ADDITIONAL SYSTEM INFORMATION :
Linux Debian buster 64-bit. OpenJDK 13 and Oracle JDK 12. Bug does not occur in my version of Java 11.


A DESCRIPTION OF THE PROBLEM :
NPE in Java Compiler when attempting to compile invalid source code using Java 12 and 13.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
`javac Test.java` with either 13 or 12.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The code is invalid so should not compile. I expect something similar to what Java 11 returns:
```
$ /usr/lib/jvm/jdk-11.0.4/bin/java -version
java version "11.0.4" 2019-07-16 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.4+10-LTS)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.4+10-LTS, mixed mode)
$ /usr/lib/jvm/jdk-11.0.4/bin/javac Test.java
Test.java:5: error: invalid method reference
        function(Test::unknown);
                 ^
  cannot find symbol
    symbol: method unknown()
    location: class Test
1 error
```
ACTUAL -
$ /usr/lib/jvm/jdk-13/bin/java -version
openjdk version "13" 2019-09-17
OpenJDK Runtime Environment (build 13+33)
OpenJDK 64-Bit Server VM (build 13+33, mixed mode, sharing)
$ /usr/lib/jvm/jdk-13/bin/javac Test.java
An exception has occurred in the compiler (13). 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, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
java.lang.NullPointerException
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitApply(Flow.java:1334)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1737)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:405)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.visitExec(TreeScanner.java:218)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1523)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:405)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:57)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitBlock(Flow.java:1083)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1030)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:405)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitMethodDef(Flow.java:1049)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:876)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:405)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitClassDef(Flow.java:1012)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:784)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:405)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.analyzeTree(Flow.java:1427)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.analyzeTree(Flow.java:1417)
        at jdk.compiler/com.sun.tools.javac.comp.Flow.analyzeTree(Flow.java:217)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1406)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1380)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:972)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:318)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:176)
        at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:57)
        at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:43)
$ /usr/lib/jvm/jdk-12.0.2/bin/java -version
java version "12.0.2" 2019-07-16
Java(TM) SE Runtime Environment (build 12.0.2+10)
Java HotSpot(TM) 64-Bit Server VM (build 12.0.2+10, mixed mode, sharing)
$ /usr/lib/jvm/jdk-12.0.2/bin/javac Test.java
An exception has occurred in the compiler (12.0.2). 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.Flow$FlowAnalyzer.visitApply(Flow.java:1304)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1709)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:394)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.visitExec(TreeScanner.java:218)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1519)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:394)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:57)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitBlock(Flow.java:1060)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1026)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:394)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitMethodDef(Flow.java:1027)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:872)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:394)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitClassDef(Flow.java:990)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:780)
        at jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:394)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.analyzeTree(Flow.java:1396)
        at jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.analyzeTree(Flow.java:1386)
        at jdk.compiler/com.sun.tools.javac.comp.Flow.analyzeTree(Flow.java:217)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1401)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1375)
        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)


---------- BEGIN SOURCE ----------
public class Test {

    public static void main(final String... args) {
        function(Test::unknown);
    }

    private static void function(final String parameter) {}

}

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

CUSTOMER SUBMITTED WORKAROUND :
Don't write code that doesn't compile.

FREQUENCY : always