| //! Machinery for hygienic macros, inspired by the `MTWT[1]` paper. |
| //! |
| //! `[1]` Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler. 2012. |
| //! *Macros that work together: Compile-time bindings, partial expansion, |
| //! and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216. |
| //! DOI=10.1017/S0956796812000093 <https://doi.org/10.1017/S0956796812000093> |
| |
| // Hygiene data is stored in a global variable and accessed via TLS, which |
| // means that accesses are somewhat expensive. (`HygieneData::with` |
| // encapsulates a single access.) Therefore, on hot code paths it is worth |
| // ensuring that multiple HygieneData accesses are combined into a single |
| // `HygieneData::with`. |
| // |
| // This explains why `HygieneData`, `SyntaxContext` and `ExpnId` have interfaces |
| // with a certain amount of redundancy in them. For example, |
| // `SyntaxContext::outer_expn_data` combines `SyntaxContext::outer` and |
| // `ExpnId::expn_data` so that two `HygieneData` accesses can be performed within |
| // a single `HygieneData::with` call. |
| // |
| // It also explains why many functions appear in `HygieneData` and again in |
| // `SyntaxContext` or `ExpnId`. For example, `HygieneData::outer` and |
| // `SyntaxContext::outer` do the same thing, but the former is for use within a |
| // `HygieneData::with` call while the latter is for use outside such a call. |
| // When modifying this file it is important to understand this distinction, |
| // because getting it wrong can lead to nested `HygieneData::with` calls that |
| // trigger runtime aborts. (Fortunately these are obvious and easy to fix.) |
| |
| use crate::GLOBALS; |
| use crate::{Span, DUMMY_SP}; |
| use crate::edition::Edition; |
| use crate::symbol::{kw, Symbol}; |
| |
| use rustc_serialize::{Encodable, Decodable, Encoder, Decoder}; |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc_data_structures::sync::Lrc; |
| use std::fmt; |
| |
| /// A `SyntaxContext` represents a chain of pairs `(ExpnId, Transparency)` named "marks". |
| #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] |
| pub struct SyntaxContext(u32); |
| |
| #[derive(Debug)] |
| struct SyntaxContextData { |
| outer_expn: ExpnId, |
| outer_transparency: Transparency, |
| parent: SyntaxContext, |
| /// This context, but with all transparent and semi-transparent expansions filtered away. |
| opaque: SyntaxContext, |
| /// This context, but with all transparent expansions filtered away. |
| opaque_and_semitransparent: SyntaxContext, |
| /// Name of the crate to which `$crate` with this context would resolve. |
| dollar_crate_name: Symbol, |
| } |
| |
| /// A unique ID associated with a macro invocation and expansion. |
| #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)] |
| pub struct ExpnId(u32); |
| |
| /// A property of a macro expansion that determines how identifiers |
| /// produced by that expansion are resolved. |
| #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug, RustcEncodable, RustcDecodable)] |
| pub enum Transparency { |
| /// Identifier produced by a transparent expansion is always resolved at call-site. |
| /// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this. |
| Transparent, |
| /// Identifier produced by a semi-transparent expansion may be resolved |
| /// either at call-site or at definition-site. |
| /// If it's a local variable, label or `$crate` then it's resolved at def-site. |
| /// Otherwise it's resolved at call-site. |
| /// `macro_rules` macros behave like this, built-in macros currently behave like this too, |
| /// but that's an implementation detail. |
| SemiTransparent, |
| /// Identifier produced by an opaque expansion is always resolved at definition-site. |
| /// Def-site spans in procedural macros, identifiers from `macro` by default use this. |
| Opaque, |
| } |
| |
| impl ExpnId { |
| pub fn fresh(expn_data: Option<ExpnData>) -> Self { |
| HygieneData::with(|data| data.fresh_expn(expn_data)) |
| } |
| |
| /// The ID of the theoretical expansion that generates freshly parsed, unexpanded AST. |
| #[inline] |
| pub fn root() -> Self { |
| ExpnId(0) |
| } |
| |
| #[inline] |
| pub fn as_u32(self) -> u32 { |
| self.0 |
| } |
| |
| #[inline] |
| pub fn from_u32(raw: u32) -> ExpnId { |
| ExpnId(raw) |
| } |
| |
| #[inline] |
| pub fn expn_data(self) -> ExpnData { |
| HygieneData::with(|data| data.expn_data(self).clone()) |
| } |
| |
| #[inline] |
| pub fn set_expn_data(self, expn_data: ExpnData) { |
| HygieneData::with(|data| { |
| let old_expn_data = &mut data.expn_data[self.0 as usize]; |
| assert!(old_expn_data.is_none(), "expansion data is reset for an expansion ID"); |
| *old_expn_data = Some(expn_data); |
| }) |
| } |
| |
| pub fn is_descendant_of(self, ancestor: ExpnId) -> bool { |
| HygieneData::with(|data| data.is_descendant_of(self, ancestor)) |
| } |
| |
| /// `expn_id.outer_expn_is_descendant_of(ctxt)` is equivalent to but faster than |
| /// `expn_id.is_descendant_of(ctxt.outer_expn())`. |
| pub fn outer_expn_is_descendant_of(self, ctxt: SyntaxContext) -> bool { |
| HygieneData::with(|data| data.is_descendant_of(self, data.outer_expn(ctxt))) |
| } |
| } |
| |
| #[derive(Debug)] |
| crate struct HygieneData { |
| /// Each expansion should have an associated expansion data, but sometimes there's a delay |
| /// between creation of an expansion ID and obtaining its data (e.g. macros are collected |
| /// first and then resolved later), so we use an `Option` here. |
| expn_data: Vec<Option<ExpnData>>, |
| syntax_context_data: Vec<SyntaxContextData>, |
| syntax_context_map: FxHashMap<(SyntaxContext, ExpnId, Transparency), SyntaxContext>, |
| } |
| |
| impl HygieneData { |
| crate fn new(edition: Edition) -> Self { |
| HygieneData { |
| expn_data: vec![Some(ExpnData::default(ExpnKind::Root, DUMMY_SP, edition))], |
| syntax_context_data: vec![SyntaxContextData { |
| outer_expn: ExpnId::root(), |
| outer_transparency: Transparency::Opaque, |
| parent: SyntaxContext(0), |
| opaque: SyntaxContext(0), |
| opaque_and_semitransparent: SyntaxContext(0), |
| dollar_crate_name: kw::DollarCrate, |
| }], |
| syntax_context_map: FxHashMap::default(), |
| } |
| } |
| |
| fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T { |
| GLOBALS.with(|globals| f(&mut *globals.hygiene_data.borrow_mut())) |
| } |
| |
| fn fresh_expn(&mut self, expn_data: Option<ExpnData>) -> ExpnId { |
| self.expn_data.push(expn_data); |
| ExpnId(self.expn_data.len() as u32 - 1) |
| } |
| |
| fn expn_data(&self, expn_id: ExpnId) -> &ExpnData { |
| self.expn_data[expn_id.0 as usize].as_ref() |
| .expect("no expansion data for an expansion ID") |
| } |
| |
| fn is_descendant_of(&self, mut expn_id: ExpnId, ancestor: ExpnId) -> bool { |
| while expn_id != ancestor { |
| if expn_id == ExpnId::root() { |
| return false; |
| } |
| expn_id = self.expn_data(expn_id).parent; |
| } |
| true |
| } |
| |
| fn modern(&self, ctxt: SyntaxContext) -> SyntaxContext { |
| self.syntax_context_data[ctxt.0 as usize].opaque |
| } |
| |
| fn modern_and_legacy(&self, ctxt: SyntaxContext) -> SyntaxContext { |
| self.syntax_context_data[ctxt.0 as usize].opaque_and_semitransparent |
| } |
| |
| fn outer_expn(&self, ctxt: SyntaxContext) -> ExpnId { |
| self.syntax_context_data[ctxt.0 as usize].outer_expn |
| } |
| |
| fn outer_mark(&self, ctxt: SyntaxContext) -> (ExpnId, Transparency) { |
| let data = &self.syntax_context_data[ctxt.0 as usize]; |
| (data.outer_expn, data.outer_transparency) |
| } |
| |
| fn parent_ctxt(&self, ctxt: SyntaxContext) -> SyntaxContext { |
| self.syntax_context_data[ctxt.0 as usize].parent |
| } |
| |
| fn remove_mark(&self, ctxt: &mut SyntaxContext) -> (ExpnId, Transparency) { |
| let outer_mark = self.outer_mark(*ctxt); |
| *ctxt = self.parent_ctxt(*ctxt); |
| outer_mark |
| } |
| |
| fn marks(&self, mut ctxt: SyntaxContext) -> Vec<(ExpnId, Transparency)> { |
| let mut marks = Vec::new(); |
| while ctxt != SyntaxContext::root() { |
| marks.push(self.outer_mark(ctxt)); |
| ctxt = self.parent_ctxt(ctxt); |
| } |
| marks.reverse(); |
| marks |
| } |
| |
| fn walk_chain(&self, mut span: Span, to: SyntaxContext) -> Span { |
| while span.from_expansion() && span.ctxt() != to { |
| span = self.expn_data(self.outer_expn(span.ctxt())).call_site; |
| } |
| span |
| } |
| |
| fn adjust(&self, ctxt: &mut SyntaxContext, expn_id: ExpnId) -> Option<ExpnId> { |
| let mut scope = None; |
| while !self.is_descendant_of(expn_id, self.outer_expn(*ctxt)) { |
| scope = Some(self.remove_mark(ctxt).0); |
| } |
| scope |
| } |
| |
| fn apply_mark( |
| &mut self, ctxt: SyntaxContext, expn_id: ExpnId, transparency: Transparency |
| ) -> SyntaxContext { |
| assert_ne!(expn_id, ExpnId::root()); |
| if transparency == Transparency::Opaque { |
| return self.apply_mark_internal(ctxt, expn_id, transparency); |
| } |
| |
| let call_site_ctxt = self.expn_data(expn_id).call_site.ctxt(); |
| let mut call_site_ctxt = if transparency == Transparency::SemiTransparent { |
| self.modern(call_site_ctxt) |
| } else { |
| self.modern_and_legacy(call_site_ctxt) |
| }; |
| |
| if call_site_ctxt == SyntaxContext::root() { |
| return self.apply_mark_internal(ctxt, expn_id, transparency); |
| } |
| |
| // Otherwise, `expn_id` is a macros 1.0 definition and the call site is in a |
| // macros 2.0 expansion, i.e., a macros 1.0 invocation is in a macros 2.0 definition. |
| // |
| // In this case, the tokens from the macros 1.0 definition inherit the hygiene |
| // at their invocation. That is, we pretend that the macros 1.0 definition |
| // was defined at its invocation (i.e., inside the macros 2.0 definition) |
| // so that the macros 2.0 definition remains hygienic. |
| // |
| // See the example at `test/ui/hygiene/legacy_interaction.rs`. |
| for (expn_id, transparency) in self.marks(ctxt) { |
| call_site_ctxt = self.apply_mark_internal(call_site_ctxt, expn_id, transparency); |
| } |
| self.apply_mark_internal(call_site_ctxt, expn_id, transparency) |
| } |
| |
| fn apply_mark_internal( |
| &mut self, ctxt: SyntaxContext, expn_id: ExpnId, transparency: Transparency |
| ) -> SyntaxContext { |
| let syntax_context_data = &mut self.syntax_context_data; |
| let mut opaque = syntax_context_data[ctxt.0 as usize].opaque; |
| let mut opaque_and_semitransparent = |
| syntax_context_data[ctxt.0 as usize].opaque_and_semitransparent; |
| |
| if transparency >= Transparency::Opaque { |
| let parent = opaque; |
| opaque = *self.syntax_context_map.entry((parent, expn_id, transparency)) |
| .or_insert_with(|| { |
| let new_opaque = SyntaxContext(syntax_context_data.len() as u32); |
| syntax_context_data.push(SyntaxContextData { |
| outer_expn: expn_id, |
| outer_transparency: transparency, |
| parent, |
| opaque: new_opaque, |
| opaque_and_semitransparent: new_opaque, |
| dollar_crate_name: kw::DollarCrate, |
| }); |
| new_opaque |
| }); |
| } |
| |
| if transparency >= Transparency::SemiTransparent { |
| let parent = opaque_and_semitransparent; |
| opaque_and_semitransparent = |
| *self.syntax_context_map.entry((parent, expn_id, transparency)) |
| .or_insert_with(|| { |
| let new_opaque_and_semitransparent = |
| SyntaxContext(syntax_context_data.len() as u32); |
| syntax_context_data.push(SyntaxContextData { |
| outer_expn: expn_id, |
| outer_transparency: transparency, |
| parent, |
| opaque, |
| opaque_and_semitransparent: new_opaque_and_semitransparent, |
| dollar_crate_name: kw::DollarCrate, |
| }); |
| new_opaque_and_semitransparent |
| }); |
| } |
| |
| let parent = ctxt; |
| *self.syntax_context_map.entry((parent, expn_id, transparency)).or_insert_with(|| { |
| let new_opaque_and_semitransparent_and_transparent = |
| SyntaxContext(syntax_context_data.len() as u32); |
| syntax_context_data.push(SyntaxContextData { |
| outer_expn: expn_id, |
| outer_transparency: transparency, |
| parent, |
| opaque, |
| opaque_and_semitransparent, |
| dollar_crate_name: kw::DollarCrate, |
| }); |
| new_opaque_and_semitransparent_and_transparent |
| }) |
| } |
| } |
| |
| pub fn clear_syntax_context_map() { |
| HygieneData::with(|data| data.syntax_context_map = FxHashMap::default()); |
| } |
| |
| pub fn walk_chain(span: Span, to: SyntaxContext) -> Span { |
| HygieneData::with(|data| data.walk_chain(span, to)) |
| } |
| |
| pub fn update_dollar_crate_names(mut get_name: impl FnMut(SyntaxContext) -> Symbol) { |
| // The new contexts that need updating are at the end of the list and have `$crate` as a name. |
| let (len, to_update) = HygieneData::with(|data| ( |
| data.syntax_context_data.len(), |
| data.syntax_context_data.iter().rev() |
| .take_while(|scdata| scdata.dollar_crate_name == kw::DollarCrate).count() |
| )); |
| // The callback must be called from outside of the `HygieneData` lock, |
| // since it will try to acquire it too. |
| let range_to_update = len - to_update .. len; |
| let names: Vec<_> = |
| range_to_update.clone().map(|idx| get_name(SyntaxContext::from_u32(idx as u32))).collect(); |
| HygieneData::with(|data| range_to_update.zip(names.into_iter()).for_each(|(idx, name)| { |
| data.syntax_context_data[idx].dollar_crate_name = name; |
| })) |
| } |
| |
| impl SyntaxContext { |
| #[inline] |
| pub const fn root() -> Self { |
| SyntaxContext(0) |
| } |
| |
| #[inline] |
| crate fn as_u32(self) -> u32 { |
| self.0 |
| } |
| |
| #[inline] |
| crate fn from_u32(raw: u32) -> SyntaxContext { |
| SyntaxContext(raw) |
| } |
| |
| /// Extend a syntax context with a given expansion and transparency. |
| crate fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext { |
| HygieneData::with(|data| data.apply_mark(self, expn_id, transparency)) |
| } |
| |
| /// Pulls a single mark off of the syntax context. This effectively moves the |
| /// context up one macro definition level. That is, if we have a nested macro |
| /// definition as follows: |
| /// |
| /// ```rust |
| /// macro_rules! f { |
| /// macro_rules! g { |
| /// ... |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// and we have a SyntaxContext that is referring to something declared by an invocation |
| /// of g (call it g1), calling remove_mark will result in the SyntaxContext for the |
| /// invocation of f that created g1. |
| /// Returns the mark that was removed. |
| pub fn remove_mark(&mut self) -> ExpnId { |
| HygieneData::with(|data| data.remove_mark(self).0) |
| } |
| |
| pub fn marks(self) -> Vec<(ExpnId, Transparency)> { |
| HygieneData::with(|data| data.marks(self)) |
| } |
| |
| /// Adjust this context for resolution in a scope created by the given expansion. |
| /// For example, consider the following three resolutions of `f`: |
| /// |
| /// ```rust |
| /// mod foo { pub fn f() {} } // `f`'s `SyntaxContext` is empty. |
| /// m!(f); |
| /// macro m($f:ident) { |
| /// mod bar { |
| /// pub fn f() {} // `f`'s `SyntaxContext` has a single `ExpnId` from `m`. |
| /// pub fn $f() {} // `$f`'s `SyntaxContext` is empty. |
| /// } |
| /// foo::f(); // `f`'s `SyntaxContext` has a single `ExpnId` from `m` |
| /// //^ Since `mod foo` is outside this expansion, `adjust` removes the mark from `f`, |
| /// //| and it resolves to `::foo::f`. |
| /// bar::f(); // `f`'s `SyntaxContext` has a single `ExpnId` from `m` |
| /// //^ Since `mod bar` not outside this expansion, `adjust` does not change `f`, |
| /// //| and it resolves to `::bar::f`. |
| /// bar::$f(); // `f`'s `SyntaxContext` is empty. |
| /// //^ Since `mod bar` is not outside this expansion, `adjust` does not change `$f`, |
| /// //| and it resolves to `::bar::$f`. |
| /// } |
| /// ``` |
| /// This returns the expansion whose definition scope we use to privacy check the resolution, |
| /// or `None` if we privacy check as usual (i.e., not w.r.t. a macro definition scope). |
| pub fn adjust(&mut self, expn_id: ExpnId) -> Option<ExpnId> { |
| HygieneData::with(|data| data.adjust(self, expn_id)) |
| } |
| |
| /// Like `SyntaxContext::adjust`, but also modernizes `self`. |
| pub fn modernize_and_adjust(&mut self, expn_id: ExpnId) -> Option<ExpnId> { |
| HygieneData::with(|data| { |
| *self = data.modern(*self); |
| data.adjust(self, expn_id) |
| }) |
| } |
| |
| /// Adjust this context for resolution in a scope created by the given expansion |
| /// via a glob import with the given `SyntaxContext`. |
| /// For example: |
| /// |
| /// ```rust |
| /// m!(f); |
| /// macro m($i:ident) { |
| /// mod foo { |
| /// pub fn f() {} // `f`'s `SyntaxContext` has a single `ExpnId` from `m`. |
| /// pub fn $i() {} // `$i`'s `SyntaxContext` is empty. |
| /// } |
| /// n(f); |
| /// macro n($j:ident) { |
| /// use foo::*; |
| /// f(); // `f`'s `SyntaxContext` has a mark from `m` and a mark from `n` |
| /// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::f`. |
| /// $i(); // `$i`'s `SyntaxContext` has a mark from `n` |
| /// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::$i`. |
| /// $j(); // `$j`'s `SyntaxContext` has a mark from `m` |
| /// //^ This cannot be glob-adjusted, so this is a resolution error. |
| /// } |
| /// } |
| /// ``` |
| /// This returns `None` if the context cannot be glob-adjusted. |
| /// Otherwise, it returns the scope to use when privacy checking (see `adjust` for details). |
| pub fn glob_adjust(&mut self, expn_id: ExpnId, glob_span: Span) -> Option<Option<ExpnId>> { |
| HygieneData::with(|data| { |
| let mut scope = None; |
| let mut glob_ctxt = data.modern(glob_span.ctxt()); |
| while !data.is_descendant_of(expn_id, data.outer_expn(glob_ctxt)) { |
| scope = Some(data.remove_mark(&mut glob_ctxt).0); |
| if data.remove_mark(self).0 != scope.unwrap() { |
| return None; |
| } |
| } |
| if data.adjust(self, expn_id).is_some() { |
| return None; |
| } |
| Some(scope) |
| }) |
| } |
| |
| /// Undo `glob_adjust` if possible: |
| /// |
| /// ```rust |
| /// if let Some(privacy_checking_scope) = self.reverse_glob_adjust(expansion, glob_ctxt) { |
| /// assert!(self.glob_adjust(expansion, glob_ctxt) == Some(privacy_checking_scope)); |
| /// } |
| /// ``` |
| pub fn reverse_glob_adjust(&mut self, expn_id: ExpnId, glob_span: Span) |
| -> Option<Option<ExpnId>> { |
| HygieneData::with(|data| { |
| if data.adjust(self, expn_id).is_some() { |
| return None; |
| } |
| |
| let mut glob_ctxt = data.modern(glob_span.ctxt()); |
| let mut marks = Vec::new(); |
| while !data.is_descendant_of(expn_id, data.outer_expn(glob_ctxt)) { |
| marks.push(data.remove_mark(&mut glob_ctxt)); |
| } |
| |
| let scope = marks.last().map(|mark| mark.0); |
| while let Some((expn_id, transparency)) = marks.pop() { |
| *self = data.apply_mark(*self, expn_id, transparency); |
| } |
| Some(scope) |
| }) |
| } |
| |
| pub fn hygienic_eq(self, other: SyntaxContext, expn_id: ExpnId) -> bool { |
| HygieneData::with(|data| { |
| let mut self_modern = data.modern(self); |
| data.adjust(&mut self_modern, expn_id); |
| self_modern == data.modern(other) |
| }) |
| } |
| |
| #[inline] |
| pub fn modern(self) -> SyntaxContext { |
| HygieneData::with(|data| data.modern(self)) |
| } |
| |
| #[inline] |
| pub fn modern_and_legacy(self) -> SyntaxContext { |
| HygieneData::with(|data| data.modern_and_legacy(self)) |
| } |
| |
| #[inline] |
| pub fn outer_expn(self) -> ExpnId { |
| HygieneData::with(|data| data.outer_expn(self)) |
| } |
| |
| /// `ctxt.outer_expn_data()` is equivalent to but faster than |
| /// `ctxt.outer_expn().expn_data()`. |
| #[inline] |
| pub fn outer_expn_data(self) -> ExpnData { |
| HygieneData::with(|data| data.expn_data(data.outer_expn(self)).clone()) |
| } |
| |
| #[inline] |
| pub fn outer_mark_with_data(self) -> (ExpnId, Transparency, ExpnData) { |
| HygieneData::with(|data| { |
| let (expn_id, transparency) = data.outer_mark(self); |
| (expn_id, transparency, data.expn_data(expn_id).clone()) |
| }) |
| } |
| |
| pub fn dollar_crate_name(self) -> Symbol { |
| HygieneData::with(|data| data.syntax_context_data[self.0 as usize].dollar_crate_name) |
| } |
| } |
| |
| impl fmt::Debug for SyntaxContext { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| write!(f, "#{}", self.0) |
| } |
| } |
| |
| impl Span { |
| /// Creates a fresh expansion with given properties. |
| /// Expansions are normally created by macros, but in some cases expansions are created for |
| /// other compiler-generated code to set per-span properties like allowed unstable features. |
| /// The returned span belongs to the created expansion and has the new properties, |
| /// but its location is inherited from the current span. |
| pub fn fresh_expansion(self, expn_data: ExpnData) -> Span { |
| self.fresh_expansion_with_transparency(expn_data, Transparency::Transparent) |
| } |
| |
| pub fn fresh_expansion_with_transparency( |
| self, expn_data: ExpnData, transparency: Transparency |
| ) -> Span { |
| HygieneData::with(|data| { |
| let expn_id = data.fresh_expn(Some(expn_data)); |
| self.with_ctxt(data.apply_mark(SyntaxContext::root(), expn_id, transparency)) |
| }) |
| } |
| } |
| |
| /// A subset of properties from both macro definition and macro call available through global data. |
| /// Avoid using this if you have access to the original definition or call structures. |
| #[derive(Clone, Debug, RustcEncodable, RustcDecodable)] |
| pub struct ExpnData { |
| // --- The part unique to each expansion. |
| /// The kind of this expansion - macro or compiler desugaring. |
| pub kind: ExpnKind, |
| /// The expansion that produced this expansion. |
| pub parent: ExpnId, |
| /// The location of the actual macro invocation or syntax sugar , e.g. |
| /// `let x = foo!();` or `if let Some(y) = x {}` |
| /// |
| /// This may recursively refer to other macro invocations, e.g., if |
| /// `foo!()` invoked `bar!()` internally, and there was an |
| /// expression inside `bar!`; the call_site of the expression in |
| /// the expansion would point to the `bar!` invocation; that |
| /// call_site span would have its own ExpnData, with the call_site |
| /// pointing to the `foo!` invocation. |
| pub call_site: Span, |
| |
| // --- The part specific to the macro/desugaring definition. |
| // --- It may be reasonable to share this part between expansions with the same definition, |
| // --- but such sharing is known to bring some minor inconveniences without also bringing |
| // --- noticeable perf improvements (PR #62898). |
| /// The span of the macro definition (possibly dummy). |
| /// This span serves only informational purpose and is not used for resolution. |
| pub def_site: Span, |
| /// List of #[unstable]/feature-gated features that the macro is allowed to use |
| /// internally without forcing the whole crate to opt-in |
| /// to them. |
| pub allow_internal_unstable: Option<Lrc<[Symbol]>>, |
| /// Whether the macro is allowed to use `unsafe` internally |
| /// even if the user crate has `#![forbid(unsafe_code)]`. |
| pub allow_internal_unsafe: bool, |
| /// Enables the macro helper hack (`ident!(...)` -> `$crate::ident!(...)`) |
| /// for a given macro. |
| pub local_inner_macros: bool, |
| /// Edition of the crate in which the macro is defined. |
| pub edition: Edition, |
| } |
| |
| impl ExpnData { |
| /// Constructs expansion data with default properties. |
| pub fn default(kind: ExpnKind, call_site: Span, edition: Edition) -> ExpnData { |
| ExpnData { |
| kind, |
| parent: ExpnId::root(), |
| call_site, |
| def_site: DUMMY_SP, |
| allow_internal_unstable: None, |
| allow_internal_unsafe: false, |
| local_inner_macros: false, |
| edition, |
| } |
| } |
| |
| pub fn allow_unstable(kind: ExpnKind, call_site: Span, edition: Edition, |
| allow_internal_unstable: Lrc<[Symbol]>) -> ExpnData { |
| ExpnData { |
| allow_internal_unstable: Some(allow_internal_unstable), |
| ..ExpnData::default(kind, call_site, edition) |
| } |
| } |
| |
| #[inline] |
| pub fn is_root(&self) -> bool { |
| if let ExpnKind::Root = self.kind { true } else { false } |
| } |
| } |
| |
| /// Expansion kind. |
| #[derive(Clone, Debug, RustcEncodable, RustcDecodable)] |
| pub enum ExpnKind { |
| /// No expansion, aka root expansion. Only `ExpnId::root()` has this kind. |
| Root, |
| /// Expansion produced by a macro. |
| Macro(MacroKind, Symbol), |
| /// Transform done by the compiler on the AST. |
| AstPass(AstPass), |
| /// Desugaring done by the compiler during HIR lowering. |
| Desugaring(DesugaringKind) |
| } |
| |
| impl ExpnKind { |
| pub fn descr(&self) -> Symbol { |
| match *self { |
| ExpnKind::Root => kw::PathRoot, |
| ExpnKind::Macro(_, descr) => descr, |
| ExpnKind::AstPass(kind) => Symbol::intern(kind.descr()), |
| ExpnKind::Desugaring(kind) => Symbol::intern(kind.descr()), |
| } |
| } |
| } |
| |
| /// The kind of macro invocation or definition. |
| #[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)] |
| pub enum MacroKind { |
| /// A bang macro `foo!()`. |
| Bang, |
| /// An attribute macro `#[foo]`. |
| Attr, |
| /// A derive macro `#[derive(Foo)]` |
| Derive, |
| } |
| |
| impl MacroKind { |
| pub fn descr(self) -> &'static str { |
| match self { |
| MacroKind::Bang => "macro", |
| MacroKind::Attr => "attribute macro", |
| MacroKind::Derive => "derive macro", |
| } |
| } |
| |
| pub fn article(self) -> &'static str { |
| match self { |
| MacroKind::Attr => "an", |
| _ => "a", |
| } |
| } |
| } |
| |
| /// The kind of AST transform. |
| #[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)] |
| pub enum AstPass { |
| StdImports, |
| TestHarness, |
| ProcMacroHarness, |
| PluginMacroDefs, |
| } |
| |
| impl AstPass { |
| fn descr(self) -> &'static str { |
| match self { |
| AstPass::StdImports => "standard library imports", |
| AstPass::TestHarness => "test harness", |
| AstPass::ProcMacroHarness => "proc macro harness", |
| AstPass::PluginMacroDefs => "plugin macro definitions", |
| } |
| } |
| } |
| |
| /// The kind of compiler desugaring. |
| #[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)] |
| pub enum DesugaringKind { |
| /// We desugar `if c { i } else { e }` to `match $ExprKind::Use(c) { true => i, _ => e }`. |
| /// However, we do not want to blame `c` for unreachability but rather say that `i` |
| /// is unreachable. This desugaring kind allows us to avoid blaming `c`. |
| /// This also applies to `while` loops. |
| CondTemporary, |
| QuestionMark, |
| TryBlock, |
| /// Desugaring of an `impl Trait` in return type position |
| /// to an `type Foo = impl Trait;` and replacing the |
| /// `impl Trait` with `Foo`. |
| OpaqueTy, |
| Async, |
| Await, |
| ForLoop, |
| } |
| |
| impl DesugaringKind { |
| /// The description wording should combine well with "desugaring of {}". |
| fn descr(self) -> &'static str { |
| match self { |
| DesugaringKind::CondTemporary => "`if` or `while` condition", |
| DesugaringKind::Async => "`async` block or function", |
| DesugaringKind::Await => "`await` expression", |
| DesugaringKind::QuestionMark => "operator `?`", |
| DesugaringKind::TryBlock => "`try` block", |
| DesugaringKind::OpaqueTy => "`impl Trait`", |
| DesugaringKind::ForLoop => "`for` loop", |
| } |
| } |
| } |
| |
| impl Encodable for ExpnId { |
| fn encode<E: Encoder>(&self, _: &mut E) -> Result<(), E::Error> { |
| Ok(()) // FIXME(jseyfried) intercrate hygiene |
| } |
| } |
| |
| impl Decodable for ExpnId { |
| fn decode<D: Decoder>(_: &mut D) -> Result<Self, D::Error> { |
| Ok(ExpnId::root()) // FIXME(jseyfried) intercrate hygiene |
| } |
| } |
