diff --git a/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaUtils.kt b/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaUtils.kt
index 6bf533bb124..f67b956a700 100644
--- a/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaUtils.kt
+++ b/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaUtils.kt
@@ -24,7 +24,6 @@ import org.jetbrains.kotlin.fir.java.declarations.buildJavaValueParameter
 import org.jetbrains.kotlin.fir.java.enhancement.readOnlyToMutable
 import org.jetbrains.kotlin.fir.references.builder.buildErrorNamedReference
 import org.jetbrains.kotlin.fir.references.builder.buildResolvedNamedReference
-import org.jetbrains.kotlin.fir.resolve.constructClassType
 import org.jetbrains.kotlin.fir.resolve.firSymbolProvider
 import org.jetbrains.kotlin.fir.resolve.getClassDeclaredCallableSymbols
 import org.jetbrains.kotlin.fir.symbols.StandardClassIds
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/AbstractAnnotationDeserializer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/AbstractAnnotationDeserializer.kt
index 2829c8286ab..1cb722cee54 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/AbstractAnnotationDeserializer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/AbstractAnnotationDeserializer.kt
@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
 import org.jetbrains.kotlin.fir.types.FirTypeRef
 import org.jetbrains.kotlin.fir.types.builder.buildErrorTypeRef
 import org.jetbrains.kotlin.fir.types.builder.buildResolvedTypeRef
+import org.jetbrains.kotlin.fir.types.constructType
 import org.jetbrains.kotlin.metadata.ProtoBuf
 import org.jetbrains.kotlin.metadata.ProtoBuf.Annotation.Argument.Value.Type.*
 import org.jetbrains.kotlin.metadata.deserialization.Flags
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt
index 03826800611..638a0d3edaa 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt
@@ -9,7 +9,6 @@ import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.FirTypeParametersOwner
 import org.jetbrains.kotlin.fir.declarations.addDefaultBoundIfNecessary
 import org.jetbrains.kotlin.fir.declarations.builder.FirTypeParameterBuilder
-import org.jetbrains.kotlin.fir.resolve.toTypeProjection
 import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
 import org.jetbrains.kotlin.fir.symbols.ConeClassifierLookupTag
 import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterLookupTag
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ResolveUtils.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ResolveUtils.kt
index 94007b5ed64..877884f10e2 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ResolveUtils.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ResolveUtils.kt
@@ -37,8 +37,6 @@ import org.jetbrains.kotlin.fir.types.builder.buildResolvedTypeRef
 import org.jetbrains.kotlin.fir.types.impl.ConeClassLikeTypeImpl
 import org.jetbrains.kotlin.fir.types.impl.ConeTypeParameterTypeImpl
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.types.AbstractStrictEqualityTypeChecker
-import org.jetbrains.kotlin.types.Variance
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 inline fun <K, V, VA : V> MutableMap<K, V>.getOrPut(key: K, defaultValue: (K) -> VA, postCompute: (VA) -> Unit): V {
@@ -150,21 +148,6 @@ fun ConeClassifierLookupTag.toSymbol(useSiteSession: FirSession): FirClassifierS
 
 fun ConeTypeParameterLookupTag.toSymbol(): FirTypeParameterSymbol = this.symbol as FirTypeParameterSymbol
 
-fun ConeClassLikeLookupTag.constructClassType(
-    typeArguments: Array<out ConeKotlinTypeProjection>,
-    isNullable: Boolean,
-): ConeLookupTagBasedType {
-    return ConeClassLikeTypeImpl(this, typeArguments, isNullable)
-}
-
-fun ConeClassifierLookupTag.constructType(typeArguments: Array<ConeKotlinTypeProjection>, isNullable: Boolean): ConeLookupTagBasedType {
-    return when (this) {
-        is ConeTypeParameterLookupTag -> ConeTypeParameterTypeImpl(this, isNullable)
-        is ConeClassLikeLookupTag -> this.constructClassType(typeArguments, isNullable)
-        else -> error("! ${this::class}")
-    }
-}
-
 fun FirClassifierSymbol<*>.constructType(typeArguments: Array<ConeKotlinTypeProjection>, isNullable: Boolean): ConeLookupTagBasedType {
     return when (this) {
         is FirTypeParameterSymbol -> {
@@ -200,12 +183,6 @@ fun FirClassifierSymbol<*>.constructType(
             }
         }
 
-fun ConeKotlinType.toTypeProjection(variance: Variance): ConeKotlinTypeProjection =
-    when (variance) {
-        Variance.INVARIANT -> this
-        Variance.IN_VARIANCE -> ConeKotlinTypeProjectionIn(this)
-        Variance.OUT_VARIANCE -> ConeKotlinTypeProjectionOut(this)
-    }
 
 private fun List<FirQualifierPart>.toTypeProjections(): Array<ConeKotlinTypeProjection> = flatMap {
     it.typeArguments.map { typeArgument ->
@@ -220,81 +197,6 @@ private fun List<FirQualifierPart>.toTypeProjections(): Array<ConeKotlinTypeProj
     }
 }.toTypedArray()
 
-fun coneFlexibleOrSimpleType(
-    typeContext: ConeInferenceContext?,
-    lowerBound: ConeKotlinType,
-    upperBound: ConeKotlinType,
-): ConeKotlinType {
-    if (lowerBound is ConeFlexibleType) {
-        return coneFlexibleOrSimpleType(typeContext, lowerBound.lowerBound, upperBound)
-    }
-    if (upperBound is ConeFlexibleType) {
-        return coneFlexibleOrSimpleType(typeContext, lowerBound, upperBound.upperBound)
-    }
-    return when {
-        typeContext != null && AbstractStrictEqualityTypeChecker.strictEqualTypes(typeContext, lowerBound, upperBound) -> {
-            lowerBound
-        }
-        typeContext == null && lowerBound == upperBound -> {
-            lowerBound
-        }
-        else -> {
-            ConeFlexibleType(lowerBound, upperBound)
-        }
-    }
-}
-
-fun <T : ConeKotlinType> T.withNullability(nullability: ConeNullability, typeContext: ConeInferenceContext? = null): T {
-    if (this.nullability == nullability) {
-        return this
-    }
-
-    return when (this) {
-        is ConeClassErrorType -> this
-        is ConeClassLikeTypeImpl -> ConeClassLikeTypeImpl(lookupTag, typeArguments, nullability.isNullable) as T
-        is ConeTypeParameterTypeImpl -> ConeTypeParameterTypeImpl(lookupTag, nullability.isNullable) as T
-        is ConeFlexibleType -> {
-            if (nullability == ConeNullability.UNKNOWN) {
-                if (lowerBound.nullability != upperBound.nullability || lowerBound.nullability == ConeNullability.UNKNOWN) {
-                    return this
-                }
-            }
-            coneFlexibleOrSimpleType(typeContext, lowerBound.withNullability(nullability), upperBound.withNullability(nullability)) as T
-        }
-        is ConeTypeVariableType -> ConeTypeVariableType(nullability, lookupTag) as T
-        is ConeCapturedType -> ConeCapturedType(captureStatus, lowerType, nullability, constructor) as T
-        is ConeIntersectionType -> when (nullability) {
-            ConeNullability.NULLABLE -> this.mapTypes {
-                it.withNullability(nullability)
-            }
-            ConeNullability.UNKNOWN -> this // TODO: is that correct?
-            ConeNullability.NOT_NULL -> this
-        } as T
-        is ConeStubType -> ConeStubType(variable, nullability) as T
-        is ConeDefinitelyNotNullType -> when (nullability) {
-            ConeNullability.NOT_NULL -> this
-            ConeNullability.NULLABLE -> original.withNullability(nullability)
-            ConeNullability.UNKNOWN -> original.withNullability(nullability)
-        } as T
-        is ConeIntegerLiteralType -> this
-        else -> error("sealed: ${this::class}")
-    }
-}
-
-
-fun <T : ConeKotlinType> T.withArguments(arguments: Array<out ConeKotlinTypeProjection>): T {
-    if (this.typeArguments === arguments) {
-        return this
-    }
-
-    return when (this) {
-        is ConeClassErrorType -> this
-        is ConeClassLikeTypeImpl -> ConeClassLikeTypeImpl(lookupTag, arguments, nullability.isNullable) as T
-        is ConeDefinitelyNotNullType -> ConeDefinitelyNotNullType.create(original.withArguments(arguments))!! as T
-        else -> error("Not supported: $this: ${this.render()}")
-    }
-}
-
 fun FirFunction<*>.constructFunctionalTypeRef(session: FirSession): FirResolvedTypeRef {
     val receiverTypeRef = when (this) {
         is FirSimpleFunction -> receiverTypeRef
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt
index 68e9c498988..8749b12a24a 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt
@@ -19,7 +19,6 @@ import org.jetbrains.kotlin.fir.resolve.inference.preprocessLambdaArgument
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.firUnsafe
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.resultType
-import org.jetbrains.kotlin.fir.resolve.withNullability
 import org.jetbrains.kotlin.fir.returnExpressions
 import org.jetbrains.kotlin.fir.scopes.impl.FirILTTypeRefPlaceHolder
 import org.jetbrains.kotlin.fir.scopes.impl.FirIntegerOperator
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerLevels.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerLevels.kt
index cccc68cce24..64158e51276 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerLevels.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerLevels.kt
@@ -11,7 +11,6 @@ import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.fir.resolve.BodyResolveComponents
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.resolve.firSymbolProvider
-import org.jetbrains.kotlin.fir.resolve.withNullability
 import org.jetbrains.kotlin.fir.scopes.FirScope
 import org.jetbrains.kotlin.fir.scopes.ProcessorAction
 import org.jetbrains.kotlin.fir.scopes.impl.FirAbstractImportingScope
@@ -20,6 +19,7 @@ import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.ConeNullability
+import org.jetbrains.kotlin.fir.types.withNullability
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlin.utils.addToStdlib.cast
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerResolveManager.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerResolveManager.kt
index 51e68a4bbd0..f64e6d2ec56 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerResolveManager.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/TowerResolveManager.kt
@@ -8,7 +8,6 @@ package org.jetbrains.kotlin.fir.resolve.calls
 import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.fir.expressions.FirResolvedQualifier
 import org.jetbrains.kotlin.fir.expressions.builder.FirQualifiedAccessExpressionBuilder
-import org.jetbrains.kotlin.fir.resolve.constructClassType
 import org.jetbrains.kotlin.fir.resolve.constructType
 import org.jetbrains.kotlin.fir.resolve.transformQualifiedAccessUsingSmartcastInfo
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.firUnsafe
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt
index 663ec350e7b..708d7842ec0 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt
@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.fir.resolve.dfa.contracts.buildContractFir
 import org.jetbrains.kotlin.fir.resolve.dfa.contracts.createArgumentsMapping
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.FirAbstractBodyResolveTransformer
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.resultType
-import org.jetbrains.kotlin.fir.resolve.withNullability
 import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.CallableId
 import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/impl/FirBuiltinSymbolProvider.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/impl/FirBuiltinSymbolProvider.kt
index e2d07e9a6ed..02e6bbd706e 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/impl/FirBuiltinSymbolProvider.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/impl/FirBuiltinSymbolProvider.kt
@@ -7,19 +7,21 @@ package org.jetbrains.kotlin.fir.resolve.impl
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor
-import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.descriptors.ClassKind
+import org.jetbrains.kotlin.descriptors.Modality
+import org.jetbrains.kotlin.descriptors.SourceElement
+import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.builder.buildClassImpl
 import org.jetbrains.kotlin.fir.declarations.builder.buildSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.builder.buildTypeParameter
 import org.jetbrains.kotlin.fir.declarations.builder.buildValueParameter
-import org.jetbrains.kotlin.fir.declarations.impl.*
+import org.jetbrains.kotlin.fir.declarations.impl.FirDeclarationStatusImpl
 import org.jetbrains.kotlin.fir.deserialization.FirBuiltinAnnotationDeserializer
 import org.jetbrains.kotlin.fir.deserialization.FirDeserializationContext
 import org.jetbrains.kotlin.fir.deserialization.deserializeClassToSymbol
 import org.jetbrains.kotlin.fir.resolve.FirSymbolProvider
-import org.jetbrains.kotlin.fir.resolve.constructClassType
 import org.jetbrains.kotlin.fir.resolve.getOrPut
 import org.jetbrains.kotlin.fir.scopes.FirScope
 import org.jetbrains.kotlin.fir.scopes.KotlinScopeProvider
@@ -29,6 +31,7 @@ import org.jetbrains.kotlin.fir.symbols.StandardClassIds
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.FirResolvedTypeRef
 import org.jetbrains.kotlin.fir.types.builder.buildResolvedTypeRef
+import org.jetbrains.kotlin.fir.types.constructClassType
 import org.jetbrains.kotlin.fir.types.impl.ConeTypeParameterTypeImpl
 import org.jetbrains.kotlin.metadata.ProtoBuf
 import org.jetbrains.kotlin.metadata.builtins.BuiltInsBinaryVersion
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/InferenceUtil.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/InferenceComponents.kt
similarity index 67%
rename from compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/InferenceUtil.kt
rename to compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/InferenceComponents.kt
index a06ac15f543..e416f3b7840 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/InferenceUtil.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/InferenceComponents.kt
@@ -7,10 +7,9 @@ package org.jetbrains.kotlin.fir.resolve.inference
 
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
-import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.resolve.transformers.ReturnTypeCalculator
-import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
-import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.fir.types.ConeClassErrorType
+import org.jetbrains.kotlin.fir.types.ConeInferenceContext
 import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintIncorporator
 import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintInjector
 import org.jetbrains.kotlin.resolve.calls.inference.components.ResultTypeResolver
@@ -20,25 +19,6 @@ import org.jetbrains.kotlin.types.AbstractTypeApproximator
 import org.jetbrains.kotlin.types.checker.KotlinTypeRefiner
 import org.jetbrains.kotlin.types.model.SimpleTypeMarker
 
-fun ConeTypeContext.hasNullableSuperType(type: ConeKotlinType): Boolean {
-    if (type is ConeClassLikeType) return false
-
-    if (type !is ConeLookupTagBasedType) return false // TODO?
-    val symbol = type.lookupTag.toSymbol(session) ?: return false // TODO?!
-    for (superType in symbol.supertypes()) {
-        if (superType.isNullableType()) return true
-    }
-//
-//    for (KotlinType supertype : getImmediateSupertypes(type)) {
-//        if (isNullableType(supertype)) return true;
-//    }
-
-    return false
-}
-
-class TypeParameterBasedTypeVariable(val typeParameterSymbol: FirTypeParameterSymbol) :
-    ConeTypeVariable(typeParameterSymbol.name.identifier)
-
 class InferenceComponents(
     val ctx: ConeInferenceContext,
     val session: FirSession,
@@ -50,7 +30,9 @@ class InferenceComponents(
             return ConeClassErrorType(message)
         }
     }
-    val trivialConstraintTypeInferenceOracle = TrivialConstraintTypeInferenceOracle.create(ctx)
+    val trivialConstraintTypeInferenceOracle =
+        TrivialConstraintTypeInferenceOracle
+            .create(ctx)
     private val incorporator = ConstraintIncorporator(approximator, trivialConstraintTypeInferenceOracle)
     private val injector = ConstraintInjector(incorporator, approximator, KotlinTypeRefiner.Default)
     val resultTypeResolver = ResultTypeResolver(approximator, trivialConstraintTypeInferenceOracle)
@@ -59,5 +41,4 @@ class InferenceComponents(
         return NewConstraintSystemImpl(injector, ctx)
     }
 
-}
-
+}
\ No newline at end of file
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/TypeParameterBasedTypeVariable.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/TypeParameterBasedTypeVariable.kt
new file mode 100644
index 00000000000..061ccdfe655
--- /dev/null
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/TypeParameterBasedTypeVariable.kt
@@ -0,0 +1,12 @@
+/*
+ * Copyright 2010-2020 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.inference
+
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
+import org.jetbrains.kotlin.fir.types.ConeTypeVariable
+
+class TypeParameterBasedTypeVariable(val typeParameterSymbol: FirTypeParameterSymbol) :
+    ConeTypeVariable(typeParameterSymbol.name.identifier)
\ No newline at end of file
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt
index b4de2249773..13e737a1283 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt
@@ -5,7 +5,6 @@
 
 package org.jetbrains.kotlin.fir.resolve.substitution
 
-import org.jetbrains.kotlin.fir.resolve.withNullability
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.impl.ConeClassLikeTypeImpl
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompletionResultsWriterTransformer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompletionResultsWriterTransformer.kt
index 79d54815aa0..01875c69837 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompletionResultsWriterTransformer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompletionResultsWriterTransformer.kt
@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.fir.resolve.inference.returnType
 import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.substitution.substituteOrNull
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.resultType
-import org.jetbrains.kotlin.fir.resolve.withNullability
 import org.jetbrains.kotlin.fir.scopes.impl.FirIntegerOperatorCall
 import org.jetbrains.kotlin.fir.scopes.impl.withReplacedConeType
 import org.jetbrains.kotlin.fir.types.*
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt
index 7594b1ccf32..7cce5d4984b 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt
@@ -27,7 +27,6 @@ import org.jetbrains.kotlin.fir.resolve.calls.*
 import org.jetbrains.kotlin.fir.resolve.diagnostics.FirUnresolvedNameError
 import org.jetbrains.kotlin.fir.resolve.inference.FirCallCompleter
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.FirAbstractBodyResolveTransformer
-import org.jetbrains.kotlin.fir.resolve.withNullability
 import org.jetbrains.kotlin.fir.symbols.CallableId
 import org.jetbrains.kotlin.fir.symbols.SyntheticCallableId
 import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeContext.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeContext.kt
index 64b0f0bb06e..f1a75c016f9 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeContext.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeContext.kt
@@ -10,10 +10,11 @@ import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.*
-import org.jetbrains.kotlin.fir.resolve.*
-import org.jetbrains.kotlin.fir.resolve.inference.hasNullableSuperType
+import org.jetbrains.kotlin.fir.resolve.correspondingSupertypesCache
+import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.substitution.substitutorByMap
+import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.firUnsafe
 import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.StandardClassIds
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/FirCorrespondingSupertypesCache.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/FirCorrespondingSupertypesCache.kt
index 8fd497b22b1..65ba37e7124 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/FirCorrespondingSupertypesCache.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/FirCorrespondingSupertypesCache.kt
@@ -9,8 +9,6 @@ import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.FirSessionComponent
 import org.jetbrains.kotlin.fir.declarations.FirClassLikeDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirTypeParametersOwner
-import org.jetbrains.kotlin.fir.resolve.constructClassType
-import org.jetbrains.kotlin.fir.resolve.constructType
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
 import org.jetbrains.kotlin.types.AbstractTypeCheckerContext
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt
index 635503ff0ba..f162fd71b33 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt
@@ -5,10 +5,17 @@
 
 package org.jetbrains.kotlin.fir.types
 
-import org.jetbrains.kotlin.fir.resolve.withNullability
+import org.jetbrains.kotlin.fir.resolve.toSymbol
+import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
+import org.jetbrains.kotlin.fir.symbols.ConeClassifierLookupTag
+import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterLookupTag
+import org.jetbrains.kotlin.fir.types.impl.ConeClassLikeTypeImpl
+import org.jetbrains.kotlin.fir.types.impl.ConeTypeParameterTypeImpl
 import org.jetbrains.kotlin.resolve.calls.NewCommonSuperTypeCalculator
 import org.jetbrains.kotlin.types.AbstractNullabilityChecker
+import org.jetbrains.kotlin.types.AbstractStrictEqualityTypeChecker
 import org.jetbrains.kotlin.types.AbstractTypeCheckerContext
+import org.jetbrains.kotlin.types.Variance
 
 object ConeNullabilityChecker {
     fun isSubtypeOfAny(context: ConeTypeContext, type: ConeKotlinType): Boolean {
@@ -76,4 +83,116 @@ fun ConeKotlinType.makeConeTypeDefinitelyNotNullOrNotNull(): ConeKotlinType {
         return ConeIntersectionType(intersectedTypes.map { it.makeConeTypeDefinitelyNotNullOrNotNull() })
     }
     return ConeDefinitelyNotNullType.create(this) ?: this.withNullability(ConeNullability.NOT_NULL)
+}
+
+fun <T : ConeKotlinType> T.withArguments(arguments: Array<out ConeKotlinTypeProjection>): T {
+    if (this.typeArguments === arguments) {
+        return this
+    }
+
+    return when (this) {
+        is ConeClassErrorType -> this
+        is ConeClassLikeTypeImpl -> ConeClassLikeTypeImpl(lookupTag, arguments, nullability.isNullable) as T
+        is ConeDefinitelyNotNullType -> ConeDefinitelyNotNullType.create(original.withArguments(arguments))!! as T
+        else -> error("Not supported: $this: ${this.render()}")
+    }
+}
+
+fun ConeTypeContext.hasNullableSuperType(type: ConeKotlinType): Boolean {
+    if (type is ConeClassLikeType) return false
+
+    if (type !is ConeLookupTagBasedType) return false // TODO?
+    val symbol = type.lookupTag.toSymbol(session) ?: return false // TODO?!
+    for (superType in symbol.supertypes()) {
+        if (superType.isNullableType()) return true
+    }
+//
+//    for (KotlinType supertype : getImmediateSupertypes(type)) {
+//        if (isNullableType(supertype)) return true;
+//    }
+
+    return false
+}
+
+fun <T : ConeKotlinType> T.withNullability(nullability: ConeNullability, typeContext: ConeInferenceContext? = null): T {
+    if (this.nullability == nullability) {
+        return this
+    }
+
+    return when (this) {
+        is ConeClassErrorType -> this
+        is ConeClassLikeTypeImpl -> ConeClassLikeTypeImpl(lookupTag, typeArguments, nullability.isNullable) as T
+        is ConeTypeParameterTypeImpl -> ConeTypeParameterTypeImpl(lookupTag, nullability.isNullable) as T
+        is ConeFlexibleType -> {
+            if (nullability == ConeNullability.UNKNOWN) {
+                if (lowerBound.nullability != upperBound.nullability || lowerBound.nullability == ConeNullability.UNKNOWN) {
+                    return this
+                }
+            }
+            coneFlexibleOrSimpleType(typeContext, lowerBound.withNullability(nullability), upperBound.withNullability(nullability)) as T
+        }
+        is ConeTypeVariableType -> ConeTypeVariableType(nullability, lookupTag) as T
+        is ConeCapturedType -> ConeCapturedType(captureStatus, lowerType, nullability, constructor) as T
+        is ConeIntersectionType -> when (nullability) {
+            ConeNullability.NULLABLE -> this.mapTypes {
+                it.withNullability(nullability)
+            }
+            ConeNullability.UNKNOWN -> this // TODO: is that correct?
+            ConeNullability.NOT_NULL -> this
+        } as T
+        is ConeStubType -> ConeStubType(variable, nullability) as T
+        is ConeDefinitelyNotNullType -> when (nullability) {
+            ConeNullability.NOT_NULL -> this
+            ConeNullability.NULLABLE -> original.withNullability(nullability)
+            ConeNullability.UNKNOWN -> original.withNullability(nullability)
+        } as T
+        is ConeIntegerLiteralType -> this
+        else -> error("sealed: ${this::class}")
+    }
+}
+
+fun coneFlexibleOrSimpleType(
+    typeContext: ConeInferenceContext?,
+    lowerBound: ConeKotlinType,
+    upperBound: ConeKotlinType,
+): ConeKotlinType {
+    if (lowerBound is ConeFlexibleType) {
+        return coneFlexibleOrSimpleType(typeContext, lowerBound.lowerBound, upperBound)
+    }
+    if (upperBound is ConeFlexibleType) {
+        return coneFlexibleOrSimpleType(typeContext, lowerBound, upperBound.upperBound)
+    }
+    return when {
+        typeContext != null && AbstractStrictEqualityTypeChecker.strictEqualTypes(typeContext, lowerBound, upperBound) -> {
+            lowerBound
+        }
+        typeContext == null && lowerBound == upperBound -> {
+            lowerBound
+        }
+        else -> {
+            ConeFlexibleType(lowerBound, upperBound)
+        }
+    }
+}
+
+fun ConeKotlinType.toTypeProjection(variance: Variance): ConeKotlinTypeProjection =
+    when (variance) {
+        Variance.INVARIANT -> this
+        Variance.IN_VARIANCE -> ConeKotlinTypeProjectionIn(this)
+        Variance.OUT_VARIANCE -> ConeKotlinTypeProjectionOut(this)
+    }
+
+fun ConeClassLikeLookupTag.constructClassType(
+    typeArguments: Array<out ConeKotlinTypeProjection>,
+    isNullable: Boolean,
+): ConeLookupTagBasedType {
+    return ConeClassLikeTypeImpl(this, typeArguments, isNullable)
+}
+
+fun ConeClassifierLookupTag.constructType(typeArguments: Array<ConeKotlinTypeProjection>, isNullable: Boolean): ConeLookupTagBasedType {
+    return when (this) {
+        is ConeTypeParameterLookupTag -> ConeTypeParameterTypeImpl(this, isNullable)
+        is ConeClassLikeLookupTag -> this.constructClassType(typeArguments, isNullable)
+        else -> error("! ${this::class}")
+    }
 }
\ No newline at end of file