add tests

Author: aspeddro

test/corpus/type_declarations.txt

@@ -530,6 +530,7 @@ Type constraint
 
 type t<'a> = 'a constraint 'a = int
 type decorator<'a, 'b> = 'a => 'b constraint 'a = int constraint 'b = _ => _
+type t<'a> constraint 'a = t
 
 ---
 
@@ -553,4 +554,11 @@ type decorator<'a, 'b> = 'a => 'b constraint 'a = int constraint 'b = _ => _
       (type_identifier)
       (function_type
         (function_type_parameters (type_identifier))
-        (type_identifier)))))
+        (type_identifier))))
+
+  (type_declaration
+    (type_identifier)
+    (type_parameters (type_identifier))
+    (type_constraint
+      (type_identifier)
+      (type_identifier))))