DSL EXPRESSION:
$y ||= $x


AST:
"block" [tt:block] [nt:StatementBlock]
    "||=" [tt:op_or_equals] [nt:CompoundAssignment]
        "$y" [tt:field_name] [nt:DirectFieldValue]
        "||=" [tt:op_or_equals] [nt:op_or_equals]
        "$x" [tt:field_name] [nt:DirectFieldValue]

