compiler/rustc_hir/src/definitions.rs - third_party/rust - Git at Google

 //! For each definition, we track the following data. A definition
 //! here is defined somewhat circularly as "something with a `DefId`",
 //! but it generally corresponds to things like structs, enums, etc.
 //! There are also some rather random cases (like const initializer
 //! expressions) that are mostly just leftovers.

 pub use crate::def_id::DefPathHash;
 use crate::def_id::{CrateNum, DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
 use crate::hir;

 use rustc_ast::crate_disambiguator::CrateDisambiguator;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_index::vec::IndexVec;
 use rustc_span::hygiene::ExpnId;
 use rustc_span::symbol::{kw, sym, Symbol};

 use std::fmt::{self, Write};
 use std::hash::Hash;
 use tracing::debug;

 /// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
 /// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`
 /// stores the `DefIndex` of its parent.
 /// There is one `DefPathTable` for each crate.
 #[derive(Clone, Default)]
 pub struct DefPathTable {
     index_to_key: IndexVec<DefIndex, DefKey>,
     def_path_hashes: IndexVec<DefIndex, DefPathHash>,
 }

 impl DefPathTable {
     fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
         let index = {
             let index = DefIndex::from(self.index_to_key.len());
             debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
             self.index_to_key.push(key);
             index
         };
         self.def_path_hashes.push(def_path_hash);
         debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
         index
     }

     #[inline(always)]
     pub fn def_key(&self, index: DefIndex) -> DefKey {
         self.index_to_key[index]
     }

     #[inline(always)]
     pub fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
         let hash = self.def_path_hashes[index];
         debug!("def_path_hash({:?}) = {:?}", index, hash);
         hash
     }

     pub fn num_def_ids(&self) -> usize {
         self.index_to_key.len()
     }

     pub fn enumerated_keys_and_path_hashes(
         &self,
     ) -> impl Iterator<Item = (DefIndex, &DefKey, &DefPathHash)> + '_ {
         self.index_to_key
             .iter_enumerated()
             .map(move |(index, key)| (index, key, &self.def_path_hashes[index]))
     }

     pub fn all_def_path_hashes_and_def_ids(
         &self,
         krate: CrateNum,
     ) -> impl Iterator<Item = (DefPathHash, DefId)> + '_ {
         self.def_path_hashes
             .iter_enumerated()
             .map(move |(index, hash)| (*hash, DefId { krate, index }))
     }
 }

 /// The definition table containing node definitions.
 /// It holds the `DefPathTable` for `LocalDefId`s/`DefPath`s.
 /// It also stores mappings to convert `LocalDefId`s to/from `HirId`s.
 #[derive(Clone)]
 pub struct Definitions {
     table: DefPathTable,

     // FIXME(eddyb) ideally all `LocalDefId`s would be HIR owners.
     pub(super) def_id_to_hir_id: IndexVec<LocalDefId, Option<hir::HirId>>,
     /// The reverse mapping of `def_id_to_hir_id`.
     pub(super) hir_id_to_def_id: FxHashMap<hir::HirId, LocalDefId>,

     /// If `ExpnId` is an ID of some macro expansion,
     /// then `DefId` is the normal module (`mod`) in which the expanded macro was defined.
     parent_modules_of_macro_defs: FxHashMap<ExpnId, DefId>,
     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
     expansions_that_defined: FxHashMap<LocalDefId, ExpnId>,
 }

 /// A unique identifier that we can use to lookup a definition
 /// precisely. It combines the index of the definition's parent (if
 /// any) with a `DisambiguatedDefPathData`.
 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 pub struct DefKey {
     /// The parent path.
     pub parent: Option<DefIndex>,

     /// The identifier of this node.
     pub disambiguated_data: DisambiguatedDefPathData,
 }

 impl DefKey {
     fn compute_stable_hash(&self, parent_hash: DefPathHash) -> DefPathHash {
         let mut hasher = StableHasher::new();

         // We hash a `0u8` here to disambiguate between regular `DefPath` hashes,
         // and the special "root_parent" below.
         0u8.hash(&mut hasher);
         parent_hash.hash(&mut hasher);

         let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;

         ::std::mem::discriminant(data).hash(&mut hasher);
         if let Some(name) = data.get_opt_name() {
             // Get a stable hash by considering the symbol chars rather than
             // the symbol index.
             name.as_str().hash(&mut hasher);
         }

         disambiguator.hash(&mut hasher);

         DefPathHash(hasher.finish())
     }

     fn root_parent_stable_hash(
         crate_name: &str,
         crate_disambiguator: CrateDisambiguator,
     ) -> DefPathHash {
         let mut hasher = StableHasher::new();
         // Disambiguate this from a regular `DefPath` hash; see `compute_stable_hash()` above.
         1u8.hash(&mut hasher);
         crate_name.hash(&mut hasher);
         crate_disambiguator.hash(&mut hasher);
         DefPathHash(hasher.finish())
     }
 }

 /// A pair of `DefPathData` and an integer disambiguator. The integer is
 /// normally `0`, but in the event that there are multiple defs with the
 /// same `parent` and `data`, we use this field to disambiguate
 /// between them. This introduces some artificial ordering dependency
 /// but means that if you have, e.g., two impls for the same type in
 /// the same module, they do get distinct `DefId`s.
 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 pub struct DisambiguatedDefPathData {
     pub data: DefPathData,
     pub disambiguator: u32,
 }

 impl DisambiguatedDefPathData {
     pub fn fmt_maybe_verbose(&self, writer: &mut impl Write, verbose: bool) -> fmt::Result {
         match self.data.name() {
             DefPathDataName::Named(name) => {
                 if verbose && self.disambiguator != 0 {
                     write!(writer, "{}#{}", name, self.disambiguator)
                 } else {
                     writer.write_str(&name.as_str())
                 }
             }
             DefPathDataName::Anon { namespace } => {
                 write!(writer, "{{{}#{}}}", namespace, self.disambiguator)
             }
         }
     }
 }

 impl fmt::Display for DisambiguatedDefPathData {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.fmt_maybe_verbose(f, true)
     }
 }

 #[derive(Clone, Debug, Encodable, Decodable)]
 pub struct DefPath {
     /// The path leading from the crate root to the item.
     pub data: Vec<DisambiguatedDefPathData>,

     /// The crate root this path is relative to.
     pub krate: CrateNum,
 }

 impl DefPath {
     pub fn is_local(&self) -> bool {
         self.krate == LOCAL_CRATE
     }

     pub fn make<FN>(krate: CrateNum, start_index: DefIndex, mut get_key: FN) -> DefPath
     where
         FN: FnMut(DefIndex) -> DefKey,
     {
         let mut data = vec![];
         let mut index = Some(start_index);
         loop {
             debug!("DefPath::make: krate={:?} index={:?}", krate, index);
             let p = index.unwrap();
             let key = get_key(p);
             debug!("DefPath::make: key={:?}", key);
             match key.disambiguated_data.data {
                 DefPathData::CrateRoot => {
                     assert!(key.parent.is_none());
                     break;
                 }
                 _ => {
                     data.push(key.disambiguated_data);
                     index = key.parent;
                 }
             }
         }
         data.reverse();
         DefPath { data, krate }
     }

     /// Returns a string representation of the `DefPath` without
     /// the crate-prefix. This method is useful if you don't have
     /// a `TyCtxt` available.
     pub fn to_string_no_crate_verbose(&self) -> String {
         let mut s = String::with_capacity(self.data.len() * 16);

         for component in &self.data {
             write!(s, "::{}", component).unwrap();
         }

         s
     }

     /// Returns a filename-friendly string of the `DefPath`, without
     /// the crate-prefix. This method is useful if you don't have
     /// a `TyCtxt` available.
     pub fn to_filename_friendly_no_crate(&self) -> String {
         let mut s = String::with_capacity(self.data.len() * 16);

         let mut opt_delimiter = None;
         for component in &self.data {
             s.extend(opt_delimiter);
             opt_delimiter = Some('-');
             write!(s, "{}", component).unwrap();
         }

         s
     }
 }

 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
 pub enum DefPathData {
     // Root: these should only be used for the root nodes, because
     // they are treated specially by the `def_path` function.
     /// The crate root (marker).
     CrateRoot,
     // Catch-all for random `DefId` things like `DUMMY_NODE_ID`.
     Misc,

     // Different kinds of items and item-like things:
     /// An impl.
     Impl,
     /// Something in the type namespace.
     TypeNs(Symbol),
     /// Something in the value namespace.
     ValueNs(Symbol),
     /// Something in the macro namespace.
     MacroNs(Symbol),
     /// Something in the lifetime namespace.
     LifetimeNs(Symbol),
     /// A closure expression.
     ClosureExpr,

     // Subportions of items:
     /// Implicit constructor for a unit or tuple-like struct or enum variant.
     Ctor,
     /// A constant expression (see `{ast,hir}::AnonConst`).
     AnonConst,
     /// An `impl Trait` type node.
     ImplTrait,
 }

 impl Definitions {
     pub fn def_path_table(&self) -> &DefPathTable {
         &self.table
     }

     /// Gets the number of definitions.
     pub fn def_index_count(&self) -> usize {
         self.table.index_to_key.len()
     }

     pub fn def_key(&self, id: LocalDefId) -> DefKey {
         self.table.def_key(id.local_def_index)
     }

     #[inline(always)]
     pub fn def_path_hash(&self, id: LocalDefId) -> DefPathHash {
         self.table.def_path_hash(id.local_def_index)
     }

     /// Returns the path from the crate root to `index`. The root
     /// nodes are not included in the path (i.e., this will be an
     /// empty vector for the crate root). For an inlined item, this
     /// will be the path of the item in the external crate (but the
     /// path will begin with the path to the external crate).
     pub fn def_path(&self, id: LocalDefId) -> DefPath {
         DefPath::make(LOCAL_CRATE, id.local_def_index, |index| {
             self.def_key(LocalDefId { local_def_index: index })
         })
     }

     #[inline]
     #[track_caller]
     pub fn local_def_id_to_hir_id(&self, id: LocalDefId) -> hir::HirId {
         self.def_id_to_hir_id[id].unwrap()
     }

     #[inline]
     pub fn opt_local_def_id_to_hir_id(&self, id: LocalDefId) -> Option<hir::HirId> {
         self.def_id_to_hir_id[id]
     }

     #[inline]
     pub fn opt_hir_id_to_local_def_id(&self, hir_id: hir::HirId) -> Option<LocalDefId> {
         self.hir_id_to_def_id.get(&hir_id).copied()
     }

     /// Adds a root definition (no parent) and a few other reserved definitions.
     pub fn new(crate_name: &str, crate_disambiguator: CrateDisambiguator) -> Definitions {
         let key = DefKey {
             parent: None,
             disambiguated_data: DisambiguatedDefPathData {
                 data: DefPathData::CrateRoot,
                 disambiguator: 0,
             },
         };

         let parent_hash = DefKey::root_parent_stable_hash(crate_name, crate_disambiguator);
         let def_path_hash = key.compute_stable_hash(parent_hash);

         // Create the root definition.
         let mut table = DefPathTable::default();
         let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);

         Definitions {
             table,
             def_id_to_hir_id: Default::default(),
             hir_id_to_def_id: Default::default(),
             expansions_that_defined: Default::default(),
             parent_modules_of_macro_defs: Default::default(),
         }
     }

     /// Retrieves the root definition.
     pub fn get_root_def(&self) -> LocalDefId {
         LocalDefId { local_def_index: CRATE_DEF_INDEX }
     }

     /// Adds a definition with a parent definition.
     pub fn create_def(
         &mut self,
         parent: LocalDefId,
         data: DefPathData,
         expn_id: ExpnId,
         mut next_disambiguator: impl FnMut(LocalDefId, DefPathData) -> u32,
     ) -> LocalDefId {
         debug!("create_def(parent={:?}, data={:?}, expn_id={:?})", parent, data, expn_id);

         // The root node must be created with `create_root_def()`.
         assert!(data != DefPathData::CrateRoot);

         let disambiguator = next_disambiguator(parent, data);
         let key = DefKey {
             parent: Some(parent.local_def_index),
             disambiguated_data: DisambiguatedDefPathData { data, disambiguator },
         };

         let parent_hash = self.table.def_path_hash(parent.local_def_index);
         let def_path_hash = key.compute_stable_hash(parent_hash);

         debug!("create_def: after disambiguation, key = {:?}", key);

         // Create the definition.
         let def_id = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };

         if expn_id != ExpnId::root() {
             self.expansions_that_defined.insert(def_id, expn_id);
         }

         def_id
     }

     /// Initializes the `LocalDefId` to `HirId` mapping once it has been generated during
     /// AST to HIR lowering.
     pub fn init_def_id_to_hir_id_mapping(
         &mut self,
         mapping: IndexVec<LocalDefId, Option<hir::HirId>>,
     ) {
         assert!(
             self.def_id_to_hir_id.is_empty(),
             "trying to initialize `LocalDefId` <-> `HirId` mappings twice"
         );

         // Build the reverse mapping of `def_id_to_hir_id`.
         self.hir_id_to_def_id = mapping
             .iter_enumerated()
             .filter_map(|(def_id, hir_id)| hir_id.map(|hir_id| (hir_id, def_id)))
             .collect();

         self.def_id_to_hir_id = mapping;
     }

     pub fn expansion_that_defined(&self, id: LocalDefId) -> ExpnId {
         self.expansions_that_defined.get(&id).copied().unwrap_or(ExpnId::root())
     }

     pub fn parent_module_of_macro_def(&self, expn_id: ExpnId) -> DefId {
         self.parent_modules_of_macro_defs[&expn_id]
     }

     pub fn add_parent_module_of_macro_def(&mut self, expn_id: ExpnId, module: DefId) {
         self.parent_modules_of_macro_defs.insert(expn_id, module);
     }
 }

 #[derive(Copy, Clone, PartialEq, Debug)]
 pub enum DefPathDataName {
     Named(Symbol),
     Anon { namespace: Symbol },
 }

 impl DefPathData {
     pub fn get_opt_name(&self) -> Option<Symbol> {
         use self::DefPathData::*;
         match *self {
             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),

             Impl | CrateRoot | Misc | ClosureExpr | Ctor | AnonConst | ImplTrait => None,
         }
     }

     pub fn name(&self) -> DefPathDataName {
         use self::DefPathData::*;
         match *self {
             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => {
                 DefPathDataName::Named(name)
             }
             // Note that this does not show up in user print-outs.
             CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
             Impl => DefPathDataName::Anon { namespace: kw::Impl },
             Misc => DefPathDataName::Anon { namespace: sym::misc },
             ClosureExpr => DefPathDataName::Anon { namespace: sym::closure },
             Ctor => DefPathDataName::Anon { namespace: sym::constructor },
             AnonConst => DefPathDataName::Anon { namespace: sym::constant },
             ImplTrait => DefPathDataName::Anon { namespace: sym::opaque },
         }
     }
 }

 impl fmt::Display for DefPathData {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.name() {
             DefPathDataName::Named(name) => f.write_str(&name.as_str()),
             // FIXME(#70334): this will generate legacy {{closure}}, {{impl}}, etc
             DefPathDataName::Anon { namespace } => write!(f, "{{{{{}}}}}", namespace),
         }
     }
 }
	//! For each definition, we track the following data. A definition
	//! here is defined somewhat circularly as "something with a `DefId`",
	//! but it generally corresponds to things like structs, enums, etc.
	//! There are also some rather random cases (like const initializer
	//! expressions) that are mostly just leftovers.

	pub use crate::def_id::DefPathHash;
	use crate::def_id::{CrateNum, DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
	use crate::hir;

	use rustc_ast::crate_disambiguator::CrateDisambiguator;
	use rustc_data_structures::fx::FxHashMap;
	use rustc_data_structures::stable_hasher::StableHasher;
	use rustc_index::vec::IndexVec;
	use rustc_span::hygiene::ExpnId;
	use rustc_span::symbol::{kw, sym, Symbol};

	use std::fmt::{self, Write};
	use std::hash::Hash;
	use tracing::debug;

	/// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
	/// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`
	/// stores the `DefIndex` of its parent.
	/// There is one `DefPathTable` for each crate.
	#[derive(Clone, Default)]
	pub struct DefPathTable {
	index_to_key: IndexVec<DefIndex, DefKey>,
	def_path_hashes: IndexVec<DefIndex, DefPathHash>,
	}

	impl DefPathTable {
	fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
	let index = {
	let index = DefIndex::from(self.index_to_key.len());
	debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
	self.index_to_key.push(key);
	index
	};
	self.def_path_hashes.push(def_path_hash);
	debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
	index
	}

	#[inline(always)]
	pub fn def_key(&self, index: DefIndex) -> DefKey {
	self.index_to_key[index]
	}

	#[inline(always)]
	pub fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
	let hash = self.def_path_hashes[index];
	debug!("def_path_hash({:?}) = {:?}", index, hash);
	hash
	}

	pub fn num_def_ids(&self) -> usize {
	self.index_to_key.len()
	}

	pub fn enumerated_keys_and_path_hashes(
	&self,
	) -> impl Iterator<Item = (DefIndex, &DefKey, &DefPathHash)> + '_ {
	self.index_to_key
	.iter_enumerated()
	.map(move \|(index, key)\| (index, key, &self.def_path_hashes[index]))
	}

	pub fn all_def_path_hashes_and_def_ids(
	&self,
	krate: CrateNum,
	) -> impl Iterator<Item = (DefPathHash, DefId)> + '_ {
	self.def_path_hashes
	.iter_enumerated()
	.map(move \|(index, hash)\| (*hash, DefId { krate, index }))
	}
	}

	/// The definition table containing node definitions.
	/// It holds the `DefPathTable` for `LocalDefId`s/`DefPath`s.
	/// It also stores mappings to convert `LocalDefId`s to/from `HirId`s.
	#[derive(Clone)]
	pub struct Definitions {
	table: DefPathTable,

	// FIXME(eddyb) ideally all `LocalDefId`s would be HIR owners.
	pub(super) def_id_to_hir_id: IndexVec<LocalDefId, Option<hir::HirId>>,
	/// The reverse mapping of `def_id_to_hir_id`.
	pub(super) hir_id_to_def_id: FxHashMap<hir::HirId, LocalDefId>,

	/// If `ExpnId` is an ID of some macro expansion,
	/// then `DefId` is the normal module (`mod`) in which the expanded macro was defined.
	parent_modules_of_macro_defs: FxHashMap<ExpnId, DefId>,
	/// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
	expansions_that_defined: FxHashMap<LocalDefId, ExpnId>,
	}

	/// A unique identifier that we can use to lookup a definition
	/// precisely. It combines the index of the definition's parent (if
	/// any) with a `DisambiguatedDefPathData`.
	#[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
	pub struct DefKey {
	/// The parent path.
	pub parent: Option<DefIndex>,

	/// The identifier of this node.
	pub disambiguated_data: DisambiguatedDefPathData,
	}

	impl DefKey {
	fn compute_stable_hash(&self, parent_hash: DefPathHash) -> DefPathHash {
	let mut hasher = StableHasher::new();

	// We hash a `0u8` here to disambiguate between regular `DefPath` hashes,
	// and the special "root_parent" below.
	0u8.hash(&mut hasher);
	parent_hash.hash(&mut hasher);

	let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;

	::std::mem::discriminant(data).hash(&mut hasher);
	if let Some(name) = data.get_opt_name() {
	// Get a stable hash by considering the symbol chars rather than
	// the symbol index.
	name.as_str().hash(&mut hasher);
	}

	disambiguator.hash(&mut hasher);

	DefPathHash(hasher.finish())
	}

	fn root_parent_stable_hash(
	crate_name: &str,
	crate_disambiguator: CrateDisambiguator,
	) -> DefPathHash {
	let mut hasher = StableHasher::new();
	// Disambiguate this from a regular `DefPath` hash; see `compute_stable_hash()` above.
	1u8.hash(&mut hasher);
	crate_name.hash(&mut hasher);
	crate_disambiguator.hash(&mut hasher);
	DefPathHash(hasher.finish())
	}
	}

	/// A pair of `DefPathData` and an integer disambiguator. The integer is
	/// normally `0`, but in the event that there are multiple defs with the
	/// same `parent` and `data`, we use this field to disambiguate
	/// between them. This introduces some artificial ordering dependency
	/// but means that if you have, e.g., two impls for the same type in
	/// the same module, they do get distinct `DefId`s.
	#[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
	pub struct DisambiguatedDefPathData {
	pub data: DefPathData,
	pub disambiguator: u32,
	}

	impl DisambiguatedDefPathData {
	pub fn fmt_maybe_verbose(&self, writer: &mut impl Write, verbose: bool) -> fmt::Result {
	match self.data.name() {
	DefPathDataName::Named(name) => {
	if verbose && self.disambiguator != 0 {
	write!(writer, "{}#{}", name, self.disambiguator)
	} else {
	writer.write_str(&name.as_str())
	}
	}
	DefPathDataName::Anon { namespace } => {
	write!(writer, "{{{}#{}}}", namespace, self.disambiguator)
	}
	}
	}
	}

	impl fmt::Display for DisambiguatedDefPathData {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	self.fmt_maybe_verbose(f, true)
	}
	}

	#[derive(Clone, Debug, Encodable, Decodable)]
	pub struct DefPath {
	/// The path leading from the crate root to the item.
	pub data: Vec<DisambiguatedDefPathData>,

	/// The crate root this path is relative to.
	pub krate: CrateNum,
	}

	impl DefPath {
	pub fn is_local(&self) -> bool {
	self.krate == LOCAL_CRATE
	}

	pub fn make<FN>(krate: CrateNum, start_index: DefIndex, mut get_key: FN) -> DefPath
	where
	FN: FnMut(DefIndex) -> DefKey,
	{
	let mut data = vec![];
	let mut index = Some(start_index);
	loop {
	debug!("DefPath::make: krate={:?} index={:?}", krate, index);
	let p = index.unwrap();
	let key = get_key(p);
	debug!("DefPath::make: key={:?}", key);
	match key.disambiguated_data.data {
	DefPathData::CrateRoot => {
	assert!(key.parent.is_none());
	break;
	}
	_ => {
	data.push(key.disambiguated_data);
	index = key.parent;
	}
	}
	}
	data.reverse();
	DefPath { data, krate }
	}

	/// Returns a string representation of the `DefPath` without
	/// the crate-prefix. This method is useful if you don't have
	/// a `TyCtxt` available.
	pub fn to_string_no_crate_verbose(&self) -> String {
	let mut s = String::with_capacity(self.data.len() * 16);

	for component in &self.data {
	write!(s, "::{}", component).unwrap();
	}

	s
	}

	/// Returns a filename-friendly string of the `DefPath`, without
	/// the crate-prefix. This method is useful if you don't have
	/// a `TyCtxt` available.
	pub fn to_filename_friendly_no_crate(&self) -> String {
	let mut s = String::with_capacity(self.data.len() * 16);

	let mut opt_delimiter = None;
	for component in &self.data {
	s.extend(opt_delimiter);
	opt_delimiter = Some('-');
	write!(s, "{}", component).unwrap();
	}

	s
	}
	}

	#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
	pub enum DefPathData {
	// Root: these should only be used for the root nodes, because
	// they are treated specially by the `def_path` function.
	/// The crate root (marker).
	CrateRoot,
	// Catch-all for random `DefId` things like `DUMMY_NODE_ID`.
	Misc,

	// Different kinds of items and item-like things:
	/// An impl.
	Impl,
	/// Something in the type namespace.
	TypeNs(Symbol),
	/// Something in the value namespace.
	ValueNs(Symbol),
	/// Something in the macro namespace.
	MacroNs(Symbol),
	/// Something in the lifetime namespace.
	LifetimeNs(Symbol),
	/// A closure expression.
	ClosureExpr,

	// Subportions of items:
	/// Implicit constructor for a unit or tuple-like struct or enum variant.
	Ctor,
	/// A constant expression (see `{ast,hir}::AnonConst`).
	AnonConst,
	/// An `impl Trait` type node.
	ImplTrait,
	}

	impl Definitions {
	pub fn def_path_table(&self) -> &DefPathTable {
	&self.table
	}

	/// Gets the number of definitions.
	pub fn def_index_count(&self) -> usize {
	self.table.index_to_key.len()
	}

	pub fn def_key(&self, id: LocalDefId) -> DefKey {
	self.table.def_key(id.local_def_index)
	}

	#[inline(always)]
	pub fn def_path_hash(&self, id: LocalDefId) -> DefPathHash {
	self.table.def_path_hash(id.local_def_index)
	}

	/// Returns the path from the crate root to `index`. The root
	/// nodes are not included in the path (i.e., this will be an
	/// empty vector for the crate root). For an inlined item, this
	/// will be the path of the item in the external crate (but the
	/// path will begin with the path to the external crate).
	pub fn def_path(&self, id: LocalDefId) -> DefPath {
	DefPath::make(LOCAL_CRATE, id.local_def_index, \|index\| {
	self.def_key(LocalDefId { local_def_index: index })
	})
	}

	#[inline]
	#[track_caller]
	pub fn local_def_id_to_hir_id(&self, id: LocalDefId) -> hir::HirId {
	self.def_id_to_hir_id[id].unwrap()
	}

	#[inline]
	pub fn opt_local_def_id_to_hir_id(&self, id: LocalDefId) -> Option<hir::HirId> {
	self.def_id_to_hir_id[id]
	}

	#[inline]
	pub fn opt_hir_id_to_local_def_id(&self, hir_id: hir::HirId) -> Option<LocalDefId> {
	self.hir_id_to_def_id.get(&hir_id).copied()
	}

	/// Adds a root definition (no parent) and a few other reserved definitions.
	pub fn new(crate_name: &str, crate_disambiguator: CrateDisambiguator) -> Definitions {
	let key = DefKey {
	parent: None,
	disambiguated_data: DisambiguatedDefPathData {
	data: DefPathData::CrateRoot,
	disambiguator: 0,
	},
	};

	let parent_hash = DefKey::root_parent_stable_hash(crate_name, crate_disambiguator);
	let def_path_hash = key.compute_stable_hash(parent_hash);

	// Create the root definition.
	let mut table = DefPathTable::default();
	let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
	assert_eq!(root.local_def_index, CRATE_DEF_INDEX);

	Definitions {
	table,
	def_id_to_hir_id: Default::default(),
	hir_id_to_def_id: Default::default(),
	expansions_that_defined: Default::default(),
	parent_modules_of_macro_defs: Default::default(),
	}
	}

	/// Retrieves the root definition.
	pub fn get_root_def(&self) -> LocalDefId {
	LocalDefId { local_def_index: CRATE_DEF_INDEX }
	}

	/// Adds a definition with a parent definition.
	pub fn create_def(
	&mut self,
	parent: LocalDefId,
	data: DefPathData,
	expn_id: ExpnId,
	mut next_disambiguator: impl FnMut(LocalDefId, DefPathData) -> u32,
	) -> LocalDefId {
	debug!("create_def(parent={:?}, data={:?}, expn_id={:?})", parent, data, expn_id);

	// The root node must be created with `create_root_def()`.
	assert!(data != DefPathData::CrateRoot);

	let disambiguator = next_disambiguator(parent, data);
	let key = DefKey {
	parent: Some(parent.local_def_index),
	disambiguated_data: DisambiguatedDefPathData { data, disambiguator },
	};

	let parent_hash = self.table.def_path_hash(parent.local_def_index);
	let def_path_hash = key.compute_stable_hash(parent_hash);

	debug!("create_def: after disambiguation, key = {:?}", key);

	// Create the definition.
	let def_id = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };

	if expn_id != ExpnId::root() {
	self.expansions_that_defined.insert(def_id, expn_id);
	}

	def_id
	}

	/// Initializes the `LocalDefId` to `HirId` mapping once it has been generated during
	/// AST to HIR lowering.
	pub fn init_def_id_to_hir_id_mapping(
	&mut self,
	mapping: IndexVec<LocalDefId, Option<hir::HirId>>,
	) {
	assert!(
	self.def_id_to_hir_id.is_empty(),
	"trying to initialize `LocalDefId` <-> `HirId` mappings twice"
	);

	// Build the reverse mapping of `def_id_to_hir_id`.
	self.hir_id_to_def_id = mapping
	.iter_enumerated()
	.filter_map(\|(def_id, hir_id)\| hir_id.map(\|hir_id\| (hir_id, def_id)))
	.collect();

	self.def_id_to_hir_id = mapping;
	}

	pub fn expansion_that_defined(&self, id: LocalDefId) -> ExpnId {
	self.expansions_that_defined.get(&id).copied().unwrap_or(ExpnId::root())
	}

	pub fn parent_module_of_macro_def(&self, expn_id: ExpnId) -> DefId {
	self.parent_modules_of_macro_defs[&expn_id]
	}

	pub fn add_parent_module_of_macro_def(&mut self, expn_id: ExpnId, module: DefId) {
	self.parent_modules_of_macro_defs.insert(expn_id, module);
	}
	}

	#[derive(Copy, Clone, PartialEq, Debug)]
	pub enum DefPathDataName {
	Named(Symbol),
	Anon { namespace: Symbol },
	}

	impl DefPathData {
	pub fn get_opt_name(&self) -> Option<Symbol> {
	use self::DefPathData::*;
	match *self {
	TypeNs(name) \| ValueNs(name) \| MacroNs(name) \| LifetimeNs(name) => Some(name),

	Impl \| CrateRoot \| Misc \| ClosureExpr \| Ctor \| AnonConst \| ImplTrait => None,
	}
	}

	pub fn name(&self) -> DefPathDataName {
	use self::DefPathData::*;
	match *self {
	TypeNs(name) \| ValueNs(name) \| MacroNs(name) \| LifetimeNs(name) => {
	DefPathDataName::Named(name)
	}
	// Note that this does not show up in user print-outs.
	CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
	Impl => DefPathDataName::Anon { namespace: kw::Impl },
	Misc => DefPathDataName::Anon { namespace: sym::misc },
	ClosureExpr => DefPathDataName::Anon { namespace: sym::closure },
	Ctor => DefPathDataName::Anon { namespace: sym::constructor },
	AnonConst => DefPathDataName::Anon { namespace: sym::constant },
	ImplTrait => DefPathDataName::Anon { namespace: sym::opaque },
	}
	}
	}

	impl fmt::Display for DefPathData {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	match self.name() {
	DefPathDataName::Named(name) => f.write_str(&name.as_str()),
	// FIXME(#70334): this will generate legacy {{closure}}, {{impl}}, etc
	DefPathDataName::Anon { namespace } => write!(f, "{{{{{}}}}}", namespace),
	}
	}
	}