rusteval/
specialization.rs

1//! Implementation details.
2#![allow(missing_docs)]
3
4use core::any::type_name;
5use core::fmt::Debug;
6
7use crate::{Interactive, InteractiveError, Methods, Result};
8
9/// Use specialization to retrieve a trait object reference
10/// from types that implement the trait or an error if it doesn't.
11macro_rules! duck_type {
12    ($vis:vis $AsTrait:ident ($method:ident) : $Trait:path | $Error:ident) => {
13        $vis trait $AsTrait {
14            fn $method(&self) -> Result<'_, &dyn $Trait>;
15        }
16
17        impl<T> $AsTrait for T {
18            default fn $method(&self) -> Result<'_, &dyn $Trait> {
19                Err(InteractiveError::$Error {
20                    type_name: type_name::<T>(),
21                })
22            }
23        }
24
25        impl<T> $AsTrait for T
26        where
27            T: $Trait,
28        {
29            fn $method(&self) -> Result<'_, &dyn $Trait> {
30                Ok(self)
31            }
32        }
33    };
34}
35
36/// Use specialization to retrieve a mutable trait object reference
37/// from types that implement the trait or an error if it doesn't.
38macro_rules! duck_type_mut {
39    ($vis:vis $AsTrait:ident ($method:ident) : $Trait:path | $Error:ident) => {
40        $vis trait $AsTrait {
41            fn $method(&mut self) -> Result<'_, &mut dyn $Trait>;
42        }
43
44        impl<T> $AsTrait for T {
45            default fn $method(&mut self) -> Result<'_, &mut dyn $Trait> {
46                Err(InteractiveError::$Error {
47                    type_name: type_name::<T>(),
48                })
49            }
50        }
51
52        impl<T> $AsTrait for T
53        where
54            T: $Trait,
55        {
56            fn $method(&mut self) -> Result<'_, &mut dyn $Trait> {
57                Ok(self)
58            }
59        }
60    };
61}
62
63duck_type!(pub AsInteractive(try_as_interactive): Interactive | InteractiveNotImplemented);
64
65duck_type_mut!(pub AsInteractiveMut(try_as_interactive_mut): Interactive | InteractiveNotImplemented);
66duck_type!(pub AsMethods(try_as_methods): Methods | MethodsNotImplemented);
67
68duck_type_mut!(pub AsMethodsMut(try_as_methods_mut): Methods | MethodsNotImplemented);
69duck_type!(pub AsDebug(try_as_debug): Debug | DebugNotImplemented);
70
71/// Add the appropriate $AsTrait impl for &dyn Interactive
72/// Prevents $AsTrait from using &(&dyn Interactive) or &(&mut dyn Interactive) as self
73macro_rules! deref_for_interactive {
74    ($AsTrait:ident ($method:ident) : $Trait:path) => {
75        impl $AsTrait for &dyn Interactive {
76            fn $method(&self) -> Result<'_, &dyn $Trait> {
77                (&**self).$method()
78            }
79        }
80
81        impl $AsTrait for &mut dyn Interactive {
82            fn $method(&self) -> Result<'_, &dyn $Trait> {
83                (&**self).$method()
84            }
85        }
86    };
87}
88
89/// Add the appropriate trait impl for &mut dyn Interactive
90/// Prevents $AsTrait from using &mut (&mut dyn Interactive) as self
91macro_rules! deref_for_interactive_mut {
92    ($AsTrait:ident ($method:ident) : $Trait:path) => {
93        impl $AsTrait for &mut dyn Interactive {
94            fn $method(&mut self) -> Result<'_, &mut dyn $Trait> {
95                (&mut **self).$method()
96            }
97        }
98    };
99}
100
101deref_for_interactive!(AsMethods(try_as_methods): Methods);
102deref_for_interactive_mut!(AsMethodsMut(try_as_methods_mut): Methods);
103deref_for_interactive!(AsDebug(try_as_debug): Debug);
104
105/// Used as a dummy value for types that don't implement Debug inside #[derive(PartialDebug)].
106#[allow(missing_copy_implementations)]
107#[derive(Debug)]
108pub struct Unknown;
rusteval/specialization.rs

rusteval/
specialization.rs
