return err
	}

	r := &Retract{
		VersionInterval: vi,
	}
	if vi.Low == vi.High {
		r.Syntax = f.Syntax.addLine(nil, "retract", AutoQuote(vi.Low))
	} else {
		r.Syntax = f.Syntax.addLine(nil, "retract", "[", AutoQuote(vi.Low), ",", AutoQuote(vi.High), "]")
	}
	if rationale != "" {
		for _, line := range strings.Split(rationale, "\n") {
			com := Comment{Token: "// " + line}

				f.Syntax.updateLine(d.Syntax, "use", AutoQuote(diskPath))
				need = false
			} else {
				d.Syntax.markRemoved()
				*d = Use{}
			}
		}
	}

	if need {
		f.AddNewUse(diskPath, modulePath)
	}
	return nil
}

func (f *WorkFile) AddNewUse(diskPath, modulePath string) {
	line := f.Syntax.addLine(nil, "use", AutoQuote(diskPath))

// for dependencies in the middle of a build, impossible to
// correct. So we stopped.
func LegacyGoMod(modPath string) []byte {
	return fmt.Appendf(nil, "module %s\n", modfile.AutoQuote(modPath))
}

func (r *codeRepo) modPrefix(rev string) string {
	return r.modPath + "@" + rev
}

func (r *codeRepo) retractedVersions(ctx context.Context) (func(string) bool, error) {