Support flexible types internally in typeOf

#KT-45066 Fixed

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/Reflection.java

@@ -183,4 +183,11 @@ public class Reflection {
     public static void setUpperBounds(KTypeParameter typeParameter, KType... bounds) {
         factory.setUpperBounds(typeParameter, ArraysKt.toList(bounds));
     }
+
+    // Features of stable typeOf
+
+    @SinceKotlin(version = "1.6")
+    public static KType platformType(KType lowerBound, KType upperBound) {
+        return factory.platformType(lowerBound, upperBound);
+    }
 }

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/ReflectionFactory.java

@@ -93,4 +93,9 @@ public class ReflectionFactory {
     public void setUpperBounds(KTypeParameter typeParameter, List<KType> bounds) {
         ((TypeParameterReference) typeParameter).setUpperBounds(bounds);
     }
+
+    @SinceKotlin(version = "1.6")
+    public KType platformType(KType lowerBound, KType upperBound) {
+        return new TypeReference(lowerBound.getClassifier(), lowerBound.getArguments(), lowerBound.isMarkedNullable(), upperBound);
+    }
 }

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/TypeReference.kt

@@ -3,22 +3,32 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
+@file:Suppress("NEWER_VERSION_IN_SINCE_KOTLIN")
+
 package kotlin.jvm.internal
 
 import kotlin.reflect.*
 
 @SinceKotlin("1.4")
-public class TypeReference(
+public class TypeReference /* @SinceKotlin("1.6") constructor */(
     override val classifier: KClassifier,
     override val arguments: List<KTypeProjection>,
-    override val isMarkedNullable: Boolean
+    override val isMarkedNullable: Boolean,
+    private val platformTypeUpperBound: KType?,
 ) : KType {
+    constructor(
+        classifier: KClassifier,
+        arguments: List<KTypeProjection>,
+        isMarkedNullable: Boolean,
+    ) : this(classifier, arguments, isMarkedNullable, null)
+
     override val annotations: List<Annotation>
         get() = emptyList()
 
     override fun equals(other: Any?): Boolean =
         other is TypeReference &&
-                classifier == other.classifier && arguments == other.arguments && isMarkedNullable == other.isMarkedNullable
+                classifier == other.classifier && arguments == other.arguments && isMarkedNullable == other.isMarkedNullable &&
+                platformTypeUpperBound == other.platformTypeUpperBound
 
     override fun hashCode(): Int =
         (classifier.hashCode() * 31 + arguments.hashCode()) * 31 + isMarkedNullable.hashCode()