Fix inheriting docs in case of diamond inheritance

plugins/base/src/main/kotlin/translators/descriptors/DefaultDescriptorToDocumentableTranslator.kt

@@ -1,5 +1,6 @@
 package org.jetbrains.dokka.base.translators.descriptors
 
+import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiNamedElement
 import com.intellij.psi.util.PsiLiteralUtil.*
 import kotlinx.coroutines.Dispatchers
@@ -49,6 +50,7 @@ import org.jetbrains.kotlin.load.java.descriptors.JavaPropertyDescriptor
 import org.jetbrains.kotlin.load.kotlin.toSourceElement
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.calls.components.isVararg
 import org.jetbrains.kotlin.resolve.calls.util.getValueArgumentsInParentheses
@@ -1016,7 +1018,13 @@ private class DokkaDescriptorVisitor(
             org.jetbrains.kotlin.types.Variance.OUT_VARIANCE -> Covariance(this)
         }
 
-    private fun DeclarationDescriptor.getDocumentation() = (findKDoc()?.let {
+    private fun descriptorToAnyDeclaration(descriptor: DeclarationDescriptor): PsiElement? {
+        val effectiveReferencedDescriptors = DescriptorToSourceUtils.getEffectiveReferencedDescriptors(descriptor)
+        //take any
+        return effectiveReferencedDescriptors.firstOrNull()?.let { DescriptorToSourceUtils.getSourceFromDescriptor(it) }
+    }
+
+    private fun DeclarationDescriptor.getDocumentation() = (findKDoc(::descriptorToAnyDeclaration)?.let {
         MarkdownParser.parseFromKDocTag(
             kDocTag = it,
             externalDri = { link: String ->

plugins/base/src/test/kotlin/model/InheritorsTest.kt

@@ -106,15 +106,6 @@ class InheritorsTest : AbstractModelTest("/src/main/kotlin/inheritors/Test.kt",
             }
         }
     }
-    interface A<E> {
-        val a: E
-    }
-
-    open class C
-    class B<E>() : C(), A<E> {
-        override val a: E
-            get() = TODO("Not yet implemented")
-    }
 
     @Test
     fun `should inherit docs`() {
@@ -370,4 +361,54 @@ class InheritorsTest : AbstractModelTest("/src/main/kotlin/inheritors/Test.kt",
             }
         }
     }
+
+    @Test
+    fun `should inherit docs in case of diamond inheritance`() {
+        inlineModelTest(
+            """
+            public interface Collection2<out E>  {
+                /**
+                 * Returns `true` if the collection is empty (contains no elements), `false` otherwise.
+                 */
+                public fun isEmpty(): Boolean
+
+                /**
+                 * Checks if the specified element is contained in this collection.
+                 */
+                public operator fun contains(element: @UnsafeVariance E): Boolean
+            }
+
+            public interface MutableCollection2<E> : Collection2<E>, MutableIterable2<E> 
+
+
+            public interface List2<out E> : Collection2<E> {
+                override fun isEmpty(): Boolean
+                override fun contains(element: @UnsafeVariance E): Boolean
+            }
+
+            public interface MutableList2<E> : List2<E>, MutableCollection2<E>
+
+            public class AbstractMutableList2<E> : MutableList2<E> {
+                protected constructor()
+
+                // From List
+
+                override fun isEmpty(): Boolean = size == 0
+                public override fun contains(element: E): Boolean = indexOf(element) != -1
+            }
+            public class ArrayDeque2<E> : AbstractMutableList2<E> {
+                override fun isEmpty(): Boolean = size == 0
+                public override fun contains(element: E): Boolean = indexOf(element) != -1
+
+            }
+            """.trimMargin()
+        ) {
+            with((this / "inheritors" / "ArrayDeque2" / "isEmpty").cast<DFunction>()) {
+                documentation.size equals 1
+            }
+            with((this / "inheritors" / "ArrayDeque2" / "contains").cast<DFunction>()) {
+                documentation.size equals 1
+            }
+        }
+    }
 }