JS backend: fix compiler crash on for with empty body

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

@@ -57,4 +57,12 @@ public final class ForeachTest extends AbstractExpressionTest {
     public void testLabeledForWithWhile() throws Exception {
         checkFooBoxIsOk();
     }
+
+    public void testForWithEmptyBody() throws Exception {
+        checkFooBoxIsOk();
+    }
+
+    public void testForWithSideEffectImElementAccessAndWithEmptyBody() throws Exception {
+        checkFooBoxIsOk();
+    }
 }

js/js.translator/src/org/jetbrains/kotlin/js/translate/expression/LoopTranslator.kt

@@ -29,7 +29,6 @@ import org.jetbrains.kotlin.js.translate.utils.BindingUtils.getIteratorFunction
 import org.jetbrains.kotlin.js.translate.utils.BindingUtils.getNextFunction
 import org.jetbrains.kotlin.js.translate.utils.BindingUtils.getTypeForExpression
 import org.jetbrains.kotlin.js.translate.utils.JsAstUtils.*
-import org.jetbrains.kotlin.js.translate.utils.PsiUtils.getLoopBody
 import org.jetbrains.kotlin.js.translate.utils.PsiUtils.getLoopParameter
 import org.jetbrains.kotlin.js.translate.utils.PsiUtils.getLoopRange
 import org.jetbrains.kotlin.js.translate.utils.TemporariesUtils.temporariesInitialization
@@ -127,8 +126,8 @@ public fun translateForExpression(expression: JetForExpression, context: Transla
 
     val parameterName: JsName = declareParameter()
 
-    fun translateBody(itemValue: JsExpression?): JsStatement {
-        val realBody = Translation.translateAsStatementAndMergeInBlockIfNeeded(getLoopBody(expression), context)
+    fun translateBody(itemValue: JsExpression?): JsStatement? {
+        val realBody = expression.getBody()?.let { Translation.translateAsStatementAndMergeInBlockIfNeeded(it, context) }
         if (itemValue == null && multiParameter == null) {
             return realBody
         }
@@ -138,6 +137,9 @@ public fun translateForExpression(expression: JetForExpression, context: Transla
                     newVar(parameterName, itemValue)
                 else
                     MultiDeclarationTranslator.translate(multiParameter, parameterName, itemValue, context)
+
+            if (realBody == null) return JsBlock(currentVarInit)
+
             val block = convertToBlock(realBody)
             block.getStatements().add(0, currentVarInit)
             return block
@@ -230,7 +232,9 @@ public fun translateForExpression(expression: JetForExpression, context: Transla
         }
 
         context.addStatementToCurrentBlock(iteratorVar.assignmentExpression().makeStmt())
-        return JsWhile(hasNextMethodInvocation(), translateBody(nextMethodInvocation()))
+        val nextInvoke = nextMethodInvocation()
+        val body = translateBody(nextInvoke)
+        return JsWhile(hasNextMethodInvocation(), body ?: nextInvoke.makeStmt())
     }
 
     return when {

js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/PsiUtils.java

@@ -111,13 +111,6 @@ public final class PsiUtils {
         return (binaryExpression.getOperationToken() == JetTokens.IN_KEYWORD);
     }
 
-    @NotNull
-    public static JetExpression getLoopBody(@NotNull JetLoopExpression expression) {
-        JetExpression body = expression.getBody();
-        assert body != null : "Loops cannot have null bodies.";
-        return body;
-    }
-
     @Nullable
     public static JetParameter getLoopParameter(@NotNull JetForExpression expression) {
         return expression.getLoopParameter();

js/js.translator/testData/expression/for/cases/forWithEmptyBody.kt

@@ -0,0 +1,14 @@
+package foo
+
+fun box(): String {
+    for (i in 0..5);
+
+    val r = 0..5
+    for (i in r);
+
+    for (i in arrayOf(1, 2, 3));
+
+    for (i in arrayOf(1, 2, 3).asList());
+
+    return "OK"
+}

js/js.translator/testData/expression/for/cases/forWithSideEffectImElementAccessAndWithEmptyBody.kt

@@ -0,0 +1,45 @@
+package foo
+
+var log = ""
+
+class T(val id: Int) {
+    fun component1(): Int {
+        log += "($id).component1();"
+        return 1
+    }
+    fun component2(): String {
+        log += "($id).component2();"
+        return "1"
+    }
+}
+
+class C {
+    fun iterator(): Iterator<T> = object: Iterator<T> {
+        var i = 0
+        var data = arrayOf(T(3), T(1), T(2))
+        override fun hasNext(): Boolean {
+            log += "C.hasNext();"
+            return i < data.size()
+        }
+
+        override fun next(): T {
+            log += "C.next();"
+            return data[i++]
+        }
+    }
+}
+
+fun box(): String {
+    for ((a, b) in arrayOf(T(3), T(1), T(2)));
+    assertEquals("(3).component1();(3).component2();(1).component1();(1).component2();(2).component1();(2).component2();", log)
+
+
+    log = ""
+    for ((a, b) in C());
+    assertEquals("C.hasNext();C.next();(3).component1();(3).component2();C.hasNext();C.next();" +
+                 "(1).component1();(1).component2();C.hasNext();C.next();" +
+                 "(2).component1();(2).component2();C.hasNext();", log)
+
+    return "OK"
+}
+