return x
		}
		return or(x1, y1)
	}
}

// appendSplitAnd appends x to list while splitting apart any top-level && expressions.
// For example, appendSplitAnd({W}, X && Y && Z) = {W, X, Y, Z}.
func appendSplitAnd(list []Expr, x Expr) []Expr {
	if x, ok := x.(*AndExpr); ok {
		list = appendSplitAnd(list, x.X)
		list = appendSplitAnd(list, x.Y)
		return list
	}
	return append(list, x)
}