627 lines
23 KiB
Rust
627 lines
23 KiB
Rust
//! Machinery for hygienic macros, inspired by the `MTWT[1]` paper.
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//!
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//! `[1]` Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler. 2012.
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//! *Macros that work together: Compile-time bindings, partial expansion,
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//! and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216.
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//! DOI=10.1017/S0956796812000093 <https://doi.org/10.1017/S0956796812000093>
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use crate::GLOBALS;
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use crate::Span;
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use crate::edition::{Edition, DEFAULT_EDITION};
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use crate::symbol::{keywords, Symbol};
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use serialize::{Encodable, Decodable, Encoder, Decoder};
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use rustc_data_structures::fx::{FxHashMap, FxHashSet};
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use rustc_data_structures::sync::Lrc;
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use std::{fmt, mem};
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/// A SyntaxContext represents a chain of macro expansions (represented by marks).
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#[derive(Clone, Copy, PartialEq, Eq, Default, PartialOrd, Ord, Hash)]
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pub struct SyntaxContext(u32);
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#[derive(Copy, Clone, Debug)]
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struct SyntaxContextData {
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outer_mark: Mark,
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transparency: Transparency,
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prev_ctxt: SyntaxContext,
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/// This context, but with all transparent and semi-transparent marks filtered away.
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opaque: SyntaxContext,
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/// This context, but with all transparent marks filtered away.
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opaque_and_semitransparent: SyntaxContext,
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/// Name of the crate to which `$crate` with this context would resolve.
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dollar_crate_name: Symbol,
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}
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/// A mark is a unique ID associated with a macro expansion.
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#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
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pub struct Mark(u32);
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#[derive(Clone, Debug)]
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struct MarkData {
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parent: Mark,
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default_transparency: Transparency,
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expn_info: Option<ExpnInfo>,
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}
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/// A property of a macro expansion that determines how identifiers
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/// produced by that expansion are resolved.
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#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
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pub enum Transparency {
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/// Identifier produced by a transparent expansion is always resolved at call-site.
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/// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this.
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Transparent,
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/// Identifier produced by a semi-transparent expansion may be resolved
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/// either at call-site or at definition-site.
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/// If it's a local variable, label or `$crate` then it's resolved at def-site.
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/// Otherwise it's resolved at call-site.
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/// `macro_rules` macros behave like this, built-in macros currently behave like this too,
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/// but that's an implementation detail.
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SemiTransparent,
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/// Identifier produced by an opaque expansion is always resolved at definition-site.
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/// Def-site spans in procedural macros, identifiers from `macro` by default use this.
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Opaque,
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}
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impl Mark {
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pub fn fresh(parent: Mark) -> Self {
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HygieneData::with(|data| {
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data.marks.push(MarkData {
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parent,
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// By default expansions behave like `macro_rules`.
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default_transparency: Transparency::SemiTransparent,
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expn_info: None,
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});
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Mark(data.marks.len() as u32 - 1)
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})
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}
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/// The mark of the theoretical expansion that generates freshly parsed, unexpanded AST.
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#[inline]
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pub fn root() -> Self {
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Mark(0)
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}
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#[inline]
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pub fn as_u32(self) -> u32 {
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self.0
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}
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#[inline]
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pub fn from_u32(raw: u32) -> Mark {
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Mark(raw)
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}
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#[inline]
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pub fn parent(self) -> Mark {
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HygieneData::with(|data| data.marks[self.0 as usize].parent)
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}
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#[inline]
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pub fn expn_info(self) -> Option<ExpnInfo> {
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HygieneData::with(|data| data.marks[self.0 as usize].expn_info.clone())
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}
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#[inline]
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pub fn set_expn_info(self, info: ExpnInfo) {
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HygieneData::with(|data| data.marks[self.0 as usize].expn_info = Some(info))
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}
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#[inline]
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pub fn set_default_transparency(self, transparency: Transparency) {
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assert_ne!(self, Mark::root());
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HygieneData::with(|data| data.marks[self.0 as usize].default_transparency = transparency)
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}
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pub fn is_descendant_of(mut self, ancestor: Mark) -> bool {
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HygieneData::with(|data| {
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while self != ancestor {
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if self == Mark::root() {
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return false;
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}
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self = data.marks[self.0 as usize].parent;
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}
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true
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})
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}
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/// Computes a mark such that both input marks are descendants of (or equal to) the returned
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/// mark. That is, the following holds:
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///
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/// ```rust
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/// let la = least_ancestor(a, b);
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/// assert!(a.is_descendant_of(la))
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/// assert!(b.is_descendant_of(la))
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/// ```
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pub fn least_ancestor(mut a: Mark, mut b: Mark) -> Mark {
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HygieneData::with(|data| {
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// Compute the path from a to the root
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let mut a_path = FxHashSet::<Mark>::default();
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while a != Mark::root() {
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a_path.insert(a);
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a = data.marks[a.0 as usize].parent;
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}
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// While the path from b to the root hasn't intersected, move up the tree
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while !a_path.contains(&b) {
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b = data.marks[b.0 as usize].parent;
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}
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b
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})
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}
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// Used for enabling some compatibility fallback in resolve.
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#[inline]
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pub fn looks_like_proc_macro_derive(self) -> bool {
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HygieneData::with(|data| {
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let mark_data = &data.marks[self.0 as usize];
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if mark_data.default_transparency == Transparency::Opaque {
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if let Some(expn_info) = &mark_data.expn_info {
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if let ExpnFormat::MacroAttribute(name) = expn_info.format {
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if name.as_str().starts_with("derive(") {
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return true;
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}
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}
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}
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}
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false
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})
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}
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}
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#[derive(Debug)]
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crate struct HygieneData {
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marks: Vec<MarkData>,
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syntax_contexts: Vec<SyntaxContextData>,
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markings: FxHashMap<(SyntaxContext, Mark, Transparency), SyntaxContext>,
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default_edition: Edition,
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}
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impl HygieneData {
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crate fn new() -> Self {
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HygieneData {
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marks: vec![MarkData {
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parent: Mark::root(),
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// If the root is opaque, then loops searching for an opaque mark
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// will automatically stop after reaching it.
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default_transparency: Transparency::Opaque,
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expn_info: None,
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}],
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syntax_contexts: vec![SyntaxContextData {
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outer_mark: Mark::root(),
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transparency: Transparency::Opaque,
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prev_ctxt: SyntaxContext(0),
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opaque: SyntaxContext(0),
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opaque_and_semitransparent: SyntaxContext(0),
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dollar_crate_name: keywords::DollarCrate.name(),
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}],
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markings: FxHashMap::default(),
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default_edition: DEFAULT_EDITION,
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}
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}
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fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T {
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GLOBALS.with(|globals| f(&mut *globals.hygiene_data.borrow_mut()))
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}
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}
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pub fn default_edition() -> Edition {
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HygieneData::with(|data| data.default_edition)
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}
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pub fn set_default_edition(edition: Edition) {
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HygieneData::with(|data| data.default_edition = edition);
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}
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pub fn clear_markings() {
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HygieneData::with(|data| data.markings = FxHashMap::default());
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}
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impl SyntaxContext {
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#[inline]
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pub const fn empty() -> Self {
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SyntaxContext(0)
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}
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#[inline]
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crate fn as_u32(self) -> u32 {
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self.0
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}
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#[inline]
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crate fn from_u32(raw: u32) -> SyntaxContext {
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SyntaxContext(raw)
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}
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// Allocate a new SyntaxContext with the given ExpnInfo. This is used when
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// deserializing Spans from the incr. comp. cache.
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// FIXME(mw): This method does not restore MarkData::parent or
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// SyntaxContextData::prev_ctxt or SyntaxContextData::opaque. These things
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// don't seem to be used after HIR lowering, so everything should be fine
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// as long as incremental compilation does not kick in before that.
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pub fn allocate_directly(expansion_info: ExpnInfo) -> Self {
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HygieneData::with(|data| {
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data.marks.push(MarkData {
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parent: Mark::root(),
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default_transparency: Transparency::SemiTransparent,
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expn_info: Some(expansion_info),
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});
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let mark = Mark(data.marks.len() as u32 - 1);
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data.syntax_contexts.push(SyntaxContextData {
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outer_mark: mark,
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transparency: Transparency::SemiTransparent,
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prev_ctxt: SyntaxContext::empty(),
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opaque: SyntaxContext::empty(),
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opaque_and_semitransparent: SyntaxContext::empty(),
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dollar_crate_name: keywords::DollarCrate.name(),
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});
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SyntaxContext(data.syntax_contexts.len() as u32 - 1)
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})
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}
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/// Extend a syntax context with a given mark and default transparency for that mark.
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pub fn apply_mark(self, mark: Mark) -> SyntaxContext {
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assert_ne!(mark, Mark::root());
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self.apply_mark_with_transparency(
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mark, HygieneData::with(|data| data.marks[mark.0 as usize].default_transparency)
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)
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}
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/// Extend a syntax context with a given mark and transparency
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pub fn apply_mark_with_transparency(self, mark: Mark, transparency: Transparency)
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-> SyntaxContext {
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assert_ne!(mark, Mark::root());
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if transparency == Transparency::Opaque {
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return self.apply_mark_internal(mark, transparency);
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}
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let call_site_ctxt =
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mark.expn_info().map_or(SyntaxContext::empty(), |info| info.call_site.ctxt());
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let call_site_ctxt = if transparency == Transparency::SemiTransparent {
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call_site_ctxt.modern()
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} else {
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call_site_ctxt.modern_and_legacy()
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};
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if call_site_ctxt == SyntaxContext::empty() {
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return self.apply_mark_internal(mark, transparency);
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}
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// Otherwise, `mark` is a macros 1.0 definition and the call site is in a
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// macros 2.0 expansion, i.e., a macros 1.0 invocation is in a macros 2.0 definition.
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//
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// In this case, the tokens from the macros 1.0 definition inherit the hygiene
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// at their invocation. That is, we pretend that the macros 1.0 definition
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// was defined at its invocation (i.e., inside the macros 2.0 definition)
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// so that the macros 2.0 definition remains hygienic.
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//
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// See the example at `test/run-pass/hygiene/legacy_interaction.rs`.
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let mut ctxt = call_site_ctxt;
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for (mark, transparency) in self.marks() {
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ctxt = ctxt.apply_mark_internal(mark, transparency);
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}
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ctxt.apply_mark_internal(mark, transparency)
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}
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fn apply_mark_internal(self, mark: Mark, transparency: Transparency) -> SyntaxContext {
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HygieneData::with(|data| {
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let syntax_contexts = &mut data.syntax_contexts;
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let mut opaque = syntax_contexts[self.0 as usize].opaque;
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let mut opaque_and_semitransparent =
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syntax_contexts[self.0 as usize].opaque_and_semitransparent;
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if transparency >= Transparency::Opaque {
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let prev_ctxt = opaque;
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opaque = *data.markings.entry((prev_ctxt, mark, transparency)).or_insert_with(|| {
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let new_opaque = SyntaxContext(syntax_contexts.len() as u32);
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syntax_contexts.push(SyntaxContextData {
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outer_mark: mark,
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transparency,
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prev_ctxt,
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opaque: new_opaque,
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opaque_and_semitransparent: new_opaque,
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dollar_crate_name: keywords::DollarCrate.name(),
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});
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new_opaque
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});
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}
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if transparency >= Transparency::SemiTransparent {
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let prev_ctxt = opaque_and_semitransparent;
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opaque_and_semitransparent =
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*data.markings.entry((prev_ctxt, mark, transparency)).or_insert_with(|| {
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let new_opaque_and_semitransparent =
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SyntaxContext(syntax_contexts.len() as u32);
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syntax_contexts.push(SyntaxContextData {
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outer_mark: mark,
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transparency,
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prev_ctxt,
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opaque,
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opaque_and_semitransparent: new_opaque_and_semitransparent,
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dollar_crate_name: keywords::DollarCrate.name(),
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});
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new_opaque_and_semitransparent
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});
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}
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let prev_ctxt = self;
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*data.markings.entry((prev_ctxt, mark, transparency)).or_insert_with(|| {
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let new_opaque_and_semitransparent_and_transparent =
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SyntaxContext(syntax_contexts.len() as u32);
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syntax_contexts.push(SyntaxContextData {
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outer_mark: mark,
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transparency,
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prev_ctxt,
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opaque,
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opaque_and_semitransparent,
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dollar_crate_name: keywords::DollarCrate.name(),
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});
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new_opaque_and_semitransparent_and_transparent
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})
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})
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}
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/// Pulls a single mark off of the syntax context. This effectively moves the
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/// context up one macro definition level. That is, if we have a nested macro
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/// definition as follows:
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///
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/// ```rust
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/// macro_rules! f {
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/// macro_rules! g {
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/// ...
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/// }
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/// }
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/// ```
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///
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/// and we have a SyntaxContext that is referring to something declared by an invocation
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/// of g (call it g1), calling remove_mark will result in the SyntaxContext for the
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/// invocation of f that created g1.
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/// Returns the mark that was removed.
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pub fn remove_mark(&mut self) -> Mark {
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HygieneData::with(|data| {
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let outer_mark = data.syntax_contexts[self.0 as usize].outer_mark;
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*self = data.syntax_contexts[self.0 as usize].prev_ctxt;
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outer_mark
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})
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}
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pub fn marks(mut self) -> Vec<(Mark, Transparency)> {
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HygieneData::with(|data| {
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let mut marks = Vec::new();
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while self != SyntaxContext::empty() {
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let ctxt_data = &data.syntax_contexts[self.0 as usize];
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marks.push((ctxt_data.outer_mark, ctxt_data.transparency));
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self = ctxt_data.prev_ctxt;
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}
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marks.reverse();
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marks
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})
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}
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/// Adjust this context for resolution in a scope created by the given expansion.
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/// For example, consider the following three resolutions of `f`:
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///
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/// ```rust
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/// mod foo { pub fn f() {} } // `f`'s `SyntaxContext` is empty.
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/// m!(f);
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/// macro m($f:ident) {
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/// mod bar {
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/// pub fn f() {} // `f`'s `SyntaxContext` has a single `Mark` from `m`.
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/// pub fn $f() {} // `$f`'s `SyntaxContext` is empty.
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/// }
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/// foo::f(); // `f`'s `SyntaxContext` has a single `Mark` from `m`
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/// //^ Since `mod foo` is outside this expansion, `adjust` removes the mark from `f`,
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/// //| and it resolves to `::foo::f`.
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/// bar::f(); // `f`'s `SyntaxContext` has a single `Mark` from `m`
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/// //^ Since `mod bar` not outside this expansion, `adjust` does not change `f`,
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/// //| and it resolves to `::bar::f`.
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/// bar::$f(); // `f`'s `SyntaxContext` is empty.
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/// //^ Since `mod bar` is not outside this expansion, `adjust` does not change `$f`,
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/// //| and it resolves to `::bar::$f`.
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/// }
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/// ```
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/// This returns the expansion whose definition scope we use to privacy check the resolution,
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/// or `None` if we privacy check as usual (i.e., not w.r.t. a macro definition scope).
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pub fn adjust(&mut self, expansion: Mark) -> Option<Mark> {
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let mut scope = None;
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while !expansion.is_descendant_of(self.outer()) {
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scope = Some(self.remove_mark());
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}
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scope
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}
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/// Adjust this context for resolution in a scope created by the given expansion
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/// via a glob import with the given `SyntaxContext`.
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/// For example:
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///
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/// ```rust
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/// m!(f);
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/// macro m($i:ident) {
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/// mod foo {
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/// pub fn f() {} // `f`'s `SyntaxContext` has a single `Mark` from `m`.
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/// pub fn $i() {} // `$i`'s `SyntaxContext` is empty.
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/// }
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/// n(f);
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/// macro n($j:ident) {
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/// use foo::*;
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/// f(); // `f`'s `SyntaxContext` has a mark from `m` and a mark from `n`
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/// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::f`.
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/// $i(); // `$i`'s `SyntaxContext` has a mark from `n`
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/// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::$i`.
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/// $j(); // `$j`'s `SyntaxContext` has a mark from `m`
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/// //^ This cannot be glob-adjusted, so this is a resolution error.
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/// }
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/// }
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/// ```
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/// This returns `None` if the context cannot be glob-adjusted.
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/// Otherwise, it returns the scope to use when privacy checking (see `adjust` for details).
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pub fn glob_adjust(&mut self, expansion: Mark, mut glob_ctxt: SyntaxContext)
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-> Option<Option<Mark>> {
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let mut scope = None;
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while !expansion.is_descendant_of(glob_ctxt.outer()) {
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scope = Some(glob_ctxt.remove_mark());
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if self.remove_mark() != scope.unwrap() {
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return None;
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}
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}
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if self.adjust(expansion).is_some() {
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return None;
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}
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Some(scope)
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}
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/// Undo `glob_adjust` if possible:
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///
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/// ```rust
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/// if let Some(privacy_checking_scope) = self.reverse_glob_adjust(expansion, glob_ctxt) {
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/// assert!(self.glob_adjust(expansion, glob_ctxt) == Some(privacy_checking_scope));
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/// }
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/// ```
|
|
pub fn reverse_glob_adjust(&mut self, expansion: Mark, mut glob_ctxt: SyntaxContext)
|
|
-> Option<Option<Mark>> {
|
|
if self.adjust(expansion).is_some() {
|
|
return None;
|
|
}
|
|
|
|
let mut marks = Vec::new();
|
|
while !expansion.is_descendant_of(glob_ctxt.outer()) {
|
|
marks.push(glob_ctxt.remove_mark());
|
|
}
|
|
|
|
let scope = marks.last().cloned();
|
|
while let Some(mark) = marks.pop() {
|
|
*self = self.apply_mark(mark);
|
|
}
|
|
Some(scope)
|
|
}
|
|
|
|
#[inline]
|
|
pub fn modern(self) -> SyntaxContext {
|
|
HygieneData::with(|data| data.syntax_contexts[self.0 as usize].opaque)
|
|
}
|
|
|
|
#[inline]
|
|
pub fn modern_and_legacy(self) -> SyntaxContext {
|
|
HygieneData::with(|data| data.syntax_contexts[self.0 as usize].opaque_and_semitransparent)
|
|
}
|
|
|
|
#[inline]
|
|
pub fn outer(self) -> Mark {
|
|
HygieneData::with(|data| data.syntax_contexts[self.0 as usize].outer_mark)
|
|
}
|
|
|
|
pub fn dollar_crate_name(self) -> Symbol {
|
|
HygieneData::with(|data| data.syntax_contexts[self.0 as usize].dollar_crate_name)
|
|
}
|
|
|
|
pub fn set_dollar_crate_name(self, dollar_crate_name: Symbol) {
|
|
HygieneData::with(|data| {
|
|
let prev_dollar_crate_name = mem::replace(
|
|
&mut data.syntax_contexts[self.0 as usize].dollar_crate_name, dollar_crate_name
|
|
);
|
|
assert!(dollar_crate_name == prev_dollar_crate_name ||
|
|
prev_dollar_crate_name == keywords::DollarCrate.name(),
|
|
"$crate name is reset for a syntax context");
|
|
})
|
|
}
|
|
}
|
|
|
|
impl fmt::Debug for SyntaxContext {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
write!(f, "#{}", self.0)
|
|
}
|
|
}
|
|
|
|
/// Extra information for tracking spans of macro and syntax sugar expansion
|
|
#[derive(Clone, Hash, Debug, RustcEncodable, RustcDecodable)]
|
|
pub struct ExpnInfo {
|
|
/// The location of the actual macro invocation or syntax sugar , e.g.
|
|
/// `let x = foo!();` or `if let Some(y) = x {}`
|
|
///
|
|
/// This may recursively refer to other macro invocations, e.g., if
|
|
/// `foo!()` invoked `bar!()` internally, and there was an
|
|
/// expression inside `bar!`; the call_site of the expression in
|
|
/// the expansion would point to the `bar!` invocation; that
|
|
/// call_site span would have its own ExpnInfo, with the call_site
|
|
/// pointing to the `foo!` invocation.
|
|
pub call_site: Span,
|
|
/// The span of the macro definition itself. The macro may not
|
|
/// have a sensible definition span (e.g., something defined
|
|
/// completely inside libsyntax) in which case this is None.
|
|
/// This span serves only informational purpose and is not used for resolution.
|
|
pub def_site: Option<Span>,
|
|
/// The format with which the macro was invoked.
|
|
pub format: ExpnFormat,
|
|
/// List of #[unstable]/feature-gated features that the macro is allowed to use
|
|
/// internally without forcing the whole crate to opt-in
|
|
/// to them.
|
|
pub allow_internal_unstable: Option<Lrc<[Symbol]>>,
|
|
/// Whether the macro is allowed to use `unsafe` internally
|
|
/// even if the user crate has `#![forbid(unsafe_code)]`.
|
|
pub allow_internal_unsafe: bool,
|
|
/// Enables the macro helper hack (`ident!(...)` -> `$crate::ident!(...)`)
|
|
/// for a given macro.
|
|
pub local_inner_macros: bool,
|
|
/// Edition of the crate in which the macro is defined.
|
|
pub edition: Edition,
|
|
}
|
|
|
|
/// The source of expansion.
|
|
#[derive(Clone, Hash, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
|
|
pub enum ExpnFormat {
|
|
/// e.g., #[derive(...)] <item>
|
|
MacroAttribute(Symbol),
|
|
/// e.g., `format!()`
|
|
MacroBang(Symbol),
|
|
/// Desugaring done by the compiler during HIR lowering.
|
|
CompilerDesugaring(CompilerDesugaringKind)
|
|
}
|
|
|
|
impl ExpnFormat {
|
|
pub fn name(&self) -> Symbol {
|
|
match *self {
|
|
ExpnFormat::MacroBang(name) | ExpnFormat::MacroAttribute(name) => name,
|
|
ExpnFormat::CompilerDesugaring(kind) => kind.name(),
|
|
}
|
|
}
|
|
}
|
|
|
|
/// The kind of compiler desugaring.
|
|
#[derive(Clone, Copy, Hash, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
|
|
pub enum CompilerDesugaringKind {
|
|
QuestionMark,
|
|
TryBlock,
|
|
/// Desugaring of an `impl Trait` in return type position
|
|
/// to an `existential type Foo: Trait;` and replacing the
|
|
/// `impl Trait` with `Foo`.
|
|
ExistentialReturnType,
|
|
Async,
|
|
ForLoop,
|
|
}
|
|
|
|
impl CompilerDesugaringKind {
|
|
pub fn name(self) -> Symbol {
|
|
Symbol::intern(match self {
|
|
CompilerDesugaringKind::Async => "async",
|
|
CompilerDesugaringKind::QuestionMark => "?",
|
|
CompilerDesugaringKind::TryBlock => "try block",
|
|
CompilerDesugaringKind::ExistentialReturnType => "existential type",
|
|
CompilerDesugaringKind::ForLoop => "for loop",
|
|
})
|
|
}
|
|
}
|
|
|
|
impl Encodable for SyntaxContext {
|
|
fn encode<E: Encoder>(&self, _: &mut E) -> Result<(), E::Error> {
|
|
Ok(()) // FIXME(jseyfried) intercrate hygiene
|
|
}
|
|
}
|
|
|
|
impl Decodable for SyntaxContext {
|
|
fn decode<D: Decoder>(_: &mut D) -> Result<SyntaxContext, D::Error> {
|
|
Ok(SyntaxContext::empty()) // FIXME(jseyfried) intercrate hygiene
|
|
}
|
|
}
|