How to know if an object is an instance of a TypeTag's type?

I have a function which is able to know if an object is an instance of a Manifest's type. I would like to migrate it to a TypeTag version. The old function is the following one:

def myIsInstanceOf[T: Manifest](that: Any) = 
  implicitly[Manifest[T]].erasure.isInstance(that)

I have been experimenting with the TypeTags and now I have this TypeTag version:

// Involved definitions
def myInstanceToTpe[T: TypeTag](x: T) = typeOf[T]
def myIsInstanceOf[T: TypeTag, U: TypeTag](tag: TypeTag[T], that: U) = 
  myInstanceToTpe(that) stat_<:< tag.tpe

// Some invocation examples
class A
class B extends A
class C

myIsInstanceOf(typeTag[A], new A)        /* true */
myIsInstanceOf(typeTag[A], new B)        /* true */
myIsInstanceOf(typeTag[A], new C)        /* false */

Is there any better way to achieve this task? Can the parameterized U be omitted, using an Any instead (just as it is done in the old function)?

Solution

If it suffices to use subtyping checks on erased types, do as Travis Brown suggested in the comment above:

def myIsInstanceOf[T: ClassTag](that: Any) =
  classTag[T].runtimeClass.isInstance(that)

Otherwise you need to explicitly spell out the U type, so that scalac captures its type in a type tag:

def myIsInstanceOf[T: TypeTag, U: TypeTag] =
  typeOf[U] <:< typeOf[T]