1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49

//! impl bool {}

use crate::marker::Destruct;

#[cfg_attr(bootstrap, lang = "bool")]
impl bool {
    /// Returns `Some(t)` if the `bool` is [`true`](../std/keyword.true.html),
    /// or `None` otherwise.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(bool_to_option)]
    ///
    /// assert_eq!(false.then_some(0), None);
    /// assert_eq!(true.then_some(0), Some(0));
    /// ```
    #[unstable(feature = "bool_to_option", issue = "80967")]
    #[rustc_const_unstable(feature = "const_bool_to_option", issue = "91917")]
    #[inline]
    #[cfg_attr(not(bootstrap), allow(drop_bounds))] // FIXME remove `~const Drop` and this attr when bumping
    pub const fn then_some<T>(self, t: T) -> Option<T>
    where
        T: ~const Drop + ~const Destruct,
    {
        if self { Some(t) } else { None }
    }

    /// Returns `Some(f())` if the `bool` is [`true`](../std/keyword.true.html),
    /// or `None` otherwise.
    ///
    /// # Examples
    ///
    /// ```
    /// assert_eq!(false.then(|| 0), None);
    /// assert_eq!(true.then(|| 0), Some(0));
    /// ```
    #[stable(feature = "lazy_bool_to_option", since = "1.50.0")]
    #[rustc_const_unstable(feature = "const_bool_to_option", issue = "91917")]
    #[inline]
    #[cfg_attr(not(bootstrap), allow(drop_bounds))] // FIXME remove `~const Drop` and this attr when bumping
    pub const fn then<T, F>(self, f: F) -> Option<T>
    where
        F: ~const FnOnce() -> T,
        F: ~const Drop + ~const Destruct,
    {
        if self { Some(f()) } else { None }
    }
}