Refactoring Using Type Constraints

Type constraints express subtype-relationships between the types of program expressions that are required for type-correctness, and were originally proposed as a convenient framework for solving type checking and type inference problems. In this paper, we show how type constraints can be used as the basis for practical refactoring tools. In our approach, a set of type constraints is derived from a type-correct program P. The main insight behind our work is the fact that P constitutes just one solution to this constraint system, and that alternative solutions may exist that correspond to refactored versions of P. We show how a number of refactorings for manipulating types and class hierarchies can be expressed naturally using type constraints. Several refactorings in the standard distribution of Eclipse are based on our results.

• Type: Conference
• Year: 2007
• Where: SAS
• Authors: Frank Tip
• Keywords: Constraints Express Subtype-relationships, Formal Methods, SAS 2007, Type Constraints, Type Inference Problems