[masklinn]

> And old languages had it bolted on (C# 8, Java 8, C++ 17).

C#: actually true, you can switch over to non-nullable reference types

Java 8: meeeh, it provides an Optional but all references are still nullable, including references to Optional. There are also @Nullable and @NotNull annotations but they're also meh, plus some checkers handle them oddly[0]

C++17: you can deref' an std::optional, it's completely legal, and it's an UB if the optional is empty. Despite its name, std::optional is not a type-safety feature, its goal is not to provide for "nullable references" (that's a pointer), it's to provide a stack-allocated smart pointer (rather than have to allocate with unique_ptr for instance).

[0] https://checkerframework.org/manual/#findbugs-nullable