[FIR] Add ability to generate members and nested classifiers for generated classes

compiler/fir/tree/src/org/jetbrains/kotlin/fir/caches/FirCacheWithPostCompute.kt

@@ -17,3 +17,14 @@ inline fun <K : Any, V> FirCache<K, V, Nothing?>.getValue(key: K): V =
 operator fun <K : Any, V> FirCache<K, V, Nothing>.contains(key: K): Boolean {
     return getValueIfComputed(key) != null
 }
+
+class FirLazyValue<out V, in CONTEXT>(private val cache: FirCache<Unit, V, CONTEXT>) {
+    fun getValue(context: CONTEXT): V {
+        return cache.getValue(Unit, context)
+    }
+}
+
+@Suppress("NOTHING_TO_INLINE")
+inline fun <V> FirLazyValue<V, Nothing?>.getValue(): V {
+    return getValue(null)
+}

compiler/fir/tree/src/org/jetbrains/kotlin/fir/caches/FirCachesFactory.kt

@@ -37,6 +37,10 @@ abstract class FirCachesFactory : FirSessionComponent {
         createValue: (K, CONTEXT) -> Pair<V, DATA>,
         postCompute: (K, V, DATA) -> Unit
     ): FirCache<K, V, CONTEXT>
+
+    fun <V, CONTEXT> createLazyValue(createValue: (CONTEXT) -> V): FirLazyValue<V, CONTEXT> {
+        return FirLazyValue(createCache { _, context -> createValue(context) })
+    }
 }
 
 val FirSession.firCachesFactory: FirCachesFactory by FirSession.sessionComponentAccessor()

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/FirDeclarationOrigin.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.fir.declarations
 
-sealed class FirDeclarationOrigin(private val displayName: String? = null, val fromSupertypes: Boolean = false) {
+sealed class FirDeclarationOrigin(private val displayName: String? = null, val fromSupertypes: Boolean = false, val generated: Boolean = false) {
     object Source : FirDeclarationOrigin()
     object Library : FirDeclarationOrigin()
     object BuiltIns : FirDeclarationOrigin()
@@ -18,7 +18,7 @@ sealed class FirDeclarationOrigin(private val displayName: String? = null, val f
     object IntersectionOverride : FirDeclarationOrigin(fromSupertypes = true)
     object Delegated : FirDeclarationOrigin()
 
-    class Plugin(val key: FirPluginKey) : FirDeclarationOrigin(displayName = "Plugin[$key]")
+    class Plugin(val key: FirPluginKey) : FirDeclarationOrigin(displayName = "Plugin[$key]", generated = true)
 
     override fun toString(): String {
         return displayName ?: this::class.simpleName!!