add test for #6493

tests/unit/src/unit/TestJson.hx

@@ -88,6 +88,7 @@ class TestJson extends Test {
 		deepId( {array: mix} );
 
 		eq( haxe.format.JsonParser.parse('"\\u00E9"'), "é" );
+		exc(() -> haxe.format.JsonParser.parse('{"""a": 1}'));
 
 		eq(haxe.format.JsonPrinter.print(Math.POSITIVE_INFINITY), "null");
 		eq(haxe.format.JsonPrinter.print(Math.NEGATIVE_INFINITY), "null");