* **Sự hỗ trợ từ các trình soạn thảo**.
* **Kiểm tra kiểu dữ liệu (type checking)**.

...và **FastAPI** sử dụng các khia báo để:

* **Định nghĩa các yêu cầu**: từ tham số đường dẫn của request, tham số query, headers, bodies, các phụ thuộc (dependencies),...
* **Chuyển dổi dữ liệu*: từ request sang kiểu dữ liệu được yêu cầu.
* **Kiểm tra tính đúng đắn của dữ liệu**: tới từ mỗi request:

// the generated ODCLFUNC, but there is no
// pointer from the Func back to the OMETHVALUE.
type Func struct {
	miniNode
	Body Nodes

	Nname    *Name        // ONAME node
	OClosure *ClosureExpr // OCLOSURE node

	// ONAME nodes for all params/locals for this func/closure, does NOT
	// include closurevars until transforming closures during walk.
	// Names must be listed PPARAMs, PPARAMOUTs, then PAUTOs,

It is designed to have functions that receive two parameters, one "request" and one "response". Then you "read" parts from the request, and "write" parts to the response. Because of this design, it is not possible to declare request parameters and bodies with standard Python type hints as function parameters.

	// We can only be inside one type parameter list at any given time:
	// function closures may appear inside a type parameter list but they
	// cannot be generic, and their bodies are processed in delayed and
	// sequential fashion. Note that with each new declaration, we save
	// the existing environment and restore it when done; thus inTParamList

			assert(rhs != nil)
			alias.fromRHS = rhs
			Unalias(alias) // resolve alias.actual
		} else {
			// With Go1.23, the default behavior is to use Alias nodes,
			// reflected by check.enableAlias. Signal non-default behavior.
			//
			// TODO(gri) Testing runs tests in both modes. Do we need to exclude
			//           tracking of non-default behavior for tests?
			gotypesalias.IncNonDefault()

			if !versionErr && tparam0 != nil {

	RegArgs []Spill
	// OwnAux describes parameters and results for this function.
	OwnAux *AuxCall
	// CloSlot holds the compiler-synthesized name (".closureptr")
	// where we spill the closure pointer for range func bodies.
	CloSlot *ir.Name

	freeValues *Value // free Values linked by argstorage[0].  All other fields except ID are 0/nil.
	freeBlocks *Block // free Blocks linked by succstorage[0].b.  All other fields except ID are 0/nil.

		// afterwards)
	}))
}

func send204(w ResponseWriter, r *Request) { w.WriteHeader(204) }
func send304(w ResponseWriter, r *Request) { w.WriteHeader(304) }

// Issue 15647: 204 responses can't have bodies, so HTTP/1.0 keep-alive conns should stay open.
func TestHTTP10KeepAlive204Response(t *testing.T) {
	testTCPConnectionStaysOpen(t, "GET / HTTP/1.0\r\nConnection: keep-alive\r\n\r\n", HandlerFunc(send204))
}

    // Create the new while operation.
    auto new_while_op = rewriter.create<WhileRegionOp>(
        while_op.getLoc(), new_result_types, new_while_operands,
        while_op->getAttrs());

    // Move region bodies to the new while.
    rewriter.inlineRegionBefore(while_op.getCond(), new_while_op.getCond(),
                                new_while_op.getCond().end());

		// Println etc. set verb to %v, which is "stringable".
		switch verb {
		case 'v', 's', 'x', 'X', 'q':
			// Is it an error or Stringer?
			// The duplication in the bodies is necessary:
			// setting handled and deferring catchPanic
			// must happen before calling the method.
			switch v := p.arg.(type) {
			case error:
				handled = true
				defer p.catchPanic(p.arg, verb, "Error")

		rp.ServeHTTP(w, r)
	}))

	bodyRes := make(chan any, 1) // error or hash.Hash
	pr, pw := io.Pipe()
	req, _ := NewRequest("PUT", proxy.ts.URL, pr)
	const size = 4 << 20
	go func() {
		h := sha1.New()
		_, err := io.CopyN(io.MultiWriter(h, pw), rand.Reader, size)
		go pw.Close()
		if err != nil {
			bodyRes <- err
		} else {
			bodyRes <- h
		}
	}()