When in doubt, prefer to_/as_/into_ to from_, because they are
more ergonomic to use (and can be chained with other methods).
For many conversions between two types, one of the types is clearly more
"specific": it provides some additional invariant or interpretation that is not
present in the other type. For example, str is more specific than &[u8],
since it is a utf-8 encoded sequence of bytes.
Conversions should live with the more specific of the involved types. Thus,
str provides both the as_bytes method and the from_utf8 constructor for
converting to and from &[u8] values. Besides being intuitive, this convention
avoids polluting concrete types like &[u8] with endless conversion methods.
If a function's name implies that it is a conversion (prefix from_, as_,
to_ or into_), but the function loses information, add a suffix _lossy or
otherwise indicate the lossyness. Consider avoiding the conversion name prefix.