"fmt"
	"go/build"
	"internal/godebugs"
	"sort"
	"strconv"
	"strings"

	"cmd/go/internal/gover"
	"cmd/go/internal/modload"
)

var ErrNotGoDebug = errors.New("not //go:debug line")

func ParseGoDebug(text string) (key, value string, err error) {
	if !strings.HasPrefix(text, "//go:debug") {
		return "", "", ErrNotGoDebug
	}
	i := strings.IndexAny(text, " \t")
	if i < 0 {

	seen := make(map[string]bool)
	// apply environment settings
	parsegodebug(env, seen)
	// apply compile-time GODEBUG settings for as-yet-unseen variables
	parsegodebug(godebugDefault, seen)
	// apply defaults for as-yet-unseen variables
	for _, v := range dbgvars {
		if v.atomic != nil && !seen[v.name] {
			v.atomic.Store(0)
		}
	}
}

// parsegodebug parses the godebug string, updating variables listed in dbgvars.

	var msg []byte
	p := a.Package
	var seen map[string]token.Position
	for _, d := range p.Internal.Build.Directives {
		if strings.HasPrefix(d.Text, "//go:debug") {
			key, _, err := load.ParseGoDebug(d.Text)
			if err != nil && err != load.ErrNotGoDebug {
				msg = fmt.Appendf(msg, "%s: invalid //go:debug: %v\n", d.Pos, err)
				continue
			}
			if pos, ok := seen[key]; ok {