The ins and outs of gradual type inference

Gradual typing lets programmers evolve their dynamically typed programs by gradually adding explicit type annotations, which confer benefits like improved performance and fewer run-time failures. However, we argue that such evolution often requires a giant leap, and that type inference can offer a crucial missing step. If omitted type annotations are interpreted as unknown types, rather than the dynamic type, then static types can often be inferred, thereby removing unnecessary assumptions of the dynamic type. The remaining assumptions of the dynamic type may then be removed by either reasoning outside the static type system, or restructuring the code. We present a type inference algorithm that can improve the performance of existing gradually typed programs without introducing any new run-time failures. To account for dynamic typing, types that flow in to an unknown type are treated in a fundamentally different manner than types that flow out. Furthermore, in the interests of back...

• Type: Journal
• Year: 2012
• Where: POPL
• Authors: Aseem Rastogi, Avik Chaudhuri, Basil Hosmer
• Keywords: POPL 2012, Programming Languages, Programming Languages Processors, Static Type System, Type Inference Algorithm