Merge pull request #1450 from hannobraun/partial

Improve usability of `Partial`

crates/fj-kernel/src/partial/wrapper.rs

@@ -76,7 +76,7 @@ impl<T: HasPartial + 'static> Partial<T> {
     /// # Panics
     ///
     /// Panics, if this method is called while the return value from a previous
-    /// call is still borrowed.
+    /// call to this method of [`Self::read`] is still borrowed.
     pub fn write(&mut self) -> impl DerefMut<Target = T::Partial> + '_ {
         let mut inner = self.inner.write();
 
@@ -91,7 +91,7 @@ impl<T: HasPartial + 'static> Partial<T> {
     ///
     /// # Panics
     ///
-    /// Panics, if a return value of [`Self::write`] is still borrowed.
+    /// Panics, if a call to [`Self::write`] would panic.
     pub fn build(self, objects: &mut Service<Objects>) -> Handle<T>
     where
         T: Insert,
@@ -168,13 +168,15 @@ impl<T: HasPartial> Inner<T> {
     }
 
     fn read(&self) -> RwLockReadGuard<InnerObject<T>> {
-        self.0.read()
+        self.0
+            .try_read()
+            .expect("Tried to read `Partial` that is currently being modified")
     }
 
     fn write(&self) -> RwLockWriteGuard<InnerObject<T>> {
         self.0
             .try_write()
-            .expect("Tried to modify `Partial` that is already being modified")
+            .expect("Tried to modify `Partial` that is currently locked")
     }
 }