! cue eval -c -e b.a.b -e b.idx
cmp stderr expect-stderr
cmp stdout expect-stdout

-- expect-stdout --
// b.a.b
4
-- expect-stderr --
// b.idx
invalid non-ground value string (must be concrete string)
-- partial.cue --
package partial

def: *1 | int
sum: 1 | 2

b: {
	idx: a[str] // should resolve to top-level `a`
	str: string
}
b: a: b: 4
a: {
	b: 3
	c: 4
}
c: b & {str: "b"}