1 //! Lints in the Rust compiler.
2 //!
3 //! This contains lints which can feasibly be implemented as their own
4 //! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
5 //! definitions of lints that are emitted directly inside the main compiler.
6 //!
7 //! To add a new lint to rustc, declare it here using `declare_lint!()`.
8 //! Then add code to emit the new lint in the appropriate circumstances.
9 //! You can do that in an existing `LintPass` if it makes sense, or in a
10 //! new `LintPass`, or using `Session::add_lint` elsewhere in the
11 //! compiler. Only do the latter if the check can't be written cleanly as a
12 //! `LintPass` (also, note that such lints will need to be defined in
13 //! `rustc_session::lint::builtin`, not here).
14 //!
15 //! If you define a new `EarlyLintPass`, you will also need to add it to the
16 //! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
17 //! `lib.rs`. Use the former for unit-like structs and the latter for structs
18 //! with a `pub fn new()`.
19 //!
20 //! If you define a new `LateLintPass`, you will also need to add it to the
21 //! `late_lint_methods!` invocation in `lib.rs`.
22
23 use crate::{
24 types::{transparent_newtype_field, CItemKind},
25 EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
26 };
27 use rustc_ast::attr;
28 use rustc_ast::tokenstream::{TokenStream, TokenTree};
29 use rustc_ast::visit::{FnCtxt, FnKind};
30 use rustc_ast::{self as ast, *};
31 use rustc_ast_pretty::pprust::{self, expr_to_string};
32 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
33 use rustc_data_structures::stack::ensure_sufficient_stack;
34 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
35 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
36 use rustc_hir as hir;
37 use rustc_hir::def::{DefKind, Res};
38 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
39 use rustc_hir::{ForeignItemKind, GenericParamKind, PatKind};
40 use rustc_hir::{HirId, Node};
41 use rustc_index::vec::Idx;
42 use rustc_middle::lint::LintDiagnosticBuilder;
43 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
44 use rustc_middle::ty::print::with_no_trimmed_paths;
45 use rustc_middle::ty::subst::{GenericArgKind, Subst};
46 use rustc_middle::ty::Instance;
47 use rustc_middle::ty::{self, Ty, TyCtxt};
48 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
49 use rustc_span::edition::Edition;
50 use rustc_span::source_map::Spanned;
51 use rustc_span::symbol::{kw, sym, Ident, Symbol};
52 use rustc_span::{BytePos, InnerSpan, MultiSpan, Span};
53 use rustc_target::abi::VariantIdx;
54 use rustc_trait_selection::traits::misc::can_type_implement_copy;
55
56 use crate::nonstandard_style::{method_context, MethodLateContext};
57
58 use std::fmt::Write;
59 use tracing::{debug, trace};
60
61 // hardwired lints from librustc_middle
62 pub use rustc_session::lint::builtin::*;
63
64 declare_lint! {
65 /// The `while_true` lint detects `while true { }`.
66 ///
67 /// ### Example
68 ///
69 /// ```rust,no_run
70 /// while true {
71 ///
72 /// }
73 /// ```
74 ///
75 /// {{produces}}
76 ///
77 /// ### Explanation
78 ///
79 /// `while true` should be replaced with `loop`. A `loop` expression is
80 /// the preferred way to write an infinite loop because it more directly
81 /// expresses the intent of the loop.
82 WHILE_TRUE,
83 Warn,
84 "suggest using `loop { }` instead of `while true { }`"
85 }
86
87 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
88
89 /// Traverse through any amount of parenthesis and return the first non-parens expression.
pierce_parens(mut expr: &ast::Expr) -> &ast::Expr90 fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
91 while let ast::ExprKind::Paren(sub) = &expr.kind {
92 expr = sub;
93 }
94 expr
95 }
96
97 impl EarlyLintPass for WhileTrue {
check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr)98 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
99 if let ast::ExprKind::While(cond, _, label) = &e.kind {
100 if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
101 if let ast::LitKind::Bool(true) = lit.kind {
102 if !lit.span.from_expansion() {
103 let msg = "denote infinite loops with `loop { ... }`";
104 let condition_span = e.span.with_hi(cond.span.hi());
105 cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
106 lint.build(msg)
107 .span_suggestion_short(
108 condition_span,
109 "use `loop`",
110 format!(
111 "{}loop",
112 label.map_or_else(String::new, |label| format!(
113 "{}: ",
114 label.ident,
115 ))
116 ),
117 Applicability::MachineApplicable,
118 )
119 .emit();
120 })
121 }
122 }
123 }
124 }
125 }
126 }
127
128 declare_lint! {
129 /// The `box_pointers` lints use of the Box type.
130 ///
131 /// ### Example
132 ///
133 /// ```rust,compile_fail
134 /// #![deny(box_pointers)]
135 /// struct Foo {
136 /// x: Box<isize>,
137 /// }
138 /// ```
139 ///
140 /// {{produces}}
141 ///
142 /// ### Explanation
143 ///
144 /// This lint is mostly historical, and not particularly useful. `Box<T>`
145 /// used to be built into the language, and the only way to do heap
146 /// allocation. Today's Rust can call into other allocators, etc.
147 BOX_POINTERS,
148 Allow,
149 "use of owned (Box type) heap memory"
150 }
151
152 declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
153
154 impl BoxPointers {
check_heap_type<'tcx>(&self, cx: &LateContext<'tcx>, span: Span, ty: Ty<'tcx>)155 fn check_heap_type<'tcx>(&self, cx: &LateContext<'tcx>, span: Span, ty: Ty<'tcx>) {
156 for leaf in ty.walk(cx.tcx) {
157 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
158 if leaf_ty.is_box() {
159 cx.struct_span_lint(BOX_POINTERS, span, |lint| {
160 lint.build(&format!("type uses owned (Box type) pointers: {}", ty)).emit()
161 });
162 }
163 }
164 }
165 }
166 }
167
168 impl<'tcx> LateLintPass<'tcx> for BoxPointers {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)169 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
170 match it.kind {
171 hir::ItemKind::Fn(..)
172 | hir::ItemKind::TyAlias(..)
173 | hir::ItemKind::Enum(..)
174 | hir::ItemKind::Struct(..)
175 | hir::ItemKind::Union(..) => {
176 self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
177 }
178 _ => (),
179 }
180
181 // If it's a struct, we also have to check the fields' types
182 match it.kind {
183 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
184 for struct_field in struct_def.fields() {
185 let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
186 self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
187 }
188 }
189 _ => (),
190 }
191 }
192
check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>)193 fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
194 let ty = cx.typeck_results().node_type(e.hir_id);
195 self.check_heap_type(cx, e.span, ty);
196 }
197 }
198
199 declare_lint! {
200 /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
201 /// instead of `Struct { x }` in a pattern.
202 ///
203 /// ### Example
204 ///
205 /// ```rust
206 /// struct Point {
207 /// x: i32,
208 /// y: i32,
209 /// }
210 ///
211 ///
212 /// fn main() {
213 /// let p = Point {
214 /// x: 5,
215 /// y: 5,
216 /// };
217 ///
218 /// match p {
219 /// Point { x: x, y: y } => (),
220 /// }
221 /// }
222 /// ```
223 ///
224 /// {{produces}}
225 ///
226 /// ### Explanation
227 ///
228 /// The preferred style is to avoid the repetition of specifying both the
229 /// field name and the binding name if both identifiers are the same.
230 NON_SHORTHAND_FIELD_PATTERNS,
231 Warn,
232 "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
233 }
234
235 declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
236
237 impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>)238 fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
239 if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
240 let variant = cx
241 .typeck_results()
242 .pat_ty(pat)
243 .ty_adt_def()
244 .expect("struct pattern type is not an ADT")
245 .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
246 for fieldpat in field_pats {
247 if fieldpat.is_shorthand {
248 continue;
249 }
250 if fieldpat.span.from_expansion() {
251 // Don't lint if this is a macro expansion: macro authors
252 // shouldn't have to worry about this kind of style issue
253 // (Issue #49588)
254 continue;
255 }
256 if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
257 if cx.tcx.find_field_index(ident, &variant)
258 == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
259 {
260 cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
261 let mut err = lint
262 .build(&format!("the `{}:` in this pattern is redundant", ident));
263 let binding = match binding_annot {
264 hir::BindingAnnotation::Unannotated => None,
265 hir::BindingAnnotation::Mutable => Some("mut"),
266 hir::BindingAnnotation::Ref => Some("ref"),
267 hir::BindingAnnotation::RefMut => Some("ref mut"),
268 };
269 let ident = if let Some(binding) = binding {
270 format!("{} {}", binding, ident)
271 } else {
272 ident.to_string()
273 };
274 err.span_suggestion(
275 fieldpat.span,
276 "use shorthand field pattern",
277 ident,
278 Applicability::MachineApplicable,
279 );
280 err.emit();
281 });
282 }
283 }
284 }
285 }
286 }
287 }
288
289 declare_lint! {
290 /// The `unsafe_code` lint catches usage of `unsafe` code.
291 ///
292 /// ### Example
293 ///
294 /// ```rust,compile_fail
295 /// #![deny(unsafe_code)]
296 /// fn main() {
297 /// unsafe {
298 ///
299 /// }
300 /// }
301 /// ```
302 ///
303 /// {{produces}}
304 ///
305 /// ### Explanation
306 ///
307 /// This lint is intended to restrict the usage of `unsafe`, which can be
308 /// difficult to use correctly.
309 UNSAFE_CODE,
310 Allow,
311 "usage of `unsafe` code"
312 }
313
314 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
315
316 impl UnsafeCode {
report_unsafe( &self, cx: &EarlyContext<'_>, span: Span, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>), )317 fn report_unsafe(
318 &self,
319 cx: &EarlyContext<'_>,
320 span: Span,
321 decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
322 ) {
323 // This comes from a macro that has `#[allow_internal_unsafe]`.
324 if span.allows_unsafe() {
325 return;
326 }
327
328 cx.struct_span_lint(UNSAFE_CODE, span, decorate);
329 }
330
report_overriden_symbol_name(&self, cx: &EarlyContext<'_>, span: Span, msg: &str)331 fn report_overriden_symbol_name(&self, cx: &EarlyContext<'_>, span: Span, msg: &str) {
332 self.report_unsafe(cx, span, |lint| {
333 lint.build(msg)
334 .note(
335 "the linker's behavior with multiple libraries exporting duplicate symbol \
336 names is undefined and Rust cannot provide guarantees when you manually \
337 override them",
338 )
339 .emit();
340 })
341 }
342 }
343
344 impl EarlyLintPass for UnsafeCode {
check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute)345 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
346 if attr.has_name(sym::allow_internal_unsafe) {
347 self.report_unsafe(cx, attr.span, |lint| {
348 lint.build(
349 "`allow_internal_unsafe` allows defining \
350 macros using unsafe without triggering \
351 the `unsafe_code` lint at their call site",
352 )
353 .emit()
354 });
355 }
356 }
357
check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr)358 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
359 if let ast::ExprKind::Block(ref blk, _) = e.kind {
360 // Don't warn about generated blocks; that'll just pollute the output.
361 if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
362 self.report_unsafe(cx, blk.span, |lint| {
363 lint.build("usage of an `unsafe` block").emit()
364 });
365 }
366 }
367 }
368
check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item)369 fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
370 match it.kind {
371 ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => self
372 .report_unsafe(cx, it.span, |lint| {
373 lint.build("declaration of an `unsafe` trait").emit()
374 }),
375
376 ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => self
377 .report_unsafe(cx, it.span, |lint| {
378 lint.build("implementation of an `unsafe` trait").emit()
379 }),
380
381 ast::ItemKind::Fn(..) => {
382 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
383 self.report_overriden_symbol_name(
384 cx,
385 attr.span,
386 "declaration of a `no_mangle` function",
387 );
388 }
389 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
390 self.report_overriden_symbol_name(
391 cx,
392 attr.span,
393 "declaration of a function with `export_name`",
394 );
395 }
396 }
397
398 ast::ItemKind::Static(..) => {
399 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
400 self.report_overriden_symbol_name(
401 cx,
402 attr.span,
403 "declaration of a `no_mangle` static",
404 );
405 }
406 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
407 self.report_overriden_symbol_name(
408 cx,
409 attr.span,
410 "declaration of a static with `export_name`",
411 );
412 }
413 }
414
415 _ => {}
416 }
417 }
418
check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem)419 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
420 if let ast::AssocItemKind::Fn(..) = it.kind {
421 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
422 self.report_overriden_symbol_name(
423 cx,
424 attr.span,
425 "declaration of a `no_mangle` method",
426 );
427 }
428 if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
429 self.report_overriden_symbol_name(
430 cx,
431 attr.span,
432 "declaration of a method with `export_name`",
433 );
434 }
435 }
436 }
437
check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId)438 fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
439 if let FnKind::Fn(
440 ctxt,
441 _,
442 ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
443 _,
444 body,
445 ) = fk
446 {
447 let msg = match ctxt {
448 FnCtxt::Foreign => return,
449 FnCtxt::Free => "declaration of an `unsafe` function",
450 FnCtxt::Assoc(_) if body.is_none() => "declaration of an `unsafe` method",
451 FnCtxt::Assoc(_) => "implementation of an `unsafe` method",
452 };
453 self.report_unsafe(cx, span, |lint| lint.build(msg).emit());
454 }
455 }
456 }
457
458 declare_lint! {
459 /// The `missing_docs` lint detects missing documentation for public items.
460 ///
461 /// ### Example
462 ///
463 /// ```rust,compile_fail
464 /// #![deny(missing_docs)]
465 /// pub fn foo() {}
466 /// ```
467 ///
468 /// {{produces}}
469 ///
470 /// ### Explanation
471 ///
472 /// This lint is intended to ensure that a library is well-documented.
473 /// Items without documentation can be difficult for users to understand
474 /// how to use properly.
475 ///
476 /// This lint is "allow" by default because it can be noisy, and not all
477 /// projects may want to enforce everything to be documented.
478 pub MISSING_DOCS,
479 Allow,
480 "detects missing documentation for public members",
481 report_in_external_macro
482 }
483
484 pub struct MissingDoc {
485 /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
486 doc_hidden_stack: Vec<bool>,
487
488 /// Private traits or trait items that leaked through. Don't check their methods.
489 private_traits: FxHashSet<hir::HirId>,
490 }
491
492 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
493
has_doc(attr: &ast::Attribute) -> bool494 fn has_doc(attr: &ast::Attribute) -> bool {
495 if attr.is_doc_comment() {
496 return true;
497 }
498
499 if !attr.has_name(sym::doc) {
500 return false;
501 }
502
503 if attr.value_str().is_some() {
504 return true;
505 }
506
507 if let Some(list) = attr.meta_item_list() {
508 for meta in list {
509 if meta.has_name(sym::hidden) {
510 return true;
511 }
512 }
513 }
514
515 false
516 }
517
518 impl MissingDoc {
new() -> MissingDoc519 pub fn new() -> MissingDoc {
520 MissingDoc { doc_hidden_stack: vec![false], private_traits: FxHashSet::default() }
521 }
522
doc_hidden(&self) -> bool523 fn doc_hidden(&self) -> bool {
524 *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
525 }
526
check_missing_docs_attrs( &self, cx: &LateContext<'_>, def_id: LocalDefId, sp: Span, article: &'static str, desc: &'static str, )527 fn check_missing_docs_attrs(
528 &self,
529 cx: &LateContext<'_>,
530 def_id: LocalDefId,
531 sp: Span,
532 article: &'static str,
533 desc: &'static str,
534 ) {
535 // If we're building a test harness, then warning about
536 // documentation is probably not really relevant right now.
537 if cx.sess().opts.test {
538 return;
539 }
540
541 // `#[doc(hidden)]` disables missing_docs check.
542 if self.doc_hidden() {
543 return;
544 }
545
546 // Only check publicly-visible items, using the result from the privacy pass.
547 // It's an option so the crate root can also use this function (it doesn't
548 // have a `NodeId`).
549 if def_id != CRATE_DEF_ID {
550 if !cx.access_levels.is_exported(def_id) {
551 return;
552 }
553 }
554
555 let attrs = cx.tcx.get_attrs(def_id.to_def_id());
556 let has_doc = attrs.iter().any(has_doc);
557 if !has_doc {
558 cx.struct_span_lint(
559 MISSING_DOCS,
560 cx.tcx.sess.source_map().guess_head_span(sp),
561 |lint| {
562 lint.build(&format!("missing documentation for {} {}", article, desc)).emit()
563 },
564 );
565 }
566 }
567 }
568
569 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute])570 fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
571 let doc_hidden = self.doc_hidden()
572 || attrs.iter().any(|attr| {
573 attr.has_name(sym::doc)
574 && match attr.meta_item_list() {
575 None => false,
576 Some(l) => attr::list_contains_name(&l, sym::hidden),
577 }
578 });
579 self.doc_hidden_stack.push(doc_hidden);
580 }
581
exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute])582 fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
583 self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
584 }
585
check_crate(&mut self, cx: &LateContext<'_>)586 fn check_crate(&mut self, cx: &LateContext<'_>) {
587 self.check_missing_docs_attrs(
588 cx,
589 CRATE_DEF_ID,
590 cx.tcx.def_span(CRATE_DEF_ID),
591 "the",
592 "crate",
593 );
594 }
595
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)596 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
597 match it.kind {
598 hir::ItemKind::Trait(.., trait_item_refs) => {
599 // Issue #11592: traits are always considered exported, even when private.
600 if let hir::VisibilityKind::Inherited = it.vis.node {
601 self.private_traits.insert(it.hir_id());
602 for trait_item_ref in trait_item_refs {
603 self.private_traits.insert(trait_item_ref.id.hir_id());
604 }
605 return;
606 }
607 }
608 hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref trait_ref), items, .. }) => {
609 // If the trait is private, add the impl items to `private_traits` so they don't get
610 // reported for missing docs.
611 let real_trait = trait_ref.path.res.def_id();
612 if let Some(def_id) = real_trait.as_local() {
613 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
614 if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
615 if let hir::VisibilityKind::Inherited = item.vis.node {
616 for impl_item_ref in items {
617 self.private_traits.insert(impl_item_ref.id.hir_id());
618 }
619 }
620 }
621 }
622 return;
623 }
624
625 hir::ItemKind::TyAlias(..)
626 | hir::ItemKind::Fn(..)
627 | hir::ItemKind::Macro(..)
628 | hir::ItemKind::Mod(..)
629 | hir::ItemKind::Enum(..)
630 | hir::ItemKind::Struct(..)
631 | hir::ItemKind::Union(..)
632 | hir::ItemKind::Const(..)
633 | hir::ItemKind::Static(..) => {}
634
635 _ => return,
636 };
637
638 let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
639
640 self.check_missing_docs_attrs(cx, it.def_id, it.span, article, desc);
641 }
642
check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>)643 fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
644 if self.private_traits.contains(&trait_item.hir_id()) {
645 return;
646 }
647
648 let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
649
650 self.check_missing_docs_attrs(cx, trait_item.def_id, trait_item.span, article, desc);
651 }
652
check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>)653 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
654 // If the method is an impl for a trait, don't doc.
655 if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
656 return;
657 }
658
659 // If the method is an impl for an item with docs_hidden, don't doc.
660 if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
661 let parent = cx.tcx.hir().get_parent_did(impl_item.hir_id());
662 let impl_ty = cx.tcx.type_of(parent);
663 let outerdef = match impl_ty.kind() {
664 ty::Adt(def, _) => Some(def.did),
665 ty::Foreign(def_id) => Some(*def_id),
666 _ => None,
667 };
668 let is_hidden = match outerdef {
669 Some(id) => cx.tcx.is_doc_hidden(id),
670 None => false,
671 };
672 if is_hidden {
673 return;
674 }
675 }
676
677 let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
678 self.check_missing_docs_attrs(cx, impl_item.def_id, impl_item.span, article, desc);
679 }
680
check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>)681 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
682 let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
683 self.check_missing_docs_attrs(cx, foreign_item.def_id, foreign_item.span, article, desc);
684 }
685
check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>)686 fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
687 if !sf.is_positional() {
688 let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
689 self.check_missing_docs_attrs(cx, def_id, sf.span, "a", "struct field")
690 }
691 }
692
check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>)693 fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
694 self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), v.span, "a", "variant");
695 }
696 }
697
698 declare_lint! {
699 /// The `missing_copy_implementations` lint detects potentially-forgotten
700 /// implementations of [`Copy`].
701 ///
702 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
703 ///
704 /// ### Example
705 ///
706 /// ```rust,compile_fail
707 /// #![deny(missing_copy_implementations)]
708 /// pub struct Foo {
709 /// pub field: i32
710 /// }
711 /// # fn main() {}
712 /// ```
713 ///
714 /// {{produces}}
715 ///
716 /// ### Explanation
717 ///
718 /// Historically (before 1.0), types were automatically marked as `Copy`
719 /// if possible. This was changed so that it required an explicit opt-in
720 /// by implementing the `Copy` trait. As part of this change, a lint was
721 /// added to alert if a copyable type was not marked `Copy`.
722 ///
723 /// This lint is "allow" by default because this code isn't bad; it is
724 /// common to write newtypes like this specifically so that a `Copy` type
725 /// is no longer `Copy`. `Copy` types can result in unintended copies of
726 /// large data which can impact performance.
727 pub MISSING_COPY_IMPLEMENTATIONS,
728 Allow,
729 "detects potentially-forgotten implementations of `Copy`"
730 }
731
732 declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
733
734 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)735 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
736 if !cx.access_levels.is_reachable(item.def_id) {
737 return;
738 }
739 let (def, ty) = match item.kind {
740 hir::ItemKind::Struct(_, ref ast_generics) => {
741 if !ast_generics.params.is_empty() {
742 return;
743 }
744 let def = cx.tcx.adt_def(item.def_id);
745 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
746 }
747 hir::ItemKind::Union(_, ref ast_generics) => {
748 if !ast_generics.params.is_empty() {
749 return;
750 }
751 let def = cx.tcx.adt_def(item.def_id);
752 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
753 }
754 hir::ItemKind::Enum(_, ref ast_generics) => {
755 if !ast_generics.params.is_empty() {
756 return;
757 }
758 let def = cx.tcx.adt_def(item.def_id);
759 (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
760 }
761 _ => return,
762 };
763 if def.has_dtor(cx.tcx) {
764 return;
765 }
766 let param_env = ty::ParamEnv::empty();
767 if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
768 return;
769 }
770 if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
771 cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
772 lint.build(
773 "type could implement `Copy`; consider adding `impl \
774 Copy`",
775 )
776 .emit()
777 })
778 }
779 }
780 }
781
782 declare_lint! {
783 /// The `missing_debug_implementations` lint detects missing
784 /// implementations of [`fmt::Debug`].
785 ///
786 /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
787 ///
788 /// ### Example
789 ///
790 /// ```rust,compile_fail
791 /// #![deny(missing_debug_implementations)]
792 /// pub struct Foo;
793 /// # fn main() {}
794 /// ```
795 ///
796 /// {{produces}}
797 ///
798 /// ### Explanation
799 ///
800 /// Having a `Debug` implementation on all types can assist with
801 /// debugging, as it provides a convenient way to format and display a
802 /// value. Using the `#[derive(Debug)]` attribute will automatically
803 /// generate a typical implementation, or a custom implementation can be
804 /// added by manually implementing the `Debug` trait.
805 ///
806 /// This lint is "allow" by default because adding `Debug` to all types can
807 /// have a negative impact on compile time and code size. It also requires
808 /// boilerplate to be added to every type, which can be an impediment.
809 MISSING_DEBUG_IMPLEMENTATIONS,
810 Allow,
811 "detects missing implementations of Debug"
812 }
813
814 #[derive(Default)]
815 pub struct MissingDebugImplementations {
816 impling_types: Option<LocalDefIdSet>,
817 }
818
819 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
820
821 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)822 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
823 if !cx.access_levels.is_reachable(item.def_id) {
824 return;
825 }
826
827 match item.kind {
828 hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
829 _ => return,
830 }
831
832 let debug = match cx.tcx.get_diagnostic_item(sym::Debug) {
833 Some(debug) => debug,
834 None => return,
835 };
836
837 if self.impling_types.is_none() {
838 let mut impls = LocalDefIdSet::default();
839 cx.tcx.for_each_impl(debug, |d| {
840 if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
841 if let Some(def_id) = ty_def.did.as_local() {
842 impls.insert(def_id);
843 }
844 }
845 });
846
847 self.impling_types = Some(impls);
848 debug!("{:?}", self.impling_types);
849 }
850
851 if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
852 cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
853 lint.build(&format!(
854 "type does not implement `{}`; consider adding `#[derive(Debug)]` \
855 or a manual implementation",
856 cx.tcx.def_path_str(debug)
857 ))
858 .emit()
859 });
860 }
861 }
862 }
863
864 declare_lint! {
865 /// The `anonymous_parameters` lint detects anonymous parameters in trait
866 /// definitions.
867 ///
868 /// ### Example
869 ///
870 /// ```rust,edition2015,compile_fail
871 /// #![deny(anonymous_parameters)]
872 /// // edition 2015
873 /// pub trait Foo {
874 /// fn foo(usize);
875 /// }
876 /// fn main() {}
877 /// ```
878 ///
879 /// {{produces}}
880 ///
881 /// ### Explanation
882 ///
883 /// This syntax is mostly a historical accident, and can be worked around
884 /// quite easily by adding an `_` pattern or a descriptive identifier:
885 ///
886 /// ```rust
887 /// trait Foo {
888 /// fn foo(_: usize);
889 /// }
890 /// ```
891 ///
892 /// This syntax is now a hard error in the 2018 edition. In the 2015
893 /// edition, this lint is "warn" by default. This lint
894 /// enables the [`cargo fix`] tool with the `--edition` flag to
895 /// automatically transition old code from the 2015 edition to 2018. The
896 /// tool will run this lint and automatically apply the
897 /// suggested fix from the compiler (which is to add `_` to each
898 /// parameter). This provides a completely automated way to update old
899 /// code for a new edition. See [issue #41686] for more details.
900 ///
901 /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
902 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
903 pub ANONYMOUS_PARAMETERS,
904 Warn,
905 "detects anonymous parameters",
906 @future_incompatible = FutureIncompatibleInfo {
907 reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
908 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
909 };
910 }
911
912 declare_lint_pass!(
913 /// Checks for use of anonymous parameters (RFC 1685).
914 AnonymousParameters => [ANONYMOUS_PARAMETERS]
915 );
916
917 impl EarlyLintPass for AnonymousParameters {
check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem)918 fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
919 if cx.sess.edition() != Edition::Edition2015 {
920 // This is a hard error in future editions; avoid linting and erroring
921 return;
922 }
923 if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
924 for arg in sig.decl.inputs.iter() {
925 if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
926 if ident.name == kw::Empty {
927 cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
928 let ty_snip = cx.sess.source_map().span_to_snippet(arg.ty.span);
929
930 let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
931 (snip.as_str(), Applicability::MachineApplicable)
932 } else {
933 ("<type>", Applicability::HasPlaceholders)
934 };
935
936 lint.build(
937 "anonymous parameters are deprecated and will be \
938 removed in the next edition",
939 )
940 .span_suggestion(
941 arg.pat.span,
942 "try naming the parameter or explicitly \
943 ignoring it",
944 format!("_: {}", ty_snip),
945 appl,
946 )
947 .emit();
948 })
949 }
950 }
951 }
952 }
953 }
954 }
955
956 /// Check for use of attributes which have been deprecated.
957 #[derive(Clone)]
958 pub struct DeprecatedAttr {
959 // This is not free to compute, so we want to keep it around, rather than
960 // compute it for every attribute.
961 depr_attrs: Vec<&'static BuiltinAttribute>,
962 }
963
964 impl_lint_pass!(DeprecatedAttr => []);
965
966 impl DeprecatedAttr {
new() -> DeprecatedAttr967 pub fn new() -> DeprecatedAttr {
968 DeprecatedAttr { depr_attrs: deprecated_attributes() }
969 }
970 }
971
lint_deprecated_attr( cx: &EarlyContext<'_>, attr: &ast::Attribute, msg: &str, suggestion: Option<&str>, )972 fn lint_deprecated_attr(
973 cx: &EarlyContext<'_>,
974 attr: &ast::Attribute,
975 msg: &str,
976 suggestion: Option<&str>,
977 ) {
978 cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
979 lint.build(msg)
980 .span_suggestion_short(
981 attr.span,
982 suggestion.unwrap_or("remove this attribute"),
983 String::new(),
984 Applicability::MachineApplicable,
985 )
986 .emit();
987 })
988 }
989
990 impl EarlyLintPass for DeprecatedAttr {
check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute)991 fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
992 for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
993 if attr.ident().map(|ident| ident.name) == Some(*name) {
994 if let &AttributeGate::Gated(
995 Stability::Deprecated(link, suggestion),
996 name,
997 reason,
998 _,
999 ) = gate
1000 {
1001 let msg =
1002 format!("use of deprecated attribute `{}`: {}. See {}", name, reason, link);
1003 lint_deprecated_attr(cx, attr, &msg, suggestion);
1004 }
1005 return;
1006 }
1007 }
1008 if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
1009 let path_str = pprust::path_to_string(&attr.get_normal_item().path);
1010 let msg = format!("use of deprecated attribute `{}`: no longer used.", path_str);
1011 lint_deprecated_attr(cx, attr, &msg, None);
1012 }
1013 }
1014 }
1015
warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute])1016 fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
1017 use rustc_ast::token::CommentKind;
1018
1019 let mut attrs = attrs.iter().peekable();
1020
1021 // Accumulate a single span for sugared doc comments.
1022 let mut sugared_span: Option<Span> = None;
1023
1024 while let Some(attr) = attrs.next() {
1025 let is_doc_comment = attr.is_doc_comment();
1026 if is_doc_comment {
1027 sugared_span =
1028 Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
1029 }
1030
1031 if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
1032 continue;
1033 }
1034
1035 let span = sugared_span.take().unwrap_or(attr.span);
1036
1037 if is_doc_comment || attr.has_name(sym::doc) {
1038 cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
1039 let mut err = lint.build("unused doc comment");
1040 err.span_label(
1041 node_span,
1042 format!("rustdoc does not generate documentation for {}", node_kind),
1043 );
1044 match attr.kind {
1045 AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
1046 err.help("use `//` for a plain comment");
1047 }
1048 AttrKind::DocComment(CommentKind::Block, _) => {
1049 err.help("use `/* */` for a plain comment");
1050 }
1051 }
1052 err.emit();
1053 });
1054 }
1055 }
1056 }
1057
1058 impl EarlyLintPass for UnusedDocComment {
check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt)1059 fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
1060 let kind = match stmt.kind {
1061 ast::StmtKind::Local(..) => "statements",
1062 // Disabled pending discussion in #78306
1063 ast::StmtKind::Item(..) => return,
1064 // expressions will be reported by `check_expr`.
1065 ast::StmtKind::Empty
1066 | ast::StmtKind::Semi(_)
1067 | ast::StmtKind::Expr(_)
1068 | ast::StmtKind::MacCall(_) => return,
1069 };
1070
1071 warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
1072 }
1073
check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm)1074 fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
1075 let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
1076 warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
1077 }
1078
check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr)1079 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
1080 warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
1081 }
1082 }
1083
1084 declare_lint! {
1085 /// The `no_mangle_const_items` lint detects any `const` items with the
1086 /// [`no_mangle` attribute].
1087 ///
1088 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1089 ///
1090 /// ### Example
1091 ///
1092 /// ```rust,compile_fail
1093 /// #[no_mangle]
1094 /// const FOO: i32 = 5;
1095 /// ```
1096 ///
1097 /// {{produces}}
1098 ///
1099 /// ### Explanation
1100 ///
1101 /// Constants do not have their symbols exported, and therefore, this
1102 /// probably means you meant to use a [`static`], not a [`const`].
1103 ///
1104 /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
1105 /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
1106 NO_MANGLE_CONST_ITEMS,
1107 Deny,
1108 "const items will not have their symbols exported"
1109 }
1110
1111 declare_lint! {
1112 /// The `no_mangle_generic_items` lint detects generic items that must be
1113 /// mangled.
1114 ///
1115 /// ### Example
1116 ///
1117 /// ```rust
1118 /// #[no_mangle]
1119 /// fn foo<T>(t: T) {
1120 ///
1121 /// }
1122 /// ```
1123 ///
1124 /// {{produces}}
1125 ///
1126 /// ### Explanation
1127 ///
1128 /// A function with generics must have its symbol mangled to accommodate
1129 /// the generic parameter. The [`no_mangle` attribute] has no effect in
1130 /// this situation, and should be removed.
1131 ///
1132 /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
1133 NO_MANGLE_GENERIC_ITEMS,
1134 Warn,
1135 "generic items must be mangled"
1136 }
1137
1138 declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
1139
1140 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)1141 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1142 let attrs = cx.tcx.hir().attrs(it.hir_id());
1143 let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
1144 impl_generics: Option<&hir::Generics<'_>>,
1145 generics: &hir::Generics<'_>,
1146 span| {
1147 for param in
1148 generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
1149 {
1150 match param.kind {
1151 GenericParamKind::Lifetime { .. } => {}
1152 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1153 cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
1154 lint.build("functions generic over types or consts must be mangled")
1155 .span_suggestion_short(
1156 no_mangle_attr.span,
1157 "remove this attribute",
1158 String::new(),
1159 // Use of `#[no_mangle]` suggests FFI intent; correct
1160 // fix may be to monomorphize source by hand
1161 Applicability::MaybeIncorrect,
1162 )
1163 .emit();
1164 });
1165 break;
1166 }
1167 }
1168 }
1169 };
1170 match it.kind {
1171 hir::ItemKind::Fn(.., ref generics, _) => {
1172 if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
1173 check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
1174 }
1175 }
1176 hir::ItemKind::Const(..) => {
1177 if cx.sess().contains_name(attrs, sym::no_mangle) {
1178 // Const items do not refer to a particular location in memory, and therefore
1179 // don't have anything to attach a symbol to
1180 cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
1181 let msg = "const items should never be `#[no_mangle]`";
1182 let mut err = lint.build(msg);
1183
1184 // account for "pub const" (#45562)
1185 let start = cx
1186 .tcx
1187 .sess
1188 .source_map()
1189 .span_to_snippet(it.span)
1190 .map(|snippet| snippet.find("const").unwrap_or(0))
1191 .unwrap_or(0) as u32;
1192 // `const` is 5 chars
1193 let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
1194 err.span_suggestion(
1195 const_span,
1196 "try a static value",
1197 "pub static".to_owned(),
1198 Applicability::MachineApplicable,
1199 );
1200 err.emit();
1201 });
1202 }
1203 }
1204 hir::ItemKind::Impl(hir::Impl { ref generics, items, .. }) => {
1205 for it in items {
1206 if let hir::AssocItemKind::Fn { .. } = it.kind {
1207 if let Some(no_mangle_attr) = cx
1208 .sess()
1209 .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
1210 {
1211 check_no_mangle_on_generic_fn(
1212 no_mangle_attr,
1213 Some(generics),
1214 cx.tcx.hir().get_generics(it.id.def_id.to_def_id()).unwrap(),
1215 it.span,
1216 );
1217 }
1218 }
1219 }
1220 }
1221 _ => {}
1222 }
1223 }
1224 }
1225
1226 declare_lint! {
1227 /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
1228 /// T` because it is [undefined behavior].
1229 ///
1230 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1231 ///
1232 /// ### Example
1233 ///
1234 /// ```rust,compile_fail
1235 /// unsafe {
1236 /// let y = std::mem::transmute::<&i32, &mut i32>(&5);
1237 /// }
1238 /// ```
1239 ///
1240 /// {{produces}}
1241 ///
1242 /// ### Explanation
1243 ///
1244 /// Certain assumptions are made about aliasing of data, and this transmute
1245 /// violates those assumptions. Consider using [`UnsafeCell`] instead.
1246 ///
1247 /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
1248 MUTABLE_TRANSMUTES,
1249 Deny,
1250 "mutating transmuted &mut T from &T may cause undefined behavior"
1251 }
1252
1253 declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
1254
1255 impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>)1256 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
1257 use rustc_target::spec::abi::Abi::RustIntrinsic;
1258 if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
1259 get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
1260 {
1261 if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
1262 let msg = "mutating transmuted &mut T from &T may cause undefined behavior, \
1263 consider instead using an UnsafeCell";
1264 cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| lint.build(msg).emit());
1265 }
1266 }
1267
1268 fn get_transmute_from_to<'tcx>(
1269 cx: &LateContext<'tcx>,
1270 expr: &hir::Expr<'_>,
1271 ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
1272 let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
1273 cx.qpath_res(qpath, expr.hir_id)
1274 } else {
1275 return None;
1276 };
1277 if let Res::Def(DefKind::Fn, did) = def {
1278 if !def_id_is_transmute(cx, did) {
1279 return None;
1280 }
1281 let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
1282 let from = sig.inputs().skip_binder()[0];
1283 let to = sig.output().skip_binder();
1284 return Some((from, to));
1285 }
1286 None
1287 }
1288
1289 fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
1290 cx.tcx.fn_sig(def_id).abi() == RustIntrinsic
1291 && cx.tcx.item_name(def_id) == sym::transmute
1292 }
1293 }
1294 }
1295
1296 declare_lint! {
1297 /// The `unstable_features` is deprecated and should no longer be used.
1298 UNSTABLE_FEATURES,
1299 Allow,
1300 "enabling unstable features (deprecated. do not use)"
1301 }
1302
1303 declare_lint_pass!(
1304 /// Forbids using the `#[feature(...)]` attribute
1305 UnstableFeatures => [UNSTABLE_FEATURES]
1306 );
1307
1308 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute)1309 fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
1310 if attr.has_name(sym::feature) {
1311 if let Some(items) = attr.meta_item_list() {
1312 for item in items {
1313 cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
1314 lint.build("unstable feature").emit()
1315 });
1316 }
1317 }
1318 }
1319 }
1320 }
1321
1322 declare_lint! {
1323 /// The `unreachable_pub` lint triggers for `pub` items not reachable from
1324 /// the crate root.
1325 ///
1326 /// ### Example
1327 ///
1328 /// ```rust,compile_fail
1329 /// #![deny(unreachable_pub)]
1330 /// mod foo {
1331 /// pub mod bar {
1332 ///
1333 /// }
1334 /// }
1335 /// ```
1336 ///
1337 /// {{produces}}
1338 ///
1339 /// ### Explanation
1340 ///
1341 /// A bare `pub` visibility may be misleading if the item is not actually
1342 /// publicly exported from the crate. The `pub(crate)` visibility is
1343 /// recommended to be used instead, which more clearly expresses the intent
1344 /// that the item is only visible within its own crate.
1345 ///
1346 /// This lint is "allow" by default because it will trigger for a large
1347 /// amount existing Rust code, and has some false-positives. Eventually it
1348 /// is desired for this to become warn-by-default.
1349 pub UNREACHABLE_PUB,
1350 Allow,
1351 "`pub` items not reachable from crate root"
1352 }
1353
1354 declare_lint_pass!(
1355 /// Lint for items marked `pub` that aren't reachable from other crates.
1356 UnreachablePub => [UNREACHABLE_PUB]
1357 );
1358
1359 impl UnreachablePub {
perform_lint( &self, cx: &LateContext<'_>, what: &str, def_id: LocalDefId, vis: &hir::Visibility<'_>, span: Span, exportable: bool, )1360 fn perform_lint(
1361 &self,
1362 cx: &LateContext<'_>,
1363 what: &str,
1364 def_id: LocalDefId,
1365 vis: &hir::Visibility<'_>,
1366 span: Span,
1367 exportable: bool,
1368 ) {
1369 let mut applicability = Applicability::MachineApplicable;
1370 match vis.node {
1371 hir::VisibilityKind::Public if !cx.access_levels.is_reachable(def_id) => {
1372 if span.from_expansion() {
1373 applicability = Applicability::MaybeIncorrect;
1374 }
1375 let def_span = cx.tcx.sess.source_map().guess_head_span(span);
1376 cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
1377 let mut err = lint.build(&format!("unreachable `pub` {}", what));
1378 let replacement = if cx.tcx.features().crate_visibility_modifier {
1379 "crate"
1380 } else {
1381 "pub(crate)"
1382 }
1383 .to_owned();
1384
1385 err.span_suggestion(
1386 vis.span,
1387 "consider restricting its visibility",
1388 replacement,
1389 applicability,
1390 );
1391 if exportable {
1392 err.help("or consider exporting it for use by other crates");
1393 }
1394 err.emit();
1395 });
1396 }
1397 _ => {}
1398 }
1399 }
1400 }
1401
1402 impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)1403 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1404 self.perform_lint(cx, "item", item.def_id, &item.vis, item.span, true);
1405 }
1406
check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>)1407 fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
1408 self.perform_lint(
1409 cx,
1410 "item",
1411 foreign_item.def_id,
1412 &foreign_item.vis,
1413 foreign_item.span,
1414 true,
1415 );
1416 }
1417
check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>)1418 fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
1419 let def_id = cx.tcx.hir().local_def_id(field.hir_id);
1420 self.perform_lint(cx, "field", def_id, &field.vis, field.span, false);
1421 }
1422
check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>)1423 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
1424 self.perform_lint(cx, "item", impl_item.def_id, &impl_item.vis, impl_item.span, false);
1425 }
1426 }
1427
1428 declare_lint! {
1429 /// The `type_alias_bounds` lint detects bounds in type aliases.
1430 ///
1431 /// ### Example
1432 ///
1433 /// ```rust
1434 /// type SendVec<T: Send> = Vec<T>;
1435 /// ```
1436 ///
1437 /// {{produces}}
1438 ///
1439 /// ### Explanation
1440 ///
1441 /// The trait bounds in a type alias are currently ignored, and should not
1442 /// be included to avoid confusion. This was previously allowed
1443 /// unintentionally; this may become a hard error in the future.
1444 TYPE_ALIAS_BOUNDS,
1445 Warn,
1446 "bounds in type aliases are not enforced"
1447 }
1448
1449 declare_lint_pass!(
1450 /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
1451 /// They are relevant when using associated types, but otherwise neither checked
1452 /// at definition site nor enforced at use site.
1453 TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
1454 );
1455
1456 impl TypeAliasBounds {
is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool1457 fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
1458 match *qpath {
1459 hir::QPath::TypeRelative(ref ty, _) => {
1460 // If this is a type variable, we found a `T::Assoc`.
1461 match ty.kind {
1462 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
1463 matches!(path.res, Res::Def(DefKind::TyParam, _))
1464 }
1465 _ => false,
1466 }
1467 }
1468 hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
1469 }
1470 }
1471
suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>)1472 fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut DiagnosticBuilder<'_>) {
1473 // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
1474 // bound. Let's see if this type does that.
1475
1476 // We use a HIR visitor to walk the type.
1477 use rustc_hir::intravisit::{self, Visitor};
1478 struct WalkAssocTypes<'a, 'db> {
1479 err: &'a mut DiagnosticBuilder<'db>,
1480 }
1481 impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
1482 type Map = intravisit::ErasedMap<'v>;
1483
1484 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1485 intravisit::NestedVisitorMap::None
1486 }
1487
1488 fn visit_qpath(&mut self, qpath: &'v hir::QPath<'v>, id: hir::HirId, span: Span) {
1489 if TypeAliasBounds::is_type_variable_assoc(qpath) {
1490 self.err.span_help(
1491 span,
1492 "use fully disambiguated paths (i.e., `<T as Trait>::Assoc`) to refer to \
1493 associated types in type aliases",
1494 );
1495 }
1496 intravisit::walk_qpath(self, qpath, id, span)
1497 }
1498 }
1499
1500 // Let's go for a walk!
1501 let mut visitor = WalkAssocTypes { err };
1502 visitor.visit_ty(ty);
1503 }
1504 }
1505
1506 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>)1507 fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
1508 let (ty, type_alias_generics) = match item.kind {
1509 hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
1510 _ => return,
1511 };
1512 if let hir::TyKind::OpaqueDef(..) = ty.kind {
1513 // Bounds are respected for `type X = impl Trait`
1514 return;
1515 }
1516 let mut suggested_changing_assoc_types = false;
1517 // There must not be a where clause
1518 if !type_alias_generics.where_clause.predicates.is_empty() {
1519 cx.lint(
1520 TYPE_ALIAS_BOUNDS,
1521 |lint| {
1522 let mut err = lint.build("where clauses are not enforced in type aliases");
1523 let spans: Vec<_> = type_alias_generics
1524 .where_clause
1525 .predicates
1526 .iter()
1527 .map(|pred| pred.span())
1528 .collect();
1529 err.set_span(spans);
1530 err.span_suggestion(
1531 type_alias_generics.where_clause.span_for_predicates_or_empty_place(),
1532 "the clause will not be checked when the type alias is used, and should be removed",
1533 String::new(),
1534 Applicability::MachineApplicable,
1535 );
1536 if !suggested_changing_assoc_types {
1537 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1538 suggested_changing_assoc_types = true;
1539 }
1540 err.emit();
1541 },
1542 );
1543 }
1544 // The parameters must not have bounds
1545 for param in type_alias_generics.params.iter() {
1546 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
1547 let suggestion = spans
1548 .iter()
1549 .map(|sp| {
1550 let start = param.span.between(*sp); // Include the `:` in `T: Bound`.
1551 (start.to(*sp), String::new())
1552 })
1553 .collect();
1554 if !spans.is_empty() {
1555 cx.struct_span_lint(TYPE_ALIAS_BOUNDS, spans, |lint| {
1556 let mut err =
1557 lint.build("bounds on generic parameters are not enforced in type aliases");
1558 let msg = "the bound will not be checked when the type alias is used, \
1559 and should be removed";
1560 err.multipart_suggestion(&msg, suggestion, Applicability::MachineApplicable);
1561 if !suggested_changing_assoc_types {
1562 TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
1563 suggested_changing_assoc_types = true;
1564 }
1565 err.emit();
1566 });
1567 }
1568 }
1569 }
1570 }
1571
1572 declare_lint_pass!(
1573 /// Lint constants that are erroneous.
1574 /// Without this lint, we might not get any diagnostic if the constant is
1575 /// unused within this crate, even though downstream crates can't use it
1576 /// without producing an error.
1577 UnusedBrokenConst => []
1578 );
1579
1580 impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)1581 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1582 match it.kind {
1583 hir::ItemKind::Const(_, body_id) => {
1584 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1585 // trigger the query once for all constants since that will already report the errors
1586 // FIXME: Use ensure here
1587 let _ = cx.tcx.const_eval_poly(def_id);
1588 }
1589 hir::ItemKind::Static(_, _, body_id) => {
1590 let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
1591 // FIXME: Use ensure here
1592 let _ = cx.tcx.eval_static_initializer(def_id);
1593 }
1594 _ => {}
1595 }
1596 }
1597 }
1598
1599 declare_lint! {
1600 /// The `trivial_bounds` lint detects trait bounds that don't depend on
1601 /// any type parameters.
1602 ///
1603 /// ### Example
1604 ///
1605 /// ```rust
1606 /// #![feature(trivial_bounds)]
1607 /// pub struct A where i32: Copy;
1608 /// ```
1609 ///
1610 /// {{produces}}
1611 ///
1612 /// ### Explanation
1613 ///
1614 /// Usually you would not write a trait bound that you know is always
1615 /// true, or never true. However, when using macros, the macro may not
1616 /// know whether or not the constraint would hold or not at the time when
1617 /// generating the code. Currently, the compiler does not alert you if the
1618 /// constraint is always true, and generates an error if it is never true.
1619 /// The `trivial_bounds` feature changes this to be a warning in both
1620 /// cases, giving macros more freedom and flexibility to generate code,
1621 /// while still providing a signal when writing non-macro code that
1622 /// something is amiss.
1623 ///
1624 /// See [RFC 2056] for more details. This feature is currently only
1625 /// available on the nightly channel, see [tracking issue #48214].
1626 ///
1627 /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
1628 /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
1629 TRIVIAL_BOUNDS,
1630 Warn,
1631 "these bounds don't depend on an type parameters"
1632 }
1633
1634 declare_lint_pass!(
1635 /// Lint for trait and lifetime bounds that don't depend on type parameters
1636 /// which either do nothing, or stop the item from being used.
1637 TrivialConstraints => [TRIVIAL_BOUNDS]
1638 );
1639
1640 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>)1641 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
1642 use rustc_middle::ty::fold::TypeFoldable;
1643 use rustc_middle::ty::PredicateKind::*;
1644
1645 if cx.tcx.features().trivial_bounds {
1646 let predicates = cx.tcx.predicates_of(item.def_id);
1647 for &(predicate, span) in predicates.predicates {
1648 let predicate_kind_name = match predicate.kind().skip_binder() {
1649 Trait(..) => "trait",
1650 TypeOutlives(..) |
1651 RegionOutlives(..) => "lifetime",
1652
1653 // Ignore projections, as they can only be global
1654 // if the trait bound is global
1655 Projection(..) |
1656 // Ignore bounds that a user can't type
1657 WellFormed(..) |
1658 ObjectSafe(..) |
1659 ClosureKind(..) |
1660 Subtype(..) |
1661 Coerce(..) |
1662 ConstEvaluatable(..) |
1663 ConstEquate(..) |
1664 TypeWellFormedFromEnv(..) => continue,
1665 };
1666 if predicate.is_global(cx.tcx) {
1667 cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
1668 lint.build(&format!(
1669 "{} bound {} does not depend on any type \
1670 or lifetime parameters",
1671 predicate_kind_name, predicate
1672 ))
1673 .emit()
1674 });
1675 }
1676 }
1677 }
1678 }
1679 }
1680
1681 declare_lint_pass!(
1682 /// Does nothing as a lint pass, but registers some `Lint`s
1683 /// which are used by other parts of the compiler.
1684 SoftLints => [
1685 WHILE_TRUE,
1686 BOX_POINTERS,
1687 NON_SHORTHAND_FIELD_PATTERNS,
1688 UNSAFE_CODE,
1689 MISSING_DOCS,
1690 MISSING_COPY_IMPLEMENTATIONS,
1691 MISSING_DEBUG_IMPLEMENTATIONS,
1692 ANONYMOUS_PARAMETERS,
1693 UNUSED_DOC_COMMENTS,
1694 NO_MANGLE_CONST_ITEMS,
1695 NO_MANGLE_GENERIC_ITEMS,
1696 MUTABLE_TRANSMUTES,
1697 UNSTABLE_FEATURES,
1698 UNREACHABLE_PUB,
1699 TYPE_ALIAS_BOUNDS,
1700 TRIVIAL_BOUNDS
1701 ]
1702 );
1703
1704 declare_lint! {
1705 /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
1706 /// pattern], which is deprecated.
1707 ///
1708 /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
1709 ///
1710 /// ### Example
1711 ///
1712 /// ```rust,edition2018
1713 /// let x = 123;
1714 /// match x {
1715 /// 0...100 => {}
1716 /// _ => {}
1717 /// }
1718 /// ```
1719 ///
1720 /// {{produces}}
1721 ///
1722 /// ### Explanation
1723 ///
1724 /// The `...` range pattern syntax was changed to `..=` to avoid potential
1725 /// confusion with the [`..` range expression]. Use the new form instead.
1726 ///
1727 /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
1728 pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
1729 Warn,
1730 "`...` range patterns are deprecated",
1731 @future_incompatible = FutureIncompatibleInfo {
1732 reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
1733 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
1734 };
1735 }
1736
1737 #[derive(Default)]
1738 pub struct EllipsisInclusiveRangePatterns {
1739 /// If `Some(_)`, suppress all subsequent pattern
1740 /// warnings for better diagnostics.
1741 node_id: Option<ast::NodeId>,
1742 }
1743
1744 impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
1745
1746 impl EarlyLintPass for EllipsisInclusiveRangePatterns {
check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat)1747 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
1748 if self.node_id.is_some() {
1749 // Don't recursively warn about patterns inside range endpoints.
1750 return;
1751 }
1752
1753 use self::ast::{PatKind, RangeSyntax::DotDotDot};
1754
1755 /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
1756 /// corresponding to the ellipsis.
1757 fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
1758 match &pat.kind {
1759 PatKind::Range(
1760 a,
1761 Some(b),
1762 Spanned { span, node: RangeEnd::Included(DotDotDot) },
1763 ) => Some((a.as_deref(), b, *span)),
1764 _ => None,
1765 }
1766 }
1767
1768 let (parenthesise, endpoints) = match &pat.kind {
1769 PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
1770 _ => (false, matches_ellipsis_pat(pat)),
1771 };
1772
1773 if let Some((start, end, join)) = endpoints {
1774 let msg = "`...` range patterns are deprecated";
1775 let suggestion = "use `..=` for an inclusive range";
1776 if parenthesise {
1777 self.node_id = Some(pat.id);
1778 let end = expr_to_string(&end);
1779 let replace = match start {
1780 Some(start) => format!("&({}..={})", expr_to_string(&start), end),
1781 None => format!("&(..={})", end),
1782 };
1783 if join.edition() >= Edition::Edition2021 {
1784 let mut err =
1785 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1786 err.span_suggestion(
1787 pat.span,
1788 suggestion,
1789 replace,
1790 Applicability::MachineApplicable,
1791 )
1792 .emit();
1793 } else {
1794 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
1795 lint.build(msg)
1796 .span_suggestion(
1797 pat.span,
1798 suggestion,
1799 replace,
1800 Applicability::MachineApplicable,
1801 )
1802 .emit();
1803 });
1804 }
1805 } else {
1806 let replace = "..=".to_owned();
1807 if join.edition() >= Edition::Edition2021 {
1808 let mut err =
1809 rustc_errors::struct_span_err!(cx.sess, pat.span, E0783, "{}", msg,);
1810 err.span_suggestion_short(
1811 join,
1812 suggestion,
1813 replace,
1814 Applicability::MachineApplicable,
1815 )
1816 .emit();
1817 } else {
1818 cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
1819 lint.build(msg)
1820 .span_suggestion_short(
1821 join,
1822 suggestion,
1823 replace,
1824 Applicability::MachineApplicable,
1825 )
1826 .emit();
1827 });
1828 }
1829 };
1830 }
1831 }
1832
check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat)1833 fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
1834 if let Some(node_id) = self.node_id {
1835 if pat.id == node_id {
1836 self.node_id = None
1837 }
1838 }
1839 }
1840 }
1841
1842 declare_lint! {
1843 /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
1844 /// that are not able to be run by the test harness because they are in a
1845 /// position where they are not nameable.
1846 ///
1847 /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
1848 ///
1849 /// ### Example
1850 ///
1851 /// ```rust,test
1852 /// fn main() {
1853 /// #[test]
1854 /// fn foo() {
1855 /// // This test will not fail because it does not run.
1856 /// assert_eq!(1, 2);
1857 /// }
1858 /// }
1859 /// ```
1860 ///
1861 /// {{produces}}
1862 ///
1863 /// ### Explanation
1864 ///
1865 /// In order for the test harness to run a test, the test function must be
1866 /// located in a position where it can be accessed from the crate root.
1867 /// This generally means it must be defined in a module, and not anywhere
1868 /// else such as inside another function. The compiler previously allowed
1869 /// this without an error, so a lint was added as an alert that a test is
1870 /// not being used. Whether or not this should be allowed has not yet been
1871 /// decided, see [RFC 2471] and [issue #36629].
1872 ///
1873 /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
1874 /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
1875 UNNAMEABLE_TEST_ITEMS,
1876 Warn,
1877 "detects an item that cannot be named being marked as `#[test_case]`",
1878 report_in_external_macro
1879 }
1880
1881 pub struct UnnameableTestItems {
1882 boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
1883 items_nameable: bool,
1884 }
1885
1886 impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
1887
1888 impl UnnameableTestItems {
new() -> Self1889 pub fn new() -> Self {
1890 Self { boundary: None, items_nameable: true }
1891 }
1892 }
1893
1894 impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>)1895 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1896 if self.items_nameable {
1897 if let hir::ItemKind::Mod(..) = it.kind {
1898 } else {
1899 self.items_nameable = false;
1900 self.boundary = Some(it.def_id);
1901 }
1902 return;
1903 }
1904
1905 let attrs = cx.tcx.hir().attrs(it.hir_id());
1906 if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
1907 cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
1908 lint.build("cannot test inner items").emit()
1909 });
1910 }
1911 }
1912
check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>)1913 fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
1914 if !self.items_nameable && self.boundary == Some(it.def_id) {
1915 self.items_nameable = true;
1916 }
1917 }
1918 }
1919
1920 declare_lint! {
1921 /// The `keyword_idents` lint detects edition keywords being used as an
1922 /// identifier.
1923 ///
1924 /// ### Example
1925 ///
1926 /// ```rust,edition2015,compile_fail
1927 /// #![deny(keyword_idents)]
1928 /// // edition 2015
1929 /// fn dyn() {}
1930 /// ```
1931 ///
1932 /// {{produces}}
1933 ///
1934 /// ### Explanation
1935 ///
1936 /// Rust [editions] allow the language to evolve without breaking
1937 /// backwards compatibility. This lint catches code that uses new keywords
1938 /// that are added to the language that are used as identifiers (such as a
1939 /// variable name, function name, etc.). If you switch the compiler to a
1940 /// new edition without updating the code, then it will fail to compile if
1941 /// you are using a new keyword as an identifier.
1942 ///
1943 /// You can manually change the identifiers to a non-keyword, or use a
1944 /// [raw identifier], for example `r#dyn`, to transition to a new edition.
1945 ///
1946 /// This lint solves the problem automatically. It is "allow" by default
1947 /// because the code is perfectly valid in older editions. The [`cargo
1948 /// fix`] tool with the `--edition` flag will switch this lint to "warn"
1949 /// and automatically apply the suggested fix from the compiler (which is
1950 /// to use a raw identifier). This provides a completely automated way to
1951 /// update old code for a new edition.
1952 ///
1953 /// [editions]: https://doc.rust-lang.org/edition-guide/
1954 /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
1955 /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
1956 pub KEYWORD_IDENTS,
1957 Allow,
1958 "detects edition keywords being used as an identifier",
1959 @future_incompatible = FutureIncompatibleInfo {
1960 reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
1961 reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
1962 };
1963 }
1964
1965 declare_lint_pass!(
1966 /// Check for uses of edition keywords used as an identifier.
1967 KeywordIdents => [KEYWORD_IDENTS]
1968 );
1969
1970 struct UnderMacro(bool);
1971
1972 impl KeywordIdents {
check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream)1973 fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
1974 for tt in tokens.into_trees() {
1975 match tt {
1976 // Only report non-raw idents.
1977 TokenTree::Token(token) => {
1978 if let Some((ident, false)) = token.ident() {
1979 self.check_ident_token(cx, UnderMacro(true), ident);
1980 }
1981 }
1982 TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
1983 }
1984 }
1985 }
1986
check_ident_token( &mut self, cx: &EarlyContext<'_>, UnderMacro(under_macro): UnderMacro, ident: Ident, )1987 fn check_ident_token(
1988 &mut self,
1989 cx: &EarlyContext<'_>,
1990 UnderMacro(under_macro): UnderMacro,
1991 ident: Ident,
1992 ) {
1993 let next_edition = match cx.sess.edition() {
1994 Edition::Edition2015 => {
1995 match ident.name {
1996 kw::Async | kw::Await | kw::Try => Edition::Edition2018,
1997
1998 // rust-lang/rust#56327: Conservatively do not
1999 // attempt to report occurrences of `dyn` within
2000 // macro definitions or invocations, because `dyn`
2001 // can legitimately occur as a contextual keyword
2002 // in 2015 code denoting its 2018 meaning, and we
2003 // do not want rustfix to inject bugs into working
2004 // code by rewriting such occurrences.
2005 //
2006 // But if we see `dyn` outside of a macro, we know
2007 // its precise role in the parsed AST and thus are
2008 // assured this is truly an attempt to use it as
2009 // an identifier.
2010 kw::Dyn if !under_macro => Edition::Edition2018,
2011
2012 _ => return,
2013 }
2014 }
2015
2016 // There are no new keywords yet for the 2018 edition and beyond.
2017 _ => return,
2018 };
2019
2020 // Don't lint `r#foo`.
2021 if cx.sess.parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
2022 return;
2023 }
2024
2025 cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
2026 lint.build(&format!("`{}` is a keyword in the {} edition", ident, next_edition))
2027 .span_suggestion(
2028 ident.span,
2029 "you can use a raw identifier to stay compatible",
2030 format!("r#{}", ident),
2031 Applicability::MachineApplicable,
2032 )
2033 .emit()
2034 });
2035 }
2036 }
2037
2038 impl EarlyLintPass for KeywordIdents {
check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId)2039 fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
2040 self.check_tokens(cx, mac_def.body.inner_tokens());
2041 }
check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall)2042 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
2043 self.check_tokens(cx, mac.args.inner_tokens());
2044 }
check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident)2045 fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
2046 self.check_ident_token(cx, UnderMacro(false), ident);
2047 }
2048 }
2049
2050 declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
2051
2052 impl ExplicitOutlivesRequirements {
lifetimes_outliving_lifetime<'tcx>( inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)], index: u32, ) -> Vec<ty::Region<'tcx>>2053 fn lifetimes_outliving_lifetime<'tcx>(
2054 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2055 index: u32,
2056 ) -> Vec<ty::Region<'tcx>> {
2057 inferred_outlives
2058 .iter()
2059 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2060 ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a {
2061 ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
2062 _ => None,
2063 },
2064 _ => None,
2065 })
2066 .collect()
2067 }
2068
lifetimes_outliving_type<'tcx>( inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)], index: u32, ) -> Vec<ty::Region<'tcx>>2069 fn lifetimes_outliving_type<'tcx>(
2070 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2071 index: u32,
2072 ) -> Vec<ty::Region<'tcx>> {
2073 inferred_outlives
2074 .iter()
2075 .filter_map(|(pred, _)| match pred.kind().skip_binder() {
2076 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
2077 a.is_param(index).then_some(b)
2078 }
2079 _ => None,
2080 })
2081 .collect()
2082 }
2083
collect_outlived_lifetimes<'tcx>( &self, param: &'tcx hir::GenericParam<'tcx>, tcx: TyCtxt<'tcx>, inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)], ty_generics: &'tcx ty::Generics, ) -> Vec<ty::Region<'tcx>>2084 fn collect_outlived_lifetimes<'tcx>(
2085 &self,
2086 param: &'tcx hir::GenericParam<'tcx>,
2087 tcx: TyCtxt<'tcx>,
2088 inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
2089 ty_generics: &'tcx ty::Generics,
2090 ) -> Vec<ty::Region<'tcx>> {
2091 let index =
2092 ty_generics.param_def_id_to_index[&tcx.hir().local_def_id(param.hir_id).to_def_id()];
2093
2094 match param.kind {
2095 hir::GenericParamKind::Lifetime { .. } => {
2096 Self::lifetimes_outliving_lifetime(inferred_outlives, index)
2097 }
2098 hir::GenericParamKind::Type { .. } => {
2099 Self::lifetimes_outliving_type(inferred_outlives, index)
2100 }
2101 hir::GenericParamKind::Const { .. } => Vec::new(),
2102 }
2103 }
2104
collect_outlives_bound_spans<'tcx>( &self, tcx: TyCtxt<'tcx>, bounds: &hir::GenericBounds<'_>, inferred_outlives: &[ty::Region<'tcx>], infer_static: bool, ) -> Vec<(usize, Span)>2105 fn collect_outlives_bound_spans<'tcx>(
2106 &self,
2107 tcx: TyCtxt<'tcx>,
2108 bounds: &hir::GenericBounds<'_>,
2109 inferred_outlives: &[ty::Region<'tcx>],
2110 infer_static: bool,
2111 ) -> Vec<(usize, Span)> {
2112 use rustc_middle::middle::resolve_lifetime::Region;
2113
2114 bounds
2115 .iter()
2116 .enumerate()
2117 .filter_map(|(i, bound)| {
2118 if let hir::GenericBound::Outlives(lifetime) = bound {
2119 let is_inferred = match tcx.named_region(lifetime.hir_id) {
2120 Some(Region::Static) if infer_static => {
2121 inferred_outlives.iter().any(|r| matches!(r, ty::ReStatic))
2122 }
2123 Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
2124 if let ty::ReEarlyBound(ebr) = r { ebr.index == index } else { false }
2125 }),
2126 _ => false,
2127 };
2128 is_inferred.then_some((i, bound.span()))
2129 } else {
2130 None
2131 }
2132 })
2133 .collect()
2134 }
2135
consolidate_outlives_bound_spans( &self, lo: Span, bounds: &hir::GenericBounds<'_>, bound_spans: Vec<(usize, Span)>, ) -> Vec<Span>2136 fn consolidate_outlives_bound_spans(
2137 &self,
2138 lo: Span,
2139 bounds: &hir::GenericBounds<'_>,
2140 bound_spans: Vec<(usize, Span)>,
2141 ) -> Vec<Span> {
2142 if bounds.is_empty() {
2143 return Vec::new();
2144 }
2145 if bound_spans.len() == bounds.len() {
2146 let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
2147 // If all bounds are inferable, we want to delete the colon, so
2148 // start from just after the parameter (span passed as argument)
2149 vec![lo.to(last_bound_span)]
2150 } else {
2151 let mut merged = Vec::new();
2152 let mut last_merged_i = None;
2153
2154 let mut from_start = true;
2155 for (i, bound_span) in bound_spans {
2156 match last_merged_i {
2157 // If the first bound is inferable, our span should also eat the leading `+`.
2158 None if i == 0 => {
2159 merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
2160 last_merged_i = Some(0);
2161 }
2162 // If consecutive bounds are inferable, merge their spans
2163 Some(h) if i == h + 1 => {
2164 if let Some(tail) = merged.last_mut() {
2165 // Also eat the trailing `+` if the first
2166 // more-than-one bound is inferable
2167 let to_span = if from_start && i < bounds.len() {
2168 bounds[i + 1].span().shrink_to_lo()
2169 } else {
2170 bound_span
2171 };
2172 *tail = tail.to(to_span);
2173 last_merged_i = Some(i);
2174 } else {
2175 bug!("another bound-span visited earlier");
2176 }
2177 }
2178 _ => {
2179 // When we find a non-inferable bound, subsequent inferable bounds
2180 // won't be consecutive from the start (and we'll eat the leading
2181 // `+` rather than the trailing one)
2182 from_start = false;
2183 merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
2184 last_merged_i = Some(i);
2185 }
2186 }
2187 }
2188 merged
2189 }
2190 }
2191 }
2192
2193 impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>)2194 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
2195 use rustc_middle::middle::resolve_lifetime::Region;
2196
2197 let infer_static = cx.tcx.features().infer_static_outlives_requirements;
2198 let def_id = item.def_id;
2199 if let hir::ItemKind::Struct(_, ref hir_generics)
2200 | hir::ItemKind::Enum(_, ref hir_generics)
2201 | hir::ItemKind::Union(_, ref hir_generics) = item.kind
2202 {
2203 let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
2204 if inferred_outlives.is_empty() {
2205 return;
2206 }
2207
2208 let ty_generics = cx.tcx.generics_of(def_id);
2209
2210 let mut bound_count = 0;
2211 let mut lint_spans = Vec::new();
2212
2213 for param in hir_generics.params {
2214 let has_lifetime_bounds = param
2215 .bounds
2216 .iter()
2217 .any(|bound| matches!(bound, hir::GenericBound::Outlives(_)));
2218 if !has_lifetime_bounds {
2219 continue;
2220 }
2221
2222 let relevant_lifetimes =
2223 self.collect_outlived_lifetimes(param, cx.tcx, inferred_outlives, ty_generics);
2224 if relevant_lifetimes.is_empty() {
2225 continue;
2226 }
2227
2228 let bound_spans = self.collect_outlives_bound_spans(
2229 cx.tcx,
2230 ¶m.bounds,
2231 &relevant_lifetimes,
2232 infer_static,
2233 );
2234 bound_count += bound_spans.len();
2235 lint_spans.extend(self.consolidate_outlives_bound_spans(
2236 param.span.shrink_to_hi(),
2237 ¶m.bounds,
2238 bound_spans,
2239 ));
2240 }
2241
2242 let mut where_lint_spans = Vec::new();
2243 let mut dropped_predicate_count = 0;
2244 let num_predicates = hir_generics.where_clause.predicates.len();
2245 for (i, where_predicate) in hir_generics.where_clause.predicates.iter().enumerate() {
2246 let (relevant_lifetimes, bounds, span) = match where_predicate {
2247 hir::WherePredicate::RegionPredicate(predicate) => {
2248 if let Some(Region::EarlyBound(index, ..)) =
2249 cx.tcx.named_region(predicate.lifetime.hir_id)
2250 {
2251 (
2252 Self::lifetimes_outliving_lifetime(inferred_outlives, index),
2253 &predicate.bounds,
2254 predicate.span,
2255 )
2256 } else {
2257 continue;
2258 }
2259 }
2260 hir::WherePredicate::BoundPredicate(predicate) => {
2261 // FIXME we can also infer bounds on associated types,
2262 // and should check for them here.
2263 match predicate.bounded_ty.kind {
2264 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
2265 if let Res::Def(DefKind::TyParam, def_id) = path.res {
2266 let index = ty_generics.param_def_id_to_index[&def_id];
2267 (
2268 Self::lifetimes_outliving_type(inferred_outlives, index),
2269 &predicate.bounds,
2270 predicate.span,
2271 )
2272 } else {
2273 continue;
2274 }
2275 }
2276 _ => {
2277 continue;
2278 }
2279 }
2280 }
2281 _ => continue,
2282 };
2283 if relevant_lifetimes.is_empty() {
2284 continue;
2285 }
2286
2287 let bound_spans = self.collect_outlives_bound_spans(
2288 cx.tcx,
2289 bounds,
2290 &relevant_lifetimes,
2291 infer_static,
2292 );
2293 bound_count += bound_spans.len();
2294
2295 let drop_predicate = bound_spans.len() == bounds.len();
2296 if drop_predicate {
2297 dropped_predicate_count += 1;
2298 }
2299
2300 // If all the bounds on a predicate were inferable and there are
2301 // further predicates, we want to eat the trailing comma.
2302 if drop_predicate && i + 1 < num_predicates {
2303 let next_predicate_span = hir_generics.where_clause.predicates[i + 1].span();
2304 where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
2305 } else {
2306 where_lint_spans.extend(self.consolidate_outlives_bound_spans(
2307 span.shrink_to_lo(),
2308 bounds,
2309 bound_spans,
2310 ));
2311 }
2312 }
2313
2314 // If all predicates are inferable, drop the entire clause
2315 // (including the `where`)
2316 if num_predicates > 0 && dropped_predicate_count == num_predicates {
2317 let where_span = hir_generics
2318 .where_clause
2319 .span()
2320 .expect("span of (nonempty) where clause should exist");
2321 // Extend the where clause back to the closing `>` of the
2322 // generics, except for tuple struct, which have the `where`
2323 // after the fields of the struct.
2324 let full_where_span =
2325 if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
2326 where_span
2327 } else {
2328 hir_generics.span.shrink_to_hi().to(where_span)
2329 };
2330 lint_spans.push(full_where_span);
2331 } else {
2332 lint_spans.extend(where_lint_spans);
2333 }
2334
2335 if !lint_spans.is_empty() {
2336 cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
2337 lint.build("outlives requirements can be inferred")
2338 .multipart_suggestion(
2339 if bound_count == 1 {
2340 "remove this bound"
2341 } else {
2342 "remove these bounds"
2343 },
2344 lint_spans
2345 .into_iter()
2346 .map(|span| (span, "".to_owned()))
2347 .collect::<Vec<_>>(),
2348 Applicability::MachineApplicable,
2349 )
2350 .emit();
2351 });
2352 }
2353 }
2354 }
2355 }
2356
2357 declare_lint! {
2358 /// The `incomplete_features` lint detects unstable features enabled with
2359 /// the [`feature` attribute] that may function improperly in some or all
2360 /// cases.
2361 ///
2362 /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
2363 ///
2364 /// ### Example
2365 ///
2366 /// ```rust
2367 /// #![feature(generic_const_exprs)]
2368 /// ```
2369 ///
2370 /// {{produces}}
2371 ///
2372 /// ### Explanation
2373 ///
2374 /// Although it is encouraged for people to experiment with unstable
2375 /// features, some of them are known to be incomplete or faulty. This lint
2376 /// is a signal that the feature has not yet been finished, and you may
2377 /// experience problems with it.
2378 pub INCOMPLETE_FEATURES,
2379 Warn,
2380 "incomplete features that may function improperly in some or all cases"
2381 }
2382
2383 declare_lint_pass!(
2384 /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
2385 IncompleteFeatures => [INCOMPLETE_FEATURES]
2386 );
2387
2388 impl EarlyLintPass for IncompleteFeatures {
check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate)2389 fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
2390 let features = cx.sess.features_untracked();
2391 features
2392 .declared_lang_features
2393 .iter()
2394 .map(|(name, span, _)| (name, span))
2395 .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
2396 .filter(|(&name, _)| features.incomplete(name))
2397 .for_each(|(&name, &span)| {
2398 cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
2399 let mut builder = lint.build(&format!(
2400 "the feature `{}` is incomplete and may not be safe to use \
2401 and/or cause compiler crashes",
2402 name,
2403 ));
2404 if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
2405 builder.note(&format!(
2406 "see issue #{} <https://github.com/rust-lang/rust/issues/{}> \
2407 for more information",
2408 n, n,
2409 ));
2410 }
2411 if HAS_MIN_FEATURES.contains(&name) {
2412 builder.help(&format!(
2413 "consider using `min_{}` instead, which is more stable and complete",
2414 name,
2415 ));
2416 }
2417 builder.emit();
2418 })
2419 });
2420 }
2421 }
2422
2423 const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
2424
2425 declare_lint! {
2426 /// The `invalid_value` lint detects creating a value that is not valid,
2427 /// such as a null reference.
2428 ///
2429 /// ### Example
2430 ///
2431 /// ```rust,no_run
2432 /// # #![allow(unused)]
2433 /// unsafe {
2434 /// let x: &'static i32 = std::mem::zeroed();
2435 /// }
2436 /// ```
2437 ///
2438 /// {{produces}}
2439 ///
2440 /// ### Explanation
2441 ///
2442 /// In some situations the compiler can detect that the code is creating
2443 /// an invalid value, which should be avoided.
2444 ///
2445 /// In particular, this lint will check for improper use of
2446 /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
2447 /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
2448 /// lint should provide extra information to indicate what the problem is
2449 /// and a possible solution.
2450 ///
2451 /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
2452 /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
2453 /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
2454 /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
2455 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
2456 pub INVALID_VALUE,
2457 Warn,
2458 "an invalid value is being created (such as a null reference)"
2459 }
2460
2461 declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
2462
2463 impl<'tcx> LateLintPass<'tcx> for InvalidValue {
check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>)2464 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
2465 #[derive(Debug, Copy, Clone, PartialEq)]
2466 enum InitKind {
2467 Zeroed,
2468 Uninit,
2469 }
2470
2471 /// Information about why a type cannot be initialized this way.
2472 /// Contains an error message and optionally a span to point at.
2473 type InitError = (String, Option<Span>);
2474
2475 /// Test if this constant is all-0.
2476 fn is_zero(expr: &hir::Expr<'_>) -> bool {
2477 use hir::ExprKind::*;
2478 use rustc_ast::LitKind::*;
2479 match &expr.kind {
2480 Lit(lit) => {
2481 if let Int(i, _) = lit.node {
2482 i == 0
2483 } else {
2484 false
2485 }
2486 }
2487 Tup(tup) => tup.iter().all(is_zero),
2488 _ => false,
2489 }
2490 }
2491
2492 /// Determine if this expression is a "dangerous initialization".
2493 fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
2494 if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
2495 // Find calls to `mem::{uninitialized,zeroed}` methods.
2496 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2497 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2498 match cx.tcx.get_diagnostic_name(def_id) {
2499 Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
2500 Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
2501 Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
2502 _ => {}
2503 }
2504 }
2505 } else if let hir::ExprKind::MethodCall(_, _, ref args, _) = expr.kind {
2506 // Find problematic calls to `MaybeUninit::assume_init`.
2507 let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
2508 if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
2509 // This is a call to *some* method named `assume_init`.
2510 // See if the `self` parameter is one of the dangerous constructors.
2511 if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
2512 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
2513 let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
2514 match cx.tcx.get_diagnostic_name(def_id) {
2515 Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
2516 Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
2517 _ => {}
2518 }
2519 }
2520 }
2521 }
2522 }
2523
2524 None
2525 }
2526
2527 /// Test if this enum has several actually "existing" variants.
2528 /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
2529 fn is_multi_variant(adt: &ty::AdtDef) -> bool {
2530 // As an approximation, we only count dataless variants. Those are definitely inhabited.
2531 let existing_variants = adt.variants.iter().filter(|v| v.fields.is_empty()).count();
2532 existing_variants > 1
2533 }
2534
2535 /// Return `Some` only if we are sure this type does *not*
2536 /// allow zero initialization.
2537 fn ty_find_init_error<'tcx>(
2538 tcx: TyCtxt<'tcx>,
2539 ty: Ty<'tcx>,
2540 init: InitKind,
2541 ) -> Option<InitError> {
2542 use rustc_middle::ty::TyKind::*;
2543 match ty.kind() {
2544 // Primitive types that don't like 0 as a value.
2545 Ref(..) => Some(("references must be non-null".to_string(), None)),
2546 Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
2547 FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
2548 Never => Some(("the `!` type has no valid value".to_string(), None)),
2549 RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
2550 // raw ptr to dyn Trait
2551 {
2552 Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
2553 }
2554 // Primitive types with other constraints.
2555 Bool if init == InitKind::Uninit => {
2556 Some(("booleans must be either `true` or `false`".to_string(), None))
2557 }
2558 Char if init == InitKind::Uninit => {
2559 Some(("characters must be a valid Unicode codepoint".to_string(), None))
2560 }
2561 // Recurse and checks for some compound types.
2562 Adt(adt_def, substs) if !adt_def.is_union() => {
2563 // First check if this ADT has a layout attribute (like `NonNull` and friends).
2564 use std::ops::Bound;
2565 match tcx.layout_scalar_valid_range(adt_def.did) {
2566 // We exploit here that `layout_scalar_valid_range` will never
2567 // return `Bound::Excluded`. (And we have tests checking that we
2568 // handle the attribute correctly.)
2569 (Bound::Included(lo), _) if lo > 0 => {
2570 return Some((format!("`{}` must be non-null", ty), None));
2571 }
2572 (Bound::Included(_), _) | (_, Bound::Included(_))
2573 if init == InitKind::Uninit =>
2574 {
2575 return Some((
2576 format!(
2577 "`{}` must be initialized inside its custom valid range",
2578 ty,
2579 ),
2580 None,
2581 ));
2582 }
2583 _ => {}
2584 }
2585 // Now, recurse.
2586 match adt_def.variants.len() {
2587 0 => Some(("enums with no variants have no valid value".to_string(), None)),
2588 1 => {
2589 // Struct, or enum with exactly one variant.
2590 // Proceed recursively, check all fields.
2591 let variant = &adt_def.variants[VariantIdx::from_u32(0)];
2592 variant.fields.iter().find_map(|field| {
2593 ty_find_init_error(tcx, field.ty(tcx, substs), init).map(
2594 |(mut msg, span)| {
2595 if span.is_none() {
2596 // Point to this field, should be helpful for figuring
2597 // out where the source of the error is.
2598 let span = tcx.def_span(field.did);
2599 write!(
2600 &mut msg,
2601 " (in this {} field)",
2602 adt_def.descr()
2603 )
2604 .unwrap();
2605 (msg, Some(span))
2606 } else {
2607 // Just forward.
2608 (msg, span)
2609 }
2610 },
2611 )
2612 })
2613 }
2614 // Multi-variant enum.
2615 _ => {
2616 if init == InitKind::Uninit && is_multi_variant(adt_def) {
2617 let span = tcx.def_span(adt_def.did);
2618 Some((
2619 "enums have to be initialized to a variant".to_string(),
2620 Some(span),
2621 ))
2622 } else {
2623 // In principle, for zero-initialization we could figure out which variant corresponds
2624 // to tag 0, and check that... but for now we just accept all zero-initializations.
2625 None
2626 }
2627 }
2628 }
2629 }
2630 Tuple(..) => {
2631 // Proceed recursively, check all fields.
2632 ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
2633 }
2634 // Conservative fallback.
2635 _ => None,
2636 }
2637 }
2638
2639 if let Some(init) = is_dangerous_init(cx, expr) {
2640 // This conjures an instance of a type out of nothing,
2641 // using zeroed or uninitialized memory.
2642 // We are extremely conservative with what we warn about.
2643 let conjured_ty = cx.typeck_results().expr_ty(expr);
2644 if let Some((msg, span)) =
2645 with_no_trimmed_paths(|| ty_find_init_error(cx.tcx, conjured_ty, init))
2646 {
2647 cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
2648 let mut err = lint.build(&format!(
2649 "the type `{}` does not permit {}",
2650 conjured_ty,
2651 match init {
2652 InitKind::Zeroed => "zero-initialization",
2653 InitKind::Uninit => "being left uninitialized",
2654 },
2655 ));
2656 err.span_label(expr.span, "this code causes undefined behavior when executed");
2657 err.span_label(
2658 expr.span,
2659 "help: use `MaybeUninit<T>` instead, \
2660 and only call `assume_init` after initialization is done",
2661 );
2662 if let Some(span) = span {
2663 err.span_note(span, &msg);
2664 } else {
2665 err.note(&msg);
2666 }
2667 err.emit();
2668 });
2669 }
2670 }
2671 }
2672 }
2673
2674 declare_lint! {
2675 /// The `clashing_extern_declarations` lint detects when an `extern fn`
2676 /// has been declared with the same name but different types.
2677 ///
2678 /// ### Example
2679 ///
2680 /// ```rust
2681 /// mod m {
2682 /// extern "C" {
2683 /// fn foo();
2684 /// }
2685 /// }
2686 ///
2687 /// extern "C" {
2688 /// fn foo(_: u32);
2689 /// }
2690 /// ```
2691 ///
2692 /// {{produces}}
2693 ///
2694 /// ### Explanation
2695 ///
2696 /// Because two symbols of the same name cannot be resolved to two
2697 /// different functions at link time, and one function cannot possibly
2698 /// have two types, a clashing extern declaration is almost certainly a
2699 /// mistake. Check to make sure that the `extern` definitions are correct
2700 /// and equivalent, and possibly consider unifying them in one location.
2701 ///
2702 /// This lint does not run between crates because a project may have
2703 /// dependencies which both rely on the same extern function, but declare
2704 /// it in a different (but valid) way. For example, they may both declare
2705 /// an opaque type for one or more of the arguments (which would end up
2706 /// distinct types), or use types that are valid conversions in the
2707 /// language the `extern fn` is defined in. In these cases, the compiler
2708 /// can't say that the clashing declaration is incorrect.
2709 pub CLASHING_EXTERN_DECLARATIONS,
2710 Warn,
2711 "detects when an extern fn has been declared with the same name but different types"
2712 }
2713
2714 pub struct ClashingExternDeclarations {
2715 /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
2716 /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
2717 /// the symbol should be reported as a clashing declaration.
2718 // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
2719 // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
2720 seen_decls: FxHashMap<Symbol, HirId>,
2721 }
2722
2723 /// Differentiate between whether the name for an extern decl came from the link_name attribute or
2724 /// just from declaration itself. This is important because we don't want to report clashes on
2725 /// symbol name if they don't actually clash because one or the other links against a symbol with a
2726 /// different name.
2727 enum SymbolName {
2728 /// The name of the symbol + the span of the annotation which introduced the link name.
2729 Link(Symbol, Span),
2730 /// No link name, so just the name of the symbol.
2731 Normal(Symbol),
2732 }
2733
2734 impl SymbolName {
get_name(&self) -> Symbol2735 fn get_name(&self) -> Symbol {
2736 match self {
2737 SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
2738 }
2739 }
2740 }
2741
2742 impl ClashingExternDeclarations {
new() -> Self2743 crate fn new() -> Self {
2744 ClashingExternDeclarations { seen_decls: FxHashMap::default() }
2745 }
2746 /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
2747 /// for the item, return its HirId without updating the set.
insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId>2748 fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
2749 let did = fi.def_id.to_def_id();
2750 let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
2751 let name = Symbol::intern(tcx.symbol_name(instance).name);
2752 if let Some(&hir_id) = self.seen_decls.get(&name) {
2753 // Avoid updating the map with the new entry when we do find a collision. We want to
2754 // make sure we're always pointing to the first definition as the previous declaration.
2755 // This lets us avoid emitting "knock-on" diagnostics.
2756 Some(hir_id)
2757 } else {
2758 self.seen_decls.insert(name, fi.hir_id())
2759 }
2760 }
2761
2762 /// Get the name of the symbol that's linked against for a given extern declaration. That is,
2763 /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
2764 /// symbol's name.
name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName2765 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
2766 if let Some((overridden_link_name, overridden_link_name_span)) =
2767 tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
2768 // FIXME: Instead of searching through the attributes again to get span
2769 // information, we could have codegen_fn_attrs also give span information back for
2770 // where the attribute was defined. However, until this is found to be a
2771 // bottleneck, this does just fine.
2772 (
2773 overridden_link_name,
2774 tcx.get_attrs(fi.def_id.to_def_id())
2775 .iter()
2776 .find(|at| at.has_name(sym::link_name))
2777 .unwrap()
2778 .span,
2779 )
2780 })
2781 {
2782 SymbolName::Link(overridden_link_name, overridden_link_name_span)
2783 } else {
2784 SymbolName::Normal(fi.ident.name)
2785 }
2786 }
2787
2788 /// Checks whether two types are structurally the same enough that the declarations shouldn't
2789 /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
2790 /// 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, ) -> bool2791 fn structurally_same_type<'tcx>(
2792 cx: &LateContext<'tcx>,
2793 a: Ty<'tcx>,
2794 b: Ty<'tcx>,
2795 ckind: CItemKind,
2796 ) -> bool {
2797 fn structurally_same_type_impl<'tcx>(
2798 seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
2799 cx: &LateContext<'tcx>,
2800 a: Ty<'tcx>,
2801 b: Ty<'tcx>,
2802 ckind: CItemKind,
2803 ) -> bool {
2804 debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
2805 let tcx = cx.tcx;
2806
2807 // Given a transparent newtype, reach through and grab the inner
2808 // type unless the newtype makes the type non-null.
2809 let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
2810 let mut ty = ty;
2811 loop {
2812 if let ty::Adt(def, substs) = *ty.kind() {
2813 let is_transparent = def.subst(tcx, substs).repr.transparent();
2814 let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, &def);
2815 debug!(
2816 "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
2817 ty, is_transparent, is_non_null
2818 );
2819 if is_transparent && !is_non_null {
2820 debug_assert!(def.variants.len() == 1);
2821 let v = &def.variants[VariantIdx::new(0)];
2822 ty = transparent_newtype_field(tcx, v)
2823 .expect(
2824 "single-variant transparent structure with zero-sized field",
2825 )
2826 .ty(tcx, substs);
2827 continue;
2828 }
2829 }
2830 debug!("non_transparent_ty -> {:?}", ty);
2831 return ty;
2832 }
2833 };
2834
2835 let a = non_transparent_ty(a);
2836 let b = non_transparent_ty(b);
2837
2838 if !seen_types.insert((a, b)) {
2839 // We've encountered a cycle. There's no point going any further -- the types are
2840 // structurally the same.
2841 return true;
2842 }
2843 let tcx = cx.tcx;
2844 if a == b || rustc_middle::ty::TyS::same_type(a, b) {
2845 // All nominally-same types are structurally same, too.
2846 true
2847 } else {
2848 // Do a full, depth-first comparison between the two.
2849 use rustc_middle::ty::TyKind::*;
2850 let a_kind = a.kind();
2851 let b_kind = b.kind();
2852
2853 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
2854 debug!("compare_layouts({:?}, {:?})", a, b);
2855 let a_layout = &cx.layout_of(a)?.layout.abi;
2856 let b_layout = &cx.layout_of(b)?.layout.abi;
2857 debug!(
2858 "comparing layouts: {:?} == {:?} = {}",
2859 a_layout,
2860 b_layout,
2861 a_layout == b_layout
2862 );
2863 Ok(a_layout == b_layout)
2864 };
2865
2866 #[allow(rustc::usage_of_ty_tykind)]
2867 let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
2868 kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
2869 };
2870
2871 ensure_sufficient_stack(|| {
2872 match (a_kind, b_kind) {
2873 (Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
2874 let a = a.subst(cx.tcx, a_substs);
2875 let b = b.subst(cx.tcx, b_substs);
2876 debug!("Comparing {:?} and {:?}", a, b);
2877
2878 // We can immediately rule out these types as structurally same if
2879 // their layouts differ.
2880 match compare_layouts(a, b) {
2881 Ok(false) => return false,
2882 _ => (), // otherwise, continue onto the full, fields comparison
2883 }
2884
2885 // Grab a flattened representation of all fields.
2886 let a_fields = a_def.variants.iter().flat_map(|v| v.fields.iter());
2887 let b_fields = b_def.variants.iter().flat_map(|v| v.fields.iter());
2888
2889 // Perform a structural comparison for each field.
2890 a_fields.eq_by(
2891 b_fields,
2892 |&ty::FieldDef { did: a_did, .. },
2893 &ty::FieldDef { did: b_did, .. }| {
2894 structurally_same_type_impl(
2895 seen_types,
2896 cx,
2897 tcx.type_of(a_did),
2898 tcx.type_of(b_did),
2899 ckind,
2900 )
2901 },
2902 )
2903 }
2904 (Array(a_ty, a_const), Array(b_ty, b_const)) => {
2905 // For arrays, we also check the constness of the type.
2906 a_const.val == b_const.val
2907 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2908 }
2909 (Slice(a_ty), Slice(b_ty)) => {
2910 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2911 }
2912 (RawPtr(a_tymut), RawPtr(b_tymut)) => {
2913 a_tymut.mutbl == b_tymut.mutbl
2914 && structurally_same_type_impl(
2915 seen_types,
2916 cx,
2917 &a_tymut.ty,
2918 &b_tymut.ty,
2919 ckind,
2920 )
2921 }
2922 (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
2923 // For structural sameness, we don't need the region to be same.
2924 a_mut == b_mut
2925 && structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2926 }
2927 (FnDef(..), FnDef(..)) => {
2928 let a_poly_sig = a.fn_sig(tcx);
2929 let b_poly_sig = b.fn_sig(tcx);
2930
2931 // As we don't compare regions, skip_binder is fine.
2932 let a_sig = a_poly_sig.skip_binder();
2933 let b_sig = b_poly_sig.skip_binder();
2934
2935 (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
2936 == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
2937 && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
2938 structurally_same_type_impl(seen_types, cx, a, b, ckind)
2939 })
2940 && structurally_same_type_impl(
2941 seen_types,
2942 cx,
2943 a_sig.output(),
2944 b_sig.output(),
2945 ckind,
2946 )
2947 }
2948 (Tuple(a_substs), Tuple(b_substs)) => {
2949 a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
2950 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
2951 })
2952 }
2953 // For these, it's not quite as easy to define structural-sameness quite so easily.
2954 // For the purposes of this lint, take the conservative approach and mark them as
2955 // not structurally same.
2956 (Dynamic(..), Dynamic(..))
2957 | (Error(..), Error(..))
2958 | (Closure(..), Closure(..))
2959 | (Generator(..), Generator(..))
2960 | (GeneratorWitness(..), GeneratorWitness(..))
2961 | (Projection(..), Projection(..))
2962 | (Opaque(..), Opaque(..)) => false,
2963
2964 // These definitely should have been caught above.
2965 (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
2966
2967 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
2968 // enum layout optimisation is being applied.
2969 (Adt(..), other_kind) | (other_kind, Adt(..))
2970 if is_primitive_or_pointer(other_kind) =>
2971 {
2972 let (primitive, adt) =
2973 if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
2974 if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
2975 ty == primitive
2976 } else {
2977 compare_layouts(a, b).unwrap_or(false)
2978 }
2979 }
2980 // Otherwise, just compare the layouts. This may fail to lint for some
2981 // incompatible types, but at the very least, will stop reads into
2982 // uninitialised memory.
2983 _ => compare_layouts(a, b).unwrap_or(false),
2984 }
2985 })
2986 }
2987 }
2988 let mut seen_types = FxHashSet::default();
2989 structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
2990 }
2991 }
2992
2993 impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
2994
2995 impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>)2996 fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
2997 trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
2998 if let ForeignItemKind::Fn(..) = this_fi.kind {
2999 let tcx = cx.tcx;
3000 if let Some(existing_hid) = self.insert(tcx, this_fi) {
3001 let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
3002 let this_decl_ty = tcx.type_of(this_fi.def_id);
3003 debug!(
3004 "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
3005 existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
3006 );
3007 // Check that the declarations match.
3008 if !Self::structurally_same_type(
3009 cx,
3010 existing_decl_ty,
3011 this_decl_ty,
3012 CItemKind::Declaration,
3013 ) {
3014 let orig_fi = tcx.hir().expect_foreign_item(existing_hid);
3015 let orig = Self::name_of_extern_decl(tcx, orig_fi);
3016
3017 // We want to ensure that we use spans for both decls that include where the
3018 // name was defined, whether that was from the link_name attribute or not.
3019 let get_relevant_span =
3020 |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
3021 SymbolName::Normal(_) => fi.span,
3022 SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
3023 };
3024 // Finally, emit the diagnostic.
3025 tcx.struct_span_lint_hir(
3026 CLASHING_EXTERN_DECLARATIONS,
3027 this_fi.hir_id(),
3028 get_relevant_span(this_fi),
3029 |lint| {
3030 let mut expected_str = DiagnosticStyledString::new();
3031 expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
3032 let mut found_str = DiagnosticStyledString::new();
3033 found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
3034
3035 lint.build(&format!(
3036 "`{}` redeclare{} with a different signature",
3037 this_fi.ident.name,
3038 if orig.get_name() == this_fi.ident.name {
3039 "d".to_string()
3040 } else {
3041 format!("s `{}`", orig.get_name())
3042 }
3043 ))
3044 .span_label(
3045 get_relevant_span(orig_fi),
3046 &format!("`{}` previously declared here", orig.get_name()),
3047 )
3048 .span_label(
3049 get_relevant_span(this_fi),
3050 "this signature doesn't match the previous declaration",
3051 )
3052 .note_expected_found(&"", expected_str, &"", found_str)
3053 .emit()
3054 },
3055 );
3056 }
3057 }
3058 }
3059 }
3060 }
3061
3062 declare_lint! {
3063 /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
3064 /// which causes [undefined behavior].
3065 ///
3066 /// ### Example
3067 ///
3068 /// ```rust,no_run
3069 /// # #![allow(unused)]
3070 /// use std::ptr;
3071 /// unsafe {
3072 /// let x = &*ptr::null::<i32>();
3073 /// let x = ptr::addr_of!(*ptr::null::<i32>());
3074 /// let x = *(0 as *const i32);
3075 /// }
3076 /// ```
3077 ///
3078 /// {{produces}}
3079 ///
3080 /// ### Explanation
3081 ///
3082 /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
3083 /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
3084 ///
3085 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
3086 pub DEREF_NULLPTR,
3087 Warn,
3088 "detects when an null pointer is dereferenced"
3089 }
3090
3091 declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
3092
3093 impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>)3094 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
3095 /// test if expression is a null ptr
3096 fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
3097 match &expr.kind {
3098 rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
3099 if let rustc_hir::TyKind::Ptr(_) = ty.kind {
3100 return is_zero(expr) || is_null_ptr(cx, expr);
3101 }
3102 }
3103 // check for call to `core::ptr::null` or `core::ptr::null_mut`
3104 rustc_hir::ExprKind::Call(ref path, _) => {
3105 if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
3106 if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
3107 return matches!(
3108 cx.tcx.get_diagnostic_name(def_id),
3109 Some(sym::ptr_null | sym::ptr_null_mut)
3110 );
3111 }
3112 }
3113 }
3114 _ => {}
3115 }
3116 false
3117 }
3118
3119 /// test if expression is the literal `0`
3120 fn is_zero(expr: &hir::Expr<'_>) -> bool {
3121 match &expr.kind {
3122 rustc_hir::ExprKind::Lit(ref lit) => {
3123 if let LitKind::Int(a, _) = lit.node {
3124 return a == 0;
3125 }
3126 }
3127 _ => {}
3128 }
3129 false
3130 }
3131
3132 if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
3133 if is_null_ptr(cx, expr_deref) {
3134 cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
3135 let mut err = lint.build("dereferencing a null pointer");
3136 err.span_label(expr.span, "this code causes undefined behavior when executed");
3137 err.emit();
3138 });
3139 }
3140 }
3141 }
3142 }
3143
3144 declare_lint! {
3145 /// The `named_asm_labels` lint detects the use of named labels in the
3146 /// inline `asm!` macro.
3147 ///
3148 /// ### Example
3149 ///
3150 /// ```rust,compile_fail
3151 /// #![feature(asm)]
3152 /// fn main() {
3153 /// unsafe {
3154 /// asm!("foo: bar");
3155 /// }
3156 /// }
3157 /// ```
3158 ///
3159 /// {{produces}}
3160 ///
3161 /// ### Explanation
3162 ///
3163 /// LLVM is allowed to duplicate inline assembly blocks for any
3164 /// reason, for example when it is in a function that gets inlined. Because
3165 /// of this, GNU assembler [local labels] *must* be used instead of labels
3166 /// with a name. Using named labels might cause assembler or linker errors.
3167 ///
3168 /// See the [unstable book] for more details.
3169 ///
3170 /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
3171 /// [unstable book]: https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels
3172 pub NAMED_ASM_LABELS,
3173 Deny,
3174 "named labels in inline assembly",
3175 }
3176
3177 declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
3178
3179 impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>)3180 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
3181 if let hir::Expr {
3182 kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
3183 ..
3184 } = expr
3185 {
3186 for (template_sym, template_snippet, template_span) in template_strs.iter() {
3187 let template_str = &template_sym.as_str();
3188 let find_label_span = |needle: &str| -> Option<Span> {
3189 if let Some(template_snippet) = template_snippet {
3190 let snippet = template_snippet.as_str();
3191 if let Some(pos) = snippet.find(needle) {
3192 let end = pos
3193 + snippet[pos..]
3194 .find(|c| c == ':')
3195 .unwrap_or(snippet[pos..].len() - 1);
3196 let inner = InnerSpan::new(pos, end);
3197 return Some(template_span.from_inner(inner));
3198 }
3199 }
3200
3201 None
3202 };
3203
3204 let mut found_labels = Vec::new();
3205
3206 // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
3207 let statements = template_str.split(|c| matches!(c, '\n' | ';'));
3208 for statement in statements {
3209 // If there's a comment, trim it from the statement
3210 let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
3211 let mut start_idx = 0;
3212 for (idx, _) in statement.match_indices(':') {
3213 let possible_label = statement[start_idx..idx].trim();
3214 let mut chars = possible_label.chars();
3215 if let Some(c) = chars.next() {
3216 // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
3217 if (c.is_alphabetic() || matches!(c, '.' | '_'))
3218 && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
3219 {
3220 found_labels.push(possible_label);
3221 } else {
3222 // If we encounter a non-label, there cannot be any further labels, so stop checking
3223 break;
3224 }
3225 } else {
3226 // Empty string means a leading ':' in this section, which is not a label
3227 break;
3228 }
3229
3230 start_idx = idx + 1;
3231 }
3232 }
3233
3234 debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
3235
3236 if found_labels.len() > 0 {
3237 let spans = found_labels
3238 .into_iter()
3239 .filter_map(|label| find_label_span(label))
3240 .collect::<Vec<Span>>();
3241 // If there were labels but we couldn't find a span, combine the warnings and use the template span
3242 let target_spans: MultiSpan =
3243 if spans.len() > 0 { spans.into() } else { (*template_span).into() };
3244
3245 cx.lookup_with_diagnostics(
3246 NAMED_ASM_LABELS,
3247 Some(target_spans),
3248 |diag| {
3249 let mut err =
3250 diag.build("avoid using named labels in inline assembly");
3251 err.emit();
3252 },
3253 BuiltinLintDiagnostics::NamedAsmLabel(
3254 "only local labels of the form `<number>:` should be used in inline asm"
3255 .to_string(),
3256 ),
3257 );
3258 }
3259 }
3260 }
3261 }
3262 }
3263