True, I was not addressing the main point of what you said, and quibbling about your wording on a side point.
So before C++ assignment and copy operator overloading, you'd have a C struct, and assignment was a bitwise copy. If the original is destroyed after that, you're safe. If it's not, and the struct contains a pointer to allocated memory, you're going to have trouble unless you're very careful about who owns the memory.
But even then, you had situations where you wanted to truly make a (deep) copy. That took a call to a function that knew the structure, and which parts to deep copy. So the need to do that was still there.
So if we move to affine types or move semantics or whatever, the need for deep copy doesn't go away. If you don't have an overloaded assignment operator or copy operator, you're going to have a function of a different name that does the exact same operations. So the need for both operations doesn't go away. But the move/affine approach does make the double-free problem go away (as does the current C++ overloaded copy approach).
> language design is hard
Yeah. Somebody wants every possible action to be doable, and different people want different actions to be easy or the default. Nobody's going to be completely happy.
I would personally arguing that a deep copy necessitating an explicit function call is a good thing, though. It makes potentially expensive operations obvious, and improves your ability to reason about program behaviour.
So before C++ assignment and copy operator overloading, you'd have a C struct, and assignment was a bitwise copy. If the original is destroyed after that, you're safe. If it's not, and the struct contains a pointer to allocated memory, you're going to have trouble unless you're very careful about who owns the memory.
But even then, you had situations where you wanted to truly make a (deep) copy. That took a call to a function that knew the structure, and which parts to deep copy. So the need to do that was still there.
So if we move to affine types or move semantics or whatever, the need for deep copy doesn't go away. If you don't have an overloaded assignment operator or copy operator, you're going to have a function of a different name that does the exact same operations. So the need for both operations doesn't go away. But the move/affine approach does make the double-free problem go away (as does the current C++ overloaded copy approach).
> language design is hard
Yeah. Somebody wants every possible action to be doable, and different people want different actions to be easy or the default. Nobody's going to be completely happy.