Conversions between types

Associate conversions with the most specific type involved. [FIXME: needs RFC]

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.

Explicitly mark lossy conversions, or do not label them as conversions. [FIXME: needs RFC]

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.