FIR IDE: add ::class/::class.java to callable references completion

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

@@ -20,7 +20,6 @@ import org.jetbrains.kotlin.idea.completion.contributors.*
 import org.jetbrains.kotlin.idea.completion.contributors.FirAnnotationCompletionContributor
 import org.jetbrains.kotlin.idea.completion.contributors.FirCallableCompletionContributor
 import org.jetbrains.kotlin.idea.completion.contributors.FirClassifierCompletionContributor
-import org.jetbrains.kotlin.idea.completion.contributors.FirKeywordCompletionContributor
 import org.jetbrains.kotlin.idea.completion.contributors.complete
 import org.jetbrains.kotlin.idea.completion.weighers.Weighers
 import org.jetbrains.kotlin.idea.fir.low.level.api.util.originalKtFile
@@ -78,6 +77,7 @@ private object KotlinFirCompletionProvider : CompletionProvider<CompletionParame
         positionContext: FirRawPositionCompletionContext,
     ) {
         val keywordContributor = FirKeywordCompletionContributor(basicContext)
+        val classReferenceContributor = FirClassReferenceCompletionContributor(basicContext)
         val callableContributor = FirCallableCompletionContributor(basicContext)
         val infixCallableContributor = FirInfixCallableCompletionContributor(basicContext)
         val callableReferenceContributor = FirCallableReferenceCompletionContributor(basicContext)
@@ -141,6 +141,7 @@ private object KotlinFirCompletionProvider : CompletionProvider<CompletionParame
             }
 
             is FirCallableReferencePositionContext -> {
+                complete(classReferenceContributor, positionContext)
                 complete(callableReferenceContributor, positionContext)
                 complete(classifierReferenceContributor, positionContext)
             }

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

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.completion.contributors
+
+import org.jetbrains.kotlin.idea.completion.context.FirBasicCompletionContext
+import org.jetbrains.kotlin.idea.completion.context.FirCallableReferencePositionContext
+import org.jetbrains.kotlin.idea.completion.createKeywordElement
+import org.jetbrains.kotlin.idea.frontend.api.KtAnalysisSession
+import org.jetbrains.kotlin.platform.jvm.isJvm
+
+internal class FirClassReferenceCompletionContributor(
+    basicContext: FirBasicCompletionContext
+) : FirCompletionContributorBase<FirCallableReferencePositionContext>(basicContext) {
+    override fun KtAnalysisSession.complete(positionContext: FirCallableReferencePositionContext) {
+        if (positionContext.explicitReceiver == null) return
+        sink.addElement(createKeywordElement("class"))
+        if (targetPlatform.isJvm()) {
+            sink.addElement(createKeywordElement("class", tail = ".java"))
+        }
+    }
+}