remove SessionVar blanket impl, replace with type impls (#7695)

The blanket impl is a bit of a footgun, replace with impls for each of
the session extension types

See discussion in
#7693 (comment)

---------

Signed-off-by: Andrew Duffy <andrew@a10y.dev>

Author: a10y

vortex-array/public-api.lock

@@ -762,6 +762,12 @@ impl core::fmt::Debug for vortex_array::aggregate_fn::session::AggregateFnSessio
 
 pub fn vortex_array::aggregate_fn::session::AggregateFnSession::fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result
 
+impl vortex_session::SessionVar for vortex_array::aggregate_fn::session::AggregateFnSession
+
+pub fn vortex_array::aggregate_fn::session::AggregateFnSession::as_any(&self) -> &dyn core::any::Any
+
+pub fn vortex_array::aggregate_fn::session::AggregateFnSession::as_any_mut(&mut self) -> &mut dyn core::any::Any
+
 pub trait vortex_array::aggregate_fn::session::AggregateFnSessionExt: vortex_session::SessionExt
 
 pub fn vortex_array::aggregate_fn::session::AggregateFnSessionExt::aggregate_fns(&self) -> vortex_session::Ref<'_, vortex_array::aggregate_fn::session::AggregateFnSession>
@@ -9044,6 +9050,12 @@ impl core::fmt::Debug for vortex_array::dtype::session::DTypeSession
 
 pub fn vortex_array::dtype::session::DTypeSession::fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result
 
+impl vortex_session::SessionVar for vortex_array::dtype::session::DTypeSession
+
+pub fn vortex_array::dtype::session::DTypeSession::as_any(&self) -> &dyn core::any::Any
+
+pub fn vortex_array::dtype::session::DTypeSession::as_any_mut(&mut self) -> &mut dyn core::any::Any
+
 pub trait vortex_array::dtype::session::DTypeSessionExt: vortex_session::SessionExt
 
 pub fn vortex_array::dtype::session::DTypeSessionExt::dtypes(&self) -> vortex_session::Ref<'_, vortex_array::dtype::session::DTypeSession>
@@ -13374,6 +13386,12 @@ impl core::fmt::Debug for vortex_array::memory::MemorySession
 
 pub fn vortex_array::memory::MemorySession::fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result
 
+impl vortex_session::SessionVar for vortex_array::memory::MemorySession
+
+pub fn vortex_array::memory::MemorySession::as_any(&self) -> &dyn core::any::Any
+
+pub fn vortex_array::memory::MemorySession::as_any_mut(&mut self) -> &mut dyn core::any::Any
+
 pub struct vortex_array::memory::WritableHostBuffer
 
 impl vortex_array::memory::WritableHostBuffer
@@ -13480,6 +13498,12 @@ impl core::fmt::Debug for vortex_array::optimizer::kernels::ArrayKernels
 
 pub fn vortex_array::optimizer::kernels::ArrayKernels::fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result
 
+impl vortex_session::SessionVar for vortex_array::optimizer::kernels::ArrayKernels
+
+pub fn vortex_array::optimizer::kernels::ArrayKernels::as_any(&self) -> &dyn core::any::Any
+
+pub fn vortex_array::optimizer::kernels::ArrayKernels::as_any_mut(&mut self) -> &mut dyn core::any::Any
+
 pub trait vortex_array::optimizer::kernels::ArrayKernelsExt: vortex_session::SessionExt
 
 pub fn vortex_array::optimizer::kernels::ArrayKernelsExt::kernels(&self) -> vortex_session::Ref<'_, vortex_array::optimizer::kernels::ArrayKernels>
@@ -17602,6 +17626,12 @@ impl core::fmt::Debug for vortex_array::scalar_fn::session::ScalarFnSession
 
 pub fn vortex_array::scalar_fn::session::ScalarFnSession::fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result
 
+impl vortex_session::SessionVar for vortex_array::scalar_fn::session::ScalarFnSession
+
+pub fn vortex_array::scalar_fn::session::ScalarFnSession::as_any(&self) -> &dyn core::any::Any
+
+pub fn vortex_array::scalar_fn::session::ScalarFnSession::as_any_mut(&mut self) -> &mut dyn core::any::Any
+
 pub trait vortex_array::scalar_fn::session::ScalarFnSessionExt: vortex_session::SessionExt
 
 pub fn vortex_array::scalar_fn::session::ScalarFnSessionExt::scalar_fns(&self) -> vortex_session::Ref<'_, vortex_array::scalar_fn::session::ScalarFnSession>
@@ -19056,6 +19086,12 @@ impl core::fmt::Debug for vortex_array::session::ArraySession
 
 pub fn vortex_array::session::ArraySession::fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result
 
+impl vortex_session::SessionVar for vortex_array::session::ArraySession
+
+pub fn vortex_array::session::ArraySession::as_any(&self) -> &dyn core::any::Any
+
+pub fn vortex_array::session::ArraySession::as_any_mut(&mut self) -> &mut dyn core::any::Any
+
 pub trait vortex_array::session::ArraySessionExt: vortex_session::SessionExt
 
 pub fn vortex_array::session::ArraySessionExt::array_serialize(&self, array: &vortex_array::ArrayRef) -> vortex_error::VortexResult<core::option::Option<alloc::vec::Vec<u8>>>

vortex-array/src/aggregate_fn/session.rs

@@ -1,11 +1,13 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
+use std::any::Any;
 use std::sync::Arc;
 
 use parking_lot::RwLock;
 use vortex_session::Ref;
 use vortex_session::SessionExt;
+use vortex_session::SessionVar;
 use vortex_session::registry::Registry;
 use vortex_utils::aliases::hash_map::HashMap;
 
@@ -42,6 +44,16 @@ pub struct AggregateFnSession {
     pub(super) grouped_kernels: RwLock<HashMap<KernelKey, &'static dyn DynGroupedAggregateKernel>>,
 }
 
+impl SessionVar for AggregateFnSession {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 type KernelKey = (ArrayId, Option<AggregateFnId>);
 
 impl Default for AggregateFnSession {

vortex-array/src/dtype/session.rs

@@ -3,10 +3,12 @@
 
 //! Module for managing extension dtypes in a Vortex session.
 
+use std::any::Any;
 use std::sync::Arc;
 
 use vortex_session::Ref;
 use vortex_session::SessionExt;
+use vortex_session::SessionVar;
 use vortex_session::registry::Registry;
 
 use crate::dtype::extension::ExtDTypePluginRef;
@@ -39,6 +41,16 @@ impl Default for DTypeSession {
     }
 }
 
+impl SessionVar for DTypeSession {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 impl DTypeSession {
     /// Register an extension DType with the Vortex session.
     pub fn register<V: ExtVTable>(&self, vtable: V) {

vortex-array/src/memory.rs

@@ -3,6 +3,7 @@
 
 //! Session-scoped memory allocation for host-side buffers.
 
+use std::any::Any;
 use std::fmt::Debug;
 use std::mem::size_of;
 use std::sync::Arc;
@@ -18,6 +19,7 @@ use vortex_error::vortex_err;
 use vortex_session::Ref;
 use vortex_session::RefMut;
 use vortex_session::SessionExt;
+use vortex_session::SessionVar;
 
 /// Mutable host buffer contract used by [`WritableHostBuffer`].
 pub trait HostBufferMut: Send + 'static {
@@ -199,6 +201,16 @@ impl Default for MemorySession {
     }
 }
 
+impl SessionVar for MemorySession {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 /// Extension trait for accessing session-scoped memory configuration.
 pub trait MemorySessionExt: SessionExt {
     /// Returns the memory session for this execution/session context.

vortex-array/src/optimizer/kernels.rs

@@ -17,6 +17,7 @@
 //! sessions can add it with [`VortexSession::with`](vortex_session::VortexSession::with) or rely
 //! on [`ArrayKernelsExt::kernels`] to insert the default value.
 
+use std::any::Any;
 use std::hash::BuildHasher;
 use std::sync::Arc;
 use std::sync::LazyLock;
@@ -25,6 +26,7 @@ use arc_swap::ArcSwap;
 use vortex_error::VortexResult;
 use vortex_session::Ref;
 use vortex_session::SessionExt;
+use vortex_session::SessionVar;
 use vortex_session::registry::Id;
 use vortex_utils::aliases::DefaultHashBuilder;
 use vortex_utils::aliases::hash_map::HashMap;
@@ -100,6 +102,16 @@ impl ArrayKernels {
     }
 }
 
+impl SessionVar for ArrayKernels {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 /// Extension trait for accessing optimizer kernels from a
 /// [`VortexSession`](vortex_session::VortexSession).
 pub trait ArrayKernelsExt: SessionExt {

vortex-array/src/scalar_fn/session.rs

@@ -1,10 +1,12 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
+use std::any::Any;
 use std::sync::Arc;
 
 use vortex_session::Ref;
 use vortex_session::SessionExt;
+use vortex_session::SessionVar;
 use vortex_session::registry::Registry;
 
 use crate::scalar_fn::ScalarFnPluginRef;
@@ -74,6 +76,16 @@ impl Default for ScalarFnSession {
     }
 }
 
+impl SessionVar for ScalarFnSession {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 /// Extension trait for accessing scalar function session data.
 pub trait ScalarFnSessionExt: SessionExt {
     /// Returns the scalar function vtable registry.

vortex-array/src/session/mod.rs

@@ -1,12 +1,14 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
+use std::any::Any;
 use std::sync::Arc;
 
 use vortex_error::VortexResult;
 use vortex_error::vortex_bail;
 use vortex_session::Ref;
 use vortex_session::SessionExt;
+use vortex_session::SessionVar;
 use vortex_session::registry::Registry;
 
 use crate::ArrayRef;
@@ -85,6 +87,16 @@ impl Default for ArraySession {
     }
 }
 
+impl SessionVar for ArraySession {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 /// Session data for Vortex arrays.
 pub trait ArraySessionExt: SessionExt {
     /// Returns the array encoding registry.

vortex-cuda/src/session.rs

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
+use std::any::Any;
 use std::fmt::Debug;
 use std::sync::Arc;
 
@@ -10,6 +11,7 @@ use vortex::array::VortexSessionExecute;
 use vortex::error::VortexResult;
 use vortex::session::Ref;
 use vortex::session::SessionExt;
+use vortex::session::SessionVar;
 use vortex::utils::aliases::dash_map::DashMap;
 
 use crate::ExportDeviceArray;
@@ -147,6 +149,16 @@ impl Default for CudaSession {
     }
 }
 
+impl SessionVar for CudaSession {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 /// Extension trait for accessing the CUDA session from a Vortex session.
 pub trait CudaSessionExt: SessionExt {
     /// Returns the CUDA session.

vortex-file/src/multi/session.rs

@@ -3,10 +3,12 @@
 
 //! Session extension for multi-file scanning, providing a shared footer cache.
 
+use std::any::Any;
 use std::fmt;
 use std::fmt::Debug;
 
 use vortex_session::SessionExt;
+use vortex_session::SessionVar;
 
 use crate::footer::Footer;
 
@@ -61,6 +63,16 @@ impl MultiFileSession {
     }
 }
 
+impl SessionVar for MultiFileSession {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
 /// Extension trait for accessing the [`MultiFileSession`] from a session.
 pub(super) trait MultiFileSessionExt: SessionExt {
     /// Returns a reference to the [`MultiFileSession`] state.

vortex-io/public-api.lock

@@ -488,6 +488,12 @@ impl core::fmt::Debug for vortex_io::session::RuntimeSession
 
 pub fn vortex_io::session::RuntimeSession::fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result
 
+impl vortex_session::SessionVar for vortex_io::session::RuntimeSession
+
+pub fn vortex_io::session::RuntimeSession::as_any(&self) -> &dyn core::any::Any
+
+pub fn vortex_io::session::RuntimeSession::as_any_mut(&mut self) -> &mut dyn core::any::Any
+
 pub trait vortex_io::session::RuntimeSessionExt: vortex_session::SessionExt
 
 pub fn vortex_io::session::RuntimeSessionExt::handle(&self) -> vortex_io::runtime::Handle