add a test case

Author: bobzhang

jscomp/test/gpr_5557.js

@@ -2,7 +2,18 @@
 
 
 function isA(c) {
-  return true;
+  if (c === 97) {
+    return true;
+  }
+  throw {
+        RE_EXN_ID: "Match_failure",
+        _1: [
+          "gpr_5557.res",
+          5,
+          2
+        ],
+        Error: new Error()
+      };
 }
 
 var h = /* 'a' */97;

jscomp/test/gpr_5557.res

@@ -1,3 +1,6 @@
+@@config({
+  flags : ["-w", "-8"]
+})
 let isA = c =>
   switch c {
   | 'a' => true