Move built-in syntax extensions to a separate crate

src/libsyntax_ext/log_syntax.rs

@@ -0,0 +1,34 @@
+// Copyright 2012 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.
+
+use syntax::ast;
+use syntax::codemap;
+use syntax::ext::base;
+use syntax::feature_gate;
+use syntax::print;
+
+pub fn expand_syntax_ext<'cx>(cx: &'cx mut base::ExtCtxt,
+                              sp: codemap::Span,
+                              tts: &[ast::TokenTree])
+                              -> Box<base::MacResult+'cx> {
+    if !cx.ecfg.enable_log_syntax() {
+        feature_gate::emit_feature_err(&cx.parse_sess.span_diagnostic,
+                                       "log_syntax",
+                                       sp,
+                                       feature_gate::GateIssue::Language,
+                                       feature_gate::EXPLAIN_LOG_SYNTAX);
+        return base::DummyResult::any(sp);
+    }
+
+    println!("{}", print::pprust::tts_to_string(tts));
+
+    // any so that `log_syntax` can be invoked as an expression and item.
+    base::DummyResult::any(sp)
+}