FIR IDE: add type completion with dot

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 class AAA {
     class Nested
     inner class Inner

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 class A {
     class Nested
     inner class Inner

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 class A {
     class Nested
     inner class Inner

idea/idea-completion/testData/basic/multifile/JavaInnerClasses/JavaInnerClasses.kt

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun main(args: Array<String>) {
     println(R.<caret>)
 }

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirLookupElementFactory.kt

@@ -13,15 +13,12 @@ import com.intellij.codeInsight.lookup.LookupElement
 import com.intellij.codeInsight.lookup.LookupElementBuilder
 import com.intellij.openapi.diagnostic.ControlFlowException
 import com.intellij.openapi.diagnostic.logger
-import com.intellij.openapi.editor.Document
 import com.intellij.openapi.util.TextRange
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.idea.completion.handlers.isTextAt
-import com.intellij.psi.util.PsiUtil
 import org.jetbrains.kotlin.idea.core.asFqNameWithRootPrefixIfNeeded
 import org.jetbrains.kotlin.idea.frontend.api.KtAnalysisSession
 import org.jetbrains.kotlin.idea.frontend.api.analyse
-import org.jetbrains.kotlin.idea.frontend.api.analyseInDependedAnalysisSession
 import org.jetbrains.kotlin.idea.frontend.api.fir.utils.addImportToFile
 import org.jetbrains.kotlin.idea.frontend.api.symbols.*
 import org.jetbrains.kotlin.idea.frontend.api.symbols.markers.KtNamedSymbol
@@ -54,6 +51,13 @@ internal class KotlinFirLookupElementFactory {
             .withPsiElement(symbol.psi) // TODO check if it is a heavy operation and should be postponed
             .withIcon(KotlinFirIconProvider.getIconFor(symbol))
     }
+
+    fun KtAnalysisSession.createLookupElementForClassLikeSymbol(symbol: KtClassLikeSymbol, insertFqName: Boolean = true): LookupElement? {
+        if (symbol !is KtNamedSymbol) return null
+        return classLookupElementFactory.createLookup(symbol, insertFqName)
+            .withPsiElement(symbol.psi) // TODO check if it is a heavy operation and should be postponed
+            .withIcon(KotlinFirIconProvider.getIconFor(symbol))
+    }
 }
 
 private sealed class CallableImportStrategy {
@@ -71,7 +75,7 @@ private interface KotlinLookupObject {
     val shortName: Name
 }
 
-private data class ClassifierLookupObject(override val shortName: Name, val classId: ClassId?) : KotlinLookupObject
+private data class ClassifierLookupObject(override val shortName: Name, val classId: ClassId?, val insertFqName: Boolean) : KotlinLookupObject
 
 /**
  * Simplest lookup object so two lookup elements for the same function will clash.
@@ -93,10 +97,10 @@ private data class VariableLookupObject(
     val importStrategy: CallableImportStrategy
 ) : KotlinLookupObject
 
-private class ClassLookupElementFactory {
+class ClassLookupElementFactory {
-    fun createLookup(symbol: KtClassLikeSymbol): LookupElementBuilder {
+    fun createLookup(symbol: KtClassLikeSymbol, insertFqName: Boolean = true): LookupElementBuilder {
         val name = symbol.nameOrAnonymous
-        return LookupElementBuilder.create(ClassifierLookupObject(name, symbol.classIdIfNonLocal), name.asString())
+        return LookupElementBuilder.create(ClassifierLookupObject(name, symbol.classIdIfNonLocal, insertFqName), name.asString())
             .withInsertHandler(ClassifierInsertionHandler)
     }
 }
@@ -202,7 +206,7 @@ private object ClassifierInsertionHandler : InsertHandler<LookupElement> {
         val targetFile = context.file as? KtFile ?: return
         val lookupObject = item.`object` as ClassifierLookupObject
 
-        if (lookupObject.classId != null) {
+        if (lookupObject.classId != null && lookupObject.insertFqName) {
             val fqName = lookupObject.classId.asSingleFqName()
 
             context.document.replaceString(context.startOffset, context.tailOffset, fqName.render())

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/contributors/FirClassifierCompletionContributor.kt

@@ -8,30 +8,61 @@ package org.jetbrains.kotlin.idea.completion.contributors
 import org.jetbrains.kotlin.idea.completion.checkers.CompletionVisibilityChecker
 import org.jetbrains.kotlin.idea.completion.context.FirBasicCompletionContext
 import org.jetbrains.kotlin.idea.completion.context.FirNameReferenceRawPositionContext
-import org.jetbrains.kotlin.idea.fir.low.level.api.IndexHelper
 import org.jetbrains.kotlin.idea.frontend.api.KtAnalysisSession
-import org.jetbrains.kotlin.idea.frontend.api.scopes.KtScope
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassLikeSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassifierSymbol
-import org.jetbrains.kotlin.idea.frontend.api.types.KtType
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtTypeParameterSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.markers.KtNamedSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.markers.KtSymbolWithMembers
+import org.jetbrains.kotlin.idea.references.mainReference
+import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.KtEnumEntry
+import org.jetbrains.kotlin.psi.KtExpression
 
 internal class FirClassifierCompletionContributor(
     basicContext: FirBasicCompletionContext,
 ) : FirContextCompletionContributorBase<FirNameReferenceRawPositionContext>(basicContext) {
 
     override fun KtAnalysisSession.complete(positionContext: FirNameReferenceRawPositionContext) {
-        val implicitScopes = originalKtFile.getScopeContextForPosition(positionContext.nameExpression).scopes
         val visibilityChecker = CompletionVisibilityChecker.create(basicContext, positionContext)
+
+        when (val receiver = positionContext.explicitReceiver) {
+            null -> {
+                completeWithoutReceiver(positionContext, visibilityChecker)
+            }
+            else -> {
+                completeWithReceiver(receiver, visibilityChecker)
+            }
+        }
+    }
+
+    private fun KtAnalysisSession.completeWithReceiver(
+        receiver: KtExpression,
+        visibilityChecker: CompletionVisibilityChecker
+    ) {
+        val reference = receiver.mainReference ?: return
+        val symbol = reference.resolveToSymbol() as? KtSymbolWithMembers ?: return
+        symbol.getMemberScope()
+            .getClassifierSymbols(scopeNameFilter)
+            .filter { with(visibilityChecker) { isVisible(it) } }
+            .forEach { addClassifierSymbolToCompletion(it, insertFqName = false) }
+    }
+
+    private fun KtAnalysisSession.completeWithoutReceiver(
+        positionContext: FirNameReferenceRawPositionContext,
+        visibilityChecker: CompletionVisibilityChecker
+    ) {
+        val implicitScopes = originalKtFile.getScopeContextForPosition(positionContext.nameExpression).scopes
         val classesFromScopes = implicitScopes
             .getClassifierSymbols(scopeNameFilter)
             .filter { with(visibilityChecker) { isVisible(it) } }
 
-        classesFromScopes.forEach { addSymbolToCompletion(expectedType = null, it) }
+        classesFromScopes.forEach { addClassifierSymbolToCompletion(it, insertFqName = true) }
 
         val kotlinClassesFromIndices = indexHelper.getKotlinClasses(scopeNameFilter, psiFilter = { it !is KtEnumEntry })
         kotlinClassesFromIndices.asSequence()
             .map { it.getSymbol() as KtClassifierSymbol }
             .filter { with(visibilityChecker) { isVisible(it) } }
-            .forEach { addSymbolToCompletion(expectedType = null, it) }
+            .forEach { addClassifierSymbolToCompletion(it, insertFqName = true) }
     }
 }

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/contributors/FirCompletionContributorBase.kt

@@ -16,7 +16,7 @@ import org.jetbrains.kotlin.idea.completion.context.FirRawPositionCompletionCont
 import org.jetbrains.kotlin.idea.completion.weighers.Weighers
 import org.jetbrains.kotlin.idea.fir.low.level.api.IndexHelper
 import org.jetbrains.kotlin.idea.frontend.api.KtAnalysisSession
-import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.*
 import org.jetbrains.kotlin.idea.frontend.api.symbols.markers.KtNamedSymbol
 import org.jetbrains.kotlin.idea.frontend.api.types.KtType
 import org.jetbrains.kotlin.platform.TargetPlatform
@@ -44,6 +44,17 @@ internal abstract class FirCompletionContributorBase<C : FirRawPositionCompletio
         }
     }
 
+    protected fun KtAnalysisSession.addClassifierSymbolToCompletion(symbol: KtClassifierSymbol, insertFqName: Boolean) {
+        if (symbol !is KtNamedSymbol) return
+        val lookup = with(lookupElementFactory) {
+            when (symbol) {
+                is KtClassLikeSymbol -> createLookupElementForClassLikeSymbol(symbol, insertFqName)
+                is KtTypeParameterSymbol -> createLookupElement(symbol)
+            }
+        } ?: return
+        result.addElement(lookup)
+    }
+
     private fun KtAnalysisSession.applyWeighers(
         lookupElement: LookupElement,
         symbol: KtSymbol,