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                 if let Ok((_, res)) =
 165                     resolver.resolve_str_path_error(DUMMY_SP, path_str, MacroNS, module_id)
 166                 {
 167                     // don't resolve builtins like `#[derive]`
 168                     if let Res::Def(..) = res {
 169                         let res = res.map_id(|_| panic!("unexpected node_id"));
 170                         return Some(res);
 171                     }
 172                 }
 173             } else {
 174                 debug!("attempting to resolve item without parent module: {}", path_str);
 175             }
 176             None
 177         })
 178     }
 179     /// Resolves a string as a path within a particular namespace. Also returns an optional
 180     /// URL fragment in the case of variants and methods.
 181     fn resolve(
 182         &self,
 183         path_str: &str,
 184         ns: Namespace,
 185         current_item: &Option<String>,
 186         parent_id: Option<DefId>,
 187         extra_fragment: &Option<String>,
 188     ) -> Result<(Res, Option<String>), ErrorKind> {
 189         let cx = self.cx;
 190
 191         // In case we're in a module, try to resolve the relative path.
 192         if let Some(module_id) = parent_id {
 193             let result = cx.enter_resolver(|resolver| {
 194                 resolver.resolve_str_path_error(DUMMY_SP, &path_str, ns, module_id)
 195             });
 196             debug!("{} resolved to {:?} in namespace {:?}", path_str, result, ns);
 197             let result = match result {
 198                 Ok((_, Res::Err)) => Err(ErrorKind::ResolutionFailure),
 199                 _ => result.map_err(|_| ErrorKind::ResolutionFailure),
 200             };
 201
 202             if let Ok((_, res)) = result {
 203                 let res = res.map_id(|_| panic!("unexpected node_id"));
 204                 // In case this is a trait item, skip the
 205                 // early return and try looking for the trait.
 206                 let value = match res {
 207                     Res::Def(DefKind::AssocFn | DefKind::AssocConst, _) => true,
 208                     Res::Def(DefKind::AssocTy, _) => false,
 209                     Res::Def(DefKind::Variant, _) => {
 210                         return handle_variant(cx, res, extra_fragment);
 211                     }
 212                     // Not a trait item; just return what we found.
 213                     Res::PrimTy(..) => {
 214                         if extra_fragment.is_some() {
 215                             return Err(ErrorKind::AnchorFailure(AnchorFailure::Primitive));
 216                         }
 217                         return Ok((res, Some(path_str.to_owned())));
 218                     }
 219                     Res::Def(DefKind::Mod, _) => {
 220                         return Ok((res, extra_fragment.clone()));
 221                     }
 222                     _ => {
 223                         return Ok((res, extra_fragment.clone()));
 224                     }
 225                 };
 226
 227                 if value != (ns == ValueNS) {
 228                     return Err(ErrorKind::ResolutionFailure);
 229                 }
 230             } else if let Some((path, prim)) = is_primitive(path_str, ns) {
 231                 if extra_fragment.is_some() {
 232                     return Err(ErrorKind::AnchorFailure(AnchorFailure::Primitive));
 233                 }
 234                 return Ok((prim, Some(path.to_owned())));
 235             }
 236
 237             // Try looking for methods and associated items.
 238             let mut split = path_str.rsplitn(2, "::");
 239             let item_name =
 240                 split.next().map(|f| Symbol::intern(f)).ok_or(ErrorKind::ResolutionFailure)?;
 241             let path = split
 242                 .next()
 243                 .map(|f| {
 244                     if f == "self" || f == "Self" {
 245                         if let Some(name) = current_item.as_ref() {
 246                             return name.clone();
 247                         }
 248                     }
 249                     f.to_owned()
 250                 })
 251                 .ok_or(ErrorKind::ResolutionFailure)?;
 252
 253             if let Some((path, prim)) = is_primitive(&path, TypeNS) {
 254                 for &impl_ in primitive_impl(cx, &path).ok_or(ErrorKind::ResolutionFailure)? {
 255                     let link = cx
 256                         .tcx
 257                         .associated_items(impl_)
 258                         .find_by_name_and_namespace(
 259                             cx.tcx,
 260                             Ident::with_dummy_span(item_name),
 261                             ns,
 262                             impl_,
 263                         )
 264                         .and_then(|item| match item.kind {
 265                             ty::AssocKind::Fn => Some("method"),
 266                             _ => None,
 267                         })
 268                         .map(|out| (prim, Some(format!("{}#{}.{}", path, out, item_name))));
 269                     if let Some(link) = link {
 270                         return Ok(link);
 271                     }
 272                 }
 273                 return Err(ErrorKind::ResolutionFailure);
 274             }
 275
 276             let (_, ty_res) = cx
 277                 .enter_resolver(|resolver| {
 278                     resolver.resolve_str_path_error(DUMMY_SP, &path, TypeNS, module_id)
 279                 })
 280                 .map_err(|_| ErrorKind::ResolutionFailure)?;
 281             if let Res::Err = ty_res {
 282                 return if ns == Namespace::ValueNS {
 283                     self.variant_field(path_str, current_item, module_id)
 284                 } else {
 285                     Err(ErrorKind::ResolutionFailure)
 286                 };
 287             }
 288             let ty_res = ty_res.map_id(|_| panic!("unexpected node_id"));
 289             let res = match ty_res {
 290                 Res::Def(
 291                     DefKind::Struct | DefKind::Union | DefKind::Enum | DefKind::TyAlias,
 292                     did,
 293                 ) => {
 294                     debug!("looking for associated item named {} for item {:?}", item_name, did);
 295                     // Checks if item_name belongs to `impl SomeItem`
 296                     let kind = cx
 297                         .tcx
 298                         .inherent_impls(did)
 299                         .iter()
 300                         .flat_map(|&imp| {
 301                             cx.tcx.associated_items(imp).find_by_name_and_namespace(
 302                                 cx.tcx,
 303                                 Ident::with_dummy_span(item_name),
 304                                 ns,
 305                                 imp,
 306                             )
 307                         })
 308                         .map(|item| item.kind)
 309                         // There should only ever be one associated item that matches from any inherent impl
 310                         .next()
 311                         // Check if item_name belongs to `impl SomeTrait for SomeItem`
 312                         // This gives precedence to `impl SomeItem`:
 313                         // Although having both would be ambiguous, use impl version for compat. sake.
 314                         // To handle that properly resolve() would have to support
 315                         // something like [`ambi_fn`](<SomeStruct as SomeTrait>::ambi_fn)
 316                         .or_else(|| {
 317                             let kind = resolve_associated_trait_item(
 318                                 did, module_id, item_name, ns, &self.cx,
 319                             );
 320                             debug!("got associated item kind {:?}", kind);
 321                             kind
 322                         });
 323
 324                     if let Some(kind) = kind {
 325                         let out = match kind {
 326                             ty::AssocKind::Fn => "method",
 327                             ty::AssocKind::Const => "associatedconstant",
 328                             ty::AssocKind::Type => "associatedtype",
 329                         };
 330                         Some(if extra_fragment.is_some() {
 331                             Err(ErrorKind::AnchorFailure(if kind == ty::AssocKind::Fn {
 332                                 AnchorFailure::Method
 333                             } else {
 334                                 AnchorFailure::AssocConstant
 335                             }))
 336                         } else {
 337                             // HACK(jynelson): `clean` expects the type, not the associated item.
 338                             // but the disambiguator logic expects the associated item.
 339                             // Store the kind in a side channel so that only the disambiguator logic looks at it.
 340                             self.kind_side_channel.set(Some(kind.as_def_kind()));
 341                             Ok((ty_res, Some(format!("{}.{}", out, item_name))))
 342                         })
 343                     } else if ns == Namespace::ValueNS {
 344                         match cx.tcx.type_of(did).kind {
 345                             ty::Adt(def, _) => {
 346                                 let field = if def.is_enum() {
 347                                     def.all_fields().find(|item| item.ident.name == item_name)
 348                                 } else {
 349                                     def.non_enum_variant()
 350                                         .fields
 351                                         .iter()
 352                                         .find(|item| item.ident.name == item_name)
 353                                 };
 354                                 field.map(|item| {
 355                                     if extra_fragment.is_some() {
 356                                         Err(ErrorKind::AnchorFailure(if def.is_enum() {
 357                                             AnchorFailure::Variant
 358                                         } else {
 359                                             AnchorFailure::Field
 360                                         }))
 361                                     } else {
 362                                         Ok((
 363                                             ty_res,
 364                                             Some(format!(
 365                                                 "{}.{}",
 366                                                 if def.is_enum() {
 367                                                     "variant"
 368                                                 } else {
 369                                                     "structfield"
 370                                                 },
 371                                                 item.ident
 372                                             )),
 373                                         ))
 374                                     }
 375                                 })
 376                             }
 377                             _ => None,
 378                         }
 379                     } else {
 380                         // We already know this isn't in ValueNS, so no need to check variant_field
 381                         return Err(ErrorKind::ResolutionFailure);
 382                     }
 383                 }
 384                 Res::Def(DefKind::Trait, did) => cx
 385                     .tcx
 386                     .associated_items(did)
 387                     .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, did)
 388                     .map(|item| {
 389                         let kind = match item.kind {
 390                             ty::AssocKind::Const => "associatedconstant",
 391                             ty::AssocKind::Type => "associatedtype",
 392                             ty::AssocKind::Fn => {
 393                                 if item.defaultness.has_value() {
 394                                     "method"
 395                                 } else {
 396                                     "tymethod"
 397                                 }
 398                             }
 399                         };
 400
 401                         if extra_fragment.is_some() {
 402                             Err(ErrorKind::AnchorFailure(if item.kind == ty::AssocKind::Const {
 403                                 AnchorFailure::AssocConstant
 404                             } else if item.kind == ty::AssocKind::Type {
 405                                 AnchorFailure::AssocType
 406                             } else {
 407                                 AnchorFailure::Method
 408                             }))
 409                         } else {
 410                             let res = Res::Def(item.kind.as_def_kind(), item.def_id);
 411                             Ok((res, Some(format!("{}.{}", kind, item_name))))
 412                         }
 413                     }),
 414                 _ => None,
 415             };
 416             res.unwrap_or_else(|| {
 417                 if ns == Namespace::ValueNS {
 418                     self.variant_field(path_str, current_item, module_id)
 419                 } else {
 420                     Err(ErrorKind::ResolutionFailure)
 421                 }
 422             })
 423         } else {
 424             debug!("attempting to resolve item without parent module: {}", path_str);
 425             Err(ErrorKind::ResolutionFailure)
 426         }
 427     }
 428 }
 429
 430 fn resolve_associated_trait_item(
 431     did: DefId,
 432     module: DefId,
 433     item_name: Symbol,
 434     ns: Namespace,
 435     cx: &DocContext<'_>,
 436 ) -> Option<ty::AssocKind> {
 437     let ty = cx.tcx.type_of(did);
 438     // First consider automatic impls: `impl From<T> for T`
 439     let implicit_impls = crate::clean::get_auto_trait_and_blanket_impls(cx, ty, did);
 440     let mut candidates: Vec<_> = implicit_impls
 441         .flat_map(|impl_outer| {
 442             match impl_outer.inner {
 443                 ImplItem(impl_) => {
 444                     debug!("considering auto or blanket impl for trait {:?}", impl_.trait_);
 445                     // Give precedence to methods that were overridden
 446                     if !impl_.provided_trait_methods.contains(&*item_name.as_str()) {
 447                         let mut items = impl_.items.into_iter().filter_map(|assoc| {
 448                             if assoc.name.as_deref() != Some(&*item_name.as_str()) {
 449                                 return None;
 450                             }
 451                             let kind = assoc
 452                                 .inner
 453                                 .as_assoc_kind()
 454                                 .expect("inner items for a trait should be associated items");
 455                             if kind.namespace() != ns {
 456                                 return None;
 457                             }
 458
 459                             trace!("considering associated item {:?}", assoc.inner);
 460                             // We have a slight issue: normal methods come from `clean` types,
 461                             // but provided methods come directly from `tcx`.
 462                             // Fortunately, we don't need the whole method, we just need to know
 463                             // what kind of associated item it is.
 464                             Some((assoc.def_id, kind))
 465                         });
 466                         let assoc = items.next();
 467                         debug_assert_eq!(items.count(), 0);
 468                         assoc
 469                     } else {
 470                         // These are provided methods or default types:
 471                         // ```
 472                         // trait T {
 473                         //   type A = usize;
 474                         //   fn has_default() -> A { 0 }
 475                         // }
 476                         // ```
 477                         let trait_ = impl_.trait_.unwrap().def_id().unwrap();
 478                         cx.tcx
 479                             .associated_items(trait_)
 480                             .find_by_name_and_namespace(
 481                                 cx.tcx,
 482                                 Ident::with_dummy_span(item_name),
 483                                 ns,
 484                                 trait_,
 485                             )
 486                             .map(|assoc| (assoc.def_id, assoc.kind))
 487                     }
 488                 }
 489                 _ => panic!("get_impls returned something that wasn't an impl"),
 490             }
 491         })
 492         .collect();
 493
 494     // Next consider explicit impls: `impl MyTrait for MyType`
 495     // Give precedence to inherent impls.
 496     if candidates.is_empty() {
 497         let traits = traits_implemented_by(cx, did, module);
 498         debug!("considering traits {:?}", traits);
 499         candidates.extend(traits.iter().filter_map(|&trait_| {
 500             cx.tcx
 501                 .associated_items(trait_)
 502                 .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, trait_)
 503                 .map(|assoc| (assoc.def_id, assoc.kind))
 504         }));
 505     }
 506     // FIXME: warn about ambiguity
 507     debug!("the candidates were {:?}", candidates);
 508     candidates.pop().map(|(_, kind)| kind)
 509 }
 510
 511 /// Given a type, return all traits in scope in `module` implemented by that type.
 512 ///
 513 /// NOTE: this cannot be a query because more traits could be available when more crates are compiled!
 514 /// So it is not stable to serialize cross-crate.
 515 fn traits_implemented_by(cx: &DocContext<'_>, type_: DefId, module: DefId) -> FxHashSet<DefId> {
 516     let mut cache = cx.module_trait_cache.borrow_mut();
 517     let in_scope_traits = cache.entry(module).or_insert_with(|| {
 518         cx.enter_resolver(|resolver| {
 519             resolver.traits_in_scope(module).into_iter().map(|candidate| candidate.def_id).collect()
 520         })
 521     });
 522
 523     let ty = cx.tcx.type_of(type_);
 524     let iter = in_scope_traits.iter().flat_map(|&trait_| {
 525         trace!("considering explicit impl for trait {:?}", trait_);
 526         let mut saw_impl = false;
 527         // Look at each trait implementation to see if it's an impl for `did`
 528         cx.tcx.for_each_relevant_impl(trait_, ty, |impl_| {
 529             // FIXME: this is inefficient, find a way to short-circuit for_each_* so this doesn't take as long
 530             if saw_impl {
 531                 return;
 532             }
 533
 534             let trait_ref = cx.tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
 535             // Check if these are the same type.
 536             let impl_type = trait_ref.self_ty();
 537             debug!(
 538                 "comparing type {} with kind {:?} against type {:?}",
 539                 impl_type, impl_type.kind, type_
 540             );
 541             // Fast path: if this is a primitive simple `==` will work
 542             saw_impl = impl_type == ty
 543                 || match impl_type.kind {
 544                     // Check if these are the same def_id
 545                     ty::Adt(def, _) => {
 546                         debug!("adt def_id: {:?}", def.did);
 547                         def.did == type_
 548                     }
 549                     ty::Foreign(def_id) => def_id == type_,
 550                     _ => false,
 551                 };
 552         });
 553         if saw_impl { Some(trait_) } else { None }
 554     });
 555     iter.collect()
 556 }
 557
 558 /// Check for resolve collisions between a trait and its derive
 559 ///
 560 /// These are common and we should just resolve to the trait in that case
 561 fn is_derive_trait_collision<T>(ns: &PerNS<Option<(Res, T)>>) -> bool {
 562     if let PerNS {
 563         type_ns: Some((Res::Def(DefKind::Trait, _), _)),
 564         macro_ns: Some((Res::Def(DefKind::Macro(MacroKind::Derive), _), _)),
 565         ..
 566     } = *ns
 567     {
 568         true
 569     } else {
 570         false
 571     }
 572 }
 573
 574 impl<'a, 'tcx> DocFolder for LinkCollector<'a, 'tcx> {
 575     fn fold_item(&mut self, mut item: Item) -> Option<Item> {
 576         use rustc_middle::ty::DefIdTree;
 577
 578         let parent_node = if item.is_fake() {
 579             // FIXME: is this correct?
 580             None
 581         } else {
 582             let mut current = item.def_id;
 583             // The immediate parent might not always be a module.
 584             // Find the first parent which is.
 585             loop {
 586                 if let Some(parent) = self.cx.tcx.parent(current) {
 587                     if self.cx.tcx.def_kind(parent) == DefKind::Mod {
 588                         break Some(parent);
 589                     }
 590                     current = parent;
 591                 } else {
 592                     break None;
 593                 }
 594             }
 595         };
 596
 597         if parent_node.is_some() {
 598             trace!("got parent node for {:?} {:?}, id {:?}", item.type_(), item.name, item.def_id);
 599         }
 600
 601         let current_item = match item.inner {
 602             ModuleItem(..) => {
 603                 if item.attrs.inner_docs {
 604                     if item.def_id.is_top_level_module() { item.name.clone() } else { None }
 605                 } else {
 606                     match parent_node.or(self.mod_ids.last().copied()) {
 607                         Some(parent) if !parent.is_top_level_module() => {
 608                             // FIXME: can we pull the parent module's name from elsewhere?
 609                             Some(self.cx.tcx.item_name(parent).to_string())
 610                         }
 611                         _ => None,
 612                     }
 613                 }
 614             }
 615             ImplItem(Impl { ref for_, .. }) => {
 616                 for_.def_id().map(|did| self.cx.tcx.item_name(did).to_string())
 617             }
 618             // we don't display docs on `extern crate` items anyway, so don't process them.
 619             ExternCrateItem(..) => {
 620                 debug!("ignoring extern crate item {:?}", item.def_id);
 621                 return self.fold_item_recur(item);
 622             }
 623             ImportItem(Import::Simple(ref name, ..)) => Some(name.clone()),
 624             MacroItem(..) => None,
 625             _ => item.name.clone(),
 626         };
 627
 628         if item.is_mod() && item.attrs.inner_docs {
 629             self.mod_ids.push(item.def_id);
 630         }
 631
 632         let cx = self.cx;
 633         let dox = item.attrs.collapsed_doc_value().unwrap_or_else(String::new);
 634         trace!("got documentation '{}'", dox);
 635
 636         // find item's parent to resolve `Self` in item's docs below
 637         let parent_name = self.cx.as_local_hir_id(item.def_id).and_then(|item_hir| {
 638             let parent_hir = self.cx.tcx.hir().get_parent_item(item_hir);
 639             let item_parent = self.cx.tcx.hir().find(parent_hir);
 640             match item_parent {
 641                 Some(hir::Node::Item(hir::Item {
 642                     kind:
 643                         hir::ItemKind::Impl {
 644                             self_ty:
 645                                 hir::Ty {
 646                                     kind:
 647                                         hir::TyKind::Path(hir::QPath::Resolved(
 648                                             _,
 649                                             hir::Path { segments, .. },
 650                                         )),
 651                                     ..
 652                                 },
 653                             ..
 654                         },
 655                     ..
 656                 })) => segments.first().map(|seg| seg.ident.to_string()),
 657                 Some(hir::Node::Item(hir::Item {
 658                     ident, kind: hir::ItemKind::Enum(..), ..
 659                 }))
 660                 | Some(hir::Node::Item(hir::Item {
 661                     ident, kind: hir::ItemKind::Struct(..), ..
 662                 }))
 663                 | Some(hir::Node::Item(hir::Item {
 664                     ident, kind: hir::ItemKind::Union(..), ..
 665                 }))
 666                 | Some(hir::Node::Item(hir::Item {
 667                     ident, kind: hir::ItemKind::Trait(..), ..
 668                 })) => Some(ident.to_string()),
 669                 _ => None,
 670             }
 671         });
 672
 673         for (ori_link, link_range) in markdown_links(&dox) {
 674             trace!("considering link '{}'", ori_link);
 675
 676             // Bail early for real links.
 677             if ori_link.contains('/') {
 678                 continue;
 679             }
 680
 681             // [] is mostly likely not supposed to be a link
 682             if ori_link.is_empty() {
 683                 continue;
 684             }
 685
 686             let link = ori_link.replace("`", "");
 687             let parts = link.split('#').collect::<Vec<_>>();
 688             let (link, extra_fragment) = if parts.len() > 2 {
 689                 anchor_failure(cx, &item, &link, &dox, link_range, AnchorFailure::MultipleAnchors);
 690                 continue;
 691             } else if parts.len() == 2 {
 692                 if parts[0].trim().is_empty() {
 693                     // This is an anchor to an element of the current page, nothing to do in here!
 694                     continue;
 695                 }
 696                 (parts[0].to_owned(), Some(parts[1].to_owned()))
 697             } else {
 698                 (parts[0].to_owned(), None)
 699             };
 700             let resolved_self;
 701             let mut path_str;
 702             let disambiguator;
 703             let (mut res, mut fragment) = {
 704                 path_str = if let Ok((d, path)) = Disambiguator::from_str(&link) {
 705                     disambiguator = Some(d);
 706                     path
 707                 } else {
 708                     disambiguator = None;
 709                     &link
 710                 }
 711                 .trim();
 712
 713                 if path_str.contains(|ch: char| !(ch.is_alphanumeric() || ch == ':' || ch == '_')) {
 714                     continue;
 715                 }
 716
 717                 // In order to correctly resolve intra-doc-links we need to
 718                 // pick a base AST node to work from.  If the documentation for
 719                 // this module came from an inner comment (//!) then we anchor
 720                 // our name resolution *inside* the module.  If, on the other
 721                 // hand it was an outer comment (///) then we anchor the name
 722                 // resolution in the parent module on the basis that the names
 723                 // used are more likely to be intended to be parent names.  For
 724                 // this, we set base_node to None for inner comments since
 725                 // we've already pushed this node onto the resolution stack but
 726                 // for outer comments we explicitly try and resolve against the
 727                 // parent_node first.
 728                 let base_node = if item.is_mod() && item.attrs.inner_docs {
 729                     self.mod_ids.last().copied()
 730                 } else {
 731                     parent_node
 732                 };
 733
 734                 // replace `Self` with suitable item's parent name
 735                 if path_str.starts_with("Self::") {
 736                     if let Some(ref name) = parent_name {
 737                         resolved_self = format!("{}::{}", name, &path_str[6..]);
 738                         path_str = &resolved_self;
 739                     }
 740                 }
 741
 742                 match disambiguator.map(Disambiguator::ns) {
 743                     Some(ns @ (ValueNS | TypeNS)) => {
 744                         match self.resolve(path_str, ns, &current_item, base_node, &extra_fragment)
 745                         {
 746                             Ok(res) => res,
 747                             Err(ErrorKind::ResolutionFailure) => {
 748                                 resolution_failure(cx, &item, path_str, &dox, link_range);
 749                                 // This could just be a normal link or a broken link
 750                                 // we could potentially check if something is
 751                                 // "intra-doc-link-like" and warn in that case.
 752                                 continue;
 753                             }
 754                             Err(ErrorKind::AnchorFailure(msg)) => {
 755                                 anchor_failure(cx, &item, &ori_link, &dox, link_range, msg);
 756                                 continue;
 757                             }
 758                         }
 759                     }
 760                     None => {
 761                         // Try everything!
 762                         let mut candidates = PerNS {
 763                             macro_ns: self
 764                                 .macro_resolve(path_str, base_node)
 765                                 .map(|res| (res, extra_fragment.clone())),
 766                             type_ns: match self.resolve(
 767                                 path_str,
 768                                 TypeNS,
 769                                 &current_item,
 770                                 base_node,
 771                                 &extra_fragment,
 772                             ) {
 773                                 Ok(res) => {
 774                                     debug!("got res in TypeNS: {:?}", res);
 775                                     Some(res)
 776                                 }
 777                                 Err(ErrorKind::AnchorFailure(msg)) => {
 778                                     anchor_failure(cx, &item, &ori_link, &dox, link_range, msg);
 779                                     continue;
 780                                 }
 781                                 Err(ErrorKind::ResolutionFailure) => None,
 782                             },
 783                             value_ns: match self.resolve(
 784                                 path_str,
 785                                 ValueNS,
 786                                 &current_item,
 787                                 base_node,
 788                                 &extra_fragment,
 789                             ) {
 790                                 Ok(res) => Some(res),
 791                                 Err(ErrorKind::AnchorFailure(msg)) => {
 792                                     anchor_failure(cx, &item, &ori_link, &dox, link_range, msg);
 793                                     continue;
 794                                 }
 795                                 Err(ErrorKind::ResolutionFailure) => None,
 796                             }
 797                             .and_then(|(res, fragment)| {
 798                                 // Constructors are picked up in the type namespace.
 799                                 match res {
 800                                     Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) => None,
 801                                     _ => match (fragment, extra_fragment) {
 802                                         (Some(fragment), Some(_)) => {
 803                                             // Shouldn't happen but who knows?
 804                                             Some((res, Some(fragment)))
 805                                         }
 806                                         (fragment, None) | (None, fragment) => {
 807                                             Some((res, fragment))
 808                                         }
 809                                     },
 810                                 }
 811                             }),
 812                         };
 813
 814                         if candidates.is_empty() {
 815                             resolution_failure(cx, &item, path_str, &dox, link_range);
 816                             // this could just be a normal link
 817                             continue;
 818                         }
 819
 820                         let len = candidates.clone().present_items().count();
 821
 822                         if len == 1 {
 823                             candidates.present_items().next().unwrap()
 824                         } else if len == 2 && is_derive_trait_collision(&candidates) {
 825                             candidates.type_ns.unwrap()
 826                         } else {
 827                             if is_derive_trait_collision(&candidates) {
 828                                 candidates.macro_ns = None;
 829                             }
 830                             let candidates =
 831                                 candidates.map(|candidate| candidate.map(|(res, _)| res));
 832                             let candidates = [TypeNS, ValueNS, MacroNS]
 833                                 .iter()
 834                                 .filter_map(|&ns| candidates[ns].map(|res| (res, ns)));
 835                             ambiguity_error(
 836                                 cx,
 837                                 &item,
 838                                 path_str,
 839                                 &dox,
 840                                 link_range,
 841                                 candidates.collect(),
 842                             );
 843                             continue;
 844                         }
 845                     }
 846                     Some(MacroNS) => {
 847                         if let Some(res) = self.macro_resolve(path_str, base_node) {
 848                             (res, extra_fragment)
 849                         } else {
 850                             resolution_failure(cx, &item, path_str, &dox, link_range);
 851                             continue;
 852                         }
 853                     }
 854                 }
 855             };
 856
 857             // Check for a primitive which might conflict with a module
 858             // Report the ambiguity and require that the user specify which one they meant.
 859             // FIXME: could there ever be a primitive not in the type namespace?
 860             if matches!(
 861                 disambiguator,
 862                 None | Some(Disambiguator::Namespace(Namespace::TypeNS) | Disambiguator::Primitive)
 863             ) && !matches!(res, Res::PrimTy(_))
 864             {
 865                 if let Some((path, prim)) = is_primitive(path_str, TypeNS) {
 866                     // `prim@char`
 867                     if matches!(disambiguator, Some(Disambiguator::Primitive)) {
 868                         if fragment.is_some() {
 869                             anchor_failure(
 870                                 cx,
 871                                 &item,
 872                                 path_str,
 873                                 &dox,
 874                                 link_range,
 875                                 AnchorFailure::Primitive,
 876                             );
 877                             continue;
 878                         }
 879                         res = prim;
 880                         fragment = Some(path.to_owned());
 881                     } else {
 882                         // `[char]` when a `char` module is in scope
 883                         let candidates = vec![(res, TypeNS), (prim, TypeNS)];
 884                         ambiguity_error(cx, &item, path_str, &dox, link_range, candidates);
 885                         continue;
 886                     }
 887                 }
 888             }
 889
 890             let report_mismatch = |specified: Disambiguator, resolved: Disambiguator| {
 891                 // The resolved item did not match the disambiguator; give a better error than 'not found'
 892                 let msg = format!("incompatible link kind for `{}`", path_str);
 893                 report_diagnostic(cx, &msg, &item, &dox, link_range.clone(), |diag, sp| {
 894                     let note = format!(
 895                         "this link resolved to {} {}, which is not {} {}",
 896                         resolved.article(),
 897                         resolved.descr(),
 898                         specified.article(),
 899                         specified.descr()
 900                     );
 901                     let suggestion = resolved.display_for(path_str);
 902                     let help_msg =
 903                         format!("to link to the {}, use its disambiguator", resolved.descr());
 904                     diag.note(&note);
 905                     if let Some(sp) = sp {
 906                         diag.span_suggestion(
 907                             sp,
 908                             &help_msg,
 909                             suggestion,
 910                             Applicability::MaybeIncorrect,
 911                         );
 912                     } else {
 913                         diag.help(&format!("{}: {}", help_msg, suggestion));
 914                     }
 915                 });
 916             };
 917             if let Res::PrimTy(_) = res {
 918                 match disambiguator {
 919                     Some(Disambiguator::Primitive | Disambiguator::Namespace(_)) | None => {
 920                         item.attrs.links.push((ori_link, None, fragment))
 921                     }
 922                     Some(other) => {
 923                         report_mismatch(other, Disambiguator::Primitive);
 924                         continue;
 925                     }
 926                 }
 927             } else {
 928                 debug!("intra-doc link to {} resolved to {:?}", path_str, res);
 929
 930                 // Disallow e.g. linking to enums with `struct@`
 931                 if let Res::Def(kind, _) = res {
 932                     debug!("saw kind {:?} with disambiguator {:?}", kind, disambiguator);
 933                     match (self.kind_side_channel.take().unwrap_or(kind), disambiguator) {
 934                         | (DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst, Some(Disambiguator::Kind(DefKind::Const)))
 935                         // NOTE: this allows 'method' to mean both normal functions and associated functions
 936                         // This can't cause ambiguity because both are in the same namespace.
 937                         | (DefKind::Fn | DefKind::AssocFn, Some(Disambiguator::Kind(DefKind::Fn)))
 938                         // These are namespaces; allow anything in the namespace to match
 939                         | (_, Some(Disambiguator::Namespace(_)))
 940                         // If no disambiguator given, allow anything
 941                         | (_, None)
 942                         // All of these are valid, so do nothing
 943                         => {}
 944                         (actual, Some(Disambiguator::Kind(expected))) if actual == expected => {}
 945                         (_, Some(specified @ Disambiguator::Kind(_) | specified @ Disambiguator::Primitive)) => {
 946                             report_mismatch(specified, Disambiguator::Kind(kind));
 947                             continue;
 948                         }
 949                     }
 950                 }
 951
 952                 // item can be non-local e.g. when using #[doc(primitive = "pointer")]
 953                 if let Some((src_id, dst_id)) = res
 954                     .opt_def_id()
 955                     .and_then(|def_id| def_id.as_local())
 956                     .and_then(|dst_id| item.def_id.as_local().map(|src_id| (src_id, dst_id)))
 957                 {
 958                     use rustc_hir::def_id::LOCAL_CRATE;
 959
 960                     let hir_src = self.cx.tcx.hir().local_def_id_to_hir_id(src_id);
 961                     let hir_dst = self.cx.tcx.hir().local_def_id_to_hir_id(dst_id);
 962
 963                     if self.cx.tcx.privacy_access_levels(LOCAL_CRATE).is_exported(hir_src)
 964                         && !self.cx.tcx.privacy_access_levels(LOCAL_CRATE).is_exported(hir_dst)
 965                     {
 966                         privacy_error(cx, &item, &path_str, &dox, link_range);
 967                         continue;
 968                     }
 969                 }
 970                 let id = register_res(cx, res);
 971                 item.attrs.links.push((ori_link, Some(id), fragment));
 972             }
 973         }
 974
 975         if item.is_mod() && !item.attrs.inner_docs {
 976             self.mod_ids.push(item.def_id);
 977         }
 978
 979         if item.is_mod() {
 980             let ret = self.fold_item_recur(item);
 981
 982             self.mod_ids.pop();
 983
 984             ret
 985         } else {
 986             self.fold_item_recur(item)
 987         }
 988     }
 989
 990     // FIXME: if we can resolve intra-doc links from other crates, we can use the stock
 991     // `fold_crate`, but until then we should avoid scanning `krate.external_traits` since those
 992     // will never resolve properly
 993     fn fold_crate(&mut self, mut c: Crate) -> Crate {
 994         c.module = c.module.take().and_then(|module| self.fold_item(module));
 995
 996         c
 997     }
 998 }
 999
1000 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
1001 enum Disambiguator {
1002     Primitive,
1003     Kind(DefKind),
1004     Namespace(Namespace),
1005 }
1006
1007 impl Disambiguator {
1008     /// (disambiguator, path_str)
1009     fn from_str(link: &str) -> Result<(Self, &str), ()> {
1010         use Disambiguator::{Kind, Namespace as NS, Primitive};
1011
1012         let find_suffix = || {
1013             let suffixes = [
1014                 ("!()", DefKind::Macro(MacroKind::Bang)),
1015                 ("()", DefKind::Fn),
1016                 ("!", DefKind::Macro(MacroKind::Bang)),
1017             ];
1018             for &(suffix, kind) in &suffixes {
1019                 if link.ends_with(suffix) {
1020                     return Ok((Kind(kind), link.trim_end_matches(suffix)));
1021                 }
1022             }
1023             Err(())
1024         };
1025
1026         if let Some(idx) = link.find('@') {
1027             let (prefix, rest) = link.split_at(idx);
1028             let d = match prefix {
1029                 "struct" => Kind(DefKind::Struct),
1030                 "enum" => Kind(DefKind::Enum),
1031                 "trait" => Kind(DefKind::Trait),
1032                 "union" => Kind(DefKind::Union),
1033                 "module" | "mod" => Kind(DefKind::Mod),
1034                 "const" | "constant" => Kind(DefKind::Const),
1035                 "static" => Kind(DefKind::Static),
1036                 "function" | "fn" | "method" => Kind(DefKind::Fn),
1037                 "derive" => Kind(DefKind::Macro(MacroKind::Derive)),
1038                 "type" => NS(Namespace::TypeNS),
1039                 "value" => NS(Namespace::ValueNS),
1040                 "macro" => NS(Namespace::MacroNS),
1041                 "prim" | "primitive" => Primitive,
1042                 _ => return find_suffix(),
1043             };
1044             Ok((d, &rest[1..]))
1045         } else {
1046             find_suffix()
1047         }
1048     }
1049
1050     fn display_for(self, path_str: &str) -> String {
1051         let kind = match self {
1052             Disambiguator::Primitive => return format!("prim@{}", path_str),
1053             Disambiguator::Kind(kind) => kind,
1054             Disambiguator::Namespace(_) => panic!("display_for cannot be used on namespaces"),
1055         };
1056         if kind == DefKind::Macro(MacroKind::Bang) {
1057             return format!("{}!", path_str);
1058         } else if kind == DefKind::Fn || kind == DefKind::AssocFn {
1059             return format!("{}()", path_str);
1060         }
1061         let prefix = match kind {
1062             DefKind::Struct => "struct",
1063             DefKind::Enum => "enum",
1064             DefKind::Trait => "trait",
1065             DefKind::Union => "union",
1066             DefKind::Mod => "mod",
1067             DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst => {
1068                 "const"
1069             }
1070             DefKind::Static => "static",
1071             DefKind::Macro(MacroKind::Derive) => "derive",
1072             // Now handle things that don't have a specific disambiguator
1073             _ => match kind
1074                 .ns()
1075                 .expect("tried to calculate a disambiguator for a def without a namespace?")
1076             {
1077                 Namespace::TypeNS => "type",
1078                 Namespace::ValueNS => "value",
1079                 Namespace::MacroNS => "macro",
1080             },
1081         };
1082         format!("{}@{}", prefix, path_str)
1083     }
1084
1085     fn ns(self) -> Namespace {
1086         match self {
1087             Self::Namespace(n) => n,
1088             Self::Kind(k) => {
1089                 k.ns().expect("only DefKinds with a valid namespace can be disambiguators")
1090             }
1091             Self::Primitive => TypeNS,
1092         }
1093     }
1094
1095     fn article(self) -> &'static str {
1096         match self {
1097             Self::Namespace(_) => panic!("article() doesn't make sense for namespaces"),
1098             Self::Kind(k) => k.article(),
1099             Self::Primitive => "a",
1100         }
1101     }
1102
1103     fn descr(self) -> &'static str {
1104         match self {
1105             Self::Namespace(n) => n.descr(),
1106             // HACK(jynelson): by looking at the source I saw the DefId we pass
1107             // for `expected.descr()` doesn't matter, since it's not a crate
1108             Self::Kind(k) => k.descr(DefId::local(hir::def_id::DefIndex::from_usize(0))),
1109             Self::Primitive => "builtin type",
1110         }
1111     }
1112 }
1113
1114 /// Reports a diagnostic for an intra-doc link.
1115 ///
1116 /// If no link range is provided, or the source span of the link cannot be determined, the span of
1117 /// the entire documentation block is used for the lint. If a range is provided but the span
1118 /// calculation fails, a note is added to the diagnostic pointing to the link in the markdown.
1119 ///
1120 /// The `decorate` callback is invoked in all cases to allow further customization of the
1121 /// diagnostic before emission. If the span of the link was able to be determined, the second
1122 /// parameter of the callback will contain it, and the primary span of the diagnostic will be set
1123 /// to it.
1124 fn report_diagnostic(
1125     cx: &DocContext<'_>,
1126     msg: &str,
1127     item: &Item,
1128     dox: &str,
1129     link_range: Option<Range<usize>>,
1130     decorate: impl FnOnce(&mut DiagnosticBuilder<'_>, Option<rustc_span::Span>),
1131 ) {
1132     let hir_id = match cx.as_local_hir_id(item.def_id) {
1133         Some(hir_id) => hir_id,
1134         None => {
1135             // If non-local, no need to check anything.
1136             info!("ignoring warning from parent crate: {}", msg);
1137             return;
1138         }
1139     };
1140
1141     let attrs = &item.attrs;
1142     let sp = span_of_attrs(attrs).unwrap_or(item.source.span());
1143
1144     cx.tcx.struct_span_lint_hir(lint::builtin::BROKEN_INTRA_DOC_LINKS, hir_id, sp, |lint| {
1145         let mut diag = lint.build(msg);
1146
1147         let span = link_range
1148             .as_ref()
1149             .and_then(|range| super::source_span_for_markdown_range(cx, dox, range, attrs));
1150
1151         if let Some(link_range) = link_range {
1152             if let Some(sp) = span {
1153                 diag.set_span(sp);
1154             } else {
1155                 // blah blah blah\nblah\nblah [blah] blah blah\nblah blah
1156                 //                       ^     ~~~~
1157                 //                       |     link_range
1158                 //                       last_new_line_offset
1159                 let last_new_line_offset = dox[..link_range.start].rfind('\n').map_or(0, |n| n + 1);
1160                 let line = dox[last_new_line_offset..].lines().next().unwrap_or("");
1161
1162                 // Print the line containing the `link_range` and manually mark it with '^'s.
1163                 diag.note(&format!(
1164                     "the link appears in this line:\n\n{line}\n\
1165                          {indicator: <before$}{indicator:^<found$}",
1166                     line = line,
1167                     indicator = "",
1168                     before = link_range.start - last_new_line_offset,
1169                     found = link_range.len(),
1170                 ));
1171             }
1172         }
1173
1174         decorate(&mut diag, span);
1175
1176         diag.emit();
1177     });
1178 }
1179
1180 fn resolution_failure(
1181     cx: &DocContext<'_>,
1182     item: &Item,
1183     path_str: &str,
1184     dox: &str,
1185     link_range: Option<Range<usize>>,
1186 ) {
1187     report_diagnostic(
1188         cx,
1189         &format!("unresolved link to `{}`", path_str),
1190         item,
1191         dox,
1192         link_range,
1193         |diag, sp| {
1194             if let Some(sp) = sp {
1195                 diag.span_label(sp, "unresolved link");
1196             }
1197
1198             diag.help(r#"to escape `[` and `]` characters, add '\' before them like `\[` or `\]`"#);
1199         },
1200     );
1201 }
1202
1203 fn anchor_failure(
1204     cx: &DocContext<'_>,
1205     item: &Item,
1206     path_str: &str,
1207     dox: &str,
1208     link_range: Option<Range<usize>>,
1209     failure: AnchorFailure,
1210 ) {
1211     let msg = match failure {
1212         AnchorFailure::MultipleAnchors => format!("`{}` contains multiple anchors", path_str),
1213         AnchorFailure::Primitive
1214         | AnchorFailure::Variant
1215         | AnchorFailure::AssocConstant
1216         | AnchorFailure::AssocType
1217         | AnchorFailure::Field
1218         | AnchorFailure::Method => {
1219             let kind = match failure {
1220                 AnchorFailure::Primitive => "primitive type",
1221                 AnchorFailure::Variant => "enum variant",
1222                 AnchorFailure::AssocConstant => "associated constant",
1223                 AnchorFailure::AssocType => "associated type",
1224                 AnchorFailure::Field => "struct field",
1225                 AnchorFailure::Method => "method",
1226                 AnchorFailure::MultipleAnchors => unreachable!("should be handled already"),
1227             };
1228
1229             format!(
1230                 "`{}` contains an anchor, but links to {kind}s are already anchored",
1231                 path_str,
1232                 kind = kind
1233             )
1234         }
1235     };
1236
1237     report_diagnostic(cx, &msg, item, dox, link_range, |diag, sp| {
1238         if let Some(sp) = sp {
1239             diag.span_label(sp, "contains invalid anchor");
1240         }
1241     });
1242 }
1243
1244 fn ambiguity_error(
1245     cx: &DocContext<'_>,
1246     item: &Item,
1247     path_str: &str,
1248     dox: &str,
1249     link_range: Option<Range<usize>>,
1250     candidates: Vec<(Res, Namespace)>,
1251 ) {
1252     let mut msg = format!("`{}` is ", path_str);
1253
1254     match candidates.as_slice() {
1255         [(first_def, _), (second_def, _)] => {
1256             msg += &format!(
1257                 "both {} {} and {} {}",
1258                 first_def.article(),
1259                 first_def.descr(),
1260                 second_def.article(),
1261                 second_def.descr(),
1262             );
1263         }
1264         _ => {
1265             let mut candidates = candidates.iter().peekable();
1266             while let Some((res, _)) = candidates.next() {
1267                 if candidates.peek().is_some() {
1268                     msg += &format!("{} {}, ", res.article(), res.descr());
1269                 } else {
1270                     msg += &format!("and {} {}", res.article(), res.descr());
1271                 }
1272             }
1273         }
1274     }
1275
1276     report_diagnostic(cx, &msg, item, dox, link_range.clone(), |diag, sp| {
1277         if let Some(sp) = sp {
1278             diag.span_label(sp, "ambiguous link");
1279
1280             let link_range = link_range.expect("must have a link range if we have a span");
1281
1282             for (res, ns) in candidates {
1283                 let (action, mut suggestion) = match res {
1284                     Res::Def(DefKind::AssocFn | DefKind::Fn, _) => {
1285                         ("add parentheses", format!("{}()", path_str))
1286                     }
1287                     Res::Def(DefKind::Macro(MacroKind::Bang), _) => {
1288                         ("add an exclamation mark", format!("{}!", path_str))
1289                     }
1290                     _ => {
1291                         let type_ = match (res, ns) {
1292                             (Res::PrimTy(_), _) => "prim",
1293                             (Res::Def(DefKind::Const, _), _) => "const",
1294                             (Res::Def(DefKind::Static, _), _) => "static",
1295                             (Res::Def(DefKind::Struct, _), _) => "struct",
1296                             (Res::Def(DefKind::Enum, _), _) => "enum",
1297                             (Res::Def(DefKind::Union, _), _) => "union",
1298                             (Res::Def(DefKind::Trait, _), _) => "trait",
1299                             (Res::Def(DefKind::Mod, _), _) => "module",
1300                             (_, TypeNS) => "type",
1301                             (_, ValueNS) => "value",
1302                             (Res::Def(DefKind::Macro(MacroKind::Derive), _), MacroNS) => "derive",
1303                             (_, MacroNS) => "macro",
1304                         };
1305
1306                         // FIXME: if this is an implied shortcut link, it's bad style to suggest `@`
1307                         ("prefix with the item type", format!("{}@{}", type_, path_str))
1308                     }
1309                 };
1310
1311                 if dox.bytes().nth(link_range.start) == Some(b'`') {
1312                     suggestion = format!("`{}`", suggestion);
1313                 }
1314
1315                 // FIXME: Create a version of this suggestion for when we don't have the span.
1316                 diag.span_suggestion(
1317                     sp,
1318                     &format!("to link to the {}, {}", res.descr(), action),
1319                     suggestion,
1320                     Applicability::MaybeIncorrect,
1321                 );
1322             }
1323         }
1324     });
1325 }
1326
1327 fn privacy_error(
1328     cx: &DocContext<'_>,
1329     item: &Item,
1330     path_str: &str,
1331     dox: &str,
1332     link_range: Option<Range<usize>>,
1333 ) {
1334     let item_name = item.name.as_deref().unwrap_or("<unknown>");
1335     let msg =
1336         format!("public documentation for `{}` links to private item `{}`", item_name, path_str);
1337
1338     report_diagnostic(cx, &msg, item, dox, link_range, |diag, sp| {
1339         if let Some(sp) = sp {
1340             diag.span_label(sp, "this item is private");
1341         }
1342
1343         let note_msg = if cx.render_options.document_private {
1344             "this link resolves only because you passed `--document-private-items`, but will break without"
1345         } else {
1346             "this link will resolve properly if you pass `--document-private-items`"
1347         };
1348         diag.note(note_msg);
1349     });
1350 }
1351
1352 /// Given an enum variant's res, return the res of its enum and the associated fragment.
1353 fn handle_variant(
1354     cx: &DocContext<'_>,
1355     res: Res,
1356     extra_fragment: &Option<String>,
1357 ) -> Result<(Res, Option<String>), ErrorKind> {
1358     use rustc_middle::ty::DefIdTree;
1359
1360     if extra_fragment.is_some() {
1361         return Err(ErrorKind::AnchorFailure(AnchorFailure::Variant));
1362     }
1363     let parent = if let Some(parent) = cx.tcx.parent(res.def_id()) {
1364         parent
1365     } else {
1366         return Err(ErrorKind::ResolutionFailure);
1367     };
1368     let parent_def = Res::Def(DefKind::Enum, parent);
1369     let variant = cx.tcx.expect_variant_res(res);
1370     Ok((parent_def, Some(format!("variant.{}", variant.ident.name))))
1371 }
1372
1373 const PRIMITIVES: &[(&str, Res)] = &[
1374     ("u8", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U8))),
1375     ("u16", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U16))),
1376     ("u32", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U32))),
1377     ("u64", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U64))),
1378     ("u128", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::U128))),
1379     ("usize", Res::PrimTy(hir::PrimTy::Uint(rustc_ast::UintTy::Usize))),
1380     ("i8", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I8))),
1381     ("i16", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I16))),
1382     ("i32", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I32))),
1383     ("i64", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I64))),
1384     ("i128", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::I128))),
1385     ("isize", Res::PrimTy(hir::PrimTy::Int(rustc_ast::IntTy::Isize))),
1386     ("f32", Res::PrimTy(hir::PrimTy::Float(rustc_ast::FloatTy::F32))),
1387     ("f64", Res::PrimTy(hir::PrimTy::Float(rustc_ast::FloatTy::F64))),
1388     ("str", Res::PrimTy(hir::PrimTy::Str)),
1389     ("bool", Res::PrimTy(hir::PrimTy::Bool)),
1390     ("true", Res::PrimTy(hir::PrimTy::Bool)),
1391     ("false", Res::PrimTy(hir::PrimTy::Bool)),
1392     ("char", Res::PrimTy(hir::PrimTy::Char)),
1393 ];
1394
1395 fn is_primitive(path_str: &str, ns: Namespace) -> Option<(&'static str, Res)> {
1396     if ns == TypeNS {
1397         PRIMITIVES
1398             .iter()
1399             .filter(|x| x.0 == path_str)
1400             .copied()
1401             .map(|x| if x.0 == "true" || x.0 == "false" { ("bool", x.1) } else { x })
1402             .next()
1403     } else {
1404         None
1405     }
1406 }
1407
1408 fn primitive_impl(cx: &DocContext<'_>, path_str: &str) -> Option<&'static SmallVec<[DefId; 4]>> {
1409     Some(PrimitiveType::from_symbol(Symbol::intern(path_str))?.impls(cx.tcx))
1410 }