fix: improve Context::add_variable Err type (#127)

Author: michaelbeaumont

interpreter/src/context.rs

@@ -45,7 +45,7 @@ impl Context<'_> {
         &mut self,
         name: S,
         value: V,
-    ) -> Result<(), Box<dyn std::error::Error>>
+    ) -> Result<(), <V as TryIntoValue>::Error>
     where
         S: Into<String>,
         V: TryIntoValue,

interpreter/src/objects.rs

@@ -136,7 +136,7 @@ impl<K: Into<Key>, V: Into<Value>> From<HashMap<K, V>> for Map {
 }
 
 pub trait TryIntoValue {
-    type Error: std::error::Error + 'static;
+    type Error: std::error::Error + 'static + Send + Sync;
     fn try_into_value(self) -> Result<Value, Self::Error>;
 }