rust-script 0.36.0

//! This module contains an implementation of Defer.
use log::error;
use std::error::Error;
use std::marker::PhantomData;

/// Used to defer a closure until the value is dropped.
///
/// The closure *must* return a `Result<(), _>`, as a reminder to *not* panic; doing so will abort your whole program if it happens during another panic.  If the closure returns an `Err`, then it is logged as an `error`.
///
/// A `Defer` can also be "disarmed", preventing the closure from running at all.
#[must_use]
pub struct Defer<'a, F, E>(Option<F>, PhantomData<&'a F>)
where
    F: 'a + FnOnce() -> Result<(), E>,
    E: Error;

impl<'a, F, E> Defer<'a, F, E>
where
    F: 'a + FnOnce() -> Result<(), E>,
    E: Error,
{
    /// Create a new `Defer` with the given closure.
    pub fn new(f: F) -> Defer<'a, F, E> {
        Defer(Some(f), PhantomData)
    }

    /// Consume this `Defer` *without* invoking the closure.
    pub fn disarm(mut self) {
        self.0 = None;
        drop(self);
    }
}

impl<'a, F, E> ::std::ops::Drop for Defer<'a, F, E>
where
    F: 'a + FnOnce() -> Result<(), E>,
    E: Error,
{
    fn drop(&mut self) {
        if let Some(f) = self.0.take() {
            if let Err(err) = f() {
                error!("deferred function failed: {}", err);
            }
        }
    }
}