Simple.java

import org.checkerframework.checker.tainting.qual.Untainted;

class Simple {

    void execute(@Untainted String s) {}

    void tainted(String s) {}

    void stringLiteral() {
        execute("ldskjfldj");
        tainted("lksjdflkjdf");
    }

    void stringRef(String ref) {
        //:: error: (argument.type.incompatible)
        execute(ref); // error
        tainted(ref);
    }

    void untaintedRef(@Untainted String ref) {
        execute(ref);
        tainted(ref);
    }

    void concatenation(@Untainted String s1, String s2) {
        execute(s1 + s1);
        execute(s1 += s1);
        execute(s1 + "m");
        //:: error: (argument.type.incompatible)
        execute(s1 + s2); // error

        //:: error: (argument.type.incompatible)
        execute(s2 + s1); // error
        //:: error: (argument.type.incompatible)
        execute(s2 + "m"); // error
        //:: error: (argument.type.incompatible)
        execute(s2 + s2); // error

        tainted(s1 + s1);
        tainted(s1 + "m");
        tainted(s1 + s2);

        tainted(s2 + s1);
        tainted(s2 + "m");
        tainted(s2 + s2);
    }
}