Go copy（）是否可以有效处理无操作副本？

Does the following code copy 30 bytes, returning in O(n) in the general case - or "realize" it doesn't have to, and return in constant time?

sliceA := make([]byte, 120)
sliceB := sliceA[0:30]
copy(sliceA, sliceB)

I'm using Go 1.6.