[JS IR BE] process empty loops correctly in BlockDecomposerLowering

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

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.ir.util.transformFlat
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+import org.jetbrains.kotlin.utils.addIfNotNull
 
 class BlockDecomposerLowering(context: JsIrBackendContext) : DeclarationContainerLoweringPass {
 
@@ -265,7 +266,7 @@ class BlockDecomposerTransformer(context: JsIrBackendContext) : IrElementTransfo
                 }
 
                 newLoopBody.statements += JsIrBuilder.buildIfElse(unitType, breakCond, thenBlock)
-                newLoopBody.statements += newBody!!
+                newLoopBody.statements.addIfNotNull(newBody)
 
                 return loop.apply {
                     condition = constTrue
@@ -293,16 +294,22 @@ class BlockDecomposerTransformer(context: JsIrBackendContext) : IrElementTransfo
         // } while (cond)
         //
         override fun visitDoWhileLoop(loop: IrDoWhileLoop): IrExpression {
-            val newBody = loop.body?.transform(statementTransformer, null)!!
+            val newBody = loop.body?.transform(statementTransformer, null)
             val newCondition = loop.condition.transform(expressionTransformer, null)
 
             if (newCondition is IrComposite) {
-                val innerLoop = IrDoWhileLoopImpl(loop.startOffset, loop.endOffset, unitType, loop.origin, newBody, constFalse).apply {
+                val innerLoop = IrDoWhileLoopImpl(loop.startOffset, loop.endOffset, unitType, loop.origin).apply {
+                    condition = constFalse
+                    body = newBody
                     label = makeLoopLabel()
                 }
 
                 val newLoopCondition = newCondition.statements.last() as IrExpression
-                val newLoopBody = IrBlockImpl(newCondition.startOffset, newBody.endOffset, newBody.type).apply {
+                val newLoopBody = IrBlockImpl(
+                    newCondition.startOffset,
+                    newBody?.endOffset ?: newCondition.endOffset,
+                    newBody?.type ?: unitType
+                ).apply {
                     statements += innerLoop
                     statements += newCondition.statements.run { subList(0, lastIndex) }
                 }

compiler/testData/codegen/box/controlStructures/emptyDoWhile.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JS_IR
 fun box(): String {
     do while (false);
 

compiler/testData/codegen/box/controlStructures/emptyWhile.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JS_IR
 fun box(): String {
     while (false);
 

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java

@@ -2149,6 +2149,11 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
                 runTest("js/js.translator/testData/box/expression/evaluationOrder/elvisWithBreakContinueReturn.kt");
             }
 
+            @TestMetadata("emptyLoopWithBreakContinueReturnInCondition.kt")
+            public void testEmptyLoopWithBreakContinueReturnInCondition() throws Exception {
+                runTest("js/js.translator/testData/box/expression/evaluationOrder/emptyLoopWithBreakContinueReturnInCondition.kt");
+            }
+
             @TestMetadata("equalsIntrinsicWithSideEffect.kt")
             public void testEqualsIntrinsicWithSideEffect() throws Exception {
                 runTest("js/js.translator/testData/box/expression/evaluationOrder/equalsIntrinsicWithSideEffect.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/IrBoxJsTestGenerated.java

@@ -2149,6 +2149,11 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
                 runTest("js/js.translator/testData/box/expression/evaluationOrder/elvisWithBreakContinueReturn.kt");
             }
 
+            @TestMetadata("emptyLoopWithBreakContinueReturnInCondition.kt")
+            public void testEmptyLoopWithBreakContinueReturnInCondition() throws Exception {
+                runTest("js/js.translator/testData/box/expression/evaluationOrder/emptyLoopWithBreakContinueReturnInCondition.kt");
+            }
+
             @TestMetadata("equalsIntrinsicWithSideEffect.kt")
             public void testEqualsIntrinsicWithSideEffect() throws Exception {
                 runTest("js/js.translator/testData/box/expression/evaluationOrder/equalsIntrinsicWithSideEffect.kt");

js/js.translator/testData/box/expression/evaluationOrder/emptyLoopWithBreakContinueReturnInCondition.kt

@@ -0,0 +1,49 @@
+// EXPECTED_REACHABLE_NODES: 1236
+package foo
+
+fun whileReturn(): String {
+    var log = ""
+    var i = 0
+    while(if (i<2) { log += "A"; i++; true } else { return log + ":whileReturn:"});
+    return ":whileReturn:after:"
+}
+
+fun whileImmediateReturn(): String {
+    while(return ":whileImmediateReturn:") {
+    }
+    return ":whileImmediateReturn:after"
+}
+
+fun doWhileReturn(): String {
+    var log = ""
+    var i = 0
+    do while(if (i<2) { log += "A"; i++; true} else { return log + ":doWhileReturn:"})
+    return ":doWhileReturn:after:"
+}
+
+fun doWhileReturnFromCondition(): String {
+    do {
+    } while(return ":doWhileReturnFromCondition:")
+    return ":doWhileReturnFromCondition:after"
+}
+
+fun forReturn(b: Boolean): String {
+    for(i in (if (b) 1..2 else { return ":forReturn:"}));
+    return ":forReturn:after:"
+}
+
+fun box(): String {
+    assertEquals("AA:whileReturn:", whileReturn())
+
+    assertEquals(":whileImmediateReturn:", whileImmediateReturn())
+
+    assertEquals("AA:doWhileReturn:", doWhileReturn())
+
+    assertEquals(":doWhileReturnFromCondition:", doWhileReturnFromCondition())
+
+    assertEquals(":forReturn:after:", forReturn(true))
+
+    assertEquals(":forReturn:", forReturn(false))
+
+    return "OK"
+}