go/test/indirect.go

88 строки
1.4 KiB
Go

// 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.
// Test various safe uses of indirection.
package main
var m0 map[string]int
var m1 *map[string]int
var m2 *map[string]int = &m0
var m3 map[string]int = map[string]int{"a": 1}
var m4 *map[string]int = &m3
var s0 string
var s1 *string
var s2 *string = &s0
var s3 string = "a"
var s4 *string = &s3
var a0 [10]int
var a1 *[10]int
var a2 *[10]int = &a0
var b0 []int
var b1 *[]int
var b2 *[]int = &b0
var b3 []int = []int{1, 2, 3}
var b4 *[]int = &b3
func crash() {
// these uses of nil pointers
// would crash but should type check
println("crash",
len(a1)+cap(a1))
}
func nocrash() {
// this is spaced funny so that
// the compiler will print a different
// line number for each len call if
// it decides there are type errors.
// it might also help in the traceback.
x :=
len(m0) +
len(m3)
if x != 1 {
println("wrong maplen")
panic("fail")
}
x =
len(s0) +
len(s3)
if x != 1 {
println("wrong stringlen")
panic("fail")
}
x =
len(a0) +
len(a2)
if x != 20 {
println("wrong arraylen")
panic("fail")
}
x =
len(b0) +
len(b3)
if x != 3 {
println("wrong slicelen")
panic("fail")
}
x =
cap(b0) +
cap(b3)
if x != 3 {
println("wrong slicecap")
panic("fail")
}
}
func main() { nocrash() }