From b26095e9fac0af54fe1d56a42b83dffb928a4a77 Mon Sep 17 00:00:00 2001
From: Thomas Butler <thomas@butlersoftwarellc.com>
Date: Fri, 6 Dec 2013 06:10:12 -0500
Subject: [PATCH] Fixed KnockoutComputed polymorphism

Changed KnockoutComputed to inherit KnockoutObservable to enable
polymorphic/covariant reference conversion (see included unit test for
example).
---
 knockout/knockout.d.ts           | 11 ++++-------
 knockout/tests/knockout-tests.ts | 13 +++++++++++++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/knockout/knockout.d.ts b/knockout/knockout.d.ts
index aa6044e9f..b41846ca5 100644
--- a/knockout/knockout.d.ts
+++ b/knockout/knockout.d.ts
@@ -68,11 +68,8 @@ interface KnockoutComputedStatic {
     (options?: any): KnockoutComputed<any>;
 }
 
-interface KnockoutComputed<T> extends KnockoutSubscribable<T>, KnockoutComputedFunctions<T> {
-	(): T;
-	(value: T): void;
-
-	peek(): T;
+interface KnockoutComputed<T> extends KnockoutObservable<T>, KnockoutComputedFunctions<T> {
+	
 	dispose(): void;
 	isActive(): boolean;
 	getDependenciesCount(): number;
@@ -100,8 +97,8 @@ interface KnockoutObservable<T> extends KnockoutSubscribable<T>, KnockoutObserva
 	(value: T): void;
 
 	peek(): T;
-	valueHasMutated(): void;
-	valueWillMutate(): void;
+	valueHasMutated?:{(): void;};
+	valueWillMutate?:{(): void;};
     extend(requestedExtenders: { [key: string]: any; }): KnockoutObservable<T>;
 }
 
diff --git a/knockout/tests/knockout-tests.ts b/knockout/tests/knockout-tests.ts
index b0755c12a..fb3955241 100644
--- a/knockout/tests/knockout-tests.ts
+++ b/knockout/tests/knockout-tests.ts
@@ -570,4 +570,17 @@ function test_misc() {
     ko.utils.domNodeDisposal.addDisposeCallback(element, function () {
         $(element).datepicker("destroy");
     });
+	
+	this.observableFactory = function(): KnockoutObservable<number>{
+	    if (true) {
+			return ko.computed({
+				read:function(){ 
+					return 3; 
+				}
+			});
+		} else {
+			return ko.observable(3);
+		}
+	}
+	
 }
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