/*
func dump(msg string, val reflect.Value) {
	fmt.Printf("%s:\n", msg)
	ast.Print(fileSet, val.Interface())
	fmt.Println()
}
*/

// rewriteFile applies the rewrite rule 'pattern -> replace' to an entire file.
func rewriteFile(fileSet *token.FileSet, pattern, replace ast.Expr, p *ast.File) *ast.File {
	cmap := ast.NewCommentMap(fileSet, p, p.Comments)
	m := make(map[string]reflect.Value)