diff --git a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderFirImpl.kt b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderFirImpl.kt
index 80ba2d43f01..57682ec1193 100644
--- a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderFirImpl.kt
+++ b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderFirImpl.kt
@@ -6,14 +6,16 @@
 package org.jetbrains.kotlin.idea.asJava
 
 import com.intellij.psi.*
+import com.intellij.psi.impl.InheritanceImplUtil
 import org.jetbrains.kotlin.asJava.*
 import org.jetbrains.kotlin.asJava.classes.KtLightClass
+import org.jetbrains.kotlin.idea.caches.lightClasses.KtFakeLightClass
+import org.jetbrains.kotlin.idea.caches.lightClasses.KtFakeLightMethod
 import org.jetbrains.kotlin.psi.*
 
 class LightClassProviderFirImpl : LightClassProvider {
-    override fun getLightFieldForCompanionObject(companionObject: KtClassOrObject): PsiField? {
-        return null
-    }
+    override fun getLightFieldForCompanionObject(companionObject: KtClassOrObject): PsiField? =
+        LightClassUtil.getLightFieldForCompanionObject(companionObject)
 
     override fun getLightClassMethods(function: KtFunction): List<PsiMethod> =
         LightClassUtil.getLightClassMethods(function)
@@ -25,7 +27,7 @@ class LightClassProviderFirImpl : LightClassProvider {
         LightClassUtil.getLightClassPropertyMethods(property).allDeclarations
 
     override fun toLightClassWithBuiltinMapping(classOrObject: KtClassOrObject): PsiClass? =
-        null
+        classOrObject.toLightClassWithBuiltinMapping()
 
     override fun toLightMethods(psiElement: PsiElement): List<PsiMethod> =
         psiElement.toLightMethods()
@@ -36,23 +38,20 @@ class LightClassProviderFirImpl : LightClassProvider {
     override fun toLightElements(ktElement: KtElement): List<PsiNamedElement> =
         ktElement.toLightElements()
 
-    override fun createKtFakeLightClass(kotlinOrigin: KtClassOrObject): PsiClass? {
-        return null
-    }
+    override fun createKtFakeLightClass(kotlinOrigin: KtClassOrObject): PsiClass? =
+        KtFakeLightClass(kotlinOrigin)
 
-    override fun getRepresentativeLightMethod(psiElement: PsiElement): PsiMethod? {
-        return null
-    }
+    override fun getRepresentativeLightMethod(psiElement: PsiElement): PsiMethod? =
+        psiElement.getRepresentativeLightMethod()
 
-    override fun isKtFakeLightClass(psiClass: PsiClass): Boolean {
-        return false
-    }
+    override fun isKtFakeLightClass(psiClass: PsiClass): Boolean =
+        psiClass is KtFakeLightClass
 
-    override fun isKtLightClassForDecompiledDeclaration(psiClass: PsiClass): Boolean {
-        return false
-    }
+    override fun isKtLightClassForDecompiledDeclaration(psiClass: PsiClass): Boolean = false //TODO
 
-    override fun createKtFakeLightMethod(ktDeclaration: KtNamedDeclaration): PsiMethod? {
-        return null
-    }
+    override fun createKtFakeLightMethod(ktDeclaration: KtNamedDeclaration): PsiMethod? =
+        KtFakeLightMethod.get(ktDeclaration)
+
+    override fun isFakeLightClassInheritor(ktFakeLightClass: KtFakeLightClass, baseClass: PsiClass, checkDeep: Boolean): Boolean =
+        InheritanceImplUtil.isInheritor(ktFakeLightClass, baseClass, checkDeep)
 }
\ No newline at end of file
diff --git a/idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/asJava/LightClassProvider.kt b/idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/asJava/LightClassProvider.kt
index 9d7f6affab0..443869046f8 100644
--- a/idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/asJava/LightClassProvider.kt
+++ b/idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/asJava/LightClassProvider.kt
@@ -9,6 +9,7 @@ import com.intellij.openapi.components.ServiceManager
 import com.intellij.openapi.project.Project
 import com.intellij.psi.*
 import org.jetbrains.kotlin.asJava.classes.KtLightClass
+import org.jetbrains.kotlin.idea.caches.lightClasses.KtFakeLightClass
 import org.jetbrains.kotlin.psi.*
 
 interface LightClassProvider {
@@ -39,6 +40,8 @@ interface LightClassProvider {
 
     fun createKtFakeLightMethod(ktDeclaration: KtNamedDeclaration): PsiMethod?
 
+    fun isFakeLightClassInheritor(ktFakeLightClass: KtFakeLightClass, baseClass: PsiClass, checkDeep: Boolean): Boolean
+
     companion object {
 
         fun getInstance(project: Project): LightClassProvider {
@@ -83,5 +86,8 @@ interface LightClassProvider {
 
         fun PsiElement.providedGetRepresentativeLightMethod(): PsiMethod? =
             getInstance(project).getRepresentativeLightMethod(this)
+
+        fun KtFakeLightClass.isFakeLightClassInheritor(baseClass: PsiClass, checkDeep: Boolean): Boolean =
+            getInstance(project).isFakeLightClassInheritor(this, baseClass, checkDeep)
     }
 }
\ No newline at end of file
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/lightClasses/KtFakeLightClass.kt b/idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/caches/lightClasses/KtFakeLightClass.kt
similarity index 80%
rename from idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/lightClasses/KtFakeLightClass.kt
rename to idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/caches/lightClasses/KtFakeLightClass.kt
index ab6e1f6416f..0a30b7caacd 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/lightClasses/KtFakeLightClass.kt
+++ b/idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/caches/lightClasses/KtFakeLightClass.kt
@@ -12,17 +12,14 @@ import com.intellij.psi.impl.PsiClassImplUtil
 import com.intellij.psi.impl.light.AbstractLightClass
 import com.intellij.psi.impl.light.LightMethod
 import com.intellij.util.IncorrectOperationException
-import org.jetbrains.kotlin.asJava.ImpreciseResolveResult
 import org.jetbrains.kotlin.asJava.classes.KtLightClass
-import org.jetbrains.kotlin.asJava.classes.LightClassInheritanceHelper
 import org.jetbrains.kotlin.asJava.elements.KtLightElement
 import org.jetbrains.kotlin.idea.KotlinLanguage
-import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
+import org.jetbrains.kotlin.idea.asJava.LightClassProvider.Companion.isFakeLightClassInheritor
 import org.jetbrains.kotlin.load.java.structure.LightClassOriginKind
 import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.KtNamedDeclaration
 import org.jetbrains.kotlin.psi.psiUtil.containingClassOrObject
-import org.jetbrains.kotlin.resolve.DescriptorUtils
 import javax.swing.Icon
 
 // Used as a placeholder when actual light class does not exist (expect-classes, for example)
@@ -48,23 +45,8 @@ class KtFakeLightClass(override val kotlinOrigin: KtClassOrObject) :
     override fun getContainingFile() = kotlinOrigin.containingFile
     override fun getUseScope() = kotlinOrigin.useScope
 
-    override fun isInheritor(baseClass: PsiClass, checkDeep: Boolean): Boolean {
-        if (manager.areElementsEquivalent(baseClass, this)) return false
-        LightClassInheritanceHelper.getService(project).isInheritor(this, baseClass, checkDeep).ifSure { return it }
-
-        val baseKtClass = (baseClass as? KtLightClass)?.kotlinOrigin ?: return false
-        val baseDescriptor = baseKtClass.resolveToDescriptorIfAny() ?: return false
-        val thisDescriptor = kotlinOrigin.resolveToDescriptorIfAny() ?: return false
-
-        val thisFqName = DescriptorUtils.getFqName(thisDescriptor).asString()
-        val baseFqName = DescriptorUtils.getFqName(baseDescriptor).asString()
-        if (thisFqName == baseFqName) return false
-
-        return if (checkDeep)
-            DescriptorUtils.isSubclass(thisDescriptor, baseDescriptor)
-        else
-            DescriptorUtils.isDirectSubclass(thisDescriptor, baseDescriptor)
-    }
+    override fun isInheritor(baseClass: PsiClass, checkDeep: Boolean): Boolean =
+        isFakeLightClassInheritor(baseClass, checkDeep)
 
     override fun isEquivalentTo(another: PsiElement?): Boolean = PsiClassImplUtil.isClassEquivalentTo(this, another)
 }
diff --git a/idea/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderImpl.kt b/idea/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderImpl.kt
index 531f952df3c..6782f070d5c 100644
--- a/idea/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderImpl.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/asJava/LightClassProviderImpl.kt
@@ -8,10 +8,13 @@ package org.jetbrains.kotlin.idea.asJava
 import com.intellij.psi.*
 import org.jetbrains.kotlin.asJava.*
 import org.jetbrains.kotlin.asJava.classes.KtLightClass
+import org.jetbrains.kotlin.asJava.classes.LightClassInheritanceHelper
 import org.jetbrains.kotlin.idea.caches.lightClasses.KtFakeLightClass
 import org.jetbrains.kotlin.idea.caches.lightClasses.KtFakeLightMethod
 import org.jetbrains.kotlin.idea.caches.lightClasses.KtLightClassForDecompiledDeclaration
+import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.resolve.DescriptorUtils
 
 class LightClassProviderImpl : LightClassProvider {
     override fun getLightFieldForCompanionObject(companionObject: KtClassOrObject): PsiField? =
@@ -52,4 +55,22 @@ class LightClassProviderImpl : LightClassProvider {
 
     override fun createKtFakeLightMethod(ktDeclaration: KtNamedDeclaration): PsiMethod? =
         KtFakeLightMethod.get(ktDeclaration)
+
+    override fun isFakeLightClassInheritor(ktFakeLightClass: KtFakeLightClass, baseClass: PsiClass, checkDeep: Boolean): Boolean {
+        if (ktFakeLightClass.manager.areElementsEquivalent(baseClass, ktFakeLightClass)) return false
+        LightClassInheritanceHelper.getService(ktFakeLightClass.project).isInheritor(ktFakeLightClass, baseClass, checkDeep).ifSure { return it }
+
+        val baseKtClass = (baseClass as? KtLightClass)?.kotlinOrigin ?: return false
+        val baseDescriptor = baseKtClass.resolveToDescriptorIfAny() ?: return false
+        val thisDescriptor = ktFakeLightClass.kotlinOrigin.resolveToDescriptorIfAny() ?: return false
+
+        val thisFqName = DescriptorUtils.getFqName(thisDescriptor).asString()
+        val baseFqName = DescriptorUtils.getFqName(baseDescriptor).asString()
+        if (thisFqName == baseFqName) return false
+
+        return if (checkDeep)
+            DescriptorUtils.isSubclass(thisDescriptor, baseDescriptor)
+        else
+            DescriptorUtils.isDirectSubclass(thisDescriptor, baseDescriptor)
+    }
 }
\ No newline at end of file