src/libsyntax_ext/trace_macros.rs

   1 use syntax::ext::base::ExtCtxt;
   2 use syntax::ext::base;
   3 use syntax::feature_gate;
   4 use syntax::symbol::keywords;
   5 use syntax_pos::Span;
   6 use syntax::tokenstream::TokenTree;
   7
   8 pub fn expand_trace_macros(cx: &mut ExtCtxt,
   9                            sp: Span,
  10                            tt: &[TokenTree])
  11                            -> Box<dyn base::MacResult + 'static> {
  12     if !cx.ecfg.enable_trace_macros() {
  13         feature_gate::emit_feature_err(&cx.parse_sess,
  14                                        "trace_macros",
  15                                        sp,
  16                                        feature_gate::GateIssue::Language,
  17                                        feature_gate::EXPLAIN_TRACE_MACROS);
  18     }
  19
  20     match (tt.len(), tt.first()) {
  21         (1, Some(&TokenTree::Token(_, ref tok))) if tok.is_keyword(keywords::True) => {
  22             cx.set_trace_macros(true);
  23         }
  24         (1, Some(&TokenTree::Token(_, ref tok))) if tok.is_keyword(keywords::False) => {
  25             cx.set_trace_macros(false);
  26         }
  27         _ => cx.span_err(sp, "trace_macros! accepts only `true` or `false`"),
  28     }
  29
  30     base::DummyResult::any_valid(sp)
  31 }