Code Transformation Issues in Move-Instance-Method Refactorings

Refactorings, by definition, preserve the behavior of a target program. Such a strong semantic property is encoded by a set of preconditions for each refactoring. Only if all preconditions are satisfied will a target program be transformed. The code transformation that implements the refactoring follows another set of rules to produce syntactically-correct, refactored code. Consequently, it is easy to believe that most behavior-changing violations in refactorings are induced by incorrect preconditions or lack of required checks. In this paper, however, we show that code transformations for Move-Instance-Method Refactoring available in several popular Java Integrated Development Environments do not preserve program behavior. We report these errors and propose solutions for each identified problem.