1 use clippy_utils::attrs::is_doc_hidden;
2 use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_note, span_lint_and_then};
3 use clippy_utils::macros::{is_panic, root_macro_call_first_node};
4 use clippy_utils::source::{first_line_of_span, snippet_with_applicability};
5 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
6 use clippy_utils::{is_entrypoint_fn, method_chain_args, return_ty};
7 use if_chain::if_chain;
8 use itertools::Itertools;
9 use rustc_ast::ast::{Async, AttrKind, Attribute, Fn, FnRetTy, ItemKind};
10 use rustc_ast::token::CommentKind;
11 use rustc_data_structures::fx::FxHashSet;
12 use rustc_data_structures::sync::Lrc;
13 use rustc_errors::emitter::EmitterWriter;
14 use rustc_errors::{Applicability, Handler, MultiSpan, SuggestionStyle};
16 use rustc_hir::intravisit::{self, Visitor};
17 use rustc_hir::{AnonConst, Expr};
18 use rustc_lint::{LateContext, LateLintPass};
19 use rustc_middle::hir::nested_filter;
20 use rustc_middle::lint::in_external_macro;
22 use rustc_parse::maybe_new_parser_from_source_str;
23 use rustc_parse::parser::ForceCollect;
24 use rustc_session::parse::ParseSess;
25 use rustc_session::{declare_tool_lint, impl_lint_pass};
26 use rustc_span::def_id::LocalDefId;
27 use rustc_span::edition::Edition;
28 use rustc_span::source_map::{BytePos, FilePathMapping, SourceMap, Span};
29 use rustc_span::{sym, FileName, Pos};
35 declare_clippy_lint! {
37 /// Checks for the presence of `_`, `::` or camel-case words
38 /// outside ticks in documentation.
40 /// ### Why is this bad?
41 /// *Rustdoc* supports markdown formatting, `_`, `::` and
42 /// camel-case probably indicates some code which should be included between
43 /// ticks. `_` can also be used for emphasis in markdown, this lint tries to
46 /// ### Known problems
47 /// Lots of bad docs won’t be fixed, what the lint checks
48 /// for is limited, and there are still false positives. HTML elements and their
49 /// content are not linted.
51 /// In addition, when writing documentation comments, including `[]` brackets
52 /// inside a link text would trip the parser. Therefore, documenting link with
53 /// `[`SmallVec<[T; INLINE_CAPACITY]>`]` and then [`SmallVec<[T; INLINE_CAPACITY]>`]: SmallVec
58 /// /// Do something with the foo_bar parameter. See also
59 /// /// that::other::module::foo.
60 /// // ^ `foo_bar` and `that::other::module::foo` should be ticked.
61 /// fn doit(foo_bar: usize) {}
65 /// // Link text with `[]` brackets should be written as following:
66 /// /// Consume the array and return the inner
67 /// /// [`SmallVec<[T; INLINE_CAPACITY]>`][SmallVec].
68 /// /// [SmallVec]: SmallVec
71 #[clippy::version = "pre 1.29.0"]
74 "presence of `_`, `::` or camel-case outside backticks in documentation"
77 declare_clippy_lint! {
79 /// Checks for the doc comments of publicly visible
80 /// unsafe functions and warns if there is no `# Safety` section.
82 /// ### Why is this bad?
83 /// Unsafe functions should document their safety
84 /// preconditions, so that users can be sure they are using them safely.
88 ///# type Universe = ();
89 /// /// This function should really be documented
90 /// pub unsafe fn start_apocalypse(u: &mut Universe) {
95 /// At least write a line about safety:
98 ///# type Universe = ();
101 /// /// This function should not be called before the horsemen are ready.
102 /// pub unsafe fn start_apocalypse(u: &mut Universe) {
103 /// unimplemented!();
106 #[clippy::version = "1.39.0"]
107 pub MISSING_SAFETY_DOC,
109 "`pub unsafe fn` without `# Safety` docs"
112 declare_clippy_lint! {
114 /// Checks the doc comments of publicly visible functions that
115 /// return a `Result` type and warns if there is no `# Errors` section.
117 /// ### Why is this bad?
118 /// Documenting the type of errors that can be returned from a
119 /// function can help callers write code to handle the errors appropriately.
122 /// Since the following function returns a `Result` it has an `# Errors` section in
129 /// /// Will return `Err` if `filename` does not exist or the user does not have
130 /// /// permission to read it.
131 /// pub fn read(filename: String) -> io::Result<String> {
132 /// unimplemented!();
135 #[clippy::version = "1.41.0"]
136 pub MISSING_ERRORS_DOC,
138 "`pub fn` returns `Result` without `# Errors` in doc comment"
141 declare_clippy_lint! {
143 /// Checks the doc comments of publicly visible functions that
144 /// may panic and warns if there is no `# Panics` section.
146 /// ### Why is this bad?
147 /// Documenting the scenarios in which panicking occurs
148 /// can help callers who do not want to panic to avoid those situations.
151 /// Since the following function may panic it has a `# Panics` section in
157 /// /// Will panic if y is 0
158 /// pub fn divide_by(x: i32, y: i32) -> i32 {
160 /// panic!("Cannot divide by 0")
166 #[clippy::version = "1.51.0"]
167 pub MISSING_PANICS_DOC,
169 "`pub fn` may panic without `# Panics` in doc comment"
172 declare_clippy_lint! {
174 /// Checks for `fn main() { .. }` in doctests
176 /// ### Why is this bad?
177 /// The test can be shorter (and likely more readable)
178 /// if the `fn main()` is left implicit.
182 /// /// An example of a doctest with a `main()` function
188 /// /// // this needs not be in an `fn`
191 /// fn needless_main() {
192 /// unimplemented!();
195 #[clippy::version = "1.40.0"]
196 pub NEEDLESS_DOCTEST_MAIN,
198 "presence of `fn main() {` in code examples"
201 #[expect(clippy::module_name_repetitions)]
203 pub struct DocMarkdown {
204 valid_idents: FxHashSet<String>,
209 pub fn new(valid_idents: FxHashSet<String>) -> Self {
212 in_trait_impl: false,
217 impl_lint_pass!(DocMarkdown =>
218 [DOC_MARKDOWN, MISSING_SAFETY_DOC, MISSING_ERRORS_DOC, MISSING_PANICS_DOC, NEEDLESS_DOCTEST_MAIN]
221 impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
222 fn check_crate(&mut self, cx: &LateContext<'tcx>) {
223 let attrs = cx.tcx.hir().attrs(hir::CRATE_HIR_ID);
224 check_attrs(cx, &self.valid_idents, attrs);
227 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
228 let attrs = cx.tcx.hir().attrs(item.hir_id());
229 let headers = check_attrs(cx, &self.valid_idents, attrs);
231 hir::ItemKind::Fn(ref sig, _, body_id) => {
232 if !(is_entrypoint_fn(cx, item.def_id.to_def_id()) || in_external_macro(cx.tcx.sess, item.span)) {
233 let body = cx.tcx.hir().body(body_id);
234 let mut fpu = FindPanicUnwrap {
236 typeck_results: cx.tcx.typeck(item.def_id),
239 fpu.visit_expr(body.value);
240 lint_for_missing_headers(cx, item.def_id, item.span, sig, headers, Some(body_id), fpu.panic_span);
243 hir::ItemKind::Impl(impl_) => {
244 self.in_trait_impl = impl_.of_trait.is_some();
246 hir::ItemKind::Trait(_, unsafety, ..) => {
247 if !headers.safety && unsafety == hir::Unsafety::Unsafe {
252 "docs for unsafe trait missing `# Safety` section",
260 fn check_item_post(&mut self, _cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
261 if let hir::ItemKind::Impl { .. } = item.kind {
262 self.in_trait_impl = false;
266 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
267 let attrs = cx.tcx.hir().attrs(item.hir_id());
268 let headers = check_attrs(cx, &self.valid_idents, attrs);
269 if let hir::TraitItemKind::Fn(ref sig, ..) = item.kind {
270 if !in_external_macro(cx.tcx.sess, item.span) {
271 lint_for_missing_headers(cx, item.def_id, item.span, sig, headers, None, None);
276 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
277 let attrs = cx.tcx.hir().attrs(item.hir_id());
278 let headers = check_attrs(cx, &self.valid_idents, attrs);
279 if self.in_trait_impl || in_external_macro(cx.tcx.sess, item.span) {
282 if let hir::ImplItemKind::Fn(ref sig, body_id) = item.kind {
283 let body = cx.tcx.hir().body(body_id);
284 let mut fpu = FindPanicUnwrap {
286 typeck_results: cx.tcx.typeck(item.def_id),
289 fpu.visit_expr(body.value);
290 lint_for_missing_headers(cx, item.def_id, item.span, sig, headers, Some(body_id), fpu.panic_span);
295 fn lint_for_missing_headers<'tcx>(
296 cx: &LateContext<'tcx>,
298 span: impl Into<MultiSpan> + Copy,
299 sig: &hir::FnSig<'_>,
301 body_id: Option<hir::BodyId>,
302 panic_span: Option<Span>,
304 if !cx.access_levels.is_exported(def_id) {
305 return; // Private functions do not require doc comments
308 // do not lint if any parent has `#[doc(hidden)]` attribute (#7347)
312 .parent_iter(cx.tcx.hir().local_def_id_to_hir_id(def_id))
313 .any(|(id, _node)| is_doc_hidden(cx.tcx.hir().attrs(id)))
318 if !headers.safety && sig.header.unsafety == hir::Unsafety::Unsafe {
323 "unsafe function's docs miss `# Safety` section",
326 if !headers.panics && panic_span.is_some() {
331 "docs for function which may panic missing `# Panics` section",
333 "first possible panic found here",
337 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
338 if is_type_diagnostic_item(cx, return_ty(cx, hir_id), sym::Result) {
343 "docs for function returning `Result` missing `# Errors` section",
347 if let Some(body_id) = body_id;
348 if let Some(future) = cx.tcx.lang_items().future_trait();
349 let typeck = cx.tcx.typeck_body(body_id);
350 let body = cx.tcx.hir().body(body_id);
351 let ret_ty = typeck.expr_ty(body.value);
352 if implements_trait(cx, ret_ty, future, &[]);
353 if let ty::Opaque(_, subs) = ret_ty.kind();
354 if let Some(gen) = subs.types().next();
355 if let ty::Generator(_, subs, _) = gen.kind();
356 if is_type_diagnostic_item(cx, subs.as_generator().return_ty(), sym::Result);
362 "docs for function returning `Result` missing `# Errors` section",
370 /// Cleanup documentation decoration.
372 /// We can't use `rustc_ast::attr::AttributeMethods::with_desugared_doc` or
373 /// `rustc_ast::parse::lexer::comments::strip_doc_comment_decoration` because we
374 /// need to keep track of
375 /// the spans but this function is inspired from the later.
376 #[expect(clippy::cast_possible_truncation)]
378 pub fn strip_doc_comment_decoration(doc: &str, comment_kind: CommentKind, span: Span) -> (String, Vec<(usize, Span)>) {
379 // one-line comments lose their prefix
380 if comment_kind == CommentKind::Line {
381 let mut doc = doc.to_owned();
384 // +3 skips the opening delimiter
385 return (doc, vec![(len, span.with_lo(span.lo() + BytePos(3)))]);
388 let mut sizes = vec![];
389 let mut contains_initial_stars = false;
390 for line in doc.lines() {
391 let offset = line.as_ptr() as usize - doc.as_ptr() as usize;
392 debug_assert_eq!(offset as u32 as usize, offset);
393 contains_initial_stars |= line.trim_start().starts_with('*');
394 // +1 adds the newline, +3 skips the opening delimiter
395 sizes.push((line.len() + 1, span.with_lo(span.lo() + BytePos(3 + offset as u32))));
397 if !contains_initial_stars {
398 return (doc.to_string(), sizes);
400 // remove the initial '*'s if any
401 let mut no_stars = String::with_capacity(doc.len());
402 for line in doc.lines() {
403 let mut chars = line.chars();
404 for c in &mut chars {
405 if c.is_whitespace() {
408 no_stars.push(if c == '*' { ' ' } else { c });
412 no_stars.push_str(chars.as_str());
419 #[derive(Copy, Clone)]
426 fn check_attrs<'a>(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, attrs: &'a [Attribute]) -> DocHeaders {
427 use pulldown_cmark::{BrokenLink, CowStr, Options};
428 /// We don't want the parser to choke on intra doc links. Since we don't
429 /// actually care about rendering them, just pretend that all broken links are
430 /// point to a fake address.
431 #[expect(clippy::unnecessary_wraps)] // we're following a type signature
432 fn fake_broken_link_callback<'a>(_: BrokenLink<'_>) -> Option<(CowStr<'a>, CowStr<'a>)> {
433 Some(("fake".into(), "fake".into()))
436 let mut doc = String::new();
437 let mut spans = vec![];
440 if let AttrKind::DocComment(comment_kind, comment) = attr.kind {
441 let (comment, current_spans) = strip_doc_comment_decoration(comment.as_str(), comment_kind, attr.span);
442 spans.extend_from_slice(¤t_spans);
443 doc.push_str(&comment);
444 } else if attr.has_name(sym::doc) {
445 // ignore mix of sugared and non-sugared doc
446 // don't trigger the safety or errors check
456 for &mut (ref mut offset, _) in &mut spans {
457 let offset_copy = *offset;
459 current += offset_copy;
470 let mut cb = fake_broken_link_callback;
473 pulldown_cmark::Parser::new_with_broken_link_callback(&doc, Options::empty(), Some(&mut cb)).into_offset_iter();
474 // Iterate over all `Events` and combine consecutive events into one
475 let events = parser.coalesce(|previous, current| {
476 use pulldown_cmark::Event::Text;
478 let previous_range = previous.1;
479 let current_range = current.1;
481 match (previous.0, current.0) {
482 (Text(previous), Text(current)) => {
483 let mut previous = previous.to_string();
484 previous.push_str(¤t);
485 Ok((Text(previous.into()), previous_range))
487 (previous, current) => Err(((previous, previous_range), (current, current_range))),
490 check_doc(cx, valid_idents, events, &spans)
493 const RUST_CODE: &[&str] = &["rust", "no_run", "should_panic", "compile_fail"];
495 fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize>)>>(
496 cx: &LateContext<'_>,
497 valid_idents: &FxHashSet<String>,
499 spans: &[(usize, Span)],
501 // true if a safety header was found
502 use pulldown_cmark::Event::{
503 Code, End, FootnoteReference, HardBreak, Html, Rule, SoftBreak, Start, TaskListMarker, Text,
505 use pulldown_cmark::Tag::{CodeBlock, Heading, Item, Link, Paragraph};
506 use pulldown_cmark::{CodeBlockKind, CowStr};
508 let mut headers = DocHeaders {
513 let mut in_code = false;
514 let mut in_link = None;
515 let mut in_heading = false;
516 let mut is_rust = false;
517 let mut edition = None;
518 let mut ticks_unbalanced = false;
519 let mut text_to_check: Vec<(CowStr<'_>, Span)> = Vec::new();
520 let mut paragraph_span = spans.get(0).expect("function isn't called if doc comment is empty").1;
521 for (event, range) in events {
523 Start(CodeBlock(ref kind)) => {
525 if let CodeBlockKind::Fenced(lang) = kind {
526 for item in lang.split(',') {
527 if item == "ignore" {
531 if let Some(stripped) = item.strip_prefix("edition") {
533 edition = stripped.parse::<Edition>().ok();
534 } else if item.is_empty() || RUST_CODE.contains(&item) {
540 End(CodeBlock(_)) => {
544 Start(Link(_, url, _)) => in_link = Some(url),
545 End(Link(..)) => in_link = None,
546 Start(Heading(_, _, _) | Paragraph | Item) => {
547 if let Start(Heading(_, _, _)) = event {
550 ticks_unbalanced = false;
551 let (_, span) = get_current_span(spans, range.start);
552 paragraph_span = first_line_of_span(cx, span);
554 End(Heading(_, _, _) | Paragraph | Item) => {
555 if let End(Heading(_, _, _)) = event {
558 if ticks_unbalanced {
563 "backticks are unbalanced",
565 "a backtick may be missing a pair",
568 for (text, span) in text_to_check {
569 check_text(cx, valid_idents, &text, span);
572 text_to_check = Vec::new();
574 Start(_tag) | End(_tag) => (), // We don't care about other tags
575 Html(_html) => (), // HTML is weird, just ignore it
576 SoftBreak | HardBreak | TaskListMarker(_) | Code(_) | Rule => (),
577 FootnoteReference(text) | Text(text) => {
578 let (begin, span) = get_current_span(spans, range.start);
579 paragraph_span = paragraph_span.with_hi(span.hi());
580 ticks_unbalanced |= text.contains('`') && !in_code;
581 if Some(&text) == in_link.as_ref() || ticks_unbalanced {
582 // Probably a link of the form `<http://example.com>`
583 // Which are represented as a link to "http://example.com" with
584 // text "http://example.com" by pulldown-cmark
587 let trimmed_text = text.trim();
588 headers.safety |= in_heading && trimmed_text == "Safety";
589 headers.safety |= in_heading && trimmed_text == "Implementation safety";
590 headers.safety |= in_heading && trimmed_text == "Implementation Safety";
591 headers.errors |= in_heading && trimmed_text == "Errors";
592 headers.panics |= in_heading && trimmed_text == "Panics";
595 let edition = edition.unwrap_or_else(|| cx.tcx.sess.edition());
596 check_code(cx, &text, edition, span);
599 // Adjust for the beginning of the current `Event`
600 let span = span.with_lo(span.lo() + BytePos::from_usize(range.start - begin));
601 text_to_check.push((text, span));
609 fn get_current_span(spans: &[(usize, Span)], idx: usize) -> (usize, Span) {
610 let index = match spans.binary_search_by(|c| c.0.cmp(&idx)) {
617 fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
618 fn has_needless_main(code: String, edition: Edition) -> bool {
619 rustc_driver::catch_fatal_errors(|| {
620 rustc_span::create_session_globals_then(edition, || {
621 let filename = FileName::anon_source_code(&code);
623 let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
624 let fallback_bundle =
625 rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
626 let emitter = EmitterWriter::new(
627 Box::new(io::sink()),
637 let handler = Handler::with_emitter(false, None, Box::new(emitter));
638 let sess = ParseSess::with_span_handler(handler, sm);
640 let mut parser = match maybe_new_parser_from_source_str(&sess, filename, code) {
648 let mut relevant_main_found = false;
650 match parser.parse_item(ForceCollect::No) {
651 Ok(Some(item)) => match &item.kind {
652 ItemKind::Fn(box Fn {
653 sig, body: Some(block), ..
654 }) if item.ident.name == sym::main => {
655 let is_async = matches!(sig.header.asyncness, Async::Yes { .. });
656 let returns_nothing = match &sig.decl.output {
657 FnRetTy::Default(..) => true,
658 FnRetTy::Ty(ty) if ty.kind.is_unit() => true,
659 FnRetTy::Ty(_) => false,
662 if returns_nothing && !is_async && !block.stmts.is_empty() {
663 // This main function should be linted, but only if there are no other functions
664 relevant_main_found = true;
666 // This main function should not be linted, we're done
670 // Tests with one of these items are ignored
672 | ItemKind::Const(..)
673 | ItemKind::ExternCrate(..)
674 | ItemKind::ForeignMod(..)
675 // Another function was found; this case is ignored
676 | ItemKind::Fn(..) => return false,
694 // Because of the global session, we need to create a new session in a different thread with
695 // the edition we need.
696 let text = text.to_owned();
697 if thread::spawn(move || has_needless_main(text, edition))
699 .expect("thread::spawn failed")
701 span_lint(cx, NEEDLESS_DOCTEST_MAIN, span, "needless `fn main` in doctest");
705 fn check_text(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, text: &str, span: Span) {
706 for word in text.split(|c: char| c.is_whitespace() || c == '\'') {
707 // Trim punctuation as in `some comment (see foo::bar).`
709 // Or even as in `_foo bar_` which is emphasized. Also preserve `::` as a prefix/suffix.
710 let mut word = word.trim_matches(|c: char| !c.is_alphanumeric() && c != ':');
712 // Remove leading or trailing single `:` which may be part of a sentence.
713 if word.starts_with(':') && !word.starts_with("::") {
714 word = word.trim_start_matches(':');
716 if word.ends_with(':') && !word.ends_with("::") {
717 word = word.trim_end_matches(':');
720 if valid_idents.contains(word) || word.chars().all(|c| c == ':') {
724 // Adjust for the current word
725 let offset = word.as_ptr() as usize - text.as_ptr() as usize;
726 let span = Span::new(
727 span.lo() + BytePos::from_usize(offset),
728 span.lo() + BytePos::from_usize(offset + word.len()),
733 check_word(cx, word, span);
737 fn check_word(cx: &LateContext<'_>, word: &str, span: Span) {
738 /// Checks if a string is camel-case, i.e., contains at least two uppercase
739 /// letters (`Clippy` is ok) and one lower-case letter (`NASA` is ok).
740 /// Plurals are also excluded (`IDs` is ok).
741 fn is_camel_case(s: &str) -> bool {
742 if s.starts_with(|c: char| c.is_ascii_digit()) {
746 let s = s.strip_suffix('s').unwrap_or(s);
748 s.chars().all(char::is_alphanumeric)
749 && s.chars().filter(|&c| c.is_uppercase()).take(2).count() > 1
750 && s.chars().filter(|&c| c.is_lowercase()).take(1).count() > 0
753 fn has_underscore(s: &str) -> bool {
754 s != "_" && !s.contains("\\_") && s.contains('_')
757 fn has_hyphen(s: &str) -> bool {
758 s != "-" && s.contains('-')
761 if let Ok(url) = Url::parse(word) {
762 // try to get around the fact that `foo::bar` parses as a valid URL
763 if !url.cannot_be_a_base() {
768 "you should put bare URLs between `<`/`>` or make a proper Markdown link",
775 // We assume that mixed-case words are not meant to be put inside backticks. (Issue #2343)
776 if has_underscore(word) && has_hyphen(word) {
780 if has_underscore(word) || word.contains("::") || is_camel_case(word) {
781 let mut applicability = Applicability::MachineApplicable;
787 "item in documentation is missing backticks",
789 let snippet = snippet_with_applicability(cx, span, "..", &mut applicability);
790 diag.span_suggestion_with_style(
793 format!("`{}`", snippet),
795 // always show the suggestion in a separate line, since the
796 // inline presentation adds another pair of backticks
797 SuggestionStyle::ShowAlways,
804 struct FindPanicUnwrap<'a, 'tcx> {
805 cx: &'a LateContext<'tcx>,
806 panic_span: Option<Span>,
807 typeck_results: &'tcx ty::TypeckResults<'tcx>,
810 impl<'a, 'tcx> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
811 type NestedFilter = nested_filter::OnlyBodies;
813 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
814 if self.panic_span.is_some() {
818 if let Some(macro_call) = root_macro_call_first_node(self.cx, expr) {
819 if is_panic(self.cx, macro_call.def_id)
821 self.cx.tcx.item_name(macro_call.def_id).as_str(),
822 "assert" | "assert_eq" | "assert_ne" | "todo"
825 self.panic_span = Some(macro_call.span);
829 // check for `unwrap`
830 if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
831 let receiver_ty = self.typeck_results.expr_ty(arglists[0].0).peel_refs();
832 if is_type_diagnostic_item(self.cx, receiver_ty, sym::Option)
833 || is_type_diagnostic_item(self.cx, receiver_ty, sym::Result)
835 self.panic_span = Some(expr.span);
839 // and check sub-expressions
840 intravisit::walk_expr(self, expr);
843 // Panics in const blocks will cause compilation to fail.
844 fn visit_anon_const(&mut self, _: &'tcx AnonConst) {}
846 fn nested_visit_map(&mut self) -> Self::Map {