A type system for recursive value definitions [article]

Alban Reynaud, Gabriel Scherer, Jeremy Yallop
2020 arXiv   pre-print
In call-by-value languages, some mutually-recursive value definitions can be safely evaluated to build recursive functions or cyclic data structures, but some definitions (let rec x = x + 1) contain vicious circles and their evaluation fails at runtime. We propose a new static analysis to check the absence of such runtime failures. We present a set of declarative inference rules, prove its soundness with respect to the reference source-level semantics of Nordlander, Carlsson, and Gill (2008),
more » ... d show that it can be (right-to-left) directed into an algorithmic check in a surprisingly simple way. Our implementation of this new check replaced the existing check used by the OCaml programming language, a fragile syntactic/grammatical criterion which let several subtle bugs slip through as the language kept evolving. We document some issues that arise when advanced features of a real-world functional language (exceptions in first-class modules, GADTs, etc.) interact with safety checking for recursive definitions.
arXiv:1811.08134v3 fatcat:qyaz3onta5hwjd5lyg5hje76nq