Support mutable collection types in typeOf

flexibleTypes_1_6.kt is fixed for JVM IR in a subsequent commit.

 #KT-35877 Fixed

core/reflection.jvm/src/kotlin/reflect/jvm/internal/ReflectionFactoryImpl.java

@@ -16,6 +16,7 @@
 
 package kotlin.reflect.jvm.internal;
 
+import kotlin.SinceKotlin;
 import kotlin.jvm.internal.*;
 import kotlin.reflect.*;
 import kotlin.reflect.full.KClassifiers;
@@ -151,6 +152,11 @@ public class ReflectionFactoryImpl extends ReflectionFactory {
         return TypeOfImplKt.createPlatformKType(lowerBound, upperBound);
     }
 
+    // @Override // JPS
+    public KType mutableCollectionType(KType type) {
+        return TypeOfImplKt.createMutableCollectionKType(type);
+    }
+
     // Misc
 
     public static void clearCaches() {

core/reflection.jvm/src/kotlin/reflect/jvm/internal/typeOfImpl.kt

@@ -5,6 +5,10 @@
 
 package kotlin.reflect.jvm.internal
 
+import org.jetbrains.kotlin.builtins.jvm.JavaToKotlinClassMap
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.resolve.descriptorUtil.builtIns
+import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameUnsafe
 import org.jetbrains.kotlin.types.KotlinTypeFactory
 import org.jetbrains.kotlin.types.SimpleType
 import kotlin.reflect.KType
@@ -19,3 +23,19 @@ internal fun createPlatformKType(lowerBound: KType, upperBound: KType): KType {
         )
     )
 }
+
+internal fun createMutableCollectionKType(type: KType): KType {
+    val kotlinType = (type as KTypeImpl).type
+    require(kotlinType is SimpleType) { "Non-simple type cannot be a mutable collection type: $type" }
+    val classifier = kotlinType.constructor.declarationDescriptor as? ClassDescriptor
+        ?: throw IllegalArgumentException("Non-class type cannot be a mutable collection type: $type")
+    return KTypeImpl(
+        KotlinTypeFactory.simpleType(kotlinType, constructor = classifier.readOnlyToMutable().typeConstructor)
+    )
+}
+
+private fun ClassDescriptor.readOnlyToMutable(): ClassDescriptor {
+    val fqName = JavaToKotlinClassMap.readOnlyToMutable(fqNameUnsafe)
+        ?: throw IllegalArgumentException("Not a readonly collection: $this")
+    return builtIns.getBuiltInClassByFqName(fqName)
+}