[JS IR BE] ExpectDeclarationsRemoving lowering

* Copy lowering from konan to common
* Keep actual default parameters when both actual and expect default parameters are present
* Run lowering before inline in JS IR BE to fix
  box/multiplatform/defaultArguments/inlineFunctionWithDefaultLambda.kt

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

@@ -0,0 +1,143 @@
+/*
+ * 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/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.descriptors.MemberDescriptor
+import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrGetValue
+import org.jetbrains.kotlin.ir.expressions.impl.IrGetValueImpl
+import org.jetbrains.kotlin.ir.symbols.IrValueParameterSymbol
+import org.jetbrains.kotlin.ir.symbols.IrValueSymbol
+import org.jetbrains.kotlin.ir.util.referenceFunction
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
+import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
+import org.jetbrains.kotlin.ir.visitors.acceptVoid
+import org.jetbrains.kotlin.resolve.checkers.ExpectedActualDeclarationChecker
+import org.jetbrains.kotlin.resolve.descriptorUtil.module
+import org.jetbrains.kotlin.resolve.multiplatform.ExpectedActualResolver
+
+/**
+ * This pass removes all declarations with `isExpect == true`.
+ */
+class ExpectDeclarationsRemoving(val context: BackendContext) : FileLoweringPass {
+
+    override fun lower(irFile: IrFile) {
+        // All declarations with `isExpect == true` are nested into a top-level declaration with `isExpect == true`.
+        irFile.declarations.removeAll {
+            val descriptor = it.descriptor
+            if (descriptor is MemberDescriptor && descriptor.isExpect) {
+                copyDefaultArgumentsFromExpectToActual(it)
+                true
+            } else {
+                false
+            }
+        }
+    }
+
+    private fun copyDefaultArgumentsFromExpectToActual(declaration: IrDeclaration) {
+        declaration.acceptVoid(object : IrElementVisitorVoid {
+            override fun visitElement(element: IrElement) {
+                element.acceptChildrenVoid(this)
+            }
+
+            override fun visitValueParameter(declaration: IrValueParameter) {
+                super.visitValueParameter(declaration)
+
+                val defaultValue = declaration.defaultValue ?: return
+                val function = declaration.parent as IrFunction
+
+                val index = declaration.index
+                assert(function.valueParameters[index] == declaration)
+
+                if (function is IrConstructor &&
+                    ExpectedActualDeclarationChecker.isOptionalAnnotationClass(
+                        function.descriptor.constructedClass
+                    )
+                ) {
+                    return
+                }
+
+                val actualParameter = function.findActualForExpected().valueParameters[index]
+
+                // Keep actual default value if present. They are generally not allowed but can be suppressed with
+                // @Suppress("ACTUAL_FUNCTION_WITH_DEFAULT_ARGUMENTS")
+                if (actualParameter.defaultValue != null)
+                    return
+
+                actualParameter.defaultValue = defaultValue.also {
+                    it.expression = it.expression.remapExpectValueSymbols()
+                }
+            }
+        })
+    }
+
+    private fun IrFunction.findActualForExpected(): IrFunction =
+        context.ir.symbols.externalSymbolTable.referenceFunction(descriptor.findActualForExpect()).owner
+
+    private fun IrClass.findActualForExpected(): IrClass =
+        context.ir.symbols.externalSymbolTable.referenceClass(descriptor.findActualForExpect()).owner
+
+    private inline fun <reified T : MemberDescriptor> T.findActualForExpect() = with(ExpectedActualResolver) {
+        val descriptor = this@findActualForExpect
+
+        if (!descriptor.isExpect) error(this)
+
+        findCompatibleActualForExpected(descriptor.module).singleOrNull() ?: error(descriptor)
+    } as T
+
+    private fun IrExpression.remapExpectValueSymbols(): IrExpression {
+        return this.transform(object : IrElementTransformerVoid() {
+
+            override fun visitGetValue(expression: IrGetValue): IrExpression {
+                expression.transformChildrenVoid()
+                val newValue = remapExpectValue(expression.symbol)
+                    ?: return expression
+
+                return IrGetValueImpl(
+                    expression.startOffset,
+                    expression.endOffset,
+                    newValue.type,
+                    newValue.symbol,
+                    expression.origin
+                )
+            }
+        }, data = null)
+    }
+
+    private fun remapExpectValue(symbol: IrValueSymbol): IrValueParameter? {
+        if (symbol !is IrValueParameterSymbol) {
+            return null
+        }
+
+        val parameter = symbol.owner
+        val parent = parameter.parent
+
+        return when (parent) {
+            is IrClass -> {
+                assert(parameter == parent.thisReceiver)
+                parent.findActualForExpected().thisReceiver!!
+            }
+
+            is IrFunction -> when (parameter) {
+                parent.dispatchReceiverParameter ->
+                    parent.findActualForExpected().dispatchReceiverParameter!!
+                parent.extensionReceiverParameter ->
+                    parent.findActualForExpected().extensionReceiverParameter!!
+                else -> {
+                    assert(parent.valueParameters[parameter.index] == parameter)
+                    parent.findActualForExpected().valueParameters[parameter.index]
+                }
+            }
+
+            else -> error(parent)
+        }
+    }
+}

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

@@ -76,6 +76,8 @@ fun compile(
 
     MoveExternalDeclarationsToSeparatePlace().lower(moduleFragment.files)
 
+    moduleFragment.files.forEach(ExpectDeclarationsRemoving(context)::lower)
+
     moduleFragment.files.forEach(CoroutineIntrinsicLowering(context)::lower)
     moduleFragment.files.forEach { ArrayInlineConstructorLowering(context).lower(it) }
 

compiler/testData/codegen/box/multiplatform/defaultArguments/constructor.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +MultiPlatformProjects
-// IGNORE_BACKEND: JS_IR
 // IGNORE_BACKEND: JVM_IR
 // WITH_RUNTIME
 // FILE: common.kt

compiler/testData/codegen/box/multiplatform/defaultArguments/function.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +MultiPlatformProjects
-// IGNORE_BACKEND: JS_IR
 // IGNORE_BACKEND: JVM_IR
 // WITH_RUNTIME
 // FILE: common.kt

compiler/testData/codegen/box/multiplatform/defaultArguments/inheritedFromExpectedClass.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +MultiPlatformProjects
-// IGNORE_BACKEND: JS_IR
 // IGNORE_BACKEND: JVM_IR
 // WITH_RUNTIME
 // FILE: common.kt

compiler/testData/codegen/box/multiplatform/defaultArguments/inheritedFromExpectedMethod.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +MultiPlatformProjects
-// IGNORE_BACKEND: JS_IR
 // WITH_RUNTIME
 // IGNORE_BACKEND: JVM_IR
 // FILE: common.kt

compiler/testData/codegen/box/multiplatform/defaultArguments/inheritedInExpectedDeclarations.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +MultiPlatformProjects
-// IGNORE_BACKEND: JS_IR
 // WITH_RUNTIME
 // IGNORE_BACKEND: JVM_IR
 // FILE: common.kt

compiler/testData/codegen/box/multiplatform/defaultArguments/inlineFunctionWithDefaultLambda.kt

@@ -1,6 +1,5 @@
 // !LANGUAGE: +MultiPlatformProjects
 // IGNORE_BACKEND: JVM_IR
-// IGNORE_BACKEND: JS_IR
 // WITH_RUNTIME
 // FILE: common.kt
 

compiler/testData/codegen/box/multiplatform/defaultArguments/kt23239.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +MultiPlatformProjects
-// IGNORE_BACKEND: JS_IR
 // WITH_RUNTIME
 // IGNORE_BACKEND: JVM_IR
 // FILE: common.kt