Impl From for SslVersion

[kornelski]

You could implement try_from as an inherent method (not a trait), and change From impl to use ExtensionType::try_from(x).unwrap() to make it sound, or if panicking could be too disruptive, then try_from(x).unwrap_or(some_default).

[rushilmehra]

My rationale is that if we went with the panic route, I consider that a breaking change, so at that point we should just switch to TryFrom directly. The issue with providing a default is it could lead to unexpected behavior. If we take SslVersion as an example, and you were able to construct one that is "invalid", the worst that would happen is any API like set_min_proto_version would just fail because the underlying c++ code sanity checks the incoming u16. If we provide a default, then application code that accidentally creates an SslVersion with a bogus value will silently configure some default version.