Error::from_context(context, self)

            let backtrace = backtrace_if_absent!(self);
            Error::from_context(context, self, backtrace)

    pub(crate) fn from_context<C, E>(context: C, error: E) -> Self

    pub(crate) fn from_context<C, E>(context: C, error: E, backtrace: Option<Backtrace>) -> Self

        Error::new(ContextError { context, error })

        let error: ContextError<C, E> = ContextError { context, error };
        let vtable = &ErrorVTable {
            object_drop: object_drop::<ContextError<C, E>>,
            object_drop_front: object_drop_front::<ContextError<C, E>>,
            object_ref: object_ref::<ContextError<C, E>>,
            object_mut: object_mut::<ContextError<C, E>>,
            object_boxed: object_boxed::<ContextError<C, E>>,
            object_is: object_is::<ContextError<C, E>>,
        };
        // Safety: passing vtable that operates on the right type.
        unsafe { Error::construct(error, vtable, backtrace) }