Make DelayedPromise conform to Equatable

Fixes #37.

README.md

@@ -360,6 +360,12 @@ Unless you explicitly state otherwise, any contribution intentionally submitted
 
 ## Version History
 
+### Development
+
+- Make `DelayedPromise` conform to `Equatable` ([#37][]).
+
+[#37]: https://github.com/lilyball/Tomorrowland/issues/37 "DelayedPromise should conform to Equatable"
+
 ### v0.5.1
 
 - When chaining multiple `.main` context blocks in the same runloop pass, ensure we release each block before executing the next one.

Sources/DelayedPromise.swift

@@ -32,7 +32,7 @@ public typealias StdDelayedPromise<Value> = DelayedPromise<Value,Swift.Error>
 ///     avatar.promise.then { [weak self] (image) in
 ///         self?.imageView.image = image
 ///     }
-public struct DelayedPromise<Value,Error> {
+public struct DelayedPromise<Value,Error>: Equatable {
     /// The type of the promise resolver. See `Promise<Value,Error>.Resolver`.
     public typealias Resolver = Promise<Value,Error>.Resolver
 
@@ -64,6 +64,11 @@ public struct DelayedPromise<Value,Error> {
     public var promise: Promise<Value,Error> {
         return _box.toPromise(with: _seal)
     }
+
+    /// Two `DelayedPromise`s compare as equal if they would produce equal `Promise`s.
+    public static func ==(lhs: DelayedPromise, rhs: DelayedPromise) -> Bool {
+        return lhs._box === rhs._box
+    }
 }
 
 // MARK: -