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::crate_disambiguator::CrateDisambiguator;
  12 use rustc_data_structures::fx::FxHashMap;
  13 use rustc_data_structures::stable_hasher::StableHasher;
  14 use rustc_index::vec::IndexVec;
  15 use rustc_span::hygiene::ExpnId;
  16 use rustc_span::symbol::{sym, Symbol};
  17
  18 use std::fmt::Write;
  19 use std::hash::Hash;
  20 use tracing::debug;
  21
  22 /// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
  23 /// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`
  24 /// stores the `DefIndex` of its parent.
  25 /// There is one `DefPathTable` for each crate.
  26 #[derive(Clone, Default)]
  27 pub struct DefPathTable {
  28     index_to_key: IndexVec<DefIndex, DefKey>,
  29     def_path_hashes: IndexVec<DefIndex, DefPathHash>,
  30 }
  31
  32 impl DefPathTable {
  33     fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
  34         let index = {
  35             let index = DefIndex::from(self.index_to_key.len());
  36             debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
  37             self.index_to_key.push(key);
  38             index
  39         };
  40         self.def_path_hashes.push(def_path_hash);
  41         debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
  42         index
  43     }
  44
  45     #[inline(always)]
  46     pub fn def_key(&self, index: DefIndex) -> DefKey {
  47         self.index_to_key[index]
  48     }
  49
  50     #[inline(always)]
  51     pub fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
  52         let hash = self.def_path_hashes[index];
  53         debug!("def_path_hash({:?}) = {:?}", index, hash);
  54         hash
  55     }
  56
  57     pub fn num_def_ids(&self) -> usize {
  58         self.index_to_key.len()
  59     }
  60
  61     pub fn enumerated_keys_and_path_hashes(
  62         &self,
  63     ) -> impl Iterator<Item = (DefIndex, &DefKey, &DefPathHash)> + '_ {
  64         self.index_to_key
  65             .iter_enumerated()
  66             .map(move |(index, key)| (index, key, &self.def_path_hashes[index]))
  67     }
  68
  69     pub fn all_def_path_hashes_and_def_ids(
  70         &self,
  71         krate: CrateNum,
  72     ) -> impl Iterator<Item = (DefPathHash, DefId)> + '_ {
  73         self.def_path_hashes
  74             .iter_enumerated()
  75             .map(move |(index, hash)| (*hash, DefId { krate, index }))
  76     }
  77 }
  78
  79 /// The definition table containing node definitions.
  80 /// It holds the `DefPathTable` for `LocalDefId`s/`DefPath`s.
  81 /// It also stores mappings to convert `LocalDefId`s to/from `HirId`s.
  82 #[derive(Clone)]
  83 pub struct Definitions {
  84     table: DefPathTable,
  85
  86     // FIXME(eddyb) ideally all `LocalDefId`s would be HIR owners.
  87     pub(super) def_id_to_hir_id: IndexVec<LocalDefId, Option<hir::HirId>>,
  88     /// The reverse mapping of `def_id_to_hir_id`.
  89     pub(super) hir_id_to_def_id: FxHashMap<hir::HirId, LocalDefId>,
  90
  91     /// If `ExpnId` is an ID of some macro expansion,
  92     /// then `DefId` is the normal module (`mod`) in which the expanded macro was defined.
  93     parent_modules_of_macro_defs: FxHashMap<ExpnId, DefId>,
  94     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
  95     expansions_that_defined: FxHashMap<LocalDefId, ExpnId>,
  96 }
  97
  98 /// A unique identifier that we can use to lookup a definition
  99 /// precisely. It combines the index of the definition's parent (if
 100 /// any) with a `DisambiguatedDefPathData`.
 101 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 102 pub struct DefKey {
 103     /// The parent path.
 104     pub parent: Option<DefIndex>,
 105
 106     /// The identifier of this node.
 107     pub disambiguated_data: DisambiguatedDefPathData,
 108 }
 109
 110 impl DefKey {
 111     fn compute_stable_hash(&self, parent_hash: DefPathHash) -> DefPathHash {
 112         let mut hasher = StableHasher::new();
 113
 114         // We hash a `0u8` here to disambiguate between regular `DefPath` hashes,
 115         // and the special "root_parent" below.
 116         0u8.hash(&mut hasher);
 117         parent_hash.hash(&mut hasher);
 118
 119         let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;
 120
 121         ::std::mem::discriminant(data).hash(&mut hasher);
 122         if let Some(name) = data.get_opt_name() {
 123             // Get a stable hash by considering the symbol chars rather than
 124             // the symbol index.
 125             name.as_str().hash(&mut hasher);
 126         }
 127
 128         disambiguator.hash(&mut hasher);
 129
 130         DefPathHash(hasher.finish())
 131     }
 132
 133     fn root_parent_stable_hash(
 134         crate_name: &str,
 135         crate_disambiguator: CrateDisambiguator,
 136     ) -> DefPathHash {
 137         let mut hasher = StableHasher::new();
 138         // Disambiguate this from a regular `DefPath` hash; see `compute_stable_hash()` above.
 139         1u8.hash(&mut hasher);
 140         crate_name.hash(&mut hasher);
 141         crate_disambiguator.hash(&mut hasher);
 142         DefPathHash(hasher.finish())
 143     }
 144 }
 145
 146 /// A pair of `DefPathData` and an integer disambiguator. The integer is
 147 /// normally `0`, but in the event that there are multiple defs with the
 148 /// same `parent` and `data`, we use this field to disambiguate
 149 /// between them. This introduces some artificial ordering dependency
 150 /// but means that if you have, e.g., two impls for the same type in
 151 /// the same module, they do get distinct `DefId`s.
 152 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 153 pub struct DisambiguatedDefPathData {
 154     pub data: DefPathData,
 155     pub disambiguator: u32,
 156 }
 157
 158 #[derive(Clone, Debug, Encodable, Decodable)]
 159 pub struct DefPath {
 160     /// The path leading from the crate root to the item.
 161     pub data: Vec<DisambiguatedDefPathData>,
 162
 163     /// The crate root this path is relative to.
 164     pub krate: CrateNum,
 165 }
 166
 167 impl DefPath {
 168     pub fn is_local(&self) -> bool {
 169         self.krate == LOCAL_CRATE
 170     }
 171
 172     pub fn make<FN>(krate: CrateNum, start_index: DefIndex, mut get_key: FN) -> DefPath
 173     where
 174         FN: FnMut(DefIndex) -> DefKey,
 175     {
 176         let mut data = vec![];
 177         let mut index = Some(start_index);
 178         loop {
 179             debug!("DefPath::make: krate={:?} index={:?}", krate, index);
 180             let p = index.unwrap();
 181             let key = get_key(p);
 182             debug!("DefPath::make: key={:?}", key);
 183             match key.disambiguated_data.data {
 184                 DefPathData::CrateRoot => {
 185                     assert!(key.parent.is_none());
 186                     break;
 187                 }
 188                 _ => {
 189                     data.push(key.disambiguated_data);
 190                     index = key.parent;
 191                 }
 192             }
 193         }
 194         data.reverse();
 195         DefPath { data, krate }
 196     }
 197
 198     /// Returns a string representation of the `DefPath` without
 199     /// the crate-prefix. This method is useful if you don't have
 200     /// a `TyCtxt` available.
 201     pub fn to_string_no_crate(&self) -> String {
 202         let mut s = String::with_capacity(self.data.len() * 16);
 203
 204         for component in &self.data {
 205             write!(s, "::{}[{}]", component.data.as_symbol(), component.disambiguator).unwrap();
 206         }
 207
 208         s
 209     }
 210
 211     /// Returns a filename-friendly string for the `DefPath`, with the
 212     /// crate-prefix.
 213     pub fn to_string_friendly<F>(&self, crate_imported_name: F) -> String
 214     where
 215         F: FnOnce(CrateNum) -> Symbol,
 216     {
 217         let crate_name_str = crate_imported_name(self.krate).as_str();
 218         let mut s = String::with_capacity(crate_name_str.len() + self.data.len() * 16);
 219
 220         write!(s, "::{}", crate_name_str).unwrap();
 221
 222         for component in &self.data {
 223             if component.disambiguator == 0 {
 224                 write!(s, "::{}", component.data.as_symbol()).unwrap();
 225             } else {
 226                 write!(s, "{}[{}]", component.data.as_symbol(), component.disambiguator).unwrap();
 227             }
 228         }
 229
 230         s
 231     }
 232
 233     /// Returns a filename-friendly string of the `DefPath`, without
 234     /// the crate-prefix. This method is useful if you don't have
 235     /// a `TyCtxt` available.
 236     pub fn to_filename_friendly_no_crate(&self) -> String {
 237         let mut s = String::with_capacity(self.data.len() * 16);
 238
 239         let mut opt_delimiter = None;
 240         for component in &self.data {
 241             s.extend(opt_delimiter);
 242             opt_delimiter = Some('-');
 243             if component.disambiguator == 0 {
 244                 write!(s, "{}", component.data.as_symbol()).unwrap();
 245             } else {
 246                 write!(s, "{}[{}]", component.data.as_symbol(), component.disambiguator).unwrap();
 247             }
 248         }
 249         s
 250     }
 251 }
 252
 253 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
 254 pub enum DefPathData {
 255     // Root: these should only be used for the root nodes, because
 256     // they are treated specially by the `def_path` function.
 257     /// The crate root (marker).
 258     CrateRoot,
 259     // Catch-all for random `DefId` things like `DUMMY_NODE_ID`.
 260     Misc,
 261
 262     // Different kinds of items and item-like things:
 263     /// An impl.
 264     Impl,
 265     /// Something in the type namespace.
 266     TypeNs(Symbol),
 267     /// Something in the value namespace.
 268     ValueNs(Symbol),
 269     /// Something in the macro namespace.
 270     MacroNs(Symbol),
 271     /// Something in the lifetime namespace.
 272     LifetimeNs(Symbol),
 273     /// A closure expression.
 274     ClosureExpr,
 275
 276     // Subportions of items:
 277     /// Implicit constructor for a unit or tuple-like struct or enum variant.
 278     Ctor,
 279     /// A constant expression (see `{ast,hir}::AnonConst`).
 280     AnonConst,
 281     /// An `impl Trait` type node.
 282     ImplTrait,
 283 }
 284
 285 impl Definitions {
 286     pub fn def_path_table(&self) -> &DefPathTable {
 287         &self.table
 288     }
 289
 290     /// Gets the number of definitions.
 291     pub fn def_index_count(&self) -> usize {
 292         self.table.index_to_key.len()
 293     }
 294
 295     pub fn def_key(&self, id: LocalDefId) -> DefKey {
 296         self.table.def_key(id.local_def_index)
 297     }
 298
 299     #[inline(always)]
 300     pub fn def_path_hash(&self, id: LocalDefId) -> DefPathHash {
 301         self.table.def_path_hash(id.local_def_index)
 302     }
 303
 304     /// Returns the path from the crate root to `index`. The root
 305     /// nodes are not included in the path (i.e., this will be an
 306     /// empty vector for the crate root). For an inlined item, this
 307     /// will be the path of the item in the external crate (but the
 308     /// path will begin with the path to the external crate).
 309     pub fn def_path(&self, id: LocalDefId) -> DefPath {
 310         DefPath::make(LOCAL_CRATE, id.local_def_index, |index| {
 311             self.def_key(LocalDefId { local_def_index: index })
 312         })
 313     }
 314
 315     #[inline]
 316     pub fn local_def_id_to_hir_id(&self, id: LocalDefId) -> hir::HirId {
 317         self.def_id_to_hir_id[id].unwrap()
 318     }
 319
 320     #[inline]
 321     pub fn opt_local_def_id_to_hir_id(&self, id: LocalDefId) -> Option<hir::HirId> {
 322         self.def_id_to_hir_id[id]
 323     }
 324
 325     #[inline]
 326     pub fn opt_hir_id_to_local_def_id(&self, hir_id: hir::HirId) -> Option<LocalDefId> {
 327         self.hir_id_to_def_id.get(&hir_id).copied()
 328     }
 329
 330     /// Adds a root definition (no parent) and a few other reserved definitions.
 331     pub fn new(crate_name: &str, crate_disambiguator: CrateDisambiguator) -> Definitions {
 332         let key = DefKey {
 333             parent: None,
 334             disambiguated_data: DisambiguatedDefPathData {
 335                 data: DefPathData::CrateRoot,
 336                 disambiguator: 0,
 337             },
 338         };
 339
 340         let parent_hash = DefKey::root_parent_stable_hash(crate_name, crate_disambiguator);
 341         let def_path_hash = key.compute_stable_hash(parent_hash);
 342
 343         // Create the root definition.
 344         let mut table = DefPathTable::default();
 345         let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
 346         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
 347
 348         Definitions {
 349             table,
 350             def_id_to_hir_id: Default::default(),
 351             hir_id_to_def_id: Default::default(),
 352             expansions_that_defined: Default::default(),
 353             parent_modules_of_macro_defs: Default::default(),
 354         }
 355     }
 356
 357     /// Retrieves the root definition.
 358     pub fn get_root_def(&self) -> LocalDefId {
 359         LocalDefId { local_def_index: CRATE_DEF_INDEX }
 360     }
 361
 362     /// Adds a definition with a parent definition.
 363     pub fn create_def(
 364         &mut self,
 365         parent: LocalDefId,
 366         data: DefPathData,
 367         expn_id: ExpnId,
 368         mut next_disambiguator: impl FnMut(LocalDefId, DefPathData) -> u32,
 369     ) -> LocalDefId {
 370         debug!("create_def(parent={:?}, data={:?}, expn_id={:?})", parent, data, expn_id);
 371
 372         // The root node must be created with `create_root_def()`.
 373         assert!(data != DefPathData::CrateRoot);
 374
 375         let disambiguator = next_disambiguator(parent, data);
 376         let key = DefKey {
 377             parent: Some(parent.local_def_index),
 378             disambiguated_data: DisambiguatedDefPathData { data, disambiguator },
 379         };
 380
 381         let parent_hash = self.table.def_path_hash(parent.local_def_index);
 382         let def_path_hash = key.compute_stable_hash(parent_hash);
 383
 384         debug!("create_def: after disambiguation, key = {:?}", key);
 385
 386         // Create the definition.
 387         let def_id = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };
 388
 389         if expn_id != ExpnId::root() {
 390             self.expansions_that_defined.insert(def_id, expn_id);
 391         }
 392
 393         def_id
 394     }
 395
 396     /// Initializes the `LocalDefId` to `HirId` mapping once it has been generated during
 397     /// AST to HIR lowering.
 398     pub fn init_def_id_to_hir_id_mapping(
 399         &mut self,
 400         mapping: IndexVec<LocalDefId, Option<hir::HirId>>,
 401     ) {
 402         assert!(
 403             self.def_id_to_hir_id.is_empty(),
 404             "trying to initialize `LocalDefId` <-> `HirId` mappings twice"
 405         );
 406
 407         // Build the reverse mapping of `def_id_to_hir_id`.
 408         self.hir_id_to_def_id = mapping
 409             .iter_enumerated()
 410             .filter_map(|(def_id, hir_id)| hir_id.map(|hir_id| (hir_id, def_id)))
 411             .collect();
 412
 413         self.def_id_to_hir_id = mapping;
 414     }
 415
 416     pub fn expansion_that_defined(&self, id: LocalDefId) -> ExpnId {
 417         self.expansions_that_defined.get(&id).copied().unwrap_or(ExpnId::root())
 418     }
 419
 420     pub fn parent_module_of_macro_def(&self, expn_id: ExpnId) -> DefId {
 421         self.parent_modules_of_macro_defs[&expn_id]
 422     }
 423
 424     pub fn add_parent_module_of_macro_def(&mut self, expn_id: ExpnId, module: DefId) {
 425         self.parent_modules_of_macro_defs.insert(expn_id, module);
 426     }
 427 }
 428
 429 impl DefPathData {
 430     pub fn get_opt_name(&self) -> Option<Symbol> {
 431         use self::DefPathData::*;
 432         match *self {
 433             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
 434
 435             Impl | CrateRoot | Misc | ClosureExpr | Ctor | AnonConst | ImplTrait => None,
 436         }
 437     }
 438
 439     pub fn as_symbol(&self) -> Symbol {
 440         use self::DefPathData::*;
 441         match *self {
 442             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => name,
 443             // Note that this does not show up in user print-outs.
 444             CrateRoot => sym::double_braced_crate,
 445             Impl => sym::double_braced_impl,
 446             Misc => sym::double_braced_misc,
 447             ClosureExpr => sym::double_braced_closure,
 448             Ctor => sym::double_braced_constructor,
 449             AnonConst => sym::double_braced_constant,
 450             ImplTrait => sym::double_braced_opaque,
 451         }
 452     }
 453
 454     pub fn to_string(&self) -> String {
 455         self.as_symbol().to_string()
 456     }
 457 }