*
 * // use case code
 * fun useCase() {
 *   analyse(function) {
 *    // 'getConstantFromExpressionBody' is an imaginary function
 *    val valueBefore = function.getConstantFromExpressionBody() // valueBefore is 0
 *
 *    changeExpressionBodyTo(1) // now function will looks like `fun foo(): Int = 1`
 *    val valueAfter = function.getConstantFromExpressionBody() // Wrong way: valueAfter is not guarantied to be '1'
 *   }
 *