FIR: Add components storage to FirSession

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirSession.kt

@@ -5,4 +5,16 @@
 
 package org.jetbrains.kotlin.fir
 
-interface FirSession
+import kotlin.reflect.KClass
+
+interface FirSession {
+
+
+    val components: Map<KClass<*>, Any>
+
+    fun <T : Any> getService(kclass: KClass<T>): T =
+        components[kclass] as T
+}
+
+inline fun <reified T : Any> FirSession.service(): T =
+    getService(T::class)

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirSessionBase.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. 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.fir
+
+import kotlin.reflect.KClass
+
+abstract class FirSessionBase : FirSession {
+
+    protected fun <T : Any> registerComponent(tClass: KClass<T>, t: T) {
+        assert(tClass !in components) { "Already registered component" }
+        components[tClass] = t
+    }
+
+    override val components: MutableMap<KClass<*>, Any> = mutableMapOf()
+
+}