Support reflection on @JvmField properties inside class companion

core/reflection.jvm/src/kotlin/reflect/jvm/internal/FunctionCaller.kt

@@ -158,6 +158,21 @@ internal abstract class FunctionCaller<out M : Member>(
         }
     }
 
+    class ClassCompanionFieldGetter(
+            field: ReflectField,
+            klass: Class<*>
+    ) : FunctionCaller<ReflectField>(
+            field,
+            field.genericType,
+            klass,
+            emptyArray()
+    ) {
+        override fun call(args: Array<*>): Any? {
+            checkArguments(args)
+            return member.get(args.first())
+        }
+    }
+
     class StaticFieldSetter(field: ReflectField, notNull: Boolean) : FieldSetter(field, notNull)
 
     class InstanceFieldSetter(field: ReflectField, notNull: Boolean) : FieldSetter(field, notNull)
@@ -168,4 +183,19 @@ internal abstract class FunctionCaller<out M : Member>(
             checkObjectInstance(args.firstOrNull())
         }
     }
+
+    class ClassCompanionFieldSetter(
+            field: ReflectField,
+            klass: Class<*>
+    ) : FunctionCaller<ReflectField>(
+            field,
+            Void.TYPE,
+            klass,
+            arrayOf(field.genericType)
+    ) {
+        override fun call(args: Array<*>): Any? {
+            checkArguments(args)
+            return member.set(instanceClass, args.last())
+        }
+    }
 }

core/reflection.jvm/src/kotlin/reflect/jvm/internal/KPropertyImpl.kt

@@ -18,7 +18,10 @@ package kotlin.reflect.jvm.internal
 
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
+import org.jetbrains.kotlin.load.kotlin.KotlinJvmBinarySourceElement
+import org.jetbrains.kotlin.load.kotlin.reflect.ReflectKotlinClass
 import org.jetbrains.kotlin.resolve.DescriptorFactory
+import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.types.TypeUtils
 import java.lang.reflect.Field
 import java.lang.reflect.Modifier
@@ -86,14 +89,29 @@ internal interface KMutablePropertyImpl<R> : KMutableProperty<R>, KPropertyImpl<
 
 
 private fun KPropertyImpl.Accessor<*>.computeCallerForAccessor(isGetter: Boolean): FunctionCaller<*> {
+    fun isInsideClassCompanionObject(): Boolean {
+        val possibleCompanionObject = property.descriptor.containingDeclaration
+        if (DescriptorUtils.isCompanionObject(possibleCompanionObject) && !DescriptorUtils.isInterface(possibleCompanionObject.containingDeclaration)) {
+            return true
+        }
+        return false
+    }
     fun isJvmStaticProperty() =
             property.descriptor.annotations.findAnnotation(PLATFORM_STATIC) != null ||
             property.descriptor.annotations.findAnnotation(JVM_STATIC) != null
 
+
     fun isNotNullProperty() =
             !TypeUtils.isNullableType(property.descriptor.type)
 
     fun computeFieldCaller(field: Field): FunctionCaller<Field> = when {
+        isInsideClassCompanionObject() -> {
+            val containingDeclaration = descriptor.containingDeclaration as ClassDescriptor
+            val sourceElement = containingDeclaration.source as KotlinJvmBinarySourceElement
+            val klass = (sourceElement.binaryClass as ReflectKotlinClass).klass
+            if (isGetter) FunctionCaller.ClassCompanionFieldGetter(field, klass)
+            else FunctionCaller.ClassCompanionFieldSetter(field, klass)
+        }
         !Modifier.isStatic(field.modifiers) ->
             if (isGetter) FunctionCaller.InstanceFieldGetter(field)
             else FunctionCaller.InstanceFieldSetter(field, isNotNullProperty())