Unused output variable

[anderseknert]

foo {
	some x
	input[x]
}

Even in strict mode, OPA considers x to be "used", as it's referenced somewhere. Howver, unless x is referenced later in the rule (or in the rule head) it's not really used, and the above could be replaced by:

foo {
	input[_]
}

Or

foo {
	some _ in input
}