Implementing a resumable exception system in Go

CRANK

GitHub’s Semantic team recently wrote: An example of [dynamic control flow] is the concept of resumable exceptions. During Semantic’s interpretation passes, invalid code (unbound variables, type errors, infinite recursion) is recognized and handled based on the pass’s calling context. Because Semantic is, at its heart, an interpreter, this feature is essential for rapid development: we specify, when constructing interpretation and analysis passes, how GHC should handle errors while executing untrusted and possibly-invalid code, simply by specializing our call sites.