Add lowering on switch in loop

^KT-42262 fixed

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

@@ -341,6 +341,12 @@ private val rangeContainsLoweringPhase = makeBodyLoweringPhase(
     description = "[Optimization] Optimizes calls to contains() for ClosedRanges"
 )
 
+private val loopWithBreakingSwitchLowering = makeBodyLoweringPhase(
+    { LoopWithBreakingSwitchLowering() },
+    name = "LoopWithBreakingSwitchLowering",
+    description = "Transform statement-like-expression nodes into pure-statement to make it easily transform into JS",
+)
+
 private val forLoopsLoweringPhase = makeBodyLoweringPhase(
     ::ForLoopsLowering,
     name = "ForLoopsLowering",
@@ -712,6 +718,7 @@ val loweringList = listOf<Lowering>(
     interopCallableReferenceLoweringPhase,
     returnableBlockLoweringPhase,
     rangeContainsLoweringPhase,
+    loopWithBreakingSwitchLowering,
     forLoopsLoweringPhase,
     primitiveCompanionLoweringPhase,
     propertyAccessorInlinerLoweringPhase,

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

@@ -0,0 +1,51 @@
+/*
+ * 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.BodyLoweringPass
+import org.jetbrains.kotlin.ir.declarations.IrDeclaration
+import org.jetbrains.kotlin.ir.declarations.IrFunction
+import org.jetbrains.kotlin.ir.expressions.IrBody
+import org.jetbrains.kotlin.ir.expressions.IrBreak
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrLoop
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import java.util.*
+
+class LoopWithBreakingSwitchLowering : BodyLoweringPass {
+
+    private val switchInLoopTransformer = LoopWithBreakingSwitchTransformer()
+
+    override fun lower(irBody: IrBody, container: IrDeclaration) {
+        when (container) {
+            is IrFunction -> {
+                container.accept(switchInLoopTransformer, null)
+            }
+        }
+    }
+}
+
+class LoopWithBreakingSwitchTransformer : IrElementTransformerVoid() {
+    private var counter: Int = 0
+
+    private val loopDeque: Deque<IrLoop> = LinkedList()
+
+    override fun visitBreak(jump: IrBreak): IrExpression {
+        val loop = loopDeque.firstOrNull()
+        loop?.label = loop?.label ?: makeLoopLabel()
+
+        return super.visitBreak(jump)
+    }
+
+    override fun visitLoop(loop: IrLoop): IrExpression {
+        loopDeque.push(loop)
+        return super.visitLoop(loop).apply {
+            loopDeque.pop()
+        }
+    }
+
+    private fun makeLoopLabel() = "\$l\$switch\$${counter++}"
+}