I left programming in PHP when isset() was a lifestyle, array() had just become [] , and types lived in docblocks where the runtime couldn't see them. The language you're returning to grew toward the exact things that pulled me to Ruby and Go: real signatures, immutability you can enforce, pattern matching, values that can't lie about what they are. Almost everything below follows one theme — declare your intent in the code, and let the engine enforce it — which means a huge amount of the...