-- in.cue --
disallowTopAsAlias: {
	_=X: 1
}

disallowTopAsLet: {
	let _ = 1
}

disallowTopAsLabel: {
	_: 1
	a: _ // Should not compile to a reference.
}

// TODO: disallow dollar as label? This is according to the spec, but it
// will be a breaking change and $ was reserved for referring to the root of
// a file, which we very likely will never implement.
// disallowDollarAsLabel: {
//   $: 1
// }

-- out/compile --
disallowTopAsAlias: cannot use _ as alias or let clause:
    ./in.cue:2:2
disallowTopAsLet: cannot use _ as alias or let clause:
    ./in.cue:6:6
disallowTopAsLabel: cannot use _ as label:
    ./in.cue:10:2
--- in.cue
{
  disallowTopAsAlias: {
    X: 1
  }
  disallowTopAsLet: {
    let _ = 1
  }
  disallowTopAsLabel: {
    _|_(cannot use _ as label)
    a: _
  }
}
-- out/eval --
disallowTopAsAlias: cannot use _ as alias or let clause:
    ./in.cue:2:2
disallowTopAsLet: cannot use _ as alias or let clause:
    ./in.cue:6:6
disallowTopAsLabel: cannot use _ as label:
    ./in.cue:10:2