Morrow

Morrow is a programming language I’m building for command-line tools and applications. The goal is code that reads about as easily as Python, with a type checker and pattern matching catching mistakes before the program runs.

Code is indentation-based, types are inferred, and bindings are immutable. Absence and failure are values: a function returns an Option or a Result, and the compiler insists that a match covers every case. Forget the Err branch in the picture and morrow check refuses with “match must be exhaustive”, naming what is missing. Traits, compile-time constants, typed JSON and deferred cleanup are there too.

morrow run compiles and executes in one step, and morrow build leaves a native executable that runs without the compiler. The compiler, runtime, language server and tools are written in Rust, with Cranelift generating the machine code. A formatter, a REPL, a test runner and a documentation generator ship with it.

The more ambitious direction is full-stack. The same typed Morrow code can run as supervised actors on a native server and as a WebAssembly client in the browser, with updates over WebSockets and offline reading. A collaborative checklist is the working demo of that, and the repository documents a three-node cluster setup with its delivery guarantees.

The project started in January 2026 under the name Fern. In September its implementation moved to a Rust workspace with Cranelift, and the language got its new name. It is an early preview: native builds are verified on macOS and Linux on ARM64, and the syntax and APIs are still changing. There are no release packages yet, so trying it means building from source.