feat: add crate swift-rs

swift-rs/src-rs/swift_ret.rs

@@ -0,0 +1,55 @@
+use crate::{swift::SwiftObject, *};
+use std::ffi::c_void;
+
+/// Identifies a type as being a valid return type from a Swift function.
+/// For types that are objects which need extra retains,
+/// the [`retain`](SwiftRet::retain) function will be re-implemented.
+pub trait SwiftRet {
+    /// Adds a retain to the value if possible
+    ///
+    /// # Safety
+    /// Just don't use this.
+    /// Let [`swift!`] handle it.
+    unsafe fn retain(&self) {}
+}
+
+macro_rules! primitive_impl {
+    ($($t:ty),+) => {
+        $(impl SwiftRet for $t {
+        })+
+    };
+}
+
+primitive_impl!(
+    Bool,
+    Int,
+    Int8,
+    Int16,
+    Int32,
+    Int64,
+    UInt,
+    UInt8,
+    UInt16,
+    UInt32,
+    UInt64,
+    Float32,
+    Float64,
+    *const c_void,
+    *mut c_void,
+    *const u8,
+    ()
+);
+
+impl<T: SwiftObject> SwiftRet for Option<T> {
+    unsafe fn retain(&self) {
+        if let Some(v) = self {
+            v.retain()
+        }
+    }
+}
+
+impl<T: SwiftObject> SwiftRet for T {
+    unsafe fn retain(&self) {
+        (*self).retain()
+    }
+}