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