Setting a default for Duration type in proc macros

[dnaka91]

When deriving a uniffi::Record I have a few fields of type Duration and was hoping to give them a default value. However it seems at the moment the proc macros don't accept literals for it, despite durations being somewhat primitive types from the Built-in types table.

It would be great if the proc macros can be extended to accept expressions for Duration.

I only use Uniffi for Kotlin code, where there should be equivalents to construct the default value in a data class but I'm not sure if this is possible in other languages as well.

For Duration I'd imagine accepting the const constructors:

• Duration::from_secs
• Duration::from_millis
• Duration::from_micros

And eventually:

• Duration::from_secs_f32
• Duration::from_secs_f64

For example:

#[uniffi::Record]
struct Config {
    #[uniffi(default = Duration::from_secs(5))]
    max_wait: Duration,
}