From 2b838d1ea63b04674bde6a26c71de03e5647d0b3 Mon Sep 17 00:00:00 2001
From: Jack Conradson <osjdconrad@gmail.com>
Date: Tue, 6 Oct 2020 15:58:23 -0700
Subject: [PATCH] fix expression type for null safe operator (#63367)

An invalid void expression type from a null safe operator caused ClassFormatError for the script Map
x= ['0': 0]; x?.0 > 1. This change sets and propagates the correct expression type for the null safe
operator to be written out.
---
 .../painless/phase/DefaultUserTreeToIRTreePhase.java           | 3 ++-
 .../src/test/java/org/elasticsearch/painless/ElvisTests.java   | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultUserTreeToIRTreePhase.java b/modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultUserTreeToIRTreePhase.java
index 254faccb326..abecf1ac88e 100644
--- a/modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultUserTreeToIRTreePhase.java
+++ b/modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultUserTreeToIRTreePhase.java
@@ -436,15 +436,16 @@ public class DefaultUserTreeToIRTreePhase implements UserTreeVisitor<ScriptScope
             if (irIndexNode != null) {
                 // this load/store requires an index
                 BinaryImplNode binaryImplNode = new BinaryImplNode(location);
-                binaryImplNode.setExpressionType(void.class);
 
                 if (isNullSafe) {
                     // the null-safe structure is slightly different from the standard structure since
                     // both the index and expression are not written to the stack if the prefix is null
+                    binaryImplNode.setExpressionType(irExpressionNode.getExpressionType());
                     binaryImplNode.setLeftNode(irIndexNode);
                     binaryImplNode.setRightNode(irExpressionNode);
                     irExpressionNode = binaryImplNode;
                 } else {
+                    binaryImplNode.setExpressionType(void.class);
                     binaryImplNode.setLeftNode(irPrefixNode);
                     binaryImplNode.setRightNode(irIndexNode);
                     irPrefixNode = binaryImplNode;
diff --git a/modules/lang-painless/src/test/java/org/elasticsearch/painless/ElvisTests.java b/modules/lang-painless/src/test/java/org/elasticsearch/painless/ElvisTests.java
index da0822c8f75..b788cf7f7dd 100644
--- a/modules/lang-painless/src/test/java/org/elasticsearch/painless/ElvisTests.java
+++ b/modules/lang-painless/src/test/java/org/elasticsearch/painless/ElvisTests.java
@@ -75,6 +75,8 @@ public class ElvisTests extends ScriptTestCase {
     }
 
     public void testWithNullSafeDereferences() {
+        assertEquals(false, exec("Map x = ['0': 0]; x?.0 > 5.0"));
+        assertEquals(false, exec("List x = [0]; x?.0 > 5.0"));
         assertEquals(1, exec("return params.a?.b ?: 1"));
         assertEquals(1, exec("return params.a?.b ?: 2", singletonMap("a", singletonMap("b", 1)), true));