Kotlin: Ensure the kotlin extractor is loaded as the last extension to be able to capture expansions from other extensions

java/kotlin-extractor/src/main/kotlin/KotlinExtractorComponentRegistrar.kt

@@ -4,6 +4,7 @@
 package com.github.codeql
 
 import com.intellij.mock.MockProject
+import com.intellij.openapi.extensions.LoadingOrder
 import org.jetbrains.kotlin.backend.common.extensions.IrGenerationExtension
 import org.jetbrains.kotlin.config.CompilerConfiguration
 
@@ -16,14 +17,18 @@ class KotlinExtractorComponentRegistrar : Kotlin2ComponentRegistrar() {
         if (invocationTrapFile == null) {
             throw Exception("Required argument for TRAP invocation file not given")
         }
-        IrGenerationExtension.registerExtension(
-            project,
+        // Register with LoadingOrder.LAST to ensure the extractor runs after other
+        // IR generation plugins (like kotlinx.serialization) have generated their code.
+        val extensionPoint = project.extensionArea.getExtensionPoint(IrGenerationExtension.extensionPointName)
+        extensionPoint.registerExtension(
             KotlinExtractorExtension(
                 invocationTrapFile,
                 configuration[KEY_CHECK_TRAP_IDENTICAL] ?: false,
                 configuration[KEY_COMPILATION_STARTTIME],
                 configuration[KEY_EXIT_AFTER_EXTRACTION] ?: false
-            )
+            ),
+            LoadingOrder.LAST,
+            project
         )
     }
 }