Build Scalar with ArrayRef

[jayzhan211]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Describe the solution you'd like

I want to build Scalar with ArrayRef, but I got an err

error[E0277]: the trait bound `std::sync::Arc<arrow_array::GenericListArray<i32>>: arrow_array::Array` is not satisfied
    --> datafusion/common/src/scalar/mod.rs:3352:29
     |
3352 |         let s = Scalar::new(arr);
     |                 ----------- ^^^ the trait `arrow_array::Array` is not implemented for `std::sync::Arc<arrow_array::GenericListArray<i32>>`
     |                 |
     |                 required by a bound introduced by this call
     |
     = help: the trait `arrow_array::Array` is implemented for `std::sync::Arc<(dyn arrow_array::Array + 'static)>`
note: required by a bound in `arrow_array::Scalar::<T>::new`
    --> /Users/jayzhan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-array-50.0.0/src/scalar.rs:130:9
     |
130  | impl<T: Array> Scalar<T> {
     |         ^^^^^ required by this bound in `Scalar::<T>::new`
...
136  |     pub fn new(array: T) -> Self {
     |            --- required by a bound in this associated function

error[E0277]: the trait bound `std::sync::Arc<arrow_array::GenericListArray<i32>>: arrow_array::Array` is not satisfied
    --> datafusion/common/src/scalar/mod.rs:3352:17
     |
3352 |         let s = Scalar::new(arr);
     |                 ^^^^^^^^^^^^^^^^ the trait `arrow_array::Array` is not implemented for `std::sync::Arc<arrow_array::GenericListArray<i32>>`
     |
     = help: the trait `arrow_array::Array` is implemented for `std::sync::Arc<(dyn arrow_array::Array + 'static)>`
note: required by a bound in `arrow_array::Scalar`
    --> /Users/jayzhan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-array-50.0.0/src/scalar.rs:128:22
     |
128  | pub struct Scalar<T: Array>(T);
     |                      ^^^^^ required by this bound in `Scalar`

error[E0277]: the trait bound `std::sync::Arc<arrow_array::GenericListArray<i32>>: arrow_array::Array` is not satisfied
    --> datafusion/common/src/scalar/mod.rs:3353:26
     |
3353 |         println!("{:?}", s);
     |                   ----   ^ the trait `arrow_array::Array` is not implemented for `std::sync::Arc<arrow_array::GenericListArray<i32>>`
     |                   |
     |                   required by a bound introduced by this call
     |
     = help: the trait `arrow_array::Array` is implemented for `std::sync::Arc<(dyn arrow_array::Array + 'static)>`
     = note: required for `arrow_array::Scalar<std::sync::Arc<arrow_array::GenericListArray<i32>>>` to implement `Debug`
note: required by a bound in `core::fmt::rt::Argument::<'a>::new_debug`
    --> /Users/jayzhan/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/fmt/rt.rs:100:29
     |
100  |     pub fn new_debug<'b, T: Debug>(x: &'b T) -> Argument<'_> {
     |                             ^^^^^ required by this bound in `Argument::<'a>::new_debug`
     = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)

This is what the code is like which we can also find in Scalar Example, but turns out not working

        let arr = Arc::new(ListArray::from_iter_primitive::<Int32Type, _, _>(vec![
            Some(vec![Some(1), None, Some(2)]),
        ]));
        println!("{:?}", arr);
        let s = Scalar::new(arr);
        println!("{:?}", s);

I'm working on apache/datafusion#8846, and trying to find whether Scalar<Arc<ListArray>> or Arc<Scalar<ListArray>> is better.

however, the previous one meets the error described above, the second one we can only get &dyn Array from fn get(), which doesn't seem like a good way either.

Describe alternatives you've considered

Remove the example that is built with ArrayRef.

Additional context

[jayzhan211]

I forgot to cast to ArrayRef..