Getting into the Flow: Towards Better Type Error Messages for Constraint-Based Type Inference
Creating good type error messages for constraint-based type inference systems is difficult. Typical type error messages reflect implementation details of the underlying constraint-solving algorithms rather than the specific factors leading to type mismatches. We propose using subtyping constraints that capture data flow to classify and explain type errors. Our algorithm explains type errors as faulty data flows, which programmers are already used to reasoning about, and illustrates these data flows as sequences of relevant program locations. We show that our ideas and algorithm are not limited to languages with subtyping, as they can be readily integrated with Hindley-Milner type inference. In addition to these core contributions, we present the results of a user study to evaluate the quality of our messages compared to other implementations. While the quantitative evaluation does not show that flow-based messages improve the localization or understanding of the causes of type errors, the qualitative evaluation suggests a real need and demand for flow-based messages.
Thu 26 OctDisplayed time zone: Lisbon change
14:00 - 15:30 | |||
14:00 18mTalk | Greedy Implicit Bounded Quantification OOPSLA Chen Cui University of Hong Kong, Shengyi Jiang University of Hong Kong, Bruno C. d. S. Oliveira University of Hong Kong DOI | ||
14:18 18mTalk | Structural Subtyping as Parametric Polymorphism OOPSLA Wenhao Tang University of Edinburgh, Daniel Hillerström Huawei Zurich Research Center, James McKinna Heriot-Watt University, Michel Steuwer TU Berlin; University of Edinburgh, Ornela Dardha University of Glasgow, Rongxiao Fu University of Edinburgh, Sam Lindley University of Edinburgh DOI Pre-print | ||
14:36 18mTalk | Simple Reference Immutability for System F<: OOPSLA DOI | ||
14:54 18mTalk | Mutually Iso-Recursive Subtyping OOPSLA Andreas Rossberg Independent DOI | ||
15:12 18mTalk | Getting into the Flow: Towards Better Type Error Messages for Constraint-Based Type Inference OOPSLA Ishan Bhanuka Hong Kong University of Science and Technology, Lionel Parreaux Hong Kong University of Science and Technology, David Binder University of Tübingen, Jonathan Immanuel Brachthäuser University of Tübingen DOI Pre-print |