Workaround an issue preventing users to catch errors from

modules/standard/JSON.chpl

@@ -1185,7 +1185,12 @@ module JSON {
   proc fromJson(jsonString: string, type loadAs): loadAs throws {
     var fileReader = openStringReader(jsonString,
                                       deserializer=new jsonDeserializer());
-    return fileReader.read(loadAs);
+    // we want `return fileReader.read(loadAs)`. But that ends up using a
+    // non-throwing compiler-generated initializer. That prevents the user to
+    // catch errors that are due to malformed jsonString.
+    var ret: loadAs;
+    fileReader.read(ret);
+    return ret;
   }
 
   /* Given a Chapel value, serialize it into a JSON string using the

test/io/serializers/jsonHelpers/fromJsonThrows.chpl

@@ -0,0 +1,20 @@
+import IO, JSON;
+
+record myRec {
+  var field: int;
+}
+
+var inFile = IO.open("fromJsonThrows.in", IO.ioMode.r);
+var inReader = inFile.reader();
+
+var rec: myRec;
+
+proc main() throws {
+  try {
+    rec = JSON.fromJson(inReader.readAll(string), myRec);
+    writeln(rec);
+  }
+  catch err: IllegalArgumentError {
+    writeln("Caught the error correctly");
+  }
+}

test/io/serializers/jsonHelpers/fromJsonThrows.cleanfiles

@@ -0,0 +1 @@
+fromJsonThrows.in

test/io/serializers/jsonHelpers/fromJsonThrows.good

@@ -0,0 +1 @@
+Caught the error correctly

test/io/serializers/jsonHelpers/fromJsonThrows.preexec

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+echo "{\"fiel\":10}" > fromJsonThrows.in