[IR] Make descriptor parameter optional for IrFileSymbolImpl and IrExternalPackageFragmentSymbolImpl

Remove DescriptorlessIrFileSymbol and use IrFileSymbolImpl instead.

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MoveBodilessDeclarationsToSeparatePlace.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.
  */
 
@@ -7,16 +7,13 @@ package org.jetbrains.kotlin.ir.backend.js.lower
 
 import org.jetbrains.kotlin.backend.common.DeclarationTransformer
 import org.jetbrains.kotlin.backend.common.ir.addChild
-import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor
 import org.jetbrains.kotlin.ir.IrElement
-import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
 import org.jetbrains.kotlin.ir.backend.js.utils.getJsModule
 import org.jetbrains.kotlin.ir.backend.js.utils.getJsQualifier
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFileImpl
-import org.jetbrains.kotlin.ir.symbols.IrFileSymbol
-import org.jetbrains.kotlin.ir.util.IdSignature
+import org.jetbrains.kotlin.ir.symbols.impl.IrFileSymbolImpl
 import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
 import org.jetbrains.kotlin.ir.util.isEffectivelyExternal
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
@@ -45,28 +42,6 @@ private val BODILESS_BUILTIN_CLASSES = listOf(
     "kotlin.Function"
 ).map { FqName(it) }.toSet()
 
-private class DescriptorlessIrFileSymbol : IrFileSymbol {
-    override fun bind(owner: IrFile) {
-        _owner = owner
-    }
-
-    @ObsoleteDescriptorBasedAPI
-    override val descriptor: PackageFragmentDescriptor
-        get() = error("Operation is unsupported")
-
-    @ObsoleteDescriptorBasedAPI
-    override val hasDescriptor: Boolean
-        get() = error("Operation is unsupported")
-
-    private var _owner: IrFile? = null
-    override val owner get() = _owner!!
-
-    override val isBound get() = _owner != null
-
-    override val signature: IdSignature?
-        get() = null
-}
-
 private fun isBuiltInClass(declaration: IrDeclaration): Boolean =
     declaration is IrClass && declaration.fqNameWhenAvailable in BODILESS_BUILTIN_CLASSES
 
@@ -85,7 +60,7 @@ class MoveBodilessDeclarationsToSeparatePlaceLowering(private val context: JsIrB
 
         val externalPackageFragment by lazy {
             context.externalPackageFragment.getOrPut(irFile.symbol) {
-                IrFileImpl(fileEntry = irFile.fileEntry, fqName = irFile.fqName, symbol = DescriptorlessIrFileSymbol()).also {
+                IrFileImpl(fileEntry = irFile.fileEntry, fqName = irFile.fqName, symbol = IrFileSymbolImpl()).also {
                     it.annotations += irFile.annotations
                 }
             }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/symbols/impl/IrPrivateSymbolBase.kt

@@ -1,17 +1,6 @@
 /*
- * Copyright 2010-2017 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.symbols.impl
@@ -83,11 +72,11 @@ abstract class IrBindableSymbolBase<out D : DeclarationDescriptor, B : IrSymbolO
         get() = _owner != null
 }
 
-class IrFileSymbolImpl(descriptor: PackageFragmentDescriptor) :
+class IrFileSymbolImpl(descriptor: PackageFragmentDescriptor? = null) :
     IrBindableSymbolBase<PackageFragmentDescriptor, IrFile>(descriptor),
     IrFileSymbol
 
-class IrExternalPackageFragmentSymbolImpl(descriptor: PackageFragmentDescriptor) :
+class IrExternalPackageFragmentSymbolImpl(descriptor: PackageFragmentDescriptor? = null) :
     IrBindableSymbolBase<PackageFragmentDescriptor, IrExternalPackageFragment>(descriptor),
     IrExternalPackageFragmentSymbol