ADDITIONAL SYSTEM INFORMATION :
Ubuntu 20.04
OpenJDK Runtime Environment (build 19-ea+25-1892)

A DESCRIPTION OF THE PROBLEM :
A method that uses instanceof pattern matching for records fails with a verify error. Rewriting it with classic instanceof succeeds.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the program below with Java 19.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The program runs and prints 3660.0 s
ACTUAL -
Error: Unable to initialize main class Test3
Caused by: java.lang.VerifyError: Bad return type
Exception Details:
  Location:
    Test3.$proxy$unit(LLength;)LLengthUnit; @4: areturn
  Reason:
    Type 'QuantityUnit' (current frame, stack[0]) is not assignable to 'LengthUnit' (from method signature)
  Current Frame:
    bci: @4
    flags: { }
    locals: { 'Length' }
    stack: { 'QuantityUnit' }
  Bytecode:
    0000000: 2ab6 001a b04c bb00 0959 2bb6 000b 2bb7
    0000010: 000f bf
  Exception Handler Table:
    bci [0, 4] => handler: 5
  Stackmap Table:
    same_locals_1_stack_item_frame(@5,Object[#7])

---------- BEGIN SOURCE ----------
interface QuantityUnit {
   double factor();
}

enum LengthUnit implements QuantityUnit {
   m(1), cm(0.01), in(0.01 / 2.54);

   private final double factor;

   public double factor() {
      return factor;
   }
   LengthUnit(double factor) {
      this.factor = factor;
   }

   public static final LengthUnit PREFERRED = m;
}

enum TimeUnit implements QuantityUnit {
   s(1), min(60), h(60 * 60);
   private final double factor;
   public double factor() {
      return factor;
   }
   TimeUnit(double factor) {
      this.factor = factor;
   }

   public static final TimeUnit PREFERRED = s;
}

sealed interface Quantity {
   double value();
   QuantityUnit unit();
}

record Length(double value, LengthUnit unit) implements Quantity {
   public String toString() {
      return value() + " " + unit();
   }
}

record Time(double value, TimeUnit unit) implements Quantity {
   public String toString() {
      return value() + " " + unit();
   }
}


public class Test3 {
   public static <T extends Quantity> T add1(T first, T second) {
      if (first instanceof Time && second instanceof Time) {
         var v1 = first.value();
         var u1 = ((Time) first).unit();
         var v2 = second.value();
         var u2 = second.unit();
         if (u1 == u2)
            return (T) new Time(v1 + v2, u1);
         else
            return (T) new Time(v1 * u1.factor() + v2 * u2.factor(),
                  TimeUnit.PREFERRED);
      }
      else if (first instanceof Length && second instanceof Length) {
         var v1 = first.value();
         var u1 = ((Length) first).unit();
         var v2 = second.value();
         var u2 = second.unit();
         if (u1 == u2)
            return (T) new Length(v1 + v2, u1);
         else
            return (T) new Length(v1 * u1.factor() + v2 * u2.factor(),
                  LengthUnit.PREFERRED);
      }
      else
         return null; // cannot happen
   }

   public static <T extends Quantity> T add2(T first, T second) {
      if (first instanceof Time(var v1, var u1) && second instanceof Time(var v2, var u2)) {
         if (u1 == u2) return (T) new Time(v1 + v2, u1);
         else return (T) new Time(v1 * u1.factor() + v2 * u2.factor(), TimeUnit.PREFERRED);
      } else if (first instanceof Length(var v1, var u1) && second instanceof Length(var v2, var u2)) {
         if (u1 == u2) return (T) new Length(v1 + v2, u1);
         else return (T) new Length(v1 * u1.factor() + v2 * u2.factor(), LengthUnit.PREFERRED);
      }
      else return null; // cannot happen
   }
   
   public static void main(String[] args) {
      System.out.println(add1(new Time(1, TimeUnit.h), new Time(1, TimeUnit.min)));
   }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Don't use pattern matching.

FREQUENCY : always