From cad192882616f162fc0dbdd46ca32262713e6e23 Mon Sep 17 00:00:00 2001
From: Lann Martin <lann.martin@fermyon.com>
Date: Thu, 25 May 2023 14:36:47 -0400
Subject: [PATCH] Make `HostComponentDataHandle::from_any` non-pub, non-unsafe

Not only was this not really `unsafe`, it doesn't really need to be
`pub`.

Also added notes about panicing to docs.

Signed-off-by: Lann Martin <lann.martin@fermyon.com>
---
 crates/app/src/host_component.rs  | 11 +++--------
 crates/core/src/host_component.rs | 28 ++++++++++++++++++----------
 2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/crates/app/src/host_component.rs b/crates/app/src/host_component.rs
index d33bfceff2..e422dd52fe 100644
--- a/crates/app/src/host_component.rs
+++ b/crates/app/src/host_component.rs
@@ -76,17 +76,12 @@ impl DynamicHostComponents {
         host_component: DHC,
     ) -> anyhow::Result<HostComponentDataHandle<DHC>> {
         let host_component = Arc::new(host_component);
-        let handle = engine_builder
-            .add_host_component(host_component.clone())?
-            .into();
+        let handle = engine_builder.add_host_component(host_component.clone())?;
         self.host_components.push(DynamicHostComponentWithHandle {
             host_component,
-            handle,
+            handle: handle.into(),
         });
-        unsafe {
-            // Safe because `EngineBuilder::add_host_component` must have correct type.
-            Ok(HostComponentDataHandle::from_any(handle))
-        }
+        Ok(handle.into())
     }
 
     pub fn update_data(
diff --git a/crates/core/src/host_component.rs b/crates/core/src/host_component.rs
index 065902f17e..f476961c72 100644
--- a/crates/core/src/host_component.rs
+++ b/crates/core/src/host_component.rs
@@ -91,12 +91,7 @@ pub struct HostComponentDataHandle<HC: HostComponent> {
 }
 
 impl<HC: HostComponent> HostComponentDataHandle<HC> {
-    /// Return a typed handle to some [`HostComponent::Data`].
-    ///
-    /// # Safety
-    /// Caller must ensure that the handle is associated with the
-    /// given type or use of the handle will panic.
-    pub unsafe fn from_any(handle: AnyHostComponentDataHandle) -> Self {
+    fn from_any(handle: AnyHostComponentDataHandle) -> Self {
         Self {
             inner: handle,
             _phantom: PhantomData,
@@ -106,15 +101,18 @@ impl<HC: HostComponent> HostComponentDataHandle<HC> {
 
 impl<HC: HostComponent> Clone for HostComponentDataHandle<HC> {
     fn clone(&self) -> Self {
-        Self {
-            inner: self.inner,
-            _phantom: PhantomData,
-        }
+        Self::from_any(self.inner)
     }
 }
 
 impl<HC: HostComponent> Copy for HostComponentDataHandle<HC> {}
 
+impl<HC: HostComponent> From<HostComponentDataHandle<Arc<HC>>> for HostComponentDataHandle<HC> {
+    fn from(value: HostComponentDataHandle<Arc<HC>>) -> Self {
+        Self::from_any(value.inner)
+    }
+}
+
 #[doc(hidden)]
 pub trait DynSafeHostComponent {
     fn build_data_box(&self) -> AnyData;
@@ -201,6 +199,11 @@ impl HostComponentsData {
     /// Retrieves a mutable reference to [`HostComponent::Data`] for the given `handle`.
     ///
     /// If unset, the data will be initialized with [`HostComponent::build_data`].
+    ///
+    /// # Panics
+    ///
+    /// If the given handle was not obtained from the same [`HostComponentsBuilder`] that
+    /// was the source of this [`HostComponentsData`], this function may panic.
     pub fn get_or_insert<HC: HostComponent>(
         &mut self,
         handle: HostComponentDataHandle<HC>,
@@ -212,6 +215,11 @@ impl HostComponentsData {
     /// Retrieves a mutable reference to [`HostComponent::Data`] for the given `handle`.
     ///
     /// If unset, the data will be initialized with [`HostComponent::build_data`].
+    ///
+    /// # Panics
+    ///
+    /// If the given handle was not obtained from the same [`HostComponentsBuilder`] that
+    /// was the source of this [`HostComponentsData`], this function may panic.
     pub fn get_or_insert_any(&mut self, handle: AnyHostComponentDataHandle) -> &mut AnyData {
         let idx = handle.0;
         self.data[idx].get_or_insert_with(|| self.host_components[idx].build_data_box())