Function extern_spec_T_Option_T_unwrap_or_else 

pub fn extern_spec_T_Option_T_unwrap_or_else<T, F: FnOnce() -> T>(
    self_: Option<T>,
    f: F,
) -> T

extern spec for Option<T>::unwrap_or_else

This is not a real function: its only use is for documentation.

requires

self == None ==> f.precondition(())

ensures

match self {
    None => f.postcondition_once((), result),
    Some(t) => resolve(f) && result == t
}