The "indices" of an IndexPath refers to what you can subscript it with, not its contents.

import Foundation

let indexPath = IndexPath(indexes: [1,3])
print(indexPath[1])

IndexPath itself is a Sequence (via Collection) which can give you the answer you expect:

import Foundation

let indexPath = IndexPath(indexes: [1,3])

var indices = [Int]()
for index in indexPath {
    indices.append(index)
}

print(indices)

Comment by Sam Stigler (JIRA)

Ah, okay. That makes more sense; thanks for clearing it up for me. indices makes it sound like those are its component (and possibly non-contiguous) indices, but I see that name is required for IndexPath's RandomAccessCollection conformance.