More elegant way to achieve the same + fixed KT-7746 Top level package name completion does not work inside class body

#KT-7746 Fixed

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

@@ -35,4 +35,6 @@ public class SamConstructorDescriptor(
 
 public object SamConstructorDescriptorKindExclude : DescriptorKindExclude {
     override fun matches(descriptor: DeclarationDescriptor) = descriptor is SamConstructorDescriptor
+
+    override val fullyExcludedDescriptorKinds: Int get() = 0
 }

core/descriptors/src/org/jetbrains/kotlin/resolve/scopes/JetScope.kt

@@ -110,7 +110,7 @@ public class DescriptorKindFilter(
             = kindMask and kinds != 0
 
     public fun exclude(exclude: DescriptorKindExclude): DescriptorKindFilter
-            = DescriptorKindFilter(kindMask, excludes + listOf(exclude))
+            = DescriptorKindFilter(kindMask and exclude.fullyExcludedDescriptorKinds.inv(), excludes + listOf(exclude))
 
     public fun withoutKinds(kinds: Int): DescriptorKindFilter
             = DescriptorKindFilter(kindMask and kinds.inv(), excludes)
@@ -196,20 +196,29 @@ public class DescriptorKindFilter(
 public trait DescriptorKindExclude {
     public fun matches(descriptor: DeclarationDescriptor): Boolean
 
+    public val fullyExcludedDescriptorKinds: Int
+
     override fun toString() = this.javaClass.getSimpleName()
 
     public object Extensions : DescriptorKindExclude {
         override fun matches(descriptor: DeclarationDescriptor)
                 = descriptor is CallableDescriptor && descriptor.getExtensionReceiverParameter() != null
+
+        override val fullyExcludedDescriptorKinds: Int get() = 0
     }
 
     public object NonExtensions : DescriptorKindExclude {
         override fun matches(descriptor: DeclarationDescriptor)
                 = descriptor !is CallableDescriptor || descriptor.getExtensionReceiverParameter() == null
+
+        override val fullyExcludedDescriptorKinds: Int
+            get() = DescriptorKindFilter.ALL_KINDS_MASK and (DescriptorKindFilter.FUNCTIONS_MASK or DescriptorKindFilter.VARIABLES_MASK).inv()
     }
 
     public object EnumEntry : DescriptorKindExclude {
         override fun matches(descriptor: DeclarationDescriptor)
                 = descriptor is ClassDescriptor && descriptor.getKind() == ClassKind.ENUM_ENTRY
+
+        override val fullyExcludedDescriptorKinds: Int get() = 0
     }
 }

idea/ide-common/src/org/jetbrains/kotlin/idea/codeInsight/ReferenceVariantsHelper.kt

@@ -221,9 +221,7 @@ public class ReferenceVariantsHelper(
             nameFilter: (Name) -> Boolean
     ) {
         if (kindFilter.excludes.contains(DescriptorKindExclude.Extensions)) return
-        val extensionsFilter = kindFilter
-                .restrictedToKinds(DescriptorKindFilter.FUNCTIONS_MASK or DescriptorKindFilter.VARIABLES_MASK)
-                .exclude(DescriptorKindExclude.NonExtensions)
+        val extensionsFilter = kindFilter.exclude(DescriptorKindExclude.NonExtensions)
 
         fun processExtension(descriptor: DeclarationDescriptor) {
             addAll((descriptor as CallableDescriptor).substituteExtensionIfCallable(receiver, callType, context, dataFlowInfo, resolutionScope.getContainingDeclaration()))

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/BasicCompletionSession.kt

@@ -233,11 +233,11 @@ class BasicCompletionSession(configuration: CompletionSessionConfiguration,
     private companion object {
         object NonAnnotationClassifierExclude : DescriptorKindExclude {
             override fun matches(descriptor: DeclarationDescriptor): Boolean {
-                return if (descriptor is ClassDescriptor)
-                    descriptor.getKind() != ClassKind.ANNOTATION_CLASS
-                else
-                    descriptor !is ClassifierDescriptor
+                if (descriptor !is ClassifierDescriptor) return false
+                return descriptor !is ClassDescriptor || descriptor.getKind() != ClassKind.ANNOTATION_CLASS
             }
+
+            override val fullyExcludedDescriptorKinds: Int get() = 0
         }
 
         val ANNOTATION_TYPES_FILTER = DescriptorKindFilter(DescriptorKindFilter.NON_SINGLETON_CLASSIFIERS_MASK or DescriptorKindFilter.PACKAGES_MASK) exclude NonAnnotationClassifierExclude

idea/idea-completion/testData/basic/common/TopLevelPackageInClassBody.kt

@@ -0,0 +1,5 @@
+class A {
+    kot<caret>
+}
+
+// EXIST: "kotlin"

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/JSBasicCompletionTestGenerated.java

@@ -865,6 +865,12 @@ public class JSBasicCompletionTestGenerated extends AbstractJSBasicCompletionTes
             doTest(fileName);
         }
 
+        @TestMetadata("TopLevelPackageInClassBody.kt")
+        public void testTopLevelPackageInClassBody() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/TopLevelPackageInClassBody.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("TypeParameterFromOuterClass.kt")
         public void testTypeParameterFromOuterClass() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/TypeParameterFromOuterClass.kt");

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/JvmBasicCompletionTestGenerated.java

@@ -865,6 +865,12 @@ public class JvmBasicCompletionTestGenerated extends AbstractJvmBasicCompletionT
             doTest(fileName);
         }
 
+        @TestMetadata("TopLevelPackageInClassBody.kt")
+        public void testTopLevelPackageInClassBody() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/TopLevelPackageInClassBody.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("TypeParameterFromOuterClass.kt")
         public void testTypeParameterFromOuterClass() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/common/TypeParameterFromOuterClass.kt");