diff --git a/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/checkers/JavaNullabilityChecker.kt b/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/checkers/JavaNullabilityChecker.kt
index 729e5a45313..fda7841ad04 100644
--- a/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/checkers/JavaNullabilityChecker.kt
+++ b/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/checkers/JavaNullabilityChecker.kt
@@ -167,20 +167,6 @@ class JavaNullabilityChecker : AdditionalTypeChecker {
         else
             null
 
-    private class EnhancedNullabilityInfo(val enhancedType: KotlinType, val isFromJava: Boolean) {
-        val isFromKotlin get() = !isFromJava
-    }
-
-    private fun KotlinType.enhancementFromKotlin() = EnhancedNullabilityInfo(this, isFromJava = false)
-    private fun TypeWithEnhancement.enhancementFromJava() = EnhancedNullabilityInfo(enhancement, isFromJava = true)
-
-    private fun KotlinType.mustNotBeNull(): EnhancedNullabilityInfo? = when {
-        !isError && !isFlexible() && !TypeUtils.acceptsNullable(this) -> enhancementFromKotlin()
-        isFlexible() && !TypeUtils.acceptsNullable(asFlexibleType().upperBound) -> enhancementFromKotlin()
-        this is TypeWithEnhancement && enhancement.mustNotBeNull() != null -> enhancementFromJava()
-        else -> null
-    }
-
     private fun KotlinType.mayBeNull(): EnhancedNullabilityInfo? = when {
         !isError && !isFlexible() && TypeUtils.acceptsNullable(this) -> enhancementFromKotlin()
         isFlexible() && TypeUtils.acceptsNullable(asFlexibleType().lowerBound) -> enhancementFromKotlin()
@@ -188,3 +174,17 @@ class JavaNullabilityChecker : AdditionalTypeChecker {
         else -> null
     }
 }
+
+class EnhancedNullabilityInfo(val enhancedType: KotlinType, val isFromJava: Boolean) {
+    val isFromKotlin get() = !isFromJava
+}
+
+private fun KotlinType.enhancementFromKotlin() = EnhancedNullabilityInfo(this, isFromJava = false)
+private fun TypeWithEnhancement.enhancementFromJava() = EnhancedNullabilityInfo(enhancement, isFromJava = true)
+
+fun KotlinType.mustNotBeNull(): EnhancedNullabilityInfo? = when {
+    !isError && !isFlexible() && !TypeUtils.acceptsNullable(this) -> enhancementFromKotlin()
+    isFlexible() && !TypeUtils.acceptsNullable(asFlexibleType().upperBound) -> enhancementFromKotlin()
+    this is TypeWithEnhancement && enhancement.mustNotBeNull() != null -> enhancementFromJava()
+    else -> null
+}