Rust, ReasonML
- Immutability by default. Check
- Discriminated unions with exhaustive check. Check
- No nulls by default. Check
- No exceptions in the business logic. Check
- Strict dependency order. Rust doesn't have this
- Warnings on unused expression results. Check
- Typed primitives. The level of ergonomics this is implemented with in F# I'll say Rust doesn't have this
- Explicit conversions. Check
- Functional approach to concurrency. I think Rust's compile time safety against data races gives this a check. I've used channels for concurrent server processes, it's nice. Check
- Explicit dependency injection. I've never understood what this means
7/10
The article seems to mean what's described in this other article as "dependency parameterization" where the dependency is explicitly passed to the function (and every function it calls that also needs that same dependency). This is as opposed to, in OO languages, setting the dependency (typically) during construction (however the object is constructed). Or it's otherwise set in some larger scope than the functions which make use of it (global, module, object instance, whatever is appropriate to the language and task).
IMO the first and foremost principle of Functional Programming languages is that they are optimised around building programs in terms of function composition. And anyone who had to work with borrow checker and closures for 5sec knows, that this is not the case for Rust.