Update due to merge conflicts, test memory leak issue

change/@microsoft-fast-foundation-e29676d4-d69a-4915-ae60-66ce6e649a92.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Fix memory leak due to binding observers",
+  "packageName": "@microsoft/fast-foundation",
+  "email": "7282195+m-akinc@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

packages/web-components/fast-foundation/src/design-token/design-token.ts

@@ -93,7 +93,8 @@ export interface CSSDesignToken<
         | ({
               createCSS?(): string;
           } & Record<PropertyKey, any>)
-> extends DesignToken<T>, CSSDirective {
+> extends DesignToken<T>,
+        CSSDirective {
     /**
      * The {@link (DesignToken:interface)} formatted as a CSS custom property if the token is
      * configured to write a CSS custom property.
@@ -128,8 +129,10 @@ export interface DesignTokenSubscriber<T extends DesignToken<any>> {
 /**
  * Implementation of {@link (DesignToken:interface)}
  */
-class DesignTokenImpl<T extends { createCSS?(): string }> extends CSSDirective
-    implements DesignToken<T> {
+class DesignTokenImpl<T extends { createCSS?(): string }>
+    extends CSSDirective
+    implements DesignToken<T>
+{
     public readonly name: string;
     public readonly cssCustomProperty: string | undefined;
     public readonly id: string;
@@ -314,8 +317,8 @@ class DesignTokenImpl<T extends { createCSS?(): string }> extends CSSDirective
      * @param token - the token to alias to
      */
     private alias(token: DesignToken<T>): DerivedDesignTokenValue<T> {
-        return (((target: HTMLElement) =>
-            token.getValueFor(target)) as unknown) as DerivedDesignTokenValue<T>;
+        return ((target: HTMLElement) =>
+            token.getValueFor(target)) as unknown as DerivedDesignTokenValue<T>;
     }
 }
 
@@ -390,10 +393,10 @@ class DesignTokenBindingObserver<T extends { createCSS?(): string }> {
             this.node.store.set(
                 this.token,
 
-                (this.observer.observe(
+                this.observer.observe(
                     this.node.target,
                     defaultExecutionContext
-                ) as unknown) as StaticDesignTokenValue<T>
+                ) as unknown as StaticDesignTokenValue<T>
             );
         } catch (e) {
             console.error(e);
@@ -704,6 +707,9 @@ class DesignTokenNode implements Behavior, Subscriber {
             const parent = childToParent.get(this)!;
             parent.removeChild(this);
         }
+        for (const token of this.bindingObservers.keys()) {
+            this.tearDownBindingObserver(token);
+        }
     }
 
     /**