[IR] Simplify IrFileImpl and IrExternalPackageFragment

#KT-65773 In Progress

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/Imports.kt

@@ -1,6 +1,6 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
- * that can be found in the LICENSE file.
+ * Copyright 2010-2024 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.backend.konan.llvm
@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.backend.konan.Context
 import org.jetbrains.kotlin.backend.konan.descriptors.isExpectMember
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.ir.declarations.IrPackageFragment
+import org.jetbrains.kotlin.ir.declarations.moduleDescriptor
 import org.jetbrains.kotlin.library.metadata.CompiledKlibModuleOrigin
 import org.jetbrains.kotlin.library.metadata.SyntheticModulesOrigin
 import org.jetbrains.kotlin.library.metadata.klibModuleOrigin
@@ -17,8 +18,7 @@ private val ModuleDescriptor.llvmSymbolOrigin: CompiledKlibModuleOrigin
     get() {
         assert(!this.isExpectMember) { this }
 
-        val moduleOrigin = klibModuleOrigin
-        when (moduleOrigin) {
+        when (val moduleOrigin = klibModuleOrigin) {
             is CompiledKlibModuleOrigin -> return moduleOrigin
             SyntheticModulesOrigin -> error("Declaration is synthetic and can't be an origin of LLVM symbol:\n${this}")
         }