Move Default trait to where it's needed

Author: mlafeldt

crates/duckdb/src/r2d2.rs

@@ -92,7 +92,7 @@ impl DuckdbConnectionManager {
     #[cfg(feature = "vscalar")]
     pub fn register_scalar_function<S: VScalar>(&self, name: &str) -> Result<()>
     where
-        S::State: Debug,
+        S::State: Debug + Default,
     {
         let conn = self.connection.lock().unwrap();
         conn.register_scalar_function::<S>(name)

crates/duckdb/src/vscalar/mod.rs

@@ -25,7 +25,7 @@ pub use arrow::{ArrowFunctionSignature, ArrowScalarParams, VArrowScalar};
 pub trait VScalar: Sized {
     /// State that persists across invocations of the scalar function (the lifetime of the connection)
     /// The state can be accessed by multiple threads, so it must be `Send + Sync`.
-    type State: Default + Sized + Send + Sync;
+    type State: Sized + Send + Sync;
     /// The actual function
     ///
     /// # Safety
@@ -134,7 +134,10 @@ where
 impl Connection {
     /// Register the given ScalarFunction with default state
     #[inline]
-    pub fn register_scalar_function<S: VScalar>(&self, name: &str) -> crate::Result<()> {
+    pub fn register_scalar_function<S: VScalar>(&self, name: &str) -> crate::Result<()>
+    where
+        S::State: Default,
+    {
         let set = ScalarFunctionSet::new(name);
         for signature in S::signatures() {
             let scalar_function = ScalarFunction::new(name)?;