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use crate::{HashStableContext, Symbol};
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::stable_hasher::{Hash64, HashStable, StableHasher, ToStableHashKey};
use rustc_data_structures::unhash::Unhasher;
use rustc_data_structures::AtomicRef;
use rustc_index::Idx;
use rustc_macros::HashStable_Generic;
use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
use std::fmt;
use std::hash::{BuildHasherDefault, Hash, Hasher};
pub type StableCrateIdMap =
indexmap::IndexMap<StableCrateId, CrateNum, BuildHasherDefault<Unhasher>>;
rustc_index::newtype_index! {
#[custom_encodable]
#[debug_format = "crate{}"]
pub struct CrateNum {}
}
/// Item definitions in the currently-compiled crate would have the `CrateNum`
/// `LOCAL_CRATE` in their `DefId`.
pub const LOCAL_CRATE: CrateNum = CrateNum::from_u32(0);
impl CrateNum {
#[inline]
pub fn new(x: usize) -> CrateNum {
CrateNum::from_usize(x)
}
// FIXME(typed_def_id): Replace this with `as_mod_def_id`.
#[inline]
pub fn as_def_id(self) -> DefId {
DefId { krate: self, index: CRATE_DEF_INDEX }
}
#[inline]
pub fn as_mod_def_id(self) -> ModDefId {
ModDefId::new_unchecked(DefId { krate: self, index: CRATE_DEF_INDEX })
}
}
impl fmt::Display for CrateNum {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(&self.as_u32(), f)
}
}
/// As a local identifier, a `CrateNum` is only meaningful within its context, e.g. within a tcx.
/// Therefore, make sure to include the context when encode a `CrateNum`.
impl<E: Encoder> Encodable<E> for CrateNum {
default fn encode(&self, s: &mut E) {
s.emit_u32(self.as_u32());
}
}
impl<D: Decoder> Decodable<D> for CrateNum {
default fn decode(d: &mut D) -> CrateNum {
CrateNum::from_u32(d.read_u32())
}
}
/// A `DefPathHash` is a fixed-size representation of a `DefPath` that is
/// stable across crate and compilation session boundaries. It consists of two
/// separate 64-bit hashes. The first uniquely identifies the crate this
/// `DefPathHash` originates from (see [StableCrateId]), and the second
/// uniquely identifies the corresponding `DefPath` within that crate. Together
/// they form a unique identifier within an entire crate graph.
///
/// There is a very small chance of hash collisions, which would mean that two
/// different `DefPath`s map to the same `DefPathHash`. Proceeding compilation
/// with such a hash collision would very probably lead to an ICE, and in the
/// worst case lead to a silent mis-compilation. The compiler therefore actively
/// and exhaustively checks for such hash collisions and aborts compilation if
/// it finds one.
///
/// `DefPathHash` uses 64-bit hashes for both the crate-id part and the
/// crate-internal part, even though it is likely that there are many more
/// `LocalDefId`s in a single crate than there are individual crates in a crate
/// graph. Since we use the same number of bits in both cases, the collision
/// probability for the crate-local part will be quite a bit higher (though
/// still very small).
///
/// This imbalance is not by accident: A hash collision in the
/// crate-local part of a `DefPathHash` will be detected and reported while
/// compiling the crate in question. Such a collision does not depend on
/// outside factors and can be easily fixed by the crate maintainer (e.g. by
/// renaming the item in question or by bumping the crate version in a harmless
/// way).
///
/// A collision between crate-id hashes on the other hand is harder to fix
/// because it depends on the set of crates in the entire crate graph of a
/// compilation session. Again, using the same crate with a different version
/// number would fix the issue with a high probability -- but that might be
/// easier said then done if the crates in questions are dependencies of
/// third-party crates.
///
/// That being said, given a high quality hash function, the collision
/// probabilities in question are very small. For example, for a big crate like
/// `rustc_middle` (with ~50000 `LocalDefId`s as of the time of writing) there
/// is a probability of roughly 1 in 14,750,000,000 of a crate-internal
/// collision occurring. For a big crate graph with 1000 crates in it, there is
/// a probability of 1 in 36,890,000,000,000 of a `StableCrateId` collision.
#[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Debug)]
#[derive(HashStable_Generic, Encodable, Decodable)]
pub struct DefPathHash(pub Fingerprint);
impl DefPathHash {
/// Returns the [StableCrateId] identifying the crate this [DefPathHash]
/// originates from.
#[inline]
pub fn stable_crate_id(&self) -> StableCrateId {
StableCrateId(self.0.split().0)
}
/// Returns the crate-local part of the [DefPathHash].
///
/// Used for tests.
#[inline]
pub fn local_hash(&self) -> Hash64 {
self.0.split().1
}
/// Builds a new [DefPathHash] with the given [StableCrateId] and
/// `local_hash`, where `local_hash` must be unique within its crate.
pub fn new(stable_crate_id: StableCrateId, local_hash: Hash64) -> DefPathHash {
DefPathHash(Fingerprint::new(stable_crate_id.0, local_hash))
}
}
impl Default for DefPathHash {
fn default() -> Self {
DefPathHash(Fingerprint::ZERO)
}
}
/// A [`StableCrateId`] is a 64-bit hash of a crate name, together with all
/// `-Cmetadata` arguments, and some other data. It is to [`CrateNum`] what [`DefPathHash`] is to
/// [`DefId`]. It is stable across compilation sessions.
///
/// Since the ID is a hash value, there is a small chance that two crates
/// end up with the same [`StableCrateId`]. The compiler will check for such
/// collisions when loading crates and abort compilation in order to avoid
/// further trouble.
///
/// For more information on the possibility of hash collisions in rustc,
/// see the discussion in [`DefId`].
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
#[derive(Hash, HashStable_Generic, Encodable, Decodable)]
pub struct StableCrateId(pub(crate) Hash64);
impl StableCrateId {
/// Computes the stable ID for a crate with the given name and
/// `-Cmetadata` arguments.
pub fn new(
crate_name: Symbol,
is_exe: bool,
mut metadata: Vec<String>,
cfg_version: &'static str,
) -> StableCrateId {
let mut hasher = StableHasher::new();
// We must hash the string text of the crate name, not the id, as the id is not stable
// across builds.
crate_name.as_str().hash(&mut hasher);
// We don't want the stable crate ID to depend on the order of
// -C metadata arguments, so sort them:
metadata.sort();
// Every distinct -C metadata value is only incorporated once:
metadata.dedup();
hasher.write(b"metadata");
for s in &metadata {
// Also incorporate the length of a metadata string, so that we generate
// different values for `-Cmetadata=ab -Cmetadata=c` and
// `-Cmetadata=a -Cmetadata=bc`
hasher.write_usize(s.len());
hasher.write(s.as_bytes());
}
// Also incorporate crate type, so that we don't get symbol conflicts when
// linking against a library of the same name, if this is an executable.
hasher.write(if is_exe { b"exe" } else { b"lib" });
// Also incorporate the rustc version. Otherwise, with -Zsymbol-mangling-version=v0
// and no -Cmetadata, symbols from the same crate compiled with different versions of
// rustc are named the same.
//
// RUSTC_FORCE_RUSTC_VERSION is used to inject rustc version information
// during testing.
if let Some(val) = std::env::var_os("RUSTC_FORCE_RUSTC_VERSION") {
hasher.write(val.to_string_lossy().into_owned().as_bytes())
} else {
hasher.write(cfg_version.as_bytes())
}
StableCrateId(hasher.finish())
}
#[inline]
pub fn as_u64(self) -> u64 {
self.0.as_u64()
}
}
impl fmt::LowerHex for StableCrateId {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::LowerHex::fmt(&self.0, f)
}
}
rustc_index::newtype_index! {
/// A DefIndex is an index into the hir-map for a crate, identifying a
/// particular definition. It should really be considered an interned
/// shorthand for a particular DefPath.
#[custom_encodable] // (only encodable in metadata)
#[debug_format = "DefIndex({})"]
pub struct DefIndex {
/// The crate root is always assigned index 0 by the AST Map code,
/// thanks to `NodeCollector::new`.
const CRATE_DEF_INDEX = 0;
}
}
impl<E: Encoder> Encodable<E> for DefIndex {
default fn encode(&self, _: &mut E) {
panic!("cannot encode `DefIndex` with `{}`", std::any::type_name::<E>());
}
}
impl<D: Decoder> Decodable<D> for DefIndex {
default fn decode(_: &mut D) -> DefIndex {
panic!("cannot decode `DefIndex` with `{}`", std::any::type_name::<D>());
}
}
/// A `DefId` identifies a particular *definition*, by combining a crate
/// index and a def index.
///
/// You can create a `DefId` from a `LocalDefId` using `local_def_id.to_def_id()`.
#[derive(Clone, PartialEq, Eq, Copy)]
// Don't derive order on 64-bit big-endian, so we can be consistent regardless of field order.
#[cfg_attr(not(all(target_pointer_width = "64", target_endian = "big")), derive(PartialOrd, Ord))]
// On below-64 bit systems we can simply use the derived `Hash` impl
#[cfg_attr(not(target_pointer_width = "64"), derive(Hash))]
#[repr(C)]
#[rustc_pass_by_value]
// We guarantee field order. Note that the order is essential here, see below why.
pub struct DefId {
// cfg-ing the order of fields so that the `DefIndex` which is high entropy always ends up in
// the lower bits no matter the endianness. This allows the compiler to turn that `Hash` impl
// into a direct call to `u64::hash(_)`.
#[cfg(not(all(target_pointer_width = "64", target_endian = "big")))]
pub index: DefIndex,
pub krate: CrateNum,
#[cfg(all(target_pointer_width = "64", target_endian = "big"))]
pub index: DefIndex,
}
// On 64-bit systems, we can hash the whole `DefId` as one `u64` instead of two `u32`s. This
// improves performance without impairing `FxHash` quality. So the below code gets compiled to a
// noop on little endian systems because the memory layout of `DefId` is as follows:
//
// ```
// +-1--------------31-+-32-------------63-+
// ! index ! krate !
// +-------------------+-------------------+
// ```
//
// The order here has direct impact on `FxHash` quality because we have far more `DefIndex` per
// crate than we have `Crate`s within one compilation. Or in other words, this arrangement puts
// more entropy in the low bits than the high bits. The reason this matters is that `FxHash`, which
// is used throughout rustc, has problems distributing the entropy from the high bits, so reversing
// the order would lead to a large number of collisions and thus far worse performance.
//
// On 64-bit big-endian systems, this compiles to a 64-bit rotation by 32 bits, which is still
// faster than another `FxHash` round.
#[cfg(target_pointer_width = "64")]
impl Hash for DefId {
fn hash<H: Hasher>(&self, h: &mut H) {
(((self.krate.as_u32() as u64) << 32) | (self.index.as_u32() as u64)).hash(h)
}
}
// Implement the same comparison as derived with the other field order.
#[cfg(all(target_pointer_width = "64", target_endian = "big"))]
impl Ord for DefId {
#[inline]
fn cmp(&self, other: &DefId) -> std::cmp::Ordering {
Ord::cmp(&(self.index, self.krate), &(other.index, other.krate))
}
}
#[cfg(all(target_pointer_width = "64", target_endian = "big"))]
impl PartialOrd for DefId {
#[inline]
fn partial_cmp(&self, other: &DefId) -> Option<std::cmp::Ordering> {
Some(self.cmp(other))
}
}
impl DefId {
/// Makes a local `DefId` from the given `DefIndex`.
#[inline]
pub fn local(index: DefIndex) -> DefId {
DefId { krate: LOCAL_CRATE, index }
}
/// Returns whether the item is defined in the crate currently being compiled.
#[inline]
pub fn is_local(self) -> bool {
self.krate == LOCAL_CRATE
}
#[inline]
pub fn as_local(self) -> Option<LocalDefId> {
self.is_local().then(|| LocalDefId { local_def_index: self.index })
}
#[inline]
#[track_caller]
pub fn expect_local(self) -> LocalDefId {
// NOTE: `match` below is required to apply `#[track_caller]`,
// i.e. don't use closures.
match self.as_local() {
Some(local_def_id) => local_def_id,
None => panic!("DefId::expect_local: `{self:?}` isn't local"),
}
}
#[inline]
pub fn is_crate_root(self) -> bool {
self.index == CRATE_DEF_INDEX
}
#[inline]
pub fn as_crate_root(self) -> Option<CrateNum> {
self.is_crate_root().then_some(self.krate)
}
#[inline]
pub fn is_top_level_module(self) -> bool {
self.is_local() && self.is_crate_root()
}
}
impl From<LocalDefId> for DefId {
fn from(local: LocalDefId) -> DefId {
local.to_def_id()
}
}
impl<E: Encoder> Encodable<E> for DefId {
default fn encode(&self, s: &mut E) {
self.krate.encode(s);
self.index.encode(s);
}
}
impl<D: Decoder> Decodable<D> for DefId {
default fn decode(d: &mut D) -> DefId {
DefId { krate: Decodable::decode(d), index: Decodable::decode(d) }
}
}
pub fn default_def_id_debug(def_id: DefId, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("DefId").field("krate", &def_id.krate).field("index", &def_id.index).finish()
}
pub static DEF_ID_DEBUG: AtomicRef<fn(DefId, &mut fmt::Formatter<'_>) -> fmt::Result> =
AtomicRef::new(&(default_def_id_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
impl fmt::Debug for DefId {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
(*DEF_ID_DEBUG)(*self, f)
}
}
rustc_data_structures::define_id_collections!(DefIdMap, DefIdSet, DefIdMapEntry, DefId);
/// A `LocalDefId` is equivalent to a `DefId` with `krate == LOCAL_CRATE`. Since
/// we encode this information in the type, we can ensure at compile time that
/// no `DefId`s from upstream crates get thrown into the mix. There are quite a
/// few cases where we know that only `DefId`s from the local crate are expected;
/// a `DefId` from a different crate would signify a bug somewhere. This
/// is when `LocalDefId` comes in handy.
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
pub struct LocalDefId {
pub local_def_index: DefIndex,
}
// To ensure correctness of incremental compilation,
// `LocalDefId` must not implement `Ord` or `PartialOrd`.
// See https://github.com/rust-lang/rust/issues/90317.
impl !Ord for LocalDefId {}
impl !PartialOrd for LocalDefId {}
pub const CRATE_DEF_ID: LocalDefId = LocalDefId { local_def_index: CRATE_DEF_INDEX };
impl Idx for LocalDefId {
#[inline]
fn new(idx: usize) -> Self {
LocalDefId { local_def_index: Idx::new(idx) }
}
#[inline]
fn index(self) -> usize {
self.local_def_index.index()
}
}
impl LocalDefId {
#[inline]
pub fn to_def_id(self) -> DefId {
DefId { krate: LOCAL_CRATE, index: self.local_def_index }
}
#[inline]
pub fn is_top_level_module(self) -> bool {
self == CRATE_DEF_ID
}
}
impl fmt::Debug for LocalDefId {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.to_def_id().fmt(f)
}
}
impl<E: Encoder> Encodable<E> for LocalDefId {
fn encode(&self, s: &mut E) {
self.to_def_id().encode(s);
}
}
impl<D: Decoder> Decodable<D> for LocalDefId {
fn decode(d: &mut D) -> LocalDefId {
DefId::decode(d).expect_local()
}
}
rustc_data_structures::define_id_collections!(
LocalDefIdMap,
LocalDefIdSet,
LocalDefIdMapEntry,
LocalDefId
);
impl<CTX: HashStableContext> HashStable<CTX> for DefId {
#[inline]
fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
self.to_stable_hash_key(hcx).hash_stable(hcx, hasher);
}
}
impl<CTX: HashStableContext> HashStable<CTX> for LocalDefId {
#[inline]
fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
self.to_stable_hash_key(hcx).hash_stable(hcx, hasher);
}
}
impl<CTX: HashStableContext> HashStable<CTX> for CrateNum {
#[inline]
fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
self.to_stable_hash_key(hcx).hash_stable(hcx, hasher);
}
}
impl<CTX: HashStableContext> ToStableHashKey<CTX> for DefId {
type KeyType = DefPathHash;
#[inline]
fn to_stable_hash_key(&self, hcx: &CTX) -> DefPathHash {
hcx.def_path_hash(*self)
}
}
impl<CTX: HashStableContext> ToStableHashKey<CTX> for LocalDefId {
type KeyType = DefPathHash;
#[inline]
fn to_stable_hash_key(&self, hcx: &CTX) -> DefPathHash {
hcx.def_path_hash(self.to_def_id())
}
}
impl<CTX: HashStableContext> ToStableHashKey<CTX> for CrateNum {
type KeyType = DefPathHash;
#[inline]
fn to_stable_hash_key(&self, hcx: &CTX) -> DefPathHash {
self.as_def_id().to_stable_hash_key(hcx)
}
}
macro_rules! typed_def_id {
($Name:ident, $LocalName:ident) => {
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Encodable, Decodable, HashStable_Generic)]
pub struct $Name(DefId);
impl $Name {
pub const fn new_unchecked(def_id: DefId) -> Self {
Self(def_id)
}
pub fn to_def_id(self) -> DefId {
self.into()
}
pub fn is_local(self) -> bool {
self.0.is_local()
}
pub fn as_local(self) -> Option<$LocalName> {
self.0.as_local().map($LocalName::new_unchecked)
}
}
impl From<$LocalName> for $Name {
fn from(local: $LocalName) -> Self {
Self(local.0.to_def_id())
}
}
impl From<$Name> for DefId {
fn from(typed: $Name) -> Self {
typed.0
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Encodable, Decodable, HashStable_Generic)]
pub struct $LocalName(LocalDefId);
impl !Ord for $LocalName {}
impl !PartialOrd for $LocalName {}
impl $LocalName {
pub const fn new_unchecked(def_id: LocalDefId) -> Self {
Self(def_id)
}
pub fn to_def_id(self) -> DefId {
self.0.into()
}
pub fn to_local_def_id(self) -> LocalDefId {
self.0
}
}
impl From<$LocalName> for LocalDefId {
fn from(typed: $LocalName) -> Self {
typed.0
}
}
impl From<$LocalName> for DefId {
fn from(typed: $LocalName) -> Self {
typed.0.into()
}
}
};
}
// N.B.: when adding new typed `DefId`s update the corresponding trait impls in
// `rustc_middle::dep_graph::def_node` for `DepNodeParams`.
typed_def_id! { ModDefId, LocalModDefId }
impl LocalModDefId {
pub const CRATE_DEF_ID: Self = Self::new_unchecked(CRATE_DEF_ID);
}
impl ModDefId {
pub fn is_top_level_module(self) -> bool {
self.0.is_top_level_module()
}
}
impl LocalModDefId {
pub fn is_top_level_module(self) -> bool {
self.0.is_top_level_module()
}
}