JVM: Generate object and companion object INSTANCE fields as @NotNull

compiler/light-classes/src/org/jetbrains/kotlin/asJava/classes/ultraLightField.kt

@@ -10,18 +10,19 @@ import com.intellij.psi.*
 import com.intellij.psi.impl.light.LightFieldBuilder
 import com.intellij.psi.util.TypeConversionUtil
 import org.jetbrains.annotations.NonNls
+import org.jetbrains.annotations.NotNull
 import org.jetbrains.kotlin.asJava.LightClassGenerationSupport
 import org.jetbrains.kotlin.asJava.builder.LightMemberOriginForDeclaration
-import org.jetbrains.kotlin.asJava.elements.*
+import org.jetbrains.kotlin.asJava.elements.KtLightElement
+import org.jetbrains.kotlin.asJava.elements.KtLightField
+import org.jetbrains.kotlin.asJava.elements.KtLightFieldForSourceDeclarationSupport
+import org.jetbrains.kotlin.asJava.elements.KtUltraLightSimpleModifierList
 import org.jetbrains.kotlin.codegen.PropertyCodegen
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
-import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.descriptors.annotations.AnnotationUseSiteTarget
 import org.jetbrains.kotlin.idea.KotlinLanguage
-import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.lexer.KtTokens
-import org.jetbrains.kotlin.lexer.KtTokens.VAL_KEYWORD
 import org.jetbrains.kotlin.load.kotlin.TypeMappingMode
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.*
@@ -76,7 +77,8 @@ internal open class KtUltraLightFieldImpl protected constructor(
         KtUltraLightSimpleModifierListField(support, declaration, this, modifiers)
     }
 
-    override fun isEquivalentTo(another: PsiElement?): Boolean = kotlinOrigin == another || (another as? KtLightField)?.kotlinOrigin == kotlinOrigin
+    override fun isEquivalentTo(another: PsiElement?): Boolean =
+        kotlinOrigin == another || (another as? KtLightField)?.kotlinOrigin == kotlinOrigin
 
     override fun getModifierList(): PsiModifierList = modifierList
 
@@ -105,11 +107,12 @@ internal open class KtUltraLightFieldImpl protected constructor(
         }
 
     override val qualifiedNameForNullabilityAnnotation: String?
-        get() {
-            // We don't generate nullability annotations for non-backing fields in backend
-            val typeForAnnotation = kotlinType?.takeUnless { declaration is KtEnumEntry || declaration is KtObjectDeclaration }
-            return computeQualifiedNameForNullabilityAnnotation(typeForAnnotation)
-        }
+        get() =
+            when (declaration) {
+                is KtObjectDeclaration -> NotNull::class.java.name
+                is KtEnumEntry -> null
+                else -> computeQualifiedNameForNullabilityAnnotation(kotlinType)
+            }
 
     override val psiTypeForNullabilityAnnotation: PsiType?
         get() = type

compiler/light-classes/src/org/jetbrains/kotlin/asJava/elements/lightAnnotations.kt

@@ -309,6 +309,9 @@ open class KtLightNullabilityAnnotation<D : KtLightElement<*, PsiModifierListOwn
         // all data-class generated members are not-null
         if (annotatedElement is KtClass && annotatedElement.isData()) return NotNull::class.java.name
 
+        // objects and companion objects are not null
+        if (annotatedElement is KtObjectDeclaration) return NotNull::class.java.name
+
         if (annotatedElement is KtParameter) {
             if (annotatedElement.containingClassOrObject?.isAnnotation() == true) return null
         }