cue: data-only mode does not allow #-quoted labels

[rogpeppe]

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

5a998808e4b76537e72996b0bf28fbf9eae9b189

Does this issue reproduce with the latest stable release?

Yes

What did you do?

exec cue export x.cue
cmp stdout want-stdout

exec cue export data: x.cue
cmp stdout want-stdout

-- want-stdout
{
    "a": 1
}
-- x.cue --
{
	"a": 1
	#"a"#: 1
	"\u0061": 1
	#"\#u0061"#: 1
}

What did you expect to see?

A passing test. There's nothing non-data in the file and cue export without the data restriction runs fine.

What did you see instead?

> exec cue export x.cue
[stdout]
{
    "a": 1
}
> cmp stdout want-stdout
> exec cue export data: x.cue
[stderr]
optional fields not allowed in data mode:
    ./x.cue:3:2
optional fields not allowed in data mode:
    ./x.cue:5:2
[exit status 1]
FAIL: /tmp/x.txtar:4: unexpected command failure