[IR] [JS_IR] Supported fun interfaces in JS

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/ir/IrUtils.kt

@@ -415,7 +415,7 @@ fun IrClass.createImplicitParameterDeclarationWithWrappedDescriptor() {
         startOffset, endOffset,
         IrDeclarationOrigin.INSTANCE_RECEIVER,
         IrValueParameterSymbolImpl(thisReceiverDescriptor),
-        Name.identifier("<this>"),
+        Name.special("<this>"),
         index = -1,
         type = symbol.typeWithParameters(typeParameters),
         varargElementType = null,

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

@@ -65,6 +65,8 @@ abstract class SingleAbstractMethodLowering(val context: CommonBackendContext) :
     abstract fun getSuperTypeForWrapper(typeOperand: IrType): IrType
 
     override fun lower(irFile: IrFile) {
+        cachedImplementations.clear()
+        inlineCachedImplementations.clear()
         enclosingContainer = irFile.declarations.filterIsInstance<IrClass>().find { it.isFileClass }
             ?: irFile
         irFile.transformChildrenVoid()

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

@@ -475,11 +475,21 @@ private val bridgesConstructionPhase = makeDeclarationTransformerPhase(
     prerequisite = setOf(suspendFunctionsLoweringPhase)
 )
 
+private val singleAbstractMethodPhase = makeIrModulePhase(
+    ::JsSingleAbstractMethodLowering,
+    name = "SingleAbstractMethod",
+    description = "Replace SAM conversions with instances of interface-implementing classes"
+).toModuleLowering()
+
 private val typeOperatorLoweringPhase = makeBodyLoweringPhase(
     ::TypeOperatorLowering,
     name = "TypeOperatorLowering",
     description = "Lower IrTypeOperator with corresponding logic",
-    prerequisite = setOf(bridgesConstructionPhase, removeInlineFunctionsWithReifiedTypeParametersLoweringPhase)
+    prerequisite = setOf(
+        bridgesConstructionPhase,
+        removeInlineFunctionsWithReifiedTypeParametersLoweringPhase,
+        singleAbstractMethodPhase
+    )
 )
 
 private val secondaryConstructorLoweringPhase = makeDeclarationTransformerPhase(
@@ -580,6 +590,7 @@ val loweringList = listOf<Lowering>(
     copyInlineFunctionBodyLoweringPhase,
     createScriptFunctionsPhase,
     provisionalFunctionExpressionPhase,
+    singleAbstractMethodPhase,
     lateinitNullableFieldsPhase,
     lateinitDeclarationLoweringPhase,
     lateinitUsageLoweringPhase,

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

@@ -0,0 +1,22 @@
+/*
+ * 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.lower.SingleAbstractMethodLowering
+import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
+import org.jetbrains.kotlin.ir.types.IrType
+import org.jetbrains.kotlin.ir.types.classOrNull
+import org.jetbrains.kotlin.ir.types.defaultType
+import org.jetbrains.kotlin.ir.util.render
+
+class JsSingleAbstractMethodLowering(context: JsIrBackendContext) : SingleAbstractMethodLowering(context) {
+    override fun getSuperTypeForWrapper(typeOperand: IrType): IrType {
+        // FE doesn't allow type parameters for now.
+        // And since there is a to-do in common SingleAbstractMethodLowering (at function visitTypeOperator),
+        // we don't have to be more saint than a pope here.
+        return typeOperand.classOrNull?.defaultType ?: error("Unsupported SAM conversion: ${typeOperand.render()}")
+    }
+}

compiler/testData/codegen/box/funInterface/basicFunInterfaceConversion.kt

@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference +FunctionalInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JS, JS_IR
+// IGNORE_BACKEND: JS
+// SKIP_DCE_DRIVEN
 
 fun interface Foo {
     fun invoke(): String

compiler/testData/codegen/box/funInterface/nullableSam.kt

@@ -1,7 +1,8 @@
 // !LANGUAGE: +NewInference +FunctionalInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JS, JS_IR
+// IGNORE_BACKEND: JS
 // WITH_RUNTIME
+// SKIP_DCE_DRIVEN
 
 fun interface KRunnable {
     fun invoke()

compiler/testData/codegen/box/funInterface/partialSam.kt

@@ -1,7 +1,8 @@
 // !LANGUAGE: +NewInference +FunctionalInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JS, JS_IR
+// IGNORE_BACKEND: JS
 // WITH_RUNTIME
+// SKIP_DCE_DRIVEN
 
 fun interface Fn<T, R> {
     fun run(s: String, i: Int, t: T): R

compiler/testData/codegen/box/funInterface/receiverEvaluatedOnce.kt

@@ -1,7 +1,8 @@
 // !LANGUAGE: +NewInference +FunctionalInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JS, JS_IR
+// IGNORE_BACKEND: JS
 // WITH_RUNTIME
+// SKIP_DCE_DRIVEN
 
 fun interface KRunnable {
     fun invoke()