Merge pull request #2635 from Microsoft/fixParameterDecoratorTyping

Fix for #2249

Author: rbuckton

src/lib/core.d.ts

@@ -1168,4 +1168,4 @@ interface TypedPropertyDescriptor<T> {
 declare type ClassDecorator = <TFunction extends Function>(target: TFunction) => TFunction | void;
 declare type PropertyDecorator = (target: Object, propertyKey: string | symbol) => void;
 declare type MethodDecorator = <T>(target: Object, propertyKey: string | symbol, descriptor: TypedPropertyDescriptor<T>) => TypedPropertyDescriptor<T> | void;
-declare type ParameterDecorator = (target: Function, propertyKey: string | symbol, parameterIndex: number) => void;
+declare type ParameterDecorator = (target: Object, propertyKey: string | symbol, parameterIndex: number) => void;