Add test to check correctness of undefined case.

Author: cristianoc

tests/tests/src/pattern_match_json.mjs

@@ -1,9 +1,10 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 
+import * as Primitive_option from "rescript/lib/es6/Primitive_option.js";
 
 function decodeGroup(group) {
   let id = group.id;
-  if (id === null) {
+  if (id == null) {
     return [
       "e",
       "f"
@@ -38,8 +39,22 @@ function decodeNull(x) {
   }
 }
 
+function decodeUndefined(x) {
+  let match = x.field;
+  if (match === undefined) {
+    return "no";
+  }
+  let tmp = Primitive_option.valFromOption(match);
+  if (tmp === undefined) {
+    return "yes it's undefined";
+  } else {
+    return "no";
+  }
+}
+
 export {
   decodeGroup,
   decodeNull,
+  decodeUndefined,
 }
 /* No side effect */

tests/tests/src/pattern_match_json.res

@@ -2,6 +2,7 @@
 type rec t =
   | Boolean(bool)
   | @as(null) Null
+  | @as(undefined) Undefined
   | String(string)
   | Number(float)
   | Object(Dict.t<t>)
@@ -24,3 +25,9 @@ let decodeNull = x =>
   | dict{"field": Null} => "yes it's null"
   | _ => "no"
   }
+
+let decodeUndefined = x =>
+  switch x {
+  | dict{"field": Undefined} => "yes it's undefined"
+  | _ => "no"
+  }