The test consists of a Java source file and a jasm file which are used as follows:

 * @compile CallSites.jasm
 * @run main/othervm -Xverify:all -Xbatch
 * -XX:CompileCommand=dontinline,compiler.linkage.LinkageErrors::test*
 * compiler.linkage.LinkageErrors

The Java file defines:

interface I {
    void m1(int i);
    static void s1() {}
}

class A implements I {
    public void m1(int i) {}
}

the jasm file has:

super class compiler/linkage/I
version 52:0
{

}

which defines I as a class not an interface.

When we run the test from clean the @compile causes the jasm to be processed and I.class is generate where I is a class. Then the @run causes LinkageErrors.java to be compiled, which overwrites I.class with a new version when I is an interface again. The test then runs, instantiates class A, and everything passes.

If you then run the test again, jtreg again processes the @compile for the jasm file and so we get I.class where I is a class. For the @run however jtreg sees that LinkageError.class is up to date and so doesn't re-run javac. Now when we instantiate A it claims I as a superinterface but I is class and so the test fails with:

 java.lang.IncompatibleClassChangeError: Implementing class

which comes from the classFileParser when loading a class and it finds that a listed superinterface is not in fact an interface.

The definition of I in the jasm file needs to be a proper interface definition, not a class definition.