This is going to sound weird, but I would like to see a garbage-collected Rust. Take away the borrow checker, and you still have a modern language with UTF-8 support out-of-the-box, algebraic data types, pattern matching, a focus on performance, and great tooling (cargo + rustup = <3).
OCaml almost fits the bill (Rust is inspired by OCaml after all), but the tooling around it is lacking to put it mildly.
F# sounds like it fits the bill. ADT, pattern matching, performant, great tooling (multiple amazing IDEs, a REPL, etc.), and a huge ecosystem of software packages to use with it (all of .NET). It's my favorite general purpose programming language (can be used for frontend programming, server, mobile apps, etc.).
I wanted to get into f# but had a hard time with tooling, cross platform. For example, I'd see a great library and the instructions assume VS while I'm on Linux. There are a variety of build tools and package managers.
As Python dev since 10 years I can't point fingers -- Python is probably worse though I've memorized the idiosyncrasies -- but I couldn't justify my way up the tooling learning curve in addition to the language curve.
Do you remember the library? The landscape has changed dramatically in the past ~6 months with .NET Core 2.0 support. For example, I can use Fable[0] and Giraffe[1] with the .NET CLI[2] to build full-stack F# apps on my machine which runs .NET Core. The big remaining blocker for most people to just jump wholesale onto .NET Core and forget anything Windows-based is the lak of Type Provider support, but we're quite close to finishing that.
[0] http://fable.io