test: promote test failure

test/class_types_3_dot_8.t/input.re

@@ -0,0 +1,41 @@
+/* Copyright (c) 2015-present, Facebook, Inc. All rights reserved. */
+
+[@reason.version 3.8];
+
+class type _module ('provider_impl) = {
+
+};
+type t;
+class type bzz = {
+  inherit _module(t)
+};
+
+class type t = { as 'a;
+  constraint 'a = #s
+};
+
+/* https://github.com/facebook/reason/issues/2037 */
+class type xt = { as 'a };
+
+class x = {
+  as self
+};
+
+class type classWithNoArgType {
+  pub x : int;
+  pub y : int
+};
+
+class classWithNoArg {
+  pub x = 0;
+  pub y = 0
+};
+
+class type t = {
+  open M;
+  as 'a;
+};
+
+class type t = {
+  open M;
+};

test/class_types_3_dot_8.t/run.t

@@ -0,0 +1,18 @@
+
+Format basic
+  $ refmt --print re ./input.re > ./formatted.re
+
+Type-check basics
+  $ ocamlc -c -pp 'refmt --print binary' -intf-suffix .rei -impl formatted.re
+  File "formatted.re", line 13, characters 19-20:
+  13 |   constraint 'a = #s;
+                          ^
+  Error: Unbound class type s
+  [2]
+
+Format the formatted file back
+  $ refmt --print re ./formatted.re > ./formatted_back.re
+
+Ensure idempotency: first format and second format are the same
+  $ diff formatted.re formatted_back.re
+