Incorrect parsing of array subscripts

[davidchisnall]

Using this rego module, patched to import rego.v1 instead of future.keywords.every (which seems to be failing since the last rego-cpp update), we see this error:

Invalid reference bracket expression
-- ../../network_stack.rego:44:40
		"connection_type":  connection_types[connectionType],
                                       ~~~~~~~~~~~~~~

-- 
wellformed_error
~~~~~~~~~~~~~~~~

Pass expr_to_opblock failed with 1 error!

Storing the array index expression in a temporary seems to fix it:

@@ -38,9 +38,12 @@ decode_connection_capability(connection) = decoded {
        host = string_from_hex_string(connection.contents, 8)
        count(host)+1 == hostLength
 
+       some connectionTypeName
+       connectionTypeName = connection_types[connectionType]
+
        decoded = {
                "port": port,
-               "connection_type":  connection_types[connectionType],
+               "connection_type":  connectionTypeName,
                "host": host
        }
 }

So it appears to be a parsing error. This was working in pre 1.0 versions. We're currently on 1.0.1, but moving to 1.4.1 does not fix the issue.