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

   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, SuggestionStyle};
  15 use rustc_hir as hir;
  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;
  21 use rustc_middle::ty;
  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, MultiSpan, SourceMap, Span};
  29 use rustc_span::{sym, FileName, Pos};
  30 use std::io;
  31 use std::ops::Range;
  32 use std::thread;
  33 use url::Url;
  34
  35 declare_clippy_lint! {
  36     /// ### What it does
  37     /// Checks for the presence of `_`, `::` or camel-case words
  38     /// outside ticks in documentation.
  39     ///
  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
  44     /// consider that.
  45     ///
  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.
  50     ///
  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
  54     /// would fail.
  55     ///
  56     /// ### Examples
  57     /// ```rust
  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) {}
  62     /// ```
  63     ///
  64     /// ```rust
  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
  69     /// fn main() {}
  70     /// ```
  71     #[clippy::version = "pre 1.29.0"]
  72     pub DOC_MARKDOWN,
  73     pedantic,
  74     "presence of `_`, `::` or camel-case outside backticks in documentation"
  75 }
  76
  77 declare_clippy_lint! {
  78     /// ### What it does
  79     /// Checks for the doc comments of publicly visible
  80     /// unsafe functions and warns if there is no `# Safety` section.
  81     ///
  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.
  85     ///
  86     /// ### Examples
  87     /// ```rust
  88     ///# type Universe = ();
  89     /// /// This function should really be documented
  90     /// pub unsafe fn start_apocalypse(u: &mut Universe) {
  91     ///     unimplemented!();
  92     /// }
  93     /// ```
  94     ///
  95     /// At least write a line about safety:
  96     ///
  97     /// ```rust
  98     ///# type Universe = ();
  99     /// /// # Safety
 100     /// ///
 101     /// /// This function should not be called before the horsemen are ready.
 102     /// pub unsafe fn start_apocalypse(u: &mut Universe) {
 103     ///     unimplemented!();
 104     /// }
 105     /// ```
 106     #[clippy::version = "1.39.0"]
 107     pub MISSING_SAFETY_DOC,
 108     style,
 109     "`pub unsafe fn` without `# Safety` docs"
 110 }
 111
 112 declare_clippy_lint! {
 113     /// ### What it does
 114     /// Checks the doc comments of publicly visible functions that
 115     /// return a `Result` type and warns if there is no `# Errors` section.
 116     ///
 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.
 120     ///
 121     /// ### Examples
 122     /// Since the following function returns a `Result` it has an `# Errors` section in
 123     /// its doc comment:
 124     ///
 125     /// ```rust
 126     ///# use std::io;
 127     /// /// # Errors
 128     /// ///
 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!();
 133     /// }
 134     /// ```
 135     #[clippy::version = "1.41.0"]
 136     pub MISSING_ERRORS_DOC,
 137     pedantic,
 138     "`pub fn` returns `Result` without `# Errors` in doc comment"
 139 }
 140
 141 declare_clippy_lint! {
 142     /// ### What it does
 143     /// Checks the doc comments of publicly visible functions that
 144     /// may panic and warns if there is no `# Panics` section.
 145     ///
 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.
 149     ///
 150     /// ### Examples
 151     /// Since the following function may panic it has a `# Panics` section in
 152     /// its doc comment:
 153     ///
 154     /// ```rust
 155     /// /// # Panics
 156     /// ///
 157     /// /// Will panic if y is 0
 158     /// pub fn divide_by(x: i32, y: i32) -> i32 {
 159     ///     if y == 0 {
 160     ///         panic!("Cannot divide by 0")
 161     ///     } else {
 162     ///         x / y
 163     ///     }
 164     /// }
 165     /// ```
 166     #[clippy::version = "1.52.0"]
 167     pub MISSING_PANICS_DOC,
 168     pedantic,
 169     "`pub fn` may panic without `# Panics` in doc comment"
 170 }
 171
 172 declare_clippy_lint! {
 173     /// ### What it does
 174     /// Checks for `fn main() { .. }` in doctests
 175     ///
 176     /// ### Why is this bad?
 177     /// The test can be shorter (and likely more readable)
 178     /// if the `fn main()` is left implicit.
 179     ///
 180     /// ### Examples
 181     /// ``````rust
 182     /// /// An example of a doctest with a `main()` function
 183     /// ///
 184     /// /// # Examples
 185     /// ///
 186     /// /// ```
 187     /// /// fn main() {
 188     /// ///     // this needs not be in an `fn`
 189     /// /// }
 190     /// /// ```
 191     /// fn needless_main() {
 192     ///     unimplemented!();
 193     /// }
 194     /// ``````
 195     #[clippy::version = "1.40.0"]
 196     pub NEEDLESS_DOCTEST_MAIN,
 197     style,
 198     "presence of `fn main() {` in code examples"
 199 }
 200
 201 #[allow(clippy::module_name_repetitions)]
 202 #[derive(Clone)]
 203 pub struct DocMarkdown {
 204     valid_idents: FxHashSet<String>,
 205     in_trait_impl: bool,
 206 }
 207
 208 impl DocMarkdown {
 209     pub fn new(valid_idents: FxHashSet<String>) -> Self {
 210         Self {
 211             valid_idents,
 212             in_trait_impl: false,
 213         }
 214     }
 215 }
 216
 217 impl_lint_pass!(DocMarkdown =>
 218     [DOC_MARKDOWN, MISSING_SAFETY_DOC, MISSING_ERRORS_DOC, MISSING_PANICS_DOC, NEEDLESS_DOCTEST_MAIN]
 219 );
 220
 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);
 225     }
 226
 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);
 230         match item.kind {
 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 {
 235                         cx,
 236                         typeck_results: cx.tcx.typeck(item.def_id),
 237                         panic_span: None,
 238                     };
 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);
 241                 }
 242             },
 243             hir::ItemKind::Impl(ref impl_) => {
 244                 self.in_trait_impl = impl_.of_trait.is_some();
 245             },
 246             hir::ItemKind::Trait(_, unsafety, ..) => {
 247                 if !headers.safety && unsafety == hir::Unsafety::Unsafe {
 248                     span_lint(
 249                         cx,
 250                         MISSING_SAFETY_DOC,
 251                         item.span,
 252                         "docs for unsafe trait missing `# Safety` section",
 253                     );
 254                 }
 255             },
 256             _ => (),
 257         }
 258     }
 259
 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;
 263         }
 264     }
 265
 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);
 272             }
 273         }
 274     }
 275
 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) {
 280             return;
 281         }
 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 {
 285                 cx,
 286                 typeck_results: cx.tcx.typeck(item.def_id),
 287                 panic_span: None,
 288             };
 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);
 291         }
 292     }
 293 }
 294
 295 fn lint_for_missing_headers<'tcx>(
 296     cx: &LateContext<'tcx>,
 297     def_id: LocalDefId,
 298     span: impl Into<MultiSpan> + Copy,
 299     sig: &hir::FnSig<'_>,
 300     headers: DocHeaders,
 301     body_id: Option<hir::BodyId>,
 302     panic_span: Option<Span>,
 303 ) {
 304     if !cx.access_levels.is_exported(def_id) {
 305         return; // Private functions do not require doc comments
 306     }
 307
 308     // do not lint if any parent has `#[doc(hidden)]` attribute (#7347)
 309     if cx
 310         .tcx
 311         .hir()
 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)))
 314     {
 315         return;
 316     }
 317
 318     if !headers.safety && sig.header.unsafety == hir::Unsafety::Unsafe {
 319         span_lint(
 320             cx,
 321             MISSING_SAFETY_DOC,
 322             span,
 323             "unsafe function's docs miss `# Safety` section",
 324         );
 325     }
 326     if !headers.panics && panic_span.is_some() {
 327         span_lint_and_note(
 328             cx,
 329             MISSING_PANICS_DOC,
 330             span,
 331             "docs for function which may panic missing `# Panics` section",
 332             panic_span,
 333             "first possible panic found here",
 334         );
 335     }
 336     if !headers.errors {
 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) {
 339             span_lint(
 340                 cx,
 341                 MISSING_ERRORS_DOC,
 342                 span,
 343                 "docs for function returning `Result` missing `# Errors` section",
 344             );
 345         } else {
 346             if_chain! {
 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);
 357                 then {
 358                     span_lint(
 359                         cx,
 360                         MISSING_ERRORS_DOC,
 361                         span,
 362                         "docs for function returning `Result` missing `# Errors` section",
 363                     );
 364                 }
 365             }
 366         }
 367     }
 368 }
 369
 370 /// Cleanup documentation decoration.
 371 ///
 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 #[allow(clippy::cast_possible_truncation)]
 377 #[must_use]
 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();
 382         doc.push('\n');
 383         let len = doc.len();
 384         // +3 skips the opening delimiter
 385         return (doc, vec![(len, span.with_lo(span.lo() + BytePos(3)))]);
 386     }
 387
 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))));
 396     }
 397     if !contains_initial_stars {
 398         return (doc.to_string(), sizes);
 399     }
 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() {
 406                 no_stars.push(c);
 407             } else {
 408                 no_stars.push(if c == '*' { ' ' } else { c });
 409                 break;
 410             }
 411         }
 412         no_stars.push_str(chars.as_str());
 413         no_stars.push('\n');
 414     }
 415
 416     (no_stars, sizes)
 417 }
 418
 419 #[derive(Copy, Clone)]
 420 struct DocHeaders {
 421     safety: bool,
 422     errors: bool,
 423     panics: bool,
 424 }
 425
 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     #[allow(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()))
 434     }
 435
 436     let mut doc = String::new();
 437     let mut spans = vec![];
 438
 439     for attr in attrs {
 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(&current_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
 447             return DocHeaders {
 448                 safety: true,
 449                 errors: true,
 450                 panics: true,
 451             };
 452         }
 453     }
 454
 455     let mut current = 0;
 456     for &mut (ref mut offset, _) in &mut spans {
 457         let offset_copy = *offset;
 458         *offset = current;
 459         current += offset_copy;
 460     }
 461
 462     if doc.is_empty() {
 463         return DocHeaders {
 464             safety: false,
 465             errors: false,
 466             panics: false,
 467         };
 468     }
 469
 470     let mut cb = fake_broken_link_callback;
 471
 472     let parser =
 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;
 477
 478         let previous_range = previous.1;
 479         let current_range = current.1;
 480
 481         match (previous.0, current.0) {
 482             (Text(previous), Text(current)) => {
 483                 let mut previous = previous.to_string();
 484                 previous.push_str(&current);
 485                 Ok((Text(previous.into()), previous_range))
 486             },
 487             (previous, current) => Err(((previous, previous_range), (current, current_range))),
 488         }
 489     });
 490     check_doc(cx, valid_idents, events, &spans)
 491 }
 492
 493 const RUST_CODE: &[&str] = &["rust", "no_run", "should_panic", "compile_fail"];
 494
 495 fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize>)>>(
 496     cx: &LateContext<'_>,
 497     valid_idents: &FxHashSet<String>,
 498     events: Events,
 499     spans: &[(usize, Span)],
 500 ) -> DocHeaders {
 501     // true if a safety header was found
 502     use pulldown_cmark::Event::{
 503         Code, End, FootnoteReference, HardBreak, Html, Rule, SoftBreak, Start, TaskListMarker, Text,
 504     };
 505     use pulldown_cmark::Tag::{CodeBlock, Heading, Item, Link, Paragraph};
 506     use pulldown_cmark::{CodeBlockKind, CowStr};
 507
 508     let mut headers = DocHeaders {
 509         safety: false,
 510         errors: false,
 511         panics: false,
 512     };
 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 {
 522         match event {
 523             Start(CodeBlock(ref kind)) => {
 524                 in_code = true;
 525                 if let CodeBlockKind::Fenced(lang) = kind {
 526                     for item in lang.split(',') {
 527                         if item == "ignore" {
 528                             is_rust = false;
 529                             break;
 530                         }
 531                         if let Some(stripped) = item.strip_prefix("edition") {
 532                             is_rust = true;
 533                             edition = stripped.parse::<Edition>().ok();
 534                         } else if item.is_empty() || RUST_CODE.contains(&item) {
 535                             is_rust = true;
 536                         }
 537                     }
 538                 }
 539             },
 540             End(CodeBlock(_)) => {
 541                 in_code = false;
 542                 is_rust = false;
 543             },
 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 {
 548                     in_heading = true;
 549                 }
 550                 ticks_unbalanced = false;
 551                 let (_, span) = get_current_span(spans, range.start);
 552                 paragraph_span = first_line_of_span(cx, span);
 553             },
 554             End(Heading(_, _, _) | Paragraph | Item) => {
 555                 if let End(Heading(_, _, _)) = event {
 556                     in_heading = false;
 557                 }
 558                 if ticks_unbalanced {
 559                     span_lint_and_help(
 560                         cx,
 561                         DOC_MARKDOWN,
 562                         paragraph_span,
 563                         "backticks are unbalanced",
 564                         None,
 565                         "a backtick may be missing a pair",
 566                     );
 567                 } else {
 568                     for (text, span) in text_to_check {
 569                         check_text(cx, valid_idents, &text, span);
 570                     }
 571                 }
 572                 text_to_check = Vec::new();
 573             },
 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
 585                     continue;
 586                 }
 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";
 593                 if in_code {
 594                     if is_rust {
 595                         let edition = edition.unwrap_or_else(|| cx.tcx.sess.edition());
 596                         check_code(cx, &text, edition, span);
 597                     }
 598                 } else {
 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));
 602                 }
 603             },
 604         }
 605     }
 606     headers
 607 }
 608
 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)) {
 611         Ok(o) => o,
 612         Err(e) => e - 1,
 613     };
 614     spans[index]
 615 }
 616
 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);
 622
 623                 let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
 624                 let emitter = EmitterWriter::new(Box::new(io::sink()), None, false, false, false, None, false);
 625                 let handler = Handler::with_emitter(false, None, Box::new(emitter));
 626                 let sess = ParseSess::with_span_handler(handler, sm);
 627
 628                 let mut parser = match maybe_new_parser_from_source_str(&sess, filename, code) {
 629                     Ok(p) => p,
 630                     Err(errs) => {
 631                         for mut err in errs {
 632                             err.cancel();
 633                         }
 634                         return false;
 635                     },
 636                 };
 637
 638                 let mut relevant_main_found = false;
 639                 loop {
 640                     match parser.parse_item(ForceCollect::No) {
 641                         Ok(Some(item)) => match &item.kind {
 642                             // Tests with one of these items are ignored
 643                             ItemKind::Static(..)
 644                             | ItemKind::Const(..)
 645                             | ItemKind::ExternCrate(..)
 646                             | ItemKind::ForeignMod(..) => return false,
 647                             // We found a main function ...
 648                             ItemKind::Fn(box Fn {
 649                                 sig, body: Some(block), ..
 650                             }) if item.ident.name == sym::main => {
 651                                 let is_async = matches!(sig.header.asyncness, Async::Yes { .. });
 652                                 let returns_nothing = match &sig.decl.output {
 653                                     FnRetTy::Default(..) => true,
 654                                     FnRetTy::Ty(ty) if ty.kind.is_unit() => true,
 655                                     FnRetTy::Ty(_) => false,
 656                                 };
 657
 658                                 if returns_nothing && !is_async && !block.stmts.is_empty() {
 659                                     // This main function should be linted, but only if there are no other functions
 660                                     relevant_main_found = true;
 661                                 } else {
 662                                     // This main function should not be linted, we're done
 663                                     return false;
 664                                 }
 665                             },
 666                             // Another function was found; this case is ignored too
 667                             ItemKind::Fn(..) => return false,
 668                             _ => {},
 669                         },
 670                         Ok(None) => break,
 671                         Err(mut e) => {
 672                             e.cancel();
 673                             return false;
 674                         },
 675                     }
 676                 }
 677
 678                 relevant_main_found
 679             })
 680         })
 681         .ok()
 682         .unwrap_or_default()
 683     }
 684
 685     // Because of the global session, we need to create a new session in a different thread with
 686     // the edition we need.
 687     let text = text.to_owned();
 688     if thread::spawn(move || has_needless_main(text, edition))
 689         .join()
 690         .expect("thread::spawn failed")
 691     {
 692         span_lint(cx, NEEDLESS_DOCTEST_MAIN, span, "needless `fn main` in doctest");
 693     }
 694 }
 695
 696 fn check_text(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, text: &str, span: Span) {
 697     for word in text.split(|c: char| c.is_whitespace() || c == '\'') {
 698         // Trim punctuation as in `some comment (see foo::bar).`
 699         //                                                   ^^
 700         // Or even as in `_foo bar_` which is emphasized. Also preserve `::` as a prefix/suffix.
 701         let mut word = word.trim_matches(|c: char| !c.is_alphanumeric() && c != ':');
 702
 703         // Remove leading or trailing single `:` which may be part of a sentence.
 704         if word.starts_with(':') && !word.starts_with("::") {
 705             word = word.trim_start_matches(':');
 706         }
 707         if word.ends_with(':') && !word.ends_with("::") {
 708             word = word.trim_end_matches(':');
 709         }
 710
 711         if valid_idents.contains(word) || word.chars().all(|c| c == ':') {
 712             continue;
 713         }
 714
 715         // Adjust for the current word
 716         let offset = word.as_ptr() as usize - text.as_ptr() as usize;
 717         let span = Span::new(
 718             span.lo() + BytePos::from_usize(offset),
 719             span.lo() + BytePos::from_usize(offset + word.len()),
 720             span.ctxt(),
 721             span.parent(),
 722         );
 723
 724         check_word(cx, word, span);
 725     }
 726 }
 727
 728 fn check_word(cx: &LateContext<'_>, word: &str, span: Span) {
 729     /// Checks if a string is camel-case, i.e., contains at least two uppercase
 730     /// letters (`Clippy` is ok) and one lower-case letter (`NASA` is ok).
 731     /// Plurals are also excluded (`IDs` is ok).
 732     fn is_camel_case(s: &str) -> bool {
 733         if s.starts_with(|c: char| c.is_digit(10)) {
 734             return false;
 735         }
 736
 737         let s = s.strip_suffix('s').unwrap_or(s);
 738
 739         s.chars().all(char::is_alphanumeric)
 740             && s.chars().filter(|&c| c.is_uppercase()).take(2).count() > 1
 741             && s.chars().filter(|&c| c.is_lowercase()).take(1).count() > 0
 742     }
 743
 744     fn has_underscore(s: &str) -> bool {
 745         s != "_" && !s.contains("\\_") && s.contains('_')
 746     }
 747
 748     fn has_hyphen(s: &str) -> bool {
 749         s != "-" && s.contains('-')
 750     }
 751
 752     if let Ok(url) = Url::parse(word) {
 753         // try to get around the fact that `foo::bar` parses as a valid URL
 754         if !url.cannot_be_a_base() {
 755             span_lint(
 756                 cx,
 757                 DOC_MARKDOWN,
 758                 span,
 759                 "you should put bare URLs between `<`/`>` or make a proper Markdown link",
 760             );
 761
 762             return;
 763         }
 764     }
 765
 766     // We assume that mixed-case words are not meant to be put inside backticks. (Issue #2343)
 767     if has_underscore(word) && has_hyphen(word) {
 768         return;
 769     }
 770
 771     if has_underscore(word) || word.contains("::") || is_camel_case(word) {
 772         let mut applicability = Applicability::MachineApplicable;
 773
 774         span_lint_and_then(
 775             cx,
 776             DOC_MARKDOWN,
 777             span,
 778             "item in documentation is missing backticks",
 779             |diag| {
 780                 let snippet = snippet_with_applicability(cx, span, "..", &mut applicability);
 781                 diag.span_suggestion_with_style(
 782                     span,
 783                     "try",
 784                     format!("`{}`", snippet),
 785                     applicability,
 786                     // always show the suggestion in a separate line, since the
 787                     // inline presentation adds another pair of backticks
 788                     SuggestionStyle::ShowAlways,
 789                 );
 790             },
 791         );
 792     }
 793 }
 794
 795 struct FindPanicUnwrap<'a, 'tcx> {
 796     cx: &'a LateContext<'tcx>,
 797     panic_span: Option<Span>,
 798     typeck_results: &'tcx ty::TypeckResults<'tcx>,
 799 }
 800
 801 impl<'a, 'tcx> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
 802     type NestedFilter = nested_filter::OnlyBodies;
 803
 804     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
 805         if self.panic_span.is_some() {
 806             return;
 807         }
 808
 809         if let Some(macro_call) = root_macro_call_first_node(self.cx, expr) {
 810             if is_panic(self.cx, macro_call.def_id)
 811                 || matches!(
 812                     self.cx.tcx.item_name(macro_call.def_id).as_str(),
 813                     "assert" | "assert_eq" | "assert_ne" | "todo"
 814                 )
 815             {
 816                 self.panic_span = Some(macro_call.span);
 817             }
 818         }
 819
 820         // check for `unwrap`
 821         if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
 822             let receiver_ty = self.typeck_results.expr_ty(&arglists[0][0]).peel_refs();
 823             if is_type_diagnostic_item(self.cx, receiver_ty, sym::Option)
 824                 || is_type_diagnostic_item(self.cx, receiver_ty, sym::Result)
 825             {
 826                 self.panic_span = Some(expr.span);
 827             }
 828         }
 829
 830         // and check sub-expressions
 831         intravisit::walk_expr(self, expr);
 832     }
 833
 834     // Panics in const blocks will cause compilation to fail.
 835     fn visit_anon_const(&mut self, _: &'tcx AnonConst) {}
 836
 837     fn nested_visit_map(&mut self) -> Self::Map {
 838         self.cx.tcx.hir()
 839     }
 840 }