Intensional Refinement Datatypes: With Application to Scalable Verification of Pattern-Match Safety

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The pattern-match safety problem is to verify that a given functional program will never crash due to non-exhaustive patterns in its function definitions. We present a refinement type system that can be used to solve this problem. The system extends ML-style type systems with algebraic data types by a limited form of structural subtyping and environment-level intersection. We describe a fully automatic, sound and complete type inference procedure for this system which, under reasonable assumptions, is worst-case linear-time in the program size. Compositionality is essential to obtaining this complexity guarantee. A prototype implementation for Haskell is able to analyse a selection of packages from the Hackage database in a few hundred milliseconds.
Original languageEnglish
JournalProceedings of the ACM on Programming Languages
Publication statusAccepted/In press - 5 Nov 2020

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