Function ExampleInfo

types/example_test.go:114–220

ExampleInfo prints various facts recorded by the type checker in a types.Info struct: definitions of and references to each named object, and the type, value, and mode of every expression in the package.

()

// types.Info struct: definitions of and references to each named object,
// and the type, value, and mode of every expression in the package.
func ExampleInfo() {
	// Parse a single source file.
	const input = `
package fib

type S string

var a, b, c = len(b), S(c), "hello"

func fib(x int) int {
	if x < 2 {
		return x
	}
	return fib(x-1) - fib(x-2)
}`
	f, err := parseSrc("fib.go", input)
	if err != nil {
		log.Fatal(err)
	}

	// Type-check the package.
	// We create an empty map for each kind of input
	// we're interested in, and Check populates them.
	info := types.Info{
		Types: make(map[Expr]types.TypeAndValue),
		Defs:  make(map[*Name]types.Object),
		Uses:  make(map[*Name]types.Object),
	}
	var conf types.Config
	pkg, err := conf.Check("fib", []*File{f}, &info)
	if err != nil {
		log.Fatal(err)
	}

	// Print package-level variables in initialization order.
	fmt.Printf("InitOrder: %v\n\n", info.InitOrder)

	// For each named object, print the line and
	// column of its definition and each of its uses.
	fmt.Println("Defs and Uses of each named object:")
	usesByObj := make(map[types.Object][]string)
	for id, obj := range info.Uses {
		posn := id.Pos()
		lineCol := fmt.Sprintf("%d:%d", posn.Line(), posn.Col())
		usesByObj[obj] = append(usesByObj[obj], lineCol)
	}
	var items []string
	for obj, uses := range usesByObj {
		sort.Strings(uses)
		item := fmt.Sprintf("%s:\n  defined at %s\n  used at %s",
			types.ObjectString(obj, types.RelativeTo(pkg)),
			obj.Pos(),
			strings.Join(uses, ", "))
		items = append(items, item)
	}
	sort.Strings(items) // sort by line:col, in effect
	fmt.Println(strings.Join(items, "\n"))
	fmt.Println()