from typing import List, Dict, Any, Optional
from dataclasses import dataclass, asdict


@dataclass
class Token:
    type: str
    value: Any


@dataclass
class Operation:
    function: str
    type: str
    value: Any


@dataclass
class StackItem:
    type: str
    value: Any


@dataclass
class RuntimeError:
    message: str


@dataclass
class TestCase:
    name: str
    code: str
    tokens: List[Dict[str, Any]]
    operations: Optional[List[Dict[str, Any]]] = None
    stack_final: Optional[List[Dict[str, Any]]] = None
    runtime_error: Optional[Dict[str, str]] = None


def to_dict(obj):
    """Convert dataclass to dict, removing None values."""
    if obj is None:
        return None
    d = asdict(obj) if hasattr(obj, '__dataclass_fields__') else obj
    return {k: v for k, v in d.items() if v is not None}