gistfile1.txt

Error: Invalid isolate scope definition for directive btn: <i class=@icon></i>

JS:
angular.module('myApp', []).directive('btn', function() {
  return {
    scope: { inner: '<i class=@icon></i>' },
    template: '<button class="btn span4">{{inner}}</button>',
    restrict: 'E',
    replace: true,
    transclude: true
  }
});

HTML
<btn icon="icon-fast-forward"></btn>