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