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Niels Lohmann
0157e9c035
Follow-up to the strong exception guarantee of the non-const operator[](json_pointer): - get_unchecked_create assumed that emplace() always inserts the key that the walk did not find. For object types whose lookup and emplace() disagree (e.g. a copied fifo_map), nothing was inserted, the rollback erased the existing member, and the walk continued with a value of the wrong type (assertion, type_error.305, or a crash). It now checks the result of emplace(), arms the rollback only if a key was inserted, and otherwise continues the walk with the member found, as basic_json's operator[] does: such pointers throw out_of_range.404 and leave the value unchanged, as before the strong guarantee. - The rollback erased the inserted key by key, which converts string_t to object_t::key_type and may allocate inside a noexcept function (std::terminate on bad_alloc with custom key types). It now erases by the iterator emplace() returned, and shrinks a grown array with erase() at the end instead of resize(). The documentation states the remaining requirement for custom template parameters. - Creating values no longer calls string_t::begin(), so the non-const operator[](json_pointer) compiles with string types that lack it (as the alternative string type of the tests). - Correct the @throw lists of get_unchecked and get_unchecked_create. Signed-off-by: Niels Lohmann <mail@nlohmann.me>