diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/DiagnosticFactory.kt b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/DiagnosticFactory.kt
similarity index 52%
rename from compiler/frontend/src/org/jetbrains/kotlin/diagnostics/DiagnosticFactory.kt
rename to compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/DiagnosticFactory.kt
index 9ed41ca5589..7891448b8c9 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/DiagnosticFactory.kt
+++ b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/DiagnosticFactory.kt
@@ -1,25 +1,14 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
+
 package org.jetbrains.kotlin.diagnostics
 
 import org.jetbrains.kotlin.diagnostics.rendering.DiagnosticRenderer
 import java.lang.IllegalArgumentException
-import java.lang.SafeVarargs
 
-abstract class DiagnosticFactory<D : Diagnostic> protected constructor(
+abstract class DiagnosticFactory<D : UnboundDiagnostic> protected constructor(
     open var name: String?,
     open val severity: Severity
 ) {
@@ -28,7 +17,12 @@ abstract class DiagnosticFactory<D : Diagnostic> protected constructor(
 
     protected constructor(severity: Severity) : this(null, severity)
 
-    fun cast(diagnostic: Diagnostic): D {
+    @Suppress("UNCHECKED_CAST")
+    fun initDefaultRenderer(defaultRenderer: DiagnosticRenderer<*>?) {
+        this.defaultRenderer = defaultRenderer as DiagnosticRenderer<D>?
+    }
+
+    fun cast(diagnostic: UnboundDiagnostic): D {
         require(!(diagnostic.factory !== this)) { "Factory mismatch: expected " + this + " but was " + diagnostic.factory }
         @Suppress("UNCHECKED_CAST")
         return diagnostic as D
@@ -40,11 +34,11 @@ abstract class DiagnosticFactory<D : Diagnostic> protected constructor(
 
     companion object {
         @SafeVarargs
-        fun <D : Diagnostic> cast(diagnostic: Diagnostic, vararg factories: DiagnosticFactory<out D>): D {
+        fun <D : UnboundDiagnostic> cast(diagnostic: UnboundDiagnostic, vararg factories: DiagnosticFactory<out D>): D {
             return cast(diagnostic, listOf(*factories))
         }
 
-        fun <D : Diagnostic> cast(diagnostic: Diagnostic, factories: Collection<DiagnosticFactory<out D>>): D {
+        fun <D : UnboundDiagnostic> cast(diagnostic: UnboundDiagnostic, factories: Collection<DiagnosticFactory<out D>>): D {
             for (factory in factories) {
                 if (diagnostic.factory === factory) return factory.cast(diagnostic)
             }
diff --git a/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/Severity.kt b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/Severity.kt
new file mode 100644
index 00000000000..96f3c3e0f12
--- /dev/null
+++ b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/Severity.kt
@@ -0,0 +1,12 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.diagnostics
+
+enum class Severity {
+    INFO,
+    ERROR,
+    WARNING
+}
\ No newline at end of file
diff --git a/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/UnboundDiagnostic.kt b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/UnboundDiagnostic.kt
new file mode 100644
index 00000000000..4b2c70a274d
--- /dev/null
+++ b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/UnboundDiagnostic.kt
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.diagnostics
+
+import com.intellij.openapi.util.TextRange
+
+interface UnboundDiagnostic {
+    val factory: DiagnosticFactory<*>
+    val severity: Severity
+    val textRanges: List<TextRange>
+    val isValid: Boolean
+}
\ No newline at end of file
diff --git a/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRenderer.kt b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRenderer.kt
new file mode 100644
index 00000000000..5e5fba8ff15
--- /dev/null
+++ b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRenderer.kt
@@ -0,0 +1,12 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.diagnostics.rendering
+
+import org.jetbrains.kotlin.diagnostics.UnboundDiagnostic
+
+interface DiagnosticRenderer<in D : UnboundDiagnostic> {
+    fun render(diagnostic: D): String
+}
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Diagnostic.kt b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Diagnostic.kt
index be763ca2c0a..ff1dc5ee0a1 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Diagnostic.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Diagnostic.kt
@@ -15,15 +15,10 @@
  */
 package org.jetbrains.kotlin.diagnostics
 
-import com.intellij.openapi.util.TextRange
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiFile
 
-interface Diagnostic {
-    val factory: DiagnosticFactory<*>
-    val severity: Severity
+interface Diagnostic : UnboundDiagnostic {
     val psiElement: PsiElement
-    val textRanges: List<TextRange>
     val psiFile: PsiFile?
-    val isValid: Boolean
 }
\ No newline at end of file
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Severity.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Severity.java
deleted file mode 100644
index d4ec5534c1a..00000000000
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Severity.java
+++ /dev/null
@@ -1,23 +0,0 @@
-/*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.kotlin.diagnostics;
-
-public enum Severity {
-    INFO,
-    ERROR,
-    WARNING
-}
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRenderer.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRenderer.java
deleted file mode 100644
index 5471c87dae6..00000000000
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRenderer.java
+++ /dev/null
@@ -1,25 +0,0 @@
-/*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.kotlin.diagnostics.rendering;
-
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.kotlin.diagnostics.Diagnostic;
-
-public interface DiagnosticRenderer<D extends Diagnostic> {
-    @NotNull
-    String render(@NotNull D diagnostic);
-}
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt
index 163207c7b84..bf000d0765a 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt
@@ -20,7 +20,7 @@ import org.jetbrains.kotlin.diagnostics.*
 import java.text.MessageFormat
 
 
-abstract class AbstractDiagnosticWithParametersRenderer<D : Diagnostic> protected constructor(message: String) : DiagnosticRenderer<D> {
+abstract class AbstractDiagnosticWithParametersRenderer<in D : Diagnostic> protected constructor(message: String) : DiagnosticRenderer<D> {
     private val messageFormat = MessageFormat(message)
 
     override fun render(diagnostic: D): String {