alamb commented on issue #1128:
URL: https://github.com/apache/arrow-rs/issues/1128#issuecomment-1003731598
I tried a blanket implementation like
```rust
/// Anything that can be retrieved as &dyn Array is also an Array
impl<T> Array for T
where T: AsRef<dyn Array> + fmt::Debug + Send + Sync + JsonEqual
{
fn as_any(&self) -> &dyn Any {
self.as_ref().as_any()
}
fn data(&self) -> &ArrayData {
self.as_ref().data()
}
}
/// Anything that can be retrieved as &dyn Array is also an Array
impl<T> JsonEqual for T
where T: AsRef<dyn JsonEqual>
{
fn equals_json(&self, json: &[&serde_json::Value]) -> bool {
self.as_ref().equals_json(json)
}
}
```
But that resulted in an error like
```
-*- mode: compilation; default-directory: "~/Software/arrow-rs/" -*-
Compilation started at Sun Jan 2 10:20:57
cd /Users/alamb/Software/arrow-rs && RUST_BACKTRACE=1
CARGO_TARGET_DIR=/Users/alamb/Software/df-target cargo test -p arrow
Compiling arrow v7.0.0-SNAPSHOT (/Users/alamb/Software/arrow-rs/arrow)
error[E0277]: the trait bound `std::sync::Arc<(dyn array::array::Array +
'static)>: AsRef<(dyn equal_json::JsonEqual + 'static)>` is not satisfied
--> arrow/src/array/array.rs:884:34
|
884 | assert!(compute_my_thing(&arr));
| ---------------- ^^^^ the trait `AsRef<(dyn
equal_json::JsonEqual + 'static)>` is not implemented for `std::sync::Arc<(dyn
array::array::Array + 'static)>`
| |
| required by a bound introduced by this call
|
= help: the following implementations were found:
<std::sync::Arc<T> as AsRef<T>>
note: required because of the requirements on the impl of
`equal_json::JsonEqual` for `std::sync::Arc<(dyn array::array::Array +
'static)>`
--> arrow/src/array/array.rs:241:9
|
241 | impl<T> JsonEqual for T
| ^^^^^^^^^ ^
note: required because of the requirements on the impl of
`array::array::Array` for `std::sync::Arc<(dyn array::array::Array + 'static)>`
--> arrow/src/array/array.rs:228:9
|
228 | impl<T> Array for T
| ^^^^^ ^
= note: required for the cast to the object type `dyn
array::array::Array`
error[E0308]: mismatched types
--> arrow/src/array/array.rs:887:34
|
887 | assert!(compute_my_thing(arr));
| ^^^ expected reference, found struct
`std::sync::Arc`
|
= note: expected reference `&dyn array::array::Array`
found struct `std::sync::Arc<(dyn array::array::Array +
'static)>`
Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.
error: could not compile `arrow` due to 2 previous errors
warning: build failed, waiting for other jobs to finish...
error: build failed
```
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