Note that Log implementors should call enabled

src/lib.rs

@@ -1273,10 +1273,18 @@ pub trait Log: Sync + Send {
     /// This is used by the `log_enabled!` macro to allow callers to avoid
     /// expensive computation of log message arguments if the message would be
     /// discarded anyway.
+    ///
+    /// # For implementors
+    ///
+    /// This method isn't called automatically by the `log!` macros.
+    /// It's up to an implementation of the `Log` trait to call `enabled` in its own
+    /// `log` method implementation to guarantee that filtering is applied.
     fn enabled(&self, metadata: &Metadata) -> bool;
 
     /// Logs the `Record`.
     ///
+    /// # For implementors
+    ///
     /// Note that `enabled` is *not* necessarily called before this method.
     /// Implementations of `log` should perform all necessary filtering
     /// internally.