Don't generate unnecessary checkcast to java.lang.Number

compiler/backend/src/org/jetbrains/kotlin/codegen/StackValue.java

@@ -396,9 +396,10 @@ public abstract class StackValue {
             }
         }
         else if (fromType.getSort() == Type.OBJECT) {
-            if (fromType.equals(getType(Boolean.class)) || fromType.equals(getType(Character.class))) {
-                unbox(unboxType(fromType), v);
-                coerce(unboxType(fromType), toType, v);
+            Type unboxedType = unboxPrimitiveTypeOrNull(fromType);
+            if (unboxedType != null) {
+                unbox(unboxedType, v);
+                coerce(unboxedType, toType, v);
             }
             else {
                 if (toType.getSort() == Type.BOOLEAN || toType.getSort() == Type.CHAR) {

compiler/testData/codegen/bytecodeText/noNumberCheckCast.kt

@@ -0,0 +1,11 @@
+fun test() {
+    val z : Int? = 1
+    val r = z!! + 1
+    stubPreventBoxingOptimization(z)
+}
+
+fun stubPreventBoxingOptimization(s: Int?) {
+    s
+}
+
+//0 CHECKCAST java/lang/Number

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -263,6 +263,12 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
         doTest(fileName);
     }
 
+    @TestMetadata("noNumberCheckCast.kt")
+    public void testNoNumberCheckCast() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/noNumberCheckCast.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("noSuperCheckInDefaultConstuctor.kt")
     public void testNoSuperCheckInDefaultConstuctor() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/noSuperCheckInDefaultConstuctor.kt");