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<istr>) -> @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};
}