Support cutting elements from the slice with append

[alexvanin]

Sometimes you need to remove element from the slice and one of the convenient ways to that is to use append.

package foo
func Main() int {
	a := []int{0,1,2,3,4,5}
	a = append(a[:2], a[3:]...)
	return len(a)
}

This code does not compile in neo-go with (SUBSTR): can't convert Array to ByteArray message You have to create new slice, which is totally fine, but may be a bit confusing. So it would be nice to support this feature if possible.

[fyrchik]

This happens because subslicing is supported only for []byte via SUBSTR instruction.
There is no similar instruction for regular Arrays and the only way to support this is via loops (which can be done manually anyway).

However for your specific case, there is a REMOVE instruction, which can be wrapped in separate builtin in 2.x and possibly invoked directly after #941 .

[fyrchik]

Closed via #1021.
Your example:

package foo
import "github.com/nspcc-dev/neo-go/pkg/interop/util"
func Main() int {
	a := []int{0,1,2,3,4,5}
	util.Remove(a, 2)
	return len(a)
}