If `Allocator::select_on_container_copy_construction` exists and has the right signature, the allocator will be constructed from its result.
If若 `Allocator::select_on_container_copy_construction` exists and has the right signature, the allocator will be constructed from its result.++_++on++_++container++_++copy++_++construction` 存在且签名正确，则将根据其结果来构造分配器。
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If若 `Allocator::select_on_container_copy_construction` exists and has the right signature, the allocator will be constructed from its result.++_++on++_++container++_++copy++_++construction` 存在且签名正确，则将根据其结果来构造分配器。