[upstream] [preview] javac AssertionError

[NekoCaffeine]

First, I don't have permission to open issues in the Java Bug System.

Reproducible code:

public class SwitchBug {
    
    interface A { }
    
    interface B { }
    
    public static void main(final String... args) {
        f((B) switch (new Object()) {
            case Object obj -> new A() {};
        });
    }
    
    static void f(final B b) { }
    
}

Source file: SwitchBug.zip

Compile command:

javac --enable-preview -source 17 SwitchBug.java

Stack trace:

java.lang.AssertionError
        at jdk.compiler/com.sun.tools.javac.util.Assert.error(Assert.java:155)
        at jdk.compiler/com.sun.tools.javac.util.Assert.check(Assert.java:46)
        at jdk.compiler/com.sun.tools.javac.jvm.Code$State.forceStackTop(Code.java:1776)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitYield(Gen.java:1802)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCYield.accept(JCTree.java:1658)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:610)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:645)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:631)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStats(Gen.java:682)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStats(Gen.java:666)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.handleSwitch(Gen.java:1373)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.doHandleSwitchExpression(Gen.java:1238)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitSwitchExpression(Gen.java:1202)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCSwitchExpression.accept(JCTree.java:1380)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitLetExpr(Gen.java:2381)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$LetExpr.accept(JCTree.java:3287)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitTypeCast(Gen.java:2228)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCTypeCast.accept(JCTree.java:2185)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genArgs(Gen.java:902)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitApply(Gen.java:1880)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1797)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitExec(Gen.java:1748)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1584)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:610)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:645)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:631)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStats(Gen.java:682)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1097)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1091)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:610)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:645)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genMethod(Gen.java:967)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitMethodDef(Gen.java:930)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:921)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:610)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genClass(Gen.java:2420)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.genCode(JavaCompiler.java:737)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1617)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1585)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:946)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:317)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:176)
        at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:64)
        at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:50)

Version info:

openjdk version "17.0.4" 2022-07-19 LTS
OpenJDK Runtime Environment SapMachine (build 17.0.4+8-LTS)
OpenJDK 64-Bit Server VM SapMachine (build 17.0.4+8-LTS, mixed mode, sharing)

[NekoCaffeine]

Workaround: Disable that assertion. There is no problem with the stack frame type of the generated bytecode.

[RealCLanger]

Yep, I checked. The code should be valid and the compilation should not fail. I opened https://bugs.openjdk.org/browse/JDK-8291657. Workaround in code: Extract the switch expression from the function call and assign it to a variable which you pass to the call of f().

[RealCLanger]

Looks like the issue is fixed in OpenJDK head now. I'm closing this issue then. Do you need it backported to e.g. 19 or 17?