src/tools/clippy/clippy_lints/src/doc.rs

   1 use clippy_utils::diagnostics::{span_lint, span_lint_and_note};
   2 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
   3 use clippy_utils::{is_entrypoint_fn, is_expn_of, match_panic_def_id, method_chain_args, return_ty};
   4 use if_chain::if_chain;
   5 use itertools::Itertools;
   6 use rustc_ast::ast::{Async, AttrKind, Attribute, FnKind, FnRetTy, ItemKind};
   7 use rustc_ast::token::CommentKind;
   8 use rustc_data_structures::fx::FxHashSet;
   9 use rustc_data_structures::sync::Lrc;
  10 use rustc_errors::emitter::EmitterWriter;
  11 use rustc_errors::Handler;
  12 use rustc_hir as hir;
  13 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  14 use rustc_hir::{AnonConst, Expr, ExprKind, QPath};
  15 use rustc_lint::{LateContext, LateLintPass};
  16 use rustc_middle::hir::map::Map;
  17 use rustc_middle::lint::in_external_macro;
  18 use rustc_middle::ty;
  19 use rustc_parse::maybe_new_parser_from_source_str;
  20 use rustc_parse::parser::ForceCollect;
  21 use rustc_session::parse::ParseSess;
  22 use rustc_session::{declare_tool_lint, impl_lint_pass};
  23 use rustc_span::edition::Edition;
  24 use rustc_span::source_map::{BytePos, FilePathMapping, MultiSpan, SourceMap, Span};
  25 use rustc_span::{sym, FileName, Pos};
  26 use std::io;
  27 use std::ops::Range;
  28 use url::Url;
  29
  30 declare_clippy_lint! {
  31     /// **What it does:** Checks for the presence of `_`, `::` or camel-case words
  32     /// outside ticks in documentation.
  33     ///
  34     /// **Why is this bad?** *Rustdoc* supports markdown formatting, `_`, `::` and
  35     /// camel-case probably indicates some code which should be included between
  36     /// ticks. `_` can also be used for emphasis in markdown, this lint tries to
  37     /// consider that.
  38     ///
  39     /// **Known problems:** Lots of bad docs won’t be fixed, what the lint checks
  40     /// for is limited, and there are still false positives.
  41     ///
  42     /// In addition, when writing documentation comments, including `[]` brackets
  43     /// inside a link text would trip the parser. Therfore, documenting link with
  44     /// `[`SmallVec<[T; INLINE_CAPACITY]>`]` and then [`SmallVec<[T; INLINE_CAPACITY]>`]: SmallVec
  45     /// would fail.
  46     ///
  47     /// **Examples:**
  48     /// ```rust
  49     /// /// Do something with the foo_bar parameter. See also
  50     /// /// that::other::module::foo.
  51     /// // ^ `foo_bar` and `that::other::module::foo` should be ticked.
  52     /// fn doit(foo_bar: usize) {}
  53     /// ```
  54     ///
  55     /// ```rust
  56     /// // Link text with `[]` brackets should be written as following:
  57     /// /// Consume the array and return the inner
  58     /// /// [`SmallVec<[T; INLINE_CAPACITY]>`][SmallVec].
  59     /// /// [SmallVec]: SmallVec
  60     /// fn main() {}
  61     /// ```
  62     pub DOC_MARKDOWN,
  63     pedantic,
  64     "presence of `_`, `::` or camel-case outside backticks in documentation"
  65 }
  66
  67 declare_clippy_lint! {
  68     /// **What it does:** Checks for the doc comments of publicly visible
  69     /// unsafe functions and warns if there is no `# Safety` section.
  70     ///
  71     /// **Why is this bad?** Unsafe functions should document their safety
  72     /// preconditions, so that users can be sure they are using them safely.
  73     ///
  74     /// **Known problems:** None.
  75     ///
  76     /// **Examples:**
  77     /// ```rust
  78     ///# type Universe = ();
  79     /// /// This function should really be documented
  80     /// pub unsafe fn start_apocalypse(u: &mut Universe) {
  81     ///     unimplemented!();
  82     /// }
  83     /// ```
  84     ///
  85     /// At least write a line about safety:
  86     ///
  87     /// ```rust
  88     ///# type Universe = ();
  89     /// /// # Safety
  90     /// ///
  91     /// /// This function should not be called before the horsemen are ready.
  92     /// pub unsafe fn start_apocalypse(u: &mut Universe) {
  93     ///     unimplemented!();
  94     /// }
  95     /// ```
  96     pub MISSING_SAFETY_DOC,
  97     style,
  98     "`pub unsafe fn` without `# Safety` docs"
  99 }
 100
 101 declare_clippy_lint! {
 102     /// **What it does:** Checks the doc comments of publicly visible functions that
 103     /// return a `Result` type and warns if there is no `# Errors` section.
 104     ///
 105     /// **Why is this bad?** Documenting the type of errors that can be returned from a
 106     /// function can help callers write code to handle the errors appropriately.
 107     ///
 108     /// **Known problems:** None.
 109     ///
 110     /// **Examples:**
 111     ///
 112     /// Since the following function returns a `Result` it has an `# Errors` section in
 113     /// its doc comment:
 114     ///
 115     /// ```rust
 116     ///# use std::io;
 117     /// /// # Errors
 118     /// ///
 119     /// /// Will return `Err` if `filename` does not exist or the user does not have
 120     /// /// permission to read it.
 121     /// pub fn read(filename: String) -> io::Result<String> {
 122     ///     unimplemented!();
 123     /// }
 124     /// ```
 125     pub MISSING_ERRORS_DOC,
 126     pedantic,
 127     "`pub fn` returns `Result` without `# Errors` in doc comment"
 128 }
 129
 130 declare_clippy_lint! {
 131     /// **What it does:** Checks the doc comments of publicly visible functions that
 132     /// may panic and warns if there is no `# Panics` section.
 133     ///
 134     /// **Why is this bad?** Documenting the scenarios in which panicking occurs
 135     /// can help callers who do not want to panic to avoid those situations.
 136     ///
 137     /// **Known problems:** None.
 138     ///
 139     /// **Examples:**
 140     ///
 141     /// Since the following function may panic it has a `# Panics` section in
 142     /// its doc comment:
 143     ///
 144     /// ```rust
 145     /// /// # Panics
 146     /// ///
 147     /// /// Will panic if y is 0
 148     /// pub fn divide_by(x: i32, y: i32) -> i32 {
 149     ///     if y == 0 {
 150     ///         panic!("Cannot divide by 0")
 151     ///     } else {
 152     ///         x / y
 153     ///     }
 154     /// }
 155     /// ```
 156     pub MISSING_PANICS_DOC,
 157     pedantic,
 158     "`pub fn` may panic without `# Panics` in doc comment"
 159 }
 160
 161 declare_clippy_lint! {
 162     /// **What it does:** Checks for `fn main() { .. }` in doctests
 163     ///
 164     /// **Why is this bad?** The test can be shorter (and likely more readable)
 165     /// if the `fn main()` is left implicit.
 166     ///
 167     /// **Known problems:** None.
 168     ///
 169     /// **Examples:**
 170     /// ``````rust
 171     /// /// An example of a doctest with a `main()` function
 172     /// ///
 173     /// /// # Examples
 174     /// ///
 175     /// /// ```
 176     /// /// fn main() {
 177     /// ///     // this needs not be in an `fn`
 178     /// /// }
 179     /// /// ```
 180     /// fn needless_main() {
 181     ///     unimplemented!();
 182     /// }
 183     /// ``````
 184     pub NEEDLESS_DOCTEST_MAIN,
 185     style,
 186     "presence of `fn main() {` in code examples"
 187 }
 188
 189 #[allow(clippy::module_name_repetitions)]
 190 #[derive(Clone)]
 191 pub struct DocMarkdown {
 192     valid_idents: FxHashSet<String>,
 193     in_trait_impl: bool,
 194 }
 195
 196 impl DocMarkdown {
 197     pub fn new(valid_idents: FxHashSet<String>) -> Self {
 198         Self {
 199             valid_idents,
 200             in_trait_impl: false,
 201         }
 202     }
 203 }
 204
 205 impl_lint_pass!(DocMarkdown =>
 206     [DOC_MARKDOWN, MISSING_SAFETY_DOC, MISSING_ERRORS_DOC, MISSING_PANICS_DOC, NEEDLESS_DOCTEST_MAIN]
 207 );
 208
 209 impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
 210     fn check_crate(&mut self, cx: &LateContext<'tcx>, _: &'tcx hir::Crate<'_>) {
 211         let attrs = cx.tcx.hir().attrs(hir::CRATE_HIR_ID);
 212         check_attrs(cx, &self.valid_idents, attrs);
 213     }
 214
 215     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
 216         let attrs = cx.tcx.hir().attrs(item.hir_id());
 217         let headers = check_attrs(cx, &self.valid_idents, attrs);
 218         match item.kind {
 219             hir::ItemKind::Fn(ref sig, _, body_id) => {
 220                 if !(is_entrypoint_fn(cx, item.def_id.to_def_id()) || in_external_macro(cx.tcx.sess, item.span)) {
 221                     let body = cx.tcx.hir().body(body_id);
 222                     let mut fpu = FindPanicUnwrap {
 223                         cx,
 224                         typeck_results: cx.tcx.typeck(item.def_id),
 225                         panic_span: None,
 226                     };
 227                     fpu.visit_expr(&body.value);
 228                     lint_for_missing_headers(
 229                         cx,
 230                         item.hir_id(),
 231                         item.span,
 232                         sig,
 233                         headers,
 234                         Some(body_id),
 235                         fpu.panic_span,
 236                     );
 237                 }
 238             },
 239             hir::ItemKind::Impl(ref impl_) => {
 240                 self.in_trait_impl = impl_.of_trait.is_some();
 241             },
 242             _ => {},
 243         }
 244     }
 245
 246     fn check_item_post(&mut self, _cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
 247         if let hir::ItemKind::Impl { .. } = item.kind {
 248             self.in_trait_impl = false;
 249         }
 250     }
 251
 252     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
 253         let attrs = cx.tcx.hir().attrs(item.hir_id());
 254         let headers = check_attrs(cx, &self.valid_idents, attrs);
 255         if let hir::TraitItemKind::Fn(ref sig, ..) = item.kind {
 256             if !in_external_macro(cx.tcx.sess, item.span) {
 257                 lint_for_missing_headers(cx, item.hir_id(), item.span, sig, headers, None, None);
 258             }
 259         }
 260     }
 261
 262     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
 263         let attrs = cx.tcx.hir().attrs(item.hir_id());
 264         let headers = check_attrs(cx, &self.valid_idents, attrs);
 265         if self.in_trait_impl || in_external_macro(cx.tcx.sess, item.span) {
 266             return;
 267         }
 268         if let hir::ImplItemKind::Fn(ref sig, body_id) = item.kind {
 269             let body = cx.tcx.hir().body(body_id);
 270             let mut fpu = FindPanicUnwrap {
 271                 cx,
 272                 typeck_results: cx.tcx.typeck(item.def_id),
 273                 panic_span: None,
 274             };
 275             fpu.visit_expr(&body.value);
 276             lint_for_missing_headers(
 277                 cx,
 278                 item.hir_id(),
 279                 item.span,
 280                 sig,
 281                 headers,
 282                 Some(body_id),
 283                 fpu.panic_span,
 284             );
 285         }
 286     }
 287 }
 288
 289 fn lint_for_missing_headers<'tcx>(
 290     cx: &LateContext<'tcx>,
 291     hir_id: hir::HirId,
 292     span: impl Into<MultiSpan> + Copy,
 293     sig: &hir::FnSig<'_>,
 294     headers: DocHeaders,
 295     body_id: Option<hir::BodyId>,
 296     panic_span: Option<Span>,
 297 ) {
 298     if !cx.access_levels.is_exported(hir_id) {
 299         return; // Private functions do not require doc comments
 300     }
 301     if !headers.safety && sig.header.unsafety == hir::Unsafety::Unsafe {
 302         span_lint(
 303             cx,
 304             MISSING_SAFETY_DOC,
 305             span,
 306             "unsafe function's docs miss `# Safety` section",
 307         );
 308     }
 309     if !headers.panics && panic_span.is_some() {
 310         span_lint_and_note(
 311             cx,
 312             MISSING_PANICS_DOC,
 313             span,
 314             "docs for function which may panic missing `# Panics` section",
 315             panic_span,
 316             "first possible panic found here",
 317         );
 318     }
 319     if !headers.errors {
 320         if is_type_diagnostic_item(cx, return_ty(cx, hir_id), sym::result_type) {
 321             span_lint(
 322                 cx,
 323                 MISSING_ERRORS_DOC,
 324                 span,
 325                 "docs for function returning `Result` missing `# Errors` section",
 326             );
 327         } else {
 328             if_chain! {
 329                 if let Some(body_id) = body_id;
 330                 if let Some(future) = cx.tcx.lang_items().future_trait();
 331                 let typeck = cx.tcx.typeck_body(body_id);
 332                 let body = cx.tcx.hir().body(body_id);
 333                 let ret_ty = typeck.expr_ty(&body.value);
 334                 if implements_trait(cx, ret_ty, future, &[]);
 335                 if let ty::Opaque(_, subs) = ret_ty.kind();
 336                 if let Some(gen) = subs.types().next();
 337                 if let ty::Generator(_, subs, _) = gen.kind();
 338                 if is_type_diagnostic_item(cx, subs.as_generator().return_ty(), sym::result_type);
 339                 then {
 340                     span_lint(
 341                         cx,
 342                         MISSING_ERRORS_DOC,
 343                         span,
 344                         "docs for function returning `Result` missing `# Errors` section",
 345                     );
 346                 }
 347             }
 348         }
 349     }
 350 }
 351
 352 /// Cleanup documentation decoration.
 353 ///
 354 /// We can't use `rustc_ast::attr::AttributeMethods::with_desugared_doc` or
 355 /// `rustc_ast::parse::lexer::comments::strip_doc_comment_decoration` because we
 356 /// need to keep track of
 357 /// the spans but this function is inspired from the later.
 358 #[allow(clippy::cast_possible_truncation)]
 359 #[must_use]
 360 pub fn strip_doc_comment_decoration(doc: &str, comment_kind: CommentKind, span: Span) -> (String, Vec<(usize, Span)>) {
 361     // one-line comments lose their prefix
 362     if comment_kind == CommentKind::Line {
 363         let mut doc = doc.to_owned();
 364         doc.push('\n');
 365         let len = doc.len();
 366         // +3 skips the opening delimiter
 367         return (doc, vec![(len, span.with_lo(span.lo() + BytePos(3)))]);
 368     }
 369
 370     let mut sizes = vec![];
 371     let mut contains_initial_stars = false;
 372     for line in doc.lines() {
 373         let offset = line.as_ptr() as usize - doc.as_ptr() as usize;
 374         debug_assert_eq!(offset as u32 as usize, offset);
 375         contains_initial_stars |= line.trim_start().starts_with('*');
 376         // +1 adds the newline, +3 skips the opening delimiter
 377         sizes.push((line.len() + 1, span.with_lo(span.lo() + BytePos(3 + offset as u32))));
 378     }
 379     if !contains_initial_stars {
 380         return (doc.to_string(), sizes);
 381     }
 382     // remove the initial '*'s if any
 383     let mut no_stars = String::with_capacity(doc.len());
 384     for line in doc.lines() {
 385         let mut chars = line.chars();
 386         for c in &mut chars {
 387             if c.is_whitespace() {
 388                 no_stars.push(c);
 389             } else {
 390                 no_stars.push(if c == '*' { ' ' } else { c });
 391                 break;
 392             }
 393         }
 394         no_stars.push_str(chars.as_str());
 395         no_stars.push('\n');
 396     }
 397
 398     (no_stars, sizes)
 399 }
 400
 401 #[derive(Copy, Clone)]
 402 struct DocHeaders {
 403     safety: bool,
 404     errors: bool,
 405     panics: bool,
 406 }
 407
 408 fn check_attrs<'a>(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, attrs: &'a [Attribute]) -> DocHeaders {
 409     let mut doc = String::new();
 410     let mut spans = vec![];
 411
 412     for attr in attrs {
 413         if let AttrKind::DocComment(comment_kind, comment) = attr.kind {
 414             let (comment, current_spans) = strip_doc_comment_decoration(&comment.as_str(), comment_kind, attr.span);
 415             spans.extend_from_slice(&current_spans);
 416             doc.push_str(&comment);
 417         } else if attr.has_name(sym::doc) {
 418             // ignore mix of sugared and non-sugared doc
 419             // don't trigger the safety or errors check
 420             return DocHeaders {
 421                 safety: true,
 422                 errors: true,
 423                 panics: true,
 424             };
 425         }
 426     }
 427
 428     let mut current = 0;
 429     for &mut (ref mut offset, _) in &mut spans {
 430         let offset_copy = *offset;
 431         *offset = current;
 432         current += offset_copy;
 433     }
 434
 435     if doc.is_empty() {
 436         return DocHeaders {
 437             safety: false,
 438             errors: false,
 439             panics: false,
 440         };
 441     }
 442
 443     let parser = pulldown_cmark::Parser::new(&doc).into_offset_iter();
 444     // Iterate over all `Events` and combine consecutive events into one
 445     let events = parser.coalesce(|previous, current| {
 446         use pulldown_cmark::Event::Text;
 447
 448         let previous_range = previous.1;
 449         let current_range = current.1;
 450
 451         match (previous.0, current.0) {
 452             (Text(previous), Text(current)) => {
 453                 let mut previous = previous.to_string();
 454                 previous.push_str(&current);
 455                 Ok((Text(previous.into()), previous_range))
 456             },
 457             (previous, current) => Err(((previous, previous_range), (current, current_range))),
 458         }
 459     });
 460     check_doc(cx, valid_idents, events, &spans)
 461 }
 462
 463 const RUST_CODE: &[&str] = &["rust", "no_run", "should_panic", "compile_fail"];
 464
 465 fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize>)>>(
 466     cx: &LateContext<'_>,
 467     valid_idents: &FxHashSet<String>,
 468     events: Events,
 469     spans: &[(usize, Span)],
 470 ) -> DocHeaders {
 471     // true if a safety header was found
 472     use pulldown_cmark::CodeBlockKind;
 473     use pulldown_cmark::Event::{
 474         Code, End, FootnoteReference, HardBreak, Html, Rule, SoftBreak, Start, TaskListMarker, Text,
 475     };
 476     use pulldown_cmark::Tag::{CodeBlock, Heading, Link};
 477
 478     let mut headers = DocHeaders {
 479         safety: false,
 480         errors: false,
 481         panics: false,
 482     };
 483     let mut in_code = false;
 484     let mut in_link = None;
 485     let mut in_heading = false;
 486     let mut is_rust = false;
 487     let mut edition = None;
 488     for (event, range) in events {
 489         match event {
 490             Start(CodeBlock(ref kind)) => {
 491                 in_code = true;
 492                 if let CodeBlockKind::Fenced(lang) = kind {
 493                     for item in lang.split(',') {
 494                         if item == "ignore" {
 495                             is_rust = false;
 496                             break;
 497                         }
 498                         if let Some(stripped) = item.strip_prefix("edition") {
 499                             is_rust = true;
 500                             edition = stripped.parse::<Edition>().ok();
 501                         } else if item.is_empty() || RUST_CODE.contains(&item) {
 502                             is_rust = true;
 503                         }
 504                     }
 505                 }
 506             },
 507             End(CodeBlock(_)) => {
 508                 in_code = false;
 509                 is_rust = false;
 510             },
 511             Start(Link(_, url, _)) => in_link = Some(url),
 512             End(Link(..)) => in_link = None,
 513             Start(Heading(_)) => in_heading = true,
 514             End(Heading(_)) => in_heading = false,
 515             Start(_tag) | End(_tag) => (), // We don't care about other tags
 516             Html(_html) => (),             // HTML is weird, just ignore it
 517             SoftBreak | HardBreak | TaskListMarker(_) | Code(_) | Rule => (),
 518             FootnoteReference(text) | Text(text) => {
 519                 if Some(&text) == in_link.as_ref() {
 520                     // Probably a link of the form `<http://example.com>`
 521                     // Which are represented as a link to "http://example.com" with
 522                     // text "http://example.com" by pulldown-cmark
 523                     continue;
 524                 }
 525                 headers.safety |= in_heading && text.trim() == "Safety";
 526                 headers.errors |= in_heading && text.trim() == "Errors";
 527                 headers.panics |= in_heading && text.trim() == "Panics";
 528                 let index = match spans.binary_search_by(|c| c.0.cmp(&range.start)) {
 529                     Ok(o) => o,
 530                     Err(e) => e - 1,
 531                 };
 532                 let (begin, span) = spans[index];
 533                 if in_code {
 534                     if is_rust {
 535                         let edition = edition.unwrap_or_else(|| cx.tcx.sess.edition());
 536                         check_code(cx, &text, edition, span);
 537                     }
 538                 } else {
 539                     // Adjust for the beginning of the current `Event`
 540                     let span = span.with_lo(span.lo() + BytePos::from_usize(range.start - begin));
 541
 542                     check_text(cx, valid_idents, &text, span);
 543                 }
 544             },
 545         }
 546     }
 547     headers
 548 }
 549
 550 fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
 551     fn has_needless_main(code: &str, edition: Edition) -> bool {
 552         rustc_driver::catch_fatal_errors(|| {
 553             rustc_span::with_session_globals(edition, || {
 554                 let filename = FileName::anon_source_code(code);
 555
 556                 let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
 557                 let emitter = EmitterWriter::new(box io::sink(), None, false, false, false, None, false);
 558                 let handler = Handler::with_emitter(false, None, box emitter);
 559                 let sess = ParseSess::with_span_handler(handler, sm);
 560
 561                 let mut parser = match maybe_new_parser_from_source_str(&sess, filename, code.into()) {
 562                     Ok(p) => p,
 563                     Err(errs) => {
 564                         for mut err in errs {
 565                             err.cancel();
 566                         }
 567                         return false;
 568                     },
 569                 };
 570
 571                 let mut relevant_main_found = false;
 572                 loop {
 573                     match parser.parse_item(ForceCollect::No) {
 574                         Ok(Some(item)) => match &item.kind {
 575                             // Tests with one of these items are ignored
 576                             ItemKind::Static(..)
 577                             | ItemKind::Const(..)
 578                             | ItemKind::ExternCrate(..)
 579                             | ItemKind::ForeignMod(..) => return false,
 580                             // We found a main function ...
 581                             ItemKind::Fn(box FnKind(_, sig, _, Some(block))) if item.ident.name == sym::main => {
 582                                 let is_async = matches!(sig.header.asyncness, Async::Yes { .. });
 583                                 let returns_nothing = match &sig.decl.output {
 584                                     FnRetTy::Default(..) => true,
 585                                     FnRetTy::Ty(ty) if ty.kind.is_unit() => true,
 586                                     FnRetTy::Ty(_) => false,
 587                                 };
 588
 589                                 if returns_nothing && !is_async && !block.stmts.is_empty() {
 590                                     // This main function should be linted, but only if there are no other functions
 591                                     relevant_main_found = true;
 592                                 } else {
 593                                     // This main function should not be linted, we're done
 594                                     return false;
 595                                 }
 596                             },
 597                             // Another function was found; this case is ignored too
 598                             ItemKind::Fn(..) => return false,
 599                             _ => {},
 600                         },
 601                         Ok(None) => break,
 602                         Err(mut e) => {
 603                             e.cancel();
 604                             return false;
 605                         },
 606                     }
 607                 }
 608
 609                 relevant_main_found
 610             })
 611         })
 612         .ok()
 613         .unwrap_or_default()
 614     }
 615
 616     if has_needless_main(text, edition) {
 617         span_lint(cx, NEEDLESS_DOCTEST_MAIN, span, "needless `fn main` in doctest");
 618     }
 619 }
 620
 621 fn check_text(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, text: &str, span: Span) {
 622     for word in text.split(|c: char| c.is_whitespace() || c == '\'') {
 623         // Trim punctuation as in `some comment (see foo::bar).`
 624         //                                                   ^^
 625         // Or even as in `_foo bar_` which is emphasized.
 626         let word = word.trim_matches(|c: char| !c.is_alphanumeric());
 627
 628         if valid_idents.contains(word) {
 629             continue;
 630         }
 631
 632         // Adjust for the current word
 633         let offset = word.as_ptr() as usize - text.as_ptr() as usize;
 634         let span = Span::new(
 635             span.lo() + BytePos::from_usize(offset),
 636             span.lo() + BytePos::from_usize(offset + word.len()),
 637             span.ctxt(),
 638         );
 639
 640         check_word(cx, word, span);
 641     }
 642 }
 643
 644 fn check_word(cx: &LateContext<'_>, word: &str, span: Span) {
 645     /// Checks if a string is camel-case, i.e., contains at least two uppercase
 646     /// letters (`Clippy` is ok) and one lower-case letter (`NASA` is ok).
 647     /// Plurals are also excluded (`IDs` is ok).
 648     fn is_camel_case(s: &str) -> bool {
 649         if s.starts_with(|c: char| c.is_digit(10)) {
 650             return false;
 651         }
 652
 653         let s = s.strip_suffix('s').unwrap_or(s);
 654
 655         s.chars().all(char::is_alphanumeric)
 656             && s.chars().filter(|&c| c.is_uppercase()).take(2).count() > 1
 657             && s.chars().filter(|&c| c.is_lowercase()).take(1).count() > 0
 658     }
 659
 660     fn has_underscore(s: &str) -> bool {
 661         s != "_" && !s.contains("\\_") && s.contains('_')
 662     }
 663
 664     fn has_hyphen(s: &str) -> bool {
 665         s != "-" && s.contains('-')
 666     }
 667
 668     if let Ok(url) = Url::parse(word) {
 669         // try to get around the fact that `foo::bar` parses as a valid URL
 670         if !url.cannot_be_a_base() {
 671             span_lint(
 672                 cx,
 673                 DOC_MARKDOWN,
 674                 span,
 675                 "you should put bare URLs between `<`/`>` or make a proper Markdown link",
 676             );
 677
 678             return;
 679         }
 680     }
 681
 682     // We assume that mixed-case words are not meant to be put inside bacticks. (Issue #2343)
 683     if has_underscore(word) && has_hyphen(word) {
 684         return;
 685     }
 686
 687     if has_underscore(word) || word.contains("::") || is_camel_case(word) {
 688         span_lint(
 689             cx,
 690             DOC_MARKDOWN,
 691             span,
 692             &format!("you should put `{}` between ticks in the documentation", word),
 693         );
 694     }
 695 }
 696
 697 struct FindPanicUnwrap<'a, 'tcx> {
 698     cx: &'a LateContext<'tcx>,
 699     panic_span: Option<Span>,
 700     typeck_results: &'tcx ty::TypeckResults<'tcx>,
 701 }
 702
 703 impl<'a, 'tcx> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
 704     type Map = Map<'tcx>;
 705
 706     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
 707         if self.panic_span.is_some() {
 708             return;
 709         }
 710
 711         // check for `begin_panic`
 712         if_chain! {
 713             if let ExprKind::Call(func_expr, _) = expr.kind;
 714             if let ExprKind::Path(QPath::Resolved(_, path)) = func_expr.kind;
 715             if let Some(path_def_id) = path.res.opt_def_id();
 716             if match_panic_def_id(self.cx, path_def_id);
 717             if is_expn_of(expr.span, "unreachable").is_none();
 718             if !is_expn_of_debug_assertions(expr.span);
 719             then {
 720                 self.panic_span = Some(expr.span);
 721             }
 722         }
 723
 724         // check for `assert_eq` or `assert_ne`
 725         if is_expn_of(expr.span, "assert_eq").is_some() || is_expn_of(expr.span, "assert_ne").is_some() {
 726             self.panic_span = Some(expr.span);
 727         }
 728
 729         // check for `unwrap`
 730         if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
 731             let reciever_ty = self.typeck_results.expr_ty(&arglists[0][0]).peel_refs();
 732             if is_type_diagnostic_item(self.cx, reciever_ty, sym::option_type)
 733                 || is_type_diagnostic_item(self.cx, reciever_ty, sym::result_type)
 734             {
 735                 self.panic_span = Some(expr.span);
 736             }
 737         }
 738
 739         // and check sub-expressions
 740         intravisit::walk_expr(self, expr);
 741     }
 742
 743     // Panics in const blocks will cause compilation to fail.
 744     fn visit_anon_const(&mut self, _: &'tcx AnonConst) {}
 745
 746     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 747         NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
 748     }
 749 }
 750
 751 fn is_expn_of_debug_assertions(span: Span) -> bool {
 752     const MACRO_NAMES: &[&str] = &["debug_assert", "debug_assert_eq", "debug_assert_ne"];
 753     MACRO_NAMES.iter().any(|name| is_expn_of(span, name).is_some())
 754 }