javac 11.0.6 NullPointerException when a type param refers to missing type

[Vitaly Davidovich]

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!
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