From 065aef581d57e227ff32e866326c4b4a7c9956be Mon Sep 17 00:00:00 2001
From: Alexey Andreev <konsoletyper@gmail.com>
Date: Mon, 12 Aug 2024 17:32:54 +0200
Subject: [PATCH] jso: fix incorrect type inference for array element types

Fix #937
---
 .../java/org/teavm/jso/impl/JSTypeInference.java   |  3 +++
 tests/src/test/java/org/teavm/vm/VMTest.java       | 14 ++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/jso/impl/src/main/java/org/teavm/jso/impl/JSTypeInference.java b/jso/impl/src/main/java/org/teavm/jso/impl/JSTypeInference.java
index 4985a5b49..81a8412b2 100644
--- a/jso/impl/src/main/java/org/teavm/jso/impl/JSTypeInference.java
+++ b/jso/impl/src/main/java/org/teavm/jso/impl/JSTypeInference.java
@@ -82,6 +82,9 @@ class JSTypeInference extends BaseTypeInference<JSType> {
 
     @Override
     protected JSType elementType(JSType jsType) {
+        if (jsType == JSType.NULL) {
+            return JSType.NULL;
+        }
         return jsType instanceof JSType.ArrayType ? ((JSType.ArrayType) jsType).elementType : JSType.MIXED;
     }
 
diff --git a/tests/src/test/java/org/teavm/vm/VMTest.java b/tests/src/test/java/org/teavm/vm/VMTest.java
index 69f4b72ad..c075b9829 100644
--- a/tests/src/test/java/org/teavm/vm/VMTest.java
+++ b/tests/src/test/java/org/teavm/vm/VMTest.java
@@ -657,6 +657,20 @@ public class VMTest {
         assertEquals("ap", callA(new B()));
     }
 
+    @Test
+    public void typeInferenceForArrayMerge() {
+        int[][] a = falseBoolean() ? null : array();
+        assertEquals(23, a[0][0]);
+    }
+
+    private boolean falseBoolean() {
+        return false;
+    }
+
+    private int[][] array() {
+        return new int[][] { { 23 } };
+    }
+
     private static String callA(A a) {
         return a.a();
     }