go/types: add Scope.Elements iterator

// This program demonstrates how to iterate over the objects in a
// types.Scope in Go 1.27.1, where the proposed Objects() iterator
// is not yet available. It parses a small Go source file, builds
// its type information, and then walks the package scope printing
// each object's name and kind.
//
// In a future release that includes the change, the loop could be
// simplified to:
//   for obj := range pkg.Scope().Objects() { ... }
package main

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"go/types"
)

func main() {
	// Create a file set and parse a tiny Go source snippet.
	fset := token.NewFileSet()
	src := `package main
func foo() {}
var x int`
	file, err := parser.ParseFile(fset, "example.go", src, 0)
	if err != nil {
		panic(err)
	}

	// Set up type checking for the file.
	conf := types.Config{Importer: nil}
	info := &types.Info{Defs: make(map[*ast.Ident]types.Object)}
	pkg, err := conf.Check("example", fset, []*ast.File{file}, info)
	if err != nil {
		panic(err)
	}

	// Iterate over the package scope using the existing API.
	s := pkg.Scope()
	for _, name := range s.Names() {
		obj := s.Lookup(name)
		fmt.Printf("%s: %s\n", name, obj.Type())
	}
}