javac exception when referencing private inner class with same name as normal class with dollar_1

FULL PRODUCT VERSION :
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

java version "9"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
macOS Sierra v10.12.6
Microsoft Windows [Version 10.0.10240]

A DESCRIPTION OF THE PROBLEM :
Compiling the sample program below causes javac to terminate with a NullPointerException. It appears to be problem caused by an interaction between a private inner class and a normal class with the same name composed of the containing class name and '$1'. This happens at least on Windows and macOS, and happens with Java 8 and Java 9, but does not happen in Java 7 (and possibly earlier versions).


REGRESSION. Last worked in version 7u80

ADDITIONAL REGRESSION INFORMATION:
java version "1.7.0_80"
Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
javac R.java

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Successful compilation.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Java 8:
An exception has occurred in the compiler (1.8.0_144). 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 and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
at com.sun.tools.javac.comp.Lower.makeEmptyClass(Lower.java:658)
at com.sun.tools.javac.comp.Lower.checkAccessConstructorTags(Lower.java:786)
at com.sun.tools.javac.comp.Lower.translateTopLevelClass(Lower.java:3938)
at com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1512)
at com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1356)
at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:901)
at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:860)
at com.sun.tools.javac.main.Main.compile(Main.java:523)
at com.sun.tools.javac.main.Main.compile(Main.java:381)
at com.sun.tools.javac.main.Main.compile(Main.java:370)
at com.sun.tools.javac.main.Main.compile(Main.java:361)
at com.sun.tools.javac.Main.compile(Main.java:56)
at com.sun.tools.javac.Main.main(Main.java:42)

Java 9:
An exception has occurred in the compiler (9). 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 and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
at jdk.compiler/com.sun.tools.javac.comp.Lower.makeEmptyClass(Lower.java:660)
at jdk.compiler/com.sun.tools.javac.comp.Lower.checkAccessConstructorTags(Lower.java:788)
at jdk.compiler/com.sun.tools.javac.comp.Lower.translateTopLevelClass(Lower.java:3926)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1565)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1418)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:959)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:302)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:162)
at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:57)
at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:43)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
// R.java
package test;
class R {
    private class R$1 {}
    void f() {
        new R$1();
    }
}
class R$1 {}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Changing the inner class to be non-private causes the compile to succeed.
Changing the class names from R$1 to R$2 causes the compile to succeed.
Changing the class names from R$1 to V$1 causes the compile to succeed.
Removing either R$1 class definition cause the compile to succeed.

Avoiding use of '$' in class names, although perhaps this construction is hard to avoid in certain cases when generating code.