FIR IDE: Add reference shortening service which works over FIR

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/KtAnalysisSession.kt

@@ -45,6 +45,7 @@ abstract class KtAnalysisSession(final override val token: ValidityToken) : Vali
     protected abstract val callResolver: KtCallResolver
     protected abstract val completionCandidateChecker: KtCompletionCandidateChecker
     protected abstract val symbolDeclarationOverridesProvider: KtSymbolDeclarationOverridesProvider
+    protected abstract val referenceShortener: KtReferenceShortener
 
     @Suppress("LeakingThis")
 
@@ -177,4 +178,6 @@ abstract class KtAnalysisSession(final override val token: ValidityToken) : Vali
 
     fun KtReturnExpression.getReturnTargetSymbol(): KtCallableSymbol? =
         expressionHandlingComponent.getReturnExpressionTargetSymbol(this)
+
+    fun collectPossibleReferenceShortenings(file: KtFile, from: Int, to: Int) = referenceShortener.collectShortenings(file, from, to)
 }

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/components/KtReferenceShortener.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2010-2020 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.frontend.api.components
+
+import com.intellij.openapi.application.ApplicationManager
+import com.intellij.psi.SmartPsiElementPointer
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.psi.KtUserType
+
+abstract class KtReferenceShortener : KtAnalysisSessionComponent() {
+    abstract fun collectShortenings(file: KtFile, from: Int, to: Int): ShortenCommand
+}
+
+class ShortenCommand(
+    val targetFile: KtFile,
+    val importsToAdd: List<FqName>,
+    val typesToShorten: List<SmartPsiElementPointer<KtUserType>>
+) {
+    fun invokeShortening() {
+        ApplicationManager.getApplication().assertWriteAccessAllowed()
+
+        for (typePointer in typesToShorten) {
+            val type = typePointer.element ?: continue
+            type.deleteQualifier()
+        }
+    }
+}