From e06ae01c0cb1a8de7cda55b615014ba28a46b3d4 Mon Sep 17 00:00:00 2001
From: Dmitry Savvinov <dmitry.savvinov@jetbrains.com>
Date: Thu, 8 Oct 2020 16:20:56 +0300
Subject: [PATCH] Restore nullability after type refinement along with
 annotations

See the issue for details

^KT-42546 Fixed
---
 .../org/jetbrains/kotlin/types/KotlinTypeRefinerImpl.kt    | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/compiler/frontend/src/org/jetbrains/kotlin/types/KotlinTypeRefinerImpl.kt b/compiler/frontend/src/org/jetbrains/kotlin/types/KotlinTypeRefinerImpl.kt
index 0b34268da17..fe63784aae2 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/types/KotlinTypeRefinerImpl.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/types/KotlinTypeRefinerImpl.kt
@@ -67,7 +67,8 @@ class KotlinTypeRefinerImpl(
                 val cached = refinedTypeCache.computeIfAbsent(type.constructor) {
                     type.constructor.declarationDescriptor!!.defaultType.refine(this)
                 }
-                cached.replace(type.arguments)
+
+                cached.restoreAdditionalTypeInformation(type)
             }
             else -> type.refine(this)
         }
@@ -146,3 +147,7 @@ private val TypeConstructor.allDependentTypeConstructors: Collection<TypeConstru
 
 private fun TypeConstructor.isExpectClass() =
     declarationDescriptor?.safeAs<ClassDescriptor>()?.isExpect == true
+
+private fun KotlinType.restoreAdditionalTypeInformation(prototype: KotlinType): KotlinType {
+    return TypeUtils.makeNullableAsSpecified(this, prototype.isMarkedNullable).replace(prototype.arguments)
+}