Tweak register_scalar_function_with_state to take reference

Author: mlafeldt

crates/duckdb/src/vscalar/mod.rs

@@ -148,7 +148,7 @@ impl Connection {
 
     /// Register the given ScalarFunction with custom state
     #[inline]
-    pub fn register_scalar_function_with_state<S: VScalar>(&self, name: &str, state: S::State) -> crate::Result<()>
+    pub fn register_scalar_function_with_state<S: VScalar>(&self, name: &str, state: &S::State) -> crate::Result<()>
     where
         S::State: Clone,
     {
@@ -315,7 +315,7 @@ mod test {
         {
             conn.register_scalar_function_with_state::<EchoScalar>(
                 "echo2",
-                TestState {
+                &TestState {
                     multiplier: 5,
                     prefix: "custom".to_string(),
                 },