Refactor and fix FIXME's in mtwt hygiene code

- Moves mtwt hygiene code into its own file
- Fixes FIXME's which leads to ~2x speed gain in expansion pass
- It is now @-free

Author: edwardw

src/librustc/middle/resolve.rs

@@ -19,8 +19,9 @@ use middle::pat_util::pat_bindings;
 
 use syntax::ast::*;
 use syntax::ast;
-use syntax::ast_util::{def_id_of_def, local_def, mtwt_resolve};
+use syntax::ast_util::{def_id_of_def, local_def};
 use syntax::ast_util::{path_to_ident, walk_pat, trait_method_to_ty_method};
+use syntax::ext::mtwt;
 use syntax::parse::token::special_idents;
 use syntax::parse::token;
 use syntax::print::pprust::path_to_str;
@@ -4176,7 +4177,7 @@ impl Resolver {
     fn binding_mode_map(&mut self, pat: @Pat) -> BindingMap {
         let mut result = HashMap::new();
         pat_bindings(self.def_map, pat, |binding_mode, _id, sp, path| {
-            let name = mtwt_resolve(path_to_ident(path));
+            let name = mtwt::resolve(path_to_ident(path));
             result.insert(name,
                           binding_info {span: sp,
                                         binding_mode: binding_mode});
@@ -4411,7 +4412,7 @@ impl Resolver {
                     // what you want).
 
                     let ident = path.segments.get(0).identifier;
-                    let renamed = mtwt_resolve(ident);
+                    let renamed = mtwt::resolve(ident);
 
                     match self.resolve_bare_identifier_pattern(ident) {
                         FoundStructOrEnumVariant(def, lp)
@@ -4965,7 +4966,7 @@ impl Resolver {
         let search_result;
         match namespace {
             ValueNS => {
-                let renamed = mtwt_resolve(ident);
+                let renamed = mtwt::resolve(ident);
                 let mut value_ribs = self.value_ribs.borrow_mut();
                 search_result = self.search_ribs(value_ribs.get(),
                                                  renamed,
@@ -5213,7 +5214,7 @@ impl Resolver {
                         let rib = label_ribs.get()[label_ribs.get().len() -
                                                    1];
                         let mut bindings = rib.bindings.borrow_mut();
-                        let renamed = mtwt_resolve(label);
+                        let renamed = mtwt::resolve(label);
                         bindings.get().insert(renamed, def_like);
                     }
 
@@ -5225,7 +5226,7 @@ impl Resolver {
 
             ExprBreak(Some(label)) | ExprAgain(Some(label)) => {
                 let mut label_ribs = self.label_ribs.borrow_mut();
-                let renamed = mtwt_resolve(label);
+                let renamed = mtwt::resolve(label);
                 match self.search_ribs(label_ribs.get(), renamed, expr.span) {
                     None =>
                         self.resolve_error(expr.span,

src/libsyntax/ast.rs

@@ -19,8 +19,6 @@ use parse::token;
 
 use std::fmt;
 use std::fmt::Show;
-use std::cell::RefCell;
-use collections::HashMap;
 use std::option::Option;
 use std::rc::Rc;
 use std::vec_ng::Vec;
@@ -42,7 +40,10 @@ pub fn P<T: 'static>(value: T) -> P<T> {
 // macro expansion per Flatt et al., "Macros
 // That Work Together"
 #[deriving(Clone, Hash, TotalEq, TotalOrd, Show)]
-pub struct Ident { name: Name, ctxt: SyntaxContext }
+pub struct Ident {
+    name: Name,
+    ctxt: SyntaxContext
+}
 
 impl Ident {
     /// Construct an identifier with the given name and an empty context:
@@ -88,43 +89,9 @@ impl Eq for Ident {
 // this uint is a reference to a table stored in thread-local
 // storage.
 pub type SyntaxContext = u32;
-
-// the SCTable contains a table of SyntaxContext_'s. It
-// represents a flattened tree structure, to avoid having
-// managed pointers everywhere (that caused an ICE).
-// the mark_memo and rename_memo fields are side-tables
-// that ensure that adding the same mark to the same context
-// gives you back the same context as before. This shouldn't
-// change the semantics--everything here is immutable--but
-// it should cut down on memory use *a lot*; applying a mark
-// to a tree containing 50 identifiers would otherwise generate
-pub struct SCTable {
-    table: RefCell<Vec<SyntaxContext_> >,
-    mark_memo: RefCell<HashMap<(SyntaxContext,Mrk),SyntaxContext>>,
-    rename_memo: RefCell<HashMap<(SyntaxContext,Ident,Name),SyntaxContext>>,
-}
-
-// NB: these must be placed in any SCTable...
 pub static EMPTY_CTXT : SyntaxContext = 0;
 pub static ILLEGAL_CTXT : SyntaxContext = 1;
 
-#[deriving(Eq, Encodable, Decodable, Hash)]
-pub enum SyntaxContext_ {
-    EmptyCtxt,
-    Mark (Mrk,SyntaxContext),
-    // flattening the name and syntaxcontext into the rename...
-    // HIDDEN INVARIANTS:
-    // 1) the first name in a Rename node
-    // can only be a programmer-supplied name.
-    // 2) Every Rename node with a given Name in the
-    // "to" slot must have the same name and context
-    // in the "from" slot. In essence, they're all
-    // pointers to a single "rename" event node.
-    Rename (Ident,Name,SyntaxContext),
-    // actually, IllegalCtxt may not be necessary.
-    IllegalCtxt
-}
-
 /// A name is a part of an identifier, representing a string or gensym. It's
 /// the result of interning.
 pub type Name = u32;