diff --git a/modules/@angular/core/src/metadata/lifecycle_hooks.ts b/modules/@angular/core/src/metadata/lifecycle_hooks.ts
index 81597293df..7423e0c8e7 100644
--- a/modules/@angular/core/src/metadata/lifecycle_hooks.ts
+++ b/modules/@angular/core/src/metadata/lifecycle_hooks.ts
@@ -86,9 +86,7 @@ export var LIFECYCLE_HOOKS_VALUES = [
  * ```
  * @stable
  */
-export abstract class OnChanges {
-  abstract ngOnChanges(changes: SimpleChanges): any /** TODO #9100 */;
-}
+export abstract class OnChanges { abstract ngOnChanges(changes: SimpleChanges): void; }
 
 /**
  * Implement this interface to execute custom initialization logic after your directive's
@@ -132,7 +130,7 @@ export abstract class OnChanges {
  *  ```
  * @stable
  */
-export abstract class OnInit { abstract ngOnInit(): any /** TODO #9100 */; }
+export abstract class OnInit { abstract ngOnInit(): void; }
 
 /**
  * Implement this interface to supplement the default change detection algorithm in your directive.
@@ -201,7 +199,7 @@ export abstract class OnInit { abstract ngOnInit(): any /** TODO #9100 */; }
  * ```
  * @stable
  */
-export abstract class DoCheck { abstract ngDoCheck(): any /** TODO #9100 */; }
+export abstract class DoCheck { abstract ngDoCheck(): void; }
 
 /**
  * Implement this interface to get notified when your directive is destroyed.
@@ -293,7 +291,7 @@ export abstract class DoCheck { abstract ngDoCheck(): any /** TODO #9100 */; }
  *
  * @stable
  */
-export abstract class OnDestroy { abstract ngOnDestroy(): any /** TODO #9100 */; }
+export abstract class OnDestroy { abstract ngOnDestroy(): void; }
 
 /**
  * Implement this interface to get notified when your directive's content has been fully
@@ -347,7 +345,7 @@ export abstract class OnDestroy { abstract ngOnDestroy(): any /** TODO #9100 */;
  * ```
  * @stable
  */
-export abstract class AfterContentInit { abstract ngAfterContentInit(): any /** TODO #9100 */; }
+export abstract class AfterContentInit { abstract ngAfterContentInit(): void; }
 
 /**
  * Implement this interface to get notified after every check of your directive's content.
@@ -396,9 +394,7 @@ export abstract class AfterContentInit { abstract ngAfterContentInit(): any /**
  * ```
  * @stable
  */
-export abstract class AfterContentChecked {
-  abstract ngAfterContentChecked(): any /** TODO #9100 */;
-}
+export abstract class AfterContentChecked { abstract ngAfterContentChecked(): void; }
 
 /**
  * Implement this interface to get notified when your component's view has been fully initialized.
@@ -446,7 +442,7 @@ export abstract class AfterContentChecked {
  * ```
  * @stable
  */
-export abstract class AfterViewInit { abstract ngAfterViewInit(): any /** TODO #9100 */; }
+export abstract class AfterViewInit { abstract ngAfterViewInit(): void; }
 
 /**
  * Implement this interface to get notified after every check of your component's view.
@@ -497,4 +493,4 @@ export abstract class AfterViewInit { abstract ngAfterViewInit(): any /** TODO #
  * ```
  * @stable
  */
-export abstract class AfterViewChecked { abstract ngAfterViewChecked(): any /** TODO #9100 */; }
+export abstract class AfterViewChecked { abstract ngAfterViewChecked(): void; }
diff --git a/modules/@angular/core/src/util/decorators.ts b/modules/@angular/core/src/util/decorators.ts
index 40adba0515..49a2bb38f0 100644
--- a/modules/@angular/core/src/util/decorators.ts
+++ b/modules/@angular/core/src/util/decorators.ts
@@ -103,24 +103,24 @@ function applyParams(fnOrArray: (Function | any[]), key: string): Function {
   if (isFunction(fnOrArray)) {
     return <Function>fnOrArray;
   } else if (fnOrArray instanceof Array) {
-    var annotations: any[] = fnOrArray;
-    var fn: Function = fnOrArray[fnOrArray.length - 1];
+    const annotations: any[] = fnOrArray;
+    const annoLength = annotations.length - 1;
+    const fn: Function = fnOrArray[annoLength];
     if (!isFunction(fn)) {
       throw new Error(
           `Last position of Class method array must be Function in key ${key} was '${stringify(fn)}'`);
     }
-    var annoLength = annotations.length - 1;
     if (annoLength != fn.length) {
       throw new Error(
           `Number of annotations (${annoLength}) does not match number of arguments (${fn.length}) in the function: ${stringify(fn)}`);
     }
-    var paramsAnnotations: any[][] = [];
-    for (var i = 0, ii = annotations.length - 1; i < ii; i++) {
-      var paramAnnotations: any[] = [];
+    const paramsAnnotations: any[][] = [];
+    for (let i = 0, ii = annotations.length - 1; i < ii; i++) {
+      const paramAnnotations: any[] = [];
       paramsAnnotations.push(paramAnnotations);
-      var annotation = annotations[i];
+      const annotation = annotations[i];
       if (annotation instanceof Array) {
-        for (var j = 0; j < annotation.length; j++) {
+        for (let j = 0; j < annotation.length; j++) {
           paramAnnotations.push(extractAnnotation(annotation[j]));
         }
       } else if (isFunction(annotation)) {
@@ -220,9 +220,9 @@ function applyParams(fnOrArray: (Function | any[]), key: string): Function {
  * @stable
  */
 export function Class(clsDef: ClassDefinition): ConcreteType<any> {
-  var constructor = applyParams(
+  const constructor = applyParams(
       clsDef.hasOwnProperty('constructor') ? clsDef.constructor : undefined, 'constructor');
-  var proto = constructor.prototype;
+  let proto = constructor.prototype;
   if (clsDef.hasOwnProperty('extends')) {
     if (isFunction(clsDef.extends)) {
       (<Function>constructor).prototype = proto =
@@ -232,7 +232,7 @@ export function Class(clsDef: ClassDefinition): ConcreteType<any> {
           `Class definition 'extends' property must be a constructor function was: ${stringify(clsDef.extends)}`);
     }
   }
-  for (var key in clsDef) {
+  for (let key in clsDef) {
     if (key != 'extends' && key != 'prototype' && clsDef.hasOwnProperty(key)) {
       proto[key] = applyParams(<any>clsDef[key], key);
     }
@@ -243,7 +243,7 @@ export function Class(clsDef: ClassDefinition): ConcreteType<any> {
   }
 
   if (!constructor['name']) {
-    (constructor as any /** TODO #9100 */)['overriddenName'] = `class${_nextClassId++}`;
+    (constructor as any)['overriddenName'] = `class${_nextClassId++}`;
   }
 
   return <ConcreteType<any>>constructor;
@@ -258,25 +258,22 @@ var Reflect = global.Reflect;
   }
 })();
 
-export function makeDecorator(
-    annotationCls: any /* TODO #9100 */,
-    chainFn: (fn: Function) => void = null): (...args: any[]) => (cls: any) => any {
-  function DecoratorFactory(objOrType: any /** TODO #9100 */): (cls: any) => any {
-    var annotationInstance = new (<any>annotationCls)(objOrType);
+export function makeDecorator(annotationCls: any, chainFn: (fn: Function) => void = null):
+    (...args: any[]) => (cls: any) => any {
+  function DecoratorFactory(objOrType: any): (cls: any) => any {
+    const annotationInstance = new (<any>annotationCls)(objOrType);
     if (this instanceof annotationCls) {
       return annotationInstance;
     } else {
-      var chainAnnotation =
+      const chainAnnotation =
           isFunction(this) && this.annotations instanceof Array ? this.annotations : [];
       chainAnnotation.push(annotationInstance);
-      var TypeDecorator: TypeDecorator =
-          <TypeDecorator>function TypeDecorator(cls: any /** TODO #9100 */) {
-            var annotations = Reflect.getOwnMetadata('annotations', cls);
-            annotations = annotations || [];
-            annotations.push(annotationInstance);
-            Reflect.defineMetadata('annotations', annotations, cls);
-            return cls;
-          };
+      const TypeDecorator: TypeDecorator = <TypeDecorator>function TypeDecorator(cls: Type) {
+        const annotations = Reflect.getOwnMetadata('annotations', cls) || [];
+        annotations.push(annotationInstance);
+        Reflect.defineMetadata('annotations', annotations, cls);
+        return cls;
+      };
       TypeDecorator.annotations = chainAnnotation;
       TypeDecorator.Class = Class;
       if (chainFn) chainFn(TypeDecorator);
@@ -288,8 +285,8 @@ export function makeDecorator(
   return DecoratorFactory;
 }
 
-export function makeParamDecorator(annotationCls: any /** TODO #9100 */): any {
-  function ParamDecoratorFactory(...args: any[] /** TODO #9100 */): any {
+export function makeParamDecorator(annotationCls: any): any {
+  function ParamDecoratorFactory(...args: any[]): any {
     var annotationInstance = Object.create(annotationCls.prototype);
     annotationCls.apply(annotationInstance, args);
     if (this instanceof annotationCls) {
@@ -300,11 +297,8 @@ export function makeParamDecorator(annotationCls: any /** TODO #9100 */): any {
     }
 
 
-    function ParamDecorator(
-        cls: any /** TODO #9100 */, unusedKey: any /** TODO #9100 */,
-        index: any /** TODO #9100 */): any {
-      var parameters: any[][] = Reflect.getMetadata('parameters', cls);
-      parameters = parameters || [];
+    function ParamDecorator(cls: any, unusedKey: any, index: number): any {
+      const parameters: any[][] = Reflect.getMetadata('parameters', cls) || [];
 
       // there might be gaps if some in between parameters do not have annotations.
       // we pad with nulls.
@@ -325,8 +319,8 @@ export function makeParamDecorator(annotationCls: any /** TODO #9100 */): any {
   return ParamDecoratorFactory;
 }
 
-export function makePropDecorator(annotationCls: any /** TODO #9100 */): any {
-  function PropDecoratorFactory(...args: any[] /** TODO #9100 */): any {
+export function makePropDecorator(annotationCls: any): any {
+  function PropDecoratorFactory(...args: any[]): any {
     var decoratorInstance = Object.create(annotationCls.prototype);
     annotationCls.apply(decoratorInstance, args);
 
@@ -334,8 +328,7 @@ export function makePropDecorator(annotationCls: any /** TODO #9100 */): any {
       return decoratorInstance;
     } else {
       return function PropDecorator(target: any, name: string) {
-        var meta = Reflect.getOwnMetadata('propMetadata', target.constructor);
-        meta = meta || {};
+        const meta = Reflect.getOwnMetadata('propMetadata', target.constructor) || {};
         meta[name] = meta[name] || [];
         meta[name].unshift(decoratorInstance);
         Reflect.defineMetadata('propMetadata', meta, target.constructor);
diff --git a/tools/public_api_guard/core/index.d.ts b/tools/public_api_guard/core/index.d.ts
index ee4e59b9c9..3a68256e3c 100644
--- a/tools/public_api_guard/core/index.d.ts
+++ b/tools/public_api_guard/core/index.d.ts
@@ -7,22 +7,22 @@ export declare class AbstractProviderError extends BaseException {
 
 /** @stable */
 export declare abstract class AfterContentChecked {
-    abstract ngAfterContentChecked(): any;
+    abstract ngAfterContentChecked(): void;
 }
 
 /** @stable */
 export declare abstract class AfterContentInit {
-    abstract ngAfterContentInit(): any;
+    abstract ngAfterContentInit(): void;
 }
 
 /** @stable */
 export declare abstract class AfterViewChecked {
-    abstract ngAfterViewChecked(): any;
+    abstract ngAfterViewChecked(): void;
 }
 
 /** @stable */
 export declare abstract class AfterViewInit {
-    abstract ngAfterViewInit(): any;
+    abstract ngAfterViewInit(): void;
 }
 
 /** @experimental */
@@ -686,7 +686,7 @@ export declare function disposePlatform(): void;
 
 /** @stable */
 export declare abstract class DoCheck {
-    abstract ngDoCheck(): any;
+    abstract ngDoCheck(): void;
 }
 
 /** @deprecated */
@@ -972,17 +972,17 @@ export declare class NoProviderError extends AbstractProviderError {
 
 /** @stable */
 export declare abstract class OnChanges {
-    abstract ngOnChanges(changes: SimpleChanges): any;
+    abstract ngOnChanges(changes: SimpleChanges): void;
 }
 
 /** @stable */
 export declare abstract class OnDestroy {
-    abstract ngOnDestroy(): any;
+    abstract ngOnDestroy(): void;
 }
 
 /** @stable */
 export declare abstract class OnInit {
-    abstract ngOnInit(): any;
+    abstract ngOnInit(): void;
 }
 
 /** @stable */