src/librustc_hir/definitions.rs

   1 //! For each definition, we track the following data. A definition
   2 //! here is defined somewhat circularly as "something with a `DefId`",
   3 //! but it generally corresponds to things like structs, enums, etc.
   4 //! There are also some rather random cases (like const initializer
   5 //! expressions) that are mostly just leftovers.
   6
   7 pub use crate::def_id::DefPathHash;
   8 use crate::def_id::{CrateNum, DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
   9 use crate::hir;
  10
  11 use rustc_ast::ast;
  12 use rustc_ast::crate_disambiguator::CrateDisambiguator;
  13 use rustc_data_structures::fx::FxHashMap;
  14 use rustc_data_structures::stable_hasher::StableHasher;
  15 use rustc_index::vec::IndexVec;
  16 use rustc_span::hygiene::ExpnId;
  17 use rustc_span::symbol::{sym, Symbol};
  18 use rustc_span::Span;
  19
  20 use log::debug;
  21 use std::fmt::Write;
  22 use std::hash::Hash;
  23
  24 /// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
  25 /// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`
  26 /// stores the `DefIndex` of its parent.
  27 /// There is one `DefPathTable` for each crate.
  28 #[derive(Clone, Default, RustcDecodable, RustcEncodable)]
  29 pub struct DefPathTable {
  30     index_to_key: IndexVec<DefIndex, DefKey>,
  31     def_path_hashes: IndexVec<DefIndex, DefPathHash>,
  32 }
  33
  34 impl DefPathTable {
  35     fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
  36         let index = {
  37             let index = DefIndex::from(self.index_to_key.len());
  38             debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
  39             self.index_to_key.push(key);
  40             index
  41         };
  42         self.def_path_hashes.push(def_path_hash);
  43         debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
  44         index
  45     }
  46
  47     pub fn next_id(&self) -> DefIndex {
  48         DefIndex::from(self.index_to_key.len())
  49     }
  50
  51     #[inline(always)]
  52     pub fn def_key(&self, index: DefIndex) -> DefKey {
  53         self.index_to_key[index]
  54     }
  55
  56     #[inline(always)]
  57     pub fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
  58         let hash = self.def_path_hashes[index];
  59         debug!("def_path_hash({:?}) = {:?}", index, hash);
  60         hash
  61     }
  62
  63     pub fn add_def_path_hashes_to(&self, cnum: CrateNum, out: &mut FxHashMap<DefPathHash, DefId>) {
  64         out.extend(self.def_path_hashes.iter().enumerate().map(|(index, &hash)| {
  65             let def_id = DefId { krate: cnum, index: DefIndex::from(index) };
  66             (hash, def_id)
  67         }));
  68     }
  69
  70     pub fn size(&self) -> usize {
  71         self.index_to_key.len()
  72     }
  73 }
  74
  75 /// The definition table containing node definitions.
  76 /// It holds the `DefPathTable` for local `DefId`s/`DefPath`s and it also stores a
  77 /// mapping from `NodeId`s to local `DefId`s.
  78 #[derive(Clone, Default)]
  79 pub struct Definitions {
  80     table: DefPathTable,
  81
  82     def_id_to_span: IndexVec<LocalDefId, Span>,
  83
  84     // FIXME(eddyb) don't go through `ast::NodeId` to convert between `HirId`
  85     // and `LocalDefId` - ideally all `LocalDefId`s would be HIR owners.
  86     node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
  87     def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
  88
  89     pub(super) node_id_to_hir_id: IndexVec<ast::NodeId, Option<hir::HirId>>,
  90     /// The reverse mapping of `node_id_to_hir_id`.
  91     pub(super) hir_id_to_node_id: FxHashMap<hir::HirId, ast::NodeId>,
  92
  93     /// If `ExpnId` is an ID of some macro expansion,
  94     /// then `DefId` is the normal module (`mod`) in which the expanded macro was defined.
  95     parent_modules_of_macro_defs: FxHashMap<ExpnId, DefId>,
  96     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
  97     expansions_that_defined: FxHashMap<LocalDefId, ExpnId>,
  98     next_disambiguator: FxHashMap<(LocalDefId, DefPathData), u32>,
  99     /// When collecting definitions from an AST fragment produced by a macro invocation `ExpnId`
 100     /// we know what parent node that fragment should be attached to thanks to this table.
 101     invocation_parents: FxHashMap<ExpnId, LocalDefId>,
 102     /// Indices of unnamed struct or variant fields with unresolved attributes.
 103     placeholder_field_indices: FxHashMap<ast::NodeId, usize>,
 104 }
 105
 106 /// A unique identifier that we can use to lookup a definition
 107 /// precisely. It combines the index of the definition's parent (if
 108 /// any) with a `DisambiguatedDefPathData`.
 109 #[derive(Copy, Clone, PartialEq, Debug, RustcEncodable, RustcDecodable)]
 110 pub struct DefKey {
 111     /// The parent path.
 112     pub parent: Option<DefIndex>,
 113
 114     /// The identifier of this node.
 115     pub disambiguated_data: DisambiguatedDefPathData,
 116 }
 117
 118 impl DefKey {
 119     fn compute_stable_hash(&self, parent_hash: DefPathHash) -> DefPathHash {
 120         let mut hasher = StableHasher::new();
 121
 122         // We hash a `0u8` here to disambiguate between regular `DefPath` hashes,
 123         // and the special "root_parent" below.
 124         0u8.hash(&mut hasher);
 125         parent_hash.hash(&mut hasher);
 126
 127         let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;
 128
 129         ::std::mem::discriminant(data).hash(&mut hasher);
 130         if let Some(name) = data.get_opt_name() {
 131             // Get a stable hash by considering the symbol chars rather than
 132             // the symbol index.
 133             name.as_str().hash(&mut hasher);
 134         }
 135
 136         disambiguator.hash(&mut hasher);
 137
 138         DefPathHash(hasher.finish())
 139     }
 140
 141     fn root_parent_stable_hash(
 142         crate_name: &str,
 143         crate_disambiguator: CrateDisambiguator,
 144     ) -> DefPathHash {
 145         let mut hasher = StableHasher::new();
 146         // Disambiguate this from a regular `DefPath` hash; see `compute_stable_hash()` above.
 147         1u8.hash(&mut hasher);
 148         crate_name.hash(&mut hasher);
 149         crate_disambiguator.hash(&mut hasher);
 150         DefPathHash(hasher.finish())
 151     }
 152 }
 153
 154 /// A pair of `DefPathData` and an integer disambiguator. The integer is
 155 /// normally `0`, but in the event that there are multiple defs with the
 156 /// same `parent` and `data`, we use this field to disambiguate
 157 /// between them. This introduces some artificial ordering dependency
 158 /// but means that if you have, e.g., two impls for the same type in
 159 /// the same module, they do get distinct `DefId`s.
 160 #[derive(Copy, Clone, PartialEq, Debug, RustcEncodable, RustcDecodable)]
 161 pub struct DisambiguatedDefPathData {
 162     pub data: DefPathData,
 163     pub disambiguator: u32,
 164 }
 165
 166 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 167 pub struct DefPath {
 168     /// The path leading from the crate root to the item.
 169     pub data: Vec<DisambiguatedDefPathData>,
 170
 171     /// The crate root this path is relative to.
 172     pub krate: CrateNum,
 173 }
 174
 175 impl DefPath {
 176     pub fn is_local(&self) -> bool {
 177         self.krate == LOCAL_CRATE
 178     }
 179
 180     pub fn make<FN>(krate: CrateNum, start_index: DefIndex, mut get_key: FN) -> DefPath
 181     where
 182         FN: FnMut(DefIndex) -> DefKey,
 183     {
 184         let mut data = vec![];
 185         let mut index = Some(start_index);
 186         loop {
 187             debug!("DefPath::make: krate={:?} index={:?}", krate, index);
 188             let p = index.unwrap();
 189             let key = get_key(p);
 190             debug!("DefPath::make: key={:?}", key);
 191             match key.disambiguated_data.data {
 192                 DefPathData::CrateRoot => {
 193                     assert!(key.parent.is_none());
 194                     break;
 195                 }
 196                 _ => {
 197                     data.push(key.disambiguated_data);
 198                     index = key.parent;
 199                 }
 200             }
 201         }
 202         data.reverse();
 203         DefPath { data, krate }
 204     }
 205
 206     /// Returns a string representation of the `DefPath` without
 207     /// the crate-prefix. This method is useful if you don't have
 208     /// a `TyCtxt` available.
 209     pub fn to_string_no_crate(&self) -> String {
 210         let mut s = String::with_capacity(self.data.len() * 16);
 211
 212         for component in &self.data {
 213             write!(s, "::{}[{}]", component.data.as_symbol(), component.disambiguator).unwrap();
 214         }
 215
 216         s
 217     }
 218
 219     /// Returns a filename-friendly string for the `DefPath`, with the
 220     /// crate-prefix.
 221     pub fn to_string_friendly<F>(&self, crate_imported_name: F) -> String
 222     where
 223         F: FnOnce(CrateNum) -> Symbol,
 224     {
 225         let crate_name_str = crate_imported_name(self.krate).as_str();
 226         let mut s = String::with_capacity(crate_name_str.len() + self.data.len() * 16);
 227
 228         write!(s, "::{}", crate_name_str).unwrap();
 229
 230         for component in &self.data {
 231             if component.disambiguator == 0 {
 232                 write!(s, "::{}", component.data.as_symbol()).unwrap();
 233             } else {
 234                 write!(s, "{}[{}]", component.data.as_symbol(), component.disambiguator).unwrap();
 235             }
 236         }
 237
 238         s
 239     }
 240
 241     /// Returns a filename-friendly string of the `DefPath`, without
 242     /// the crate-prefix. This method is useful if you don't have
 243     /// a `TyCtxt` available.
 244     pub fn to_filename_friendly_no_crate(&self) -> String {
 245         let mut s = String::with_capacity(self.data.len() * 16);
 246
 247         let mut opt_delimiter = None;
 248         for component in &self.data {
 249             opt_delimiter.map(|d| s.push(d));
 250             opt_delimiter = Some('-');
 251             if component.disambiguator == 0 {
 252                 write!(s, "{}", component.data.as_symbol()).unwrap();
 253             } else {
 254                 write!(s, "{}[{}]", component.data.as_symbol(), component.disambiguator).unwrap();
 255             }
 256         }
 257         s
 258     }
 259 }
 260
 261 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 262 pub enum DefPathData {
 263     // Root: these should only be used for the root nodes, because
 264     // they are treated specially by the `def_path` function.
 265     /// The crate root (marker).
 266     CrateRoot,
 267     // Catch-all for random `DefId` things like `DUMMY_NODE_ID`.
 268     Misc,
 269
 270     // Different kinds of items and item-like things:
 271     /// An impl.
 272     Impl,
 273     /// Something in the type namespace.
 274     TypeNs(Symbol),
 275     /// Something in the value namespace.
 276     ValueNs(Symbol),
 277     /// Something in the macro namespace.
 278     MacroNs(Symbol),
 279     /// Something in the lifetime namespace.
 280     LifetimeNs(Symbol),
 281     /// A closure expression.
 282     ClosureExpr,
 283
 284     // Subportions of items:
 285     /// Implicit constructor for a unit or tuple-like struct or enum variant.
 286     Ctor,
 287     /// A constant expression (see `{ast,hir}::AnonConst`).
 288     AnonConst,
 289     /// An `impl Trait` type node.
 290     ImplTrait,
 291 }
 292
 293 impl Definitions {
 294     pub fn def_path_table(&self) -> &DefPathTable {
 295         &self.table
 296     }
 297
 298     /// Gets the number of definitions.
 299     pub fn def_index_count(&self) -> usize {
 300         self.table.index_to_key.len()
 301     }
 302
 303     pub fn def_key(&self, id: LocalDefId) -> DefKey {
 304         self.table.def_key(id.local_def_index)
 305     }
 306
 307     #[inline(always)]
 308     pub fn def_path_hash(&self, id: LocalDefId) -> DefPathHash {
 309         self.table.def_path_hash(id.local_def_index)
 310     }
 311
 312     /// Returns the path from the crate root to `index`. The root
 313     /// nodes are not included in the path (i.e., this will be an
 314     /// empty vector for the crate root). For an inlined item, this
 315     /// will be the path of the item in the external crate (but the
 316     /// path will begin with the path to the external crate).
 317     pub fn def_path(&self, id: LocalDefId) -> DefPath {
 318         DefPath::make(LOCAL_CRATE, id.local_def_index, |index| {
 319             self.def_key(LocalDefId { local_def_index: index })
 320         })
 321     }
 322
 323     #[inline]
 324     pub fn opt_local_def_id(&self, node: ast::NodeId) -> Option<LocalDefId> {
 325         self.node_id_to_def_id.get(&node).copied()
 326     }
 327
 328     #[inline]
 329     pub fn local_def_id(&self, node: ast::NodeId) -> LocalDefId {
 330         self.opt_local_def_id(node).unwrap()
 331     }
 332
 333     #[inline]
 334     pub fn as_local_node_id(&self, def_id: DefId) -> Option<ast::NodeId> {
 335         if let Some(def_id) = def_id.as_local() {
 336             let node_id = self.def_id_to_node_id[def_id];
 337             if node_id != ast::DUMMY_NODE_ID {
 338                 return Some(node_id);
 339             }
 340         }
 341         None
 342     }
 343
 344     #[inline]
 345     pub fn as_local_hir_id(&self, def_id: DefId) -> Option<hir::HirId> {
 346         if let Some(def_id) = def_id.as_local() {
 347             Some(self.local_def_id_to_hir_id(def_id))
 348         } else {
 349             None
 350         }
 351     }
 352
 353     #[inline]
 354     pub fn hir_id_to_node_id(&self, hir_id: hir::HirId) -> ast::NodeId {
 355         self.hir_id_to_node_id[&hir_id]
 356     }
 357
 358     #[inline]
 359     pub fn node_id_to_hir_id(&self, node_id: ast::NodeId) -> hir::HirId {
 360         self.node_id_to_hir_id[node_id].unwrap()
 361     }
 362
 363     #[inline]
 364     pub fn opt_node_id_to_hir_id(&self, node_id: ast::NodeId) -> Option<hir::HirId> {
 365         self.node_id_to_hir_id[node_id]
 366     }
 367
 368     #[inline]
 369     pub fn local_def_id_to_hir_id(&self, id: LocalDefId) -> hir::HirId {
 370         let node_id = self.def_id_to_node_id[id];
 371         self.node_id_to_hir_id[node_id].unwrap()
 372     }
 373
 374     #[inline]
 375     pub fn opt_local_def_id_to_hir_id(&self, id: LocalDefId) -> Option<hir::HirId> {
 376         let node_id = self.def_id_to_node_id[id];
 377         self.node_id_to_hir_id[node_id]
 378     }
 379
 380     /// Retrieves the span of the given `DefId` if `DefId` is in the local crate.
 381     #[inline]
 382     pub fn opt_span(&self, def_id: DefId) -> Option<Span> {
 383         if let Some(def_id) = def_id.as_local() { Some(self.def_id_to_span[def_id]) } else { None }
 384     }
 385
 386     /// Adds a root definition (no parent) and a few other reserved definitions.
 387     pub fn create_root_def(
 388         &mut self,
 389         crate_name: &str,
 390         crate_disambiguator: CrateDisambiguator,
 391     ) -> LocalDefId {
 392         let key = DefKey {
 393             parent: None,
 394             disambiguated_data: DisambiguatedDefPathData {
 395                 data: DefPathData::CrateRoot,
 396                 disambiguator: 0,
 397             },
 398         };
 399
 400         let parent_hash = DefKey::root_parent_stable_hash(crate_name, crate_disambiguator);
 401         let def_path_hash = key.compute_stable_hash(parent_hash);
 402
 403         // Create the definition.
 404         let root = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };
 405         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
 406
 407         assert_eq!(self.def_id_to_node_id.push(ast::CRATE_NODE_ID), root);
 408         assert_eq!(self.def_id_to_span.push(rustc_span::DUMMY_SP), root);
 409
 410         self.node_id_to_def_id.insert(ast::CRATE_NODE_ID, root);
 411         self.set_invocation_parent(ExpnId::root(), root);
 412
 413         root
 414     }
 415
 416     /// Adds a definition with a parent definition.
 417     pub fn create_def_with_parent(
 418         &mut self,
 419         parent: LocalDefId,
 420         node_id: ast::NodeId,
 421         data: DefPathData,
 422         expn_id: ExpnId,
 423         span: Span,
 424     ) -> LocalDefId {
 425         debug!(
 426             "create_def_with_parent(parent={:?}, node_id={:?}, data={:?})",
 427             parent, node_id, data
 428         );
 429
 430         assert!(
 431             !self.node_id_to_def_id.contains_key(&node_id),
 432             "adding a def'n for node-id {:?} and data {:?} but a previous def'n exists: {:?}",
 433             node_id,
 434             data,
 435             self.table.def_key(self.node_id_to_def_id[&node_id].local_def_index),
 436         );
 437
 438         // The root node must be created with `create_root_def()`.
 439         assert!(data != DefPathData::CrateRoot);
 440
 441         // Find the next free disambiguator for this key.
 442         let disambiguator = {
 443             let next_disamb = self.next_disambiguator.entry((parent, data)).or_insert(0);
 444             let disambiguator = *next_disamb;
 445             *next_disamb = next_disamb.checked_add(1).expect("disambiguator overflow");
 446             disambiguator
 447         };
 448
 449         let key = DefKey {
 450             parent: Some(parent.local_def_index),
 451             disambiguated_data: DisambiguatedDefPathData { data, disambiguator },
 452         };
 453
 454         let parent_hash = self.table.def_path_hash(parent.local_def_index);
 455         let def_path_hash = key.compute_stable_hash(parent_hash);
 456
 457         debug!("create_def_with_parent: after disambiguation, key = {:?}", key);
 458
 459         // Create the definition.
 460         let def_id = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };
 461
 462         assert_eq!(self.def_id_to_node_id.push(node_id), def_id);
 463         assert_eq!(self.def_id_to_span.push(span), def_id);
 464
 465         // Some things for which we allocate `LocalDefId`s don't correspond to
 466         // anything in the AST, so they don't have a `NodeId`. For these cases
 467         // we don't need a mapping from `NodeId` to `LocalDefId`.
 468         if node_id != ast::DUMMY_NODE_ID {
 469             debug!("create_def_with_parent: def_id_to_node_id[{:?}] <-> {:?}", def_id, node_id);
 470             self.node_id_to_def_id.insert(node_id, def_id);
 471         }
 472
 473         if expn_id != ExpnId::root() {
 474             self.expansions_that_defined.insert(def_id, expn_id);
 475         }
 476
 477         def_id
 478     }
 479
 480     /// Initializes the `ast::NodeId` to `HirId` mapping once it has been generated during
 481     /// AST to HIR lowering.
 482     pub fn init_node_id_to_hir_id_mapping(
 483         &mut self,
 484         mapping: IndexVec<ast::NodeId, Option<hir::HirId>>,
 485     ) {
 486         assert!(
 487             self.node_id_to_hir_id.is_empty(),
 488             "trying to initialize `NodeId` -> `HirId` mapping twice"
 489         );
 490         self.node_id_to_hir_id = mapping;
 491
 492         // Build the reverse mapping of `node_id_to_hir_id`.
 493         self.hir_id_to_node_id = self
 494             .node_id_to_hir_id
 495             .iter_enumerated()
 496             .filter_map(|(node_id, &hir_id)| hir_id.map(|hir_id| (hir_id, node_id)))
 497             .collect();
 498     }
 499
 500     pub fn expansion_that_defined(&self, id: LocalDefId) -> ExpnId {
 501         self.expansions_that_defined.get(&id).copied().unwrap_or(ExpnId::root())
 502     }
 503
 504     pub fn parent_module_of_macro_def(&self, expn_id: ExpnId) -> DefId {
 505         self.parent_modules_of_macro_defs[&expn_id]
 506     }
 507
 508     pub fn add_parent_module_of_macro_def(&mut self, expn_id: ExpnId, module: DefId) {
 509         self.parent_modules_of_macro_defs.insert(expn_id, module);
 510     }
 511
 512     pub fn invocation_parent(&self, invoc_id: ExpnId) -> LocalDefId {
 513         self.invocation_parents[&invoc_id]
 514     }
 515
 516     pub fn set_invocation_parent(&mut self, invoc_id: ExpnId, parent: LocalDefId) {
 517         let old_parent = self.invocation_parents.insert(invoc_id, parent);
 518         assert!(old_parent.is_none(), "parent `LocalDefId` is reset for an invocation");
 519     }
 520
 521     pub fn placeholder_field_index(&self, node_id: ast::NodeId) -> usize {
 522         self.placeholder_field_indices[&node_id]
 523     }
 524
 525     pub fn set_placeholder_field_index(&mut self, node_id: ast::NodeId, index: usize) {
 526         let old_index = self.placeholder_field_indices.insert(node_id, index);
 527         assert!(old_index.is_none(), "placeholder field index is reset for a node ID");
 528     }
 529 }
 530
 531 impl DefPathData {
 532     pub fn get_opt_name(&self) -> Option<Symbol> {
 533         use self::DefPathData::*;
 534         match *self {
 535             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
 536
 537             Impl | CrateRoot | Misc | ClosureExpr | Ctor | AnonConst | ImplTrait => None,
 538         }
 539     }
 540
 541     pub fn as_symbol(&self) -> Symbol {
 542         use self::DefPathData::*;
 543         match *self {
 544             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => name,
 545             // Note that this does not show up in user print-outs.
 546             CrateRoot => sym::double_braced_crate,
 547             Impl => sym::double_braced_impl,
 548             Misc => sym::double_braced_misc,
 549             ClosureExpr => sym::double_braced_closure,
 550             Ctor => sym::double_braced_constructor,
 551             AnonConst => sym::double_braced_constant,
 552             ImplTrait => sym::double_braced_opaque,
 553         }
 554     }
 555
 556     pub fn to_string(&self) -> String {
 557         self.as_symbol().to_string()
 558     }
 559 }