# pyclass_slots.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/pyo3-0.13.2/src/pyclass_slots.rs`.
Keywords: rust, rustlang, rust-lang

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    //! This module contains additional fields for `#[pyclass]`..
    //! Mainly used by our proc-macro codes.
    use crate::{ffi, Python};

    /// Represents `__dict__` field for `#[pyclass]`.
    pub trait PyClassDict {
        const IS_DUMMY: bool = true;
        fn new() -> Self;
        fn clear_dict(&mut self, _py: Python) {}
        private_decl! {}
    }

    /// Represents `__weakref__` field for `#[pyclass]`.
    pub trait PyClassWeakRef {
        const IS_DUMMY: bool = true;
        fn new() -> Self;
        unsafe fn clear_weakrefs(&mut self, _obj: *mut ffi::PyObject, _py: Python) {}
        private_decl! {}
    }

    /// Zero-sized dummy field.
    pub struct PyClassDummySlot;

    impl PyClassDict for PyClassDummySlot {
        private_impl! {}
        fn new() -> Self {
            PyClassDummySlot
        }
    }

    impl PyClassWeakRef for PyClassDummySlot {
        private_impl! {}
        fn new() -> Self {
            PyClassDummySlot
        }
    }

    /// Actual dict field, which holds the pointer to `__dict__`.
    ///
    /// `#[pyclass(dict)]` automatically adds this.
    #[repr(transparent)]
    pub struct PyClassDictSlot(*mut ffi::PyObject);

    impl PyClassDict for PyClassDictSlot {
        private_impl! {}
        const IS_DUMMY: bool = false;
        fn new() -> Self {
            Self(std::ptr::null_mut())
        }
        fn clear_dict(&mut self, _py: Python) {
            if !self.0.is_null() {
                unsafe { ffi::PyDict_Clear(self.0) }
            }
        }
    }

    /// Actual weakref field, which holds the pointer to `__weakref__`.
    ///
    /// `#[pyclass(weakref)]` automatically adds this.
    #[repr(transparent)]
    pub struct PyClassWeakRefSlot(*mut ffi::PyObject);

    impl PyClassWeakRef for PyClassWeakRefSlot {
        private_impl! {}
        const IS_DUMMY: bool = false;
        fn new() -> Self {
            Self(std::ptr::null_mut())
        }
        unsafe fn clear_weakrefs(&mut self, obj: *mut ffi::PyObject, _py: Python) {
            if !self.0.is_null() {
                ffi::PyObject_ClearWeakRefs(obj)
            }
        }
    }