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 syntax::ast::{self, TokenTree};
  12 use syntax::codemap::Span;
  13 use syntax::ext::base::*;
  14 use syntax::ext::base;
  15 use syntax::feature_gate;
  16 use syntax::parse::token;
  17 use syntax::parse::token::str_to_ident;
  18 use syntax::ptr::P;
  19
  20 pub fn expand_syntax_ext<'cx>(cx: &mut ExtCtxt, sp: Span, tts: &[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::GateIssue::Language,
  27                                        feature_gate::EXPLAIN_CONCAT_IDENTS);
  28         return base::DummyResult::expr(sp);
  29     }
  30
  31     let mut res_str = String::new();
  32     for (i, e) in tts.iter().enumerate() {
  33         if i & 1 == 1 {
  34             match *e {
  35                 TokenTree::Token(_, token::Comma) => {},
  36                 _ => {
  37                     cx.span_err(sp, "concat_idents! expecting comma.");
  38                     return DummyResult::expr(sp);
  39                 },
  40             }
  41         } else {
  42             match *e {
  43                 TokenTree::Token(_, token::Ident(ident, _)) => {
  44                     res_str.push_str(&ident.name.as_str())
  45                 },
  46                 _ => {
  47                     cx.span_err(sp, "concat_idents! requires ident args.");
  48                     return DummyResult::expr(sp);
  49                 },
  50             }
  51         }
  52     }
  53     let res = str_to_ident(&res_str);
  54
  55     let e = P(ast::Expr {
  56         id: ast::DUMMY_NODE_ID,
  57         node: ast::ExprPath(None,
  58             ast::Path {
  59                  span: sp,
  60                  global: false,
  61                  segments: vec!(
  62                     ast::PathSegment {
  63                         identifier: res,
  64                         parameters: ast::PathParameters::none(),
  65                     }
  66                 )
  67             }
  68         ),
  69         span: sp,
  70         attrs: None,
  71     });
  72     MacEager::expr(e)
  73 }