type mismatch category generics

i have following formula won't accumulate nonetheless there proceed accumulate i wish know since isn't compiling. someone illuminate me personally since i blunder summary i post during finish please?

public category exam {
    open stationary vacant main(string args[]) {
        exam t = new test();
        t.testt(null);
    }

    open <t extends test> vacant testt(class<t> type) {
        class<t> testtype = form == zero ? test.class : type; //error here
        system.out.println(testtype);
    }
}

type mismatch: can't modify class<capture#1-of ? extends test> class<t>

by casting test.class class<t> compiles an unchecked cast warning runs perfectly.