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Auto merge of #34570 - jseyfried:no_rename, r=nrc

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Simplify the macro hygiene algorithm

This PR removes renaming from the hygiene algorithm and treats differently marked identifiers as unequal.

This change makes the scope of identifiers in `macro_rules!` items empty. That is, identifiers in `macro_rules!` definitions do not inherit any semantics from the `macro_rules!`'s scope.

Since `macro_rules!` macros are items, the scope of their identifiers "should" be the same as that of other items; in particular, the scope should contain only items. Since all items are unhygienic today, this would mean the scope should be empty.

However, the scope of an identifier in a `macro_rules!` statement today is the scope that the identifier would have if it replaced the `macro_rules!` (excluding anything unhygienic, i.e. locals only).

To continue to support this, this PR tracks the scope of each `macro_rules!` and uses it in `resolve` to ensure that an identifier expanded from a `macro_rules!` gets a chance to resolve to the locals in the `macro_rules!`'s scope.

This PR is a pure refactoring. After this PR,
 - `syntax::ext::expand` is much simpler.
 - We can expand macros in any order without causing problems for hygiene (needed for macro modularization).
 - We can deprecate or remove today's `macro_rules!` scope easily.
 - Expansion performance improves by 25%, post-expansion memory usage decreases by ~5%.
 - Expanding a block is no longer quadratic in the number of `let` statements (fixes #10607).

r? @nrc
This commit is contained in:
bors 2016-07-15 08:48:41 -07:00 • committed by GitHub
commit 4db1874f4c
10 changed files with 251 additions and 806 deletions
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30
src/libsyntax/parse/token.rs
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@ -15,7 +15,6 @@ pub use self::Lit::*;
pub use self::Token::*;
use ast::{self, BinOpKind};
use ext::mtwt;
use ptr::P;
use util::interner::Interner;
use tokenstream;
@ -313,17 +312,6 @@ impl Token {
_ => false,
}
}
/// Hygienic identifier equality comparison.
///
/// See `styntax::ext::mtwt`.
pub fn mtwt_eq(&self, other : &Token) -> bool {
match (self, other) {
(&Ident(id1), &Ident(id2)) | (&Lifetime(id1), &Lifetime(id2)) =>
mtwt::resolve(id1) == mtwt::resolve(id2),
_ => *self == *other
}
}
}
#[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash)]
@ -650,21 +638,3 @@ pub fn fresh_name(src: ast::Ident) -> ast::Name {
pub fn fresh_mark() -> ast::Mrk {
gensym("mark").0
}
#[cfg(test)]
mod tests {
use super::*;
use ast;
use ext::mtwt;
fn mark_ident(id : ast::Ident, m : ast::Mrk) -> ast::Ident {
ast::Ident::new(id.name, mtwt::apply_mark(m, id.ctxt))
}
#[test] fn mtwt_token_eq_test() {
assert!(Gt.mtwt_eq(&Gt));
let a = str_to_ident("bac");
let a1 = mark_ident(a,92);
assert!(Ident(a).mtwt_eq(&Ident(a1)));
}
}