added test for KT-248

idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -1613,7 +1613,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
             if (!(descriptor instanceof ClassDescriptor)) {
                 throw new UnsupportedOperationException("don't know how to handle non-class types in as/as?");
             }
-            Type type = typeMapper.mapType(jetType, OwnerKind.INTERFACE);
+            Type type = typeMapper.boxType(typeMapper.mapType(jetType, OwnerKind.INTERFACE));
             generateInstanceOf(StackValue.expression(OBJECT_TYPE, expression.getLeft(), this), jetType, true);
             Label isInstance = new Label();
             v.ifne(isInstance);
@@ -1739,7 +1739,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
             if (leaveExpressionOnStack) {
                 v.dup();
             }
-            Type type = typeMapper.mapType(jetType, OwnerKind.INTERFACE);
+            Type type = typeMapper.boxType(typeMapper.mapType(jetType, OwnerKind.INTERFACE));
             v.instanceOf(type);
         }
     }

idea/testData/codegen/regressions/kt248.jet

@@ -0,0 +1,7 @@
+fun box() : String {
+    val b = true as? Boolean //exception
+    val i = 1 as Int         //exception
+    val j = 1 as Int?        //ok
+    val s = "s" as String    //ok
+    return "OK"
+}

idea/tests/org/jetbrains/jet/codegen/PrimitiveTypesTest.java

@@ -270,4 +270,8 @@ public class PrimitiveTypesTest extends CodegenTestCase {
     public void testKt243 () throws Exception {
         blackBoxFile("regressions/kt243.jet");
     }
+
+    public void testKt248 () throws Exception {
+        blackBoxFile("regressions/kt248.jet");
+    }
 }