1 //! Machinery for hygienic macros.
3 //! Inspired by Matthew Flatt et al., “Macros That Work Together: Compile-Time Bindings, Partial
4 //! Expansion, and Definition Contexts,” *Journal of Functional Programming* 22, no. 2
5 //! (March 1, 2012): 181–216, <https://doi.org/10.1017/S0956796812000093>.
7 // Hygiene data is stored in a global variable and accessed via TLS, which
8 // means that accesses are somewhat expensive. (`HygieneData::with`
9 // encapsulates a single access.) Therefore, on hot code paths it is worth
10 // ensuring that multiple HygieneData accesses are combined into a single
11 // `HygieneData::with`.
13 // This explains why `HygieneData`, `SyntaxContext` and `ExpnId` have interfaces
14 // with a certain amount of redundancy in them. For example,
15 // `SyntaxContext::outer_expn_data` combines `SyntaxContext::outer` and
16 // `ExpnId::expn_data` so that two `HygieneData` accesses can be performed within
17 // a single `HygieneData::with` call.
19 // It also explains why many functions appear in `HygieneData` and again in
20 // `SyntaxContext` or `ExpnId`. For example, `HygieneData::outer` and
21 // `SyntaxContext::outer` do the same thing, but the former is for use within a
22 // `HygieneData::with` call while the latter is for use outside such a call.
23 // When modifying this file it is important to understand this distinction,
24 // because getting it wrong can lead to nested `HygieneData::with` calls that
25 // trigger runtime aborts. (Fortunately these are obvious and easy to fix.)
27 use crate::edition::Edition;
28 use crate::symbol::{kw, sym, Symbol};
29 use crate::with_session_globals;
30 use crate::{HashStableContext, Span, DUMMY_SP};
32 use crate::def_id::{CrateNum, DefId, StableCrateId, CRATE_DEF_ID, LOCAL_CRATE};
33 use rustc_data_structures::fingerprint::Fingerprint;
34 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
35 use rustc_data_structures::stable_hasher::HashingControls;
36 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
37 use rustc_data_structures::sync::{Lock, Lrc};
38 use rustc_data_structures::unhash::UnhashMap;
39 use rustc_index::vec::IndexVec;
40 use rustc_macros::HashStable_Generic;
41 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
46 /// A `SyntaxContext` represents a chain of pairs `(ExpnId, Transparency)` named "marks".
47 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
48 pub struct SyntaxContext(u32);
50 #[derive(Debug, Encodable, Decodable, Clone)]
51 pub struct SyntaxContextData {
53 outer_transparency: Transparency,
54 parent: SyntaxContext,
55 /// This context, but with all transparent and semi-transparent expansions filtered away.
56 opaque: SyntaxContext,
57 /// This context, but with all transparent expansions filtered away.
58 opaque_and_semitransparent: SyntaxContext,
59 /// Name of the crate to which `$crate` with this context would resolve.
60 dollar_crate_name: Symbol,
63 rustc_index::newtype_index! {
64 /// A unique ID associated with a macro invocation and expansion.
65 pub struct ExpnIndex {
70 /// A unique ID associated with a macro invocation and expansion.
71 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
74 pub local_id: ExpnIndex,
77 impl fmt::Debug for ExpnId {
78 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
79 // Generate crate_::{{expn_}}.
80 write!(f, "{:?}::{{{{expn{}}}}}", self.krate, self.local_id.private)
84 rustc_index::newtype_index! {
85 /// A unique ID associated with a macro invocation and expansion.
86 pub struct LocalExpnId {
89 DEBUG_FORMAT = "expn{}"
93 // To ensure correctness of incremental compilation,
94 // `LocalExpnId` must not implement `Ord` or `PartialOrd`.
95 // See https://github.com/rust-lang/rust/issues/90317.
96 impl !Ord for LocalExpnId {}
97 impl !PartialOrd for LocalExpnId {}
99 /// Assert that the provided `HashStableContext` is configured with the 'default'
100 /// `HashingControls`. We should always have bailed out before getting to here
101 /// with a non-default mode. With this check in place, we can avoid the need
102 /// to maintain separate versions of `ExpnData` hashes for each permutation
103 /// of `HashingControls` settings.
104 fn assert_default_hashing_controls<CTX: HashStableContext>(ctx: &CTX, msg: &str) {
105 match ctx.hashing_controls() {
106 // Note that we require that `hash_spans` be set according to the global
107 // `-Z incremental-ignore-spans` option. Normally, this option is disabled,
108 // which will cause us to require that this method always be called with `Span` hashing
110 HashingControls { hash_spans }
111 if hash_spans == !ctx.debug_opts_incremental_ignore_spans() => {}
112 other => panic!("Attempted hashing of {msg} with non-default HashingControls: {:?}", other),
116 /// A unique hash value associated to an expansion.
117 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Encodable, Decodable, HashStable_Generic)]
118 pub struct ExpnHash(Fingerprint);
121 /// Returns the [StableCrateId] identifying the crate this [ExpnHash]
124 pub fn stable_crate_id(self) -> StableCrateId {
125 StableCrateId(self.0.as_value().0)
128 /// Returns the crate-local part of the [ExpnHash].
132 pub fn local_hash(self) -> u64 {
137 pub fn is_root(self) -> bool {
138 self.0 == Fingerprint::ZERO
141 /// Builds a new [ExpnHash] with the given [StableCrateId] and
142 /// `local_hash`, where `local_hash` must be unique within its crate.
143 fn new(stable_crate_id: StableCrateId, local_hash: u64) -> ExpnHash {
144 ExpnHash(Fingerprint::new(stable_crate_id.0, local_hash))
148 /// A property of a macro expansion that determines how identifiers
149 /// produced by that expansion are resolved.
150 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug, Encodable, Decodable)]
151 #[derive(HashStable_Generic)]
152 pub enum Transparency {
153 /// Identifier produced by a transparent expansion is always resolved at call-site.
154 /// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this.
156 /// Identifier produced by a semi-transparent expansion may be resolved
157 /// either at call-site or at definition-site.
158 /// If it's a local variable, label or `$crate` then it's resolved at def-site.
159 /// Otherwise it's resolved at call-site.
160 /// `macro_rules` macros behave like this, built-in macros currently behave like this too,
161 /// but that's an implementation detail.
163 /// Identifier produced by an opaque expansion is always resolved at definition-site.
164 /// Def-site spans in procedural macros, identifiers from `macro` by default use this.
169 /// The ID of the theoretical expansion that generates freshly parsed, unexpanded AST.
170 pub const ROOT: LocalExpnId = LocalExpnId::from_u32(0);
173 pub fn from_raw(idx: ExpnIndex) -> LocalExpnId {
174 LocalExpnId::from_u32(idx.as_u32())
178 pub fn as_raw(self) -> ExpnIndex {
179 ExpnIndex::from_u32(self.as_u32())
182 pub fn fresh_empty() -> LocalExpnId {
183 HygieneData::with(|data| {
184 let expn_id = data.local_expn_data.push(None);
185 let _eid = data.local_expn_hashes.push(ExpnHash(Fingerprint::ZERO));
186 debug_assert_eq!(expn_id, _eid);
191 pub fn fresh(mut expn_data: ExpnData, ctx: impl HashStableContext) -> LocalExpnId {
192 debug_assert_eq!(expn_data.parent.krate, LOCAL_CRATE);
193 let expn_hash = update_disambiguator(&mut expn_data, ctx);
194 HygieneData::with(|data| {
195 let expn_id = data.local_expn_data.push(Some(expn_data));
196 let _eid = data.local_expn_hashes.push(expn_hash);
197 debug_assert_eq!(expn_id, _eid);
198 let _old_id = data.expn_hash_to_expn_id.insert(expn_hash, expn_id.to_expn_id());
199 debug_assert!(_old_id.is_none());
205 pub fn expn_hash(self) -> ExpnHash {
206 HygieneData::with(|data| data.local_expn_hash(self))
210 pub fn expn_data(self) -> ExpnData {
211 HygieneData::with(|data| data.local_expn_data(self).clone())
215 pub fn to_expn_id(self) -> ExpnId {
216 ExpnId { krate: LOCAL_CRATE, local_id: self.as_raw() }
220 pub fn set_expn_data(self, mut expn_data: ExpnData, ctx: impl HashStableContext) {
221 debug_assert_eq!(expn_data.parent.krate, LOCAL_CRATE);
222 let expn_hash = update_disambiguator(&mut expn_data, ctx);
223 HygieneData::with(|data| {
224 let old_expn_data = &mut data.local_expn_data[self];
225 assert!(old_expn_data.is_none(), "expansion data is reset for an expansion ID");
226 *old_expn_data = Some(expn_data);
227 debug_assert_eq!(data.local_expn_hashes[self].0, Fingerprint::ZERO);
228 data.local_expn_hashes[self] = expn_hash;
229 let _old_id = data.expn_hash_to_expn_id.insert(expn_hash, self.to_expn_id());
230 debug_assert!(_old_id.is_none());
235 pub fn is_descendant_of(self, ancestor: LocalExpnId) -> bool {
236 self.to_expn_id().is_descendant_of(ancestor.to_expn_id())
239 /// `expn_id.outer_expn_is_descendant_of(ctxt)` is equivalent to but faster than
240 /// `expn_id.is_descendant_of(ctxt.outer_expn())`.
242 pub fn outer_expn_is_descendant_of(self, ctxt: SyntaxContext) -> bool {
243 self.to_expn_id().outer_expn_is_descendant_of(ctxt)
246 /// Returns span for the macro which originally caused this expansion to happen.
248 /// Stops backtracing at include! boundary.
250 pub fn expansion_cause(self) -> Option<Span> {
251 self.to_expn_id().expansion_cause()
256 pub fn parent(self) -> LocalExpnId {
257 self.expn_data().parent.as_local().unwrap()
262 /// The ID of the theoretical expansion that generates freshly parsed, unexpanded AST.
263 /// Invariant: we do not create any ExpnId with local_id == 0 and krate != 0.
264 pub const fn root() -> ExpnId {
265 ExpnId { krate: LOCAL_CRATE, local_id: ExpnIndex::from_u32(0) }
269 pub fn expn_hash(self) -> ExpnHash {
270 HygieneData::with(|data| data.expn_hash(self))
274 pub fn from_hash(hash: ExpnHash) -> Option<ExpnId> {
275 HygieneData::with(|data| data.expn_hash_to_expn_id.get(&hash).copied())
279 pub fn as_local(self) -> Option<LocalExpnId> {
280 if self.krate == LOCAL_CRATE { Some(LocalExpnId::from_raw(self.local_id)) } else { None }
285 pub fn expect_local(self) -> LocalExpnId {
286 self.as_local().unwrap()
290 pub fn expn_data(self) -> ExpnData {
291 HygieneData::with(|data| data.expn_data(self).clone())
295 pub fn is_descendant_of(self, ancestor: ExpnId) -> bool {
296 // a few "fast path" cases to avoid locking HygieneData
297 if ancestor == ExpnId::root() || ancestor == self {
300 if ancestor.krate != self.krate {
303 HygieneData::with(|data| data.is_descendant_of(self, ancestor))
306 /// `expn_id.outer_expn_is_descendant_of(ctxt)` is equivalent to but faster than
307 /// `expn_id.is_descendant_of(ctxt.outer_expn())`.
308 pub fn outer_expn_is_descendant_of(self, ctxt: SyntaxContext) -> bool {
309 HygieneData::with(|data| data.is_descendant_of(self, data.outer_expn(ctxt)))
312 /// Returns span for the macro which originally caused this expansion to happen.
314 /// Stops backtracing at include! boundary.
315 pub fn expansion_cause(mut self) -> Option<Span> {
316 let mut last_macro = None;
318 let expn_data = self.expn_data();
319 // Stop going up the backtrace once include! is encountered
320 if expn_data.is_root()
321 || expn_data.kind == ExpnKind::Macro(MacroKind::Bang, sym::include)
325 self = expn_data.call_site.ctxt().outer_expn();
326 last_macro = Some(expn_data.call_site);
333 pub struct HygieneData {
334 /// Each expansion should have an associated expansion data, but sometimes there's a delay
335 /// between creation of an expansion ID and obtaining its data (e.g. macros are collected
336 /// first and then resolved later), so we use an `Option` here.
337 local_expn_data: IndexVec<LocalExpnId, Option<ExpnData>>,
338 local_expn_hashes: IndexVec<LocalExpnId, ExpnHash>,
339 /// Data and hash information from external crates. We may eventually want to remove these
340 /// maps, and fetch the information directly from the other crate's metadata like DefIds do.
341 foreign_expn_data: FxHashMap<ExpnId, ExpnData>,
342 foreign_expn_hashes: FxHashMap<ExpnId, ExpnHash>,
343 expn_hash_to_expn_id: UnhashMap<ExpnHash, ExpnId>,
344 syntax_context_data: Vec<SyntaxContextData>,
345 syntax_context_map: FxHashMap<(SyntaxContext, ExpnId, Transparency), SyntaxContext>,
346 /// Maps the `local_hash` of an `ExpnData` to the next disambiguator value.
347 /// This is used by `update_disambiguator` to keep track of which `ExpnData`s
348 /// would have collisions without a disambiguator.
349 /// The keys of this map are always computed with `ExpnData.disambiguator`
351 expn_data_disambiguators: FxHashMap<u64, u32>,
355 crate fn new(edition: Edition) -> Self {
356 let root_data = ExpnData::default(
360 Some(CRATE_DEF_ID.to_def_id()),
365 local_expn_data: IndexVec::from_elem_n(Some(root_data), 1),
366 local_expn_hashes: IndexVec::from_elem_n(ExpnHash(Fingerprint::ZERO), 1),
367 foreign_expn_data: FxHashMap::default(),
368 foreign_expn_hashes: FxHashMap::default(),
369 expn_hash_to_expn_id: std::iter::once((ExpnHash(Fingerprint::ZERO), ExpnId::root()))
371 syntax_context_data: vec![SyntaxContextData {
372 outer_expn: ExpnId::root(),
373 outer_transparency: Transparency::Opaque,
374 parent: SyntaxContext(0),
375 opaque: SyntaxContext(0),
376 opaque_and_semitransparent: SyntaxContext(0),
377 dollar_crate_name: kw::DollarCrate,
379 syntax_context_map: FxHashMap::default(),
380 expn_data_disambiguators: FxHashMap::default(),
384 pub fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T {
385 with_session_globals(|session_globals| f(&mut *session_globals.hygiene_data.borrow_mut()))
389 fn local_expn_hash(&self, expn_id: LocalExpnId) -> ExpnHash {
390 self.local_expn_hashes[expn_id]
394 fn expn_hash(&self, expn_id: ExpnId) -> ExpnHash {
395 match expn_id.as_local() {
396 Some(expn_id) => self.local_expn_hashes[expn_id],
397 None => self.foreign_expn_hashes[&expn_id],
401 fn local_expn_data(&self, expn_id: LocalExpnId) -> &ExpnData {
402 self.local_expn_data[expn_id].as_ref().expect("no expansion data for an expansion ID")
405 fn expn_data(&self, expn_id: ExpnId) -> &ExpnData {
406 if let Some(expn_id) = expn_id.as_local() {
407 self.local_expn_data[expn_id].as_ref().expect("no expansion data for an expansion ID")
409 &self.foreign_expn_data[&expn_id]
413 fn is_descendant_of(&self, mut expn_id: ExpnId, ancestor: ExpnId) -> bool {
414 // a couple "fast path" cases to avoid traversing parents in the loop below
415 if ancestor == ExpnId::root() {
418 if expn_id.krate != ancestor.krate {
422 if expn_id == ancestor {
425 if expn_id == ExpnId::root() {
428 expn_id = self.expn_data(expn_id).parent;
432 fn normalize_to_macros_2_0(&self, ctxt: SyntaxContext) -> SyntaxContext {
433 self.syntax_context_data[ctxt.0 as usize].opaque
436 fn normalize_to_macro_rules(&self, ctxt: SyntaxContext) -> SyntaxContext {
437 self.syntax_context_data[ctxt.0 as usize].opaque_and_semitransparent
440 fn outer_expn(&self, ctxt: SyntaxContext) -> ExpnId {
441 self.syntax_context_data[ctxt.0 as usize].outer_expn
444 fn outer_mark(&self, ctxt: SyntaxContext) -> (ExpnId, Transparency) {
445 let data = &self.syntax_context_data[ctxt.0 as usize];
446 (data.outer_expn, data.outer_transparency)
449 fn parent_ctxt(&self, ctxt: SyntaxContext) -> SyntaxContext {
450 self.syntax_context_data[ctxt.0 as usize].parent
453 fn remove_mark(&self, ctxt: &mut SyntaxContext) -> (ExpnId, Transparency) {
454 let outer_mark = self.outer_mark(*ctxt);
455 *ctxt = self.parent_ctxt(*ctxt);
459 fn marks(&self, mut ctxt: SyntaxContext) -> Vec<(ExpnId, Transparency)> {
460 let mut marks = Vec::new();
461 while ctxt != SyntaxContext::root() {
462 debug!("marks: getting parent of {:?}", ctxt);
463 marks.push(self.outer_mark(ctxt));
464 ctxt = self.parent_ctxt(ctxt);
470 fn walk_chain(&self, mut span: Span, to: SyntaxContext) -> Span {
471 debug!("walk_chain({:?}, {:?})", span, to);
472 debug!("walk_chain: span ctxt = {:?}", span.ctxt());
473 while span.from_expansion() && span.ctxt() != to {
474 let outer_expn = self.outer_expn(span.ctxt());
475 debug!("walk_chain({:?}): outer_expn={:?}", span, outer_expn);
476 let expn_data = self.expn_data(outer_expn);
477 debug!("walk_chain({:?}): expn_data={:?}", span, expn_data);
478 span = expn_data.call_site;
483 fn adjust(&self, ctxt: &mut SyntaxContext, expn_id: ExpnId) -> Option<ExpnId> {
484 let mut scope = None;
485 while !self.is_descendant_of(expn_id, self.outer_expn(*ctxt)) {
486 scope = Some(self.remove_mark(ctxt).0);
495 transparency: Transparency,
497 assert_ne!(expn_id, ExpnId::root());
498 if transparency == Transparency::Opaque {
499 return self.apply_mark_internal(ctxt, expn_id, transparency);
502 let call_site_ctxt = self.expn_data(expn_id).call_site.ctxt();
503 let mut call_site_ctxt = if transparency == Transparency::SemiTransparent {
504 self.normalize_to_macros_2_0(call_site_ctxt)
506 self.normalize_to_macro_rules(call_site_ctxt)
509 if call_site_ctxt == SyntaxContext::root() {
510 return self.apply_mark_internal(ctxt, expn_id, transparency);
513 // Otherwise, `expn_id` is a macros 1.0 definition and the call site is in a
514 // macros 2.0 expansion, i.e., a macros 1.0 invocation is in a macros 2.0 definition.
516 // In this case, the tokens from the macros 1.0 definition inherit the hygiene
517 // at their invocation. That is, we pretend that the macros 1.0 definition
518 // was defined at its invocation (i.e., inside the macros 2.0 definition)
519 // so that the macros 2.0 definition remains hygienic.
521 // See the example at `test/ui/hygiene/legacy_interaction.rs`.
522 for (expn_id, transparency) in self.marks(ctxt) {
523 call_site_ctxt = self.apply_mark_internal(call_site_ctxt, expn_id, transparency);
525 self.apply_mark_internal(call_site_ctxt, expn_id, transparency)
528 fn apply_mark_internal(
532 transparency: Transparency,
534 let syntax_context_data = &mut self.syntax_context_data;
535 let mut opaque = syntax_context_data[ctxt.0 as usize].opaque;
536 let mut opaque_and_semitransparent =
537 syntax_context_data[ctxt.0 as usize].opaque_and_semitransparent;
539 if transparency >= Transparency::Opaque {
543 .entry((parent, expn_id, transparency))
545 let new_opaque = SyntaxContext(syntax_context_data.len() as u32);
546 syntax_context_data.push(SyntaxContextData {
548 outer_transparency: transparency,
551 opaque_and_semitransparent: new_opaque,
552 dollar_crate_name: kw::DollarCrate,
558 if transparency >= Transparency::SemiTransparent {
559 let parent = opaque_and_semitransparent;
560 opaque_and_semitransparent = *self
562 .entry((parent, expn_id, transparency))
564 let new_opaque_and_semitransparent =
565 SyntaxContext(syntax_context_data.len() as u32);
566 syntax_context_data.push(SyntaxContextData {
568 outer_transparency: transparency,
571 opaque_and_semitransparent: new_opaque_and_semitransparent,
572 dollar_crate_name: kw::DollarCrate,
574 new_opaque_and_semitransparent
579 *self.syntax_context_map.entry((parent, expn_id, transparency)).or_insert_with(|| {
580 let new_opaque_and_semitransparent_and_transparent =
581 SyntaxContext(syntax_context_data.len() as u32);
582 syntax_context_data.push(SyntaxContextData {
584 outer_transparency: transparency,
587 opaque_and_semitransparent,
588 dollar_crate_name: kw::DollarCrate,
590 new_opaque_and_semitransparent_and_transparent
595 pub fn clear_syntax_context_map() {
596 HygieneData::with(|data| data.syntax_context_map = FxHashMap::default());
599 pub fn walk_chain(span: Span, to: SyntaxContext) -> Span {
600 HygieneData::with(|data| data.walk_chain(span, to))
603 pub fn update_dollar_crate_names(mut get_name: impl FnMut(SyntaxContext) -> Symbol) {
604 // The new contexts that need updating are at the end of the list and have `$crate` as a name.
605 let (len, to_update) = HygieneData::with(|data| {
607 data.syntax_context_data.len(),
608 data.syntax_context_data
611 .take_while(|scdata| scdata.dollar_crate_name == kw::DollarCrate)
615 // The callback must be called from outside of the `HygieneData` lock,
616 // since it will try to acquire it too.
617 let range_to_update = len - to_update..len;
619 range_to_update.clone().map(|idx| get_name(SyntaxContext::from_u32(idx as u32))).collect();
620 HygieneData::with(|data| {
621 range_to_update.zip(names).for_each(|(idx, name)| {
622 data.syntax_context_data[idx].dollar_crate_name = name;
627 pub fn debug_hygiene_data(verbose: bool) -> String {
628 HygieneData::with(|data| {
630 format!("{:#?}", data)
632 let mut s = String::from("");
633 s.push_str("Expansions:");
634 let mut debug_expn_data = |(id, expn_data): (&ExpnId, &ExpnData)| {
636 "\n{:?}: parent: {:?}, call_site_ctxt: {:?}, def_site_ctxt: {:?}, kind: {:?}",
639 expn_data.call_site.ctxt(),
640 expn_data.def_site.ctxt(),
644 data.local_expn_data.iter_enumerated().for_each(|(id, expn_data)| {
645 let expn_data = expn_data.as_ref().expect("no expansion data for an expansion ID");
646 debug_expn_data((&id.to_expn_id(), expn_data))
648 // Sort the hash map for more reproducible output.
649 let mut foreign_expn_data: Vec<_> = data.foreign_expn_data.iter().collect();
650 foreign_expn_data.sort_by_key(|(id, _)| (id.krate, id.local_id));
651 foreign_expn_data.into_iter().for_each(debug_expn_data);
652 s.push_str("\n\nSyntaxContexts:");
653 data.syntax_context_data.iter().enumerate().for_each(|(id, ctxt)| {
655 "\n#{}: parent: {:?}, outer_mark: ({:?}, {:?})",
656 id, ctxt.parent, ctxt.outer_expn, ctxt.outer_transparency,
666 pub const fn root() -> Self {
671 crate fn as_u32(self) -> u32 {
676 crate fn from_u32(raw: u32) -> SyntaxContext {
680 /// Extend a syntax context with a given expansion and transparency.
681 crate fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext {
682 HygieneData::with(|data| data.apply_mark(self, expn_id, transparency))
685 /// Pulls a single mark off of the syntax context. This effectively moves the
686 /// context up one macro definition level. That is, if we have a nested macro
687 /// definition as follows:
697 /// and we have a SyntaxContext that is referring to something declared by an invocation
698 /// of g (call it g1), calling remove_mark will result in the SyntaxContext for the
699 /// invocation of f that created g1.
700 /// Returns the mark that was removed.
701 pub fn remove_mark(&mut self) -> ExpnId {
702 HygieneData::with(|data| data.remove_mark(self).0)
705 pub fn marks(self) -> Vec<(ExpnId, Transparency)> {
706 HygieneData::with(|data| data.marks(self))
709 /// Adjust this context for resolution in a scope created by the given expansion.
710 /// For example, consider the following three resolutions of `f`:
713 /// mod foo { pub fn f() {} } // `f`'s `SyntaxContext` is empty.
715 /// macro m($f:ident) {
717 /// pub fn f() {} // `f`'s `SyntaxContext` has a single `ExpnId` from `m`.
718 /// pub fn $f() {} // `$f`'s `SyntaxContext` is empty.
720 /// foo::f(); // `f`'s `SyntaxContext` has a single `ExpnId` from `m`
721 /// //^ Since `mod foo` is outside this expansion, `adjust` removes the mark from `f`,
722 /// //| and it resolves to `::foo::f`.
723 /// bar::f(); // `f`'s `SyntaxContext` has a single `ExpnId` from `m`
724 /// //^ Since `mod bar` not outside this expansion, `adjust` does not change `f`,
725 /// //| and it resolves to `::bar::f`.
726 /// bar::$f(); // `f`'s `SyntaxContext` is empty.
727 /// //^ Since `mod bar` is not outside this expansion, `adjust` does not change `$f`,
728 /// //| and it resolves to `::bar::$f`.
731 /// This returns the expansion whose definition scope we use to privacy check the resolution,
732 /// or `None` if we privacy check as usual (i.e., not w.r.t. a macro definition scope).
733 pub fn adjust(&mut self, expn_id: ExpnId) -> Option<ExpnId> {
734 HygieneData::with(|data| data.adjust(self, expn_id))
737 /// Like `SyntaxContext::adjust`, but also normalizes `self` to macros 2.0.
738 pub fn normalize_to_macros_2_0_and_adjust(&mut self, expn_id: ExpnId) -> Option<ExpnId> {
739 HygieneData::with(|data| {
740 *self = data.normalize_to_macros_2_0(*self);
741 data.adjust(self, expn_id)
745 /// Adjust this context for resolution in a scope created by the given expansion
746 /// via a glob import with the given `SyntaxContext`.
751 /// macro m($i:ident) {
753 /// pub fn f() {} // `f`'s `SyntaxContext` has a single `ExpnId` from `m`.
754 /// pub fn $i() {} // `$i`'s `SyntaxContext` is empty.
757 /// macro n($j:ident) {
759 /// f(); // `f`'s `SyntaxContext` has a mark from `m` and a mark from `n`
760 /// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::f`.
761 /// $i(); // `$i`'s `SyntaxContext` has a mark from `n`
762 /// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::$i`.
763 /// $j(); // `$j`'s `SyntaxContext` has a mark from `m`
764 /// //^ This cannot be glob-adjusted, so this is a resolution error.
768 /// This returns `None` if the context cannot be glob-adjusted.
769 /// Otherwise, it returns the scope to use when privacy checking (see `adjust` for details).
770 pub fn glob_adjust(&mut self, expn_id: ExpnId, glob_span: Span) -> Option<Option<ExpnId>> {
771 HygieneData::with(|data| {
772 let mut scope = None;
773 let mut glob_ctxt = data.normalize_to_macros_2_0(glob_span.ctxt());
774 while !data.is_descendant_of(expn_id, data.outer_expn(glob_ctxt)) {
775 scope = Some(data.remove_mark(&mut glob_ctxt).0);
776 if data.remove_mark(self).0 != scope.unwrap() {
780 if data.adjust(self, expn_id).is_some() {
787 /// Undo `glob_adjust` if possible:
790 /// if let Some(privacy_checking_scope) = self.reverse_glob_adjust(expansion, glob_ctxt) {
791 /// assert!(self.glob_adjust(expansion, glob_ctxt) == Some(privacy_checking_scope));
794 pub fn reverse_glob_adjust(
798 ) -> Option<Option<ExpnId>> {
799 HygieneData::with(|data| {
800 if data.adjust(self, expn_id).is_some() {
804 let mut glob_ctxt = data.normalize_to_macros_2_0(glob_span.ctxt());
805 let mut marks = Vec::new();
806 while !data.is_descendant_of(expn_id, data.outer_expn(glob_ctxt)) {
807 marks.push(data.remove_mark(&mut glob_ctxt));
810 let scope = marks.last().map(|mark| mark.0);
811 while let Some((expn_id, transparency)) = marks.pop() {
812 *self = data.apply_mark(*self, expn_id, transparency);
818 pub fn hygienic_eq(self, other: SyntaxContext, expn_id: ExpnId) -> bool {
819 HygieneData::with(|data| {
820 let mut self_normalized = data.normalize_to_macros_2_0(self);
821 data.adjust(&mut self_normalized, expn_id);
822 self_normalized == data.normalize_to_macros_2_0(other)
827 pub fn normalize_to_macros_2_0(self) -> SyntaxContext {
828 HygieneData::with(|data| data.normalize_to_macros_2_0(self))
832 pub fn normalize_to_macro_rules(self) -> SyntaxContext {
833 HygieneData::with(|data| data.normalize_to_macro_rules(self))
837 pub fn outer_expn(self) -> ExpnId {
838 HygieneData::with(|data| data.outer_expn(self))
841 /// `ctxt.outer_expn_data()` is equivalent to but faster than
842 /// `ctxt.outer_expn().expn_data()`.
844 pub fn outer_expn_data(self) -> ExpnData {
845 HygieneData::with(|data| data.expn_data(data.outer_expn(self)).clone())
849 pub fn outer_mark(self) -> (ExpnId, Transparency) {
850 HygieneData::with(|data| data.outer_mark(self))
853 pub fn dollar_crate_name(self) -> Symbol {
854 HygieneData::with(|data| data.syntax_context_data[self.0 as usize].dollar_crate_name)
857 pub fn edition(self) -> Edition {
858 HygieneData::with(|data| data.expn_data(data.outer_expn(self)).edition)
862 impl fmt::Debug for SyntaxContext {
863 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
864 write!(f, "#{}", self.0)
869 /// Creates a fresh expansion with given properties.
870 /// Expansions are normally created by macros, but in some cases expansions are created for
871 /// other compiler-generated code to set per-span properties like allowed unstable features.
872 /// The returned span belongs to the created expansion and has the new properties,
873 /// but its location is inherited from the current span.
874 pub fn fresh_expansion(self, expn_id: LocalExpnId) -> Span {
875 HygieneData::with(|data| {
876 self.with_ctxt(data.apply_mark(
877 SyntaxContext::root(),
878 expn_id.to_expn_id(),
879 Transparency::Transparent,
884 /// Reuses the span but adds information like the kind of the desugaring and features that are
885 /// allowed inside this span.
886 pub fn mark_with_reason(
888 allow_internal_unstable: Option<Lrc<[Symbol]>>,
889 reason: DesugaringKind,
891 ctx: impl HashStableContext,
893 let expn_data = ExpnData {
894 allow_internal_unstable,
895 ..ExpnData::default(ExpnKind::Desugaring(reason), self, edition, None, None)
897 let expn_id = LocalExpnId::fresh(expn_data, ctx);
898 self.fresh_expansion(expn_id)
902 /// A subset of properties from both macro definition and macro call available through global data.
903 /// Avoid using this if you have access to the original definition or call structures.
904 #[derive(Clone, Debug, Encodable, Decodable, HashStable_Generic)]
905 pub struct ExpnData {
906 // --- The part unique to each expansion.
907 /// The kind of this expansion - macro or compiler desugaring.
909 /// The expansion that produced this expansion.
911 /// The location of the actual macro invocation or syntax sugar , e.g.
912 /// `let x = foo!();` or `if let Some(y) = x {}`
914 /// This may recursively refer to other macro invocations, e.g., if
915 /// `foo!()` invoked `bar!()` internally, and there was an
916 /// expression inside `bar!`; the call_site of the expression in
917 /// the expansion would point to the `bar!` invocation; that
918 /// call_site span would have its own ExpnData, with the call_site
919 /// pointing to the `foo!` invocation.
921 /// Used to force two `ExpnData`s to have different `Fingerprint`s.
922 /// Due to macro expansion, it's possible to end up with two `ExpnId`s
923 /// that have identical `ExpnData`s. This violates the contract of `HashStable`
924 /// - the two `ExpnId`s are not equal, but their `Fingerprint`s are equal
925 /// (since the numerical `ExpnId` value is not considered by the `HashStable`
928 /// The `disambiguator` field is set by `update_disambiguator` when two distinct
929 /// `ExpnId`s would end up with the same `Fingerprint`. Since `ExpnData` includes
930 /// a `krate` field, this value only needs to be unique within a single crate.
933 // --- The part specific to the macro/desugaring definition.
934 // --- It may be reasonable to share this part between expansions with the same definition,
935 // --- but such sharing is known to bring some minor inconveniences without also bringing
936 // --- noticeable perf improvements (PR #62898).
937 /// The span of the macro definition (possibly dummy).
938 /// This span serves only informational purpose and is not used for resolution.
940 /// List of `#[unstable]`/feature-gated features that the macro is allowed to use
941 /// internally without forcing the whole crate to opt-in
943 pub allow_internal_unstable: Option<Lrc<[Symbol]>>,
944 /// Whether the macro is allowed to use `unsafe` internally
945 /// even if the user crate has `#![forbid(unsafe_code)]`.
946 pub allow_internal_unsafe: bool,
947 /// Enables the macro helper hack (`ident!(...)` -> `$crate::ident!(...)`)
948 /// for a given macro.
949 pub local_inner_macros: bool,
950 /// Edition of the crate in which the macro is defined.
951 pub edition: Edition,
952 /// The `DefId` of the macro being invoked,
953 /// if this `ExpnData` corresponds to a macro invocation
954 pub macro_def_id: Option<DefId>,
955 /// The normal module (`mod`) in which the expanded macro was defined.
956 pub parent_module: Option<DefId>,
959 impl !PartialEq for ExpnData {}
960 impl !Hash for ExpnData {}
968 allow_internal_unstable: Option<Lrc<[Symbol]>>,
969 allow_internal_unsafe: bool,
970 local_inner_macros: bool,
972 macro_def_id: Option<DefId>,
973 parent_module: Option<DefId>,
980 allow_internal_unstable,
981 allow_internal_unsafe,
990 /// Constructs expansion data with default properties.
995 macro_def_id: Option<DefId>,
996 parent_module: Option<DefId>,
1000 parent: ExpnId::root(),
1003 allow_internal_unstable: None,
1004 allow_internal_unsafe: false,
1005 local_inner_macros: false,
1013 pub fn allow_unstable(
1017 allow_internal_unstable: Lrc<[Symbol]>,
1018 macro_def_id: Option<DefId>,
1019 parent_module: Option<DefId>,
1022 allow_internal_unstable: Some(allow_internal_unstable),
1023 ..ExpnData::default(kind, call_site, edition, macro_def_id, parent_module)
1028 pub fn is_root(&self) -> bool {
1029 matches!(self.kind, ExpnKind::Root)
1033 fn hash_expn(&self, ctx: &mut impl HashStableContext) -> u64 {
1034 let mut hasher = StableHasher::new();
1035 self.hash_stable(ctx, &mut hasher);
1041 #[derive(Clone, Debug, PartialEq, Encodable, Decodable, HashStable_Generic)]
1043 /// No expansion, aka root expansion. Only `ExpnId::root()` has this kind.
1045 /// Expansion produced by a macro.
1046 Macro(MacroKind, Symbol),
1047 /// Transform done by the compiler on the AST.
1049 /// Desugaring done by the compiler during HIR lowering.
1050 Desugaring(DesugaringKind),
1056 pub fn descr(&self) -> String {
1058 ExpnKind::Root => kw::PathRoot.to_string(),
1059 ExpnKind::Macro(macro_kind, name) => match macro_kind {
1060 MacroKind::Bang => format!("{}!", name),
1061 MacroKind::Attr => format!("#[{}]", name),
1062 MacroKind::Derive => format!("#[derive({})]", name),
1064 ExpnKind::AstPass(kind) => kind.descr().to_string(),
1065 ExpnKind::Desugaring(kind) => format!("desugaring of {}", kind.descr()),
1066 ExpnKind::Inlined => "inlined source".to_string(),
1071 /// The kind of macro invocation or definition.
1072 #[derive(Clone, Copy, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
1073 #[derive(HashStable_Generic)]
1074 pub enum MacroKind {
1075 /// A bang macro `foo!()`.
1077 /// An attribute macro `#[foo]`.
1079 /// A derive macro `#[derive(Foo)]`
1084 pub fn descr(self) -> &'static str {
1086 MacroKind::Bang => "macro",
1087 MacroKind::Attr => "attribute macro",
1088 MacroKind::Derive => "derive macro",
1092 pub fn descr_expected(self) -> &'static str {
1094 MacroKind::Attr => "attribute",
1099 pub fn article(self) -> &'static str {
1101 MacroKind::Attr => "an",
1107 /// The kind of AST transform.
1108 #[derive(Clone, Copy, Debug, PartialEq, Encodable, Decodable, HashStable_Generic)]
1116 pub fn descr(self) -> &'static str {
1118 AstPass::StdImports => "standard library imports",
1119 AstPass::TestHarness => "test harness",
1120 AstPass::ProcMacroHarness => "proc macro harness",
1125 /// The kind of compiler desugaring.
1126 #[derive(Clone, Copy, PartialEq, Debug, Encodable, Decodable, HashStable_Generic)]
1127 pub enum DesugaringKind {
1128 /// We desugar `if c { i } else { e }` to `match $ExprKind::Use(c) { true => i, _ => e }`.
1129 /// However, we do not want to blame `c` for unreachability but rather say that `i`
1130 /// is unreachable. This desugaring kind allows us to avoid blaming `c`.
1131 /// This also applies to `while` loops.
1135 /// Desugaring of an `impl Trait` in return type position
1136 /// to an `type Foo = impl Trait;` and replacing the
1137 /// `impl Trait` with `Foo`.
1146 impl DesugaringKind {
1147 /// The description wording should combine well with "desugaring of {}".
1148 pub fn descr(self) -> &'static str {
1150 DesugaringKind::CondTemporary => "`if` or `while` condition",
1151 DesugaringKind::Async => "`async` block or function",
1152 DesugaringKind::Await => "`await` expression",
1153 DesugaringKind::QuestionMark => "operator `?`",
1154 DesugaringKind::TryBlock => "`try` block",
1155 DesugaringKind::OpaqueTy => "`impl Trait`",
1156 DesugaringKind::ForLoop => "`for` loop",
1157 DesugaringKind::LetElse => "`let...else`",
1158 DesugaringKind::WhileLoop => "`while` loop",
1164 pub struct HygieneEncodeContext {
1165 /// All `SyntaxContexts` for which we have written `SyntaxContextData` into crate metadata.
1166 /// This is `None` after we finish encoding `SyntaxContexts`, to ensure
1167 /// that we don't accidentally try to encode any more `SyntaxContexts`
1168 serialized_ctxts: Lock<FxHashSet<SyntaxContext>>,
1169 /// The `SyntaxContexts` that we have serialized (e.g. as a result of encoding `Spans`)
1170 /// in the most recent 'round' of serializing. Serializing `SyntaxContextData`
1171 /// may cause us to serialize more `SyntaxContext`s, so serialize in a loop
1172 /// until we reach a fixed point.
1173 latest_ctxts: Lock<FxHashSet<SyntaxContext>>,
1175 serialized_expns: Lock<FxHashSet<ExpnId>>,
1177 latest_expns: Lock<FxHashSet<ExpnId>>,
1180 impl HygieneEncodeContext {
1181 /// Record the fact that we need to serialize the corresponding `ExpnData`.
1182 pub fn schedule_expn_data_for_encoding(&self, expn: ExpnId) {
1183 if !self.serialized_expns.lock().contains(&expn) {
1184 self.latest_expns.lock().insert(expn);
1188 pub fn encode<T, R>(
1191 mut encode_ctxt: impl FnMut(&mut T, u32, &SyntaxContextData) -> Result<(), R>,
1192 mut encode_expn: impl FnMut(&mut T, ExpnId, &ExpnData, ExpnHash) -> Result<(), R>,
1193 ) -> Result<(), R> {
1194 // When we serialize a `SyntaxContextData`, we may end up serializing
1195 // a `SyntaxContext` that we haven't seen before
1196 while !self.latest_ctxts.lock().is_empty() || !self.latest_expns.lock().is_empty() {
1198 "encode_hygiene: Serializing a round of {:?} SyntaxContextDatas: {:?}",
1199 self.latest_ctxts.lock().len(),
1203 // Consume the current round of SyntaxContexts.
1204 // Drop the lock() temporary early
1205 let latest_ctxts = { std::mem::take(&mut *self.latest_ctxts.lock()) };
1207 // It's fine to iterate over a HashMap, because the serialization
1208 // of the table that we insert data into doesn't depend on insertion
1210 for_all_ctxts_in(latest_ctxts.into_iter(), |index, ctxt, data| {
1211 if self.serialized_ctxts.lock().insert(ctxt) {
1212 encode_ctxt(encoder, index, data)?;
1217 let latest_expns = { std::mem::take(&mut *self.latest_expns.lock()) };
1219 for_all_expns_in(latest_expns.into_iter(), |expn, data, hash| {
1220 if self.serialized_expns.lock().insert(expn) {
1221 encode_expn(encoder, expn, data, hash)?;
1226 debug!("encode_hygiene: Done serializing SyntaxContextData");
1232 /// Additional information used to assist in decoding hygiene data
1233 pub struct HygieneDecodeContext {
1234 // Maps serialized `SyntaxContext` ids to a `SyntaxContext` in the current
1235 // global `HygieneData`. When we deserialize a `SyntaxContext`, we need to create
1236 // a new id in the global `HygieneData`. This map tracks the ID we end up picking,
1237 // so that multiple occurrences of the same serialized id are decoded to the same
1239 remapped_ctxts: Lock<Vec<Option<SyntaxContext>>>,
1242 /// Register an expansion which has been decoded from the on-disk-cache for the local crate.
1243 pub fn register_local_expn_id(data: ExpnData, hash: ExpnHash) -> ExpnId {
1244 HygieneData::with(|hygiene_data| {
1245 let expn_id = hygiene_data.local_expn_data.next_index();
1246 hygiene_data.local_expn_data.push(Some(data));
1247 let _eid = hygiene_data.local_expn_hashes.push(hash);
1248 debug_assert_eq!(expn_id, _eid);
1250 let expn_id = expn_id.to_expn_id();
1252 let _old_id = hygiene_data.expn_hash_to_expn_id.insert(hash, expn_id);
1253 debug_assert!(_old_id.is_none());
1258 /// Register an expansion which has been decoded from the metadata of a foreign crate.
1259 pub fn register_expn_id(
1261 local_id: ExpnIndex,
1265 debug_assert!(data.parent == ExpnId::root() || krate == data.parent.krate);
1266 let expn_id = ExpnId { krate, local_id };
1267 HygieneData::with(|hygiene_data| {
1268 let _old_data = hygiene_data.foreign_expn_data.insert(expn_id, data);
1269 debug_assert!(_old_data.is_none());
1270 let _old_hash = hygiene_data.foreign_expn_hashes.insert(expn_id, hash);
1271 debug_assert!(_old_hash.is_none());
1272 let _old_id = hygiene_data.expn_hash_to_expn_id.insert(hash, expn_id);
1273 debug_assert!(_old_id.is_none());
1278 /// Decode an expansion from the metadata of a foreign crate.
1279 pub fn decode_expn_id(
1282 decode_data: impl FnOnce(ExpnId) -> (ExpnData, ExpnHash),
1285 debug!("decode_expn_id: deserialized root");
1286 return ExpnId::root();
1289 let index = ExpnIndex::from_u32(index);
1291 // This function is used to decode metadata, so it cannot decode information about LOCAL_CRATE.
1292 debug_assert_ne!(krate, LOCAL_CRATE);
1293 let expn_id = ExpnId { krate, local_id: index };
1295 // Fast path if the expansion has already been decoded.
1296 if HygieneData::with(|hygiene_data| hygiene_data.foreign_expn_data.contains_key(&expn_id)) {
1300 // Don't decode the data inside `HygieneData::with`, since we need to recursively decode
1302 let (expn_data, hash) = decode_data(expn_id);
1304 register_expn_id(krate, index, expn_data, hash)
1307 // Decodes `SyntaxContext`, using the provided `HygieneDecodeContext`
1308 // to track which `SyntaxContext`s we have already decoded.
1309 // The provided closure will be invoked to deserialize a `SyntaxContextData`
1310 // if we haven't already seen the id of the `SyntaxContext` we are deserializing.
1311 pub fn decode_syntax_context<D: Decoder, F: FnOnce(&mut D, u32) -> SyntaxContextData>(
1313 context: &HygieneDecodeContext,
1315 ) -> SyntaxContext {
1316 let raw_id: u32 = Decodable::decode(d);
1318 debug!("decode_syntax_context: deserialized root");
1319 // The root is special
1320 return SyntaxContext::root();
1323 let outer_ctxts = &context.remapped_ctxts;
1325 // Ensure that the lock() temporary is dropped early
1327 if let Some(ctxt) = outer_ctxts.lock().get(raw_id as usize).copied().flatten() {
1332 // Allocate and store SyntaxContext id *before* calling the decoder function,
1333 // as the SyntaxContextData may reference itself.
1334 let new_ctxt = HygieneData::with(|hygiene_data| {
1335 let new_ctxt = SyntaxContext(hygiene_data.syntax_context_data.len() as u32);
1336 // Push a dummy SyntaxContextData to ensure that nobody else can get the
1337 // same ID as us. This will be overwritten after call `decode_Data`
1338 hygiene_data.syntax_context_data.push(SyntaxContextData {
1339 outer_expn: ExpnId::root(),
1340 outer_transparency: Transparency::Transparent,
1341 parent: SyntaxContext::root(),
1342 opaque: SyntaxContext::root(),
1343 opaque_and_semitransparent: SyntaxContext::root(),
1344 dollar_crate_name: kw::Empty,
1346 let mut ctxts = outer_ctxts.lock();
1347 let new_len = raw_id as usize + 1;
1348 if ctxts.len() < new_len {
1349 ctxts.resize(new_len, None);
1351 ctxts[raw_id as usize] = Some(new_ctxt);
1356 // Don't try to decode data while holding the lock, since we need to
1357 // be able to recursively decode a SyntaxContext
1358 let mut ctxt_data = decode_data(d, raw_id);
1359 // Reset `dollar_crate_name` so that it will be updated by `update_dollar_crate_names`
1360 // We don't care what the encoding crate set this to - we want to resolve it
1361 // from the perspective of the current compilation session
1362 ctxt_data.dollar_crate_name = kw::DollarCrate;
1364 // Overwrite the dummy data with our decoded SyntaxContextData
1365 HygieneData::with(|hygiene_data| {
1366 let dummy = std::mem::replace(
1367 &mut hygiene_data.syntax_context_data[new_ctxt.as_u32() as usize],
1370 // Make sure nothing weird happening while `decode_data` was running
1371 assert_eq!(dummy.dollar_crate_name, kw::Empty);
1377 fn for_all_ctxts_in<E, F: FnMut(u32, SyntaxContext, &SyntaxContextData) -> Result<(), E>>(
1378 ctxts: impl Iterator<Item = SyntaxContext>,
1380 ) -> Result<(), E> {
1381 let all_data: Vec<_> = HygieneData::with(|data| {
1382 ctxts.map(|ctxt| (ctxt, data.syntax_context_data[ctxt.0 as usize].clone())).collect()
1384 for (ctxt, data) in all_data.into_iter() {
1385 f(ctxt.0, ctxt, &data)?;
1390 fn for_all_expns_in<E>(
1391 expns: impl Iterator<Item = ExpnId>,
1392 mut f: impl FnMut(ExpnId, &ExpnData, ExpnHash) -> Result<(), E>,
1393 ) -> Result<(), E> {
1394 let all_data: Vec<_> = HygieneData::with(|data| {
1395 expns.map(|expn| (expn, data.expn_data(expn).clone(), data.expn_hash(expn))).collect()
1397 for (expn, data, hash) in all_data.into_iter() {
1398 f(expn, &data, hash)?;
1403 impl<E: Encoder> Encodable<E> for LocalExpnId {
1404 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
1405 self.to_expn_id().encode(e)
1409 impl<E: Encoder> Encodable<E> for ExpnId {
1410 default fn encode(&self, _: &mut E) -> Result<(), E::Error> {
1411 panic!("cannot encode `ExpnId` with `{}`", std::any::type_name::<E>());
1415 impl<D: Decoder> Decodable<D> for LocalExpnId {
1416 fn decode(d: &mut D) -> Self {
1417 ExpnId::expect_local(ExpnId::decode(d))
1421 impl<D: Decoder> Decodable<D> for ExpnId {
1422 default fn decode(_: &mut D) -> Self {
1423 panic!("cannot decode `ExpnId` with `{}`", std::any::type_name::<D>());
1427 pub fn raw_encode_syntax_context<E: Encoder>(
1428 ctxt: SyntaxContext,
1429 context: &HygieneEncodeContext,
1431 ) -> Result<(), E::Error> {
1432 if !context.serialized_ctxts.lock().contains(&ctxt) {
1433 context.latest_ctxts.lock().insert(ctxt);
1438 impl<E: Encoder> Encodable<E> for SyntaxContext {
1439 default fn encode(&self, _: &mut E) -> Result<(), E::Error> {
1440 panic!("cannot encode `SyntaxContext` with `{}`", std::any::type_name::<E>());
1444 impl<D: Decoder> Decodable<D> for SyntaxContext {
1445 default fn decode(_: &mut D) -> Self {
1446 panic!("cannot decode `SyntaxContext` with `{}`", std::any::type_name::<D>());
1450 /// Updates the `disambiguator` field of the corresponding `ExpnData`
1451 /// such that the `Fingerprint` of the `ExpnData` does not collide with
1452 /// any other `ExpnIds`.
1454 /// This method is called only when an `ExpnData` is first associated
1455 /// with an `ExpnId` (when the `ExpnId` is initially constructed, or via
1456 /// `set_expn_data`). It is *not* called for foreign `ExpnId`s deserialized
1457 /// from another crate's metadata - since `ExpnHash` includes the stable crate id,
1458 /// collisions are only possible between `ExpnId`s within the same crate.
1459 fn update_disambiguator(expn_data: &mut ExpnData, mut ctx: impl HashStableContext) -> ExpnHash {
1460 // This disambiguator should not have been set yet.
1462 expn_data.disambiguator, 0,
1463 "Already set disambiguator for ExpnData: {:?}",
1466 assert_default_hashing_controls(&ctx, "ExpnData (disambiguator)");
1467 let mut expn_hash = expn_data.hash_expn(&mut ctx);
1469 let disambiguator = HygieneData::with(|data| {
1470 // If this is the first ExpnData with a given hash, then keep our
1471 // disambiguator at 0 (the default u32 value)
1472 let disambig = data.expn_data_disambiguators.entry(expn_hash).or_default();
1473 let disambiguator = *disambig;
1478 if disambiguator != 0 {
1479 debug!("Set disambiguator for expn_data={:?} expn_hash={:?}", expn_data, expn_hash);
1481 expn_data.disambiguator = disambiguator;
1482 expn_hash = expn_data.hash_expn(&mut ctx);
1484 // Verify that the new disambiguator makes the hash unique
1485 #[cfg(debug_assertions)]
1486 HygieneData::with(|data| {
1488 data.expn_data_disambiguators.get(&expn_hash),
1490 "Hash collision after disambiguator update!",
1495 ExpnHash::new(ctx.def_path_hash(LOCAL_CRATE.as_def_id()).stable_crate_id(), expn_hash)
1498 impl<CTX: HashStableContext> HashStable<CTX> for SyntaxContext {
1499 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
1500 const TAG_EXPANSION: u8 = 0;
1501 const TAG_NO_EXPANSION: u8 = 1;
1503 if *self == SyntaxContext::root() {
1504 TAG_NO_EXPANSION.hash_stable(ctx, hasher);
1506 TAG_EXPANSION.hash_stable(ctx, hasher);
1507 let (expn_id, transparency) = self.outer_mark();
1508 expn_id.hash_stable(ctx, hasher);
1509 transparency.hash_stable(ctx, hasher);
1514 impl<CTX: HashStableContext> HashStable<CTX> for ExpnId {
1515 fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
1516 assert_default_hashing_controls(ctx, "ExpnId");
1517 let hash = if *self == ExpnId::root() {
1518 // Avoid fetching TLS storage for a trivial often-used value.
1524 hash.hash_stable(ctx, hasher);