if, for等可以有初始化表达式的，其作用域还要高于其后的花括号一层

package mainfunc main() {	x:=1	println(x)		for x:=3;;{		print(x," ")		break	}	println(x)		if x:=5; true {		print(x," ")	}	println(x)		for {		x:=7		print(x," ")		break	}	println(x)		if true {		x:=9		print(x," ")	}	println(x)	if x:=2; true {		print(x," ")		x:="abc"		print(x," ")	}	println(x)		for x:=4;; {		print(x," ")		x:="def"		print(x," ")		break	}	println(x)}// 1// 3 1// 5 1// 7 1// 9 1// 2 abc 1// 4 def 1