[IR] add TODO to RenderIrElement

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/RenderIrElement.kt

@@ -1,17 +1,6 @@
 /*
- * Copyright 2010-2016 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.ir.util
@@ -577,6 +566,7 @@ class RenderIrElementVisitor(private val normalizeNames: Boolean = false) : IrEl
     override fun visitSpreadElement(spread: IrSpreadElement, data: Nothing?): String =
         "SPREAD_ELEMENT"
 
+    // TODO do we need a special support for IrReturnableBlock here?
     override fun visitBlock(expression: IrBlock, data: Nothing?): String =
         "BLOCK type=${expression.type.render()} origin=${expression.origin}"