Tell us about your environment

• ESLint Version: 5.8.0/master
• Node Version: n/a
• npm Version: n/a

What parser (default, Babel-ESLint, etc.) are you using?
default
Please show your full configuration:

{
  rules: {"no-else-return": 2}
}

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

function foo(){
    let bar = 0;
    if(cond) {
        return bar;
    } else {
        let bar = 1;
        return bar;
    }
}

What did you expect to happen?
not fix to incorrect code.

What actually happened? Please include the actual, raw output from ESLint.

fixed code:

function foo(){
    let bar = 0;
    if(cond) {
        return bar;
    } 
        let bar = 1;
        return bar;
    
}

7:13  error  Parsing error: Identifier 'bar' has already been declared

Are you willing to submit a pull request to fix this bug?
yes, but I don't have time to do it in the following days. please feel free to take it if someone else have interests.