Array mapping fails

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Current behavior (how does the issue manifest): It seems that mapping with arrays fails when using it in branches or functions

Using in a branch

2018-05-23 19:57:16.474 ERROR  [linker] - Get value from link value %+v, error %s$flow.commandline[0] == "type"Execution failed for mapping [$flow.commandline[0] == "type"] due to error - Mapping ref eva error [not an array]

The input for the array

{
                  "mapTo": "commandline",
                  "type": "assign",
                  "value": "$.args"
                }

The commandline is mapped from the args coming from the cli trigger

The link expression

{
            "from": "log_2",
            "to": "log_5",
            "type": "expression",
            "value": "$flow.commandline[0] == \"type\""
          }

Using in a function

This mapping

{
"type": "expression",
"value": "string.concat(\"Your search parameters are \", $flow.commandline[0], \" - \", $flow.commandline[1], \" - \", $flow.commandline[2], \" - \", $flow.commandline[3])",
"mapTo": "message"
}

results in this error

Expression mapping failed, due to Execution failed for mapping [string.concat("Your search parameters are ", $flow.commandline[0], " - ", $flow.commandline[1], " - ", $flow.commandline[2], " - ", $flow.commandline[3])] due to error - not an array
2018-05-23 20:14:35.615 ERROR  [flowmodel-simple] - Error evaluating activity 'log_2'[github.com/TIBCOSoftware/flogo-contrib/activity/log] - Expression mapping failed, due to Execution failed for mapping [string.concat("Your search parameters are ", $flow.commandline[0], " - ", $flow.commandline[1], " - ", $flow.commandline[2], " - ", $flow.commandline[3])] due to error - not an array

I'm very sure that $flow.commandline is an array because when I try to use it without any qualifiers in my mapping I get the error

 Expression mapping failed, due to Execution failed for mapping [string.concat("Your search parameters are ", $flow.commandline)] due to error - reflect: cannot use []string as type string in Call