ADDITIONAL SYSTEM INFORMATION :
System: Ubuntu 22.04, Linux kernel version 6.2.0-39-generic
Javac: javac 21.0.1

A DESCRIPTION OF THE PROBLEM :
When compiling a class which has two local classes (A and B), A captures a variable, B reference A in a static initializer, javac will throw null pointer error.

This is an example:

public class TestUseTree2 {
    public static void main(String[] args) {
        String i = "111";
        class TestUseTree2_ROOT {
            // ctor arg i
            void f() {
                System.out.println(i);
            }
        }

        class TestUseTree2_ROOT1 {
            // clinit args: i?
            // should be prohibited, use `new TestUseTree2_ROOT()` is a static context
            static TestUseTree2_ROOT r = new TestUseTree2_ROOT();
        }

        TestUseTree2_ROOT1.r.f();
    }
}

And javac will throw a null pointer error.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Create a java source file, named "TestUseTree.java", with such content:

```
public class TestUseTree2 {
    public static void main(String[] args) {
        String i = "111";
        class TestUseTree2_ROOT {
            // ctor arg i
            void f() {
                System.out.println(i);
            }
        }

        class TestUseTree2_ROOT1 {
            // clinit args: i?
            // should be prohibited, use `new TestUseTree2_ROOT()` is a static context
            static TestUseTree2_ROOT r = new TestUseTree2_ROOT();
        }

        TestUseTree2_ROOT1.r.f();
    }
}
```

2. Compile with javac, command: `javac TestUseTree.java`

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Javac will report error for `static TestUseTree2_ROOT r = new TestUseTree2_ROOT();`, because TestUseTree2_Root cannot be accessed from a static context.
ACTUAL -
Javac throws a null pointer error:

```
An exception has occurred in the compiler (21.0.1). Please file a bug against the Java compiler via the Java bug reporting page (https://bugreport.java.com) after checking the Bug Database (https://bugs.java.com) for duplicates. Include your program, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
java.lang.NullPointerException: Cannot read field "sym" because "this.lvar[0]" is null
        at jdk.compiler/com.sun.tools.javac.jvm.Code.emitop0(Code.java:568)
        at jdk.compiler/com.sun.tools.javac.jvm.Items$SelfItem.load(Items.java:369)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitIdent(Gen.java:2334)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCIdent.accept(JCTree.java:2715)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:885)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genArgs(Gen.java:910)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitNewClass(Gen.java:2019)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCNewClass.accept(JCTree.java:1871)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:885)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitAssign(Gen.java:2075)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCAssign.accept(JCTree.java:2060)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:885)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitExec(Gen.java:1794)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1603)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:614)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:649)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:635)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStats(Gen.java:686)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.doVisitBlock(Gen.java:1128)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1121)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1092)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:614)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:649)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genMethod(Gen.java:975)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitMethodDef(Gen.java:938)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:916)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:614)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genClass(Gen.java:2472)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.genCode(JavaCompiler.java:769)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1710)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1678)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:976)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:319)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:178)
        at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:64)
        at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:50)
printing javac parameters to: /home/ayanamists/repo/handscript/constructor/javac.20231228_150905.args
```

---------- BEGIN SOURCE ----------
public class TestUseTree2 {
    public static void main(String[] args) {
        String i = "111";
        class TestUseTree2_ROOT {
            // ctor arg i
            void f() {
                System.out.println(i);
            }
        }

        class TestUseTree2_ROOT1 {
            // clinit args: i?
            // should be prohibited, use `new TestUseTree2_ROOT()` is a static context
            static TestUseTree2_ROOT r = new TestUseTree2_ROOT();
        }

        TestUseTree2_ROOT1.r.f();
    }
}
---------- END SOURCE ----------

FREQUENCY : always