DOC: Document when Ok(None) is returned

rust/dbn/src/decode.rs

@@ -39,7 +39,8 @@ use crate::{
 
 /// Trait for types that decode references to DBN records of a dynamic type.
 pub trait DecodeRecordRef {
-    /// Tries to decode a generic reference a record.
+    /// Tries to decode a generic reference a record. Returns `Ok(None)` if input
+    /// has been exhausted.
     ///
     /// # Errors
     /// This function returns an error if the underlying reader returns an error of a

rust/dbn/src/decode/dbn/async.rs

@@ -66,7 +66,7 @@ where
     }
 
     /// Tries to decode a single record and returns a reference to the record that
-    /// lasts until the next method call. Returns `None` if `reader` has been
+    /// lasts until the next method call. Returns `Ok(None)` if `reader` has been
     /// exhausted.
     ///
     /// # Errors
@@ -80,7 +80,7 @@ where
     }
 
     /// Tries to decode a single record and returns a reference to the record that
-    /// lasts until the next method call. Returns `None` if `reader` has been
+    /// lasts until the next method call. Returns `Ok(None)` if `reader` has been
     /// exhausted.
     ///
     /// # Errors

rust/dbn/src/decode/dbn/sync.rs

@@ -231,7 +231,8 @@ where
         }
     }
 
-    /// Tries to decode a generic reference a record.
+    /// Tries to decode a generic reference a record. Returns `Ok(None)` if
+    /// the reader is exhausted.
     ///
     /// # Errors
     /// This function returns an error if the underlying reader returns an