eval: invalid structural cycle error with matchN

[rogpeppe]

What version of CUE are you using (cue version)?

$ cue version
e48fb9db492048b213b6a56fdce5c3660e69a189

Does this issue reproduce with the latest stable release?

N/A

What did you do?

env CUE_EXPERIMENT=evalv3
exec cue export x.cue

-- x.cue --
_s
_s: {
    #x: matchN(1, [_s, [..._s]])
}

What did you expect to see?

Passing test.

What did you see instead?

> env CUE_EXPERIMENT=evalv3
> exec cue export x.cue
[stderr]
0: structural cycle:
    ./x.cue:3:19
_s.0: structural cycle:
    ./x.cue:3:19
[exit status 1]
FAIL: /tmp/testscript4122338254/x.txtar/script.txtar:2: unexpected command failure

[mpvl]

FTR: this also happens with or:

s: or([s, []])