kosiew commented on code in PR #17081:
URL: https://github.com/apache/datafusion/pull/17081#discussion_r2266911805
##########
datafusion/expr/src/udwf.rs:
##########
@@ -82,15 +82,15 @@ impl Display for WindowUDF {
impl PartialEq for WindowUDF {
fn eq(&self, other: &Self) -> bool {
- self.inner.equals(other.inner.as_ref())
+ self.inner.dyn_eq(&other.inner)
}
Review Comment:
should this be
```rust
self.inner.as_ref().dyn_eq(other.inner.as_ref().as_any())
```
to ensure the implementor’s dyn_eq sees &dyn Any of the concrete type (F),
making the downcast succeed when appropriate.
##########
datafusion/expr/src/udwf.rs:
##########
@@ -229,6 +229,10 @@ where
/// This trait exposes the full API for implementing user defined window
functions and
/// can be used to implement any function.
///
+/// While the trait depends on [`DynEq`] and [`DynHash`] traits, these should
not be
+/// implemented directly. Instead, implement [`Eq`] and [`Hash`] and leverage
the
+/// blanked implementations of [`DynEq`] and [`DynHash`].
Review Comment:
```suggestion
/// blanket implementations of [`DynEq`] and [`DynHash`].
```
##########
datafusion/expr-common/src/dyn_eq.rs:
##########
@@ -0,0 +1,67 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::any::Any;
+use std::hash::{Hash, Hasher};
+
+/// A dyn-compatible version of [`Eq`] trait.
+/// The implementation constraints for this trait are the same as for [`Eq`]:
+/// the implementation must be reflexive, symmetric, and transitive.
+/// Additionally, if two values can be compared with [`DynEq`] and
[`PartialEq`] then
+/// they must be [`DynEq`]-equal if and only if they are [`PartialEq`]-equal.
+/// It is therefore strongly discouraged to implement this trait for types
+/// that implement `PartialEq<Other>` or `Eq<Other>` for any type `Other`
other than `Self`.
+///
+/// Note: This trait should not be implemented directly. Implement `Eq` and
`Any` and use
+/// the blanket implementation.
+pub trait DynEq {
+ fn dyn_eq(&self, other: &dyn Any) -> bool;
+
+ fn
i_did_not_implement_the_trait_directly_but_using_the_blanked_impl_instead()
Review Comment:
This doesn’t prevent downstream manual impls. Maybe use the sealed-trait
pattern instead?
```rust
/// Sealed traits, not exported outside this module. Only types in this crate
/// implementing `Eq + Any` (resp. `Hash + Any`) get these impls.
mod sealed {
use super::*;
pub trait DynEqSealed {}
impl<T: Eq + Any> DynEqSealed for T {}
pub trait DynHashSealed {}
impl<T: Hash + Any> DynHashSealed for T {}
}
/// A dyn-compatible version of [`Eq`] trait.
/// Now sealed, so external crates cannot impl this themselves.
pub trait DynEq: sealed::DynEqSealed {
fn dyn_eq(&self, other: &dyn Any) -> bool;
}
```
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