--- /dev/null
+// Copyright 2014 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.
+
+use std::gc::{Gc, GC};
+
+use ast;
+use attr;
+use codemap::Span;
+use ext::base::ExtCtxt;
+use ext::build::AstBuilder;
+
+pub fn expand(cx: &mut ExtCtxt, sp: Span, mi: Gc<ast::MetaItem>, it: Gc<ast::Item>)
+ -> Gc<ast::Item> {
+ let (cfg, attr) = match mi.node {
+ ast::MetaList(_, ref mis) if mis.len() == 2 => (mis[0], mis[1]),
+ _ => {
+ cx.span_err(sp, "expected `#[cfg_attr(<cfg pattern>, <attr>)]`");
+ return it;
+ }
+ };
+
+ let mut out = (*it).clone();
+ if cfg_matches(cx, cfg) {
+ out.attrs.push(cx.attribute(attr.span, attr));
+ }
+
+ box(GC) out
+}
+
+fn cfg_matches(cx: &mut ExtCtxt, cfg: Gc<ast::MetaItem>) -> bool {
+ match cfg.node {
+ ast::MetaList(ref pred, ref mis) if pred.get() == "any" =>
+ mis.iter().any(|mi| cfg_matches(cx, *mi)),
+ ast::MetaList(ref pred, ref mis) if pred.get() == "all" =>
+ mis.iter().all(|mi| cfg_matches(cx, *mi)),
+ ast::MetaList(ref pred, ref mis) if pred.get() == "not" => {
+ if mis.len() != 1 {
+ cx.span_err(cfg.span, format!("expected 1 value, got {}",
+ mis.len()).as_slice());
+ return false;
+ }
+ !cfg_matches(cx, mis[0])
+ }
+ ast::MetaList(ref pred, _) => {
+ cx.span_err(cfg.span,
+ format!("invalid predicate `{}`", pred).as_slice());
+ false
+ },
+ ast::MetaWord(_) | ast::MetaNameValue(..) =>
+ attr::contains(cx.cfg.as_slice(), cfg),
+ }
+}
--- /dev/null
+// Copyright 2014 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.
+
+// compile-flags:--cfg set1 --cfg set2
+#![allow(dead_code)]
+use std::fmt::Show;
+
+struct NotShowable;
+
+#[cfg_attr(set1, deriving(Show))]
+struct Set1;
+
+#[cfg_attr(notset, deriving(Show))]
+struct Notset(NotShowable);
+
+#[cfg_attr(not(notset), deriving(Show))]
+struct NotNotset;
+
+#[cfg_attr(not(set1), deriving(Show))]
+struct NotSet1(NotShowable);
+
+#[cfg_attr(all(set1, set2), deriving(Show))]
+struct AllSet1Set2;
+
+#[cfg_attr(all(set1, notset), deriving(Show))]
+struct AllSet1Notset(NotShowable);
+
+#[cfg_attr(any(set1, notset), deriving(Show))]
+struct AnySet1Notset;
+
+#[cfg_attr(any(notset, notset2), deriving(Show))]
+struct AnyNotsetNotset2(NotShowable);
+
+#[cfg_attr(all(not(notset), any(set1, notset)), deriving(Show))]
+struct Complex;
+
+#[cfg_attr(any(notset, not(any(set1, notset))), deriving(Show))]
+struct ComplexNot(NotShowable);
+
+fn is_show<T: Show>() {}
+
+fn main() {
+ is_show::<Set1>();
+ is_show::<NotNotset>();
+ is_show::<AllSet1Set2>();
+ is_show::<AnySet1Notset>();
+ is_show::<Complex>();
+}