The guidelines below were approved by rust issue #7087.
[FIXME] Should we provide standard traits for conversions? Doing so nicely will require trait reform to land.
Conversions should be provided as methods, with names prefixed as follows:
| Prefix | Cost | Consumes convertee |
|---|---|---|
as_ |
Free | No |
to_ |
Expensive | No |
into_ |
Variable | Yes |
For example:
as_bytes() gives a &[u8] view into a &str, which is a no-op.to_owned() copies a &str to a new String.into_bytes() consumes a String and yields the underlying
Vec<u8>, which is a no-op.Conversions prefixed as_ and into_ typically decrease abstraction, either
exposing a view into the underlying representation (as) or deconstructing data
into its underlying representation (into). Conversions prefixed to_, on the
other hand, typically stay at the same level of abstraction but do some work to
change one representation into another.
[FIXME] The distinctions between conversion methods does not work so well for
from_conversion constructors. Is that a problem?