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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! 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>
use super::GLOBALS;
use crate::collections::AHashMap;
use serde::{Deserialize, Serialize};
use std::{
collections::{HashMap, HashSet},
fmt,
};
/// A SyntaxContext represents a chain of macro expansions (represented by
/// marks).
#[derive(Clone, Copy, PartialEq, Eq, Default, PartialOrd, Ord, Hash, Serialize, Deserialize)]
#[serde(transparent)]
#[cfg_attr(
feature = "rkyv",
derive(rkyv::Archive, rkyv::Serialize, rkyv::Deserialize)
)]
pub struct SyntaxContext(#[cfg_attr(feature = "rkyv", omit_bounds)] u32);
#[cfg(feature = "arbitrary")]
#[cfg_attr(docsrs, doc(cfg(feature = "arbitrary")))]
impl<'a> arbitrary::Arbitrary<'a> for SyntaxContext {
fn arbitrary(_: &mut arbitrary::Unstructured<'_>) -> arbitrary::Result<Self> {
Ok(SyntaxContext::empty())
}
}
#[derive(Copy, Clone, Debug)]
struct SyntaxContextData {
outer_mark: Mark,
prev_ctxt: SyntaxContext,
// This context, but with all transparent and semi-transparent marks filtered away.
opaque: SyntaxContext,
// This context, but with all transparent marks filtered away.
opaque_and_semitransparent: SyntaxContext,
}
/// A mark is a unique id associated with a macro expansion.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub struct Mark(u32);
#[derive(Clone, Debug)]
struct MarkData {
parent: Mark,
is_builtin: bool,
}
impl Mark {
pub fn fresh(parent: Mark) -> Self {
HygieneData::with(|data| {
data.marks.push(MarkData {
parent,
is_builtin: false,
});
Mark(data.marks.len() as u32 - 1)
})
}
/// The mark of the theoretical expansion that generates freshly parsed,
/// unexpanded AST.
#[inline]
pub fn root() -> Self {
Mark(0)
}
#[inline]
pub fn as_u32(self) -> u32 {
self.0
}
#[inline]
pub fn from_u32(raw: u32) -> Mark {
Mark(raw)
}
#[inline]
pub fn parent(self) -> Mark {
HygieneData::with(|data| data.marks[self.0 as usize].parent)
}
#[inline]
pub fn is_builtin(self) -> bool {
assert_ne!(self, Mark::root());
HygieneData::with(|data| data.marks[self.0 as usize].is_builtin)
}
#[inline]
pub fn set_is_builtin(self, is_builtin: bool) {
assert_ne!(self, Mark::root());
HygieneData::with(|data| data.marks[self.0 as usize].is_builtin = is_builtin)
}
pub fn is_descendant_of(mut self, ancestor: Mark) -> bool {
HygieneData::with(|data| {
while self != ancestor {
if self == Mark::root() {
return false;
}
self = data.marks[self.0 as usize].parent;
}
true
})
}
/// Computes a mark such that both input marks are descendants of (or equal
/// to) the returned mark. That is, the following holds:
///
/// ```rust,ignore
/// let la = least_ancestor(a, b);
/// assert!(a.is_descendant_of(la))
/// assert!(b.is_descendant_of(la))
/// ```
#[allow(unused_mut)]
pub fn least_ancestor(mut a: Mark, mut b: Mark) -> Mark {
HygieneData::with(|data| {
// Compute the path from a to the root
let mut a_path = HashSet::<Mark>::default();
while a != Mark::root() {
a_path.insert(a);
a = data.marks[a.0 as usize].parent;
}
// While the path from b to the root hasn't intersected, move up the tree
while !a_path.contains(&b) {
b = data.marks[b.0 as usize].parent;
}
b
})
}
}
#[derive(Debug)]
pub(crate) struct HygieneData {
marks: Vec<MarkData>,
syntax_contexts: Vec<SyntaxContextData>,
markings: AHashMap<(SyntaxContext, Mark), SyntaxContext>,
}
impl Default for HygieneData {
fn default() -> Self {
Self::new()
}
}
impl HygieneData {
pub(crate) fn new() -> Self {
HygieneData {
marks: vec![MarkData {
parent: Mark::root(),
// If the root is opaque, then loops searching for an opaque mark
// will automatically stop after reaching it.
is_builtin: true,
}],
syntax_contexts: vec![SyntaxContextData {
outer_mark: Mark::root(),
prev_ctxt: SyntaxContext(0),
opaque: SyntaxContext(0),
opaque_and_semitransparent: SyntaxContext(0),
}],
markings: HashMap::default(),
}
}
fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T {
GLOBALS.with(|globals| {
#[cfg(feature = "parking_lot")]
return f(&mut *globals.hygiene_data.lock());
#[cfg(not(feature = "parking_lot"))]
return f(&mut *globals.hygiene_data.lock().unwrap());
})
}
}
// pub fn clear_markings() {
// HygieneData::with(|data| data.markings = HashMap::default());
// }
impl SyntaxContext {
pub const fn empty() -> Self {
SyntaxContext(0)
}
// pub(crate) fn as_u32(self) -> u32 {
// self.0
// }
//
// pub(crate) fn from_u32(raw: u32) -> SyntaxContext {
// SyntaxContext(raw)
// }
/// Extend a syntax context with a given mark and default transparency for
/// that mark.
pub fn apply_mark(self, mark: Mark) -> SyntaxContext {
assert_ne!(mark, Mark::root());
return self.apply_mark_internal(mark);
}
fn apply_mark_internal(self, mark: Mark) -> SyntaxContext {
HygieneData::with(|data| {
let syntax_contexts = &mut data.syntax_contexts;
let mut opaque = syntax_contexts[self.0 as usize].opaque;
let opaque_and_semitransparent =
syntax_contexts[self.0 as usize].opaque_and_semitransparent;
let prev_ctxt = opaque;
opaque = *data.markings.entry((prev_ctxt, mark)).or_insert_with(|| {
let new_opaque = SyntaxContext(syntax_contexts.len() as u32);
syntax_contexts.push(SyntaxContextData {
outer_mark: mark,
prev_ctxt,
opaque: new_opaque,
opaque_and_semitransparent: new_opaque,
});
new_opaque
});
let prev_ctxt = self;
*data.markings.entry((prev_ctxt, mark)).or_insert_with(|| {
let new_opaque_and_semitransparent_and_transparent =
SyntaxContext(syntax_contexts.len() as u32);
syntax_contexts.push(SyntaxContextData {
outer_mark: mark,
prev_ctxt,
opaque,
opaque_and_semitransparent,
});
new_opaque_and_semitransparent_and_transparent
})
})
}
/// 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,ignore
/// 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) -> Mark {
HygieneData::with(|data| {
let outer_mark = data.syntax_contexts[self.0 as usize].outer_mark;
*self = data.syntax_contexts[self.0 as usize].prev_ctxt;
outer_mark
})
}
/// Adjust this context for resolution in a scope created by the given
/// expansion. For example, consider the following three resolutions of
/// `f`:
///
/// ```rust,ignore
/// 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 `Mark` from `m`.
/// pub fn $f() {} // `$f`'s `SyntaxContext` is empty.
/// }
/// foo::f(); // `f`'s `SyntaxContext` has a single `Mark` 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 `Mark` 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::$f`.
/// }
/// ```
/// This returns the expansion whose definition scope we use to privacy
/// check the resolution, or `None` if we privacy check as usual (i.e.
/// not w.r.t. a macro definition scope).
pub fn adjust(&mut self, expansion: Mark) -> Option<Mark> {
let mut scope = None;
while !expansion.is_descendant_of(self.outer()) {
scope = Some(self.remove_mark());
}
scope
}
/// Adjust this context for resolution in a scope created by the given
/// expansion via a glob import with the given `SyntaxContext`.
/// For example:
///
/// ```rust,ignore
/// m!(f);
/// macro m($i:ident) {
/// mod foo {
/// pub fn f() {} // `f`'s `SyntaxContext` has a single `Mark` 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,
expansion: Mark,
mut glob_ctxt: SyntaxContext,
) -> Option<Option<Mark>> {
let mut scope = None;
while !expansion.is_descendant_of(glob_ctxt.outer()) {
scope = Some(glob_ctxt.remove_mark());
if self.remove_mark() != scope.unwrap() {
return None;
}
}
if self.adjust(expansion).is_some() {
return None;
}
Some(scope)
}
/// Undo `glob_adjust` if possible:
///
/// ```rust,ignore
/// 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,
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 outer(self) -> Mark {
HygieneData::with(|data| data.syntax_contexts[self.0 as usize].outer_mark)
}
}
impl fmt::Debug for SyntaxContext {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "#{}", self.0)
}
}
impl Default for Mark {
fn default() -> Self {
Mark::root()
}
}