javac 11.0.6 NullPointerException when a type param refers to missing type

[Vitaly Davidovich]

Hi guys,

Wanted to bring this up in case the mail slipped through.  If there's any
additional info that you'd like, happy to provide it.  Or if there's a more
appropriate channel to report this, please let me know; I thought about
going to JBS directly, but pinging this list seemed like a good start.

Thanks!

On Wed, Mar 18, 2020 at 7:47 PM Vitaly Davidovich <vitalyd at gmail.com> wrote:

> Hi all,
>
> I'd like to report a bug against javac 11.0.6 (and possibly later, but I
> don't readily have access to newer versions).
>
> To reproduce:
>
> Create the following 3 source files:
>
> ////// A.java
>
> public class A<T extends B<T>> {
>
>     public void foo() {}
>
> }
>
>
>
> ////// B.java
>
> public class B<T> {}
>
>
>
> ////// C.java
>
> public class C {
>
>     public static void crashJavaC(A a) {
>
>         a.foo(null);
>
>     }
>
> }
>
>
> $ javac A.java B.java
>
> $ rm B.java B.class
>
> $ javac C.java
>
> An exception has occurred in the compiler (11.0.6). 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.TransTypes.visitSelect(TransTypes.java:811)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCFieldAccess.accept(JCTree.java:2114)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.translate(TransTypes.java:454)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.visitApply(TransTypes.java:622)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1634)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.translate(TransTypes.java:454)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.visitExec(TransTypes.java:599)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1452)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:70)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitBlock(TreeTranslator.java:167)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1020)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.translate(TransTypes.java:454)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.visitMethodDef(TransTypes.java:489)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:866)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:70)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.visitClassDef(TreeTranslator.java:139)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.translateClass(TransTypes.java:918)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.visitClassDef(TransTypes.java:475)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:774)
>
>                 at
> jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.translate(TransTypes.java:454)
>
>                 at
> jdk.compiler/com.sun.tools.javac.comp.TransTypes.translateTopLevelClass(TransTypes.java:942)
>
>                 at
> jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1553)
>
>                 at
> jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1432)
>
>                 at
> jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:973)
>
>                 at
> jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:311)
>
>                 at
> jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:170)
>
>                 at
> jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:57)
>
>                 at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:43)
>
>
> If B.java *is* present, we get the expected compilation error:
>
> $ javac C.java
>
> C.java:3: error: method foo in class A<T> cannot be applied to given types;
>
>         a.foo(null);
>
>          ^
>
>   required: no arguments
>
>   found: <null>
>
>   reason: actual and formal argument lists differ in length
>
>   where T is a type-variable:
>
>     T extends B<T> declared in class A
>
> 1 error
>
>
> The repro is (purposely) contrived.  The real case came up when build
> infrastructure prevented the source path of B.java from being observed when
> building C.java.
>
>
> I assume javac shouldn't crash with an NPE, and should instead provide a
> compilation error pointing out that B symbol is not found (or similar).
>
>
> Let me know if you have any questions.
>
>
> Thanks!
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.java.net/pipermail/compiler-dev/attachments/20200323/fce0d968/attachment.htm>