Be Realistic: Automated Program Repair is a Combination of Undecidable Problems

Automated program repair (APR) tools have promising results, but what are APR's limits? The answer could help researchers design tool trade-offs and manage user expectations. Since APR is undecidable, as are two of its typical phases, tools must use conservative approximations. Such approximations can help APR tools be better understood and can lead to a theory of sound APR.