# 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.