Remove as_any from scalar UDF trait definition (#20812)

## Which issue does this PR close?

None.

## Rationale for this change

This PR reduces the amount of boilerplate code that users need to write
for scalar UDFs. I didn't address aggregate or window functions yet just
to keep the size of the PR manageable.

## What changes are included in this PR?

Now that we have [trait
upcasting](https://blog.rust-lang.org/2025/04/03/Rust-1.86.0/) since
rust 1.86, we no longer need every implementation of `ScalarUDFImpl` to
have the `as_any` function that returns `&self`. This PR makes `Any` an
supertrait for `ScalarUDFImpl` and makes the appropriate casts when
necessary. The overall diff is about 1200 lines of code removed.

## Are these changes tested?

Existing unit tests.

## Are there any user-facing changes?

Users simply need to remove the `as_any()` function from their
implementations.

Author: timsaucer

datafusion-examples/examples/builtin_functions/function_factory.rs

@@ -118,10 +118,6 @@ struct ScalarFunctionWrapper {
 }
 
 impl ScalarUDFImpl for ScalarFunctionWrapper {
-    fn as_any(&self) -> &dyn std::any::Any {
-        self
-    }
-
     fn name(&self) -> &str {
         &self.name
     }

datafusion-examples/examples/data_io/json_shredding.rs

@@ -17,7 +17,6 @@
 
 //! See `main.rs` for how to run it.
 
-use std::any::Any;
 use std::sync::Arc;
 
 use arrow::array::{RecordBatch, StringArray};
@@ -207,10 +206,6 @@ impl Default for JsonGetStr {
 }
 
 impl ScalarUDFImpl for JsonGetStr {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         "json_get_str"
     }

datafusion-examples/examples/query_planning/optimizer_rule.rs

@@ -28,7 +28,6 @@ use datafusion::logical_expr::{
 use datafusion::optimizer::ApplyOrder;
 use datafusion::optimizer::{OptimizerConfig, OptimizerRule};
 use datafusion::prelude::SessionContext;
-use std::any::Any;
 use std::sync::Arc;
 
 /// This example demonstrates how to add your own [`OptimizerRule`]
@@ -190,10 +189,6 @@ impl MyEq {
 }
 
 impl ScalarUDFImpl for MyEq {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         "my_eq"
     }

datafusion-examples/examples/udf/advanced_udf.rs

@@ -17,7 +17,6 @@
 
 //! See `main.rs` for how to run it.
 
-use std::any::Any;
 use std::sync::Arc;
 
 use arrow::array::{
@@ -66,10 +65,6 @@ impl PowUdf {
 
 impl ScalarUDFImpl for PowUdf {
     /// We implement as_any so that we can downcast the ScalarUDFImpl trait object
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     /// Return the name of this function
     fn name(&self) -> &str {
         "pow"

datafusion-examples/examples/udf/async_udf.rs

@@ -23,7 +23,7 @@
 //! making network requests. This can be used for tasks like fetching
 //! data from an external API such as a LLM service or an external database.
 
-use std::{any::Any, sync::Arc};
+use std::sync::Arc;
 
 use arrow::array::{ArrayRef, BooleanArray, Int64Array, RecordBatch, StringArray};
 use arrow_schema::{DataType, Field, Schema};
@@ -160,10 +160,6 @@ impl AskLLM {
 /// information for the function, such as its name, signature, and return type.
 /// [async_trait]
 impl ScalarUDFImpl for AskLLM {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         "ask_llm"
     }

datafusion/core/tests/fuzz_cases/equivalence/utils.rs

@@ -15,7 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use std::any::Any;
 use std::cmp::Ordering;
 use std::sync::Arc;
 
@@ -531,9 +530,6 @@ impl TestScalarUDF {
 }
 
 impl ScalarUDFImpl for TestScalarUDF {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
     fn name(&self) -> &str {
         "test-scalar-udf"
     }

datafusion/core/tests/physical_optimizer/projection_pushdown.rs

@@ -15,7 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use std::any::Any;
 use std::sync::Arc;
 
 use arrow::compute::SortOptions;
@@ -79,10 +78,6 @@ impl DummyUDF {
 }
 
 impl ScalarUDFImpl for DummyUDF {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         "dummy_udf"
     }

datafusion/core/tests/user_defined/user_defined_async_scalar_functions.rs

@@ -129,10 +129,6 @@ impl TestAsyncUDFImpl {
 }
 
 impl ScalarUDFImpl for TestAsyncUDFImpl {
-    fn as_any(&self) -> &dyn std::any::Any {
-        self
-    }
-
     fn name(&self) -> &str {
         "test_async_udf"
     }

datafusion/core/tests/user_defined/user_defined_scalar_functions.rs

@@ -15,7 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use std::any::Any;
 use std::collections::HashMap;
 use std::hash::{Hash, Hasher};
 use std::sync::Arc;
@@ -201,10 +200,6 @@ impl std::fmt::Debug for Simple0ArgsScalarUDF {
 }
 
 impl ScalarUDFImpl for Simple0ArgsScalarUDF {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         &self.name
     }
@@ -511,10 +506,6 @@ impl AddIndexToStringVolatileScalarUDF {
 }
 
 impl ScalarUDFImpl for AddIndexToStringVolatileScalarUDF {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         &self.name
     }
@@ -678,9 +669,6 @@ impl CastToI64UDF {
 }
 
 impl ScalarUDFImpl for CastToI64UDF {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
     fn name(&self) -> &str {
         "cast_to_i64"
     }
@@ -800,9 +788,6 @@ impl TakeUDF {
 
 /// Implement a ScalarUDFImpl whose return type is a function of the input values
 impl ScalarUDFImpl for TakeUDF {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
     fn name(&self) -> &str {
         "take"
     }
@@ -949,10 +934,6 @@ struct ScalarFunctionWrapper {
 }
 
 impl ScalarUDFImpl for ScalarFunctionWrapper {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         &self.name
     }
@@ -1441,10 +1422,6 @@ impl MyRegexUdf {
 }
 
 impl ScalarUDFImpl for MyRegexUdf {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         "regex_udf"
     }
@@ -1609,10 +1586,6 @@ impl MetadataBasedUdf {
 }
 
 impl ScalarUDFImpl for MetadataBasedUdf {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         &self.name
     }
@@ -1818,10 +1791,6 @@ impl Default for ExtensionBasedUdf {
     }
 }
 impl ScalarUDFImpl for ExtensionBasedUdf {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         &self.name
     }
@@ -1988,9 +1957,6 @@ async fn test_config_options_work_for_scalar_func() -> Result<()> {
     }
 
     impl ScalarUDFImpl for TestScalarUDF {
-        fn as_any(&self) -> &dyn Any {
-            self
-        }
         fn name(&self) -> &str {
             "TestScalarUDF"
         }
@@ -2052,10 +2018,6 @@ async fn test_extension_metadata_preserve_in_sql_values() -> Result<()> {
     }
 
     impl ScalarUDFImpl for MakeExtension {
-        fn as_any(&self) -> &dyn Any {
-            self
-        }
-
         fn name(&self) -> &str {
             "make_extension"
         }
@@ -2133,10 +2095,6 @@ async fn test_extension_metadata_preserve_in_subquery() -> Result<()> {
     }
 
     impl ScalarUDFImpl for ExtensionScalarPredicate {
-        fn as_any(&self) -> &dyn Any {
-            self
-        }
-
         fn name(&self) -> &str {
             "extension_predicate"
         }

datafusion/expr/src/async_udf.rs

@@ -63,7 +63,7 @@ impl PartialEq for AsyncScalarUDF {
     fn eq(&self, other: &Self) -> bool {
         // Deconstruct to catch any new fields added in future
         let Self { inner } = self;
-        inner.dyn_eq(other.inner.as_any())
+        inner.as_ref().dyn_eq(other.inner.as_ref() as &dyn Any)
     }
 }
 impl Eq for AsyncScalarUDF {}
@@ -102,10 +102,6 @@ impl AsyncScalarUDF {
 }
 
 impl ScalarUDFImpl for AsyncScalarUDF {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
     fn name(&self) -> &str {
         self.inner.name()
     }
@@ -156,10 +152,6 @@ mod tests {
     }
 
     impl ScalarUDFImpl for TestAsyncUDFImpl1 {
-        fn as_any(&self) -> &dyn std::any::Any {
-            self
-        }
-
         fn name(&self) -> &str {
             todo!()
         }
@@ -193,10 +185,6 @@ mod tests {
     }
 
     impl ScalarUDFImpl for TestAsyncUDFImpl2 {
-        fn as_any(&self) -> &dyn std::any::Any {
-            self
-        }
-
         fn name(&self) -> &str {
             todo!()
         }