A potential JDK 20 bug

[Tesla Zhang]

Trying to run the following code with jdk 20 leads to java.lang.VerifyError:

public class Java20 {
  sealed interface AST {}
  record Lam(String name, AST ast) implements AST {}
  record Var(String name) implements AST {}
  record Pair(AST a, AST b) {}

  static void test(AST x, AST y) {
    System.out.println(switch (new Pair(x, y)) {
      case Pair(Lam(var a, var b), var c) -> a + b + c;
      case Pair(var a, Lam b) -> b.toString();
      default -> "1919";
    });
  }

  public static void main(String[] args) {
    test(new Var("a"), new Var("b"));
  }
}


The exception is:


Error: Unable to initialize main class com.intellij.bug.Java20 in module intellij.bug.reports
Caused by: java.lang.VerifyError: Bad local variable type
Exception Details:
  Location:
    com/intellij/bug/Java20.test(Lcom/intellij/bug/Java20$AST;Lcom/intellij/bug/Java20$AST;)V @192: aload
  Reason:
    Type top (current frame, locals[10]) is not assignable to reference type
  Current Frame:
    bci: @192
    flags: { }
    locals: { 'com/intellij/bug/Java20$AST', 'com/intellij/bug/Java20$AST', 'com/intellij/bug/Java20$Pair', integer, 'com/intellij/bug/Java20$Pair', top, top, top, top, 'com/intellij/bug/Java20$AST', top, 'com/intellij/bug/Java20$AST', integer }
    stack: { 'java/io/PrintStream' }
  Bytecode:
    0000000: b200 07bb 000d 592a 2bb7 000f 59b8 0012
    0000010: 574d 033e 2c1d ba00 1800 00ab 0000 00b2
    0000020: 0000 0001 0000 0000 0000 0011 2c3a 0419
    0000030: 04b6 001c 3a0b 0336 0c19 0b15 0cba 0020
    0000040: 0000 aa00 0000 0086 ffff ffff 0000 0001
    0000050: 0000 0056 0000 001a 0000 0056 190b c000
    0000060: 213a 0519 04b6 0023 3a0d 190d 3a06 1905
    0000070: b600 263a 0d19 0d3a 0719 05b6 002a 3a0d
    0000080: 190d 3a08 1907 1908 b800 2d19 06b8 002d
    0000090: ba00 3300 00a7 003d 190b 3a09 1909 c600
    00000a0: 2219 04b6 0023 3a0d 190d c100 2199 000d
    00000b0: 190d c000 213a 0aa7 0009 0536 0ca7 ff7c
    00000c0: 190a b600 37a7 000d 043e a7ff 4a12 3aa7
    00000d0: 0003 b600 3ca7 0011 4dbb 0044 592c b600
    00000e0: 462c b700 47bf b1                      
  Exception Handler Table:
    bci [49, 52] => handler: 216
    bci [101, 104] => handler: 216
    bci [112, 115] => handler: 216
    bci [123, 126] => handler: 216
    bci [163, 166] => handler: 216
  Stackmap Table:
    full_frame(@20,{Object[#97],Object[#97],Object[#13],Integer},{Object[#61]})
    same_locals_1_stack_item_frame(@44,Object[#61])
    full_frame(@57,{Object[#97],Object[#97],Object[#13],Integer,Object[#13],Top,Top,Top,Top,Top,Top,Object[#97],Integer},{Object[#61]})
    same_locals_1_stack_item_frame(@92,Object[#61])
    same_locals_1_stack_item_frame(@152,Object[#61])
    full_frame(@186,{Object[#97],Object[#97],Object[#13],Integer,Object[#13],Top,Top,Top,Top,Object[#97],Top,Object[#97],Integer},{Object[#61]})
    same_locals_1_stack_item_frame(@192,Object[#61])
    full_frame(@200,{Object[#97],Object[#97],Object[#13],Integer,Object[#13],Top,Top,Top,Top,Top,Top,Object[#97],Integer},{Object[#61]})
    full_frame(@205,{Object[#97],Object[#97],Object[#13],Integer},{Object[#61]})
    full_frame(@210,{Object[#97],Object[#97]},{Object[#61],Object[#46]})
    same_locals_1_stack_item_frame(@216,Object[#66])
    same_frame(@230)



Env:
openjdk version "20.0.2" 2023-07-18
OpenJDK Runtime Environment (build 20.0.2+10)
OpenJDK 64-Bit Server VM (build 20.0.2+10, mixed mode, sharing)



Best regards,
Tesla Zhang
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