auto merge of #6611 : huonw/rust/syntax-ext-no-dup, r=jbclements

Fixes https://github.com/mozilla/rust/issues/6578 by merging the 3 different ways to build an AST into a single `AstBuilder` trait, creating a more uniform and briefer interface.

Also, converts the `ext_ctxt` trait-object to be a plain struct, as well as renaming it to `ExtCtxt`.

Seems to make expansion slightly faster for the normal case (e.g. `libcore` and `libstd`), but slower for `librustc` (slightly) and `libsyntax` (0.3s -> 0.8s! I'm investigating this, but I'd prefer this patch to land relatively quickly.).

`git blame` suggests maybe @graydon or @erickt are familiar with this area of the code. r?

1 files changed, 3 insertions, 3 deletions

diff --git a/src/librustpkg/util.rs b/src/librustpkg/util.rs
index 0ae9539fece..f18396f95be 100644
--- a/src/librustpkg/util.rs
+++ b/src/librustpkg/util.rs
@@ -19,7 +19,7 @@ use std::semver;
 use std::term;
 use syntax::ast_util::*;
 use syntax::codemap::{dummy_sp, spanned, dummy_spanned};
-use syntax::ext::base::{mk_ctxt, ext_ctxt};
+use syntax::ext::base::ExtCtxt;
 use syntax::{ast, attr, codemap, diagnostic, fold};
 use syntax::ast::{meta_name_value, meta_list};
 use syntax::attr::{mk_attr};
@@ -178,7 +178,7 @@ struct ListenerFn {
 struct ReadyCtx {
     sess: session::Session,
     crate: @ast::crate,
-    ext_cx: @ext_ctxt,
+    ext_cx: @ExtCtxt,
     path: ~[ast::ident],
     fns: ~[ListenerFn]
 }
@@ -247,7 +247,7 @@ pub fn ready_crate(sess: session::Session,
     let ctx = @mut ReadyCtx {
         sess: sess,
         crate: crate,
-        ext_cx: mk_ctxt(sess.parse_sess, copy sess.opts.cfg),
+        ext_cx: ExtCtxt::new(sess.parse_sess, copy sess.opts.cfg),
         path: ~[],
         fns: ~[]
     };