Implement upgrade method plus fix issue with previous PRs (#66)

Author: nekevss

oscars/src/collectors/mark_sweep/internals/ephemeron.rs

@@ -47,6 +47,16 @@ impl<K: Trace, V: Trace> Ephemeron<K, V> {
         None
     }
 
+    pub fn upgrade(&self) -> Option<Gc<K>> {
+        self.key.inner_ptr().map(|ptr| {
+            // Increment the roots, since we are creating a new root.
+            ptr.as_inner_ref().inc_roots();
+            // Safety: This is safe because WeakGc's collection insures
+            // the liveliness of the underlying pointer
+            unsafe { Gc::from_raw(ptr) }
+        })
+    }
+
     pub fn is_reachable(&self, color: TraceColor) -> bool {
         self.key.is_reachable(color)
     }

oscars/src/collectors/mark_sweep/pointers/gc.rs

@@ -37,7 +37,9 @@ impl<T: Trace> Gc<T> {
 
     /// Converts a `Gc` into a raw [`PoolPointer`].
     pub fn into_raw(this: Self) -> PoolPointer<'static, GcBox<T>> {
-        this.inner_ptr()
+        let ptr = this.inner_ptr();
+        core::mem::forget(this);
+        ptr
     }
 
     /// Creates a `Gc` from the provided [`PoolPointer`].
@@ -84,8 +86,10 @@ impl<T: Trace> Gc<T> {
     #[inline]
     #[must_use]
     pub unsafe fn cast_unchecked<U: Trace + 'static>(this: Self) -> Gc<U> {
+        let inner_ptr = this.inner_ptr;
+        core::mem::forget(this);
         Gc {
-            inner_ptr: this.inner_ptr,
+            inner_ptr,
             marker: PhantomData,
         }
     }

oscars/src/collectors/mark_sweep/pointers/weak.rs

@@ -3,7 +3,7 @@
 // optimized in the future
 use crate::{
     alloc::mempool3::PoolPointer,
-    collectors::mark_sweep::{Collector, Trace, internals::Ephemeron},
+    collectors::mark_sweep::{Collector, Gc, Trace, internals::Ephemeron},
 };
 
 #[repr(transparent)]
@@ -26,7 +26,12 @@ impl<T: Trace> WeakGc<T> {
         Self { inner_ptr }
     }
 
+    /// Returns the value of this [`WeakGc`] if the underlying value is alive.
     pub fn value(&self) -> Option<&T> {
         self.inner_ptr.as_inner_ref().key()
     }
+
+    pub fn upgrade(&self) -> Option<Gc<T>> {
+        self.inner_ptr.as_inner_ref().upgrade()
+    }
 }

oscars/src/collectors/mark_sweep_arena2/internals/ephemeron.rs

@@ -50,6 +50,16 @@ impl<K: Trace, V: Trace> Ephemeron<K, V> {
     pub(crate) fn invalidate(&self) {
         self.active.set(false);
     }
+
+    pub fn upgrade(&self) -> Option<Gc<K>> {
+        self.key.inner_ptr().map(|ptr| {
+            // Increment the root by one since we are upgrading this value.
+            ptr.as_inner_ref().inc_roots();
+            // Safety: This is safe because WeakGc's collection insures
+            // the liveliness of the underlying pointer
+            unsafe { Gc::from_raw(ptr) }
+        })
+    }
 }
 
 impl<K: Trace, V: Trace> Ephemeron<K, V> {

oscars/src/collectors/mark_sweep_arena2/pointers/gc.rs

@@ -40,7 +40,9 @@ impl<T: Trace> Gc<T> {
 
     /// Converts a `Gc` into a raw [`ArenaPointer`].
     pub fn into_raw(this: Self) -> ArenaPointer<'static, GcBox<T>> {
-        this.inner_ptr()
+        let ptr = this.inner_ptr();
+        core::mem::forget(this);
+        ptr
     }
 
     /// Creates a `Gc` from the provided [`ArenaPointer`].
@@ -88,8 +90,10 @@ impl<T: Trace> Gc<T> {
     #[inline]
     #[must_use]
     pub unsafe fn cast_unchecked<U: Trace + 'static>(this: Self) -> Gc<U> {
+        let inner_ptr = this.inner_ptr;
+        core::mem::forget(this);
         Gc {
-            inner_ptr: this.inner_ptr,
+            inner_ptr,
             marker: PhantomData,
         }
     }

oscars/src/collectors/mark_sweep_arena2/pointers/weak.rs

@@ -3,7 +3,7 @@
 // optimized in the future
 use crate::{
     alloc::arena2::ArenaPointer,
-    collectors::mark_sweep_arena2::{Trace, internals::Ephemeron},
+    collectors::mark_sweep_arena2::{Gc, Trace, internals::Ephemeron},
 };
 
 #[repr(transparent)]
@@ -33,4 +33,8 @@ impl<T: Trace> WeakGc<T> {
     pub fn value(&self) -> Option<&T> {
         self.inner_ptr.as_inner_ref().key()
     }
+
+    pub fn upgrade(&self) -> Option<Gc<T>> {
+        self.inner_ptr.as_inner_ref().upgrade()
+    }
 }