[etbebl]

The author dismisses C++ out of hand, but I really think it does a pretty good job of making this a non-issue. Want a structured value type? Sure, that's a struct with public fields by default, passed by value with automatic copy constructor and assignment functions. Want a mutable type that's encapsulated and needs to do something special to be cloned? Sure, that's a class passed by unique_pointer or reference, with non-default (or deleted) copy constructor and assignment functions and private fields by default.

Every language I've used since then feels like it makes this issue needlessly complicated and implicit.

[deterministic]

C++ developer here (30+ years). C++ is really missing support for sum types. The Haskell JSON example shows how useful it would be to have native support for it. Yes you can build your own but it’s pages of boiler plate code.