[GitHub] [arrow-rs] viirya commented on pull request #1367: More idiomatic primitive array creation

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

viirya commented on pull request #1367:
URL: https://github.com/apache/arrow-rs/pull/1367#issuecomment-1054982569


   > Today if people `impl Borrow<i8> for MyAwesomeType` then I think (untested) they can create arrays from an iterator of `MyAwesomeType` which they might not be able to do after this PR 🤔 Though perhaps they just need to implement `ArrowPrimitiveTypeNative`
   
   I guess you mean `impl Borrow<Option<i8>> for MyAwesomeType`? Yes, this is a concern. People need to implement `impl From<MyAwesomeType> for ArrowPrimitiveTypeNative<Int8Type>`.
   
   
   > I tried a little to figure out a clever way to implement the conversion using a trait that is a superset of `Borrow` to make it backwards compatible and more general. Thus instead of
   > 
   > ```rust
   > impl<T: ArrowPrimitiveType, Ptr: Borrow<Option<<T as ArrowPrimitiveType>::Native>>>
   >     FromIterator<Ptr> for PrimitiveArray<T>
   > ```
   > 
   > It would look something like
   > 
   > ```rust
   > impl<T: ArrowPrimitiveType, Ptr: BorrowAsOption<<T as ArrowPrimitiveType>::Native>>
   >     FromIterator<Ptr> for PrimitiveArray<T>
   > ..
   > 
   > pub trait BorrowAsOption<T: ArrowPrimitiveType> {
   >     fn as_native(&self) -> Option<&<T as ArrowPrimitiveType>::Native>;
   > }
   > ```
   > 
   > But my mind was being blown by type errors.
   
   Not sure if I understand above way. Seems people still need to implement `BorrowAsOption`, so it's still not backwards compatible.
   
   


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