Unexpected slice behavior

[Roel van der Goot]

package main

import "fmt"

func main() {
slice := []int{1, 2}
rest := append(slice[:0], slice[1:]...)
fmt.Printf("slice = %+v, rest = %+v\n", slice, rest)
}

Actual output:

slice = [2 2], rest = [2]

Expected output:

slice = [1 2], rest = [2]

https://go.dev/play/p/GU5h_45dPg9

Go 1.25.3 and 1.25.4

Am I missing something?

[Ian Lance Taylor]

Please see https://go.dev/blog/slices .

Ian

[Roel van der Goot]

Thank you. I am sure I read that blog post before, but I didn't understand the ramifications. For performance reasons it makes sense, but it remains a bit unexpected to me that rest := append(slice[:i], slice[j:]...) and rest := slices.Delete(slice, i, j) have a side effect on slice (as documented in slices.Delete). Thank you again.