cue: embedded scalar resulting from conditional fails

[cueckoo]

Originally opened by @myitcv in cuelang/cue#729

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

$ cue version
cue version +fdccfbc5 linux/amd64

Does this issue reproduce with the latest release?

Yes

What did you do?

exec cue eval

-- x.cue --
package x

_#cond: true

if _#cond {5}

What did you expect to see?

5

What did you see instead?

[stderr]
conflicting values 5 and {_#cond(:x):true,if _#cond(:x) {5}} (mismatched types int and struct):
    ./x.cue:1:1
    ./x.cue:5:12

[cueckoo]

Original reply by @mpvl in cuelang/cue#729 (comment)

FTR: this works:

_#cond: true

_
if _#cond {5}

But so does this:

{5}

In the spirit of the spec, at least, I would say the latter is correct. So this issue would be correct to call this a bug.

Also FTR: add this test case:

_#cond: true
if _#cond {5}
"v"

It currently crashes.