Fix primitive types mapping

Use boxed version if type was enhaced to not-nullable

compiler/backend/src/org/jetbrains/kotlin/codegen/state/JetTypeMapper.java

@@ -44,6 +44,7 @@ import org.jetbrains.kotlin.load.java.descriptors.JavaCallableMemberDescriptor;
 import org.jetbrains.kotlin.load.java.descriptors.JavaClassDescriptor;
 import org.jetbrains.kotlin.load.java.lazy.descriptors.LazyJavaPackageFragment;
 import org.jetbrains.kotlin.load.java.lazy.descriptors.LazyJavaPackageScope;
+import org.jetbrains.kotlin.load.java.typeEnhancement.TypeEnhancementKt;
 import org.jetbrains.kotlin.load.kotlin.KotlinJvmBinaryClass;
 import org.jetbrains.kotlin.load.kotlin.KotlinJvmBinaryPackageSourceElement;
 import org.jetbrains.kotlin.load.kotlin.KotlinJvmBinarySourceElement;
@@ -510,7 +511,8 @@ public class JetTypeMapper {
         PrimitiveType primitiveType = KotlinBuiltIns.getPrimitiveTypeByFqName(fqName);
         if (primitiveType != null) {
             Type asmType = Type.getType(JvmPrimitiveType.get(primitiveType).getDesc());
-            return TypeUtils.isNullableType(type) ? boxType(asmType) : asmType;
+            boolean isNullableInJava = TypeUtils.isNullableType(type) || TypeEnhancementKt.hasEnhancedNullability(type);
+            return isNullableInJava ? boxType(asmType) : asmType;
         }
 
         PrimitiveType arrayElementType = KotlinBuiltIns.getPrimitiveTypeByArrayClassFqName(fqName);

compiler/frontend.java/src/org/jetbrains/kotlin/jvm/RuntimeAssertions.kt

@@ -20,6 +20,7 @@ import com.intellij.openapi.util.text.StringUtil
 import org.jetbrains.kotlin.descriptors.ReceiverParameterDescriptor
 import org.jetbrains.kotlin.load.java.JvmAnnotationNames
 import org.jetbrains.kotlin.jvm.bindingContextSlices.RUNTIME_ASSERTION_INFO
+import org.jetbrains.kotlin.load.java.typeEnhancement.hasEnhancedNullability
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.calls.checkers.AdditionalTypeChecker
@@ -74,9 +75,6 @@ class RuntimeAssertionInfo(val needNotNullAssertion: Boolean, val message: Strin
             else
                 null
         }
-
-        private fun KotlinType.hasEnhancedNullability()
-                = annotations.findAnnotation(JvmAnnotationNames.ENHANCED_NULLABILITY_ANNOTATION) != null
     }
 }
 

compiler/testData/codegen/box/platformTypes/primitives/identityEquals.kt

@@ -3,7 +3,7 @@ fun box(): String {
     l.add(1000)
 
     val x = l[0] === 1000
-    if (!x) return "Fail: $x"
+    if (x) return "Fail: $x"
     val x1 = l[0] === 1
     if (x1) return "Fail 1: $x"
     val x2 = l[0] === l[0]

compiler/testData/codegen/boxWithJava/enhancedPrimitives/J.java

@@ -0,0 +1,7 @@
+public class J {
+    // This test checks that although type '@org.jetbrains.annotations.NotNull Integer' is perceived as simple Int,
+    // it's correctly mapped to 'Lj.l.Integer' by JVM backend
+    public static String test(@org.jetbrains.annotations.NotNull Integer x) {
+        return "OK";
+    }
+}

compiler/testData/codegen/boxWithJava/enhancedPrimitives/box.kt

@@ -0,0 +1 @@
+fun box() = J.test(1)

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxWithJavaCodegenTestGenerated.java

@@ -77,6 +77,12 @@ public class BlackBoxWithJavaCodegenTestGenerated extends AbstractBlackBoxCodege
         doTestWithJava(fileName);
     }
 
+    @TestMetadata("enhancedPrimitives")
+    public void testEnhancedPrimitives() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/boxWithJava/enhancedPrimitives/");
+        doTestWithJava(fileName);
+    }
+
     @TestMetadata("inline")
     public void testInline() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/boxWithJava/inline/");

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/typeEnhancement/typeEnhancement.kt

@@ -42,6 +42,8 @@ import org.jetbrains.kotlin.utils.toReadOnlyList
 // For flexible types, both bounds are indexed in the same way: `(A<B>..C<D>)` gives `0 - (A<B>..C<D>), 1 - B and D`.
 fun KotlinType.enhance(qualifiers: (Int) -> JavaTypeQualifiers) = this.enhancePossiblyFlexible(qualifiers, 0).typeIfChanged
 
+fun KotlinType.hasEnhancedNullability()
+        = annotations.findAnnotation(JvmAnnotationNames.ENHANCED_NULLABILITY_ANNOTATION) != null
 
 private enum class TypeComponentPosition {
     FLEXIBLE_LOWER,