Rename struct to class per #651 (#765)

executable_semantics/testdata/class_field_missing.carbon

@@ -0,0 +1,12 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+class Point {
+  var x: i32;
+  var y: i32;
+}
+
+fn main() -> i32 {
+  return Point(.x = 1).x - 1;
+}