Bug with let/var and for loop when transpile to ES2015 code

[paul-phan]

Input Code

let abc = '123'
for (let i = 0; i < [1,2,3].length; i++) {
	abc = abc + '345'	
}

console.log(abc)

Actual Output

'use strict';for(var i=0;i<[1,2,3].length;i++){}console.log(abc);

Expected Output

for(var abc="123",i=0;i<[1,2,3].length;i++)abc+="345";console.log(abc);

Details

When I declare a let/var or even const variable before a for loop, It disappeared and make this variable undefined. You can test it with Babel Repl

[boopathi]

Closing this as duplicate of #485