before this change, the build fails, because AlloAllocator is not defined when the standard library provides std::generator, and the tree is built with C++23.
in this change, we replace AlloAllocator with Allocator. and the tree builds fine.
also, we include <generator> only if __cpp_lib_generator is defined. as the existence of the header does not imply that we are building with C++23.
before this change, the build fails, because
AlloAllocatoris not defined when the standard library providesstd::generator, and the tree is built with C++23.in this change, we replace
AlloAllocatorwithAllocator. and the tree builds fine.also, we include
<generator>only if__cpp_lib_generatoris defined. as the existence of the header does not imply that we are building with C++23.