https://mail.openjdk.org/pipermail/amber-dev/2023-September/008300.html

The following raises a java.lang.VerifyError for the fourth case, unless the first component of the third case is named.

public class TestUnnamed {
    record Tuple<T1, T2>(T1 first, T2 second) {}
    record R1<T>(Integer value) implements R<T> {}
    record R2<T>(Integer value) implements R<T> {}
    sealed interface R<T> {}

    static <T1 extends Comparable, T2 extends Comparable> int compareTo(Tuple<R<T1>, R<T2>> o) {
        return switch (o) {
            case Tuple<R<T1>, R<T2>>(R1<T1> _, R1<T2> _) -> -1;
            case Tuple<R<T1>, R<T2>>(R1<T1> _, R2<T2> _) -> -1;
            case Tuple<R<T1>, R<T2>>(R2<T1> _, R1<T2> _) -> -1;
            case Tuple<R<T1>, R<T2>>(R2<T1> fst, R2<T2> snd) -> fst.value().compareTo(snd.value());
        };
    }

    public static void main(String[] args) {
        compareTo(new Tuple<R<Integer>, R<Integer>>(new R2<Integer>(1), new R2<Integer>(2)));
    }
}

Output:

> java --enable-preview --source 22 TestUnnamed.java java 22-internal
Note: TestUnnamed.java uses preview features of Java SE 22.
Note: Recompile with -Xlint:preview for details.
Exception in thread "main" java.lang.VerifyError: Bad local variable type
Exception Details:
  Location:
    TestUnnamed.compareTo(LTestUnnamed$Tuple;)I @215: aload
  Reason:
    Type top (current frame, locals[7]) is not assignable to reference type
  Current Frame:
    bci: @215
    flags: { }
    locals: { 'TestUnnamed$Tuple', 'TestUnnamed$Tuple', integer, 'TestUnnamed$Tuple', top, top, top, top, top, 'TestUnnamed$R2', 'TestUnnamed$R', integer, 'TestUnnamed$R', integer }
    stack: { }
  Bytecode:
    0000000: 2a59 b800 0757 4c03 3d2b 1cba 000d 0000
    0000010: ab00 0000 0000 0014 0000 0001 0000 0000
    0000020: 0000 001e bb00 1159 0101 b700 13bf 2b4e
    0000030: 2db6 0016 c000 1c3a 0a03 360b 190a 150b
    0000040: ba00 1e00 00aa 0000 0000 00a8 ffff ffff
    0000050: 0000 0001 0000 00a8 0000 001b 0000 0059
    0000060: 2db6 001f c000 1c3a 0c03 360d 190c 150d
    0000070: ba00 1e00 00aa 0000 0000 0023 ffff ffff
    0000080: 0000 0001 0000 0023 0000 001b 0000 001f
    0000090: 02a7 0061 02a7 005d 0436 0ba7 ffa1 2db6
    00000a0: 001f c000 1c3a 0c03 360d 190c 150d ba00
    00000b0: 1e00 00aa 0000 0034 ffff ffff 0000 0001
    00000c0: 0000 0034 0000 0019 0000 001d 02a7 0025
    00000d0: 190c c000 223a 0919 07b6 0024 1909 b600
    00000e0: 24b6 0028 a700 0e05 360b a7ff 5204 3da7
    00000f0: ff1a ac4c bb00 1159 2bb6 0030 2bb7 0013
    0000100: bf
  Exception Handler Table:
    bci [49, 52] => handler: 243
    bci [97, 100] => handler: 243
    bci [159, 162] => handler: 243
  Stackmap Table:
    append_frame(@9,Object[#23],Integer)
    same_frame(@36)
    same_frame(@46)
    full_frame(@60,{Object[#23],Object[#23],Integer,Object[#23],Top,Top,Top,Top,Top,Top,Object[#28],Integer},{})
    same_frame(@96)
    append_frame(@108,Object[#28],Integer)
    same_frame(@144)
    same_frame(@148)
    same_frame(@152)
    chop_frame(@158,2)
    append_frame(@170,Object[#28],Integer)
    same_frame(@204)
    same_frame(@208)
    same_frame(@231)
    chop_frame(@237,2)
    full_frame(@242,{Object[#23]},{Integer})
    same_locals_1_stack_item_frame(@243,Object[#46])

        at java.base/java.lang.Class.forName0(Native Method)
        at java.base/java.lang.Class.forName(Class.java:537)
        at java.base/java.lang.Class.forName(Class.java:516)
        at jdk.compiler/com.sun.tools.javac.launcher.Main.execute(Main.java:432)
        at jdk.compiler/com.sun.tools.javac.launcher.Main.run(Main.java:208)
        at jdk.compiler/com.sun.tools.javac.launcher.Main.main(Main.java:135)