golang a 代码
文件路径：/test/fixedbugs/bug480.dir/a.go
/ Copyright 2013 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package a
type S interface{
F() T
}
type T struct {
S
}
type U struct {
error
}