From be81dd0923101b647850e4eb257e250d30b78d47 Mon Sep 17 00:00:00 2001
From: Jeong Yunwon <jeong@youknowone.org>
Date: Tue, 17 May 2022 07:34:01 +0900
Subject: [PATCH] PyExact as counterpart of PyExactRef

---
 vm/src/lib.rs        |   2 +-
 vm/src/object/ext.rs | 100 +++++++++++++++++++++++++++++++++++++++++--
 vm/src/prelude.rs    |   3 +-
 3 files changed, 100 insertions(+), 5 deletions(-)

diff --git a/vm/src/lib.rs b/vm/src/lib.rs
index c2370c4ba..a772e4604 100644
--- a/vm/src/lib.rs
+++ b/vm/src/lib.rs
@@ -77,7 +77,7 @@ pub mod vm;
 
 pub use self::convert::{TryFromBorrowedObject, TryFromObject};
 pub use self::object::{
-    AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyRefExact, PyResult, PyWeakRef,
+    AsObject, Py, PyExact, PyObject, PyObjectRef, PyPayload, PyRef, PyRefExact, PyResult, PyWeakRef,
 };
 pub use self::vm::{Context, Interpreter, Settings, VirtualMachine};
 
diff --git a/vm/src/object/ext.rs b/vm/src/object/ext.rs
index 67105953f..d46490af0 100644
--- a/vm/src/object/ext.rs
+++ b/vm/src/object/ext.rs
@@ -58,7 +58,66 @@ where
     }
 }
 
+#[repr(transparent)]
+pub struct PyExact<T: PyObjectPayload> {
+    inner: Py<T>,
+}
+
+impl<T: PyPayload> PyExact<T> {
+    /// # Safety
+    /// Given reference must be exact type of payload T
+    #[inline(always)]
+    pub unsafe fn ref_unchecked(r: &Py<T>) -> &Self {
+        &*(r as *const _ as *const Self)
+    }
+}
+
+impl<T: PyPayload> Deref for PyExact<T> {
+    type Target = Py<T>;
+    #[inline(always)]
+    fn deref(&self) -> &Py<T> {
+        &self.inner
+    }
+}
+
+impl<T: PyObjectPayload> Borrow<PyObject> for PyExact<T> {
+    #[inline(always)]
+    fn borrow(&self) -> &PyObject {
+        self.inner.borrow()
+    }
+}
+
+impl<T: PyObjectPayload> AsRef<PyObject> for PyExact<T> {
+    #[inline(always)]
+    fn as_ref(&self) -> &PyObject {
+        self.inner.as_ref()
+    }
+}
+
+impl<T: PyObjectPayload> Borrow<Py<T>> for PyExact<T> {
+    #[inline(always)]
+    fn borrow(&self) -> &Py<T> {
+        &self.inner
+    }
+}
+
+impl<T: PyObjectPayload> AsRef<Py<T>> for PyExact<T> {
+    #[inline(always)]
+    fn as_ref(&self) -> &Py<T> {
+        &self.inner
+    }
+}
+
+impl<T: PyPayload> std::borrow::ToOwned for PyExact<T> {
+    type Owned = PyRefExact<T>;
+    fn to_owned(&self) -> Self::Owned {
+        let owned = self.inner.to_owned();
+        unsafe { PyRefExact::new_unchecked(owned) }
+    }
+}
+
 #[derive(Debug)]
+#[repr(transparent)]
 pub struct PyRefExact<T: PyObjectPayload> {
     inner: PyRef<T>,
 }
@@ -109,10 +168,31 @@ impl<T: PyPayload> TryFromObject for PyRefExact<T> {
 }
 
 impl<T: PyPayload> Deref for PyRefExact<T> {
-    type Target = PyRef<T>;
+    type Target = PyExact<T>;
     #[inline(always)]
-    fn deref(&self) -> &PyRef<T> {
-        &self.inner
+    fn deref(&self) -> &PyExact<T> {
+        unsafe { PyExact::ref_unchecked(self.inner.deref()) }
+    }
+}
+
+impl<T: PyObjectPayload> Borrow<PyObject> for PyRefExact<T> {
+    #[inline(always)]
+    fn borrow(&self) -> &PyObject {
+        self.inner.borrow()
+    }
+}
+
+impl<T: PyObjectPayload> AsRef<PyObject> for PyRefExact<T> {
+    #[inline(always)]
+    fn as_ref(&self) -> &PyObject {
+        self.inner.as_ref()
+    }
+}
+
+impl<T: PyObjectPayload> Borrow<Py<T>> for PyRefExact<T> {
+    #[inline(always)]
+    fn borrow(&self) -> &Py<T> {
+        self.inner.borrow()
     }
 }
 
@@ -123,6 +203,20 @@ impl<T: PyObjectPayload> AsRef<Py<T>> for PyRefExact<T> {
     }
 }
 
+impl<T: PyPayload> Borrow<PyExact<T>> for PyRefExact<T> {
+    #[inline(always)]
+    fn borrow(&self) -> &PyExact<T> {
+        self
+    }
+}
+
+impl<T: PyPayload> AsRef<PyExact<T>> for PyRefExact<T> {
+    #[inline(always)]
+    fn as_ref(&self) -> &PyExact<T> {
+        self
+    }
+}
+
 impl<T: PyPayload> ToPyObject for PyRefExact<T> {
     #[inline(always)]
     fn to_pyobject(self, _vm: &VirtualMachine) -> PyObjectRef {
diff --git a/vm/src/prelude.rs b/vm/src/prelude.rs
index 415e7da79..0bd0fe88b 100644
--- a/vm/src/prelude.rs
+++ b/vm/src/prelude.rs
@@ -1,6 +1,7 @@
 pub use crate::{
     object::{
-        AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyRefExact, PyResult, PyWeakRef,
+        AsObject, Py, PyExact, PyObject, PyObjectRef, PyPayload, PyRef, PyRefExact, PyResult,
+        PyWeakRef,
     },
     vm::{Context, Interpreter, Settings, VirtualMachine},
 };