[JS IR] Add init function for properties

^KT-43222 fixed

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt

@@ -109,6 +109,16 @@ class ModuleLowering(
     override val modulePhase: NamedCompilerPhase<JsIrBackendContext, Iterable<IrModuleFragment>>
 ) : Lowering(name)
 
+class FileLowering(
+    name: String,
+    description: String,
+    prerequisite: Set<NamedCompilerPhase<JsIrBackendContext, *>> = emptySet(),
+    private val factory: (JsIrBackendContext) -> FileLoweringPass
+) : Lowering(name) {
+    override val modulePhase: NamedCompilerPhase<JsIrBackendContext, Iterable<IrModuleFragment>> =
+        makeJsModulePhase(factory, name, description, prerequisite)
+}
+
 private fun makeDeclarationTransformerPhase(
     lowering: (JsIrBackendContext) -> DeclarationTransformer,
     name: String,
@@ -123,6 +133,13 @@ private fun makeBodyLoweringPhase(
     prerequisite: Set<Lowering> = emptySet()
 ) = BodyLowering(name, description, prerequisite.map { it.modulePhase }.toSet(), lowering)
 
+private fun makeFileLoweringPhase(
+    lowering: (JsIrBackendContext) -> FileLoweringPass,
+    name: String,
+    description: String,
+    prerequisite: Set<Lowering> = emptySet()
+) = FileLowering(name, description, prerequisite.map { it.modulePhase }.toSet(), lowering)
+
 fun NamedCompilerPhase<JsIrBackendContext, Iterable<IrModuleFragment>>.toModuleLowering() = ModuleLowering(this.name, this)
 
 private val validateIrBeforeLowering = makeCustomJsModulePhase(
@@ -352,6 +369,12 @@ private val forLoopsLoweringPhase = makeBodyLoweringPhase(
     description = "[Optimization] For loops lowering"
 )
 
+private val propertyLazyInitLoweringPhase = makeFileLoweringPhase(
+    ::PropertyLazyInitLowering,
+    name = "PropertyLazyInitLowering",
+    description = "Make property init as lazy"
+)
+
 private val propertyAccessorInlinerLoweringPhase = makeBodyLoweringPhase(
     ::PropertyAccessorInlineLowering,
     name = "PropertyAccessorInlineLowering",
@@ -727,6 +750,7 @@ val loweringList = listOf<Lowering>(
     rangeContainsLoweringPhase,
     forLoopsLoweringPhase,
     primitiveCompanionLoweringPhase,
+    propertyLazyInitLoweringPhase,
     propertyAccessorInlinerLoweringPhase,
     foldConstantLoweringPhase,
     privateMembersLoweringPhase,

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

@@ -0,0 +1,102 @@
+/*
+ * 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.backend.js.lower
+
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.ir.IrStatement
+import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
+import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
+import org.jetbrains.kotlin.ir.backend.js.ir.JsIrBuilder
+import org.jetbrains.kotlin.ir.builders.declarations.addFunction
+import org.jetbrains.kotlin.ir.declarations.IrField
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
+import org.jetbrains.kotlin.ir.expressions.IrBody
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrFieldAccessExpression
+import org.jetbrains.kotlin.ir.expressions.IrSetField
+import org.jetbrains.kotlin.ir.expressions.impl.IrSetFieldImpl
+import org.jetbrains.kotlin.ir.util.kotlinFqName
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+import org.jetbrains.kotlin.name.Name
+
+class PropertyLazyInitLowering(private val context: JsIrBackendContext) : FileLoweringPass {
+    private val irBuiltIns
+        get() = context.irBuiltIns
+
+    override fun lower(irFile: IrFile) {
+        val initializers = PropertyInitializerMover(context).process(irFile)
+        val irFactory = context.irFactory
+        if (initializers.isNotEmpty()) {
+            irFactory.addFunction(irFile) {
+                name = Name.identifier("init properties ${irFile.kotlinFqName}")
+                returnType = irBuiltIns.unitType
+                origin = JsIrBuilder.SYNTHESIZED_DECLARATION
+            }.apply {
+                body = irFactory.createBlockBody(
+                    UNDEFINED_OFFSET,
+                    UNDEFINED_OFFSET,
+                    initializers
+                        .map { (field, expression) ->
+                            createIrSetField(field, expression)
+                        }
+                )
+            }
+        }
+    }
+
+    private fun createIrSetField(field: IrField, expression: IrExpression): IrSetField {
+        return IrSetFieldImpl(
+            field.startOffset,
+            field.endOffset,
+            field.symbol,
+            null,
+            expression,
+            expression.type
+        )
+    }
+}
+
+private class PropertyInitializerMover(
+    private val context: JsIrBackendContext
+) : IrElementTransformerVoid() {
+
+    private val fieldToInitializers = mutableListOf<Pair<IrField, IrExpression>>()
+
+    fun process(irFile: IrFile): List<Pair<IrField, IrExpression>> {
+        irFile.transformChildrenVoid(this)
+        return fieldToInitializers
+    }
+
+    override fun visitSimpleFunction(declaration: IrSimpleFunction): IrStatement {
+        declaration.correspondingPropertySymbol
+            ?.owner
+            ?.takeIf { !it.isConst }
+            ?.takeIf { !it.isDelegated }
+            ?.backingField
+            ?.takeIf { it.initializer != null }
+            ?.let { field ->
+                fieldToInitializers.add(field to field.initializer!!.expression)
+            }
+
+        fieldToInitializers.forEach { it.first.initializer = null }
+
+        return super.visitSimpleFunction(declaration)
+    }
+
+    override fun visitFieldAccess(expression: IrFieldAccessExpression): IrExpression {
+        return super.visitFieldAccess(expression)
+    }
+
+    override fun visitField(declaration: IrField): IrStatement {
+        return super.visitField(declaration)
+    }
+
+    override fun visitBody(body: IrBody): IrBody {
+        return super.visitBody(body)
+    }
+}