shepmaster commented on pull request #984:
URL: https://github.com/apache/arrow-rs/pull/984#issuecomment-992777187
> avoid having to add type annotations to the call of `eq_dict_scalar`?
You can likely infer the first type (`eq_dict_scalar::<_, UInt8Type>(&array,
123)`) because the type is directly related to the `left` argument:
```rust
pub fn eq_dict_scalar<T, K>(
left: &DictionaryArray<K>,
right: T::Native,
) -> Result<BooleanArray>
where
T: ArrowNumericType,
K: ArrowNumericType,
```
The problem with the `right` argument is that there's potentially an
infinite number of concrete `T` types that could have a matching associated
type `Native`:
```rust
impl ArrowNumericType for OneThing {
type Native = u8;
}
impl ArrowNumericType for SomeOtherThing {
type Native = u8;
}
```
I won't claim to have read the code thoroughly, but I'm not yet
understanding why there are two generics here. Could you change the function to
have only one?
```rust
pub fn eq_dict_scalar<K>(
left: &DictionaryArray<K>,
right: K::Native,
) -> Result<BooleanArray>
where
K: ArrowNumericType,
```
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