Consider the following example:

package foo;

class Test {

String s;

static class Sup {
        Sup(Runnable r) { }
    }

    class Sub extends Sup {
        Sub() {
            super(() -> { s.startsWith("L"); });
        }
    }

    public static void main(String[] args) {
new Test().new Sub();
    }
}

Running Test with -Xverify:all leads to a verifier error:

Exception in thread "main" java.lang.ClassFormatError: Illegal field name "foo.Test$this" in class foo/Test$Sub
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:759)
at java.lang.ClassLoader.defineClass(ClassLoader.java:835)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:184)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:547)
at java.net.URLClassLoader.access$100(URLClassLoader.java:87)
at java.net.URLClassLoader$1.run(URLClassLoader.java:413)
at java.net.URLClassLoader$1.run(URLClassLoader.java:397)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:396)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:262)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at foo.Test.main(Main.java:28)


The problem lies in the name of a synthetic lambda parameter being bogus, as shown on javap:

private static void lambda$new$0(foo.Test);
    descriptor: (Lfoo/Test;)V
    flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
    Code:
      stack=2, locals=1, args_size=1
         0: aload_0
         1: getfield #4 // Field foo/Test.s:Ljava/lang/String;
         4: ldc #5 // String L
         6: invokevirtual #6 // Method java/lang/String.startsWith:(Ljava/lang/String;)Z
         9: pop
        10: return
      LineNumberTable:
        line 23: 0
      LocalVariableTable:
        Start Length Slot Name Signature
            0 11 0 foo.Test$this Lfoo/Test; // <----------------------
}