Allow initialization of EvalState tag and separate debugger state into separate variable.

src/api/run.rs

@@ -26,7 +26,11 @@ impl Engine {
             self.lex_raw(&scripts, self.token_mapper.as_ref().map(Box::as_ref));
         let mut state = ParseState::new(self, scope, tokenizer_control);
 
-        let ast = self.parse(&mut stream.peekable(), &mut state, self.optimization_level)?;
+        let ast = self.parse(
+            &mut stream.peekable(),
+            &mut state,
+            self.optimization_level(),
+        )?;
 
         self.run_ast_with_scope(scope, &ast)
     }