Make IrDeclaration#parent a var

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/IrDeclaration.kt

@@ -31,7 +31,7 @@ interface IrDeclaration : IrStatement {
     val declarationKind: IrDeclarationKind
     val origin: IrDeclarationOrigin
 
-    val parent: IrDeclarationParent
+    var parent: IrDeclarationParent
 
     override fun <D> transform(transformer: IrElementTransformer<D>, data: D): IrStatement =
         accept(transformer, data) as IrStatement

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

@@ -49,6 +49,6 @@ class PatchDeclarationParentsVisitor : IrElementVisitorVoid {
     }
 
     private fun patchParent(declaration: IrDeclaration) {
-        (declaration as IrDeclarationBase).parent = declarationParentsStack.peekFirst()
+        declaration.parent = declarationParentsStack.peekFirst()
     }
 }