FIR IDE: add validation contract to analysis session

This contract ensures that analysis session is used:
  * in read action
  * in non-EDT
  * Project has not changed since the session was created

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

@@ -10,8 +10,7 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.types.model.KotlinTypeMarker
 
-abstract class FrontendAnalysisSession {
-    abstract fun getSmartCastedToTypes(expression: KtExpression): Collection<KotlinTypeMarker>?
+abstract class FrontendAnalysisSession : Invalidatable {
 
     abstract fun getImplicitReceiverSmartCasts(expression: KtExpression): Collection<ImplicitReceiverSmartCast>
 

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

@@ -0,0 +1,46 @@
+/*
+ * 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
+
+import com.intellij.openapi.application.ApplicationManager
+import com.intellij.openapi.project.Project
+import org.jetbrains.kotlin.analyzer.KotlinModificationTrackerService
+
+interface Invalidatable {
+    fun isValid(): Boolean
+
+    fun invalidationReason(): String
+
+    fun assertIsValid() {
+        assert(isValid()) { "Access to invalid $this, invalidation reason is ${invalidationReason()}" }
+    }
+}
+
+class ReadActionConfinementValidityToken(project: Project) : Invalidatable {
+    private val modificationTracker = KotlinModificationTrackerService.getInstance(project).modificationTracker
+    private val ownerThread = Thread.currentThread()
+    private val onCreatedTimeStamp = modificationTracker.modificationCount
+
+
+    override fun isValid(): Boolean {
+        val application = ApplicationManager.getApplication()
+        if (application.isDispatchThread) return false
+        if (!application.isReadAccessAllowed) return false
+        if (ownerThread != Thread.currentThread()) return false
+        return onCreatedTimeStamp == modificationTracker.modificationCount
+    }
+
+    override fun invalidationReason(): String {
+        val application = ApplicationManager.getApplication()
+        if (application.isDispatchThread) return "Called in EDT thread"
+        if (!application.isReadAccessAllowed) return "Called outside read action"
+        if (ownerThread != Thread.currentThread()) {
+            return "Called outside the thread was created in (was created in $ownerThread, but accessed in ${Thread.currentThread()}"
+        }
+        if (onCreatedTimeStamp != modificationTracker.modificationCount) return "PSI has changed since creation"
+        error("Getting invalidation reason for valid invalidatable")
+    }
+}