[Solved]-cannot find class manifest for element type T-scala

To provide type information you can use a context bound

def f[T : Manifest](a:T, b:T):Array[T] = { new Array[T](2) }

or the manifest as an implicit argument:

def f[T](a:T, b:T)(implicit manifest : Manifest[T]) : Array[T] = { new Array[T](2) }

The former is syntactic sugar for the later. The manifest is needed because the type information about T is missing due to generic type errasure of the JVM.