For the last few years, we at Morgan Stanley have been developing hobbes -- a programming language, JIT compiler, and database system. It has developed into a critical piece of infrastructure in our low-latency, high-volume trading applications, and we have decided to release the source code to the public on github (currently can be built for recent Linux and macOS platforms):
The database system is a lightweight (self-contained, header-only) library used by applications to efficiently log structured (binary) data over shared memory to minimize application latency and reflect application type structure as accurately as possible in log files. We use this to record a very detailed image of application state over time, which we analyze/query out of band.
The JIT compiler can be used embedded in another application (e.g. to "hot patch" an application with very efficient, precisely typed intercepts) or as a standalone interactive interpreter (e.g.: to monitor and query application log data).
The programming language is a variant of Haskell (HM type inference, algebraic data types, qualified types / type classes) with some adjustments to help reduce boilerplate and derive very efficient machine code. For example, we use "structural" record, variant, and (iso-)recursive types to represent data as it's naturally represented in applications and can be deconstructed generically at compile time (e.g. a record can be printed if its first field can be printed and its rest can be printed, a variant can be printed if its first case can be printed and its rest cases can be printed, a recursive type can be printed if its one-step unrolling can be printed, etc).
We are actively using this on major projects, we will continue to develop this github project as we need new features, and we are interested in engaging others outside of the firm for their thoughts, feedback, and hopefully pull requests. :)