Incremental type-checking for free: using scope graphs to derive incremental type-checkers

Fast analysis response times in IDEs are essential for a good editor experience. Incremental type-checking can provide that scalable fashion. However, existing techniques not reusable between languages. Moreover, mutual and dynamic dependencies preclude traditional approaches to incrementality. This makes finding automatic incremental challenging but important open question. In this paper, we present technique automatically derives type-checkers from type system specifications written the Statix meta-DSL. We use name resolution queries scope graphs (a generic model of binding embedded Statix) derive compilation units. A novel query confirmation algorithm finds which answer changed due an edit program. Only units with such require reanalysis. The effectiveness is improved by (1) splitting task into context-free context-sensitive part, (2) reusing mechanism resolve dependencies. yields any specification. Compared non-incremental parallel execution, achieve speedups up 147x on synthetic benchmarks, 21x real-world projects, initial overheads below 10%. suggests our framework efficient wide range languages supported Statix.