Struct describe_err::Described

pub struct Described<E: Error + 'static> { /* fields omitted */ }

An error wrapper with description.

This struct can hold every error, with the only restriction that this error must be 'static to support downcasting through source.

When converting this wrapper to string with Display, it will render colon-separated pair of description and original error:

use describe_err::{Described, describing};
fn fmt<E: std::error::Error + 'static>(err: &Described<E>) -> String {
    format!("{}: {}", err.description(), err.original())
}
 
fn main() {
    // Let's create a simple error with auto-generated description...
    let res: Result<u32, _> = describing!("Not a number".parse());
    // ...then unwrap it...
    let err = res.unwrap_err();
    // and see that the formatting is indeed the same:
    assert_eq!(fmt(&err), format!("{}", err));
}

Implementations

impl<E: Error + 'static> Described<E>

pub fn description(&self) -> &str

Directly retrieves an error description.

pub fn original(&self) -> &E

Directly retrieves an original error.

This method is different from source, since it is generic and is known to return exactly the wrapped type, not a boxed trait object. This way you won't need any downcasting.

Trait Implementations

impl<E: Debug + Error + 'static> Debug for Described<E>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<E: Error + 'static> Display for Described<E>

fn fmt(&self, __formatter: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<E: Error + 'static> Error for Described<E>

fn source(&self) -> Option<&(dyn Error + 'static)>

The lower-level source of this error, if any.

fn backtrace(&self) -> Option<&Backtrace>

🔬 This is a nightly-only experimental API. (backtrace)

Returns a stack backtrace, if available, of where this error occurred.

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

if let Err(e) = "xc".parse::<u32>() { // Print e itself, no need for description(). eprintln!("Error: {}", e); }

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting