JVM IR: add jvmLocalClassExtractionPhase to lift out local classes from initializers

Otherwise a local class in a field initializer or anonymous init block
is copied into each constructor of the containing class (because
InitializersLowering calls deepCopy).

Since the code structure no longer resembles the original source code
here, record a custom EnclosingMethod mapping before moving such
classes, and use it in codegen.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/LocalClassPopupLowering.kt

@@ -1,8 +1,14 @@
+/*
+ * Copyright 2010-2019 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.common.lower
 
 import org.jetbrains.kotlin.backend.common.BackendContext
 import org.jetbrains.kotlin.backend.common.FileLoweringPass
 import org.jetbrains.kotlin.backend.common.IrElementTransformerVoidWithContext
+import org.jetbrains.kotlin.backend.common.ScopeWithIr
 import org.jetbrains.kotlin.backend.common.ir.addChild
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.declarations.IrClass
@@ -12,8 +18,7 @@ import org.jetbrains.kotlin.ir.declarations.IrScript
 import org.jetbrains.kotlin.ir.expressions.impl.IrCompositeImpl
 
 //This lower takes part of old LocalDeclarationLowering job to pop up local classes from functions
-class LocalClassPopupLowering(val context: BackendContext) : FileLoweringPass {
-
+open class LocalClassPopupLowering(val context: BackendContext) : FileLoweringPass {
     override fun lower(irFile: IrFile) {
         val extractedLocalClasses = arrayListOf<Pair<IrClass, IrDeclarationContainer>>()
 
@@ -21,9 +26,10 @@ class LocalClassPopupLowering(val context: BackendContext) : FileLoweringPass {
 
             override fun visitClassNew(declaration: IrClass): IrStatement {
                 val newDeclaration = super.visitClassNew(declaration)
-                if (newDeclaration !is IrClass || !newDeclaration.isLocalNotInner()) {
-                    return newDeclaration
-                }
+                if (newDeclaration !is IrClass) return newDeclaration
+
+                val currentScope = allScopes[allScopes.lastIndex - 1]
+                if (!shouldPopUp(declaration, currentScope)) return newDeclaration
 
                 val newContainer = allScopes.asReversed().drop(1/*skip self*/).firstOrNull {
                     //find first class local or not;
@@ -39,4 +45,7 @@ class LocalClassPopupLowering(val context: BackendContext) : FileLoweringPass {
             newContainer.addChild(local)
         }
     }
-}
+
+    protected open fun shouldPopUp(klass: IrClass, currentScope: ScopeWithIr?): Boolean =
+        klass.isLocalNotInner()
+}