title: Attempting numpy conversion when not needed in cupy
body: <p>Using python3.8 with cupy-cuda111</p>
  <p>creating a cupy array and trying to cast to cp.int_ causes cupy assume an implicit conversion to numpy array</p>
  <pre><code>import cupy as cp
  
  def test_function(x):
      y = cp.int_(x * 10)
      return(y)
  
  x = cp.array([0.1, 0.2, 0.3, 0.4, 0.5])
  y = test_function(x)
  
  print(y)
  </code></pre>
  <p>This I assumed would multiply the scalar and return <code>([1, 2, 3, 4, 5], dtype=cp.int_)</code>
  but instead gives:</p>
  <pre><code>TypeError: Implicit conversion to a NumPy array is not allowed. Please use `.get()` to construct a NumPy array explicitly.
  </code></pre>
  <p>Why does this error get generated?</p>
  <p>How can I multiply and cast to int_ the cp.array?</p>