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)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.16299.248]

A DESCRIPTION OF THE PROBLEM :
> cat Error.java
class Error<T,T,T> {

}
> javac -version
javac 1.8.0_144
> javac .\Error.java
コンパイラで例外が発生しました(1.8.0_144)。Bug Database (http://bugs.java.com)で重複がないかをご確認のうえ、Java bugレポート・ページ(http://bugreport.java.com)でJavaコンパイラに対するbugの登録をお願いいたします。レポートには、そのプログラムと下記の診断内容を含めてください。ご協力ありがとうございます。
java.lang.NullPointerException
        at com.sun.tools.javac.comp.MemberEnter.baseEnv(MemberEnter.java:1388)
        at com.sun.tools.javac.comp.MemberEnter.complete(MemberEnter.java:1046)
        at com.sun.tools.javac.code.Symbol.complete(Symbol.java:574)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1037)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.flags(Symbol.java:973)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.getKind(Symbol.java:1101)
        at com.sun.tools.javac.code.Kinds.kindName(Kinds.java:162)
        at com.sun.tools.javac.comp.Check.duplicateError(Check.java:329)
        at com.sun.tools.javac.comp.Check.checkUnique(Check.java:3380)
        at com.sun.tools.javac.comp.Enter.visitTypeParameter(Enter.java:454)
        at com.sun.tools.javac.tree.JCTree$JCTypeParameter.accept(JCTree.java:2224)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.visitClassDef(Enter.java:418)
        at com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:693)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.visitTopLevel(Enter.java:334)
        at com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:518)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.complete(Enter.java:486)
        at com.sun.tools.javac.comp.Enter.main(Enter.java:471)
        at com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:982)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:857)
        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)



REPRODUCIBILITY :
This bug can be reproduced always.