Better document event context argument restrictions

matrix_sdk/src/client.rs

@@ -888,9 +888,13 @@ impl Client {
     /// [`Client`] also implements the `EventHandlerContext` trait
     /// so you don't have to clone your client into the event handler manually.
     ///
-    /// Invalid context arguments, for example a [`Room`][room::Room] as an
-    /// argument to an account data event handler, will result in the event
-    /// handler being skipped and an error logged.
+    /// Some context arguments are not universally applicable. A context
+    /// argument that isn't available for the given event type will result in
+    /// the event handler being skipped and an error being logged. The following
+    /// context argument types are only available for a subset of event types:
+    ///
+    /// * [`Room`][room::Room] is only available for room-specific events, i.e.
+    ///   not for events like global account data events or presence events
     ///
     /// [`EventHandlerContext`]: crate::event_handler::EventHandlerContext
     ///

matrix_sdk/src/event_handler.rs

@@ -134,6 +134,12 @@ impl EventHandlerContext for Client {
     }
 }
 
+/// This event handler context argument is only applicable to room-specific
+/// events.
+///
+/// Trying to use it in the event handler for another event, for example a
+/// global account data or presence event, will result in the event handler
+/// being skipped and an error getting logged.
 impl EventHandlerContext for room::Room {
     fn from_data(data: &EventHandlerData<'_>) -> Option<Self> {
         data.room.clone()