 ///
3046 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3047 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3048 ///
3049 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3050 pub DEREF_NULLPTR,
3051 Warn,
3052 "detects when an null pointer is dereferenced"
3053 }
3054
3055 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3056
3057 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>)3058 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3059 /// test if expression is a null ptr
3060 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3061 match &expr.kind {
3062 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3063 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3064 return is_zero(expr) || is_null_ptr(cx, expr);
3065 }
3066 }
3067 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3068 rustc_hir::ExprKind::Call(ref path, _) => {
3069 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3070 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3071 return matches!(
3072 cx.tcx.get_diagnostic_name(def_id),
3073 Some(sym::ptr_null | sym::ptr_null_mut)
3074 );
3075 }
3076 }
3077 }
3078 _ => {}
3079 }
3080 false
3081 }
3082
3083 /// test if expression is the literal `0`
3084 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3085 match &expr.kind {
3086 rustc_hir::ExprKind::Lit(ref lit) => {
3087 if let LitKind::Int(a, _) = lit.node {
3088 return a == 0;
3089 }
3090 }
3091 _ => {}
3092 }
3093 false
3094 }
3095
3096 if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3097 if is_null_ptr(cx, expr_deref) {
3098 cx.emit_spanned_lint(
3099 DEREF_NULLPTR,
3100 expr.span,
3101 BuiltinDerefNullptr { label: expr.span },
3102 );
3103 }
3104 }
3105 }
3106 }
3107
3108 declare_lint! {
3109 /// The `named_asm_labels` lint detects the use of named labels in the
3110 /// inline `asm!` macro.
3111 ///
3112 /// ### Example
3113 ///
3114 /// ```rust,compile_fail
3115 /// # #![feature(asm_experimental_arch)]
3116 /// use std::arch::asm;
3117 ///
3118 /// fn main() {
3119 /// unsafe {
3120 /// asm!("foo: bar");
3121 /// }
3122 /// }
3123 /// ```
3124 ///
3125 /// {{produces}}
3126 ///
3127 /// ### Explanation
3128 ///
3129 /// LLVM is allowed to duplicate inline assembly blocks for any
3130 /// reason, for example when it is in a function that gets inlined. Because
3131 /// of this, GNU assembler [local labels] *must* be used instead of labels
3132 /// with a name. Using named labels might cause assembler or linker errors.
3133 ///
3134 /// See the explanation in [Rust By Example] for more details.
3135 ///
3136 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3137 /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
3138 pub NAMED_ASM_LABELS,
3139 Deny,
3140 "named labels in inline assembly",
3141 }
3142
3143 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3144
3145 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
3146 #[allow(rustc::diagnostic_outside_of_impl)]
check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>)3147 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3148 if let hir::Expr {
3149 kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3150 ..
3151 } = expr
3152 {
3153 for (template_sym, template_snippet, template_span) in template_strs.iter() {
3154 let template_str = template_sym.as_str();
3155 let find_label_span = |needle: &str| -> Option<Span> {
3156 if let Some(template_snippet) = template_snippet {
3157 let snippet = template_snippet.as_str();
3158 if let Some(pos) = snippet.find(needle) {
3159 let end = pos
3160 + snippet[pos..]
3161 .find(|c| c == ':')
3162 .unwrap_or(snippet[pos..].len() - 1);
3163 let inner = InnerSpan::new(pos, end);
3164 return Some(template_span.from_inner(inner));
3165 }
3166 }
3167
3168 None
3169 };
3170
3171 let mut found_labels = Vec::new();
3172
3173 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3174 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3175 for statement in statements {
3176 // If there's a comment, trim it from the statement
3177 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3178 let mut start_idx = 0;
3179 for (idx, _) in statement.match_indices(':') {
3180 let possible_label = statement[start_idx..idx].trim();
3181 let mut chars = possible_label.chars();
3182 let Some(c) = chars.next() else {
3183 // Empty string means a leading ':' in this section, which is not a label
3184 break
3185 };
3186 // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3187 if (c.is_alphabetic() || matches!(c, '.' | '_'))
3188 && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3189 {
3190 found_labels.push(possible_label);
3191 } else {
3192 // If we encounter a non-label, there cannot be any further labels, so stop checking
3193 break;
3194 }
3195
3196 start_idx = idx + 1;
3197 }
3198 }
3199
3200 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3201
3202 if found_labels.len() > 0 {
3203 let spans = found_labels
3204 .into_iter()
3205 .filter_map(|label| find_label_span(label))
3206 .collect::<Vec<Span>>();
3207 // If there were labels but we couldn't find a span, combine the warnings and use the template span
3208 let target_spans: MultiSpan =
3209 if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3210
3211 cx.lookup_with_diagnostics(
3212 NAMED_ASM_LABELS,
3213 Some(target_spans),
3214 fluent::lint_builtin_asm_labels,
3215 |lint| lint,
3216 BuiltinLintDiagnostics::NamedAsmLabel(
3217 "only local labels of the form `<number>:` should be used in inline asm"
3218 .to_string(),
3219 ),
3220 );
3221 }
3222 }
3223 }
3224 }
3225 }
3226
3227 declare_lint! {
3228 /// The `special_module_name` lint detects module
3229 /// declarations for files that have a special meaning.
3230 ///
3231 /// ### Example
3232 ///
3233 /// ```rust,compile_fail
3234 /// mod lib;
3235 ///
3236 /// fn main() {
3237 /// lib::run();
3238 /// }
3239 /// ```
3240 ///
3241 /// {{produces}}
3242 ///
3243 /// ### Explanation
3244 ///
3245 /// Cargo recognizes `lib.rs` and `main.rs` as the root of a
3246 /// library or binary crate, so declaring them as modules
3247 /// will lead to miscompilation of the crate unless configured
3248 /// explicitly.
3249 ///
3250 /// To access a library from a binary target within the same crate,
3251 /// use `your_crate_name::` as the path instead of `lib::`:
3252 ///
3253 /// ```rust,compile_fail
3254 /// // bar/src/lib.rs
3255 /// fn run() {
3256 /// // ...
3257 /// }
3258 ///
3259 /// // bar/src/main.rs
3260 /// fn main() {
3261 /// bar::run();
3262 /// }
3263 /// ```
3264 ///
3265 /// Binary targets cannot be used as libraries and so declaring
3266 /// one as a module is not allowed.
3267 pub SPECIAL_MODULE_NAME,
3268 Warn,
3269 "module declarations for files with a special meaning",
3270 }
3271
3272 declare_lint_pass!(SpecialModuleName => [SPECIAL_MODULE_NAME]);
3273
3274 impl EarlyLintPass for SpecialModuleName {
check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate)3275 fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
3276 for item in &krate.items {
3277 if let ast::ItemKind::Mod(
3278 _,
3279 ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _),
3280 ) = item.kind
3281 {
3282 if item.attrs.iter().any(|a| a.has_name(sym::path)) {
3283 continue;
3284 }
3285
3286 match item.ident.name.as_str() {
3287 "lib" => cx.emit_spanned_lint(
3288 SPECIAL_MODULE_NAME,
3289 item.span,
3290 BuiltinSpecialModuleNameUsed::Lib,
3291 ),
3292 "main" => cx.emit_spanned_lint(
3293 SPECIAL_MODULE_NAME,
3294 item.span,
3295 BuiltinSpecialModuleNameUsed::Main,
3296 ),
3297 _ => continue,
3298 }
3299 }
3300 }
3301 }
3302 }
3303
3304 pub use rustc_session::lint::builtin::UNEXPECTED_CFGS;
3305
3306 declare_lint_pass!(UnexpectedCfgs => [UNEXPECTED_CFGS]);
3307
3308 impl EarlyLintPass for UnexpectedCfgs {
check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate)3309 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
3310 let cfg = &cx.sess().parse_sess.config;
3311 let check_cfg = &cx.sess().parse_sess.check_config;
3312 for &(name, value) in cfg {
3313 match check_cfg.expecteds.get(&name) {
3314 Some(ExpectedValues::Some(values)) if !values.contains(&value) => {
3315 let value = value.unwrap_or(kw::Empty);
3316 cx.emit_lint(UNEXPECTED_CFGS, BuiltinUnexpectedCliConfigValue { name, value });
3317 }
3318 None if check_cfg.exhaustive_names => {
3319 cx.emit_lint(UNEXPECTED_CFGS, BuiltinUnexpectedCliConfigName { name });
3320 }
3321 _ => { /* expected */ }
3322 }
3323 }
3324 }
3325 }
3326