if (!result.use_empty()) return false;

  Block& body_block = while_op.getBody().front();
  Block& cond_block = while_op.getCond().front();
  Operation* body_yield_op = body_block.getTerminator();

  // The body yield operand, body block argument, condition block argument, and
  // result all correspond to each other (see definition of `WhileRegionOp`).
  int idx = result.getResultNumber();

    // match the "func.return" within the function.
    //
    // So this would transform
    // func.func @f(...) -> ... {
    //     yield %x : foo
    // }
    // ...
    // func.call @f(...) -> bar
    //
    // to
    //
    // func.func @f(...) -> ... {
    //     yield %x : foo
    // }
    // ...
    // func.call f(...) -> foo
    auto symbol_uses = f.getSymbolUses(f->getParentOp());

//
// For greater control over the traversal of each subtree, use [Inspect].
func Preorder(root Node) iter.Seq[Node] {
	return func(yield func(Node) bool) {
		ok := true
		Inspect(root, func(n Node) bool {
			if n != nil {
				// yield must not be called once ok is false.
				ok = ok && yield(n)
			}
			return ok
		})
	}

    我们将`SessionLocal()`请求的创建和处理放在一个`try`块中。

    然后我们在finally块中关闭它。

    通过这种方式，我们确保数据库会话在请求后始终关闭。即使在处理请求时出现异常。

    但是您不能从退出代码中引发另一个异常（在yield之后）。可以查阅 [Dependencies with yield and HTTPException](https://fastapi.tiangolo.com/zh/tutorial/dependencies/dependencies-with-yield/#dependencies-with-yield-and-httpexception)

*然后，当在路径操作函数*中使用依赖项时，我们使用`Session`，直接从 SQLAlchemy 导入的类型声明它。

*这将为我们在路径操作函数*中提供更好的编辑器支持，因为编辑器将知道`db`参数的类型`Session`：

    static_dir: Path = Path(os.getcwd()) / "static"
    print(static_dir)
    static_dir.mkdir(exist_ok=True)
    from docs_src.custom_docs_ui.tutorial002 import app

    with TestClient(app) as client:
        yield client
    static_dir.rmdir()


def test_swagger_ui_html(client: TestClient):
    response = client.get("/docs")
    assert response.status_code == 200, response.text

					if b['tophash'][i] != 0:
						k = b['keys'][i]
						v = b['values'][i]
						if flags & 1:
							k = k.dereference()
						if flags & 2:
							v = v.dereference()
						yield str(cnt), k
						yield str(cnt + 1), v
						cnt += 2
				bp = b['overflow']


class ChanTypePrinter:
	"""Pretty print chan[T] types.

	Chan-typed go variables are really pointers. dereference them in gdb

)

// Readdir reads the contents of the directory associated with file and
// returns a slice of up to n [FileInfo] values, as would be returned
// by [Lstat], in directory order. Subsequent calls on the same file will yield
// further FileInfos.
//
// If n > 0, Readdir returns at most n FileInfo structures. In this case, if
// Readdir returns an empty slice, it will return a non-nil error

	file := fset.AddFile("", fset.Base(), len(src)) // register input "file"
	s.Init(file, src, nil /* no error handler */, scanner.ScanComments)

	// Repeated calls to Scan yield the token sequence found in the input.
	for {
		pos, tok, lit := s.Scan()
		if tok == token.EOF {
			break
		}
		fmt.Printf("%s\t%s\t%q\n", fset.Position(pos), tok, lit)
	}

	// output:
	// 1:1	IDENT	"cos"

For example:

```mlir
"tf.IfRegion"(%0) ( {
  %2 = "tf.A"() : () -> (tensor<f32>)
  "tf.Yield"() : () -> ()
  }, {
  "tf.Yield"() : () -> ()
 }) { is_stateless = true } : (tensor<i1>) -> ()
"tf.IfRegion"(%0) ( {
  %2 = "tf.B"() : () -> (tensor<f32>)
  "tf.Yield"() : () -> ()
  }, {
  "tf.Yield"() : () -> ()
  }) { is_stateless = true } : (tensor<i1>) -> ()
```

Would be transformed to:

  // CHECK:   %[[MUL:.*]] = "tf.Mul"(%[[ARG0]], %[[ARG1]])
  // CHECK:   "tf.Yield"(%[[MUL]]) : (tensor<f32>)
  // CHECK:  },  {
  // CHECK:    %[[SUB:.*]] = "tf.Sub"(%[[ARG0]], %[[ARG1]])
  // CHECK:    "tf.Yield"(%[[SUB]]) : (tensor<f32>)
  // CHECK:  },  {
  // CHECK:    %[[ADD:.*]] = "tf.AddV2"(%[[ARG0]], %[[ARG1]])
  // CHECK:    "tf.Yield"(%[[ADD]]) : (tensor<f32>)