src/librustdoc/passes/collect_intra_doc_links.rs

   1 use rustc_ast as ast;
   2 use rustc_data_structures::stable_set::FxHashSet;
   3 use rustc_errors::{Applicability, DiagnosticBuilder};
   4 use rustc_expand::base::SyntaxExtensionKind;
   5 use rustc_feature::UnstableFeatures;
   6 use rustc_hir as hir;
   7 use rustc_hir::def::{
   8     DefKind,
   9     Namespace::{self, *},
  10     PerNS, Res,
  11 };
  12 use rustc_hir::def_id::DefId;
  13 use rustc_middle::ty;
  14 use rustc_resolve::ParentScope;
  15 use rustc_session::lint;
  16 use rustc_span::hygiene::MacroKind;
  17 use rustc_span::symbol::Ident;
  18 use rustc_span::symbol::Symbol;
  19 use rustc_span::DUMMY_SP;
  20 use smallvec::SmallVec;
  21
  22 use std::cell::Cell;
  23 use std::ops::Range;
  24
  25 use crate::clean::*;
  26 use crate::core::DocContext;
  27 use crate::fold::DocFolder;
  28 use crate::html::markdown::markdown_links;
  29 use crate::passes::Pass;
  30
  31 use super::span_of_attrs;
  32
  33 pub const COLLECT_INTRA_DOC_LINKS: Pass = Pass {
  34     name: "collect-intra-doc-links",
  35     run: collect_intra_doc_links,
  36     description: "reads a crate's documentation to resolve intra-doc-links",
  37 };
  38
  39 pub fn collect_intra_doc_links(krate: Crate, cx: &DocContext<'_>) -> Crate {
  40     if !UnstableFeatures::from_environment().is_nightly_build() {
  41         krate
  42     } else {
  43         let mut coll = LinkCollector::new(cx);
  44
  45         coll.fold_crate(krate)
  46     }
  47 }
  48
  49 enum ErrorKind {
  50     ResolutionFailure,
  51     AnchorFailure(AnchorFailure),
  52 }
  53
  54 enum AnchorFailure {
  55     MultipleAnchors,
  56     Primitive,
  57     Variant,
  58     AssocConstant,
  59     AssocType,
  60     Field,
  61     Method,
  62 }
  63
  64 struct LinkCollector<'a, 'tcx> {
  65     cx: &'a DocContext<'tcx>,
  66     // NOTE: this may not necessarily be a module in the current crate
  67     mod_ids: Vec<DefId>,
  68     /// This is used to store the kind of associated items,
  69     /// because `clean` and the disambiguator code expect them to be different.
  70     /// See the code for associated items on inherent impls for details.
  71     kind_side_channel: Cell<Option<DefKind>>,
  72 }
  73
  74 impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
  75     fn new(cx: &'a DocContext<'tcx>) -> Self {
  76         LinkCollector { cx, mod_ids: Vec::new(), kind_side_channel: Cell::new(None) }
  77     }
  78
  79     fn variant_field(
  80         &self,
  81         path_str: &str,
  82         current_item: &Option<String>,
  83         module_id: DefId,
  84     ) -> Result<(Res, Option<String>), ErrorKind> {
  85         let cx = self.cx;
  86
  87         let mut split = path_str.rsplitn(3, "::");
  88         let variant_field_name =
  89             split.next().map(|f| Symbol::intern(f)).ok_or(ErrorKind::ResolutionFailure)?;
  90         let variant_name =
  91             split.next().map(|f| Symbol::intern(f)).ok_or(ErrorKind::ResolutionFailure)?;
  92         let path = split
  93             .next()
  94             .map(|f| {
  95                 if f == "self" || f == "Self" {
  96                     if let Some(name) = current_item.as_ref() {
  97                         return name.clone();
  98                     }
  99                 }
 100                 f.to_owned()
 101             })
 102             .ok_or(ErrorKind::ResolutionFailure)?;
 103         let (_, ty_res) = cx
 104             .enter_resolver(|resolver| {
 105                 resolver.resolve_str_path_error(DUMMY_SP, &path, TypeNS, module_id)
 106             })
 107             .map_err(|_| ErrorKind::ResolutionFailure)?;
 108         if let Res::Err = ty_res {
 109             return Err(ErrorKind::ResolutionFailure);
 110         }
 111         let ty_res = ty_res.map_id(|_| panic!("unexpected node_id"));
 112         match ty_res {
 113             Res::Def(DefKind::Enum, did) => {
 114                 if cx
 115                     .tcx
 116                     .inherent_impls(did)
 117                     .iter()
 118                     .flat_map(|imp| cx.tcx.associated_items(*imp).in_definition_order())
 119                     .any(|item| item.ident.name == variant_name)
 120                 {
 121                     return Err(ErrorKind::ResolutionFailure);
 122                 }
 123                 match cx.tcx.type_of(did).kind() {
 124                     ty::Adt(def, _) if def.is_enum() => {
 125                         if def.all_fields().any(|item| item.ident.name == variant_field_name) {
 126                             Ok((
 127                                 ty_res,
 128                                 Some(format!(
 129                                     "variant.{}.field.{}",
 130                                     variant_name, variant_field_name
 131                                 )),
 132                             ))
 133                         } else {
 134                             Err(ErrorKind::ResolutionFailure)
 135                         }
 136                     }
 137                     _ => Err(ErrorKind::ResolutionFailure),
 138                 }
 139             }
 140             _ => Err(ErrorKind::ResolutionFailure),
 141         }
 142     }
 143
 144     /// Resolves a string as a macro.
 145     fn macro_resolve(&self, path_str: &str, parent_id: Option<DefId>) -> Option<Res> {
 146         let cx = self.cx;
 147         let path = ast::Path::from_ident(Ident::from_str(path_str));
 148         cx.enter_resolver(|resolver| {
 149             if let Ok((Some(ext), res)) = resolver.resolve_macro_path(
 150                 &path,
 151                 None,
 152                 &ParentScope::module(resolver.graph_root()),
 153                 false,
 154                 false,
 155             ) {
 156                 if let SyntaxExtensionKind::LegacyBang { .. } = ext.kind {
 157                     return Some(res.map_id(|_| panic!("unexpected id")));
 158                 }
 159             }
 160             if let Some(res) = resolver.all_macros().get(&Symbol::intern(path_str)) {
 161                 return Some(res.map_id(|_| panic!("unexpected id")));
 162             }
 163             if let Some(module_id) = parent_id {
 164                 debug!("resolving {} as a macro in the module {:?}", path_str, module_id);
 165                 if let Ok((_, res)) =
 166                     resolver.resolve_str_path_error(DUMMY_SP, path_str, MacroNS, module_id)
 167                 {
 168                     // don't resolve builtins like `#[derive]`
 169                     if let Res::Def(..) = res {
 170                         let res = res.map_id(|_| panic!("unexpected node_id"));
 171                         return Some(res);
 172                     }
 173                 }
 174             } else {
 175                 debug!("attempting to resolve item without parent module: {}", path_str);
 176             }
 177             None
 178         })
 179     }
 180     /// Resolves a string as a path within a particular namespace. Also returns an optional
 181     /// URL fragment in the case of variants and methods.
 182     fn resolve(
 183         &self,
 184         path_str: &str,
 185         ns: Namespace,
 186         current_item: &Option<String>,
 187         parent_id: Option<DefId>,
 188         extra_fragment: &Option<String>,
 189     ) -> Result<(Res, Option<String>), ErrorKind> {
 190         let cx = self.cx;
 191
 192         // In case we're in a module, try to resolve the relative path.
 193         if let Some(module_id) = parent_id {
 194             let result = cx.enter_resolver(|resolver| {
 195                 resolver.resolve_str_path_error(DUMMY_SP, &path_str, ns, module_id)
 196             });
 197             debug!("{} resolved to {:?} in namespace {:?}", path_str, result, ns);
 198             let result = match result {
 199                 Ok((_, Res::Err)) => Err(ErrorKind::ResolutionFailure),
 200                 _ => result.map_err(|_| ErrorKind::ResolutionFailure),
 201             };
 202
 203             if let Ok((_, res)) = result {
 204                 let res = res.map_id(|_| panic!("unexpected node_id"));
 205                 // In case this is a trait item, skip the
 206                 // early return and try looking for the trait.
 207                 let value = match res {
 208                     Res::Def(DefKind::AssocFn | DefKind::AssocConst, _) => true,
 209                     Res::Def(DefKind::AssocTy, _) => false,
 210                     Res::Def(DefKind::Variant, _) => {
 211                         return handle_variant(cx, res, extra_fragment);
 212                     }
 213                     // Not a trait item; just return what we found.
 214                     Res::PrimTy(..) => {
 215                         if extra_fragment.is_some() {
 216                             return Err(ErrorKind::AnchorFailure(AnchorFailure::Primitive));
 217                         }
 218                         return Ok((res, Some(path_str.to_owned())));
 219                     }
 220                     Res::Def(DefKind::Mod, _) => {
 221                         return Ok((res, extra_fragment.clone()));
 222                     }
 223                     _ => {
 224                         return Ok((res, extra_fragment.clone()));
 225                     }
 226                 };
 227
 228                 if value != (ns == ValueNS) {
 229                     return Err(ErrorKind::ResolutionFailure);
 230                 }
 231             } else if let Some((path, prim)) = is_primitive(path_str, ns) {
 232                 if extra_fragment.is_some() {
 233                     return Err(ErrorKind::AnchorFailure(AnchorFailure::Primitive));
 234                 }
 235                 return Ok((prim, Some(path.to_owned())));
 236             }
 237
 238             // Try looking for methods and associated items.
 239             let mut split = path_str.rsplitn(2, "::");
 240             let item_name =
 241                 split.next().map(|f| Symbol::intern(f)).ok_or(ErrorKind::ResolutionFailure)?;
 242             let path = split
 243                 .next()
 244                 .map(|f| {
 245                     if f == "self" || f == "Self" {
 246                         if let Some(name) = current_item.as_ref() {
 247                             return name.clone();
 248                         }
 249                     }
 250                     f.to_owned()
 251                 })
 252                 .ok_or(ErrorKind::ResolutionFailure)?;
 253
 254             if let Some((path, prim)) = is_primitive(&path, TypeNS) {
 255                 for &impl_ in primitive_impl(cx, &path).ok_or(ErrorKind::ResolutionFailure)? {
 256                     let link = cx
 257                         .tcx
 258                         .associated_items(impl_)
 259                         .find_by_name_and_namespace(
 260                             cx.tcx,
 261                             Ident::with_dummy_span(item_name),
 262                             ns,
 263                             impl_,
 264                         )
 265                         .map(|item| match item.kind {
 266                             ty::AssocKind::Fn => "method",
 267                             ty::AssocKind::Const => "associatedconstant",
 268                             ty::AssocKind::Type => "associatedtype",
 269                         })
 270                         .map(|out| (prim, Some(format!("{}#{}.{}", path, out, item_name))));
 271                     if let Some(link) = link {
 272                         return Ok(link);
 273                     }
 274                 }
 275                 return Err(ErrorKind::ResolutionFailure);
 276             }
 277
 278             let (_, ty_res) = cx
 279                 .enter_resolver(|resolver| {
 280                     resolver.resolve_str_path_error(DUMMY_SP, &path, TypeNS, module_id)
 281                 })
 282                 .map_err(|_| ErrorKind::ResolutionFailure)?;
 283             if let Res::Err = ty_res {
 284                 return if ns == Namespace::ValueNS {
 285                     self.variant_field(path_str, current_item, module_id)
 286                 } else {
 287                     Err(ErrorKind::ResolutionFailure)
 288                 };
 289             }
 290             let ty_res = ty_res.map_id(|_| panic!("unexpected node_id"));
 291             let res = match ty_res {
 292                 Res::Def(
 293                     DefKind::Struct | DefKind::Union | DefKind::Enum | DefKind::TyAlias,
 294                     did,
 295                 ) => {
 296                     debug!("looking for associated item named {} for item {:?}", item_name, did);
 297                     // Checks if item_name belongs to `impl SomeItem`
 298                     let kind = cx
 299                         .tcx
 300                         .inherent_impls(did)
 301                         .iter()
 302                         .flat_map(|&imp| {
 303                             cx.tcx.associated_items(imp).find_by_name_and_namespace(
 304                                 cx.tcx,
 305                                 Ident::with_dummy_span(item_name),
 306                                 ns,
 307                                 imp,
 308                             )
 309                         })
 310                         .map(|item| item.kind)
 311                         // There should only ever be one associated item that matches from any inherent impl
 312                         .next()
 313                         // Check if item_name belongs to `impl SomeTrait for SomeItem`
 314                         // This gives precedence to `impl SomeItem`:
 315                         // Although having both would be ambiguous, use impl version for compat. sake.
 316                         // To handle that properly resolve() would have to support
 317                         // something like [`ambi_fn`](<SomeStruct as SomeTrait>::ambi_fn)
 318                         .or_else(|| {
 319                             let kind = resolve_associated_trait_item(
 320                                 did, module_id, item_name, ns, &self.cx,
 321                             );
 322                             debug!("got associated item kind {:?}", kind);
 323                             kind
 324                         });
 325
 326                     if let Some(kind) = kind {
 327                         let out = match kind {
 328                             ty::AssocKind::Fn => "method",
 329                             ty::AssocKind::Const => "associatedconstant",
 330                             ty::AssocKind::Type => "associatedtype",
 331                         };
 332                         Some(if extra_fragment.is_some() {
 333                             Err(ErrorKind::AnchorFailure(if kind == ty::AssocKind::Fn {
 334                                 AnchorFailure::Method
 335                             } else {
 336                                 AnchorFailure::AssocConstant
 337                             }))
 338                         } else {
 339                             // HACK(jynelson): `clean` expects the type, not the associated item.
 340                             // but the disambiguator logic expects the associated item.
 341                             // Store the kind in a side channel so that only the disambiguator logic looks at it.
 342                             self.kind_side_channel.set(Some(kind.as_def_kind()));
 343                             Ok((ty_res, Some(format!("{}.{}", out, item_name))))
 344                         })
 345                     } else if ns == Namespace::ValueNS {
 346                         match cx.tcx.type_of(did).kind() {
 347                             ty::Adt(def, _) => {
 348                                 let field = if def.is_enum() {
 349                                     def.all_fields().find(|item| item.ident.name == item_name)
 350                                 } else {
 351                                     def.non_enum_variant()
 352                                         .fields
 353                                         .iter()
 354                                         .find(|item| item.ident.name == item_name)
 355                                 };
 356                                 field.map(|item| {
 357                                     if extra_fragment.is_some() {
 358                                         Err(ErrorKind::AnchorFailure(if def.is_enum() {
 359                                             AnchorFailure::Variant
 360                                         } else {
 361                                             AnchorFailure::Field
 362                                         }))
 363                                     } else {
 364                                         Ok((
 365                                             ty_res,
 366                                             Some(format!(
 367                                                 "{}.{}",
 368                                                 if def.is_enum() {
 369                                                     "variant"
 370                                                 } else {
 371                                                     "structfield"
 372                                                 },
 373                                                 item.ident
 374                                             )),
 375                                         ))
 376                                     }
 377                                 })
 378                             }
 379                             _ => None,
 380                         }
 381                     } else {
 382                         // We already know this isn't in ValueNS, so no need to check variant_field
 383                         return Err(ErrorKind::ResolutionFailure);
 384                     }
 385                 }
 386                 Res::Def(DefKind::Trait, did) => cx
 387                     .tcx
 388                     .associated_items(did)
 389                     .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, did)
 390                     .map(|item| {
 391                         let kind = match item.kind {
 392                             ty::AssocKind::Const => "associatedconstant",
 393                             ty::AssocKind::Type => "associatedtype",
 394                             ty::AssocKind::Fn => {
 395                                 if item.defaultness.has_value() {
 396                                     "method"
 397                                 } else {
 398                                     "tymethod"
 399                                 }
 400                             }
 401                         };
 402
 403                         if extra_fragment.is_some() {
 404                             Err(ErrorKind::AnchorFailure(if item.kind == ty::AssocKind::Const {
 405                                 AnchorFailure::AssocConstant
 406                             } else if item.kind == ty::AssocKind::Type {
 407                                 AnchorFailure::AssocType
 408                             } else {
 409                                 AnchorFailure::Method
 410                             }))
 411                         } else {
 412                             let res = Res::Def(item.kind.as_def_kind(), item.def_id);
 413                             Ok((res, Some(format!("{}.{}", kind, item_name))))
 414                         }
 415                     }),
 416                 _ => None,
 417             };
 418             res.unwrap_or_else(|| {
 419                 if ns == Namespace::ValueNS {
 420                     self.variant_field(path_str, current_item, module_id)
 421                 } else {
 422                     Err(ErrorKind::ResolutionFailure)
 423                 }
 424             })
 425         } else {
 426             debug!("attempting to resolve item without parent module: {}", path_str);
 427             Err(ErrorKind::ResolutionFailure)
 428         }
 429     }
 430 }
 431
 432 fn resolve_associated_trait_item(
 433     did: DefId,
 434     module: DefId,
 435     item_name: Symbol,
 436     ns: Namespace,
 437     cx: &DocContext<'_>,
 438 ) -> Option<ty::AssocKind> {
 439     let ty = cx.tcx.type_of(did);
 440     // First consider automatic impls: `impl From<T> for T`
 441     let implicit_impls = crate::clean::get_auto_trait_and_blanket_impls(cx, ty, did);
 442     let mut candidates: Vec<_> = implicit_impls
 443         .flat_map(|impl_outer| {
 444             match impl_outer.inner {
 445                 ImplItem(impl_) => {
 446                     debug!("considering auto or blanket impl for trait {:?}", impl_.trait_);
 447                     // Give precedence to methods that were overridden
 448                     if !impl_.provided_trait_methods.contains(&*item_name.as_str()) {
 449                         let mut items = impl_.items.into_iter().filter_map(|assoc| {
 450                             if assoc.name.as_deref() != Some(&*item_name.as_str()) {
 451                                 return None;
 452                             }
 453                             let kind = assoc
 454                                 .inner
 455                                 .as_assoc_kind()
 456                                 .expect("inner items for a trait should be associated items");
 457                             if kind.namespace() != ns {
 458                                 return None;
 459                             }
 460
 461                             trace!("considering associated item {:?}", assoc.inner);
 462                             // We have a slight issue: normal methods come from `clean` types,
 463                             // but provided methods come directly from `tcx`.
 464                             // Fortunately, we don't need the whole method, we just need to know
 465                             // what kind of associated item it is.
 466                             Some((assoc.def_id, kind))
 467                         });
 468                         let assoc = items.next();
 469                         debug_assert_eq!(items.count(), 0);
 470                         assoc
 471                     } else {
 472                         // These are provided methods or default types:
 473                         // ```
 474                         // trait T {
 475                         //   type A = usize;
 476                         //   fn has_default() -> A { 0 }
 477                         // }
 478                         // ```
 479                         let trait_ = impl_.trait_.unwrap().def_id().unwrap();
 480                         cx.tcx
 481                             .associated_items(trait_)
 482                             .find_by_name_and_namespace(
 483                                 cx.tcx,
 484                                 Ident::with_dummy_span(item_name),
 485                                 ns,
 486                                 trait_,
 487                             )
 488                             .map(|assoc| (assoc.def_id, assoc.kind))
 489                     }
 490                 }
 491                 _ => panic!("get_impls returned something that wasn't an impl"),
 492             }
 493         })
 494         .collect();
 495
 496     // Next consider explicit impls: `impl MyTrait for MyType`
 497     // Give precedence to inherent impls.
 498     if candidates.is_empty() {
 499         let traits = traits_implemented_by(cx, did, module);
 500         debug!("considering traits {:?}", traits);
 501         candidates.extend(traits.iter().filter_map(|&trait_| {
 502             cx.tcx
 503                 .associated_items(trait_)
 504                 .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, trait_)
 505                 .map(|assoc| (assoc.def_id, assoc.kind))
 506         }));
 507     }
 508     // FIXME: warn about ambiguity
 509     debug!("the candidates were {:?}", candidates);
 510     candidates.pop().map(|(_, kind)| kind)
 511 }
 512
 513 /// Given a type, return all traits in scope in `module` implemented by that type.
 514 ///
 515 /// NOTE: this cannot be a query because more traits could be available when more crates are compiled!
 516 /// So it is not stable to serialize cross-crate.
 517 fn traits_implemented_by(cx: &DocContext<'_>, type_: DefId, module: DefId) -> FxHashSet<DefId> {
 518     let mut cache = cx.module_trait_cache.borrow_mut();
 519     let in_scope_traits = cache.entry(module).or_insert_with(|| {
 520         cx.enter_resolver(|resolver| {
 521             resolver.traits_in_scope(module).into_iter().map(|candidate| candidate.def_id).collect()
 522         })
 523     });
 524
 525     let ty = cx.tcx.type_of(type_);
 526     let iter = in_scope_traits.iter().flat_map(|&trait_| {
 527         trace!("considering explicit impl for trait {:?}", trait_);
 528         let mut saw_impl = false;
 529         // Look at each trait implementation to see if it's an impl for `did`
 530         cx.tcx.for_each_relevant_impl(trait_, ty, |impl_| {
 531             // FIXME: this is inefficient, find a way to short-circuit for_each_* so this doesn't take as long
 532             if saw_impl {
 533                 return;
 534             }
 535
 536             let trait_ref = cx.tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
 537             // Check if these are the same type.
 538             let impl_type = trait_ref.self_ty();
 539             debug!(
 540                 "comparing type {} with kind {:?} against type {:?}",
 541                 impl_type,
 542                 impl_type.kind(),
 543                 type_
 544             );
 545             // Fast path: if this is a primitive simple `==` will work
 546             saw_impl = impl_type == ty
 547                 || match impl_type.kind() {
 548                     // Check if these are the same def_id
 549                     ty::Adt(def, _) => {
 550                         debug!("adt def_id: {:?}", def.did);
 551                         def.did == type_
 552                     }
 553                     ty::Foreign(def_id) => *def_id == type_,
 554                     _ => false,
 555                 };
 556         });
 557         if saw_impl { Some(trait_) } else { None }
 558     });
 559     iter.collect()
 560 }
 561
 562 /// Check for resolve collisions between a trait and its derive
 563 ///
 564 /// These are common and we should just resolve to the trait in that case
 565 fn is_derive_trait_collision<T>(ns: &PerNS<Option<(Res, T)>>) -> bool {
 566     if let PerNS {
 567         type_ns: Some((Res::Def(DefKind::Trait, _), _)),
 568         macro_ns: Some((Res::Def(DefKind::Macro(MacroKind::Derive), _), _)),
 569         ..
 570     } = *ns
 571     {
 572         true
 573     } else {
 574         false
 575     }
 576 }
 577
 578 impl<'a, 'tcx> DocFolder for LinkCollector<'a, 'tcx> {
 579     fn fold_item(&mut self, mut item: Item) -> Option<Item> {
 580         use rustc_middle::ty::DefIdTree;
 581
 582         let parent_node = if item.is_fake() {
 583             // FIXME: is this correct?
 584             None
 585         } else {
 586             let mut current = item.def_id;
 587             // The immediate parent might not always be a module.
 588             // Find the first parent which is.
 589             loop {
 590                 if let Some(parent) = self.cx.tcx.parent(current) {
 591                     if self.cx.tcx.def_kind(parent) == DefKind::Mod {
 592                         break Some(parent);
 593                     }
 594                     current = parent;
 595                 } else {
 596                     break None;
 597                 }
 598             }
 599         };
 600
 601         if parent_node.is_some() {
 602             trace!("got parent node for {:?} {:?}, id {:?}", item.type_(), item.name, item.def_id);
 603         }
 604
 605         let current_item = match item.inner {
 606             ModuleItem(..) => {
 607                 if item.attrs.inner_docs {
 608                     if item.def_id.is_top_level_module() { item.name.clone() } else { None }
 609                 } else {
 610                     match parent_node.or(self.mod_ids.last().copied()) {
 611                         Some(parent) if !parent.is_top_level_module() => {
 612                             // FIXME: can we pull the parent module's name from elsewhere?
 613                             Some(self.cx.tcx.item_name(parent).to_string())
 614                         }
 615                         _ => None,
 616                     }
 617                 }
 618             }
 619             ImplItem(Impl { ref for_, .. }) => {
 620                 for_.def_id().map(|did| self.cx.tcx.item_name(did).to_string())
 621             }
 622             // we don't display docs on `extern crate` items anyway, so don't process them.
 623             ExternCrateItem(..) => {
 624                 debug!("ignoring extern crate item {:?}", item.def_id);
 625                 return self.fold_item_recur(item);
 626             }
 627             ImportItem(Import::Simple(ref name, ..)) => Some(name.clone()),
 628             MacroItem(..) => None,
 629             _ => item.name.clone(),
 630         };
 631
 632         if item.is_mod() && item.attrs.inner_docs {
 633             self.mod_ids.push(item.def_id);
 634         }
 635
 636         let cx = self.cx;
 637         let dox = item.attrs.collapsed_doc_value().unwrap_or_else(String::new);
 638         trace!("got documentation '{}'", dox);
 639
 640         // find item's parent to resolve `Self` in item's docs below
 641         let parent_name = self.cx.as_local_hir_id(item.def_id).and_then(|item_hir| {
 642             let parent_hir = self.cx.tcx.hir().get_parent_item(item_hir);
 643             let item_parent = self.cx.tcx.hir().find(parent_hir);
 644             match item_parent {
 645                 Some(hir::Node::Item(hir::Item {
 646                     kind:
 647                         hir::ItemKind::Impl {
 648                             self_ty:
 649                                 hir::Ty {
 650                                     kind:
 651                                         hir::TyKind::Path(hir::QPath::Resolved(
 652                                             _,
 653                                             hir::Path { segments, .. },
 654                                         )),
 655                                     ..
 656                                 },
 657                             ..
 658                         },
 659                     ..
 660                 })) => segments.first().map(|seg| seg.ident.to_string()),
 661                 Some(hir::Node::Item(hir::Item {
 662                     ident, kind: hir::ItemKind::Enum(..), ..
 663                 }))
 664                 | Some(hir::Node::Item(hir::Item {
 665                     ident, kind: hir::ItemKind::Struct(..), ..
 666                 }))
 667                 | Some(hir::Node::Item(hir::Item {
 668                     ident, kind: hir::ItemKind::Union(..), ..
 669                 }))
 670                 | Some(hir::Node::Item(hir::Item {
 671                     ident, kind: hir::ItemKind::Trait(..), ..
 672                 })) => Some(ident.to_string()),
 673                 _ => None,
 674             }
 675         });
 676
 677         for (ori_link, link_range) in markdown_links(&dox) {
 678             trace!("considering link '{}'", ori_link);
 679
 680             // Bail early for real links.
 681             if ori_link.contains('/') {
 682                 continue;
 683             }
 684
 685             // [] is mostly likely not supposed to be a link
 686             if ori_link.is_empty() {
 687                 continue;
 688             }
 689
 690             let link = ori_link.replace("`", "");
 691             let parts = link.split('#').collect::<Vec<_>>();
 692             let (link, extra_fragment) = if parts.len() > 2 {
 693                 anchor_failure(cx, &item, &link, &dox, link_range, AnchorFailure::MultipleAnchors);
 694                 continue;
 695             } else if parts.len() == 2 {
 696                 if parts[0].trim().is_empty() {
 697                     // This is an anchor to an element of the current page, nothing to do in here!
 698                     continue;
 699                 }
 700                 (parts[0].to_owned(), Some(parts[1].to_owned()))
 701             } else {
 702                 (parts[0].to_owned(), None)
 703             };
 704             let resolved_self;
 705             let mut path_str;
 706             let disambiguator;
 707             let (mut res, mut fragment) = {
 708                 path_str = if let Ok((d, path)) = Disambiguator::from_str(&link) {
 709                     disambiguator = Some(d);
 710                     path
 711                 } else {
 712                     disambiguator = None;
 713                     &link
 714                 }
 715                 .trim();
 716
 717                 if path_str.contains(|ch: char| !(ch.is_alphanumeric() || ch == ':' || ch == '_')) {
 718                     continue;
 719                 }
 720
 721                 // In order to correctly resolve intra-doc-links we need to
 722                 // pick a base AST node to work from.  If the documentation for
 723                 // this module came from an inner comment (//!) then we anchor
 724                 // our name resolution *inside* the module.  If, on the other
 725                 // hand it was an outer comment (///) then we anchor the name
 726                 // resolution in the parent module on the basis that the names
 727                 // used are more likely to be intended to be parent names.  For
 728                 // this, we set base_node to None for inner comments since
 729                 // we've already pushed this node onto the resolution stack but
 730                 // for outer comments we explicitly try and resolve against the
 731                 // parent_node first.
 732                 let base_node = if item.is_mod() && item.attrs.inner_docs {
 733                     self.mod_ids.last().copied()
 734                 } else {
 735                     parent_node
 736                 };
 737
 738                 // replace `Self` with suitable item's parent name
 739                 if path_str.starts_with("Self::") {
 740                     if let Some(ref name) = parent_name {
 741                         resolved_self = format!("{}::{}", name, &path_str[6..]);
 742                         path_str = &resolved_self;
 743                     }
 744                 }
 745
 746                 match disambiguator.map(Disambiguator::ns) {
 747                     Some(ns @ (ValueNS | TypeNS)) => {
 748                         match self.resolve(path_str, ns, &current_item, base_node, &extra_fragment)
 749                         {
 750                             Ok(res) => res,
 751                             Err(ErrorKind::ResolutionFailure) => {
 752                                 resolution_failure(cx, &item, path_str, &dox, link_range);
 753                                 // This could just be a normal link or a broken link
 754                                 // we could potentially check if something is
 755                                 // "intra-doc-link-like" and warn in that case.
 756                                 continue;
 757                             }
 758                             Err(ErrorKind::AnchorFailure(msg)) => {
 759                                 anchor_failure(cx, &item, &ori_link, &dox, link_range, msg);
 760                                 continue;
 761                             }
 762                         }
 763                     }
 764                     None => {
 765                         // Try everything!
 766                         let mut candidates = PerNS {
 767                             macro_ns: self
 768                                 .macro_resolve(path_str, base_node)
 769                                 .map(|res| (res, extra_fragment.clone())),
 770                             type_ns: match self.resolve(
 771                                 path_str,
 772                                 TypeNS,
 773                                 &current_item,
 774                                 base_node,
 775                                 &extra_fragment,
 776                             ) {
 777                                 Ok(res) => {
 778                                     debug!("got res in TypeNS: {:?}", res);
 779                                     Some(res)
 780                                 }
 781                                 Err(ErrorKind::AnchorFailure(msg)) => {
 782                                     anchor_failure(cx, &item, &ori_link, &dox, link_range, msg);
 783                                     continue;
 784                                 }
 785                                 Err(ErrorKind::ResolutionFailure) => None,
 786                             },
 787                             value_ns: match self.resolve(
 788                                 path_str,
 789                                 ValueNS,
 790                                 &current_item,
 791                                 base_node,
 792                                 &extra_fragment,
 793                             ) {
 794                                 Ok(res) => Some(res),
 795                                 Err(ErrorKind::AnchorFailure(msg)) => {
 796                                     anchor_failure(cx, &item, &ori_link, &dox, link_range, msg);
 797                                     continue;
 798                                 }
 799                                 Err(ErrorKind::ResolutionFailure) => None,
 800                             }
 801                             .and_then(|(res, fragment)| {
 802                                 // Constructors are picked up in the type namespace.
 803                                 match res {
 804                                     Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) => None,
 805                                     _ => match (fragment, extra_fragment) {
 806                                         (Some(fragment), Some(_)) => {
 807                                             // Shouldn't happen but who knows?
 808                                             Some((res, Some(fragment)))
 809                                         }
 810                                         (fragment, None) | (None, fragment) => {
 811                                             Some((res, fragment))
 812                                         }
 813                                     },
 814                                 }
 815                             }),
 816                         };
 817
 818                         if candidates.is_empty() {
 819                             resolution_failure(cx, &item, path_str, &dox, link_range);
 820                             // this could just be a normal link
 821                             continue;
 822                         }
 823
 824                         let len = candidates.clone().present_items().count();
 825
 826                         if len == 1 {
 827                             candidates.present_items().next().unwrap()
 828                         } else if len == 2 && is_derive_trait_collision(&candidates) {
 829                             candidates.type_ns.unwrap()
 830                         } else {
 831                             if is_derive_trait_collision(&candidates) {
 832                                 candidates.macro_ns = None;
 833                             }
 834                             let candidates =
 835                                 candidates.map(|candidate| candidate.map(|(res, _)| res));
 836                             ambiguity_error(
 837                                 cx,
 838                                 &item,
 839                                 path_str,
 840                                 &dox,
 841                                 link_range,
 842                                 candidates.present_items().collect(),
 843                             );
 844                             continue;
 845                         }
 846                     }
 847                     Some(MacroNS) => {
 848                         if let Some(res) = self.macro_resolve(path_str, base_node) {
 849                             (res, extra_fragment)
 850                         } else {
 851                             resolution_failure(cx, &item, path_str, &dox, link_range);
 852                             continue;
 853                         }
 854                     }
 855                 }
 856             };
 857
 858             // Check for a primitive which might conflict with a module
 859             // Report the ambiguity and require that the user specify which one they meant.
 860             // FIXME: could there ever be a primitive not in the type namespace?
 861             if matches!(
 862                 disambiguator,
 863                 None | Some(Disambiguator::Namespace(Namespace::TypeNS) | Disambiguator::Primitive)
 864             ) && !matches!(res, Res::PrimTy(_))
 865             {
 866                 if let Some((path, prim)) = is_primitive(path_str, TypeNS) {
 867                     // `prim@char`
 868                     if matches!(disambiguator, Some(Disambiguator::Primitive)) {
 869                         if fragment.is_some() {
 870                             anchor_failure(
 871                                 cx,
 872                                 &item,
 873                                 path_str,
 874                                 &dox,
 875                                 link_range,
 876                                 AnchorFailure::Primitive,
 877                             );
 878                             continue;
 879                         }
 880                         res = prim;
 881                         fragment = Some(path.to_owned());
 882                     } else {
 883                         // `[char]` when a `char` module is in scope
 884                         let candidates = vec![res, prim];
 885                         ambiguity_error(cx, &item, path_str, &dox, link_range, candidates);
 886                         continue;
 887                     }
 888                 }
 889             }
 890
 891             let report_mismatch = |specified: Disambiguator, resolved: Disambiguator| {
 892                 // The resolved item did not match the disambiguator; give a better error than 'not found'
 893                 let msg = format!("incompatible link kind for `{}`", path_str);
 894                 report_diagnostic(cx, &msg, &item, &dox, link_range.clone(), |diag, sp| {
 895                     let note = format!(
 896                         "this link resolved to {} {}, which is not {} {}",
 897                         resolved.article(),
 898                         resolved.descr(),
 899                         specified.article(),
 900                         specified.descr()
 901                     );
 902                     diag.note(&note);
 903                     suggest_disambiguator(resolved, diag, path_str, &dox, sp, &link_range);
 904                 });
 905             };
 906             if let Res::PrimTy(_) = res {
 907                 match disambiguator {
 908                     Some(Disambiguator::Primitive | Disambiguator::Namespace(_)) | None => {
 909                         item.attrs.links.push((ori_link, None, fragment))
 910                     }
 911                     Some(other) => {
 912                         report_mismatch(other, Disambiguator::Primitive);
 913                         continue;
 914                     }
 915                 }
 916             } else {
 917                 debug!("intra-doc link to {} resolved to {:?}", path_str, res);
 918
 919                 // Disallow e.g. linking to enums with `struct@`
 920                 if let Res::Def(kind, _) = res {
 921                     debug!("saw kind {:?} with disambiguator {:?}", kind, disambiguator);
 922                     match (self.kind_side_channel.take().unwrap_or(kind), disambiguator) {
 923                         | (DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst, Some(Disambiguator::Kind(DefKind::Const)))
 924                         // NOTE: this allows 'method' to mean both normal functions and associated functions
 925                         // This can't cause ambiguity because both are in the same namespace.
 926                         | (DefKind::Fn | DefKind::AssocFn, Some(Disambiguator::Kind(DefKind::Fn)))
 927                         // These are namespaces; allow anything in the namespace to match
 928                         | (_, Some(Disambiguator::Namespace(_)))
 929                         // If no disambiguator given, allow anything
 930                         | (_, None)
 931                         // All of these are valid, so do nothing
 932                         => {}
 933                         (actual, Some(Disambiguator::Kind(expected))) if actual == expected => {}
 934                         (_, Some(specified @ Disambiguator::Kind(_) | specified @ Disambiguator::Primitive)) => {
 935                             report_mismatch(specified, Disambiguator::Kind(kind));
 936                             continue;
 937                         }
 938                     }
 939                 }
 940
 941                 // item can be non-local e.g. when using #[doc(primitive = "pointer")]
 942                 if let Some((src_id, dst_id)) = res
 943                     .opt_def_id()
 944                     .and_then(|def_id| def_id.as_local())
 945                     .and_then(|dst_id| item.def_id.as_local().map(|src_id| (src_id, dst_id)))
 946                 {
 947                     use rustc_hir::def_id::LOCAL_CRATE;
 948
 949                     let hir_src = self.cx.tcx.hir().local_def_id_to_hir_id(src_id);
 950                     let hir_dst = self.cx.tcx.hir().local_def_id_to_hir_id(dst_id);
 951
 952                     if self.cx.tcx.privacy_access_levels(LOCAL_CRATE).is_exported(hir_src)
 953                         && !self.cx.tcx.privacy_access_levels(LOCAL_CRATE).is_exported(hir_dst)
 954                     {
 955                         privacy_error(cx, &item, &path_str, &dox, link_range);
 956                         continue;
 957                     }
 958                 }
 959                 let id = register_res(cx, res);
 960                 item.attrs.links.push((ori_link, Some(id), fragment));
 961             }
 962         }
 963
 964         if item.is_mod() && !item.attrs.inner_docs {
 965             self.mod_ids.push(item.def_id);
 966         }
 967
 968         if item.is_mod() {
 969             let ret = self.fold_item_recur(item);
 970
 971             self.mod_ids.pop();
 972
 973             ret
 974         } else {
 975             self.fold_item_recur(item)
 976         }
 977     }
 978 }
 979
 980 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 981 enum Disambiguator {
 982     Primitive,
 983     Kind(DefKind),
 984     Namespace(Namespace),
 985 }
 986
 987 impl Disambiguator {
 988     /// (disambiguator, path_str)
 989     fn from_str(link: &str) -> Result<(Self, &str), ()> {
 990         use Disambiguator::{Kind, Namespace as NS, Primitive};
 991
 992         let find_suffix = || {
 993             let suffixes = [
 994                 ("!()", DefKind::Macro(MacroKind::Bang)),
 995                 ("()", DefKind::Fn),
 996                 ("!", DefKind::Macro(MacroKind::Bang)),
 997             ];
 998             for &(suffix, kind) in &suffixes {
 999                 if link.ends_with(suffix) {
1000                     return Ok((Kind(kind), link.trim_end_matches(suffix)));
1001                 }
1002             }
1003             Err(())
1004         };
1005
1006         if let Some(idx) = link.find('@') {
1007             let (prefix, rest) = link.split_at(idx);
1008             let d = match prefix {
1009                 "struct" => Kind(DefKind::Struct),
1010                 "enum" => Kind(DefKind::Enum),
1011                 "trait" => Kind(DefKind::Trait),
1012                 "union" => Kind(DefKind::Union),
1013                 "module" | "mod" => Kind(DefKind::Mod),
1014                 "const" | "constant" => Kind(DefKind::Const),
1015                 "static" => Kind(DefKind::Static),
1016                 "function" | "fn" | "method" => Kind(DefKind::Fn),
1017                 "derive" => Kind(DefKind::Macro(MacroKind::Derive)),
1018                 "type" => NS(Namespace::TypeNS),
1019                 "value" => NS(Namespace::ValueNS),
1020                 "macro" => NS(Namespace::MacroNS),
1021                 "prim" | "primitive" => Primitive,
1022                 _ => return find_suffix(),
1023             };
1024             Ok((d, &rest[1..]))
1025         } else {
1026             find_suffix()
1027         }
1028     }
1029
1030     /// WARNING: panics on `Res::Err`
1031     fn from_res(res: Res) -> Self {
1032         match res {
1033             Res::Def(kind, _) => Disambiguator::Kind(kind),
1034             Res::PrimTy(_) => Disambiguator::Primitive,
1035             _ => Disambiguator::Namespace(res.ns().expect("can't call `from_res` on Res::err")),
1036         }
1037     }
1038
1039     /// Return (description of the change, suggestion)
1040     fn display_for(self, path_str: &str) -> (&'static str, String) {
1041         const PREFIX: &str = "prefix with the item kind";
1042         const FUNCTION: &str = "add parentheses";
1043         const MACRO: &str = "add an exclamation mark";
1044
1045         let kind = match self {
1046             Disambiguator::Primitive => return (PREFIX, format!("prim@{}", path_str)),
1047             Disambiguator::Kind(kind) => kind,
1048             Disambiguator::Namespace(_) => panic!("display_for cannot be used on namespaces"),
1049         };
1050         if kind == DefKind::Macro(MacroKind::Bang) {
1051             return (MACRO, format!("{}!", path_str));
1052         } else if kind == DefKind::Fn || kind == DefKind::AssocFn {
1053             return (FUNCTION, format!("{}()", path_str));
1054         }
1055
1056         let prefix = match kind {
1057             DefKind::Struct => "struct",
1058             DefKind::Enum => "enum",
1059             DefKind::Trait => "trait",
1060             DefKind::Union => "union",
1061             DefKind::Mod => "mod",
1062             DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst => {
1063                 "const"
1064             }
1065             DefKind::Static => "static",
1066             DefKind::Macro(MacroKind::Derive) => "derive",
1067             // Now handle things that don't have a specific disambiguator
1068             _ => match kind
1069                 .ns()
1070                 .expect("tried to calculate a disambiguator for a def without a namespace?")
1071             {
1072                 Namespace::TypeNS => "type",
1073                 Namespace::ValueNS => "value",
1074                 Namespace::MacroNS => "macro",
1075             },
1076         };
1077
1078         // FIXME: if this is an implied shortcut link, it's bad style to suggest `@`
1079         (PREFIX, format!("{}@{}", prefix, path_str))
1080     }
1081
1082     fn ns(self) -> Namespace {
1083         match self {
1084             Self::Namespace(n) => n,
1085             Self::Kind(k) => {
1086                 k.ns().expect("only DefKinds with a valid namespace can be disambiguators")
1087             }
1088             Self::Primitive => TypeNS,
1089         }
1090     }
1091
1092     fn article(self) -> &'static str {
1093         match self {
1094             Self::Namespace(_) => panic!("article() doesn't make sense for namespaces"),
1095             Self::Kind(k) => k.article(),
1096             Self::Primitive => "a",
1097         }
1098     }
1099
1100     fn descr(self) -> &'static str {
1101         match self {
1102             Self::Namespace(n) => n.descr(),
1103             // HACK(jynelson): by looking at the source I saw the DefId we pass
1104             // for `expected.descr()` doesn't matter, since it's not a crate
1105             Self::Kind(k) => k.descr(DefId::local(hir::def_id::DefIndex::from_usize(0))),
1106             Self::Primitive => "builtin type",
1107         }
1108     }
1109 }
1110
1111 /// Reports a diagnostic for an intra-doc link.
1112 ///
1113 /// If no link range is provided, or the source span of the link cannot be determined, the span of
1114 /// the entire documentation block is used for the lint. If a range is provided but the span
1115 /// calculation fails, a note is added to the diagnostic pointing to the link in the markdown.
1116 ///
1117 /// The `decorate` callback is invoked in all cases to allow further customization of the
1118 /// diagnostic before emission. If the span of the link was able to be determined, the second
1119 /// parameter of the callback will contain it, and the primary span of the diagnostic will be set
1120 /// to it.
1121 fn report_diagnostic(
1122     cx: &DocContext<'_>,
1123     msg: &str,
1124     item: &Item,
1125     dox: &str,
1126     link_range: Option<Range<usize>>,
1127     decorate: impl FnOnce(&mut DiagnosticBuilder<'_>, Option<rustc_span::Span>),
1128 ) {
1129     let hir_id = match cx.as_local_hir_id(item.def_id) {
1130         Some(hir_id) => hir_id,
1131         None => {
1132             // If non-local, no need to check anything.
1133             info!("ignoring warning from parent crate: {}", msg);
1134             return;
1135         }
1136     };
1137
1138     let attrs = &item.attrs;
1139     let sp = span_of_attrs(attrs).unwrap_or(item.source.span());
1140
1141     cx.tcx.struct_span_lint_hir(lint::builtin::BROKEN_INTRA_DOC_LINKS, hir_id, sp, |lint| {
1142         let mut diag = lint.build(msg);
1143
1144         let span = link_range
1145             .as_ref()
1146             .and_then(|range| super::source_span_for_markdown_range(cx, dox, range, attrs));
1147
1148         if let Some(link_range) = link_range {
1149             if let Some(sp) = span {
1150                 diag.set_span(sp);
1151             } else {
1152                 // blah blah blah\nblah\nblah [blah] blah blah\nblah blah
1153                 //                       ^     ~~~~
1154                 //                       |     link_range
1155                 //                       last_new_line_offset
1156                 let last_new_line_offset = dox[..link_range.start].rfind('\n').map_or(0, |n| n + 1);
1157                 let line = dox[last_new_line_offset..].lines().next().unwrap_or("");
1158
1159                 // Print the line containing the `link_range` and manually mark it with '^'s.
1160                 diag.note(&format!(
1161                     "the link appears in this line:\n\n{line}\n\
1162                      {indicator: <before$}{indicator:^<found$}",
1163                     line = line,
1164                     indicator = "",
1165                     before = link_range.start - last_new_line_offset,
1166                     found = link_range.len(),
1167                 ));
1168             }
1169         }
1170
1171         decorate(&mut diag, span);
1172
1173         diag.emit();
1174     });
1175 }
1176
1177 fn resolution_failure(
1178     cx: &DocContext<'_>,
1179     item: &Item,
1180     path_str: &str,
1181     dox: &str,
1182     link_range: Option<Range<usize>>,
1183 ) {
1184     report_diagnostic(
1185         cx,
1186         &format!("unresolved link to `{}`", path_str),
1187         item,
1188         dox,
1189         link_range,
1190         |diag, sp| {
1191             if let Some(sp) = sp {
1192                 diag.span_label(sp, "unresolved link");
1193             }
1194
1195             diag.help(r#"to escape `[` and `]` characters, add '\' before them like `\[` or `\]`"#);
1196         },
1197     );
1198 }
1199
1200 fn anchor_failure(
1201     cx: &DocContext<'_>,
1202     item: &Item,
1203     path_str: &str,
1204     dox: &str,
1205     link_range: Option<Range<usize>>,
1206     failure: AnchorFailure,
1207 ) {
1208     let msg = match failure {
1209         AnchorFailure::MultipleAnchors => format!("`{}` contains multiple anchors", path_str),
1210         AnchorFailure::Primitive
1211         | AnchorFailure::Variant
1212         | AnchorFailure::AssocConstant
1213         | AnchorFailure::AssocType
1214         | AnchorFailure::Field
1215         | AnchorFailure::Method => {
1216             let kind = match failure {
1217                 AnchorFailure::Primitive => "primitive type",
1218                 AnchorFailure::Variant => "enum variant",
1219                 AnchorFailure::AssocConstant => "associated constant",
1220                 AnchorFailure::AssocType => "associated type",
1221                 AnchorFailure::Field => "struct field",
1222                 AnchorFailure::Method => "method",
1223                 AnchorFailure::MultipleAnchors => unreachable!("should be handled already"),
1224             };
1225
1226             format!(
1227                 "`{}` contains an anchor, but links to {kind}s are already anchored",
1228                 path_str,
1229                 kind = kind
1230             )
1231         }
1232     };
1233
1234     report_diagnostic(cx, &msg, item, dox, link_range, |diag, sp| {
1235         if let Some(sp) = sp {
1236             diag.span_label(sp, "contains invalid anchor");
1237         }
1238     });
1239 }
1240
1241 fn ambiguity_error(
1242     cx: &DocContext<'_>,
1243     item: &Item,
1244     path_str: &str,
1245     dox: &str,
1246     link_range: Option<Range<usize>>,
1247     candidates: Vec<Res>,
1248 ) {
1249     let mut msg = format!("`{}` is ", path_str);
1250
1251     match candidates.as_slice() {
1252         [first_def, second_def] => {
1253             msg += &format!(
1254                 "both {} {} and {} {}",
1255                 first_def.article(),
1256                 first_def.descr(),
1257                 second_def.article(),
1258                 second_def.descr(),
1259             );
1260         }
1261         _ => {
1262             let mut candidates = candidates.iter().peekable();
1263             while let Some(res) = candidates.next() {
1264                 if candidates.peek().is_some() {
1265                     msg += &format!("{} {}, ", res.article(), res.descr());
1266                 } else {
1267                     msg += &format!("and {} {}", res.article(), res.descr());
1268                 }
1269             }
1270         }
1271     }
1272
1273     report_diagnostic(cx, &msg, item, dox, link_range.clone(), |diag, sp| {
1274         if let Some(sp) = sp {
1275             diag.span_label(sp, "ambiguous link");
1276         } else {
1277             diag.note("ambiguous link");
1278         }
1279
1280         for res in candidates {
1281             let disambiguator = Disambiguator::from_res(res);
1282             suggest_disambiguator(disambiguator, diag, path_str, dox, sp, &link_range);
1283         }
1284     });
1285 }
1286
1287 fn suggest_disambiguator(
1288     disambiguator: Disambiguator,
1289     diag: &mut DiagnosticBuilder<'_>,
1290     path_str: &str,
1291     dox: &str,
1292     sp: Option<rustc_span::Span>,
1293     link_range: &Option<Range<usize>>,
1294 ) {
1295     let (action, mut suggestion) = disambiguator.display_for(path_str);
1296     let help = format!("to link to the {}, {}", disambiguator.descr(), action);
1297
1298     if let Some(sp) = sp {
1299         let link_range = link_range.as_ref().expect("must have a link range if we have a span");
1300         if dox.bytes().nth(link_range.start) == Some(b'`') {
1301             suggestion = format!("`{}`", suggestion);
1302         }
1303
1304         diag.span_suggestion(sp, &help, suggestion, Applicability::MaybeIncorrect);
1305     } else {
1306         diag.help(&format!("{}: {}", help, suggestion));
1307     }
1308 }
1309
1310 fn privacy_error(
1311     cx: &DocContext<'_>,
1312     item: &Item,
1313     path_str: &str,
1314     dox: &str,
1315     link_range: Option<Range<usize>>,
1316 ) {
1317     let item_name = item.name.as_deref().unwrap_or("<unknown>");
1318     let msg =
1319         format!("public documentation for `{}` links to private item `{}`", item_name, path_str);
1320
1321     report_diagnostic(cx, &msg, item, dox, link_range, |diag, sp| {
1322         if let Some(sp) = sp {
1323             diag.span_label(sp, "this item is private");
1324         }
1325
1326         let note_msg = if cx.render_options.document_private {
1327             "this link resolves only because you passed `--document-private-items`, but will break without"
1328         } else {
1329             "this link will resolve properly if you pass `--document-private-items`"
1330         };
1331         diag.note(note_msg);
1332     });
1333 }
1334
1335 /// Given an enum variant's res, return the res of its enum and the associated fragment.
1336 fn handle_variant(
1337     cx: &DocContext<'_>,
1338     res: Res,
1339     extra_fragment: &Option<String>,
1340 ) -> Result<(Res, Option<String>), ErrorKind> {
1341     use rustc_middle::ty::DefIdTree;
1342
1343     if extra_fragment.is_some() {
1344         return Err(ErrorKind::AnchorFailure(AnchorFailure::Variant));
1345     }
1346     let parent = if let Some(parent) = cx.tcx.parent(res.def_id()) {
1347         parent
1348     } else {
1349         return Err(ErrorKind::ResolutionFailure);
1350     };
1351     let parent_def = Res::Def(DefKind::Enum, parent);
1352     let variant = cx.tcx.expect_variant_res(res);
1353     Ok((parent_def, Some(format!("variant.{}", variant.ident.name))))
1354 }
1355
1356 const PRIMITIVES: &[(&str, Res)] = &[
1357     ("u8", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U8))),
1358     ("u16", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U16))),
1359     ("u32", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U32))),
1360     ("u64", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U64))),
1361     ("u128", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U128))),
1362     ("usize", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::Usize))),
1363     ("i8", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I8))),
1364     ("i16", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I16))),
1365     ("i32", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I32))),
1366     ("i64", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I64))),
1367     ("i128", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I128))),
1368     ("isize", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::Isize))),
1369     ("f32", Res::PrimTy(hir::PrimTy::Float(rustc_ast::FloatTy::F32))),
1370     ("f64", Res::PrimTy(hir::PrimTy::Float(rustc_ast::FloatTy::F64))),
1371     ("str", Res::PrimTy(hir::PrimTy::Str)),
1372     ("bool", Res::PrimTy(hir::PrimTy::Bool)),
1373     ("true", Res::PrimTy(hir::PrimTy::Bool)),
1374     ("false", Res::PrimTy(hir::PrimTy::Bool)),
1375     ("char", Res::PrimTy(hir::PrimTy::Char)),
1376 ];
1377
1378 fn is_primitive(path_str: &str, ns: Namespace) -> Option<(&'static str, Res)> {
1379     if ns == TypeNS {
1380         PRIMITIVES
1381             .iter()
1382             .filter(|x| x.0 == path_str)
1383             .copied()
1384             .map(|x| if x.0 == "true" || x.0 == "false" { ("bool", x.1) } else { x })
1385             .next()
1386     } else {
1387         None
1388     }
1389 }
1390
1391 fn primitive_impl(cx: &DocContext<'_>, path_str: &str) -> Option<&'static SmallVec<[DefId; 4]>> {
1392     Some(PrimitiveType::from_symbol(Symbol::intern(path_str))?.impls(cx.tcx))
1393 }