Update visitor.rs

src/validation/visitor.rs

@@ -376,6 +376,15 @@ fn visit_selection<'a, V: Visitor<'a>>(
                         visit_field(v, ctx, field);
                     },
                 );
+            } else {
+                ctx.report_error(
+                    vec![field.position],
+                    format!(
+                        "Cannot query field \"{}\" on type \"{}\".",
+                        field.name,
+                        ctx.current_type().name()
+                    ),
+                );
             }
         }
         Selection::FragmentSpread(fragment_spread) => {