FULL PRODUCT VERSION :
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b73)
Java HotSpot(TM) 64-Bit Server VM (build 1.9.0-ea-b73, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
javac crashes with an assertionerror in ClassSymbol.setAnnotationTypeMetadata when an annotation processor generates a source file that declares an annotation with the same qualified name as an annotation that was already on the classpath.

This issue bisects to the fix for JDK-8031744:

* https://bugs.openjdk.java.net/browse/JDK-8031744
* http://hg.openjdk.java.net/jdk9/dev/langtools/rev/62e285806e83

REGRESSION.  Last worked in version 8u51

ADDITIONAL REGRESSION INFORMATION: 
java version "1.8.0_51"
Java(TM) SE Runtime Environment (build 1.8.0_51-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.51-b03, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
$ javac Processor.java 
$ javac -processor Processor Test.java 
$ javac -processor Processor Test.java 

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I was expecting javac to not crash.
ACTUAL -
javac crashed.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
An exception has occurred in the compiler (1.9.0-ea). Please file a bug at the Java Bug Database (http://bugreport.java.com/bugreport/) after checking the database for duplicates. Include your program and the following diagnostic in your report.  Thank you.
java.lang.AssertionError
	at com.sun.tools.javac.util.Assert.error(Assert.java:155)
	at com.sun.tools.javac.util.Assert.check(Assert.java:46)
	at com.sun.tools.javac.code.Symbol$ClassSymbol.setAnnotationTypeMetadata(Symbol.java:1241)
	at com.sun.tools.javac.comp.TypeEnter$MembersPhase.finishClass(TypeEnter.java:901)
	at com.sun.tools.javac.comp.TypeEnter$MembersPhase.doRunPhase(TypeEnter.java:882)
	at com.sun.tools.javac.comp.TypeEnter$Phase.runPhase(TypeEnter.java:251)
	at com.sun.tools.javac.comp.TypeEnter$Phase.runPhase(TypeEnter.java:265)
	at com.sun.tools.javac.comp.TypeEnter$Phase.runPhase(TypeEnter.java:265)
	at com.sun.tools.javac.comp.TypeEnter$Phase.runPhase(TypeEnter.java:265)
	at com.sun.tools.javac.comp.TypeEnter.complete(TypeEnter.java:196)
	at com.sun.tools.javac.code.Symbol.complete(Symbol.java:579)
	at com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1074)
	at com.sun.tools.javac.comp.Enter.complete(Enter.java:490)
	at com.sun.tools.javac.comp.Enter.main(Enter.java:467)
	at com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:952)
	at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.enterTrees(JavacProcessingEnvironment.java:1003)
	at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.<init>(JavacProcessingEnvironment.java:898)
	at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.next(JavacProcessingEnvironment.java:916)
	at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1141)
	at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1141)
	at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:832)
	at com.sun.tools.javac.main.Main.compile(Main.java:253)
	at com.sun.tools.javac.main.Main.compile(Main.java:141)
	at com.sun.tools.javac.Main.compile(Main.java:56)
	at com.sun.tools.javac.Main.main(Main.java:42)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
=== Test.java ===
@Deprecated
@AutoAnnotation_Test
public class Test {}
===

=== Processor.java ===
import java.io.IOError;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.tools.JavaFileObject;

@SupportedAnnotationTypes("*")
public class Processor extends AbstractProcessor {

  @Override
  public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
    if (!roundEnv.processingOver()) {
      for (Element element : roundEnv.getRootElements()) {
        String elementName = element.getSimpleName().toString();
        if (elementName.startsWith("AutoAnnotation_")) {
          continue;
        }
        String name = "AutoAnnotation_" + elementName;
        JavaFileObject jfo;
        try {
          jfo = processingEnv.getFiler().createSourceFile(name, element);
        } catch (IOException e) {
          throw new IOError(e);
        }
        try (OutputStream os = jfo.openOutputStream()) {
          String output = String.format("public @interface %s {}", name);
          os.write(output.getBytes(StandardCharsets.UTF_8));
        } catch (IOException e) {
          throw new IOError(e);
        }
      }
    }
    return false;
  }
}
===
---------- END SOURCE ----------