|  | // run | 
|  |  | 
|  | // Copyright 2009 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 main | 
|  |  | 
|  | type I interface{} | 
|  |  | 
|  | func foo1(i int) int     { return i } | 
|  | func foo2(i int32) int32 { return i } | 
|  | func main() { | 
|  | var i I | 
|  | i = 1 | 
|  | var v1 = i.(int) | 
|  | if foo1(v1) != 1 { | 
|  | panic(1) | 
|  | } | 
|  | var v2 = int32(i.(int)) | 
|  | if foo2(v2) != 1 { | 
|  | panic(2) | 
|  | } | 
|  |  | 
|  | shouldPanic(p1) | 
|  | } | 
|  |  | 
|  | func p1() { | 
|  | var i I | 
|  | i = 1 | 
|  | var v3 = i.(int32) // This type conversion should fail at runtime. | 
|  | if foo2(v3) != 1 { | 
|  | panic(3) | 
|  | } | 
|  | } | 
|  |  | 
|  | func shouldPanic(f func()) { | 
|  | defer func() { | 
|  | if recover() == nil { | 
|  | panic("function should panic") | 
|  | } | 
|  | }() | 
|  | f() | 
|  | } |