Variant of 47 where the comprehension makes use of the value of the
key-value pair.

#skip-v2
-- a.cue --
d: port: 8080
s: {
	x: {
		port: 8080
	}
	y: {
		port: 8080
	}
}
for k, v in s {
	s: (k): d
	s: (k): portCopy: v.port
}
-- out/trim-v3 --
== a.cue
d: port: 8080
s: {
	x: _
	y: _
}
for k, v in s {
	s: (k): d
	s: (k): portCopy: v.port
}
-- out/trim-v3-noshare --
== a.cue
d: port: 8080
s: {
	x: _
	y: _
}
for k, v in s {
	s: (k): d
	s: (k): portCopy: v.port
}
