// If addPosition is true, add position info in the ident name.
func (p *Package) rewriteName(f *File, r *Ref, addPosition bool) ast.Expr {
	getNewIdent := ast.NewIdent
	if addPosition {
		getNewIdent = func(newName string) *ast.Ident {
			mangledIdent := ast.NewIdent(newName)
			if len(newName) == len(r.Name.Go) {
				return mangledIdent
			}
			p := fset.Position((*r.Expr).End())