When you write

def check[T <: AnyVal] ...

you're defining the method for all the subtypes of AnyVal. However, your implementation uses two methods (<= and >=) which are available only for a subset of types, namely the ones that support ordering.

So you have to specify that the method applies to all types for which an ordering exists, or in other words

def check[T](value: T, min: T, max: T)(implicit ev: T => Ordered[T]): Boolean =
  value >= min && value <= max

This syntax is equivalent to a view bound (<%)

def check[T <% Ordered[T]](value: T, min: T, max: T): Boolean = ...

but, since view bounds are deprecated, you should avoid it.

---

Another option is to use Ordering in this fashion

def check[T](value: T, mini: T, maxi: T)(implicit ord: Ordering[T]): Boolean = {
  import ord.mkOrderingOps
  value >= mini && value <= maxi
}

where importing ord.mkOrderingOps gives you the ability of using the regular >= and <= methods.

Another equivalent alternative using a context bound directly:

def check[T: Ordering](value: T, mini: T, maxi: T): Boolean = {
  val ord = implicitly[Ordering[T]]
  import ord.mkOrderingOps
  value >= mini && value <= maxi
}