Implement IntInst methods

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm.rs

@@ -265,7 +265,9 @@ impl Vm {
         let method_type = self.builtins().get("Method").unwrap().clone();
 
         loop {
-            match self.dispatch() {
+            let op = self.dispatch();
+
+            match op {
                 Op::Pop => {
                     self.pop();
                 }