2de2bb980e
shared_ptr was used in 2d1984c20c75e03ec79eeb3806b12efa1679b977 due to a misunderstanding of how the language generates move constructors and move assignment operators. If a destructor is user-provided, then the compiler won't generate the move constructor and move assignment operators by default--they must be explicitly opted into. The reason for the compilation errors is due to the fact that the language will fall back to attempting to use the copy constructor/copy assignment operators if the respective move constructor or move assignment operator is unavailable. Given that we explicitly opt into them now, the the move constructor and move assignment operators will be generated as expected.