DSL EXPRESSION:
$[2] = 3


AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "$[]" [tt:$[]] [nt:IndirectFieldValue]
            "2" [tt:int_literal] [nt:int_literal]
        "3" [tt:int_literal] [nt:int_literal]

