rust/src/libsyntax/ext/env.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.


/*
 * The compiler code necessary to support the env! extension.  Eventually this
 * should all get sucked into either the compiler syntax extension plugin
 * interface.
 */
use base::*;
use build::mk_uniq_str;
export expand_syntax_ext;

fn expand_syntax_ext(cx: ext_ctxt, sp: codemap::span, arg: ast::mac_arg,
                     _body: ast::mac_body) -> @ast::expr {
    let args = get_mac_args(cx, sp, arg, 1u, option::Some(1u), ~"env");

    // FIXME (#2248): if this was more thorough it would manufacture an
    // Option<str> rather than just an maybe-empty string.

    let var = expr_to_str(cx, args[0], ~"env! requires a string");
    match os::getenv(var) {
      option::None => return mk_uniq_str(cx, sp, ~""),
      option::Some(ref s) => return mk_uniq_str(cx, sp, (*s))
    }
}

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