rustc_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
7use std::fmt::{self, Write};
8use std::hash::Hash;
9
10use rustc_data_structures::stable_hasher::StableHasher;
11use rustc_data_structures::unord::UnordMap;
12use rustc_hashes::Hash64;
13use rustc_index::IndexVec;
14use rustc_macros::{Decodable, Encodable};
15use rustc_span::{Symbol, kw, sym};
16use tracing::{debug, instrument};
17
18pub use crate::def_id::DefPathHash;
19use crate::def_id::{CRATE_DEF_INDEX, CrateNum, DefIndex, LOCAL_CRATE, LocalDefId, StableCrateId};
20use crate::def_path_hash_map::DefPathHashMap;
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(Debug)]
27pub struct DefPathTable {
28    stable_crate_id: StableCrateId,
29    index_to_key: IndexVec<DefIndex, DefKey>,
30    // We do only store the local hash, as all the definitions are from the current crate.
31    def_path_hashes: IndexVec<DefIndex, Hash64>,
32    def_path_hash_to_index: DefPathHashMap,
33}
34
35impl DefPathTable {
36    fn new(stable_crate_id: StableCrateId) -> DefPathTable {
37        DefPathTable {
38            stable_crate_id,
39            index_to_key: Default::default(),
40            def_path_hashes: Default::default(),
41            def_path_hash_to_index: Default::default(),
42        }
43    }
44
45    fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
46        // Assert that all DefPathHashes correctly contain the local crate's StableCrateId.
47        debug_assert_eq!(self.stable_crate_id, def_path_hash.stable_crate_id());
48        let local_hash = def_path_hash.local_hash();
49
50        let index = self.index_to_key.push(key);
51        debug!("DefPathTable::insert() - {key:?} <-> {index:?}");
52
53        self.def_path_hashes.push(local_hash);
54        debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
55
56        // Check for hash collisions of DefPathHashes. These should be
57        // exceedingly rare.
58        if let Some(existing) = self.def_path_hash_to_index.insert(&local_hash, &index) {
59            let def_path1 = DefPath::make(LOCAL_CRATE, existing, |idx| self.def_key(idx));
60            let def_path2 = DefPath::make(LOCAL_CRATE, index, |idx| self.def_key(idx));
61
62            // Continuing with colliding DefPathHashes can lead to correctness
63            // issues. We must abort compilation.
64            //
65            // The likelihood of such a collision is very small, so actually
66            // running into one could be indicative of a poor hash function
67            // being used.
68            //
69            // See the documentation for DefPathHash for more information.
70            panic!(
71                "found DefPathHash collision between {def_path1:#?} and {def_path2:#?}. \
72                    Compilation cannot continue."
73            );
74        }
75
76        index
77    }
78
79    #[inline(always)]
80    pub fn def_key(&self, index: DefIndex) -> DefKey {
81        self.index_to_key[index]
82    }
83
84    #[instrument(level = "trace", skip(self), ret)]
85    #[inline(always)]
86    pub fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
87        let hash = self.def_path_hashes[index];
88        DefPathHash::new(self.stable_crate_id, hash)
89    }
90
91    pub fn enumerated_keys_and_path_hashes(
92        &self,
93    ) -> impl Iterator<Item = (DefIndex, &DefKey, DefPathHash)> + ExactSizeIterator {
94        self.index_to_key
95            .iter_enumerated()
96            .map(move |(index, key)| (index, key, self.def_path_hash(index)))
97    }
98}
99
100#[derive(Debug)]
101pub struct DisambiguatorState {
102    next: UnordMap<(LocalDefId, DefPathData), u32>,
103}
104
105impl DisambiguatorState {
106    pub fn new() -> Self {
107        Self { next: Default::default() }
108    }
109
110    /// Creates a `DisambiguatorState` where the next allocated `(LocalDefId, DefPathData)` pair
111    /// will have `index` as the disambiguator.
112    pub fn with(def_id: LocalDefId, data: DefPathData, index: u32) -> Self {
113        let mut this = Self::new();
114        this.next.insert((def_id, data), index);
115        this
116    }
117}
118
119/// The definition table containing node definitions.
120/// It holds the `DefPathTable` for `LocalDefId`s/`DefPath`s.
121/// It also stores mappings to convert `LocalDefId`s to/from `HirId`s.
122#[derive(Debug)]
123pub struct Definitions {
124    table: DefPathTable,
125}
126
127/// A unique identifier that we can use to lookup a definition
128/// precisely. It combines the index of the definition's parent (if
129/// any) with a `DisambiguatedDefPathData`.
130#[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
131pub struct DefKey {
132    /// The parent path.
133    pub parent: Option<DefIndex>,
134
135    /// The identifier of this node.
136    pub disambiguated_data: DisambiguatedDefPathData,
137}
138
139impl DefKey {
140    pub(crate) fn compute_stable_hash(&self, parent: DefPathHash) -> DefPathHash {
141        let mut hasher = StableHasher::new();
142
143        parent.hash(&mut hasher);
144
145        let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;
146
147        std::mem::discriminant(data).hash(&mut hasher);
148        if let Some(name) = data.hashed_symbol() {
149            // Get a stable hash by considering the symbol chars rather than
150            // the symbol index.
151            name.as_str().hash(&mut hasher);
152        }
153
154        disambiguator.hash(&mut hasher);
155
156        let local_hash = hasher.finish();
157
158        // Construct the new DefPathHash, making sure that the `crate_id`
159        // portion of the hash is properly copied from the parent. This way the
160        // `crate_id` part will be recursively propagated from the root to all
161        // DefPathHashes in this DefPathTable.
162        DefPathHash::new(parent.stable_crate_id(), local_hash)
163    }
164
165    #[inline]
166    pub fn get_opt_name(&self) -> Option<Symbol> {
167        self.disambiguated_data.data.get_opt_name()
168    }
169}
170
171/// A pair of `DefPathData` and an integer disambiguator. The integer is
172/// normally `0`, but in the event that there are multiple defs with the
173/// same `parent` and `data`, we use this field to disambiguate
174/// between them. This introduces some artificial ordering dependency
175/// but means that if you have, e.g., two impls for the same type in
176/// the same module, they do get distinct `DefId`s.
177#[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
178pub struct DisambiguatedDefPathData {
179    pub data: DefPathData,
180    pub disambiguator: u32,
181}
182
183impl DisambiguatedDefPathData {
184    pub fn fmt_maybe_verbose(&self, writer: &mut impl Write, verbose: bool) -> fmt::Result {
185        match self.data.name() {
186            DefPathDataName::Named(name) => {
187                if verbose && self.disambiguator != 0 {
188                    write!(writer, "{}#{}", name, self.disambiguator)
189                } else {
190                    writer.write_str(name.as_str())
191                }
192            }
193            DefPathDataName::Anon { namespace } => {
194                if let DefPathData::AnonAssocTy(method) = self.data {
195                    write!(writer, "{}::{{{}#{}}}", method, namespace, self.disambiguator)
196                } else {
197                    write!(writer, "{{{}#{}}}", namespace, self.disambiguator)
198                }
199            }
200        }
201    }
202}
203
204impl fmt::Display for DisambiguatedDefPathData {
205    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
206        self.fmt_maybe_verbose(f, true)
207    }
208}
209
210#[derive(Clone, Debug, Encodable, Decodable)]
211pub struct DefPath {
212    /// The path leading from the crate root to the item.
213    pub data: Vec<DisambiguatedDefPathData>,
214
215    /// The crate root this path is relative to.
216    pub krate: CrateNum,
217}
218
219impl DefPath {
220    pub fn make<FN>(krate: CrateNum, start_index: DefIndex, mut get_key: FN) -> DefPath
221    where
222        FN: FnMut(DefIndex) -> DefKey,
223    {
224        let mut data = vec![];
225        let mut index = Some(start_index);
226        loop {
227            debug!("DefPath::make: krate={:?} index={:?}", krate, index);
228            let p = index.unwrap();
229            let key = get_key(p);
230            debug!("DefPath::make: key={:?}", key);
231            match key.disambiguated_data.data {
232                DefPathData::CrateRoot => {
233                    assert!(key.parent.is_none());
234                    break;
235                }
236                _ => {
237                    data.push(key.disambiguated_data);
238                    index = key.parent;
239                }
240            }
241        }
242        data.reverse();
243        DefPath { data, krate }
244    }
245
246    /// Returns a string representation of the `DefPath` without
247    /// the crate-prefix. This method is useful if you don't have
248    /// a `TyCtxt` available.
249    pub fn to_string_no_crate_verbose(&self) -> String {
250        let mut s = String::with_capacity(self.data.len() * 16);
251
252        for component in &self.data {
253            write!(s, "::{component}").unwrap();
254        }
255
256        s
257    }
258
259    /// Returns a filename-friendly string of the `DefPath`, without
260    /// the crate-prefix. This method is useful if you don't have
261    /// a `TyCtxt` available.
262    pub fn to_filename_friendly_no_crate(&self) -> String {
263        let mut s = String::with_capacity(self.data.len() * 16);
264
265        let mut opt_delimiter = None;
266        for component in &self.data {
267            s.extend(opt_delimiter);
268            opt_delimiter = Some('-');
269            write!(s, "{component}").unwrap();
270        }
271
272        s
273    }
274}
275
276/// New variants should only be added in synchronization with `enum DefKind`.
277#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
278pub enum DefPathData {
279    // Root: these should only be used for the root nodes, because
280    // they are treated specially by the `def_path` function.
281    /// The crate root (marker).
282    CrateRoot,
283
284    // Different kinds of items and item-like things:
285    /// An impl.
286    Impl,
287    /// An `extern` block.
288    ForeignMod,
289    /// A `use` item.
290    Use,
291    /// A global asm item.
292    GlobalAsm,
293    /// Something in the type namespace.
294    TypeNs(Symbol),
295    /// Something in the value namespace.
296    ValueNs(Symbol),
297    /// Something in the macro namespace.
298    MacroNs(Symbol),
299    /// Something in the lifetime namespace.
300    LifetimeNs(Symbol),
301    /// A closure expression.
302    Closure,
303
304    // Subportions of items:
305    /// Implicit constructor for a unit or tuple-like struct or enum variant.
306    Ctor,
307    /// A constant expression (see `{ast,hir}::AnonConst`).
308    AnonConst,
309    /// An existential `impl Trait` type node.
310    /// Argument position `impl Trait` have a `TypeNs` with their pretty-printed name.
311    OpaqueTy,
312    /// Used for remapped captured lifetimes in an existential `impl Trait` type node.
313    OpaqueLifetime(Symbol),
314    /// An anonymous associated type from an RPITIT. The symbol refers to the name of the method
315    /// that defined the type.
316    AnonAssocTy(Symbol),
317    /// A synthetic body for a coroutine's by-move body.
318    SyntheticCoroutineBody,
319    /// Additional static data referred to by a static.
320    NestedStatic,
321}
322
323impl Definitions {
324    pub fn def_path_table(&self) -> &DefPathTable {
325        &self.table
326    }
327
328    /// Gets the number of definitions.
329    pub fn def_index_count(&self) -> usize {
330        self.table.index_to_key.len()
331    }
332
333    #[inline]
334    pub fn def_key(&self, id: LocalDefId) -> DefKey {
335        self.table.def_key(id.local_def_index)
336    }
337
338    #[inline(always)]
339    pub fn def_path_hash(&self, id: LocalDefId) -> DefPathHash {
340        self.table.def_path_hash(id.local_def_index)
341    }
342
343    /// Returns the path from the crate root to `index`. The root
344    /// nodes are not included in the path (i.e., this will be an
345    /// empty vector for the crate root). For an inlined item, this
346    /// will be the path of the item in the external crate (but the
347    /// path will begin with the path to the external crate).
348    pub fn def_path(&self, id: LocalDefId) -> DefPath {
349        DefPath::make(LOCAL_CRATE, id.local_def_index, |index| {
350            self.def_key(LocalDefId { local_def_index: index })
351        })
352    }
353
354    /// Adds a root definition (no parent) and a few other reserved definitions.
355    pub fn new(stable_crate_id: StableCrateId) -> Definitions {
356        let key = DefKey {
357            parent: None,
358            disambiguated_data: DisambiguatedDefPathData {
359                data: DefPathData::CrateRoot,
360                disambiguator: 0,
361            },
362        };
363
364        let parent_hash = DefPathHash::new(stable_crate_id, Hash64::ZERO);
365        let def_path_hash = key.compute_stable_hash(parent_hash);
366
367        // Create the root definition.
368        let mut table = DefPathTable::new(stable_crate_id);
369        let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
370        assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
371
372        Definitions { table }
373    }
374
375    /// Creates a definition with a parent definition.
376    /// If there are multiple definitions with the same DefPathData and the same parent, use
377    /// `disambiguator` to differentiate them. Distinct `DisambiguatorState` instances are not
378    /// guaranteed to generate unique disambiguators and should instead ensure that the `parent`
379    /// and `data` pair is distinct from other instances.
380    pub fn create_def(
381        &mut self,
382        parent: LocalDefId,
383        data: DefPathData,
384        disambiguator: &mut DisambiguatorState,
385    ) -> LocalDefId {
386        // We can't use `Debug` implementation for `LocalDefId` here, since it tries to acquire a
387        // reference to `Definitions` and we're already holding a mutable reference.
388        debug!(
389            "create_def(parent={}, data={data:?})",
390            self.def_path(parent).to_string_no_crate_verbose(),
391        );
392
393        // The root node must be created in `new()`.
394        assert!(data != DefPathData::CrateRoot);
395
396        // Find the next free disambiguator for this key.
397        let disambiguator = {
398            let next_disamb = disambiguator.next.entry((parent, data)).or_insert(0);
399            let disambiguator = *next_disamb;
400            *next_disamb = next_disamb.checked_add(1).expect("disambiguator overflow");
401            disambiguator
402        };
403        let key = DefKey {
404            parent: Some(parent.local_def_index),
405            disambiguated_data: DisambiguatedDefPathData { data, disambiguator },
406        };
407
408        let parent_hash = self.table.def_path_hash(parent.local_def_index);
409        let def_path_hash = key.compute_stable_hash(parent_hash);
410
411        debug!("create_def: after disambiguation, key = {:?}", key);
412
413        // Create the definition.
414        LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) }
415    }
416
417    #[inline(always)]
418    /// Returns `None` if the `DefPathHash` does not correspond to a `LocalDefId`
419    /// in the current compilation session. This can legitimately happen if the
420    /// `DefPathHash` is from a `DefId` in an upstream crate or, during incr. comp.,
421    /// if the `DefPathHash` is from a previous compilation session and
422    /// the def-path does not exist anymore.
423    pub fn local_def_path_hash_to_def_id(&self, hash: DefPathHash) -> Option<LocalDefId> {
424        debug_assert!(hash.stable_crate_id() == self.table.stable_crate_id);
425        self.table
426            .def_path_hash_to_index
427            .get(&hash.local_hash())
428            .map(|local_def_index| LocalDefId { local_def_index })
429    }
430
431    pub fn def_path_hash_to_def_index_map(&self) -> &DefPathHashMap {
432        &self.table.def_path_hash_to_index
433    }
434
435    pub fn num_definitions(&self) -> usize {
436        self.table.def_path_hashes.len()
437    }
438}
439
440#[derive(Copy, Clone, PartialEq, Debug)]
441pub enum DefPathDataName {
442    Named(Symbol),
443    Anon { namespace: Symbol },
444}
445
446impl DefPathData {
447    pub fn get_opt_name(&self) -> Option<Symbol> {
448        use self::DefPathData::*;
449        match *self {
450            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name)
451            | OpaqueLifetime(name) => Some(name),
452
453            Impl
454            | ForeignMod
455            | CrateRoot
456            | Use
457            | GlobalAsm
458            | Closure
459            | Ctor
460            | AnonConst
461            | OpaqueTy
462            | AnonAssocTy(..)
463            | SyntheticCoroutineBody
464            | NestedStatic => None,
465        }
466    }
467
468    fn hashed_symbol(&self) -> Option<Symbol> {
469        use self::DefPathData::*;
470        match *self {
471            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) | AnonAssocTy(name)
472            | OpaqueLifetime(name) => Some(name),
473
474            Impl
475            | ForeignMod
476            | CrateRoot
477            | Use
478            | GlobalAsm
479            | Closure
480            | Ctor
481            | AnonConst
482            | OpaqueTy
483            | SyntheticCoroutineBody
484            | NestedStatic => None,
485        }
486    }
487
488    pub fn name(&self) -> DefPathDataName {
489        use self::DefPathData::*;
490        match *self {
491            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name)
492            | OpaqueLifetime(name) => DefPathDataName::Named(name),
493            // Note that this does not show up in user print-outs.
494            CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
495            Impl => DefPathDataName::Anon { namespace: kw::Impl },
496            ForeignMod => DefPathDataName::Anon { namespace: kw::Extern },
497            Use => DefPathDataName::Anon { namespace: kw::Use },
498            GlobalAsm => DefPathDataName::Anon { namespace: sym::global_asm },
499            Closure => DefPathDataName::Anon { namespace: sym::closure },
500            Ctor => DefPathDataName::Anon { namespace: sym::constructor },
501            AnonConst => DefPathDataName::Anon { namespace: sym::constant },
502            OpaqueTy => DefPathDataName::Anon { namespace: sym::opaque },
503            AnonAssocTy(..) => DefPathDataName::Anon { namespace: sym::anon_assoc },
504            SyntheticCoroutineBody => DefPathDataName::Anon { namespace: sym::synthetic },
505            NestedStatic => DefPathDataName::Anon { namespace: sym::nested },
506        }
507    }
508}
509
510impl fmt::Display for DefPathData {
511    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
512        match self.name() {
513            DefPathDataName::Named(name) => f.write_str(name.as_str()),
514            // FIXME(#70334): this will generate legacy {{closure}}, {{impl}}, etc
515            DefPathDataName::Anon { namespace } => write!(f, "{{{{{namespace}}}}}"),
516        }
517    }
518}
rustc_hir/definitions.rs

rustc_hir/
definitions.rs
