Trait wasmi::HostError

pub trait HostError: 'static + Display + Debug + Send + Sync { }

Trait that allows the host to return custom error.

It should be useful for representing custom traps, troubles at instantiation time or other host specific conditions.

Examples

use std::fmt;
use wasmi::{Error, HostError};

#[derive(Debug)]
struct MyError {
    code: u32,
}

impl fmt::Display for MyError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "MyError, code={}", self.code)
    }
}

impl HostError for MyError { }

fn failable_fn() -> Result<(), Error> {
    let my_error = MyError { code: 1312 };
    Err(Error::Host(Box::new(my_error)))
}

match failable_fn() {
    Err(Error::Host(host_error)) => {
        let my_error = host_error.downcast_ref::<MyError>().unwrap();
        assert_eq!(my_error.code, 1312);
    }
    _ => panic!(),
}

Implementations

impl dyn HostError

pub fn downcast_ref<T: HostError>(&self) -> Option<&T>

Attempt to downcast this HostError to a concrete type by reference.

pub fn downcast_mut<T: HostError>(&mut self) -> Option<&mut T>

Attempt to downcast this HostError to a concrete type by mutable reference.

Implementors