`List(42).indexOfSlice(Nil, 1) == -1`

[noresttherein]

Scala version: 2.13.16

As in the title. I believe this is new, and I think the general expectation here would be that length is a valid index of an empty subsequence.

[som-snytt]

I noticed that it checks the bounds first. Usually an empty matches at beginning or end (thinking of splitting with a regex). But I also recall a discussion about whether returning an index must return a valid index for the collection.

This is not yet fixed my WIP, which breaks it more; I'm not sure about my expectation. Behavior is unchanged for the indexed case.

Worth adding that putting the example in the title is slightly less convenient for copying.

[sjrd]

The expected result is 1. All languages agree on that for similar APIs.

[Ichoran]

Scala also agrees that it is 1 for other types that use a different code path.

[som-snytt]

Maybe I was thinking of patch, which will clip at length, i.e., append. I'll adjust it.

Edit: I have a vague memory that that might have been the discussion about which API are relaxed about indexes; see the recent thread on the forum about whether tail should throw.