[BUG] Invalid com.sun.source.tree.LiteralTree generated by lombok?

[mattiasgronlund]

Describe the bug
When lombok executes as an annotation processor it seems like it produces invalid code.

To Reproduce
At the end of the report, there is a command to extract source.tgz which contains a maven project which shows the problem.

The following sequence should fail:

$ tar zxvf source.tgz
$ mvn compile 
...
The Checker Framework crashed
...
Exception: java.lang.ClassCastException: class java.lang.Integer cannot be cast to class java.lang.Void (java.lang.Integer and java.lang.Void are in module java.base of loader 'bootstrap'); java.lang.ClassCastException: class java.lang.Integer cannot be cast to class java.lang.Void (java.lang.Integer and java.lang.Void are in module java.base of loader 'bootstrap')
...

But if we move the source the compilation will work:

$ mv src/main/java/test src/main/lombok/
$ mvn compile 
...
BUILD SUCCESS
...

Expected behavior
The expected behavior is that both cases above should work.

Version info (please complete the following information):

• Lombok version: 1.18.16.0
• Platform: javac -version => javac 11.0.8
• Checker framework 3.8.0

Additional context
I have not been able to create a smaller crashing example, I have no clue why the interface and derived types are needed, but I think the @Singular is the root for this problem as the build() method get a lot more complex when @Singular is added (and if I remove it, the problems go away).

I have investigated the crash in checkerframework and got a workaround running, but I get the feeling that this is really a lombok problem.

The workaround in checkerframework is:

diff --git a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/node/NullLiteralNode.java b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/node/NullLiteralNode.java
index 18206dde1..e9596c791 100644
--- a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/node/NullLiteralNode.java
+++ b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/node/NullLiteralNode.java
@@ -27,7 +27,19 @@ public class NullLiteralNode extends ValueLiteralNode {
 
     @Override
     public Void getValue() {
-        return (Void) tree.getValue();
+        Object value = tree.getValue();
+        if (value instanceof Void) {
+
+            return (Void) value;
+        }
+
+        if (value instanceof java.lang.Integer) {
+            System.out.printf("Expected a java.lang.Void value, as type is %s but it has a %s value: %s%n",
+                              tree.getKind(),
+                              value.getClass().getCanonicalName(),
+                              value == null ? "null" : value.toString());
+        }
+        return (Void) null;
     }
 
     @Override

With this patch added the failing build succeeds but outputs:

...
Expected a java.lang.Void value, as type is NULL_LITERAL but it has a java.lang.Integer value: 0
Expected a java.lang.Void value, as type is NULL_LITERAL but it has a java.lang.Integer value: 0
Expected a java.lang.Void value, as type is NULL_LITERAL but it has a java.lang.Integer value: 0
...

Why do I think this is a lombok problem?
For me it seems very strange that checker framework manage to get its hands on a LiteralTree instance which has the kind NULL_LITERAL, which value isn't (Void) null, but instead an (Integer) 0.

Command to extract source.tgz:

base64 -d /tmp/b < <(cat << END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2dcPk/az5La1rW1ta1vb2ta2trWtbW1rW9vi9j8KETvHAFAAAA==
END
) > source.tgz

[Rawi01]

Can confirm that this is broken, already identified the root cause and will provide a PR soon. I also don't get why the unreferenced interface is required, thats fascinating 😄

Btw you can also upload files to github, that base64 encode archive was a little bit strange 😄

[mattiasgronlund]

Thanks for the extremely quick support!

Sorry for the strange archive, I must have been a bit to focused on the lombok problem to realize that it could be as simple as drag and drop to add an attachment, I saw the Video support, and just didn't read the full line😄.