foo1.cs

    [Pure]
    private static bool HasContainingUnclosedBlocks([NotNull] ILocalFunctionDeclaration localFunctionDeclaration)
    {
      foreach (var containingNode in localFunctionDeclaration.ContainingNodes())
      {
        var containingBlock = containingNode as IBlock;
        if (containingBlock != null && containingBlock.RBrace == null) return true;

        var switchBlock = containingNode as ISwitchBlock;
        if (switchBlock != null && switchBlock.RBrace == null) return true;

        var classBody = containingNode as IClassBody;
        if (classBody != null && classBody.RBrace == null) return true;

        var namespaceBody = containingNode as INamespaceBody;
        if (namespaceBody != null && namespaceBody.RBrace == null) return true;
      }

      return false;
    }

foo2.cs

    [Pure]
    private static bool HasContainingUnclosedBlocks([NotNull] ILocalFunctionDeclaration localFunctionDeclaration)
    {
      foreach (var containingNode in localFunctionDeclaration.ContainingNodes())
      {
        switch (containingNode)
        {
          case IBlock block                 when block.RBrace == null:
          case ISwitchBlock switchBlock     when switchBlock.RBrace == null:
          case IClassBody classBody         when classBody.RBrace == null:
          case INamespaceBody namespaceBody when namespaceBody.RBrace == null:
            return true;
        }
      }

      return false;
    }