1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Machinery for hygienic macros, inspired by the `MTWT[1]` paper.
13 //! `[1]` Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler. 2012.
14 //! *Macros that work together: Compile-time bindings, partial expansion,
15 //! and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216.
16 //! DOI=10.1017/S0956796812000093 <https://doi.org/10.1017/S0956796812000093>
20 use edition::{Edition, DEFAULT_EDITION};
21 use symbol::{keywords, Symbol};
23 use serialize::{Encodable, Decodable, Encoder, Decoder};
24 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
27 /// A SyntaxContext represents a chain of macro expansions (represented by marks).
28 #[derive(Clone, Copy, PartialEq, Eq, Default, PartialOrd, Ord, Hash)]
29 pub struct SyntaxContext(u32);
31 #[derive(Copy, Clone, Debug)]
32 struct SyntaxContextData {
34 transparency: Transparency,
35 prev_ctxt: SyntaxContext,
36 // This context, but with all transparent and semi-transparent marks filtered away.
37 opaque: SyntaxContext,
38 // This context, but with all transparent marks filtered away.
39 opaque_and_semitransparent: SyntaxContext,
40 // Name of the crate to which `$crate` with this context would resolve.
41 dollar_crate_name: Symbol,
44 /// A mark is a unique id associated with a macro expansion.
45 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
48 #[derive(Clone, Debug)]
51 default_transparency: Transparency,
52 expn_info: Option<ExpnInfo>,
55 /// A property of a macro expansion that determines how identifiers
56 /// produced by that expansion are resolved.
57 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
58 pub enum Transparency {
59 /// Identifier produced by a transparent expansion is always resolved at call-site.
60 /// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this.
62 /// Identifier produced by a semi-transparent expansion may be resolved
63 /// either at call-site or at definition-site.
64 /// If it's a local variable, label or `$crate` then it's resolved at def-site.
65 /// Otherwise it's resolved at call-site.
66 /// `macro_rules` macros behave like this, built-in macros currently behave like this too,
67 /// but that's an implementation detail.
69 /// Identifier produced by an opaque expansion is always resolved at definition-site.
70 /// Def-site spans in procedural macros, identifiers from `macro` by default use this.
75 pub fn fresh(parent: Mark) -> Self {
76 HygieneData::with(|data| {
77 data.marks.push(MarkData {
79 // By default expansions behave like `macro_rules`.
80 default_transparency: Transparency::SemiTransparent,
83 Mark(data.marks.len() as u32 - 1)
87 /// The mark of the theoretical expansion that generates freshly parsed, unexpanded AST.
89 pub fn root() -> Self {
94 pub fn as_u32(self) -> u32 {
99 pub fn from_u32(raw: u32) -> Mark {
104 pub fn parent(self) -> Mark {
105 HygieneData::with(|data| data.marks[self.0 as usize].parent)
109 pub fn expn_info(self) -> Option<ExpnInfo> {
110 HygieneData::with(|data| data.marks[self.0 as usize].expn_info.clone())
114 pub fn set_expn_info(self, info: ExpnInfo) {
115 HygieneData::with(|data| data.marks[self.0 as usize].expn_info = Some(info))
119 pub fn set_default_transparency(self, transparency: Transparency) {
120 assert_ne!(self, Mark::root());
121 HygieneData::with(|data| data.marks[self.0 as usize].default_transparency = transparency)
124 pub fn is_descendant_of(mut self, ancestor: Mark) -> bool {
125 HygieneData::with(|data| {
126 while self != ancestor {
127 if self == Mark::root() {
130 self = data.marks[self.0 as usize].parent;
136 /// Computes a mark such that both input marks are descendants of (or equal to) the returned
137 /// mark. That is, the following holds:
140 /// let la = least_ancestor(a, b);
141 /// assert!(a.is_descendant_of(la))
142 /// assert!(b.is_descendant_of(la))
144 pub fn least_ancestor(mut a: Mark, mut b: Mark) -> Mark {
145 HygieneData::with(|data| {
146 // Compute the path from a to the root
147 let mut a_path = FxHashSet::<Mark>::default();
148 while a != Mark::root() {
150 a = data.marks[a.0 as usize].parent;
153 // While the path from b to the root hasn't intersected, move up the tree
154 while !a_path.contains(&b) {
155 b = data.marks[b.0 as usize].parent;
162 // Used for enabling some compatibility fallback in resolve.
164 pub fn looks_like_proc_macro_derive(self) -> bool {
165 HygieneData::with(|data| {
166 let mark_data = &data.marks[self.0 as usize];
167 if mark_data.default_transparency == Transparency::Opaque {
168 if let Some(expn_info) = &mark_data.expn_info {
169 if let ExpnFormat::MacroAttribute(name) = expn_info.format {
170 if name.as_str().starts_with("derive(") {
182 crate struct HygieneData {
183 marks: Vec<MarkData>,
184 syntax_contexts: Vec<SyntaxContextData>,
185 markings: FxHashMap<(SyntaxContext, Mark, Transparency), SyntaxContext>,
186 default_edition: Edition,
190 crate fn new() -> Self {
192 marks: vec![MarkData {
193 parent: Mark::root(),
194 // If the root is opaque, then loops searching for an opaque mark
195 // will automatically stop after reaching it.
196 default_transparency: Transparency::Opaque,
199 syntax_contexts: vec![SyntaxContextData {
200 outer_mark: Mark::root(),
201 transparency: Transparency::Opaque,
202 prev_ctxt: SyntaxContext(0),
203 opaque: SyntaxContext(0),
204 opaque_and_semitransparent: SyntaxContext(0),
205 dollar_crate_name: keywords::DollarCrate.name(),
207 markings: FxHashMap::default(),
208 default_edition: DEFAULT_EDITION,
212 fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T {
213 GLOBALS.with(|globals| f(&mut *globals.hygiene_data.borrow_mut()))
217 pub fn default_edition() -> Edition {
218 HygieneData::with(|data| data.default_edition)
221 pub fn set_default_edition(edition: Edition) {
222 HygieneData::with(|data| data.default_edition = edition);
225 pub fn clear_markings() {
226 HygieneData::with(|data| data.markings = FxHashMap::default());
230 pub const fn empty() -> Self {
234 crate fn as_u32(self) -> u32 {
238 crate fn from_u32(raw: u32) -> SyntaxContext {
242 // Allocate a new SyntaxContext with the given ExpnInfo. This is used when
243 // deserializing Spans from the incr. comp. cache.
244 // FIXME(mw): This method does not restore MarkData::parent or
245 // SyntaxContextData::prev_ctxt or SyntaxContextData::opaque. These things
246 // don't seem to be used after HIR lowering, so everything should be fine
247 // as long as incremental compilation does not kick in before that.
248 pub fn allocate_directly(expansion_info: ExpnInfo) -> Self {
249 HygieneData::with(|data| {
250 data.marks.push(MarkData {
251 parent: Mark::root(),
252 default_transparency: Transparency::SemiTransparent,
253 expn_info: Some(expansion_info),
256 let mark = Mark(data.marks.len() as u32 - 1);
258 data.syntax_contexts.push(SyntaxContextData {
260 transparency: Transparency::SemiTransparent,
261 prev_ctxt: SyntaxContext::empty(),
262 opaque: SyntaxContext::empty(),
263 opaque_and_semitransparent: SyntaxContext::empty(),
264 dollar_crate_name: keywords::DollarCrate.name(),
266 SyntaxContext(data.syntax_contexts.len() as u32 - 1)
270 /// Extend a syntax context with a given mark and default transparency for that mark.
271 pub fn apply_mark(self, mark: Mark) -> SyntaxContext {
272 assert_ne!(mark, Mark::root());
273 self.apply_mark_with_transparency(
274 mark, HygieneData::with(|data| data.marks[mark.0 as usize].default_transparency)
278 /// Extend a syntax context with a given mark and transparency
279 pub fn apply_mark_with_transparency(self, mark: Mark, transparency: Transparency)
281 assert_ne!(mark, Mark::root());
282 if transparency == Transparency::Opaque {
283 return self.apply_mark_internal(mark, transparency);
287 mark.expn_info().map_or(SyntaxContext::empty(), |info| info.call_site.ctxt());
288 let call_site_ctxt = if transparency == Transparency::SemiTransparent {
289 call_site_ctxt.modern()
291 call_site_ctxt.modern_and_legacy()
294 if call_site_ctxt == SyntaxContext::empty() {
295 return self.apply_mark_internal(mark, transparency);
298 // Otherwise, `mark` is a macros 1.0 definition and the call site is in a
299 // macros 2.0 expansion, i.e., a macros 1.0 invocation is in a macros 2.0 definition.
301 // In this case, the tokens from the macros 1.0 definition inherit the hygiene
302 // at their invocation. That is, we pretend that the macros 1.0 definition
303 // was defined at its invocation (i.e., inside the macros 2.0 definition)
304 // so that the macros 2.0 definition remains hygienic.
306 // See the example at `test/run-pass/hygiene/legacy_interaction.rs`.
307 let mut ctxt = call_site_ctxt;
308 for (mark, transparency) in self.marks() {
309 ctxt = ctxt.apply_mark_internal(mark, transparency);
311 ctxt.apply_mark_internal(mark, transparency)
314 fn apply_mark_internal(self, mark: Mark, transparency: Transparency) -> SyntaxContext {
315 HygieneData::with(|data| {
316 let syntax_contexts = &mut data.syntax_contexts;
317 let mut opaque = syntax_contexts[self.0 as usize].opaque;
318 let mut opaque_and_semitransparent =
319 syntax_contexts[self.0 as usize].opaque_and_semitransparent;
321 if transparency >= Transparency::Opaque {
322 let prev_ctxt = opaque;
323 opaque = *data.markings.entry((prev_ctxt, mark, transparency)).or_insert_with(|| {
324 let new_opaque = SyntaxContext(syntax_contexts.len() as u32);
325 syntax_contexts.push(SyntaxContextData {
330 opaque_and_semitransparent: new_opaque,
331 dollar_crate_name: keywords::DollarCrate.name(),
337 if transparency >= Transparency::SemiTransparent {
338 let prev_ctxt = opaque_and_semitransparent;
339 opaque_and_semitransparent =
340 *data.markings.entry((prev_ctxt, mark, transparency)).or_insert_with(|| {
341 let new_opaque_and_semitransparent =
342 SyntaxContext(syntax_contexts.len() as u32);
343 syntax_contexts.push(SyntaxContextData {
348 opaque_and_semitransparent: new_opaque_and_semitransparent,
349 dollar_crate_name: keywords::DollarCrate.name(),
351 new_opaque_and_semitransparent
355 let prev_ctxt = self;
356 *data.markings.entry((prev_ctxt, mark, transparency)).or_insert_with(|| {
357 let new_opaque_and_semitransparent_and_transparent =
358 SyntaxContext(syntax_contexts.len() as u32);
359 syntax_contexts.push(SyntaxContextData {
364 opaque_and_semitransparent,
365 dollar_crate_name: keywords::DollarCrate.name(),
367 new_opaque_and_semitransparent_and_transparent
372 /// Pulls a single mark off of the syntax context. This effectively moves the
373 /// context up one macro definition level. That is, if we have a nested macro
374 /// definition as follows:
384 /// and we have a SyntaxContext that is referring to something declared by an invocation
385 /// of g (call it g1), calling remove_mark will result in the SyntaxContext for the
386 /// invocation of f that created g1.
387 /// Returns the mark that was removed.
388 pub fn remove_mark(&mut self) -> Mark {
389 HygieneData::with(|data| {
390 let outer_mark = data.syntax_contexts[self.0 as usize].outer_mark;
391 *self = data.syntax_contexts[self.0 as usize].prev_ctxt;
396 pub fn marks(mut self) -> Vec<(Mark, Transparency)> {
397 HygieneData::with(|data| {
398 let mut marks = Vec::new();
399 while self != SyntaxContext::empty() {
400 let ctxt_data = &data.syntax_contexts[self.0 as usize];
401 marks.push((ctxt_data.outer_mark, ctxt_data.transparency));
402 self = ctxt_data.prev_ctxt;
409 /// Adjust this context for resolution in a scope created by the given expansion.
410 /// For example, consider the following three resolutions of `f`:
413 /// mod foo { pub fn f() {} } // `f`'s `SyntaxContext` is empty.
415 /// macro m($f:ident) {
417 /// pub fn f() {} // `f`'s `SyntaxContext` has a single `Mark` from `m`.
418 /// pub fn $f() {} // `$f`'s `SyntaxContext` is empty.
420 /// foo::f(); // `f`'s `SyntaxContext` has a single `Mark` from `m`
421 /// //^ Since `mod foo` is outside this expansion, `adjust` removes the mark from `f`,
422 /// //| and it resolves to `::foo::f`.
423 /// bar::f(); // `f`'s `SyntaxContext` has a single `Mark` from `m`
424 /// //^ Since `mod bar` not outside this expansion, `adjust` does not change `f`,
425 /// //| and it resolves to `::bar::f`.
426 /// bar::$f(); // `f`'s `SyntaxContext` is empty.
427 /// //^ Since `mod bar` is not outside this expansion, `adjust` does not change `$f`,
428 /// //| and it resolves to `::bar::$f`.
431 /// This returns the expansion whose definition scope we use to privacy check the resolution,
432 /// or `None` if we privacy check as usual (i.e., not w.r.t. a macro definition scope).
433 pub fn adjust(&mut self, expansion: Mark) -> Option<Mark> {
434 let mut scope = None;
435 while !expansion.is_descendant_of(self.outer()) {
436 scope = Some(self.remove_mark());
441 /// Adjust this context for resolution in a scope created by the given expansion
442 /// via a glob import with the given `SyntaxContext`.
447 /// macro m($i:ident) {
449 /// pub fn f() {} // `f`'s `SyntaxContext` has a single `Mark` from `m`.
450 /// pub fn $i() {} // `$i`'s `SyntaxContext` is empty.
453 /// macro n($j:ident) {
455 /// f(); // `f`'s `SyntaxContext` has a mark from `m` and a mark from `n`
456 /// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::f`.
457 /// $i(); // `$i`'s `SyntaxContext` has a mark from `n`
458 /// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::$i`.
459 /// $j(); // `$j`'s `SyntaxContext` has a mark from `m`
460 /// //^ This cannot be glob-adjusted, so this is a resolution error.
464 /// This returns `None` if the context cannot be glob-adjusted.
465 /// Otherwise, it returns the scope to use when privacy checking (see `adjust` for details).
466 pub fn glob_adjust(&mut self, expansion: Mark, mut glob_ctxt: SyntaxContext)
467 -> Option<Option<Mark>> {
468 let mut scope = None;
469 while !expansion.is_descendant_of(glob_ctxt.outer()) {
470 scope = Some(glob_ctxt.remove_mark());
471 if self.remove_mark() != scope.unwrap() {
475 if self.adjust(expansion).is_some() {
481 /// Undo `glob_adjust` if possible:
484 /// if let Some(privacy_checking_scope) = self.reverse_glob_adjust(expansion, glob_ctxt) {
485 /// assert!(self.glob_adjust(expansion, glob_ctxt) == Some(privacy_checking_scope));
488 pub fn reverse_glob_adjust(&mut self, expansion: Mark, mut glob_ctxt: SyntaxContext)
489 -> Option<Option<Mark>> {
490 if self.adjust(expansion).is_some() {
494 let mut marks = Vec::new();
495 while !expansion.is_descendant_of(glob_ctxt.outer()) {
496 marks.push(glob_ctxt.remove_mark());
499 let scope = marks.last().cloned();
500 while let Some(mark) = marks.pop() {
501 *self = self.apply_mark(mark);
507 pub fn modern(self) -> SyntaxContext {
508 HygieneData::with(|data| data.syntax_contexts[self.0 as usize].opaque)
512 pub fn modern_and_legacy(self) -> SyntaxContext {
513 HygieneData::with(|data| data.syntax_contexts[self.0 as usize].opaque_and_semitransparent)
517 pub fn outer(self) -> Mark {
518 HygieneData::with(|data| data.syntax_contexts[self.0 as usize].outer_mark)
521 pub fn dollar_crate_name(self) -> Symbol {
522 HygieneData::with(|data| data.syntax_contexts[self.0 as usize].dollar_crate_name)
525 pub fn set_dollar_crate_name(self, dollar_crate_name: Symbol) {
526 HygieneData::with(|data| {
527 let prev_dollar_crate_name = mem::replace(
528 &mut data.syntax_contexts[self.0 as usize].dollar_crate_name, dollar_crate_name
530 assert!(dollar_crate_name == prev_dollar_crate_name ||
531 prev_dollar_crate_name == keywords::DollarCrate.name(),
532 "$crate name is reset for a syntax context");
537 impl fmt::Debug for SyntaxContext {
538 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
539 write!(f, "#{}", self.0)
543 /// Extra information for tracking spans of macro and syntax sugar expansion
544 #[derive(Clone, Hash, Debug, RustcEncodable, RustcDecodable)]
545 pub struct ExpnInfo {
546 /// The location of the actual macro invocation or syntax sugar , e.g.
547 /// `let x = foo!();` or `if let Some(y) = x {}`
549 /// This may recursively refer to other macro invocations, e.g., if
550 /// `foo!()` invoked `bar!()` internally, and there was an
551 /// expression inside `bar!`; the call_site of the expression in
552 /// the expansion would point to the `bar!` invocation; that
553 /// call_site span would have its own ExpnInfo, with the call_site
554 /// pointing to the `foo!` invocation.
556 /// The span of the macro definition itself. The macro may not
557 /// have a sensible definition span (e.g., something defined
558 /// completely inside libsyntax) in which case this is None.
559 /// This span serves only informational purpose and is not used for resolution.
560 pub def_site: Option<Span>,
561 /// The format with which the macro was invoked.
562 pub format: ExpnFormat,
563 /// Whether the macro is allowed to use #[unstable]/feature-gated
564 /// features internally without forcing the whole crate to opt-in
566 pub allow_internal_unstable: bool,
567 /// Whether the macro is allowed to use `unsafe` internally
568 /// even if the user crate has `#![forbid(unsafe_code)]`.
569 pub allow_internal_unsafe: bool,
570 /// Enables the macro helper hack (`ident!(...)` -> `$crate::ident!(...)`)
571 /// for a given macro.
572 pub local_inner_macros: bool,
573 /// Edition of the crate in which the macro is defined.
574 pub edition: Edition,
577 /// The source of expansion.
578 #[derive(Clone, Hash, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
579 pub enum ExpnFormat {
580 /// e.g., #[derive(...)] <item>
581 MacroAttribute(Symbol),
582 /// e.g., `format!()`
584 /// Desugaring done by the compiler during HIR lowering.
585 CompilerDesugaring(CompilerDesugaringKind)
589 pub fn name(&self) -> Symbol {
591 ExpnFormat::MacroBang(name) | ExpnFormat::MacroAttribute(name) => name,
592 ExpnFormat::CompilerDesugaring(kind) => kind.name(),
597 /// The kind of compiler desugaring.
598 #[derive(Clone, Copy, Hash, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
599 pub enum CompilerDesugaringKind {
602 /// Desugaring of an `impl Trait` in return type position
603 /// to an `existential type Foo: Trait;` + replacing the
604 /// `impl Trait` with `Foo`.
605 ExistentialReturnType,
610 impl CompilerDesugaringKind {
611 pub fn name(self) -> Symbol {
612 Symbol::intern(match self {
613 CompilerDesugaringKind::Async => "async",
614 CompilerDesugaringKind::QuestionMark => "?",
615 CompilerDesugaringKind::TryBlock => "try block",
616 CompilerDesugaringKind::ExistentialReturnType => "existential type",
617 CompilerDesugaringKind::ForLoop => "for loop",
622 impl Encodable for SyntaxContext {
623 fn encode<E: Encoder>(&self, _: &mut E) -> Result<(), E::Error> {
624 Ok(()) // FIXME(jseyfried) intercrate hygiene
628 impl Decodable for SyntaxContext {
629 fn decode<D: Decoder>(_: &mut D) -> Result<SyntaxContext, D::Error> {
630 Ok(SyntaxContext::empty()) // FIXME(jseyfried) intercrate hygiene