Fix for KT-5995: Labeled val causes an exception from the back-end

#KT-5995 Fixed

compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -1430,7 +1430,12 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
         StackValue answer = StackValue.none();
 
         for (Iterator<JetElement> iterator = statements.iterator(); iterator.hasNext(); ) {
-            JetElement statement = iterator.next();
+            JetElement possiblyLabeledStatement = iterator.next();
+
+            JetElement statement = possiblyLabeledStatement instanceof JetExpression
+                                   ? JetPsiUtil.safeDeparenthesize((JetExpression) possiblyLabeledStatement, true)
+                                   : possiblyLabeledStatement;
+
 
             if (statement instanceof JetNamedDeclaration) {
                 JetNamedDeclaration declaration = (JetNamedDeclaration) statement;
@@ -1459,7 +1464,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
                 v.mark(labelBeforeLastExpression);
             }
 
-            StackValue result = isExpression ? gen(statement) : genStatement(statement);
+            StackValue result = isExpression ? gen(possiblyLabeledStatement) : genStatement(possiblyLabeledStatement);
 
             if (!iterator.hasNext()) {
                 answer = result;

compiler/testData/codegen/box/labels/labeledDeclarations.kt

@@ -0,0 +1,16 @@
+data class A(val a: Int, val b: Int)
+
+fun box() : String
+{
+    @a val x = 1
+    @b fun a() = 2
+    @c val (z, z2) = A(1, 2)
+
+    if (x != 1) return "fail 1"
+
+    if (a() != 2) return "fail 2"
+
+    if (z != 1 || z2 != 2) return "fail 3"
+
+    return "OK"
+}

compiler/testData/codegen/box/labels/labeledDeclarations2.kt

@@ -0,0 +1,16 @@
+data class A(val a: Int, val b: Int)
+
+fun box() : String
+{
+    (@a val x = 1)
+    (@b fun a() = 2)
+    (@c val (z, z2) = A(1, 2))
+
+    if (x != 1) return "fail 1"
+
+    if (a() != 2) return "fail 2"
+
+    if (z != 1 || z2 != 2) return "fail 3"
+
+    return "OK"
+}

compiler/tests/org/jetbrains/jet/codegen/generated/BlackBoxCodegenTestGenerated.java

@@ -4075,6 +4075,18 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/box/labels"), Pattern.compile("^(.+)\\.kt$"), true);
         }
         
+        @TestMetadata("labeledDeclarations.kt")
+        public void testLabeledDeclarations() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/labels/labeledDeclarations.kt");
+            doTest(fileName);
+        }
+        
+        @TestMetadata("labeledDeclarations2.kt")
+        public void testLabeledDeclarations2() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/labels/labeledDeclarations2.kt");
+            doTest(fileName);
+        }
+        
         @TestMetadata("propertyAccessor.kt")
         public void testPropertyAccessor() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/labels/propertyAccessor.kt");