final version with Arc<Mutex<Object>>

src/function.rs

@@ -5,7 +5,7 @@ use crate::{Type, Object, Value};
 
 use std::collections::HashMap;
 use std::fmt::{self, Display};
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 
 #[derive(Clone, Debug, PartialEq)]
 pub struct FunctionType(pub Box<Type>, pub Vec<Type>);
@@ -52,8 +52,8 @@ impl Function {
 	}
 
 	pub(crate) fn call(&mut self,
-                mut globals: HashMap<String, Arc<RefCell<Object>>>,
-                locals: HashMap<String, Arc<RefCell<Object>>>,
+                mut globals: HashMap<String, Arc<Mutex<Object>>>,
+                locals: HashMap<String, Arc<Mutex<Object>>>,
                 args: Vec<Object>) -> Result<Value, RuntimeError>
     {
         let mut tree = vec![Ok(*self.body.clone())].into_iter();
@@ -63,11 +63,11 @@ impl Function {
             .locals(locals.clone());
 
         for (obj, name) in std::iter::zip(args.into_iter(), self.arg_names.clone().into_iter()) {
-            exec = exec.add_local(name.clone(), Arc::new(RefCell::new(obj)));
+            exec = exec.add_local(name.clone(), Arc::new(Mutex::new(obj)));
         }
 
         if let Some(name) = self.name().map(|x| x.to_string()) {
-            exec = exec.add_local(name, Arc::new(RefCell::new(Object::function(self.clone(), g, locals))));
+            exec = exec.add_local(name, Arc::new(Mutex::new(Object::function(self.clone(), g, locals))));
         }
 
         exec.next().unwrap()