20 Memory management library [mem]

20.3 Smart pointers [smartptr]

20.3.1 Unique-ownership pointers [unique.ptr]

20.3.1.4 unique_ptr for array objects with a runtime length [unique.ptr.runtime]

20.3.1.4.4 Observers [unique.ptr.runtime.observers]

constexpr T& operator[](size_t i) const;
Preconditions: i < the number of elements in the array to which the stored pointer points.
Returns: get()[i].