[GitHub] [arrow-rs] alamb edited a comment on issue #996: Remove unsafe from Buffer::typed_data

[GitBox <gi...@apache.org>]

alamb edited a comment on issue #996:
URL: https://github.com/apache/arrow-rs/issues/996#issuecomment-986042173


   I reviewed the code a bit more, and the comments make a great point:
   
   ```
       /// `ArrowNativeType` is public so that it can be used as a trait bound for other public
       /// components, such as the `ToByteSlice` trait.  However, this means that it can be
       /// implemented by user defined types, which it is not intended for.
   ```
   
   Meaning that if a user implements `ArrowNativeType` for their types, this will result in undefined behavior. 
   
   I also looked more carefully at Buffer and it effectively allows reinterpreting arbitrary `bytes` as different types, so I am not sure that behavior is safe...
   
   What could 
    be done is make `MutableBuffer::typed_data` unsafe instead as the docs there say very specifically 
   
   ```
       /// # Safety
       /// This function must only be used when this buffer was extended with items of type `T`.
       /// Failure to do so results in undefined behavior.
   ```


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