Using the Lessoid/Less 2.7.2 drop in: https://github.com/HydraWiki/lessoid
ParseError: Unrecognised input in ../mmv.mixins.less on line 42, column 65:
41 /* stylelint-disable number-no-trailing-zeros */
42 filter: progid:DXImageTransform.Microsoft.BasicImage( rotation=( @degrees / 90.0 ) );
43 -ms-filter: 'progid:DXImageTransform.Microsoft.BasicImage( rotation=( @degrees / 90.0 ) )';
I fixed it by escaping the input per Less documentation, but I am unsure if this will work with MediaWiki's default outdated Less.php implementation.
filter: e("progid:DXImageTransform.Microsoft.BasicImage( rotation=(") @degrees / 90.0 e(") )"); -ms-filter: e("'progid:DXImageTransform.Microsoft.BasicImage( rotation=(") @degrees / 90.0 e(") )'");
Which produces:
/* stylelint-disable number-no-trailing-zeros */ filter: progid:DXImageTransform.Microsoft.BasicImage( rotation=( -0.5deg ) ); -ms-filter: 'progid:DXImageTransform.Microsoft.BasicImage( rotation=( -0.5deg ) )';