Shadowing issue errorneuously reported as redefinition when using block scoping

[fluidsonic]

const Set = require('some-set-package');  // Redefinition of 'Set'

Since let and const are block scoped the global variable will be left untouched.
This looks like a bug as this is shadowing, not redefinition.

I actually stumbled across this problem when overwriting Set (as node's implementation is very limited) and we can expect more such warnings in the future as the number of predefined global symbols increases.

(jshint 2.5.11)

[lukeapage]

@jugglinmike this can probably be closed I think, unless @fluidsonic can provide a proper test case which doesn't work on master, but I think it should.

[jugglinmike]

This is still an issue on master

gh-2090.js:

// jshint esnext: true
{
  var Proxy = null; // expected error
  const Set = null;
  let Map = null;
}
(function() {
  var Proxy = null;
  const Set = null;
  let Map = null;
}());

gh-2090.js: line 3, col 7, Redefinition of 'Proxy'.
gh-2090.js: line 4, col 9, Redefinition of 'Set'.
gh-2090.js: line 5, col 7, Redefinition of 'Map'.