Trait EmptyIntoErr 

pub trait EmptyIntoErr<T, E> {
    // Required method
    fn empty_into_err<O>(self, op: O) -> Result<T, E>
       where O: FnOnce() -> E;
}

Import this trait to add the empty_into_err(op) method to Result<T, E>, where T implements IsEmpty.

IsEmpty is implemented for the standard collections, and more.

Required Methods

fn empty_into_err<O>(self, op: O) -> Result<T, E>

where O: FnOnce() -> E,

If the value is Result::Ok with an inner value that IsEmpty::is_empty, calls op and returns its return value in Result::Err. Otherwise the original value is returned.

Examples

These examples only show Result<Vec<T>, E>, but any Result<T, E> can be used where T implements IsEmpty.

Ok with an empty Vec becomes Err.

let ok: Result<Vec<&str>, &str> = Ok(vec![]);
let err = ok.empty_into_err(|| "was empty");
assert_eq!(Err("was empty"), err);

Ok with a non-empty Vec remains unchanged.

let ok = Ok(vec!["a", "b", "c"]);
let still_ok = ok.empty_into_err(|| "was empty");
assert_eq!(Ok(vec!["a", "b", "c"]), still_ok);

Err remains unchanged.

let err: Result<Vec<&str>, &str> = Err("failed");
let still_err = err.empty_into_err(|| "was empty");
assert_eq!(Err("failed"), still_err);

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<T, E> EmptyIntoErr<T, E> for Result<T, E>

where T: IsEmpty,

fn empty_into_err<O>(self, op: O) -> Result<T, E>

where O: FnOnce() -> E,

Implementors