This is such an interesting choice of example because this particular implicit is baked into the language, and the discomfort you feel is a fine measure of how good an idea this is. Last I checked there was no way to turn it off.

  scala> def f(x: Float) = x.round
  f: (x: Float)Int

  scala> f(123456789)
  res0: Int = 123456792

But of course it doesn't stop at converting Ints into Floats.

  scala> f(Long.MaxValue)
  res1: Int = 2147483647

So it seems 9223372036854775807 rounds to 2147483647. This can be a real simplifier if your "big data" is getting too big.