Nested Refinements: A Logic for Duck Typing

作者：Chugh Ravi^*; Rondon Patrick M; Jhala Ranjit

来源：ACM Sigplan Notices, 2012, 47(1): 231-243.

DOI：10.1145/2103621.2103686

• Languages
• Verification
• Refinement Types
• Dynamic Languages

Programs written in dynamic languages make heavy use of features - run-time type tests, value-indexed dictionaries, polymorphism, and higher-order functions-that are beyond the reach of type systems that employ either purely syntactic or purely semantic reasoning. We present a core calculus, System D, that merges these two modes of reasoning into a single powerful mechanism of nested refinement types wherein the typing relation is itself a predicate in the refinement logic. System D coordinates SMT-based logical implication and syntactic subtyping to automatically typecheck sophisticated dynamic language programs. By coupling nested refinements with McCarthy's theory of finite maps, System D can precisely reason about the interaction of higher-order functions, polymorphism, and dictionaries. The addition of type predicates to the refinement logic creates a circularity that leads to unique technical challenges in the metatheory, which we solve with a novel stratification approach that we use to prove the soundness of System D.

• 出版日期2012-1