My colleague Eddie Aftandilian discovered the following crash, which only occurs when annotation processing is enabled and the flags used include -XDshould-stop.ifError=FLOW.

This bug has some features in common with JDK-8225003, but it may not be an exact duplicate: the stack trace is different, and the required flag is a new wrinkle.

=== EmptyProcessor.java
import java.util.Set;
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.lang.model.element.TypeElement;

public class EmptyProcessor extends AbstractProcessor {
  @Override
  public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
    return false;
  }
}
=== MyClass.java
public class MyClass {
  enum MyEnum {
    FIRST,
    SECOND,
    THIRD. // syntax error
    FOURTH,
    FIFTH,
    SIXTH;
  }

  private void test() {
    Foo.bar(Object.class);
    val1 += val2;
  }
}
===

$ javac -fullversion
javac full version "13-ea+30"
$ javac EmptyProcessor.java
$ javac -XDshould-stop.ifError=FLOW -processor EmptyProcessor MyClass.java
An exception has occurred in the compiler (13-ea). Please file a bug against the Java compiler via the Java bug reporting page (http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com) for duplicates. Include your program, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
java.lang.AssertionError: Unexpected tree: val1 += val2 with kind: PLUS_ASSIGNMENT within: val1 += val2 with kind: PLUS_ASSIGNMENT
        at jdk.compiler/com.sun.tools.javac.util.Assert.error(Assert.java:162)
        at jdk.compiler/com.sun.tools.javac.comp.Attr$TypeAnnotationsValidator.validateAnnotatedType(Attr.java:5154)
        at jdk.compiler/com.sun.tools.javac.comp.Attr$TypeAnnotationsValidator.visitVarDef(Attr.java:5000)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:966)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Attr$TypeAnnotationsValidator.visitClassDef(Attr.java:5053)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:784)
        at jdk.compiler/com.sun.tools.javac.comp.Attr.validateTypeAnnotations(Attr.java:4949)
        at jdk.compiler/com.sun.tools.javac.code.TypeAnnotations.lambda$validateTypeAnnotationsSignatures$1(TypeAnnotations.java:134)
        at jdk.compiler/com.sun.tools.javac.comp.Annotate.flush(Annotate.java:200)
        at jdk.compiler/com.sun.tools.javac.comp.Annotate.unblockAnnotations(Annotate.java:144)
        at jdk.compiler/com.sun.tools.javac.comp.Annotate.enterDone(Annotate.java:157)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.enterDone(JavaCompiler.java:1746)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:1073)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:936)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:318)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:176)
        at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:57)
        at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:43)