C++ primer 5th ed. assigning to an std::array from a brace-list [duplicate]

Hello I am on page 1286 of C++ primer. I am at the solutions part. here is an example in the book:

 std::array<int, 10> a1 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
 std::array<int, 10> a2 = {0}; // elements all have value 0
 a1 = a2; // replace elements  in a1
 a2 = {0}; // error: cannot assign to an array from a braced list

• However we can assign to an std::array from a braced list so a2 is assigned 0 to the first element and all the remaining elements are value-init to 0 too.

• So is this a mistake in the book or just because of some change in the new Standard? Thank you!