Get PartialEq on Value types working correctly. Yay!

src/types/mod.rs

@@ -15,17 +15,44 @@ pub struct Boolean(bool);
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct Character(char);
 
-pub trait Value: Debug + 'static { }
-impl Value for Boolean { }
-impl Value for Character { }
+pub trait Value: Debug + ValueEq {
+    fn as_value(&self) -> &Value;
+}
 
-impl<'a,'b> PartialEq<&'a Value> for &'b Value {
-    fn eq(&self, other: &&Value) -> bool {
-        other.as_any().downcast_ref::<Self>().map_or(false, |x| x == self)
+/// A trait on value types that makes it easier to compare values of disparate types. The methods
+/// provided by this trait are used by the PartialEq implementation on Values.
+pub trait ValueEq {
+    fn eq(&self, other: &Value) -> bool;
+    fn as_any(&self) -> &Any;
+}
+
+impl<'lhs,'rhs> PartialEq<Value+'rhs> for Value+'lhs {
+    fn eq(&self, other: &(Value+'rhs)) -> bool {
+        ValueEq::eq(self, other)
     }
 }
 
-impl Value {
+impl Value for Boolean {
+    fn as_value(&self) -> &Value { self }
+}
+
+impl ValueEq for Boolean {
+    fn eq(&self, other: &Value) -> bool {
+        other.as_any().downcast_ref::<Self>().map_or(false, |x| x == self)
+    }
+
+    fn as_any(&self) -> &Any { self }
+}
+
+impl Value for Character {
+    fn as_value(&self) -> &Value { self }
+}
+
+impl ValueEq for Character {
+    fn eq(&self, other: &Value) -> bool {
+        other.as_any().downcast_ref::<Self>().map_or(false, |x| x == self)
+    }
+
     fn as_any(&self) -> &Any { self }
 }
 
@@ -39,4 +66,15 @@ mod tests {
         assert_eq!(Boolean(false), Boolean(false));
         assert_ne!(Boolean(true), Boolean(false));
     }
+
+    #[test]
+    fn equal_chars_are_equal() {
+        assert_eq!(Character('a'), Character('a'));
+        assert_eq!(Character('a').as_value(), Character('a').as_value());
+    }
+
+    #[test]
+    fn booleans_and_chars_are_not_equal() {
+        assert_ne!(Boolean(true).as_value(), Character('a').as_value());
+    }
 }