asfail.rs

/// Helper trait to downcast a response error into a fail.
pub trait ResponseErrorAsFail {
    /// Returns the response error as fail.
    fn as_fail(&self) -> &Fail;
    /// Returns the response error as mut fail.
    fn as_mut_fail(&mut self) -> &mut Fail;
}

#[doc(hidden)]
impl<T: ResponseError> ResponseErrorAsFail for T {
    fn as_fail(&self) -> &Fail { self }
    fn as_mut_fail(&mut self) -> &mut Fail { self }
}

/// Error that can be converted to `HttpResponse`
pub trait ResponseError: Fail + ResponseErrorAsFail {
    /// Create response for error
    ///
    /// Internal server error is generated by default.
    fn error_response(&self) -> HttpResponse {
        HttpResponse::new(StatusCode::INTERNAL_SERVER_ERROR)
    }
}

impl ResponseError {
    pub fn downcast_ref<T: Fail>(&self) -> Option<&T> {
        Fail::downcast_ref(self.as_fail())
    }

    pub fn downcast_mut<T: Fail>(&mut self) -> Option<&mut T> {
        self.as_mut_fail().downcast_mut()
    }

    // THIS ONE FAILS
    pub fn root_cause(&self) -> &Fail {
        self.as_fail().root_cause()
    }
}

gistfile1.txt

   = note: candidate #1 is defined in an impl for the type `failure::Fail + 'static`
note: candidate #2 is defined in the trait `failure::Fail`
  --> /Users/mitsuhiko/.cargo/registry/src/github.com-1ecc6299db9ec823/failure-0.1.1/src/lib.rs:152:5
   |
152| /     fn root_cause(&self) -> &Fail where
153| |         Self: Sized,
154| |     {
155| |         find_root_cause(self)
156| |     }
   | |_____^
   = help: to disambiguate the method call, write `failure::Fail::root_cause(...)` instead