Most advanced existing tools for clone-based refactoring propose a limited number of predefined clone-removal transformations that can be applied automatically, typically under user control. This fixed set of refactorings usually guarantee that semantics is preserved, but is inherently limited to generally-applicable transformations (extract method, pull-up method, etc.). This tool design rules out many potential domain-specific or application-specific clone removals. Such cases are ordinarily recognized by humans as stereotypes derived from a higher-level concept and manually replaced with an appropriate abstraction. Thus, in current tools, generality is sacrificed for the safety of the transformation. This paper proposes an alternative approach, in which the spectrum of refactoring techniques is open, including manual interventions, while keeping strong safety guarantees based on the notion of iso-generation. Our method can operate on multiple languages and has been prototyped on a subset of a real-world legacy asset containing C and COBOL programs, with promising results.
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