Constraint-Based Refactoring with Foresight

Constraint-based refactoring tools as currently implemented generate their required constraint sets from the programs to be refactored, before any changes are performed. Constraint generation is thus unable to see — and regard — the changed structure of the refactored program, although this new structure may give rise to new constraints that need to be satisfied for the program to maintain its original behaviour. To address this problem, we present a framework allowing the constraint-generation process to foresee all changes a refactoring might perform, generating — at the outset of the refactoring — all constraints necessary to constrain these changes. As we are able to demonstrate, the computational overhead imposed by our framework, although threatening viability in theory, can be reduced to tractable sizes.