Implement AtomicRef::map.

MozReview-Commit-ID: 8iOALQylOuK

tests/unit/style/atomic_refcell.rs

@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use style::atomic_refcell::{AtomicRef, AtomicRefCell};
+
+struct Foo {
+    u: u32,
+}
+
+struct Bar {
+    f: Foo,
+}
+
+#[test]
+fn map() {
+    let a = AtomicRefCell::new(Bar { f: Foo { u: 42 } });
+    let b = a.borrow();
+    assert_eq!(b.f.u, 42);
+    let c = AtomicRef::map(b, |x| &x.f);
+    assert_eq!(c.u, 42);
+    let d = AtomicRef::map(c, |x| &x.u);
+    assert_eq!(*d, 42);
+}
+
+/* FIXME(bholley): Enable once we have AtomicRefMut::map(), which is blocked on
+ * https://github.com/Kimundi/owning-ref-rs/pull/16
+#[test]
+fn map_mut() {
+    let a = AtomicRefCell::new(Bar { f: Foo { u: 42 } });
+    let mut b = a.borrow_mut();
+    assert_eq!(b.f.u, 42);
+    b.f.u = 43;
+    let mut c = AtomicRefMut::map(b, |x| &x.f);
+    assert_eq!(c.u, 43);
+    c.u = 44;
+    let mut d = AtomicRefMut::map(c, |x| &x.u);
+    assert_eq!(*d, 44);
+    *d. = 45;
+    assert_eq!(*d, 45);
+}*/

tests/unit/style/lib.rs

@@ -19,6 +19,7 @@ extern crate style_traits;
 extern crate url;
 extern crate util;
 
+mod atomic_refcell;
 mod attr;
 mod cache;
 mod logical_geometry;