LONDON/TOKYO—Shares from Asia to Europe gained on Wednesday on rising optimism about the global economy and corporate earnings, while government bond yields rose and the yen fell to its lowest in four years against the dollar. The regional Euro STOXX 600 traded up 0.1 percent after opening in negative territory, amid a somewhat mixed picture for earnings even as investors were largely upbeat about prospects. German stocks also turned positive, adding 0.3 percent. In the Netherlands, chip-making machine maker ASML Holdings, a key supplier to computer chip makers, fell 3 percent despite posting slightly better-than-expected quarterly results. Swiss food giant Nestle gained 3 percent after it raised its sales outlook. Earnings reports will be in full swings in many countries over coming weeks. Tesla is among companies that will release results later on Wednesday. “Some volatility should be expected in a time when you have the earnings season, you have …