Fix some compiler warnings in FIR modules

compiler/fir/tree/src/org/jetbrains/kotlin/fir/scopes/FirScope.kt

@@ -66,7 +66,7 @@ enum class ProcessorAction {
     }
 }
 
-
+@Suppress("NOTHING_TO_INLINE")
 inline fun FirScope.processClassifiersByName(
     name: Name,
     noinline processor: (FirClassifierSymbol<*>) -> Unit

compiler/fir/tree/src/org/jetbrains/kotlin/fir/visitors/CompositeTransformResult.kt

@@ -7,36 +7,38 @@ package org.jetbrains.kotlin.fir.visitors
 
 import org.jetbrains.kotlin.fir.FirElement
 
-sealed class CompositeTransformResult<out T : Any>() {
+sealed class CompositeTransformResult<out T : Any> {
 
     class Single<out T : Any>(val _single: T) : CompositeTransformResult<T>()
 
     class Multiple<out T : Any>(val _list: List<T>) : CompositeTransformResult<T>()
 
     companion object {
-        fun <T : Any> empty() = CompositeTransformResult.Multiple<T>(emptyList<T>())
-        fun <T : Any> single(t: T) = CompositeTransformResult.Single(t)
-        fun <T : Any> many(l: List<T>) = CompositeTransformResult.Multiple(l)
+        fun <T : Any> empty() = Multiple(emptyList<T>())
+        fun <T : Any> single(t: T) = Single(t)
+        fun <T : Any> many(l: List<T>) = Multiple(l)
     }
 
+    @Suppress("UNCHECKED_CAST")
     val list: List<T>
         get() = when (this) {
-            is CompositeTransformResult.Multiple<*> -> _list as List<T>
+            is Multiple<*> -> _list as List<T>
             else -> error("!")
         }
 
 
+    @Suppress("UNCHECKED_CAST")
     val single: T
         get() = when (this) {
-            is CompositeTransformResult.Single<*> -> _single as T
+            is Single<*> -> _single as T
             else -> error("!")
         }
 
     val isSingle
-        get() = this is CompositeTransformResult.Single<*>
+        get() = this is Single<*>
 
     val isEmpty
-        get() = this is CompositeTransformResult.Multiple<*> && this.list.isEmpty()
+        get() = this is Multiple<*> && this.list.isEmpty()
 }
 
 @Suppress("NOTHING_TO_INLINE")

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/implementation.kt

@@ -69,7 +69,7 @@ fun SmartPrinter.printImplementation(implementation: Implementation) {
             }
             println("(")
             withIndent {
-                fieldsWithoutDefault.forEachIndexed { i, field ->
+                fieldsWithoutDefault.forEachIndexed { _, field ->
                     printField(field, isImplementation = true, override = true, end = ",")
                 }
             }

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/util/InterfaceAbstractClassSolver.kt

@@ -52,9 +52,11 @@ private fun updateKinds(solution: List<Boolean>, elementMapping: ElementMapping)
         val element = elementMapping[index * 2].origin
         val existingKind = element.kind
         if (isClass) {
-            when (existingKind) {
-                Implementation.Kind.Interface -> throw IllegalStateException(element.toString())
-                null -> element.kind = when (element) {
+            if (existingKind == Implementation.Kind.Interface)
+                throw IllegalStateException(element.toString())
+
+            if (existingKind == null) {
+                element.kind = when (element) {
                     is Implementation -> {
                         if (elementMapping.hasInheritors(element))
                             Implementation.Kind.AbstractClass