Issue #553
-- in.cue --
a: "foo" @test(eq, "foo")
b: "boo" @test(eq, "boo")
commands: {
	#c: {
		help: "help!"
	}
}
out: """
    a is \(a)
    b is \(b)

    c is \(commands.#c.help)
    d is \(commands.#d.help)
    """ @test(err, code=incomplete)
-- out/errors.txt --
[incomplete] out: invalid interpolation: undefined field: #d:
    ./in.cue:8:6
    ./in.cue:13:21
-- out/eval/stats --
Leaks:  0
Freed:  7
Reused: 3
Allocs: 4
Retain: 0

Unifications: 7
Conjuncts:    11
Disjuncts:    7
