Use box-impl function as factory for kotlin jvm inline class

Author: wplong11

src/main/java/com/fasterxml/jackson/databind/ext/KotlinSupport.java

@@ -1,6 +1,8 @@
 package com.fasterxml.jackson.databind.ext;
 
 import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
 
 public class KotlinSupport {
     public static boolean isJvmInlineClassSyntheticConstructor(Constructor<?> ctor) {
@@ -12,4 +14,10 @@ public static boolean isJvmInlineClassSyntheticConstructor(Constructor<?> ctor)
         Class<?> lastParam = params[params.length - 1];
         return ctor.isSynthetic() && lastParam.getName().equals("kotlin.jvm.internal.DefaultConstructorMarker");
     }
+
+    public static boolean isJvmInlineClassSyntheticBoxingFunction(Method method) {
+        return Modifier.isStatic(method.getModifiers())
+                && method.isSynthetic()
+                && method.getName().equals("box-impl");
+    }
 }

src/main/java/com/fasterxml/jackson/databind/introspect/AnnotatedCreatorCollector.java

@@ -278,6 +278,10 @@ private List<AnnotatedMethod> _findPotentialFactories(TypeFactory typeFactory,
 
     private static boolean _isIncludableFactoryMethod(Method m)
     {
+        if (KotlinSupport.isJvmInlineClassSyntheticBoxingFunction(m)) {
+            return true;
+        }
+
         return Modifier.isStatic(m.getModifiers())
                 // 09-Nov-2020, ckozak: Avoid considering synthetic methods such as
                 // lambdas used within methods because they're not relevant.