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Auto merge of #34860 - jseyfried:encapsulate_hygiene, r=nrc
Clean up and encapsulate `syntax::ext::mtwt`, rename `mtwt` to `hygiene` r? @nrc
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,116 @@ | ||
| // 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 http://dx.doi.org/10.1017/S0956796812000093 | ||
| use std::cell::RefCell; | ||
| use std::collections::HashMap; | ||
| use std::fmt; | ||
|
|
||
| /// A SyntaxContext represents a chain of macro expansions (represented by marks). | ||
| #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Default)] | ||
| pub struct SyntaxContext(u32); | ||
|
|
||
| #[derive(Copy, Clone)] | ||
| pub struct SyntaxContextData { | ||
| pub outer_mark: Mark, | ||
| pub prev_ctxt: SyntaxContext, | ||
| } | ||
|
|
||
| /// A mark represents a unique id associated with a macro expansion. | ||
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Default)] | ||
| pub struct Mark(u32); | ||
|
|
||
| impl Mark { | ||
| pub fn fresh() -> Self { | ||
| HygieneData::with(|data| { | ||
| let next_mark = Mark(data.next_mark.0 + 1); | ||
| ::std::mem::replace(&mut data.next_mark, next_mark) | ||
| }) | ||
| } | ||
| } | ||
|
|
||
| struct HygieneData { | ||
| syntax_contexts: Vec<SyntaxContextData>, | ||
| markings: HashMap<(SyntaxContext, Mark), SyntaxContext>, | ||
| next_mark: Mark, | ||
| } | ||
|
|
||
| impl HygieneData { | ||
| fn new() -> Self { | ||
| HygieneData { | ||
| syntax_contexts: vec![SyntaxContextData { | ||
| outer_mark: Mark(0), // the null mark | ||
| prev_ctxt: SyntaxContext(0), // the empty context | ||
| }], | ||
| markings: HashMap::new(), | ||
| next_mark: Mark(1), | ||
| } | ||
| } | ||
|
|
||
| fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T { | ||
| thread_local! { | ||
| static HYGIENE_DATA: RefCell<HygieneData> = RefCell::new(HygieneData::new()); | ||
| } | ||
| HYGIENE_DATA.with(|data| f(&mut *data.borrow_mut())) | ||
| } | ||
| } | ||
|
|
||
| pub fn reset_hygiene_data() { | ||
| HygieneData::with(|data| *data = HygieneData::new()) | ||
| } | ||
|
|
||
| impl SyntaxContext { | ||
| pub const fn empty() -> Self { | ||
| SyntaxContext(0) | ||
| } | ||
|
|
||
| pub fn data(self) -> SyntaxContextData { | ||
| HygieneData::with(|data| data.syntax_contexts[self.0 as usize]) | ||
| } | ||
|
|
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| /// Extend a syntax context with a given mark | ||
| pub fn apply_mark(self, mark: Mark) -> SyntaxContext { | ||
| // Applying the same mark twice is a no-op | ||
| let ctxt_data = self.data(); | ||
| if mark == ctxt_data.outer_mark { | ||
| return ctxt_data.prev_ctxt; | ||
| } | ||
|
|
||
| HygieneData::with(|data| { | ||
| let syntax_contexts = &mut data.syntax_contexts; | ||
| *data.markings.entry((self, mark)).or_insert_with(|| { | ||
| syntax_contexts.push(SyntaxContextData { | ||
| outer_mark: mark, | ||
| prev_ctxt: self, | ||
| }); | ||
| SyntaxContext(syntax_contexts.len() as u32 - 1) | ||
| }) | ||
| }) | ||
| } | ||
|
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| /// If `ident` is macro expanded, return the source ident from the macro definition | ||
| /// and the mark of the expansion that created the macro definition. | ||
| pub fn source(self) -> (Self /* source context */, Mark /* source macro */) { | ||
| let macro_def_ctxt = self.data().prev_ctxt.data(); | ||
| (macro_def_ctxt.prev_ctxt, macro_def_ctxt.outer_mark) | ||
| } | ||
| } | ||
|
|
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| impl fmt::Debug for SyntaxContext { | ||
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | ||
| write!(f, "#{}", self.0) | ||
| } | ||
| } |
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