Let's consider following code:

public class Test54 {
static class Nested {
static {
class Local { }
}
}
}

When this code is a subject of annotation processing NPE is thrown when annotation processor invokes getEnclosedElements() on the Element instance representing a package:

java.lang.NullPointerException
        at com.sun.tools.javac.jvm.Code.width(jdk.compiler@9-ea/Code.java:279)
        at com.sun.tools.javac.jvm.ClassReader.initParameterNames(jdk.compiler@9-ea/ClassReader.java:2242)
        at com.sun.tools.javac.jvm.ClassReader.readMethod(jdk.compiler@9-ea/ClassReader.java:2191)
        at com.sun.tools.javac.jvm.ClassReader.readClass(jdk.compiler@9-ea/ClassReader.java:2446)
        at com.sun.tools.javac.jvm.ClassReader.readClassBuffer(jdk.compiler@9-ea/ClassReader.java:2511)
        at com.sun.tools.javac.jvm.ClassReader.readClassFile(jdk.compiler@9-ea/ClassReader.java:2524)
        at com.sun.tools.javac.code.ClassFinder.fillIn(jdk.compiler@9-ea/ClassFinder.java:350)
        at com.sun.tools.javac.code.ClassFinder.complete(jdk.compiler@9-ea/ClassFinder.java:287)
        at com.sun.tools.javac.code.ClassFinder.access$000(jdk.compiler@9-ea/ClassFinder.java:74)
        at com.sun.tools.javac.code.ClassFinder$1.complete(jdk.compiler@9-ea/ClassFinder.java:166)
        at com.sun.tools.javac.code.Symbol.complete(jdk.compiler@9-ea/Symbol.java:623)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.complete(jdk.compiler@9-ea/Symbol.java:1235)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.flags(jdk.compiler@9-ea/Symbol.java:1169)
        at com.sun.tools.javac.code.Symbol$TypeSymbol.getEnclosedElements(jdk.compiler@9-ea/Symbol.java:790)
        at Test54Proc.process(Test54Proc.java:19)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(jdk.compiler@9-ea/JavacProcessingEnvironment.java:959)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(jdk.compiler@9-ea/JavacProcessingEnvironment.java:875)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$2100(jdk.compiler@9-ea/JavacProcessingEnvironment.java:106)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(jdk.compiler@9-ea/JavacProcessingEnvironment.java:1182)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(jdk.compiler@9-ea/JavacProcessingEnvironment.java:1290)
        at com.sun.tools.javac.main.JavaCompiler.processAnnotations(jdk.compiler@9-ea/JavaCompiler.java:1232)
        at com.sun.tools.javac.main.JavaCompiler.compile(jdk.compiler@9-ea/JavaCompiler.java:911)
        at com.sun.tools.javac.main.Main.compile(jdk.compiler@9-ea/Main.java:292)
        at com.sun.tools.javac.main.Main.compile(jdk.compiler@9-ea/Main.java:148)
        at com.sun.tools.javac.Main.compile(jdk.compiler@9-ea/Main.java:55)
        at com.sun.tools.javac.Main.main(jdk.compiler@9-ea/Main.java:41)

This error is reproduced on JDK build 137.

This error is reproduced only when the source is "compiled twice", namely when Test54$Nested$1Local.class is on the class path passed to javac via -classpath option.

The minimized test case is attached, in order to reproduce the bug please:
1. Unzip attached archive to some dir, say A, on Unix/Linux machine.
2. Modify A/Test54/test.sh by setting JDK_HOME variable to your JDK installation dir.
3. Run A/Test54/test.sh.

It produces following output:

First compilation
Root elemnts count: 1
pack: unnamed package
Root elemnts count: 0
Second compilation
Root elemnts count: 1
pack: unnamed package
java.lang.NullPointerException
        at com.sun.tools.javac.jvm.Code.width(jdk.compiler@9-ea/Code.java:279)
        at com.sun.tools.javac.jvm.ClassReader.initParameterNames(jdk.compiler@9-ea/ClassReader.java:2242)
        at com.sun.tools.javac.jvm.ClassReader.readMethod(jdk.compiler@9-ea/ClassReader.java:2191)
        at com.sun.tools.javac.jvm.ClassReader.readClass(jdk.compiler@9-ea/ClassReader.java:2446)
        at com.sun.tools.javac.jvm.ClassReader.readClassBuffer(jdk.compiler@9-ea/ClassReader.java:2511)
        at com.sun.tools.javac.jvm.ClassReader.readClassFile(jdk.compiler@9-ea/ClassReader.java:2524)
        at com.sun.tools.javac.code.ClassFinder.fillIn(jdk.compiler@9-ea/ClassFinder.java:350)
        at com.sun.tools.javac.code.ClassFinder.complete(jdk.compiler@9-ea/ClassFinder.java:287)
        at com.sun.tools.javac.code.ClassFinder.access$000(jdk.compiler@9-ea/ClassFinder.java:74)
        at com.sun.tools.javac.code.ClassFinder$1.complete(jdk.compiler@9-ea/ClassFinder.java:166)
        at com.sun.tools.javac.code.Symbol.complete(jdk.compiler@9-ea/Symbol.java:623)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.complete(jdk.compiler@9-ea/Symbol.java:1235)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.flags(jdk.compiler@9-ea/Symbol.java:1169)
        at com.sun.tools.javac.code.Symbol$TypeSymbol.getEnclosedElements(jdk.compiler@9-ea/Symbol.java:790)
        at Test54Proc.process(Test54Proc.java:19)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(jdk.compiler@9-ea/JavacProcessingEnvironment.java:959)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(jdk.compiler@9-ea/JavacProcessingEnvironment.java:875)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$2100(jdk.compiler@9-ea/JavacProcessingEnvironment.java:106)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(jdk.compiler@9-ea/JavacProcessingEnvironment.java:1182)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(jdk.compiler@9-ea/JavacProcessingEnvironment.java:1290)
        at com.sun.tools.javac.main.JavaCompiler.processAnnotations(jdk.compiler@9-ea/JavaCompiler.java:1232)
        at com.sun.tools.javac.main.JavaCompiler.compile(jdk.compiler@9-ea/JavaCompiler.java:911)
        at com.sun.tools.javac.main.Main.compile(jdk.compiler@9-ea/Main.java:292)
        at com.sun.tools.javac.main.Main.compile(jdk.compiler@9-ea/Main.java:148)
        at com.sun.tools.javac.Main.compile(jdk.compiler@9-ea/Main.java:55)
        at com.sun.tools.javac.Main.main(jdk.compiler@9-ea/Main.java:41)