polyhorn_core/
key.rs

1use std::cmp::PartialEq;
2use std::fmt::Debug;
3use std::hash::{Hash, Hasher};
4use std::rc::Rc;
5
6/// Key is a dynamically typed wrapper around any type that implements `Any + Eq
7/// + Hash` (note that `Any` implies `'static`). Key acts as a transparent
8/// wrapper for these traits, where `Eq` and `PartialEq` in particular perform
9/// dynamic type checks before determining value equality.
10#[derive(Clone, Debug)]
11pub struct Key(Rc<dyn machinery::Keyable>);
12
13impl Key {
14    /// This function returns a new key with the given value. The prescribed
15    /// trait bound on `machinery::Keyable` refers to a hidden trait that is
16    /// automatically implemented for types that implement `Any + Eq + Hash`.
17    /// This trait is hidden because it should not be implemented manually.
18    pub fn new<T>(value: T) -> Key
19    where
20        T: machinery::Keyable + 'static,
21    {
22        Key(Rc::new(value))
23    }
24}
25
26impl<T> From<Rc<T>> for Key
27where
28    T: machinery::Keyable + 'static,
29{
30    fn from(value: Rc<T>) -> Self {
31        Key(value)
32    }
33}
34
35impl PartialEq for Key {
36    fn eq(&self, other: &Key) -> bool {
37        self.0.eq(other.0.as_any())
38    }
39}
40
41impl Eq for Key {}
42
43impl Hash for Key {
44    fn hash<H>(&self, state: &mut H)
45    where
46        H: Hasher,
47    {
48        self.0.hash(state)
49    }
50}
51
52mod machinery {
53    use std::any::Any;
54    use std::cmp::PartialEq;
55    use std::fmt::Debug;
56    use std::hash::{Hash, Hasher};
57
58    pub trait Keyable: Any + Debug {
59        fn eq(&self, other: &dyn Any) -> bool;
60        fn as_any(&self) -> &dyn Any;
61        fn hash(&self, state: &mut dyn Hasher);
62    }
63
64    impl<T> Keyable for T
65    where
66        T: Debug + Eq + Hash + 'static,
67    {
68        fn eq(&self, other: &dyn Any) -> bool {
69            match other.downcast_ref::<Self>() {
70                Some(other) => PartialEq::eq(self, other),
71                _ => false,
72            }
73        }
74
75        fn as_any(&self) -> &dyn Any {
76            self
77        }
78
79        fn hash(&self, mut state: &mut dyn Hasher) {
80            T::hash(self, &mut state)
81        }
82    }
83}
84
85#[cfg(test)]
86mod tests {
87    use super::Key;
88
89    #[test]
90    fn test_key() {
91        assert_eq!(Key::new((1, "Hello")), Key::new((1, "Hello")));
92        assert_ne!(Key::new((1, "Hello")), Key::new((2, "Hello")));
93    }
94}
polyhorn_core/key.rs

polyhorn_core/
key.rs
