rust/src/comp/syntax/ext/concat_idents.rs

import std::option;
import base::*;
import syntax::ast;

fn expand_syntax_ext(cx: &ext_ctxt, sp: codemap::span, arg: @ast::expr,
                     _body: option::t<str>) -> @ast::expr {
    let args: [@ast::expr] = alt arg.node {
      ast::expr_vec(elts, _) { elts }
      _ { cx.span_fatal(sp, "#concat_idents requires a vector argument .") }
    };
    let res: ast::ident = "";
    for e: @ast::expr in args {
        res += expr_to_ident(cx, e, "expected an ident");
    }

    ret @{id: cx.next_id(),
          node: ast::expr_path( {
              node: {global: false, idents: ~[res], types: ~[]},
              span: sp}),
          span: sp};
}