src/libsyntax_ext/trace_macros.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use syntax::ext::base::ExtCtxt;
  12 use syntax::ext::base;
  13 use syntax::feature_gate;
  14 use syntax::symbol::keywords;
  15 use syntax_pos::Span;
  16 use syntax::tokenstream::TokenTree;
  17
  18 pub fn expand_trace_macros(cx: &mut ExtCtxt,
  19                            sp: Span,
  20                            tt: &[TokenTree])
  21                            -> Box<base::MacResult + 'static> {
  22     if !cx.ecfg.enable_trace_macros() {
  23         feature_gate::emit_feature_err(&cx.parse_sess,
  24                                        "trace_macros",
  25                                        sp,
  26                                        feature_gate::GateIssue::Language,
  27                                        feature_gate::EXPLAIN_TRACE_MACROS);
  28         return base::DummyResult::any(sp);
  29     }
  30
  31     match (tt.len(), tt.first()) {
  32         (1, Some(&TokenTree::Token(_, ref tok))) if tok.is_keyword(keywords::True) => {
  33             cx.set_trace_macros(true);
  34         }
  35         (1, Some(&TokenTree::Token(_, ref tok))) if tok.is_keyword(keywords::False) => {
  36             cx.set_trace_macros(false);
  37         }
  38         _ => cx.span_err(sp, "trace_macros! accepts only `true` or `false`"),
  39     }
  40
  41     base::DummyResult::any(sp)
  42 }