t = db.jstests_count_hint; t.drop();   t.save( { i: 1 } ); t.save( { i: 2 } ); assert.eq( 2, t.find().count() );   // create a sparse index which should have no entries t.ensureIndex( { x:1 }, { sparse: true } );   assert.eq( 0, t.find( { i: 1 } ).hint( "x_1" ).count(), "A" ); assert.eq( 0, t.find( { i: 1 } ).hint( {x: 1} ).length(), "B" ); // With just find works assert.eq( 0, t.find( { i: 1 } ).hint( {x: 1} ).count(), "C" ); // Fails