-- in.cue --
import "list"

repeat: {
    [string]: {x: _, n: int, v: list.Repeat(x, n)}

    t1: {x: [], n: 0}
    t2: {x: [1], n: 0}

    t3: {x: [1], n: 1}
    t4: {x: [1, 2], n: 1}

    t5: {x: [], n: 3}
    t6: {x: [1, 2], n: 3}
    t7: {x: [1, 2, 3, 4], n: 3}

    t8: {x: [1],  n: -1}
}
concat: {
    [string]: {x: _, v: list.Concat(x)}

    t1: x: []
    t2: x: [[]]

    t3: x: [[1]]
    t4: x: [[1, 2]]
    t5: x: [[1], [2]]

    t6: x: [[1, 2], [3, 4]]

    t7: x: 1
    t8: x: [1, [2]]
}
-- out/list --
Errors:
error in call to list.Concat: cannot use value 1 (type int) as list
error in call to list.Repeat: negative count
concat.t7.v: cannot use 1 (type int) as list in argument 1 to list.Concat:
    ./in.cue:30:12

Result:
repeat: {
	t1: {
		x: []
		n: 0
		v: []
	}
	t2: {
		x: [1]
		n: 0
		v: []
	}
	t3: {
		x: [1]
		n: 1
		v: [1]
	}
	t4: {
		x: [1, 2]
		n: 1
		v: [1, 2]
	}
	t5: {
		x: []
		n: 3
		v: []
	}
	t6: {
		x: [1, 2]
		n: 3
		v: [1, 2, 1, 2, 1, 2]
	}
	t7: {
		x: [1, 2, 3, 4]
		n: 3
		v: [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4]
	}
	t8: {
		x: [1]
		n: -1
		v: _|_ // error in call to list.Repeat: negative count (and 1 more errors)
	}
}
concat: {
	t1: {
		x: []
		v: []
	}
	t2: {
		x: [[]]
		v: []
	}
	t3: {
		x: [[1]]
		v: [1]
	}
	t4: {
		x: [[1, 2]]
		v: [1, 2]
	}
	t5: {
		x: [[1], [2]]
		v: [1, 2]
	}
	t6: {
		x: [[1, 2], [3, 4]]
		v: [1, 2, 3, 4]
	}
	t7: {
		x: 1
		v: _|_ // concat.t7.v: cannot use 1 (type int) as list in argument 1 to list.Concat
	}
	t8: {
		x: [1, [2]]
		v: _|_ // error in call to list.Concat: cannot use value 1 (type int) as list (and 1 more errors)
	}
}