foo1.cs

[NotNull, Pure]
public static IPattern UnwrapFromSandbox([NotNull] this IPattern pattern)
{
  if (pattern.Parent is ISandBox sandBox
      && sandBox.ContextType == SandBoxContextType.Replace
      && sandBox.ContextNode is IPattern replacedPattern)
  {
    return replacedPattern;
  }

  return pattern;
}

foo2.cs

[NotNull, Pure]
public static IPattern UnwrapFromSandbox([NotNull] this IPattern pattern)
{
  if (pattern.Parent is ISandBox {
        ContextType: SandBoxContextType.Replace,
        ContextNode: IPattern replacedPattern })
  {
    return replacedPattern;
  }

  return pattern;
}

foo3.cs

[NotNull, Pure]
public static IPattern UnwrapFromSandbox([NotNull] this IPattern pattern)
{
  if (pattern is {
        Parent: ISandBox {
          ContextType: SandBoxContextType.Replace,
          ContextNode: IPattern replacedPattern } })
  {
    return replacedPattern;
  }

  return pattern;
}