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

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

1 files changed, 0 insertions, 30 deletions

diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index ab7ed223bb3..fe9d3ef7c23 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -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)));
-    }
-}