I want to make the following example compile, but it returns an error: "error[E0119]: conflicting implementations of trait From<A<_>> for type A<_>"
I know that "auto trait" combined "negative impl" may have worked before, however, it fails due to the forbid conditional issue in the recent night version.
Without specialization being stabilized (which won't happen any time soon), I don't think there's a way to write your generic trait implementation like that.