Add positional_count field to Lambda

This field is used for static optimization, determining if parameters
are purely positional.

src/ast/environment.rs

@@ -231,15 +231,24 @@ impl Environment {
     /// Runtime: Execute the linked AST in the VM
     pub fn run(&self, node: &TypedNode) -> Result<Value, String> {
         let mut vm = VM::new(self.global_values.clone());
-        let result = vm.run(node)?;
+        let mut result = vm.run(node)?;
         
+        // Handle potential script body closure
         if let Value::Object(obj) = &result 
             && let Some(closure) = obj.as_any().downcast_ref::<crate::ast::vm::Closure>() 
         {
-            // Execute the script body
-            return vm.run(&closure.function_node);
+            result = vm.run(&closure.function_node)?;
+        }
+
+        // IMPORTANT: Resolve any pending tail call requests from the top-level execution
+        while let Value::TailCallRequest(payload) = result {
+            let (next_obj, next_args) = *payload;
+            if let Some(closure) = next_obj.as_any().downcast_ref::<crate::ast::vm::Closure>() {
+                result = vm.run_with_args(closure, next_args)?;
+            } else {
+                return Err(format!("Tail call target is not a closure: {}", next_obj.type_name()));
+            }
         }
-        
         Ok(result)
     }
 
@@ -273,6 +282,17 @@ impl Environment {
             result = vm.run_with_observer(&mut observer, &closure.function_node);
         }
 
+        // Resolve top-level tail calls
+        while let Ok(Value::TailCallRequest(payload)) = result {
+            let (next_obj, next_args) = *payload;
+            if let Some(closure) = next_obj.as_any().downcast_ref::<crate::ast::vm::Closure>() {
+                result = vm.run_with_args_observed(&mut observer, closure, next_args);
+            } else {
+                result = Err(format!("Tail call target is not a closure: {}", next_obj.type_name()));
+                break;
+            }
+        }
+
         Ok((result, observer.logs))
     }
 }