pyo3/impl_/pyclass/
probes.rs

1use std::marker::PhantomData;
2
3use crate::{conversion::IntoPyObject, FromPyObject, Py};
4
5/// Trait used to combine with zero-sized types to calculate at compile time
6/// some property of a type.
7///
8/// The trick uses the fact that an associated constant has higher priority
9/// than a trait constant, so we can use the trait to define the false case.
10///
11/// The true case is defined in the zero-sized type's impl block, which is
12/// gated on some property like trait bound or only being implemented
13/// for fixed concrete types.
14pub trait Probe {
15    const VALUE: bool = false;
16}
17
18macro_rules! probe {
19    ($name:ident) => {
20        pub struct $name<T>(PhantomData<T>);
21        impl<T> Probe for $name<T> {}
22    };
23}
24
25probe!(IsPyT);
26
27impl<T> IsPyT<Py<T>> {
28    pub const VALUE: bool = true;
29}
30
31probe!(IsIntoPyObjectRef);
32
33impl<'a, 'py, T: 'a> IsIntoPyObjectRef<T>
34where
35    &'a T: IntoPyObject<'py>,
36{
37    pub const VALUE: bool = true;
38}
39
40probe!(IsIntoPyObject);
41
42impl<'py, T> IsIntoPyObject<T>
43where
44    T: IntoPyObject<'py>,
45{
46    pub const VALUE: bool = true;
47}
48
49probe!(IsSend);
50
51impl<T: Send> IsSend<T> {
52    pub const VALUE: bool = true;
53}
54
55probe!(IsSync);
56
57impl<T: Sync> IsSync<T> {
58    pub const VALUE: bool = true;
59}
60
61probe!(IsFromPyObject);
62
63impl<'a, 'py, T> IsFromPyObject<T>
64where
65    T: FromPyObject<'a, 'py>,
66{
67    pub const VALUE: bool = true;
68}
69
70probe!(HasNewTextSignature);
71
72impl<T: super::doc::PyClassNewTextSignature> HasNewTextSignature<T> {
73    pub const VALUE: bool = true;
74}
75
76probe!(IsClone);
77
78impl<T: Clone> IsClone<T> {
79    pub const VALUE: bool = true;
80}
81
82probe!(IsReturningEmptyTuple);
83
84impl IsReturningEmptyTuple<()> {
85    pub const VALUE: bool = true;
86}
87
88impl<E> IsReturningEmptyTuple<Result<(), E>> {
89    pub const VALUE: bool = true;
90}
91
92#[cfg(test)]
93macro_rules! value_of {
94    ($probe:ident, $ty:ty) => {{
95        #[allow(unused_imports)] // probe trait not used if VALUE is true
96        use crate::impl_::pyclass::Probe as _;
97        $probe::<$ty>::VALUE
98    }};
99}
100
101#[cfg(test)]
102pub(crate) use value_of;
pyo3/impl_/pyclass/probes.rs

pyo3/impl_/pyclass/
probes.rs
