Oh hey I recently saw a comment which discussed this exact issue: https://news.ycombinator.com/item?id=47752915
99% of the time this situation is okay, because Cargo allows you to have both 0.1 and 0.2 in the same project as dependencies. It's just packages that call out to external dependencies, like libc, where it enforces the single version rule.
alt Hacker News
99% of the time this situation is okay, because Cargo allows you to have both 0.1 and 0.2 in the same project as dependencies. It's just packages that call out to external dependencies, like libc, where it enforces the single version rule.