compiler/rustc_hir/src/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, DefIndex, LocalDefId, StableCrateId, CRATE_DEF_INDEX, LOCAL_CRATE};
   9 use crate::def_path_hash_map::DefPathHashMap;
  10
  11 use rustc_data_structures::fx::FxHashMap;
  12 use rustc_data_structures::stable_hasher::StableHasher;
  13 use rustc_index::vec::IndexVec;
  14 use rustc_span::symbol::{kw, sym, Symbol};
  15
  16 use std::fmt::{self, Write};
  17 use std::hash::Hash;
  18
  19 /// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
  20 /// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`
  21 /// stores the `DefIndex` of its parent.
  22 /// There is one `DefPathTable` for each crate.
  23 #[derive(Clone, Default, Debug)]
  24 pub struct DefPathTable {
  25     index_to_key: IndexVec<DefIndex, DefKey>,
  26     def_path_hashes: IndexVec<DefIndex, DefPathHash>,
  27     def_path_hash_to_index: DefPathHashMap,
  28 }
  29
  30 impl DefPathTable {
  31     fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
  32         let index = {
  33             let index = DefIndex::from(self.index_to_key.len());
  34             debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
  35             self.index_to_key.push(key);
  36             index
  37         };
  38         self.def_path_hashes.push(def_path_hash);
  39         debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
  40
  41         // Check for hash collisions of DefPathHashes. These should be
  42         // exceedingly rare.
  43         if let Some(existing) = self.def_path_hash_to_index.insert(&def_path_hash, &index) {
  44             let def_path1 = DefPath::make(LOCAL_CRATE, existing, |idx| self.def_key(idx));
  45             let def_path2 = DefPath::make(LOCAL_CRATE, index, |idx| self.def_key(idx));
  46
  47             // Continuing with colliding DefPathHashes can lead to correctness
  48             // issues. We must abort compilation.
  49             //
  50             // The likelihood of such a collision is very small, so actually
  51             // running into one could be indicative of a poor hash function
  52             // being used.
  53             //
  54             // See the documentation for DefPathHash for more information.
  55             panic!(
  56                 "found DefPathHash collision between {:?} and {:?}. \
  57                     Compilation cannot continue.",
  58                 def_path1, def_path2
  59             );
  60         }
  61
  62         // Assert that all DefPathHashes correctly contain the local crate's
  63         // StableCrateId
  64         #[cfg(debug_assertions)]
  65         if let Some(root) = self.def_path_hashes.get(CRATE_DEF_INDEX) {
  66             assert!(def_path_hash.stable_crate_id() == root.stable_crate_id());
  67         }
  68
  69         index
  70     }
  71
  72     #[inline(always)]
  73     pub fn def_key(&self, index: DefIndex) -> DefKey {
  74         self.index_to_key[index]
  75     }
  76
  77     #[inline(always)]
  78     pub fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
  79         let hash = self.def_path_hashes[index];
  80         debug!("def_path_hash({:?}) = {:?}", index, hash);
  81         hash
  82     }
  83
  84     pub fn enumerated_keys_and_path_hashes(
  85         &self,
  86     ) -> impl Iterator<Item = (DefIndex, &DefKey, &DefPathHash)> + ExactSizeIterator + '_ {
  87         self.index_to_key
  88             .iter_enumerated()
  89             .map(move |(index, key)| (index, key, &self.def_path_hashes[index]))
  90     }
  91 }
  92
  93 /// The definition table containing node definitions.
  94 /// It holds the `DefPathTable` for `LocalDefId`s/`DefPath`s.
  95 /// It also stores mappings to convert `LocalDefId`s to/from `HirId`s.
  96 #[derive(Clone, Debug)]
  97 pub struct Definitions {
  98     table: DefPathTable,
  99     next_disambiguator: FxHashMap<(LocalDefId, DefPathData), u32>,
 100
 101     /// The [StableCrateId] of the local crate.
 102     stable_crate_id: StableCrateId,
 103 }
 104
 105 /// A unique identifier that we can use to lookup a definition
 106 /// precisely. It combines the index of the definition's parent (if
 107 /// any) with a `DisambiguatedDefPathData`.
 108 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 109 pub struct DefKey {
 110     /// The parent path.
 111     pub parent: Option<DefIndex>,
 112
 113     /// The identifier of this node.
 114     pub disambiguated_data: DisambiguatedDefPathData,
 115 }
 116
 117 impl DefKey {
 118     pub(crate) fn compute_stable_hash(&self, parent: DefPathHash) -> DefPathHash {
 119         let mut hasher = StableHasher::new();
 120
 121         parent.hash(&mut hasher);
 122
 123         let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;
 124
 125         std::mem::discriminant(data).hash(&mut hasher);
 126         if let Some(name) = data.get_opt_name() {
 127             // Get a stable hash by considering the symbol chars rather than
 128             // the symbol index.
 129             name.as_str().hash(&mut hasher);
 130         }
 131
 132         disambiguator.hash(&mut hasher);
 133
 134         let local_hash: u64 = hasher.finish();
 135
 136         // Construct the new DefPathHash, making sure that the `crate_id`
 137         // portion of the hash is properly copied from the parent. This way the
 138         // `crate_id` part will be recursively propagated from the root to all
 139         // DefPathHashes in this DefPathTable.
 140         DefPathHash::new(parent.stable_crate_id(), local_hash)
 141     }
 142
 143     #[inline]
 144     pub fn get_opt_name(&self) -> Option<Symbol> {
 145         self.disambiguated_data.data.get_opt_name()
 146     }
 147 }
 148
 149 /// A pair of `DefPathData` and an integer disambiguator. The integer is
 150 /// normally `0`, but in the event that there are multiple defs with the
 151 /// same `parent` and `data`, we use this field to disambiguate
 152 /// between them. This introduces some artificial ordering dependency
 153 /// but means that if you have, e.g., two impls for the same type in
 154 /// the same module, they do get distinct `DefId`s.
 155 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 156 pub struct DisambiguatedDefPathData {
 157     pub data: DefPathData,
 158     pub disambiguator: u32,
 159 }
 160
 161 impl DisambiguatedDefPathData {
 162     pub fn fmt_maybe_verbose(&self, writer: &mut impl Write, verbose: bool) -> fmt::Result {
 163         match self.data.name() {
 164             DefPathDataName::Named(name) => {
 165                 if verbose && self.disambiguator != 0 {
 166                     write!(writer, "{}#{}", name, self.disambiguator)
 167                 } else {
 168                     writer.write_str(name.as_str())
 169                 }
 170             }
 171             DefPathDataName::Anon { namespace } => {
 172                 write!(writer, "{{{}#{}}}", namespace, self.disambiguator)
 173             }
 174         }
 175     }
 176 }
 177
 178 impl fmt::Display for DisambiguatedDefPathData {
 179     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 180         self.fmt_maybe_verbose(f, true)
 181     }
 182 }
 183
 184 #[derive(Clone, Debug, Encodable, Decodable)]
 185 pub struct DefPath {
 186     /// The path leading from the crate root to the item.
 187     pub data: Vec<DisambiguatedDefPathData>,
 188
 189     /// The crate root this path is relative to.
 190     pub krate: CrateNum,
 191 }
 192
 193 impl DefPath {
 194     pub fn make<FN>(krate: CrateNum, start_index: DefIndex, mut get_key: FN) -> DefPath
 195     where
 196         FN: FnMut(DefIndex) -> DefKey,
 197     {
 198         let mut data = vec![];
 199         let mut index = Some(start_index);
 200         loop {
 201             debug!("DefPath::make: krate={:?} index={:?}", krate, index);
 202             let p = index.unwrap();
 203             let key = get_key(p);
 204             debug!("DefPath::make: key={:?}", key);
 205             match key.disambiguated_data.data {
 206                 DefPathData::CrateRoot => {
 207                     assert!(key.parent.is_none());
 208                     break;
 209                 }
 210                 _ => {
 211                     data.push(key.disambiguated_data);
 212                     index = key.parent;
 213                 }
 214             }
 215         }
 216         data.reverse();
 217         DefPath { data, krate }
 218     }
 219
 220     /// Returns a string representation of the `DefPath` without
 221     /// the crate-prefix. This method is useful if you don't have
 222     /// a `TyCtxt` available.
 223     pub fn to_string_no_crate_verbose(&self) -> String {
 224         let mut s = String::with_capacity(self.data.len() * 16);
 225
 226         for component in &self.data {
 227             write!(s, "::{}", component).unwrap();
 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             write!(s, "{}", component).unwrap();
 244         }
 245
 246         s
 247     }
 248 }
 249
 250 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
 251 pub enum DefPathData {
 252     // Root: these should only be used for the root nodes, because
 253     // they are treated specially by the `def_path` function.
 254     /// The crate root (marker).
 255     CrateRoot,
 256
 257     // Different kinds of items and item-like things:
 258     /// An impl.
 259     Impl,
 260     /// An `extern` block.
 261     ForeignMod,
 262     /// A `use` item.
 263     Use,
 264     /// A global asm item.
 265     GlobalAsm,
 266     /// Something in the type namespace.
 267     TypeNs(Symbol),
 268     /// Something in the value namespace.
 269     ValueNs(Symbol),
 270     /// Something in the macro namespace.
 271     MacroNs(Symbol),
 272     /// Something in the lifetime namespace.
 273     LifetimeNs(Symbol),
 274     /// A closure expression.
 275     ClosureExpr,
 276
 277     // Subportions of items:
 278     /// Implicit constructor for a unit or tuple-like struct or enum variant.
 279     Ctor,
 280     /// A constant expression (see `{ast,hir}::AnonConst`).
 281     AnonConst,
 282     /// An `impl Trait` type node.
 283     ImplTrait,
 284 }
 285
 286 impl Definitions {
 287     pub fn def_path_table(&self) -> &DefPathTable {
 288         &self.table
 289     }
 290
 291     /// Gets the number of definitions.
 292     pub fn def_index_count(&self) -> usize {
 293         self.table.index_to_key.len()
 294     }
 295
 296     #[inline]
 297     pub fn def_key(&self, id: LocalDefId) -> DefKey {
 298         self.table.def_key(id.local_def_index)
 299     }
 300
 301     #[inline(always)]
 302     pub fn def_path_hash(&self, id: LocalDefId) -> DefPathHash {
 303         self.table.def_path_hash(id.local_def_index)
 304     }
 305
 306     /// Returns the path from the crate root to `index`. The root
 307     /// nodes are not included in the path (i.e., this will be an
 308     /// empty vector for the crate root). For an inlined item, this
 309     /// will be the path of the item in the external crate (but the
 310     /// path will begin with the path to the external crate).
 311     pub fn def_path(&self, id: LocalDefId) -> DefPath {
 312         DefPath::make(LOCAL_CRATE, id.local_def_index, |index| {
 313             self.def_key(LocalDefId { local_def_index: index })
 314         })
 315     }
 316
 317     /// Adds a root definition (no parent) and a few other reserved definitions.
 318     pub fn new(stable_crate_id: StableCrateId) -> Definitions {
 319         let key = DefKey {
 320             parent: None,
 321             disambiguated_data: DisambiguatedDefPathData {
 322                 data: DefPathData::CrateRoot,
 323                 disambiguator: 0,
 324             },
 325         };
 326
 327         let parent_hash = DefPathHash::new(stable_crate_id, 0);
 328         let def_path_hash = key.compute_stable_hash(parent_hash);
 329
 330         // Create the root definition.
 331         let mut table = DefPathTable::default();
 332         let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
 333         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
 334
 335         Definitions { table, next_disambiguator: Default::default(), stable_crate_id }
 336     }
 337
 338     /// Adds a definition with a parent definition.
 339     pub fn create_def(&mut self, parent: LocalDefId, data: DefPathData) -> LocalDefId {
 340         // We can't use `Debug` implementation for `LocalDefId` here, since it tries to acquire a
 341         // reference to `Definitions` and we're already holding a mutable reference.
 342         debug!(
 343             "create_def(parent={}, data={data:?})",
 344             self.def_path(parent).to_string_no_crate_verbose(),
 345         );
 346
 347         // The root node must be created with `create_root_def()`.
 348         assert!(data != DefPathData::CrateRoot);
 349
 350         // Find the next free disambiguator for this key.
 351         let disambiguator = {
 352             let next_disamb = self.next_disambiguator.entry((parent, data)).or_insert(0);
 353             let disambiguator = *next_disamb;
 354             *next_disamb = next_disamb.checked_add(1).expect("disambiguator overflow");
 355             disambiguator
 356         };
 357         let key = DefKey {
 358             parent: Some(parent.local_def_index),
 359             disambiguated_data: DisambiguatedDefPathData { data, disambiguator },
 360         };
 361
 362         let parent_hash = self.table.def_path_hash(parent.local_def_index);
 363         let def_path_hash = key.compute_stable_hash(parent_hash);
 364
 365         debug!("create_def: after disambiguation, key = {:?}", key);
 366
 367         // Create the definition.
 368         LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) }
 369     }
 370
 371     pub fn iter_local_def_id(&self) -> impl Iterator<Item = LocalDefId> + '_ {
 372         self.table.def_path_hashes.indices().map(|local_def_index| LocalDefId { local_def_index })
 373     }
 374
 375     #[inline(always)]
 376     pub fn local_def_path_hash_to_def_id(
 377         &self,
 378         hash: DefPathHash,
 379         err: &mut dyn FnMut() -> !,
 380     ) -> LocalDefId {
 381         debug_assert!(hash.stable_crate_id() == self.stable_crate_id);
 382         self.table
 383             .def_path_hash_to_index
 384             .get(&hash)
 385             .map(|local_def_index| LocalDefId { local_def_index })
 386             .unwrap_or_else(|| err())
 387     }
 388
 389     pub fn def_path_hash_to_def_index_map(&self) -> &DefPathHashMap {
 390         &self.table.def_path_hash_to_index
 391     }
 392 }
 393
 394 #[derive(Copy, Clone, PartialEq, Debug)]
 395 pub enum DefPathDataName {
 396     Named(Symbol),
 397     Anon { namespace: Symbol },
 398 }
 399
 400 impl DefPathData {
 401     pub fn get_opt_name(&self) -> Option<Symbol> {
 402         use self::DefPathData::*;
 403         match *self {
 404             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
 405
 406             Impl | ForeignMod | CrateRoot | Use | GlobalAsm | ClosureExpr | Ctor | AnonConst
 407             | ImplTrait => None,
 408         }
 409     }
 410
 411     pub fn name(&self) -> DefPathDataName {
 412         use self::DefPathData::*;
 413         match *self {
 414             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => {
 415                 DefPathDataName::Named(name)
 416             }
 417             // Note that this does not show up in user print-outs.
 418             CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
 419             Impl => DefPathDataName::Anon { namespace: kw::Impl },
 420             ForeignMod => DefPathDataName::Anon { namespace: kw::Extern },
 421             Use => DefPathDataName::Anon { namespace: kw::Use },
 422             GlobalAsm => DefPathDataName::Anon { namespace: sym::global_asm },
 423             ClosureExpr => DefPathDataName::Anon { namespace: sym::closure },
 424             Ctor => DefPathDataName::Anon { namespace: sym::constructor },
 425             AnonConst => DefPathDataName::Anon { namespace: sym::constant },
 426             ImplTrait => DefPathDataName::Anon { namespace: sym::opaque },
 427         }
 428     }
 429 }
 430
 431 impl fmt::Display for DefPathData {
 432     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 433         match self.name() {
 434             DefPathDataName::Named(name) => f.write_str(name.as_str()),
 435             // FIXME(#70334): this will generate legacy {{closure}}, {{impl}}, etc
 436             DefPathDataName::Anon { namespace } => write!(f, "{{{{{}}}}}", namespace),
 437         }
 438     }
 439 }