Less v2 does not compile Twitter's Bootstrap 2.x

I was able to avoid the error without modifying Bootstrap files by creating a new mixin that loaded after the Bootstrap mixins:

#grid {
    .core  {
        .span(@gridColumns) {
            width: (@gridColumnWidth * @gridColumns) + (@gridGutterWidth * (@gridColumns - 1));
        }
    }
};

This was better for us as we avoid patching contrib packages.

In the less/navbar.less file:

Replace:

.navbar-static-top .container,
.navbar-fixed-top .container,
.navbar-fixed-bottom .container {
  #grid > .core > .span(@gridColumns);
}

With:

.navbar-static-top .container,  
.navbar-fixed-top .container,
.navbar-fixed-bottom .container { 
width: (@gridColumnWidth * @gridColumns) + (@gridGutterWidth * (@gridColumns - 1));
}

See also: Overriding class definitions with Less

There's no need to edit the style.

Just npm install [email protected] and you will have a local (inside the folder you are in) copy of the latest less v1, which compiles bootstrap v2.3.2 correctly if you run node_modules/less/bin/lessc source.less output.css.