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
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158

//! The different types of `Any` for use in a map.
//!
//! This stuff is all based on `std::any`, but goes a little further, with `CloneAny` being a
//! cloneable `Any` and with the `Send` and `Sync` bounds possible on both `Any` and `CloneAny`.

use std::fmt;
use std::any::Any as StdAny;

#[doc(hidden)]
pub trait CloneToAny {
    /// Clone `self` into a new `Box<CloneAny>` object.
    fn clone_to_any(&self) -> Box<CloneAny>;

    /// Clone `self` into a new `Box<CloneAny + Send>` object.
    fn clone_to_any_send(&self) -> Box<CloneAny + Send> where Self: Send;

    /// Clone `self` into a new `Box<CloneAny + Sync>` object.
    fn clone_to_any_sync(&self) -> Box<CloneAny + Sync> where Self: Sync;

    /// Clone `self` into a new `Box<CloneAny + Send + Sync>` object.
    fn clone_to_any_send_sync(&self) -> Box<CloneAny + Send + Sync> where Self: Send + Sync;
}

impl<T: Any + Clone> CloneToAny for T {
    #[inline]
    fn clone_to_any(&self) -> Box<CloneAny> {
        Box::new(self.clone())
    }

    #[inline]
    fn clone_to_any_send(&self) -> Box<CloneAny + Send> where Self: Send {
        Box::new(self.clone())
    }

    #[inline]
    fn clone_to_any_sync(&self) -> Box<CloneAny + Sync> where Self: Sync {
        Box::new(self.clone())
    }

    #[inline]
    fn clone_to_any_send_sync(&self) -> Box<CloneAny + Send + Sync> where Self: Send + Sync {
        Box::new(self.clone())
    }
}

macro_rules! define {
    (CloneAny) => {
        /// A type to emulate dynamic typing.
        ///
        /// Every type with no non-`'static` references implements `Any`.
        define!(CloneAny remainder);
    };
    (Any) => {
        /// A type to emulate dynamic typing with cloning.
        ///
        /// Every type with no non-`'static` references that implements `Clone` implements `Any`.
        define!(Any remainder);
    };
    ($t:ident remainder) => {
        /// See the [`std::any` documentation](https://doc.rust-lang.org/std/any/index.html) for
        /// more details on `Any` in general.
        ///
        /// This trait is not `std::any::Any` but rather a type extending that for this library’s
        /// purposes so that it can be combined with marker traits like 
        /// <code><a class=trait title=core::marker::Send
        /// href=http://doc.rust-lang.org/std/marker/trait.Send.html>Send</a></code> and
        /// <code><a class=trait title=core::marker::Sync
        /// href=http://doc.rust-lang.org/std/marker/trait.Sync.html>Sync</a></code>.
        ///
        define!($t trait);
    };
    (CloneAny trait) => {
        /// See also [`Any`](trait.Any.html) for a version without the `Clone` requirement.
        pub trait CloneAny: Any + CloneToAny { }
        impl<T: StdAny + Clone> CloneAny for T { }
    };
    (Any trait) => {
        /// See also [`CloneAny`](trait.CloneAny.html) for a cloneable version of this trait.
        pub trait Any: StdAny { }
        impl<T: StdAny> Any for T { }
    };
}

macro_rules! impl_clone {
    ($t:ty, $method:ident) => {
        impl Clone for Box<$t> {
            #[inline]
            fn clone(&self) -> Box<$t> {
                (**self).$method()
            }
        }
    }
}

#[allow(missing_docs)]  // Bogus warning (it’s not public outside the crate), ☹
pub trait UncheckedAnyExt: Any {
    unsafe fn downcast_ref_unchecked<T: Any>(&self) -> &T;
    unsafe fn downcast_mut_unchecked<T: Any>(&mut self) -> &mut T;
    unsafe fn downcast_unchecked<T: Any>(self: Box<Self>) -> Box<T>;
}

#[doc(hidden)]
/// A trait for the conversion of an object into a boxed trait object.
pub trait IntoBox<A: ?Sized + UncheckedAnyExt>: Any {
    /// Convert self into the appropriate boxed form.
    fn into_box(self) -> Box<A>;
}

macro_rules! implement {
    ($base:ident, $(+ $bounds:ident)*) => {
        impl fmt::Debug for $base $(+ $bounds)* {
            #[inline]
            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                f.pad(stringify!($base $(+ $bounds)*))
            }
        }

        impl UncheckedAnyExt for $base $(+ $bounds)* {
            #[inline]
            unsafe fn downcast_ref_unchecked<T: 'static>(&self) -> &T {
                &*(self as *const Self as *const T)
            }

            #[inline]
            unsafe fn downcast_mut_unchecked<T: 'static>(&mut self) -> &mut T {
                &mut *(self as *mut Self as *mut T)
            }

            #[inline]
            unsafe fn downcast_unchecked<T: 'static>(self: Box<Self>) -> Box<T> {
                Box::from_raw(Box::into_raw(self) as *mut T)
            }
        }

        impl<T: $base $(+ $bounds)*> IntoBox<$base $(+ $bounds)*> for T {
            #[inline]
            fn into_box(self) -> Box<$base $(+ $bounds)*> {
                Box::new(self)
            }
        }
    }
}

define!(Any);
implement!(Any,);
implement!(Any, + Send);
implement!(Any, + Sync);
implement!(Any, + Send + Sync);
implement!(CloneAny,);
implement!(CloneAny, + Send);
implement!(CloneAny, + Sync);
implement!(CloneAny, + Send + Sync);

define!(CloneAny);
impl_clone!(CloneAny, clone_to_any);
impl_clone!((CloneAny + Send), clone_to_any_send);
impl_clone!((CloneAny + Sync), clone_to_any_sync);
impl_clone!((CloneAny + Send + Sync), clone_to_any_send_sync);