JS backend: fix translation when statement -- now WhenTranslator returns JsBlock instead of hackish adding statements to context block.

It fixed the compiler crashing when translating `for`/`when`/`if` with `when` statement(KT-5234) and KT-5058.

 #KT-5234 fixed
 #EA-57346 fixed
 #KT-5058 fixed

js/js.tests/test/org/jetbrains/k2js/test/semantics/MiscTest.java

@@ -190,4 +190,8 @@ public final class MiscTest extends AbstractExpressionTest {
     public void testStringInterpolationEvaluationOrder() throws Exception {
         fooBoxTest();
     }
+
+    public void testKt5058() throws Exception {
+        checkFooBoxIsTrue("KT-5058.kt");
+    }
 }

js/js.tests/test/org/jetbrains/k2js/test/semantics/PatternMatchingTest.java

@@ -89,4 +89,20 @@ public final class PatternMatchingTest extends SingleFileTranslationTest {
     public void testIfInWhen() throws Exception {
         checkFooBoxIsOk();
     }
+
+    public void testForWithOneStmWhen() throws Exception {
+        fooBoxTest();
+    }
+
+    public void testWhileWithOneStmWhen() throws Exception {
+        fooBoxTest();
+    }
+
+    public void testDoWhileWithOneStmWhen() throws Exception {
+        fooBoxTest();
+    }
+
+    public void testIfWithOneStmWhen() throws Exception {
+        fooBoxTest();
+    }
 }

js/js.translator/src/org/jetbrains/k2js/translate/expression/WhenTranslator.java

@@ -40,8 +40,9 @@ public final class WhenTranslator extends AbstractTranslator {
         WhenTranslator translator = new WhenTranslator(expression, context);
 
         if (BindingUtils.isStatement(context.bindingContext(), expression)) {
-            translator.translateAsStatement(context.dynamicContext().jsBlock().getStatements());
-            return null;
+            JsBlock jsBlock = new JsBlock();
+            translator.translateAsStatement(jsBlock.getStatements());
+            return jsBlock;
         }
 
         return translator.translateAsExpression();

js/js.translator/testData/expression/misc/cases/KT-5058.kt

@@ -0,0 +1,25 @@
+package foo
+
+fun test():Any {
+    val a: Any = "OK"
+    val f: Any =
+            if (true) {
+                when {
+                    false -> "1"
+                    ((a as? String)?.size ?: 0 > 0) -> a
+                    else -> "2"
+                }
+            }
+            else {
+                "3"
+
+            }
+
+    return f
+}
+
+fun box(): Boolean {
+    var result = test()
+    return result == "OK";
+}
+

js/js.translator/testData/patternMatching/cases/doWhileWithOneStmWhen.kt

@@ -0,0 +1,15 @@
+package foo
+
+
+fun box(): Boolean {
+    var result = false
+    var i = 1
+    do
+        when (i) {
+            1 ->    result = true
+            else -> result = false
+        }
+    while (i==0)
+    return result;
+}
+

js/js.translator/testData/patternMatching/cases/forWithOneStmWhen.kt

@@ -0,0 +1,13 @@
+package foo
+
+
+fun box(): Boolean {
+    var result = false
+    for (i in array(1))
+        when (i) {
+            1 -> result = true
+            else -> result = false
+        }
+    return result;
+}
+

js/js.translator/testData/patternMatching/cases/ifWithOneStmWhen.kt

@@ -0,0 +1,13 @@
+package foo
+
+
+fun box(): Boolean {
+    var result = false
+    var i = 1
+    if (i==1)
+        when (i) {
+            1 ->    result = true
+            else -> result = false
+        }
+    return result;
+}

js/js.translator/testData/patternMatching/cases/whileWithOneStmWhen.kt

@@ -0,0 +1,14 @@
+package foo
+
+
+fun box(): Boolean {
+    var result = false
+    var i = 1
+    while(i==1)
+        when (i) {
+            1 -> { result = true; break }
+            else -> result = false
+        }
+    return result;
+}
+