Possible new rule-disallow naming a variable in a function the same as a function parameter

[capaj]

I'd like to have a rule against naming variables in a function the same as a function parameter.
It makes code unreadable, because it requires the reader to resolve the scope of current variable based on scoping rules and that's not always easy, especially with let.
I don't think there is an eslint rule for this, but if there would be a a positive stance toward this rule by standard maintainers I'd love to write such a rule.

example of invalid code:

function (a) {
  let a
}

[dcousens]

http://eslint.org/docs/rules/no-redeclare

It is enabled... your example doesn't work.

[capaj]

@dcousens sorry, what I meant was:

function (a) {
  if (a) {
    let a = 1
    console.log(a)
  }
}

this one is valid currently.