add Sealed to probe and pyfunction traits (#5806)

* add Sealed to probe traits

* add Sealed to pyfunction traits

Author: luxedo

src/impl_/pyclass/probes.rs

@@ -14,14 +14,20 @@ use crate::{FromPyObject, Py, PyClass, PyClassInitializer};
 /// The true case is defined in the zero-sized type's impl block, which is
 /// gated on some property like trait bound or only being implemented
 /// for fixed concrete types.
-pub trait Probe {
+pub trait Probe: probe::Sealed {
     const VALUE: bool = false;
 }
 
+/// Seals `Probe` so that types outside PyO3 cannot implement it.
+mod probe {
+    pub trait Sealed {}
+}
+
 macro_rules! probe {
     ($name:ident) => {
         pub struct $name<T>(PhantomData<T>);
         impl<T> Probe for $name<T> {}
+        impl<T> probe::Sealed for $name<T> {}
     };
 }
 
@@ -93,6 +99,7 @@ impl<E> IsReturningEmptyTuple<Result<(), E>> {
 }
 
 probe!(IsPyClass);
+
 impl<T> IsPyClass<T>
 where
     T: PyClass,
@@ -108,6 +115,7 @@ where
 }
 
 probe!(IsInitializerTuple);
+
 impl<S, B> IsInitializerTuple<(S, B)>
 where
     S: PyClass<BaseType = B>,

src/impl_/pyfunction.rs

@@ -39,10 +39,22 @@ impl PyFunctionDef {
 
 /// Trait to enable the use of `wrap_pyfunction` with both `Python` and `PyModule`,
 /// and also to infer the return type of either `&'py PyCFunction` or `Bound<'py, PyCFunction>`.
-pub trait WrapPyFunctionArg<'py, T> {
+pub trait WrapPyFunctionArg<'py, T>: wrap_pyfunctionarg::Sealed {
     fn wrap_pyfunction(self, function_def: &'static PyFunctionDef) -> PyResult<T>;
 }
 
+/// Seals `WrapPyFunctionArg` so that types outside PyO3 cannot implement it.
+mod wrap_pyfunctionarg {
+    use crate::{types::PyModule, Borrowed, Bound, Python};
+
+    pub trait Sealed {}
+    impl<'py> Sealed for Bound<'py, PyModule> {}
+    impl<'py> Sealed for &Bound<'py, PyModule> {}
+    impl<'a, 'py> Sealed for Borrowed<'a, 'py, PyModule> {}
+    impl<'a, 'py> Sealed for &Borrowed<'a, 'py, PyModule> {}
+    impl<'py> Sealed for Python<'py> {}
+}
+
 impl<'py> WrapPyFunctionArg<'py, Bound<'py, PyCFunction>> for Bound<'py, PyModule> {
     fn wrap_pyfunction(
         self,