Auto merge of #165 - servo:default--partialeq-string, r=nox

Implement Default and PartialEq<String>.

This is part of the changes proposed at servo/servo#12391 (comment)

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Author: bors-servo

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "string_cache"
-version = "0.2.21"
+version = "0.2.22"
 authors = [ "The Servo Project Developers" ]
 description = "A string interning library for Rust, developed as part of the Servo project."
 license = "MIT / Apache-2.0"

src/atom/mod.rs

@@ -203,6 +203,12 @@ impl Atom {
     }
 }
 
+impl Default for Atom {
+    fn default() -> Self {
+        atom!("")
+    }
+}
+
 impl PartialEq<str> for Atom {
     fn eq(&self, other: &str) -> bool {
         &self[..] == other
@@ -215,6 +221,12 @@ impl PartialEq<Atom> for str {
     }
 }
 
+impl PartialEq<String> for Atom {
+    fn eq(&self, other: &String) -> bool {
+        &self[..] == &other[..]
+    }
+}
+
 impl<'a> From<Cow<'a, str>> for Atom {
     #[inline]
     fn from(string_to_add: Cow<'a, str>) -> Atom {

src/namespace.rs

@@ -15,7 +15,7 @@ use std::ops;
 /// An atom that is meant to represent a namespace in the HTML / XML sense.
 /// Whether a given string represents a namespace is contextual, so this is
 /// a transparent wrapper that will not catch all mistakes.
-#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Clone)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Clone, Default)]
 #[cfg_attr(feature = "heap_size", derive(HeapSizeOf))]
 pub struct Namespace(pub Atom);