src/librustdoc/passes/collect_intra_doc_links.rs

   1 //! This module implements [RFC 1946]: Intra-rustdoc-links
   2 //!
   3 //! [RFC 1946]: https://github.com/rust-lang/rfcs/blob/master/text/1946-intra-rustdoc-links.md
   4
   5 use rustc_ast as ast;
   6 use rustc_data_structures::{fx::FxHashMap, stable_set::FxHashSet};
   7 use rustc_errors::{Applicability, DiagnosticBuilder};
   8 use rustc_expand::base::SyntaxExtensionKind;
   9 use rustc_hir as hir;
  10 use rustc_hir::def::{
  11     DefKind,
  12     Namespace::{self, *},
  13     PerNS,
  14 };
  15 use rustc_hir::def_id::{CrateNum, DefId};
  16 use rustc_middle::ty::TyCtxt;
  17 use rustc_middle::{bug, ty};
  18 use rustc_resolve::ParentScope;
  19 use rustc_session::lint::Lint;
  20 use rustc_span::hygiene::{MacroKind, SyntaxContext};
  21 use rustc_span::symbol::{sym, Ident, Symbol};
  22 use rustc_span::DUMMY_SP;
  23 use smallvec::{smallvec, SmallVec};
  24
  25 use pulldown_cmark::LinkType;
  26
  27 use std::borrow::Cow;
  28 use std::cell::Cell;
  29 use std::convert::{TryFrom, TryInto};
  30 use std::mem;
  31 use std::ops::Range;
  32
  33 use crate::clean::{self, utils::find_nearest_parent_module, Crate, Item, ItemLink, PrimitiveType};
  34 use crate::core::DocContext;
  35 use crate::fold::DocFolder;
  36 use crate::html::markdown::{markdown_links, MarkdownLink};
  37 use crate::lint::{BROKEN_INTRA_DOC_LINKS, PRIVATE_INTRA_DOC_LINKS};
  38 use crate::passes::Pass;
  39
  40 use super::span_of_attrs;
  41
  42 crate const COLLECT_INTRA_DOC_LINKS: Pass = Pass {
  43     name: "collect-intra-doc-links",
  44     run: collect_intra_doc_links,
  45     description: "resolves intra-doc links",
  46 };
  47
  48 crate fn collect_intra_doc_links(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
  49     LinkCollector {
  50         cx,
  51         mod_ids: Vec::new(),
  52         kind_side_channel: Cell::new(None),
  53         visited_links: FxHashMap::default(),
  54     }
  55     .fold_crate(krate)
  56 }
  57
  58 /// Top-level errors emitted by this pass.
  59 enum ErrorKind<'a> {
  60     Resolve(Box<ResolutionFailure<'a>>),
  61     AnchorFailure(AnchorFailure),
  62 }
  63
  64 impl<'a> From<ResolutionFailure<'a>> for ErrorKind<'a> {
  65     fn from(err: ResolutionFailure<'a>) -> Self {
  66         ErrorKind::Resolve(box err)
  67     }
  68 }
  69
  70 #[derive(Copy, Clone, Debug, Hash)]
  71 enum Res {
  72     Def(DefKind, DefId),
  73     Primitive(PrimitiveType),
  74 }
  75
  76 type ResolveRes = rustc_hir::def::Res<rustc_ast::NodeId>;
  77
  78 impl Res {
  79     fn descr(self) -> &'static str {
  80         match self {
  81             Res::Def(kind, id) => ResolveRes::Def(kind, id).descr(),
  82             Res::Primitive(_) => "builtin type",
  83         }
  84     }
  85
  86     fn article(self) -> &'static str {
  87         match self {
  88             Res::Def(kind, id) => ResolveRes::Def(kind, id).article(),
  89             Res::Primitive(_) => "a",
  90         }
  91     }
  92
  93     fn name(self, tcx: TyCtxt<'_>) -> String {
  94         match self {
  95             Res::Def(_, id) => tcx.item_name(id).to_string(),
  96             Res::Primitive(prim) => prim.as_str().to_string(),
  97         }
  98     }
  99
 100     fn def_id(self) -> DefId {
 101         self.opt_def_id().expect("called def_id() on a primitive")
 102     }
 103
 104     fn opt_def_id(self) -> Option<DefId> {
 105         match self {
 106             Res::Def(_, id) => Some(id),
 107             Res::Primitive(_) => None,
 108         }
 109     }
 110
 111     fn as_hir_res(self) -> Option<rustc_hir::def::Res> {
 112         match self {
 113             Res::Def(kind, id) => Some(rustc_hir::def::Res::Def(kind, id)),
 114             // FIXME: maybe this should handle the subset of PrimitiveType that fits into hir::PrimTy?
 115             Res::Primitive(_) => None,
 116         }
 117     }
 118 }
 119
 120 impl TryFrom<ResolveRes> for Res {
 121     type Error = ();
 122
 123     fn try_from(res: ResolveRes) -> Result<Self, ()> {
 124         use rustc_hir::def::Res::*;
 125         match res {
 126             Def(kind, id) => Ok(Res::Def(kind, id)),
 127             PrimTy(prim) => Ok(Res::Primitive(PrimitiveType::from_hir(prim))),
 128             // e.g. `#[derive]`
 129             NonMacroAttr(..) | Err => Result::Err(()),
 130             other => bug!("unrecognized res {:?}", other),
 131         }
 132     }
 133 }
 134
 135 /// A link failed to resolve.
 136 #[derive(Debug)]
 137 enum ResolutionFailure<'a> {
 138     /// This resolved, but with the wrong namespace.
 139     WrongNamespace {
 140         /// What the link resolved to.
 141         res: Res,
 142         /// The expected namespace for the resolution, determined from the link's disambiguator.
 143         ///
 144         /// E.g., for `[fn@Result]` this is [`Namespace::ValueNS`],
 145         /// even though `Result`'s actual namespace is [`Namespace::TypeNS`].
 146         expected_ns: Namespace,
 147     },
 148     /// The link failed to resolve. [`resolution_failure`] should look to see if there's
 149     /// a more helpful error that can be given.
 150     NotResolved {
 151         /// The scope the link was resolved in.
 152         module_id: DefId,
 153         /// If part of the link resolved, this has the `Res`.
 154         ///
 155         /// In `[std::io::Error::x]`, `std::io::Error` would be a partial resolution.
 156         partial_res: Option<Res>,
 157         /// The remaining unresolved path segments.
 158         ///
 159         /// In `[std::io::Error::x]`, `x` would be unresolved.
 160         unresolved: Cow<'a, str>,
 161     },
 162     /// This happens when rustdoc can't determine the parent scope for an item.
 163     /// It is always a bug in rustdoc.
 164     NoParentItem,
 165     /// This link has malformed generic parameters; e.g., the angle brackets are unbalanced.
 166     MalformedGenerics(MalformedGenerics),
 167     /// Used to communicate that this should be ignored, but shouldn't be reported to the user.
 168     ///
 169     /// This happens when there is no disambiguator and one of the namespaces
 170     /// failed to resolve.
 171     Dummy,
 172 }
 173
 174 #[derive(Debug)]
 175 enum MalformedGenerics {
 176     /// This link has unbalanced angle brackets.
 177     ///
 178     /// For example, `Vec<T` should trigger this, as should `Vec<T>>`.
 179     UnbalancedAngleBrackets,
 180     /// The generics are not attached to a type.
 181     ///
 182     /// For example, `<T>` should trigger this.
 183     ///
 184     /// This is detected by checking if the path is empty after the generics are stripped.
 185     MissingType,
 186     /// The link uses fully-qualified syntax, which is currently unsupported.
 187     ///
 188     /// For example, `<Vec as IntoIterator>::into_iter` should trigger this.
 189     ///
 190     /// This is detected by checking if ` as ` (the keyword `as` with spaces around it) is inside
 191     /// angle brackets.
 192     HasFullyQualifiedSyntax,
 193     /// The link has an invalid path separator.
 194     ///
 195     /// For example, `Vec:<T>:new()` should trigger this. Note that `Vec:new()` will **not**
 196     /// trigger this because it has no generics and thus [`strip_generics_from_path`] will not be
 197     /// called.
 198     ///
 199     /// Note that this will also **not** be triggered if the invalid path separator is inside angle
 200     /// brackets because rustdoc mostly ignores what's inside angle brackets (except for
 201     /// [`HasFullyQualifiedSyntax`](MalformedGenerics::HasFullyQualifiedSyntax)).
 202     ///
 203     /// This is detected by checking if there is a colon followed by a non-colon in the link.
 204     InvalidPathSeparator,
 205     /// The link has too many angle brackets.
 206     ///
 207     /// For example, `Vec<<T>>` should trigger this.
 208     TooManyAngleBrackets,
 209     /// The link has empty angle brackets.
 210     ///
 211     /// For example, `Vec<>` should trigger this.
 212     EmptyAngleBrackets,
 213 }
 214
 215 impl ResolutionFailure<'a> {
 216     /// This resolved fully (not just partially) but is erroneous for some other reason
 217     ///
 218     /// Returns the full resolution of the link, if present.
 219     fn full_res(&self) -> Option<Res> {
 220         match self {
 221             Self::WrongNamespace { res, expected_ns: _ } => Some(*res),
 222             _ => None,
 223         }
 224     }
 225 }
 226
 227 enum AnchorFailure {
 228     /// User error: `[std#x#y]` is not valid
 229     MultipleAnchors,
 230     /// The anchor provided by the user conflicts with Rustdoc's generated anchor.
 231     ///
 232     /// This is an unfortunate state of affairs. Not every item that can be
 233     /// linked to has its own page; sometimes it is a subheading within a page,
 234     /// like for associated items. In those cases, rustdoc uses an anchor to
 235     /// link to the subheading. Since you can't have two anchors for the same
 236     /// link, Rustdoc disallows having a user-specified anchor.
 237     ///
 238     /// Most of the time this is fine, because you can just link to the page of
 239     /// the item if you want to provide your own anchor. For primitives, though,
 240     /// rustdoc uses the anchor as a side channel to know which page to link to;
 241     /// it doesn't show up in the generated link. Ideally, rustdoc would remove
 242     /// this limitation, allowing you to link to subheaders on primitives.
 243     RustdocAnchorConflict(Res),
 244 }
 245
 246 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
 247 struct ResolutionInfo {
 248     module_id: DefId,
 249     dis: Option<Disambiguator>,
 250     path_str: String,
 251     extra_fragment: Option<String>,
 252 }
 253
 254 struct DiagnosticInfo<'a> {
 255     item: &'a Item,
 256     dox: &'a str,
 257     ori_link: &'a str,
 258     link_range: Range<usize>,
 259 }
 260
 261 #[derive(Clone, Debug, Hash)]
 262 struct CachedLink {
 263     pub res: (Res, Option<String>),
 264     pub side_channel: Option<(DefKind, DefId)>,
 265 }
 266
 267 struct LinkCollector<'a, 'tcx> {
 268     cx: &'a mut DocContext<'tcx>,
 269     /// A stack of modules used to decide what scope to resolve in.
 270     ///
 271     /// The last module will be used if the parent scope of the current item is
 272     /// unknown.
 273     mod_ids: Vec<DefId>,
 274     /// This is used to store the kind of associated items,
 275     /// because `clean` and the disambiguator code expect them to be different.
 276     /// See the code for associated items on inherent impls for details.
 277     kind_side_channel: Cell<Option<(DefKind, DefId)>>,
 278     /// Cache the resolved links so we can avoid resolving (and emitting errors for) the same link.
 279     /// The link will be `None` if it could not be resolved (i.e. the error was cached).
 280     visited_links: FxHashMap<ResolutionInfo, Option<CachedLink>>,
 281 }
 282
 283 impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
 284     /// Given a full link, parse it as an [enum struct variant].
 285     ///
 286     /// In particular, this will return an error whenever there aren't three
 287     /// full path segments left in the link.
 288     ///
 289     /// [enum struct variant]: hir::VariantData::Struct
 290     fn variant_field(
 291         &self,
 292         path_str: &'path str,
 293         module_id: DefId,
 294     ) -> Result<(Res, Option<String>), ErrorKind<'path>> {
 295         let tcx = self.cx.tcx;
 296         let no_res = || ResolutionFailure::NotResolved {
 297             module_id,
 298             partial_res: None,
 299             unresolved: path_str.into(),
 300         };
 301
 302         debug!("looking for enum variant {}", path_str);
 303         let mut split = path_str.rsplitn(3, "::");
 304         let (variant_field_str, variant_field_name) = split
 305             .next()
 306             .map(|f| (f, Symbol::intern(f)))
 307             .expect("fold_item should ensure link is non-empty");
 308         let (variant_str, variant_name) =
 309             // we're not sure this is a variant at all, so use the full string
 310             // If there's no second component, the link looks like `[path]`.
 311             // So there's no partial res and we should say the whole link failed to resolve.
 312             split.next().map(|f| (f, Symbol::intern(f))).ok_or_else(no_res)?;
 313         let path = split
 314             .next()
 315             .map(|f| f.to_owned())
 316             // If there's no third component, we saw `[a::b]` before and it failed to resolve.
 317             // So there's no partial res.
 318             .ok_or_else(no_res)?;
 319         let ty_res = self
 320             .cx
 321             .enter_resolver(|resolver| {
 322                 resolver.resolve_str_path_error(DUMMY_SP, &path, TypeNS, module_id)
 323             })
 324             .and_then(|(_, res)| res.try_into())
 325             .map_err(|()| no_res())?;
 326
 327         match ty_res {
 328             Res::Def(DefKind::Enum, did) => {
 329                 if tcx
 330                     .inherent_impls(did)
 331                     .iter()
 332                     .flat_map(|imp| tcx.associated_items(*imp).in_definition_order())
 333                     .any(|item| item.ident.name == variant_name)
 334                 {
 335                     // This is just to let `fold_item` know that this shouldn't be considered;
 336                     // it's a bug for the error to make it to the user
 337                     return Err(ResolutionFailure::Dummy.into());
 338                 }
 339                 match tcx.type_of(did).kind() {
 340                     ty::Adt(def, _) if def.is_enum() => {
 341                         if def.all_fields().any(|item| item.ident.name == variant_field_name) {
 342                             Ok((
 343                                 ty_res,
 344                                 Some(format!(
 345                                     "variant.{}.field.{}",
 346                                     variant_str, variant_field_name
 347                                 )),
 348                             ))
 349                         } else {
 350                             Err(ResolutionFailure::NotResolved {
 351                                 module_id,
 352                                 partial_res: Some(Res::Def(DefKind::Enum, def.did)),
 353                                 unresolved: variant_field_str.into(),
 354                             }
 355                             .into())
 356                         }
 357                     }
 358                     _ => unreachable!(),
 359                 }
 360             }
 361             _ => Err(ResolutionFailure::NotResolved {
 362                 module_id,
 363                 partial_res: Some(ty_res),
 364                 unresolved: variant_str.into(),
 365             }
 366             .into()),
 367         }
 368     }
 369
 370     /// Given a primitive type, try to resolve an associated item.
 371     ///
 372     /// HACK(jynelson): `item_str` is passed in instead of derived from `item_name` so the
 373     /// lifetimes on `&'path` will work.
 374     fn resolve_primitive_associated_item(
 375         &self,
 376         prim_ty: PrimitiveType,
 377         ns: Namespace,
 378         module_id: DefId,
 379         item_name: Symbol,
 380         item_str: &'path str,
 381     ) -> Result<(Res, Option<String>), ErrorKind<'path>> {
 382         let tcx = self.cx.tcx;
 383
 384         prim_ty
 385             .impls(tcx)
 386             .into_iter()
 387             .find_map(|&impl_| {
 388                 tcx.associated_items(impl_)
 389                     .find_by_name_and_namespace(tcx, Ident::with_dummy_span(item_name), ns, impl_)
 390                     .map(|item| {
 391                         let kind = item.kind;
 392                         self.kind_side_channel.set(Some((kind.as_def_kind(), item.def_id)));
 393                         match kind {
 394                             ty::AssocKind::Fn => "method",
 395                             ty::AssocKind::Const => "associatedconstant",
 396                             ty::AssocKind::Type => "associatedtype",
 397                         }
 398                     })
 399                     .map(|out| {
 400                         (
 401                             Res::Primitive(prim_ty),
 402                             Some(format!("{}#{}.{}", prim_ty.as_str(), out, item_str)),
 403                         )
 404                     })
 405             })
 406             .ok_or_else(|| {
 407                 debug!(
 408                     "returning primitive error for {}::{} in {} namespace",
 409                     prim_ty.as_str(),
 410                     item_name,
 411                     ns.descr()
 412                 );
 413                 ResolutionFailure::NotResolved {
 414                     module_id,
 415                     partial_res: Some(Res::Primitive(prim_ty)),
 416                     unresolved: item_str.into(),
 417                 }
 418                 .into()
 419             })
 420     }
 421
 422     /// Resolves a string as a macro.
 423     ///
 424     /// FIXME(jynelson): Can this be unified with `resolve()`?
 425     fn resolve_macro(
 426         &self,
 427         path_str: &'a str,
 428         module_id: DefId,
 429     ) -> Result<Res, ResolutionFailure<'a>> {
 430         let path = ast::Path::from_ident(Ident::from_str(path_str));
 431         self.cx.enter_resolver(|resolver| {
 432             // FIXME(jynelson): does this really need 3 separate lookups?
 433             if let Ok((Some(ext), res)) = resolver.resolve_macro_path(
 434                 &path,
 435                 None,
 436                 &ParentScope::module(resolver.graph_root(), resolver),
 437                 false,
 438                 false,
 439             ) {
 440                 if let SyntaxExtensionKind::LegacyBang { .. } = ext.kind {
 441                     return Ok(res.try_into().unwrap());
 442                 }
 443             }
 444             if let Some(&res) = resolver.all_macros().get(&Symbol::intern(path_str)) {
 445                 return Ok(res.try_into().unwrap());
 446             }
 447             debug!("resolving {} as a macro in the module {:?}", path_str, module_id);
 448             if let Ok((_, res)) =
 449                 resolver.resolve_str_path_error(DUMMY_SP, path_str, MacroNS, module_id)
 450             {
 451                 // don't resolve builtins like `#[derive]`
 452                 if let Ok(res) = res.try_into() {
 453                     return Ok(res);
 454                 }
 455             }
 456             Err(ResolutionFailure::NotResolved {
 457                 module_id,
 458                 partial_res: None,
 459                 unresolved: path_str.into(),
 460             })
 461         })
 462     }
 463
 464     /// Convenience wrapper around `resolve_str_path_error`.
 465     ///
 466     /// This also handles resolving `true` and `false` as booleans.
 467     /// NOTE: `resolve_str_path_error` knows only about paths, not about types.
 468     /// Associated items will never be resolved by this function.
 469     fn resolve_path(&self, path_str: &str, ns: Namespace, module_id: DefId) -> Option<Res> {
 470         let result = self.cx.enter_resolver(|resolver| {
 471             resolver
 472                 .resolve_str_path_error(DUMMY_SP, &path_str, ns, module_id)
 473                 .and_then(|(_, res)| res.try_into())
 474         });
 475         debug!("{} resolved to {:?} in namespace {:?}", path_str, result, ns);
 476         match result {
 477             // resolver doesn't know about true, false, and types that aren't paths (e.g. `()`)
 478             // manually as bool
 479             Err(()) => resolve_primitive(path_str, ns),
 480             Ok(res) => Some(res),
 481         }
 482     }
 483
 484     /// Resolves a string as a path within a particular namespace. Returns an
 485     /// optional URL fragment in the case of variants and methods.
 486     fn resolve<'path>(
 487         &mut self,
 488         path_str: &'path str,
 489         ns: Namespace,
 490         module_id: DefId,
 491         extra_fragment: &Option<String>,
 492     ) -> Result<(Res, Option<String>), ErrorKind<'path>> {
 493         let tcx = self.cx.tcx;
 494
 495         if let Some(res) = self.resolve_path(path_str, ns, module_id) {
 496             match res {
 497                 // FIXME(#76467): make this fallthrough to lookup the associated
 498                 // item a separate function.
 499                 Res::Def(DefKind::AssocFn | DefKind::AssocConst, _) => assert_eq!(ns, ValueNS),
 500                 Res::Def(DefKind::AssocTy, _) => assert_eq!(ns, TypeNS),
 501                 Res::Def(DefKind::Variant, _) => {
 502                     return handle_variant(self.cx, res, extra_fragment);
 503                 }
 504                 // Not a trait item; just return what we found.
 505                 Res::Primitive(ty) => {
 506                     if extra_fragment.is_some() {
 507                         return Err(ErrorKind::AnchorFailure(
 508                             AnchorFailure::RustdocAnchorConflict(res),
 509                         ));
 510                     }
 511                     return Ok((res, Some(ty.as_str().to_owned())));
 512                 }
 513                 _ => return Ok((res, extra_fragment.clone())),
 514             }
 515         }
 516
 517         // Try looking for methods and associated items.
 518         let mut split = path_str.rsplitn(2, "::");
 519         // NB: `split`'s first element is always defined, even if the delimiter was not present.
 520         // NB: `item_str` could be empty when resolving in the root namespace (e.g. `::std`).
 521         let item_str = split.next().unwrap();
 522         let item_name = Symbol::intern(item_str);
 523         let path_root = split
 524             .next()
 525             .map(|f| f.to_owned())
 526             // If there's no `::`, it's not an associated item.
 527             // So we can be sure that `rustc_resolve` was accurate when it said it wasn't resolved.
 528             .ok_or_else(|| {
 529                 debug!("found no `::`, assumming {} was correctly not in scope", item_name);
 530                 ResolutionFailure::NotResolved {
 531                     module_id,
 532                     partial_res: None,
 533                     unresolved: item_str.into(),
 534                 }
 535             })?;
 536
 537         // FIXME: are these both necessary?
 538         let ty_res = if let Some(ty_res) = resolve_primitive(&path_root, TypeNS)
 539             .or_else(|| self.resolve_path(&path_root, TypeNS, module_id))
 540         {
 541             ty_res
 542         } else {
 543             // FIXME: this is duplicated on the end of this function.
 544             return if ns == Namespace::ValueNS {
 545                 self.variant_field(path_str, module_id)
 546             } else {
 547                 Err(ResolutionFailure::NotResolved {
 548                     module_id,
 549                     partial_res: None,
 550                     unresolved: path_root.into(),
 551                 }
 552                 .into())
 553             };
 554         };
 555
 556         let res = match ty_res {
 557             Res::Primitive(prim) => Some(
 558                 self.resolve_primitive_associated_item(prim, ns, module_id, item_name, item_str),
 559             ),
 560             Res::Def(
 561                 DefKind::Struct
 562                 | DefKind::Union
 563                 | DefKind::Enum
 564                 | DefKind::TyAlias
 565                 | DefKind::ForeignTy,
 566                 did,
 567             ) => {
 568                 debug!("looking for associated item named {} for item {:?}", item_name, did);
 569                 // Checks if item_name belongs to `impl SomeItem`
 570                 let assoc_item = tcx
 571                     .inherent_impls(did)
 572                     .iter()
 573                     .flat_map(|&imp| {
 574                         tcx.associated_items(imp).find_by_name_and_namespace(
 575                             tcx,
 576                             Ident::with_dummy_span(item_name),
 577                             ns,
 578                             imp,
 579                         )
 580                     })
 581                     .map(|item| (item.kind, item.def_id))
 582                     // There should only ever be one associated item that matches from any inherent impl
 583                     .next()
 584                     // Check if item_name belongs to `impl SomeTrait for SomeItem`
 585                     // FIXME(#74563): This gives precedence to `impl SomeItem`:
 586                     // Although having both would be ambiguous, use impl version for compatibility's sake.
 587                     // To handle that properly resolve() would have to support
 588                     // something like [`ambi_fn`](<SomeStruct as SomeTrait>::ambi_fn)
 589                     .or_else(|| {
 590                         let kind =
 591                             resolve_associated_trait_item(did, module_id, item_name, ns, self.cx);
 592                         debug!("got associated item kind {:?}", kind);
 593                         kind
 594                     });
 595
 596                 if let Some((kind, id)) = assoc_item {
 597                     let out = match kind {
 598                         ty::AssocKind::Fn => "method",
 599                         ty::AssocKind::Const => "associatedconstant",
 600                         ty::AssocKind::Type => "associatedtype",
 601                     };
 602                     Some(if extra_fragment.is_some() {
 603                         Err(ErrorKind::AnchorFailure(AnchorFailure::RustdocAnchorConflict(ty_res)))
 604                     } else {
 605                         // HACK(jynelson): `clean` expects the type, not the associated item
 606                         // but the disambiguator logic expects the associated item.
 607                         // Store the kind in a side channel so that only the disambiguator logic looks at it.
 608                         self.kind_side_channel.set(Some((kind.as_def_kind(), id)));
 609                         Ok((ty_res, Some(format!("{}.{}", out, item_str))))
 610                     })
 611                 } else if ns == Namespace::ValueNS {
 612                     debug!("looking for variants or fields named {} for {:?}", item_name, did);
 613                     // FIXME(jynelson): why is this different from
 614                     // `variant_field`?
 615                     match tcx.type_of(did).kind() {
 616                         ty::Adt(def, _) => {
 617                             let field = if def.is_enum() {
 618                                 def.all_fields().find(|item| item.ident.name == item_name)
 619                             } else {
 620                                 def.non_enum_variant()
 621                                     .fields
 622                                     .iter()
 623                                     .find(|item| item.ident.name == item_name)
 624                             };
 625                             field.map(|item| {
 626                                 if extra_fragment.is_some() {
 627                                     let res = Res::Def(
 628                                         if def.is_enum() {
 629                                             DefKind::Variant
 630                                         } else {
 631                                             DefKind::Field
 632                                         },
 633                                         item.did,
 634                                     );
 635                                     Err(ErrorKind::AnchorFailure(
 636                                         AnchorFailure::RustdocAnchorConflict(res),
 637                                     ))
 638                                 } else {
 639                                     Ok((
 640                                         ty_res,
 641                                         Some(format!(
 642                                             "{}.{}",
 643                                             if def.is_enum() { "variant" } else { "structfield" },
 644                                             item.ident
 645                                         )),
 646                                     ))
 647                                 }
 648                             })
 649                         }
 650                         _ => None,
 651                     }
 652                 } else {
 653                     None
 654                 }
 655             }
 656             Res::Def(DefKind::Trait, did) => tcx
 657                 .associated_items(did)
 658                 .find_by_name_and_namespace(tcx, Ident::with_dummy_span(item_name), ns, did)
 659                 .map(|item| {
 660                     let kind = match item.kind {
 661                         ty::AssocKind::Const => "associatedconstant",
 662                         ty::AssocKind::Type => "associatedtype",
 663                         ty::AssocKind::Fn => {
 664                             if item.defaultness.has_value() {
 665                                 "method"
 666                             } else {
 667                                 "tymethod"
 668                             }
 669                         }
 670                     };
 671
 672                     if extra_fragment.is_some() {
 673                         Err(ErrorKind::AnchorFailure(AnchorFailure::RustdocAnchorConflict(ty_res)))
 674                     } else {
 675                         let res = Res::Def(item.kind.as_def_kind(), item.def_id);
 676                         Ok((res, Some(format!("{}.{}", kind, item_str))))
 677                     }
 678                 }),
 679             _ => None,
 680         };
 681         res.unwrap_or_else(|| {
 682             if ns == Namespace::ValueNS {
 683                 self.variant_field(path_str, module_id)
 684             } else {
 685                 Err(ResolutionFailure::NotResolved {
 686                     module_id,
 687                     partial_res: Some(ty_res),
 688                     unresolved: item_str.into(),
 689                 }
 690                 .into())
 691             }
 692         })
 693     }
 694
 695     /// Used for reporting better errors.
 696     ///
 697     /// Returns whether the link resolved 'fully' in another namespace.
 698     /// 'fully' here means that all parts of the link resolved, not just some path segments.
 699     /// This returns the `Res` even if it was erroneous for some reason
 700     /// (such as having invalid URL fragments or being in the wrong namespace).
 701     fn check_full_res(
 702         &mut self,
 703         ns: Namespace,
 704         path_str: &str,
 705         module_id: DefId,
 706         extra_fragment: &Option<String>,
 707     ) -> Option<Res> {
 708         // resolve() can't be used for macro namespace
 709         let result = match ns {
 710             Namespace::MacroNS => self.resolve_macro(path_str, module_id).map_err(ErrorKind::from),
 711             Namespace::TypeNS | Namespace::ValueNS => {
 712                 self.resolve(path_str, ns, module_id, extra_fragment).map(|(res, _)| res)
 713             }
 714         };
 715
 716         let res = match result {
 717             Ok(res) => Some(res),
 718             Err(ErrorKind::Resolve(box kind)) => kind.full_res(),
 719             Err(ErrorKind::AnchorFailure(AnchorFailure::RustdocAnchorConflict(res))) => Some(res),
 720             Err(ErrorKind::AnchorFailure(AnchorFailure::MultipleAnchors)) => None,
 721         };
 722         self.kind_side_channel.take().map(|(kind, id)| Res::Def(kind, id)).or(res)
 723     }
 724 }
 725
 726 /// Look to see if a resolved item has an associated item named `item_name`.
 727 ///
 728 /// Given `[std::io::Error::source]`, where `source` is unresolved, this would
 729 /// find `std::error::Error::source` and return
 730 /// `<io::Error as error::Error>::source`.
 731 fn resolve_associated_trait_item(
 732     did: DefId,
 733     module: DefId,
 734     item_name: Symbol,
 735     ns: Namespace,
 736     cx: &mut DocContext<'_>,
 737 ) -> Option<(ty::AssocKind, DefId)> {
 738     // FIXME: this should also consider blanket impls (`impl<T> X for T`). Unfortunately
 739     // `get_auto_trait_and_blanket_impls` is broken because the caching behavior is wrong. In the
 740     // meantime, just don't look for these blanket impls.
 741
 742     // Next consider explicit impls: `impl MyTrait for MyType`
 743     // Give precedence to inherent impls.
 744     let traits = traits_implemented_by(cx, did, module);
 745     debug!("considering traits {:?}", traits);
 746     let mut candidates = traits.iter().filter_map(|&trait_| {
 747         cx.tcx
 748             .associated_items(trait_)
 749             .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, trait_)
 750             .map(|assoc| (assoc.kind, assoc.def_id))
 751     });
 752     // FIXME(#74563): warn about ambiguity
 753     debug!("the candidates were {:?}", candidates.clone().collect::<Vec<_>>());
 754     candidates.next()
 755 }
 756
 757 /// Given a type, return all traits in scope in `module` implemented by that type.
 758 ///
 759 /// NOTE: this cannot be a query because more traits could be available when more crates are compiled!
 760 /// So it is not stable to serialize cross-crate.
 761 fn traits_implemented_by(cx: &mut DocContext<'_>, type_: DefId, module: DefId) -> FxHashSet<DefId> {
 762     let mut resolver = cx.resolver.borrow_mut();
 763     let in_scope_traits = cx.module_trait_cache.entry(module).or_insert_with(|| {
 764         resolver.access(|resolver| {
 765             let parent_scope = &ParentScope::module(resolver.get_module(module), resolver);
 766             resolver
 767                 .traits_in_scope(None, parent_scope, SyntaxContext::root(), None)
 768                 .into_iter()
 769                 .map(|candidate| candidate.def_id)
 770                 .collect()
 771         })
 772     });
 773
 774     let tcx = cx.tcx;
 775     let ty = tcx.type_of(type_);
 776     let iter = in_scope_traits.iter().flat_map(|&trait_| {
 777         trace!("considering explicit impl for trait {:?}", trait_);
 778
 779         // Look at each trait implementation to see if it's an impl for `did`
 780         tcx.find_map_relevant_impl(trait_, ty, |impl_| {
 781             let trait_ref = tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
 782             // Check if these are the same type.
 783             let impl_type = trait_ref.self_ty();
 784             trace!(
 785                 "comparing type {} with kind {:?} against type {:?}",
 786                 impl_type,
 787                 impl_type.kind(),
 788                 type_
 789             );
 790             // Fast path: if this is a primitive simple `==` will work
 791             let saw_impl = impl_type == ty
 792                 || match impl_type.kind() {
 793                     // Check if these are the same def_id
 794                     ty::Adt(def, _) => {
 795                         debug!("adt def_id: {:?}", def.did);
 796                         def.did == type_
 797                     }
 798                     ty::Foreign(def_id) => *def_id == type_,
 799                     _ => false,
 800                 };
 801
 802             if saw_impl { Some(trait_) } else { None }
 803         })
 804     });
 805     iter.collect()
 806 }
 807
 808 /// Check for resolve collisions between a trait and its derive.
 809 ///
 810 /// These are common and we should just resolve to the trait in that case.
 811 fn is_derive_trait_collision<T>(ns: &PerNS<Result<(Res, T), ResolutionFailure<'_>>>) -> bool {
 812     matches!(
 813         *ns,
 814         PerNS {
 815             type_ns: Ok((Res::Def(DefKind::Trait, _), _)),
 816             macro_ns: Ok((Res::Def(DefKind::Macro(MacroKind::Derive), _), _)),
 817             ..
 818         }
 819     )
 820 }
 821
 822 impl<'a, 'tcx> DocFolder for LinkCollector<'a, 'tcx> {
 823     fn fold_item(&mut self, mut item: Item) -> Option<Item> {
 824         use rustc_middle::ty::DefIdTree;
 825
 826         let parent_node = if item.is_fake() {
 827             None
 828         } else {
 829             find_nearest_parent_module(self.cx.tcx, item.def_id)
 830         };
 831
 832         if parent_node.is_some() {
 833             trace!("got parent node for {:?} {:?}, id {:?}", item.type_(), item.name, item.def_id);
 834         }
 835
 836         // find item's parent to resolve `Self` in item's docs below
 837         debug!("looking for the `Self` type");
 838         let self_id = if item.is_fake() {
 839             None
 840         // Checking if the item is a field in an enum variant
 841         } else if (matches!(self.cx.tcx.def_kind(item.def_id), DefKind::Field)
 842             && matches!(
 843                 self.cx.tcx.def_kind(self.cx.tcx.parent(item.def_id).unwrap()),
 844                 DefKind::Variant
 845             ))
 846         {
 847             self.cx.tcx.parent(item.def_id).and_then(|item_id| self.cx.tcx.parent(item_id))
 848         } else if matches!(
 849             self.cx.tcx.def_kind(item.def_id),
 850             DefKind::AssocConst
 851                 | DefKind::AssocFn
 852                 | DefKind::AssocTy
 853                 | DefKind::Variant
 854                 | DefKind::Field
 855         ) {
 856             self.cx.tcx.parent(item.def_id)
 857         // HACK(jynelson): `clean` marks associated types as `TypedefItem`, not as `AssocTypeItem`.
 858         // Fixing this breaks `fn render_deref_methods`.
 859         // As a workaround, see if the parent of the item is an `impl`; if so this must be an associated item,
 860         // regardless of what rustdoc wants to call it.
 861         } else if let Some(parent) = self.cx.tcx.parent(item.def_id) {
 862             let parent_kind = self.cx.tcx.def_kind(parent);
 863             Some(if parent_kind == DefKind::Impl { parent } else { item.def_id })
 864         } else {
 865             Some(item.def_id)
 866         };
 867
 868         // FIXME(jynelson): this shouldn't go through stringification, rustdoc should just use the DefId directly
 869         let self_name = self_id.and_then(|self_id| {
 870             if matches!(self.cx.tcx.def_kind(self_id), DefKind::Impl) {
 871                 // using `ty.to_string()` (or any variant) has issues with raw idents
 872                 let ty = self.cx.tcx.type_of(self_id);
 873                 let name = match ty.kind() {
 874                     ty::Adt(def, _) => Some(self.cx.tcx.item_name(def.did).to_string()),
 875                     other if other.is_primitive() => Some(ty.to_string()),
 876                     _ => None,
 877                 };
 878                 debug!("using type_of(): {:?}", name);
 879                 name
 880             } else {
 881                 let name = self.cx.tcx.opt_item_name(self_id).map(|sym| sym.to_string());
 882                 debug!("using item_name(): {:?}", name);
 883                 name
 884             }
 885         });
 886
 887         if item.is_mod() && item.attrs.inner_docs {
 888             self.mod_ids.push(item.def_id);
 889         }
 890
 891         // We want to resolve in the lexical scope of the documentation.
 892         // In the presence of re-exports, this is not the same as the module of the item.
 893         // Rather than merging all documentation into one, resolve it one attribute at a time
 894         // so we know which module it came from.
 895         for (parent_module, doc) in item.attrs.collapsed_doc_value_by_module_level() {
 896             debug!("combined_docs={}", doc);
 897
 898             let (krate, parent_node) = if let Some(id) = parent_module {
 899                 (id.krate, Some(id))
 900             } else {
 901                 (item.def_id.krate, parent_node)
 902             };
 903             // NOTE: if there are links that start in one crate and end in another, this will not resolve them.
 904             // This is a degenerate case and it's not supported by rustdoc.
 905             for md_link in markdown_links(&doc) {
 906                 let link = self.resolve_link(&item, &doc, &self_name, parent_node, krate, md_link);
 907                 if let Some(link) = link {
 908                     item.attrs.links.push(link);
 909                 }
 910             }
 911         }
 912
 913         Some(if item.is_mod() {
 914             if !item.attrs.inner_docs {
 915                 self.mod_ids.push(item.def_id);
 916             }
 917
 918             let ret = self.fold_item_recur(item);
 919             self.mod_ids.pop();
 920             ret
 921         } else {
 922             self.fold_item_recur(item)
 923         })
 924     }
 925 }
 926
 927 impl LinkCollector<'_, '_> {
 928     /// This is the entry point for resolving an intra-doc link.
 929     ///
 930     /// FIXME(jynelson): this is way too many arguments
 931     fn resolve_link(
 932         &mut self,
 933         item: &Item,
 934         dox: &str,
 935         self_name: &Option<String>,
 936         parent_node: Option<DefId>,
 937         krate: CrateNum,
 938         ori_link: MarkdownLink,
 939     ) -> Option<ItemLink> {
 940         trace!("considering link '{}'", ori_link.link);
 941
 942         // Bail early for real links.
 943         if ori_link.link.contains('/') {
 944             return None;
 945         }
 946
 947         // [] is mostly likely not supposed to be a link
 948         if ori_link.link.is_empty() {
 949             return None;
 950         }
 951
 952         let link = ori_link.link.replace("`", "");
 953         let no_backticks_range = range_between_backticks(&ori_link);
 954         let parts = link.split('#').collect::<Vec<_>>();
 955         let (link, extra_fragment) = if parts.len() > 2 {
 956             // A valid link can't have multiple #'s
 957             anchor_failure(
 958                 self.cx,
 959                 &item,
 960                 &link,
 961                 dox,
 962                 ori_link.range,
 963                 AnchorFailure::MultipleAnchors,
 964             );
 965             return None;
 966         } else if parts.len() == 2 {
 967             if parts[0].trim().is_empty() {
 968                 // This is an anchor to an element of the current page, nothing to do in here!
 969                 return None;
 970             }
 971             (parts[0], Some(parts[1].to_owned()))
 972         } else {
 973             (parts[0], None)
 974         };
 975
 976         // Parse and strip the disambiguator from the link, if present.
 977         let (mut path_str, disambiguator) = match Disambiguator::from_str(&link) {
 978             Ok(Some((d, path))) => (path.trim(), Some(d)),
 979             Ok(None) => (link.trim(), None),
 980             Err((err_msg, relative_range)) => {
 981                 if !should_ignore_link_with_disambiguators(link) {
 982                     // Only report error if we would not have ignored this link.
 983                     // See issue #83859.
 984                     let disambiguator_range = (no_backticks_range.start + relative_range.start)
 985                         ..(no_backticks_range.start + relative_range.end);
 986                     disambiguator_error(self.cx, &item, dox, disambiguator_range, &err_msg);
 987                 }
 988                 return None;
 989             }
 990         };
 991
 992         if should_ignore_link(path_str) {
 993             return None;
 994         }
 995
 996         // We stripped `()` and `!` when parsing the disambiguator.
 997         // Add them back to be displayed, but not prefix disambiguators.
 998         let link_text =
 999             disambiguator.map(|d| d.display_for(path_str)).unwrap_or_else(|| path_str.to_owned());
1000
1001         // In order to correctly resolve intra-doc links we need to
1002         // pick a base AST node to work from.  If the documentation for
1003         // this module came from an inner comment (//!) then we anchor
1004         // our name resolution *inside* the module.  If, on the other
1005         // hand it was an outer comment (///) then we anchor the name
1006         // resolution in the parent module on the basis that the names
1007         // used are more likely to be intended to be parent names.  For
1008         // this, we set base_node to None for inner comments since
1009         // we've already pushed this node onto the resolution stack but
1010         // for outer comments we explicitly try and resolve against the
1011         // parent_node first.
1012         let base_node = if item.is_mod() && item.attrs.inner_docs {
1013             self.mod_ids.last().copied()
1014         } else {
1015             parent_node
1016         };
1017
1018         let mut module_id = if let Some(id) = base_node {
1019             id
1020         } else {
1021             // This is a bug.
1022             debug!("attempting to resolve item without parent module: {}", path_str);
1023             resolution_failure(
1024                 self,
1025                 &item,
1026                 path_str,
1027                 disambiguator,
1028                 dox,
1029                 ori_link.range,
1030                 smallvec![ResolutionFailure::NoParentItem],
1031             );
1032             return None;
1033         };
1034
1035         let resolved_self;
1036         // replace `Self` with suitable item's parent name
1037         let is_lone_self = path_str == "Self";
1038         let is_lone_crate = path_str == "crate";
1039         if path_str.starts_with("Self::") || is_lone_self {
1040             if let Some(ref name) = self_name {
1041                 if is_lone_self {
1042                     path_str = name;
1043                 } else {
1044                     resolved_self = format!("{}::{}", name, &path_str[6..]);
1045                     path_str = &resolved_self;
1046                 }
1047             }
1048         } else if path_str.starts_with("crate::") || is_lone_crate {
1049             use rustc_span::def_id::CRATE_DEF_INDEX;
1050
1051             // HACK(jynelson): rustc_resolve thinks that `crate` is the crate currently being documented.
1052             // But rustdoc wants it to mean the crate this item was originally present in.
1053             // To work around this, remove it and resolve relative to the crate root instead.
1054             // HACK(jynelson)(2): If we just strip `crate::` then suddenly primitives become ambiguous
1055             // (consider `crate::char`). Instead, change it to `self::`. This works because 'self' is now the crate root.
1056             // FIXME(#78696): This doesn't always work.
1057             if is_lone_crate {
1058                 path_str = "self";
1059             } else {
1060                 resolved_self = format!("self::{}", &path_str["crate::".len()..]);
1061                 path_str = &resolved_self;
1062             }
1063             module_id = DefId { krate, index: CRATE_DEF_INDEX };
1064         }
1065
1066         // Strip generics from the path.
1067         let stripped_path_string;
1068         if path_str.contains(['<', '>'].as_slice()) {
1069             stripped_path_string = match strip_generics_from_path(path_str) {
1070                 Ok(path) => path,
1071                 Err(err_kind) => {
1072                     debug!("link has malformed generics: {}", path_str);
1073                     resolution_failure(
1074                         self,
1075                         &item,
1076                         path_str,
1077                         disambiguator,
1078                         dox,
1079                         ori_link.range,
1080                         smallvec![err_kind],
1081                     );
1082                     return None;
1083                 }
1084             };
1085             path_str = &stripped_path_string;
1086         }
1087         // Sanity check to make sure we don't have any angle brackets after stripping generics.
1088         assert!(!path_str.contains(['<', '>'].as_slice()));
1089
1090         // The link is not an intra-doc link if it still contains spaces after stripping generics.
1091         if path_str.contains(' ') {
1092             return None;
1093         }
1094
1095         let diag_info = DiagnosticInfo {
1096             item,
1097             dox,
1098             ori_link: &ori_link.link,
1099             link_range: ori_link.range.clone(),
1100         };
1101         let (mut res, mut fragment) = self.resolve_with_disambiguator_cached(
1102             ResolutionInfo {
1103                 module_id,
1104                 dis: disambiguator,
1105                 path_str: path_str.to_owned(),
1106                 extra_fragment,
1107             },
1108             diag_info,
1109             matches!(ori_link.kind, LinkType::Reference | LinkType::Shortcut),
1110         )?;
1111
1112         // Check for a primitive which might conflict with a module
1113         // Report the ambiguity and require that the user specify which one they meant.
1114         // FIXME: could there ever be a primitive not in the type namespace?
1115         if matches!(
1116             disambiguator,
1117             None | Some(Disambiguator::Namespace(Namespace::TypeNS) | Disambiguator::Primitive)
1118         ) && !matches!(res, Res::Primitive(_))
1119         {
1120             if let Some(prim) = resolve_primitive(path_str, TypeNS) {
1121                 // `prim@char`
1122                 if matches!(disambiguator, Some(Disambiguator::Primitive)) {
1123                     if fragment.is_some() {
1124                         anchor_failure(
1125                             self.cx,
1126                             &item,
1127                             path_str,
1128                             dox,
1129                             ori_link.range,
1130                             AnchorFailure::RustdocAnchorConflict(prim),
1131                         );
1132                         return None;
1133                     }
1134                     res = prim;
1135                     fragment = Some(prim.name(self.cx.tcx));
1136                 } else {
1137                     // `[char]` when a `char` module is in scope
1138                     let candidates = vec![res, prim];
1139                     ambiguity_error(self.cx, &item, path_str, dox, ori_link.range, candidates);
1140                     return None;
1141                 }
1142             }
1143         }
1144
1145         let report_mismatch = |specified: Disambiguator, resolved: Disambiguator| {
1146             // The resolved item did not match the disambiguator; give a better error than 'not found'
1147             let msg = format!("incompatible link kind for `{}`", path_str);
1148             let callback = |diag: &mut DiagnosticBuilder<'_>, sp| {
1149                 let note = format!(
1150                     "this link resolved to {} {}, which is not {} {}",
1151                     resolved.article(),
1152                     resolved.descr(),
1153                     specified.article(),
1154                     specified.descr()
1155                 );
1156                 diag.note(&note);
1157                 suggest_disambiguator(resolved, diag, path_str, dox, sp, &ori_link.range);
1158             };
1159             report_diagnostic(
1160                 self.cx.tcx,
1161                 BROKEN_INTRA_DOC_LINKS,
1162                 &msg,
1163                 &item,
1164                 dox,
1165                 &ori_link.range,
1166                 callback,
1167             );
1168         };
1169
1170         let verify = |kind: DefKind, id: DefId| {
1171             let (kind, id) = self.kind_side_channel.take().unwrap_or((kind, id));
1172             debug!("intra-doc link to {} resolved to {:?} (id: {:?})", path_str, res, id);
1173
1174             // Disallow e.g. linking to enums with `struct@`
1175             debug!("saw kind {:?} with disambiguator {:?}", kind, disambiguator);
1176             match (kind, disambiguator) {
1177                 | (DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst, Some(Disambiguator::Kind(DefKind::Const)))
1178                 // NOTE: this allows 'method' to mean both normal functions and associated functions
1179                 // This can't cause ambiguity because both are in the same namespace.
1180                 | (DefKind::Fn | DefKind::AssocFn, Some(Disambiguator::Kind(DefKind::Fn)))
1181                 // These are namespaces; allow anything in the namespace to match
1182                 | (_, Some(Disambiguator::Namespace(_)))
1183                 // If no disambiguator given, allow anything
1184                 | (_, None)
1185                 // All of these are valid, so do nothing
1186                 => {}
1187                 (actual, Some(Disambiguator::Kind(expected))) if actual == expected => {}
1188                 (_, Some(specified @ Disambiguator::Kind(_) | specified @ Disambiguator::Primitive)) => {
1189                     report_mismatch(specified, Disambiguator::Kind(kind));
1190                     return None;
1191                 }
1192             }
1193
1194             // item can be non-local e.g. when using #[doc(primitive = "pointer")]
1195             if let Some((src_id, dst_id)) = id
1196                 .as_local()
1197                 .and_then(|dst_id| item.def_id.as_local().map(|src_id| (src_id, dst_id)))
1198             {
1199                 use rustc_hir::def_id::LOCAL_CRATE;
1200
1201                 let hir_src = self.cx.tcx.hir().local_def_id_to_hir_id(src_id);
1202                 let hir_dst = self.cx.tcx.hir().local_def_id_to_hir_id(dst_id);
1203
1204                 if self.cx.tcx.privacy_access_levels(LOCAL_CRATE).is_exported(hir_src)
1205                     && !self.cx.tcx.privacy_access_levels(LOCAL_CRATE).is_exported(hir_dst)
1206                 {
1207                     privacy_error(self.cx, &item, &path_str, dox, &ori_link);
1208                 }
1209             }
1210
1211             Some(())
1212         };
1213
1214         match res {
1215             Res::Primitive(prim) => {
1216                 if let Some((kind, id)) = self.kind_side_channel.take() {
1217                     // We're actually resolving an associated item of a primitive, so we need to
1218                     // verify the disambiguator (if any) matches the type of the associated item.
1219                     // This case should really follow the same flow as the `Res::Def` branch below,
1220                     // but attempting to add a call to `clean::register_res` causes an ICE. @jyn514
1221                     // thinks `register_res` is only needed for cross-crate re-exports, but Rust
1222                     // doesn't allow statements like `use str::trim;`, making this a (hopefully)
1223                     // valid omission. See https://github.com/rust-lang/rust/pull/80660#discussion_r551585677
1224                     // for discussion on the matter.
1225                     verify(kind, id)?;
1226
1227                     // FIXME: it would be nice to check that the feature gate was enabled in the original crate, not just ignore it altogether.
1228                     // However I'm not sure how to check that across crates.
1229                     if prim == PrimitiveType::RawPointer
1230                         && item.def_id.is_local()
1231                         && !self.cx.tcx.features().intra_doc_pointers
1232                     {
1233                         let span = super::source_span_for_markdown_range(
1234                             self.cx.tcx,
1235                             dox,
1236                             &ori_link.range,
1237                             &item.attrs,
1238                         )
1239                         .unwrap_or_else(|| span_of_attrs(&item.attrs).unwrap_or(item.span.inner()));
1240
1241                         rustc_session::parse::feature_err(
1242                             &self.cx.tcx.sess.parse_sess,
1243                             sym::intra_doc_pointers,
1244                             span,
1245                             "linking to associated items of raw pointers is experimental",
1246                         )
1247                         .note("rustdoc does not allow disambiguating between `*const` and `*mut`, and pointers are unstable until it does")
1248                         .emit();
1249                     }
1250                 } else {
1251                     match disambiguator {
1252                         Some(Disambiguator::Primitive | Disambiguator::Namespace(_)) | None => {}
1253                         Some(other) => {
1254                             report_mismatch(other, Disambiguator::Primitive);
1255                             return None;
1256                         }
1257                     }
1258                 }
1259
1260                 Some(ItemLink { link: ori_link.link, link_text, did: None, fragment })
1261             }
1262             Res::Def(kind, id) => {
1263                 verify(kind, id)?;
1264                 let id = clean::register_res(self.cx, rustc_hir::def::Res::Def(kind, id));
1265                 Some(ItemLink { link: ori_link.link, link_text, did: Some(id), fragment })
1266             }
1267         }
1268     }
1269
1270     fn resolve_with_disambiguator_cached(
1271         &mut self,
1272         key: ResolutionInfo,
1273         diag: DiagnosticInfo<'_>,
1274         cache_resolution_failure: bool,
1275     ) -> Option<(Res, Option<String>)> {
1276         // Try to look up both the result and the corresponding side channel value
1277         if let Some(ref cached) = self.visited_links.get(&key) {
1278             match cached {
1279                 Some(cached) => {
1280                     self.kind_side_channel.set(cached.side_channel.clone());
1281                     return Some(cached.res.clone());
1282                 }
1283                 None if cache_resolution_failure => return None,
1284                 None => {
1285                     // Although we hit the cache and found a resolution error, this link isn't
1286                     // supposed to cache those. Run link resolution again to emit the expected
1287                     // resolution error.
1288                 }
1289             }
1290         }
1291
1292         let res = self.resolve_with_disambiguator(&key, diag);
1293
1294         // Cache only if resolved successfully - don't silence duplicate errors
1295         if let Some(res) = res {
1296             // Store result for the actual namespace
1297             self.visited_links.insert(
1298                 key,
1299                 Some(CachedLink {
1300                     res: res.clone(),
1301                     side_channel: self.kind_side_channel.clone().into_inner(),
1302                 }),
1303             );
1304
1305             Some(res)
1306         } else {
1307             if cache_resolution_failure {
1308                 // For reference-style links we only want to report one resolution error
1309                 // so let's cache them as well.
1310                 self.visited_links.insert(key, None);
1311             }
1312
1313             None
1314         }
1315     }
1316
1317     /// After parsing the disambiguator, resolve the main part of the link.
1318     // FIXME(jynelson): wow this is just so much
1319     fn resolve_with_disambiguator(
1320         &mut self,
1321         key: &ResolutionInfo,
1322         diag: DiagnosticInfo<'_>,
1323     ) -> Option<(Res, Option<String>)> {
1324         let disambiguator = key.dis;
1325         let path_str = &key.path_str;
1326         let base_node = key.module_id;
1327         let extra_fragment = &key.extra_fragment;
1328
1329         match disambiguator.map(Disambiguator::ns) {
1330             Some(expected_ns @ (ValueNS | TypeNS)) => {
1331                 match self.resolve(path_str, expected_ns, base_node, extra_fragment) {
1332                     Ok(res) => Some(res),
1333                     Err(ErrorKind::Resolve(box mut kind)) => {
1334                         // We only looked in one namespace. Try to give a better error if possible.
1335                         if kind.full_res().is_none() {
1336                             let other_ns = if expected_ns == ValueNS { TypeNS } else { ValueNS };
1337                             // FIXME: really it should be `resolution_failure` that does this, not `resolve_with_disambiguator`
1338                             // See https://github.com/rust-lang/rust/pull/76955#discussion_r493953382 for a good approach
1339                             for &new_ns in &[other_ns, MacroNS] {
1340                                 if let Some(res) =
1341                                     self.check_full_res(new_ns, path_str, base_node, extra_fragment)
1342                                 {
1343                                     kind = ResolutionFailure::WrongNamespace { res, expected_ns };
1344                                     break;
1345                                 }
1346                             }
1347                         }
1348                         resolution_failure(
1349                             self,
1350                             diag.item,
1351                             path_str,
1352                             disambiguator,
1353                             diag.dox,
1354                             diag.link_range,
1355                             smallvec![kind],
1356                         );
1357                         // This could just be a normal link or a broken link
1358                         // we could potentially check if something is
1359                         // "intra-doc-link-like" and warn in that case.
1360                         None
1361                     }
1362                     Err(ErrorKind::AnchorFailure(msg)) => {
1363                         anchor_failure(
1364                             self.cx,
1365                             diag.item,
1366                             diag.ori_link,
1367                             diag.dox,
1368                             diag.link_range,
1369                             msg,
1370                         );
1371                         None
1372                     }
1373                 }
1374             }
1375             None => {
1376                 // Try everything!
1377                 let mut candidates = PerNS {
1378                     macro_ns: self
1379                         .resolve_macro(path_str, base_node)
1380                         .map(|res| (res, extra_fragment.clone())),
1381                     type_ns: match self.resolve(path_str, TypeNS, base_node, extra_fragment) {
1382                         Ok(res) => {
1383                             debug!("got res in TypeNS: {:?}", res);
1384                             Ok(res)
1385                         }
1386                         Err(ErrorKind::AnchorFailure(msg)) => {
1387                             anchor_failure(
1388                                 self.cx,
1389                                 diag.item,
1390                                 diag.ori_link,
1391                                 diag.dox,
1392                                 diag.link_range,
1393                                 msg,
1394                             );
1395                             return None;
1396                         }
1397                         Err(ErrorKind::Resolve(box kind)) => Err(kind),
1398                     },
1399                     value_ns: match self.resolve(path_str, ValueNS, base_node, extra_fragment) {
1400                         Ok(res) => Ok(res),
1401                         Err(ErrorKind::AnchorFailure(msg)) => {
1402                             anchor_failure(
1403                                 self.cx,
1404                                 diag.item,
1405                                 diag.ori_link,
1406                                 diag.dox,
1407                                 diag.link_range,
1408                                 msg,
1409                             );
1410                             return None;
1411                         }
1412                         Err(ErrorKind::Resolve(box kind)) => Err(kind),
1413                     }
1414                     .and_then(|(res, fragment)| {
1415                         // Constructors are picked up in the type namespace.
1416                         match res {
1417                             Res::Def(DefKind::Ctor(..), _) => {
1418                                 Err(ResolutionFailure::WrongNamespace { res, expected_ns: TypeNS })
1419                             }
1420                             _ => {
1421                                 match (fragment, extra_fragment.clone()) {
1422                                     (Some(fragment), Some(_)) => {
1423                                         // Shouldn't happen but who knows?
1424                                         Ok((res, Some(fragment)))
1425                                     }
1426                                     (fragment, None) | (None, fragment) => Ok((res, fragment)),
1427                                 }
1428                             }
1429                         }
1430                     }),
1431                 };
1432
1433                 let len = candidates.iter().filter(|res| res.is_ok()).count();
1434
1435                 if len == 0 {
1436                     resolution_failure(
1437                         self,
1438                         diag.item,
1439                         path_str,
1440                         disambiguator,
1441                         diag.dox,
1442                         diag.link_range,
1443                         candidates.into_iter().filter_map(|res| res.err()).collect(),
1444                     );
1445                     // this could just be a normal link
1446                     return None;
1447                 }
1448
1449                 if len == 1 {
1450                     Some(candidates.into_iter().filter_map(|res| res.ok()).next().unwrap())
1451                 } else if len == 2 && is_derive_trait_collision(&candidates) {
1452                     Some(candidates.type_ns.unwrap())
1453                 } else {
1454                     if is_derive_trait_collision(&candidates) {
1455                         candidates.macro_ns = Err(ResolutionFailure::Dummy);
1456                     }
1457                     // If we're reporting an ambiguity, don't mention the namespaces that failed
1458                     let candidates = candidates.map(|candidate| candidate.ok().map(|(res, _)| res));
1459                     ambiguity_error(
1460                         self.cx,
1461                         diag.item,
1462                         path_str,
1463                         diag.dox,
1464                         diag.link_range,
1465                         candidates.present_items().collect(),
1466                     );
1467                     None
1468                 }
1469             }
1470             Some(MacroNS) => {
1471                 match self.resolve_macro(path_str, base_node) {
1472                     Ok(res) => Some((res, extra_fragment.clone())),
1473                     Err(mut kind) => {
1474                         // `resolve_macro` only looks in the macro namespace. Try to give a better error if possible.
1475                         for &ns in &[TypeNS, ValueNS] {
1476                             if let Some(res) =
1477                                 self.check_full_res(ns, path_str, base_node, extra_fragment)
1478                             {
1479                                 kind =
1480                                     ResolutionFailure::WrongNamespace { res, expected_ns: MacroNS };
1481                                 break;
1482                             }
1483                         }
1484                         resolution_failure(
1485                             self,
1486                             diag.item,
1487                             path_str,
1488                             disambiguator,
1489                             diag.dox,
1490                             diag.link_range,
1491                             smallvec![kind],
1492                         );
1493                         None
1494                     }
1495                 }
1496             }
1497         }
1498     }
1499 }
1500
1501 /// Get the section of a link between the backticks,
1502 /// or the whole link if there aren't any backticks.
1503 ///
1504 /// For example:
1505 ///
1506 /// ```text
1507 /// [`Foo`]
1508 ///   ^^^
1509 /// ```
1510 fn range_between_backticks(ori_link: &MarkdownLink) -> Range<usize> {
1511     let after_first_backtick_group = ori_link.link.bytes().position(|b| b != b'`').unwrap_or(0);
1512     let before_second_backtick_group = ori_link
1513         .link
1514         .bytes()
1515         .skip(after_first_backtick_group)
1516         .position(|b| b == b'`')
1517         .unwrap_or(ori_link.link.len());
1518     (ori_link.range.start + after_first_backtick_group)
1519         ..(ori_link.range.start + before_second_backtick_group)
1520 }
1521
1522 /// Returns true if we should ignore `link` due to it being unlikely
1523 /// that it is an intra-doc link. `link` should still have disambiguators
1524 /// if there were any.
1525 ///
1526 /// The difference between this and [`should_ignore_link()`] is that this
1527 /// check should only be used on links that still have disambiguators.
1528 fn should_ignore_link_with_disambiguators(link: &str) -> bool {
1529     link.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;@()".contains(ch)))
1530 }
1531
1532 /// Returns true if we should ignore `path_str` due to it being unlikely
1533 /// that it is an intra-doc link.
1534 fn should_ignore_link(path_str: &str) -> bool {
1535     path_str.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;".contains(ch)))
1536 }
1537
1538 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
1539 /// Disambiguators for a link.
1540 crate enum Disambiguator {
1541     /// `prim@`
1542     ///
1543     /// This is buggy, see <https://github.com/rust-lang/rust/pull/77875#discussion_r503583103>
1544     Primitive,
1545     /// `struct@` or `f()`
1546     Kind(DefKind),
1547     /// `type@`
1548     Namespace(Namespace),
1549 }
1550
1551 impl Disambiguator {
1552     /// The text that should be displayed when the path is rendered as HTML.
1553     ///
1554     /// NOTE: `path` is not the original link given by the user, but a name suitable for passing to `resolve`.
1555     fn display_for(&self, path: &str) -> String {
1556         match self {
1557             // FIXME: this will have different output if the user had `m!()` originally.
1558             Self::Kind(DefKind::Macro(MacroKind::Bang)) => format!("{}!", path),
1559             Self::Kind(DefKind::Fn) => format!("{}()", path),
1560             _ => path.to_owned(),
1561         }
1562     }
1563
1564     /// Given a link, parse and return `(disambiguator, path_str)`.
1565     ///
1566     /// This returns `Ok(Some(...))` if a disambiguator was found,
1567     /// `Ok(None)` if no disambiguator was found, or `Err(...)`
1568     /// if there was a problem with the disambiguator.
1569     crate fn from_str(link: &str) -> Result<Option<(Self, &str)>, (String, Range<usize>)> {
1570         use Disambiguator::{Kind, Namespace as NS, Primitive};
1571
1572         if let Some(idx) = link.find('@') {
1573             let (prefix, rest) = link.split_at(idx);
1574             let d = match prefix {
1575                 "struct" => Kind(DefKind::Struct),
1576                 "enum" => Kind(DefKind::Enum),
1577                 "trait" => Kind(DefKind::Trait),
1578                 "union" => Kind(DefKind::Union),
1579                 "module" | "mod" => Kind(DefKind::Mod),
1580                 "const" | "constant" => Kind(DefKind::Const),
1581                 "static" => Kind(DefKind::Static),
1582                 "function" | "fn" | "method" => Kind(DefKind::Fn),
1583                 "derive" => Kind(DefKind::Macro(MacroKind::Derive)),
1584                 "type" => NS(Namespace::TypeNS),
1585                 "value" => NS(Namespace::ValueNS),
1586                 "macro" => NS(Namespace::MacroNS),
1587                 "prim" | "primitive" => Primitive,
1588                 _ => return Err((format!("unknown disambiguator `{}`", prefix), 0..idx)),
1589             };
1590             Ok(Some((d, &rest[1..])))
1591         } else {
1592             let suffixes = [
1593                 ("!()", DefKind::Macro(MacroKind::Bang)),
1594                 ("()", DefKind::Fn),
1595                 ("!", DefKind::Macro(MacroKind::Bang)),
1596             ];
1597             for &(suffix, kind) in &suffixes {
1598                 if let Some(link) = link.strip_suffix(suffix) {
1599                     // Avoid turning `!` or `()` into an empty string
1600                     if !link.is_empty() {
1601                         return Ok(Some((Kind(kind), link)));
1602                     }
1603                 }
1604             }
1605             Ok(None)
1606         }
1607     }
1608
1609     fn from_res(res: Res) -> Self {
1610         match res {
1611             Res::Def(kind, _) => Disambiguator::Kind(kind),
1612             Res::Primitive(_) => Disambiguator::Primitive,
1613         }
1614     }
1615
1616     /// Used for error reporting.
1617     fn suggestion(self) -> Suggestion {
1618         let kind = match self {
1619             Disambiguator::Primitive => return Suggestion::Prefix("prim"),
1620             Disambiguator::Kind(kind) => kind,
1621             Disambiguator::Namespace(_) => panic!("display_for cannot be used on namespaces"),
1622         };
1623         if kind == DefKind::Macro(MacroKind::Bang) {
1624             return Suggestion::Macro;
1625         } else if kind == DefKind::Fn || kind == DefKind::AssocFn {
1626             return Suggestion::Function;
1627         }
1628
1629         let prefix = match kind {
1630             DefKind::Struct => "struct",
1631             DefKind::Enum => "enum",
1632             DefKind::Trait => "trait",
1633             DefKind::Union => "union",
1634             DefKind::Mod => "mod",
1635             DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst => {
1636                 "const"
1637             }
1638             DefKind::Static => "static",
1639             DefKind::Macro(MacroKind::Derive) => "derive",
1640             // Now handle things that don't have a specific disambiguator
1641             _ => match kind
1642                 .ns()
1643                 .expect("tried to calculate a disambiguator for a def without a namespace?")
1644             {
1645                 Namespace::TypeNS => "type",
1646                 Namespace::ValueNS => "value",
1647                 Namespace::MacroNS => "macro",
1648             },
1649         };
1650
1651         Suggestion::Prefix(prefix)
1652     }
1653
1654     fn ns(self) -> Namespace {
1655         match self {
1656             Self::Namespace(n) => n,
1657             Self::Kind(k) => {
1658                 k.ns().expect("only DefKinds with a valid namespace can be disambiguators")
1659             }
1660             Self::Primitive => TypeNS,
1661         }
1662     }
1663
1664     fn article(self) -> &'static str {
1665         match self {
1666             Self::Namespace(_) => panic!("article() doesn't make sense for namespaces"),
1667             Self::Kind(k) => k.article(),
1668             Self::Primitive => "a",
1669         }
1670     }
1671
1672     fn descr(self) -> &'static str {
1673         match self {
1674             Self::Namespace(n) => n.descr(),
1675             // HACK(jynelson): by looking at the source I saw the DefId we pass
1676             // for `expected.descr()` doesn't matter, since it's not a crate
1677             Self::Kind(k) => k.descr(DefId::local(hir::def_id::DefIndex::from_usize(0))),
1678             Self::Primitive => "builtin type",
1679         }
1680     }
1681 }
1682
1683 /// A suggestion to show in a diagnostic.
1684 enum Suggestion {
1685     /// `struct@`
1686     Prefix(&'static str),
1687     /// `f()`
1688     Function,
1689     /// `m!`
1690     Macro,
1691 }
1692
1693 impl Suggestion {
1694     fn descr(&self) -> Cow<'static, str> {
1695         match self {
1696             Self::Prefix(x) => format!("prefix with `{}@`", x).into(),
1697             Self::Function => "add parentheses".into(),
1698             Self::Macro => "add an exclamation mark".into(),
1699         }
1700     }
1701
1702     fn as_help(&self, path_str: &str) -> String {
1703         // FIXME: if this is an implied shortcut link, it's bad style to suggest `@`
1704         match self {
1705             Self::Prefix(prefix) => format!("{}@{}", prefix, path_str),
1706             Self::Function => format!("{}()", path_str),
1707             Self::Macro => format!("{}!", path_str),
1708         }
1709     }
1710 }
1711
1712 /// Reports a diagnostic for an intra-doc link.
1713 ///
1714 /// If no link range is provided, or the source span of the link cannot be determined, the span of
1715 /// the entire documentation block is used for the lint. If a range is provided but the span
1716 /// calculation fails, a note is added to the diagnostic pointing to the link in the markdown.
1717 ///
1718 /// The `decorate` callback is invoked in all cases to allow further customization of the
1719 /// diagnostic before emission. If the span of the link was able to be determined, the second
1720 /// parameter of the callback will contain it, and the primary span of the diagnostic will be set
1721 /// to it.
1722 fn report_diagnostic(
1723     tcx: TyCtxt<'_>,
1724     lint: &'static Lint,
1725     msg: &str,
1726     item: &Item,
1727     dox: &str,
1728     link_range: &Range<usize>,
1729     decorate: impl FnOnce(&mut DiagnosticBuilder<'_>, Option<rustc_span::Span>),
1730 ) {
1731     let hir_id = match DocContext::as_local_hir_id(tcx, item.def_id) {
1732         Some(hir_id) => hir_id,
1733         None => {
1734             // If non-local, no need to check anything.
1735             info!("ignoring warning from parent crate: {}", msg);
1736             return;
1737         }
1738     };
1739
1740     let attrs = &item.attrs;
1741     let sp = span_of_attrs(attrs).unwrap_or(item.span.inner());
1742
1743     tcx.struct_span_lint_hir(lint, hir_id, sp, |lint| {
1744         let mut diag = lint.build(msg);
1745
1746         let span = super::source_span_for_markdown_range(tcx, dox, link_range, attrs);
1747
1748         if let Some(sp) = span {
1749             diag.set_span(sp);
1750         } else {
1751             // blah blah blah\nblah\nblah [blah] blah blah\nblah blah
1752             //                       ^     ~~~~
1753             //                       |     link_range
1754             //                       last_new_line_offset
1755             let last_new_line_offset = dox[..link_range.start].rfind('\n').map_or(0, |n| n + 1);
1756             let line = dox[last_new_line_offset..].lines().next().unwrap_or("");
1757
1758             // Print the line containing the `link_range` and manually mark it with '^'s.
1759             diag.note(&format!(
1760                 "the link appears in this line:\n\n{line}\n\
1761                      {indicator: <before$}{indicator:^<found$}",
1762                 line = line,
1763                 indicator = "",
1764                 before = link_range.start - last_new_line_offset,
1765                 found = link_range.len(),
1766             ));
1767         }
1768
1769         decorate(&mut diag, span);
1770
1771         diag.emit();
1772     });
1773 }
1774
1775 /// Reports a link that failed to resolve.
1776 ///
1777 /// This also tries to resolve any intermediate path segments that weren't
1778 /// handled earlier. For example, if passed `Item::Crate(std)` and `path_str`
1779 /// `std::io::Error::x`, this will resolve `std::io::Error`.
1780 fn resolution_failure(
1781     collector: &mut LinkCollector<'_, '_>,
1782     item: &Item,
1783     path_str: &str,
1784     disambiguator: Option<Disambiguator>,
1785     dox: &str,
1786     link_range: Range<usize>,
1787     kinds: SmallVec<[ResolutionFailure<'_>; 3]>,
1788 ) {
1789     let tcx = collector.cx.tcx;
1790     report_diagnostic(
1791         tcx,
1792         BROKEN_INTRA_DOC_LINKS,
1793         &format!("unresolved link to `{}`", path_str),
1794         item,
1795         dox,
1796         &link_range,
1797         |diag, sp| {
1798             let item = |res: Res| format!("the {} `{}`", res.descr(), res.name(tcx),);
1799             let assoc_item_not_allowed = |res: Res| {
1800                 let name = res.name(tcx);
1801                 format!(
1802                     "`{}` is {} {}, not a module or type, and cannot have associated items",
1803                     name,
1804                     res.article(),
1805                     res.descr()
1806                 )
1807             };
1808             // ignore duplicates
1809             let mut variants_seen = SmallVec::<[_; 3]>::new();
1810             for mut failure in kinds {
1811                 let variant = std::mem::discriminant(&failure);
1812                 if variants_seen.contains(&variant) {
1813                     continue;
1814                 }
1815                 variants_seen.push(variant);
1816
1817                 if let ResolutionFailure::NotResolved { module_id, partial_res, unresolved } =
1818                     &mut failure
1819                 {
1820                     use DefKind::*;
1821
1822                     let module_id = *module_id;
1823                     // FIXME(jynelson): this might conflict with my `Self` fix in #76467
1824                     // FIXME: maybe use itertools `collect_tuple` instead?
1825                     fn split(path: &str) -> Option<(&str, &str)> {
1826                         let mut splitter = path.rsplitn(2, "::");
1827                         splitter.next().and_then(|right| splitter.next().map(|left| (left, right)))
1828                     }
1829
1830                     // Check if _any_ parent of the path gets resolved.
1831                     // If so, report it and say the first which failed; if not, say the first path segment didn't resolve.
1832                     let mut name = path_str;
1833                     'outer: loop {
1834                         let (start, end) = if let Some(x) = split(name) {
1835                             x
1836                         } else {
1837                             // avoid bug that marked [Quux::Z] as missing Z, not Quux
1838                             if partial_res.is_none() {
1839                                 *unresolved = name.into();
1840                             }
1841                             break;
1842                         };
1843                         name = start;
1844                         for &ns in &[TypeNS, ValueNS, MacroNS] {
1845                             if let Some(res) =
1846                                 collector.check_full_res(ns, &start, module_id, &None)
1847                             {
1848                                 debug!("found partial_res={:?}", res);
1849                                 *partial_res = Some(res);
1850                                 *unresolved = end.into();
1851                                 break 'outer;
1852                             }
1853                         }
1854                         *unresolved = end.into();
1855                     }
1856
1857                     let last_found_module = match *partial_res {
1858                         Some(Res::Def(DefKind::Mod, id)) => Some(id),
1859                         None => Some(module_id),
1860                         _ => None,
1861                     };
1862                     // See if this was a module: `[path]` or `[std::io::nope]`
1863                     if let Some(module) = last_found_module {
1864                         let note = if partial_res.is_some() {
1865                             // Part of the link resolved; e.g. `std::io::nonexistent`
1866                             let module_name = tcx.item_name(module);
1867                             format!("no item named `{}` in module `{}`", unresolved, module_name)
1868                         } else {
1869                             // None of the link resolved; e.g. `Notimported`
1870                             format!("no item named `{}` in scope", unresolved)
1871                         };
1872                         if let Some(span) = sp {
1873                             diag.span_label(span, &note);
1874                         } else {
1875                             diag.note(&note);
1876                         }
1877
1878                         // If the link has `::` in it, assume it was meant to be an intra-doc link.
1879                         // Otherwise, the `[]` might be unrelated.
1880                         // FIXME: don't show this for autolinks (`<>`), `()` style links, or reference links
1881                         if !path_str.contains("::") {
1882                             diag.help(r#"to escape `[` and `]` characters, add '\' before them like `\[` or `\]`"#);
1883                         }
1884
1885                         continue;
1886                     }
1887
1888                     // Otherwise, it must be an associated item or variant
1889                     let res = partial_res.expect("None case was handled by `last_found_module`");
1890                     let name = res.name(tcx);
1891                     let kind = match res {
1892                         Res::Def(kind, _) => Some(kind),
1893                         Res::Primitive(_) => None,
1894                     };
1895                     let path_description = if let Some(kind) = kind {
1896                         match kind {
1897                             Mod | ForeignMod => "inner item",
1898                             Struct => "field or associated item",
1899                             Enum | Union => "variant or associated item",
1900                             Variant
1901                             | Field
1902                             | Closure
1903                             | Generator
1904                             | AssocTy
1905                             | AssocConst
1906                             | AssocFn
1907                             | Fn
1908                             | Macro(_)
1909                             | Const
1910                             | ConstParam
1911                             | ExternCrate
1912                             | Use
1913                             | LifetimeParam
1914                             | Ctor(_, _)
1915                             | AnonConst => {
1916                                 let note = assoc_item_not_allowed(res);
1917                                 if let Some(span) = sp {
1918                                     diag.span_label(span, &note);
1919                                 } else {
1920                                     diag.note(&note);
1921                                 }
1922                                 return;
1923                             }
1924                             Trait | TyAlias | ForeignTy | OpaqueTy | TraitAlias | TyParam
1925                             | Static => "associated item",
1926                             Impl | GlobalAsm => unreachable!("not a path"),
1927                         }
1928                     } else {
1929                         "associated item"
1930                     };
1931                     let note = format!(
1932                         "the {} `{}` has no {} named `{}`",
1933                         res.descr(),
1934                         name,
1935                         disambiguator.map_or(path_description, |d| d.descr()),
1936                         unresolved,
1937                     );
1938                     if let Some(span) = sp {
1939                         diag.span_label(span, &note);
1940                     } else {
1941                         diag.note(&note);
1942                     }
1943
1944                     continue;
1945                 }
1946                 let note = match failure {
1947                     ResolutionFailure::NotResolved { .. } => unreachable!("handled above"),
1948                     ResolutionFailure::Dummy => continue,
1949                     ResolutionFailure::WrongNamespace { res, expected_ns } => {
1950                         if let Res::Def(kind, _) = res {
1951                             let disambiguator = Disambiguator::Kind(kind);
1952                             suggest_disambiguator(
1953                                 disambiguator,
1954                                 diag,
1955                                 path_str,
1956                                 dox,
1957                                 sp,
1958                                 &link_range,
1959                             )
1960                         }
1961
1962                         format!(
1963                             "this link resolves to {}, which is not in the {} namespace",
1964                             item(res),
1965                             expected_ns.descr()
1966                         )
1967                     }
1968                     ResolutionFailure::NoParentItem => {
1969                         diag.level = rustc_errors::Level::Bug;
1970                         "all intra-doc links should have a parent item".to_owned()
1971                     }
1972                     ResolutionFailure::MalformedGenerics(variant) => match variant {
1973                         MalformedGenerics::UnbalancedAngleBrackets => {
1974                             String::from("unbalanced angle brackets")
1975                         }
1976                         MalformedGenerics::MissingType => {
1977                             String::from("missing type for generic parameters")
1978                         }
1979                         MalformedGenerics::HasFullyQualifiedSyntax => {
1980                             diag.note("see https://github.com/rust-lang/rust/issues/74563 for more information");
1981                             String::from("fully-qualified syntax is unsupported")
1982                         }
1983                         MalformedGenerics::InvalidPathSeparator => {
1984                             String::from("has invalid path separator")
1985                         }
1986                         MalformedGenerics::TooManyAngleBrackets => {
1987                             String::from("too many angle brackets")
1988                         }
1989                         MalformedGenerics::EmptyAngleBrackets => {
1990                             String::from("empty angle brackets")
1991                         }
1992                     },
1993                 };
1994                 if let Some(span) = sp {
1995                     diag.span_label(span, &note);
1996                 } else {
1997                     diag.note(&note);
1998                 }
1999             }
2000         },
2001     );
2002 }
2003
2004 /// Report an anchor failure.
2005 fn anchor_failure(
2006     cx: &DocContext<'_>,
2007     item: &Item,
2008     path_str: &str,
2009     dox: &str,
2010     link_range: Range<usize>,
2011     failure: AnchorFailure,
2012 ) {
2013     let msg = match failure {
2014         AnchorFailure::MultipleAnchors => format!("`{}` contains multiple anchors", path_str),
2015         AnchorFailure::RustdocAnchorConflict(res) => format!(
2016             "`{}` contains an anchor, but links to {kind}s are already anchored",
2017             path_str,
2018             kind = res.descr(),
2019         ),
2020     };
2021
2022     report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, item, dox, &link_range, |diag, sp| {
2023         if let Some(sp) = sp {
2024             diag.span_label(sp, "contains invalid anchor");
2025         }
2026     });
2027 }
2028
2029 /// Report an error in the link disambiguator.
2030 fn disambiguator_error(
2031     cx: &DocContext<'_>,
2032     item: &Item,
2033     dox: &str,
2034     link_range: Range<usize>,
2035     msg: &str,
2036 ) {
2037     report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, msg, item, dox, &link_range, |_diag, _sp| {});
2038 }
2039
2040 /// Report an ambiguity error, where there were multiple possible resolutions.
2041 fn ambiguity_error(
2042     cx: &DocContext<'_>,
2043     item: &Item,
2044     path_str: &str,
2045     dox: &str,
2046     link_range: Range<usize>,
2047     candidates: Vec<Res>,
2048 ) {
2049     let mut msg = format!("`{}` is ", path_str);
2050
2051     match candidates.as_slice() {
2052         [first_def, second_def] => {
2053             msg += &format!(
2054                 "both {} {} and {} {}",
2055                 first_def.article(),
2056                 first_def.descr(),
2057                 second_def.article(),
2058                 second_def.descr(),
2059             );
2060         }
2061         _ => {
2062             let mut candidates = candidates.iter().peekable();
2063             while let Some(res) = candidates.next() {
2064                 if candidates.peek().is_some() {
2065                     msg += &format!("{} {}, ", res.article(), res.descr());
2066                 } else {
2067                     msg += &format!("and {} {}", res.article(), res.descr());
2068                 }
2069             }
2070         }
2071     }
2072
2073     report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, item, dox, &link_range, |diag, sp| {
2074         if let Some(sp) = sp {
2075             diag.span_label(sp, "ambiguous link");
2076         } else {
2077             diag.note("ambiguous link");
2078         }
2079
2080         for res in candidates {
2081             let disambiguator = Disambiguator::from_res(res);
2082             suggest_disambiguator(disambiguator, diag, path_str, dox, sp, &link_range);
2083         }
2084     });
2085 }
2086
2087 /// In case of an ambiguity or mismatched disambiguator, suggest the correct
2088 /// disambiguator.
2089 fn suggest_disambiguator(
2090     disambiguator: Disambiguator,
2091     diag: &mut DiagnosticBuilder<'_>,
2092     path_str: &str,
2093     dox: &str,
2094     sp: Option<rustc_span::Span>,
2095     link_range: &Range<usize>,
2096 ) {
2097     let suggestion = disambiguator.suggestion();
2098     let help = format!("to link to the {}, {}", disambiguator.descr(), suggestion.descr());
2099
2100     if let Some(sp) = sp {
2101         let msg = if dox.bytes().nth(link_range.start) == Some(b'`') {
2102             format!("`{}`", suggestion.as_help(path_str))
2103         } else {
2104             suggestion.as_help(path_str)
2105         };
2106
2107         diag.span_suggestion(sp, &help, msg, Applicability::MaybeIncorrect);
2108     } else {
2109         diag.help(&format!("{}: {}", help, suggestion.as_help(path_str)));
2110     }
2111 }
2112
2113 /// Report a link from a public item to a private one.
2114 fn privacy_error(cx: &DocContext<'_>, item: &Item, path_str: &str, dox: &str, link: &MarkdownLink) {
2115     let sym;
2116     let item_name = match item.name {
2117         Some(name) => {
2118             sym = name.as_str();
2119             &*sym
2120         }
2121         None => "<unknown>",
2122     };
2123     let msg =
2124         format!("public documentation for `{}` links to private item `{}`", item_name, path_str);
2125
2126     report_diagnostic(cx.tcx, PRIVATE_INTRA_DOC_LINKS, &msg, item, dox, &link.range, |diag, sp| {
2127         if let Some(sp) = sp {
2128             diag.span_label(sp, "this item is private");
2129         }
2130
2131         let note_msg = if cx.render_options.document_private {
2132             "this link resolves only because you passed `--document-private-items`, but will break without"
2133         } else {
2134             "this link will resolve properly if you pass `--document-private-items`"
2135         };
2136         diag.note(note_msg);
2137     });
2138 }
2139
2140 /// Given an enum variant's res, return the res of its enum and the associated fragment.
2141 fn handle_variant(
2142     cx: &DocContext<'_>,
2143     res: Res,
2144     extra_fragment: &Option<String>,
2145 ) -> Result<(Res, Option<String>), ErrorKind<'static>> {
2146     use rustc_middle::ty::DefIdTree;
2147
2148     if extra_fragment.is_some() {
2149         return Err(ErrorKind::AnchorFailure(AnchorFailure::RustdocAnchorConflict(res)));
2150     }
2151     cx.tcx
2152         .parent(res.def_id())
2153         .map(|parent| {
2154             let parent_def = Res::Def(DefKind::Enum, parent);
2155             let variant = cx.tcx.expect_variant_res(res.as_hir_res().unwrap());
2156             (parent_def, Some(format!("variant.{}", variant.ident.name)))
2157         })
2158         .ok_or_else(|| ResolutionFailure::NoParentItem.into())
2159 }
2160
2161 /// Resolve a primitive type or value.
2162 fn resolve_primitive(path_str: &str, ns: Namespace) -> Option<Res> {
2163     if ns != TypeNS {
2164         return None;
2165     }
2166     use PrimitiveType::*;
2167     let prim = match path_str {
2168         "isize" => Isize,
2169         "i8" => I8,
2170         "i16" => I16,
2171         "i32" => I32,
2172         "i64" => I64,
2173         "i128" => I128,
2174         "usize" => Usize,
2175         "u8" => U8,
2176         "u16" => U16,
2177         "u32" => U32,
2178         "u64" => U64,
2179         "u128" => U128,
2180         "f32" => F32,
2181         "f64" => F64,
2182         "char" => Char,
2183         "bool" | "true" | "false" => Bool,
2184         "str" | "&str" => Str,
2185         // See #80181 for why these don't have symbols associated.
2186         "slice" => Slice,
2187         "array" => Array,
2188         "tuple" => Tuple,
2189         "unit" => Unit,
2190         "pointer" | "*const" | "*mut" => RawPointer,
2191         "reference" | "&" | "&mut" => Reference,
2192         "fn" => Fn,
2193         "never" | "!" => Never,
2194         _ => return None,
2195     };
2196     debug!("resolved primitives {:?}", prim);
2197     Some(Res::Primitive(prim))
2198 }
2199
2200 fn strip_generics_from_path(path_str: &str) -> Result<String, ResolutionFailure<'static>> {
2201     let mut stripped_segments = vec![];
2202     let mut path = path_str.chars().peekable();
2203     let mut segment = Vec::new();
2204
2205     while let Some(chr) = path.next() {
2206         match chr {
2207             ':' => {
2208                 if path.next_if_eq(&':').is_some() {
2209                     let stripped_segment =
2210                         strip_generics_from_path_segment(mem::take(&mut segment))?;
2211                     if !stripped_segment.is_empty() {
2212                         stripped_segments.push(stripped_segment);
2213                     }
2214                 } else {
2215                     return Err(ResolutionFailure::MalformedGenerics(
2216                         MalformedGenerics::InvalidPathSeparator,
2217                     ));
2218                 }
2219             }
2220             '<' => {
2221                 segment.push(chr);
2222
2223                 match path.next() {
2224                     Some('<') => {
2225                         return Err(ResolutionFailure::MalformedGenerics(
2226                             MalformedGenerics::TooManyAngleBrackets,
2227                         ));
2228                     }
2229                     Some('>') => {
2230                         return Err(ResolutionFailure::MalformedGenerics(
2231                             MalformedGenerics::EmptyAngleBrackets,
2232                         ));
2233                     }
2234                     Some(chr) => {
2235                         segment.push(chr);
2236
2237                         while let Some(chr) = path.next_if(|c| *c != '>') {
2238                             segment.push(chr);
2239                         }
2240                     }
2241                     None => break,
2242                 }
2243             }
2244             _ => segment.push(chr),
2245         }
2246         trace!("raw segment: {:?}", segment);
2247     }
2248
2249     if !segment.is_empty() {
2250         let stripped_segment = strip_generics_from_path_segment(segment)?;
2251         if !stripped_segment.is_empty() {
2252             stripped_segments.push(stripped_segment);
2253         }
2254     }
2255
2256     debug!("path_str: {:?}\nstripped segments: {:?}", path_str, &stripped_segments);
2257
2258     let stripped_path = stripped_segments.join("::");
2259
2260     if !stripped_path.is_empty() {
2261         Ok(stripped_path)
2262     } else {
2263         Err(ResolutionFailure::MalformedGenerics(MalformedGenerics::MissingType))
2264     }
2265 }
2266
2267 fn strip_generics_from_path_segment(
2268     segment: Vec<char>,
2269 ) -> Result<String, ResolutionFailure<'static>> {
2270     let mut stripped_segment = String::new();
2271     let mut param_depth = 0;
2272
2273     let mut latest_generics_chunk = String::new();
2274
2275     for c in segment {
2276         if c == '<' {
2277             param_depth += 1;
2278             latest_generics_chunk.clear();
2279         } else if c == '>' {
2280             param_depth -= 1;
2281             if latest_generics_chunk.contains(" as ") {
2282                 // The segment tries to use fully-qualified syntax, which is currently unsupported.
2283                 // Give a helpful error message instead of completely ignoring the angle brackets.
2284                 return Err(ResolutionFailure::MalformedGenerics(
2285                     MalformedGenerics::HasFullyQualifiedSyntax,
2286                 ));
2287             }
2288         } else {
2289             if param_depth == 0 {
2290                 stripped_segment.push(c);
2291             } else {
2292                 latest_generics_chunk.push(c);
2293             }
2294         }
2295     }
2296
2297     if param_depth == 0 {
2298         Ok(stripped_segment)
2299     } else {
2300         // The segment has unbalanced angle brackets, e.g. `Vec<T` or `Vec<T>>`
2301         Err(ResolutionFailure::MalformedGenerics(MalformedGenerics::UnbalancedAngleBrackets))
2302     }
2303 }