go const4 源码
golang const4 代码
文件路径：/test/const4.go
// run
// Copyright 2011 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 len constants and non-constants, https://golang.org/issue/3244.
package main
var b struct {
a [10]int
}
var m map[string][20]int
var s [][30]int
const (
n1 = len(b.a)
n2 = len(m[""])
n3 = len(s[10])
)
// Non-constants (see also const5.go).
var (
n4 = len(f())
n5 = len(<-c)
n6 = cap(g())
n7 = cap(<-c1)
)
var calledF = false
func f() *[40]int {
calledF = true
return nil
}
var c = func() chan *[50]int {
c := make(chan *[50]int, 2)
c <- nil
c <- new([50]int)
return c
}()
var calledG = false
func g() *[60]int {
calledG = true
return nil
}
var c1 = func() chan *[70]int {
c := make(chan *[70]int, 2)
c <- nil
c <- new([70]int)
return c
}()
func main() {
if n1 != 10 || n2 != 20 || n3 != 30 || n4 != 40 || n5 != 50 || n6 != 60 || n7 != 70 {
println("BUG:", n1, n2, n3, n4, n5, n6, n7)
panic("fail")
}
if !calledF {
println("BUG: did not call f")
panic("fail")
}
if <-c == nil {
println("BUG: did not receive from c")
panic("fail")
}
if !calledG {
println("BUG: did not call g")
panic("fail")
}
if <-c1 == nil {
println("BUG: did not receive from c1")
panic("fail")
}
}
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