Resolver - Fixed function handling

* Since the arguments are stored in an intermediate environment, an
    additional scope is required

src/resolver.rs

@@ -68,8 +68,12 @@ impl ResolverState {
             self.declare(param);
             self.define(param);
         }
+        // Unlike the original Lox, function arguments and function bodies do
+        // not use the same environment.
+        self.begin_scope();
         let result = body.resolve(self);
         self.end_scope();
+        self.end_scope();
         result
     }