slice[:1][0] vs slice[0] in go

In the documentation of the unsafe.SliceData function in go, it says:

SliceData returns a pointer to the underlying array of the argument
slice.

• If cap(slice) > 0, SliceData returns &slice[:1][0].

What’s the logic behind returning &slice[:1][0] instead of &slice[0]? As far as I’m aware (and my tests confirm), both would return the same address. Is there a specific reason that go developers chose to use the former rather than the latter?

>Solution :

A slice may have a positive capacity (cap(slice) > 0), but it may have 0 length at the same time. Indexing it like slice[0] would result in a runtime panic.

If a slice has positive capacity, you may slice it like slice[:1] which will result in a slice that will have a length of 1, and you may index it like slice[0] without resulting in a runtime panic.

For example:

slice := make([]int, 0, 5)
fmt.Println(&slice[0]) 

This results in:

panic: runtime error: index out of range [0] with length 0

But this works:

fmt.Println(&slice[:1][0])