src/libsyntax/ext/concat_idents.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 ast;
  12 use codemap::Span;
  13 use ext::base::*;
  14 use ext::base;
  15 use feature_gate;
  16 use parse::token;
  17 use parse::token::{str_to_ident};
  18 use ptr::P;
  19
  20 pub fn expand_syntax_ext<'cx>(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
  21                               -> Box<base::MacResult+'cx> {
  22     if !cx.ecfg.enable_concat_idents() {
  23         feature_gate::emit_feature_err(&cx.parse_sess.span_diagnostic,
  24                                        "concat_idents",
  25                                        sp,
  26                                        feature_gate::EXPLAIN_CONCAT_IDENTS);
  27         return base::DummyResult::expr(sp);
  28     }
  29
  30     let mut res_str = String::new();
  31     for (i, e) in tts.iter().enumerate() {
  32         if i & 1 == 1 {
  33             match *e {
  34                 ast::TtToken(_, token::Comma) => {},
  35                 _ => {
  36                     cx.span_err(sp, "concat_idents! expecting comma.");
  37                     return DummyResult::expr(sp);
  38                 },
  39             }
  40         } else {
  41             match *e {
  42                 ast::TtToken(_, token::Ident(ident, _)) => {
  43                     res_str.push_str(&token::get_ident(ident))
  44                 },
  45                 _ => {
  46                     cx.span_err(sp, "concat_idents! requires ident args.");
  47                     return DummyResult::expr(sp);
  48                 },
  49             }
  50         }
  51     }
  52     let res = str_to_ident(&res_str[..]);
  53
  54     let e = P(ast::Expr {
  55         id: ast::DUMMY_NODE_ID,
  56         node: ast::ExprPath(
  57             ast::Path {
  58                  span: sp,
  59                  global: false,
  60                  segments: vec!(
  61                     ast::PathSegment {
  62                         identifier: res,
  63                         parameters: ast::PathParameters::none(),
  64                     }
  65                 )
  66             }
  67         ),
  68         span: sp,
  69     });
  70     MacExpr::new(e)
  71 }