That's one of my biggest issues with C++ today. Objects that can be moved must support a "my value was moved out" state. So every access to the object usually starts with "if (have-a-value())". It also means that the destructor is called for an object that won't be used anymore.

Regarding #2, take Resource Acquisition Is Initialization (RAII) as an example - in RAII, the existence of an object implies the existence of a resource. Now, if you want to be able to move, the object becomes "either the resource exists or it was moved out". As someone else noted in the comments, this affects not only the destructor. Methods cannot assume the existence of the resource, they have to check it first. Kind of like optional.

The problem with the current move semantics is that, compared to e.g. Rust: 1) the compiler generates unnecessary code and 2) instead of just implementing class T you must implement a kind of optional.

Which means, that after all those years of using smart pointers I find myself ditching them in favor of plain pointers like we did in the 90's.

For example, function arguments can be "in", "out", "inout", "ref", "scope", "return ref" - and combinations.

Another example is conditional compilation. Great when used sparely, but can otherwise make it very difficult to understand how the code flows.

In the end, reading the source code of the standard library convinced me against it.

(The source code for the C++ standard library is much worse, of course).

In most implementations of the standard library, safety checks can be enabled with a simple #define. In some, it's the default behavior in DEBUG mode. I wonder what this library improves on that and why these bugs have not been discovered before.