理解Go的错误[err is shadowed during return]

毫不例外的，我也遇见了[err is shadowed during return]的错误。然后上网搜原因，找到了[http://www.knowsky.com/1061898.html]，然后明白了报错原因。现记录于此：

package mainimport "fmt"func main() {myTest()v0, v1 := myTest3()fmt.Println("myTest3:", v0, v1)}func myTest() (retI int, retF float64) { //返回值列表定义了retI和retF变量,作用域是整个函数体//retI, retF := 0, 0.0 //报错:[no new variables on left side of :=]//左边不需要"全部都是新变量",但可以是"一部分新变量+一部分老变量"i0, retF := 1, 1.1i1, retF := 2, 2.2i2, retF := 3, 3.3fmt.Println("print1:", retI, retF, i0, i1, i2)if true { //新的语句块,产生了新的作用域retI, retF := -1, -1.1 //这里又定义了新的变量retI和retF,和返回值列表重名了,作用域是if语句块fmt.Println("print2:", retI, retF)}fmt.Println("print3:", retI, retF)if true {j0, retF := -2, -2.2 //这里又定义了新的变量j0和retF,其中retF和返回值列表中的retF重名了fmt.Println("print4:", retI, retF, j0)}fmt.Println("print5:", retI, retF)if true {retI, retF = 9, 9.9 //修改老变量的值fmt.Println("print6:", retI, retF)}fmt.Println("print7:", retI, retF)return}func myTest2() (retI int, retF float64) {if true { //新的作用域i0, retF := -1, -1.1fmt.Println(i0, retF)return //报错:[retF is shadowed during return]//无返回值的return,会把返回值列表中的retI和retF返回出去,而不是新的作用域里的retF}return}func myTest3() (retI int, retF float64) {if true {i0, retF := -1, -1.1fmt.Println(i0, retF)return retI, retF //这里返回的是外层的retI和里层的retF,因为指明了,所以没有报错}return}

结束。