Move built-in syntax extensions to a separate crate

src/libsyntax_ext/trace_macros.rs

@@ -0,0 +1,43 @@
+// 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::TokenTree;
+use syntax::codemap::Span;
+use syntax::ext::base::ExtCtxt;
+use syntax::ext::base;
+use syntax::feature_gate;
+use syntax::parse::token::keywords;
+
+
+pub fn expand_trace_macros(cx: &mut ExtCtxt,
+                           sp: Span,
+                           tt: &[TokenTree])
+                           -> Box<base::MacResult+'static> {
+    if !cx.ecfg.enable_trace_macros() {
+        feature_gate::emit_feature_err(&cx.parse_sess.span_diagnostic,
+                                       "trace_macros",
+                                       sp,
+                                       feature_gate::GateIssue::Language,
+                                       feature_gate::EXPLAIN_TRACE_MACROS);
+        return base::DummyResult::any(sp);
+    }
+
+    match (tt.len(), tt.first()) {
+        (1, Some(&TokenTree::Token(_, ref tok))) if tok.is_keyword(keywords::True) => {
+            cx.set_trace_macros(true);
+        }
+        (1, Some(&TokenTree::Token(_, ref tok))) if tok.is_keyword(keywords::False) => {
+            cx.set_trace_macros(false);
+        }
+        _ => cx.span_err(sp, "trace_macros! accepts only `true` or `false`"),
+    }
+
+    base::DummyResult::any(sp)
+}