[FIR] Refactoring: create use-site scopes via scope provider

compiler/fir/cones/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2010-2019 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.fir.resolve.substitution
+
+import org.jetbrains.kotlin.fir.types.ConeKotlinType
+import org.jetbrains.kotlin.types.model.TypeSubstitutorMarker
+
+abstract class ConeSubstitutor : TypeSubstitutorMarker {
+    open fun substituteOrSelf(type: ConeKotlinType): ConeKotlinType = substituteOrNull(type) ?: type
+    abstract fun substituteOrNull(type: ConeKotlinType): ConeKotlinType?
+
+    object Empty : ConeSubstitutor() {
+        override fun substituteOrSelf(type: ConeKotlinType): ConeKotlinType {
+            return type
+        }
+
+        override fun substituteOrNull(type: ConeKotlinType): ConeKotlinType? {
+            return null
+        }
+
+    }
+}
+
+fun ConeSubstitutor.substituteOrNull(type: ConeKotlinType?): ConeKotlinType? {
+    return type?.let { substituteOrNull(it) }
+}