diff --git a/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt b/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt
index 56ecfd2d540..98e101ab2b4 100644
--- a/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt
+++ b/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt
@@ -173,4 +173,53 @@ class ConeDefinitelyNotNullType(val original: ConeKotlinType): ConeKotlinType(),
         get() = original.typeArguments
     override val nullability: ConeNullability
         get() = ConeNullability.NOT_NULL
+}
+
+/*
+ * Contract of the intersection type: it is flat. It means that
+ *   intersection type can not contains another intersection types
+ *   inside it. To keep this contract construct new intersection types
+ *   only via ConeTypeIntersector
+ */
+class ConeIntersectionType(
+    val constructor: ConeIntersectionTypeConstructor
+) : ConeKotlinType(), SimpleTypeMarker {
+    override val typeArguments: Array<out ConeKotlinTypeProjection>
+        get() = emptyArray()
+
+    override val nullability: ConeNullability
+        get() = ConeNullability.NOT_NULL
+
+    val intersectedTypes: Collection<ConeKotlinType> get() = constructor.intersectedTypes
+    val statusMap: Map<ConeKotlinType, ConeIntersectionTypeConstructor.IntersectionStatus> get() = constructor.statusMap
+}
+
+class ConeIntersectionTypeConstructor(
+    val intersectedTypes: Collection<ConeKotlinType>,
+    val statusMap: Map<ConeKotlinType, IntersectionStatus>
+) : TypeConstructorMarker {
+    val supertypes: Collection<ConeKotlinType> get() = intersectedTypes
+
+    /*
+     * IMPORTANT: use this method only for types from intersectedTypes
+     */
+    fun getStatus(type: ConeKotlinType): IntersectionStatus {
+        return statusMap[type] ?: error("")
+    }
+
+    enum class IntersectionStatus {
+        FROM_INFERENCE,
+        FROM_SMARTCAST
+    }
+}
+
+fun ConeIntersectionTypeConstructor.mapTypes(func: (ConeKotlinType) -> ConeKotlinType): ConeIntersectionTypeConstructor {
+    val newStatusMap = mutableMapOf<ConeKotlinType, ConeIntersectionTypeConstructor.IntersectionStatus>()
+    val newTypes = intersectedTypes.map { type ->
+        val newType = func(type)
+        // TODO: what if some types squash? What status should we choose?
+        newStatusMap[newType] = getStatus(type)
+        newType
+    }
+    return ConeIntersectionTypeConstructor(newTypes, newStatusMap)
 }
\ No newline at end of file
diff --git a/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/TypeRenderer.kt b/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/TypeRenderer.kt
index ae7bef7b86d..f8b278e5528 100644
--- a/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/TypeRenderer.kt
+++ b/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/TypeRenderer.kt
@@ -39,5 +39,12 @@ fun ConeKotlinType.render(): String {
                 append(">")
             }
         }
+        is ConeIntersectionType -> {
+            intersectedTypes.joinToString(
+                separator = " & ",
+                prefix = "it(",
+                postfix = ")"
+            )
+        }
     } + nullabilitySuffix
 }
diff --git a/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt b/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
index 0c4e7af4c42..b2ea888529a 100644
--- a/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
+++ b/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
@@ -599,6 +599,12 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
         }
     }
 
+    private fun FlowContent.generate(intersectionType: ConeIntersectionType) {
+        +"("
+        generateList(intersectionType.intersectedTypes.toList(), " & ") { generate(it) }
+        +")"
+    }
+
     private fun FlowContent.generate(type: ConeClassType) {
         resolved {
             symbolRef(type.lookupTag.toSymbol(session)) {
@@ -704,6 +710,7 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
             is ConeFlexibleType -> resolved { generate(type) }
             is ConeCapturedType -> inlineUnsupported(type)
             is ConeDefinitelyNotNullType -> inlineUnsupported(type)
+            is ConeIntersectionType -> resolved { generate(type) }
         }
         if (type.typeArguments.isNotEmpty()) {
             +"<"
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt
index 3d3c57234c5..d8324967275 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt
@@ -58,6 +58,10 @@ fun ConeKotlinType.toIrType(session: FirSession, declarationStorage: Fir2IrDecla
         }
         is ConeCapturedType -> TODO()
         is ConeDefinitelyNotNullType -> TODO()
+        is ConeIntersectionType -> {
+            // TODO: add intersectionTypeApproximation
+            intersectedTypes.first().toIrType(session, declarationStorage)
+        }
     }
 }
 
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 59490b38d0a..8a5afb57f78 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
@@ -164,6 +164,13 @@ fun <T : ConeKotlinType> T.withNullability(nullability: ConeNullability): T {
         is ConeFlexibleType -> ConeFlexibleType(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 -> ConeIntersectionType(constructor.mapTypes {
+                it.withNullability(nullability)
+            })
+            ConeNullability.UNKNOWN -> this // TODO: is that correct?
+            ConeNullability.NOT_NULL -> this
+        } as T
         else -> error("sealed: ${this::class}")
     }
 }
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ScopeUtils.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ScopeUtils.kt
index 531dd264791..1d08d96604d 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ScopeUtils.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ScopeUtils.kt
@@ -38,6 +38,7 @@ fun ConeKotlinType.scope(useSiteSession: FirSession, scopeSession: ScopeSession)
             )
         }
         is ConeFlexibleType -> lowerBound.scope(useSiteSession, scopeSession)
+        is ConeIntersectionType -> FirCompositeScope(intersectedTypes.mapNotNullTo(mutableListOf()) { it.scope(useSiteSession, scopeSession) })
         else -> error("Failed type ${this}")
     }
 }
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt
index 073fd2bd697..1f031204198 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt
@@ -75,9 +75,23 @@ abstract class AbstractConeSubstitutor : ConeSubstitutor() {
             is ConeFlexibleType -> this.substituteBounds()
             is ConeCapturedType -> return null
             is ConeDefinitelyNotNullType -> this.substituteOriginal()
+            is ConeIntersectionType -> this.substituteIntersectedTypes()
         }
     }
 
+    private fun ConeIntersectionType.substituteIntersectedTypes(): ConeIntersectionType? {
+        val substitutedTypes = ArrayList<ConeKotlinType>(intersectedTypes.size)
+        var somethingIsSubstituted = false
+        for (type in intersectedTypes) {
+            val substitutedType = substituteOrNull(type)?.also {
+                somethingIsSubstituted = true
+            } ?: type
+            substitutedTypes += substitutedType
+        }
+        if (!somethingIsSubstituted) return null
+        return ConeIntersectionType(ConeIntersectionTypeConstructor(substitutedTypes, statusMap))
+    }
+
     private fun ConeDefinitelyNotNullType.substituteOriginal(): ConeDefinitelyNotNullType? {
         TODO()
     }
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 ce7c7fca250..42c9e972533 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
@@ -60,6 +60,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
             is ConeCapturedType -> this
             is ConeLookupTagBasedType -> this
             is ConeDefinitelyNotNullType -> this
+            is ConeIntersectionType -> this
             is ConeFlexibleType -> null
             else -> error("Unknown simpleType: $this")
         }
@@ -128,6 +129,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
                 typeArguments,
                 nullable
             )
+            is ConeIntersectionType -> this.withNullability(ConeNullability.create(nullable))
             else -> error("!")
         }
     }
@@ -139,6 +141,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
             is ConeAbbreviatedType -> this.directExpansionType(session)?.typeConstructor()
                 ?: ErrorTypeConstructor("Failed to expand alias: ${this}")
             is ConeLookupTagBasedType -> this.lookupTag.toSymbol(session) ?: ErrorTypeConstructor("Unresolved: ${this.lookupTag}")
+            is ConeIntersectionType -> constructor
             else -> error("?: ${this}")
         }
 
@@ -199,7 +202,11 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
     override fun TypeConstructorMarker.parametersCount(): Int {
         //require(this is ConeSymbol)
         return when (this) {
-            is ConeTypeParameterSymbol, is ConeCapturedTypeConstructor, is ErrorTypeConstructor, is ConeTypeVariableTypeConstructor -> 0
+            is ConeTypeParameterSymbol,
+            is ConeCapturedTypeConstructor,
+            is ErrorTypeConstructor,
+            is ConeTypeVariableTypeConstructor,
+            is ConeIntersectionTypeConstructor -> 0
             is FirClassSymbol -> fir.typeParameters.size
             is FirTypeAliasSymbol -> fir.typeParameters.size
             else -> error("?!:10")
@@ -225,12 +232,13 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
             is FirClassSymbol -> fir.superConeTypes
             is FirTypeAliasSymbol -> listOfNotNull(fir.expandedConeType)
             is ConeCapturedTypeConstructor -> supertypes!!
+            is ConeIntersectionTypeConstructor -> intersectedTypes
             else -> error("?!:13")
         }
     }
 
     override fun TypeConstructorMarker.isIntersection(): Boolean {
-        return false // TODO
+        return this is ConeIntersectionTypeConstructor
     }
 
     override fun TypeConstructorMarker.isClassTypeConstructor(): Boolean {
@@ -269,8 +277,9 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
     override fun TypeConstructorMarker.isDenotable(): Boolean {
         //TODO
         return when (this) {
-            is ConeCapturedTypeConstructor -> false
-            is ConeTypeVariableTypeConstructor -> false
+            is ConeCapturedTypeConstructor,
+            is ConeTypeVariableTypeConstructor,
+            is ConeIntersectionTypeConstructor -> false
             is ConeSymbol -> true
             else -> true
         }
@@ -351,6 +360,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
         if (isError()) return false
         if (this is ConeCapturedType) return true
         if (this is ConeTypeVariableType) return false
+        if (this is ConeIntersectionType) return false
         require(this is ConeLookupTagBasedType)
         val typeConstructor = this.typeConstructor()
         return typeConstructor is FirClassSymbol ||
@@ -370,11 +380,13 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
     }
 
     override fun intersectTypes(types: List<SimpleTypeMarker>): SimpleTypeMarker {
-        return types.first() // TODO: proper implementation
+        @Suppress("UNCHECKED_CAST")
+        return ConeTypeIntersector.intersectTypes(this, types as List<ConeKotlinType>) as SimpleTypeMarker
     }
 
     override fun intersectTypes(types: List<KotlinTypeMarker>): KotlinTypeMarker {
-        return types.first() // TODO: proper implementation
+        @Suppress("UNCHECKED_CAST")
+        return ConeTypeIntersector.intersectTypes(this, types as List<ConeKotlinType>)
     }
 
     private fun prepareClassLikeType(
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeIntersector.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeIntersector.kt
new file mode 100644
index 00000000000..4fb1baf0f75
--- /dev/null
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeIntersector.kt
@@ -0,0 +1,185 @@
+/*
+ * Copyright 2010-2019 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.types
+
+import org.jetbrains.kotlin.fir.resolve.calls.ConeInferenceContext
+import org.jetbrains.kotlin.fir.types.ConeIntersectionTypeConstructor.IntersectionStatus
+import org.jetbrains.kotlin.types.AbstractTypeChecker
+import java.util.*
+import kotlin.collections.LinkedHashSet
+
+object ConeTypeIntersector {
+    fun intersectTypes(context: ConeTypeContext, types: List<ConeKotlinType>): ConeKotlinType {
+        require(context is ConeInferenceContext)
+        return intersectTypes(context, types, types.map { IntersectionStatus.FROM_INFERENCE })
+    }
+
+    private fun intersectTypes(
+        context: ConeInferenceContext,
+        types: List<ConeKotlinType>,
+        intersectionStatus: List<IntersectionStatus>
+    ): ConeKotlinType {
+        assert(types.size == intersectionStatus.size)
+
+        when (types.size) {
+            0 -> error("Expected some types")
+            1 -> return types.single()
+        }
+
+        val inputTypes = mutableListOf<ConeKotlinType>()
+        val statusMap = mutableMapOf<ConeKotlinType, IntersectionStatus>()
+        flatIntersectionTypes(types, intersectionStatus, inputTypes, statusMap)
+
+        /**
+         * resultNullability. Value description:
+         * ACCEPT_NULL means that all types marked nullable
+         *
+         * NOT_NULL means that there is one type which is subtype of Any => all types can be made definitely not null,
+         * making types definitely not null (not just not null) makes sense when we have intersection of type parameters like {T!! & S}
+         *
+         * UNKNOWN means, that we do not know, i.e. more precisely, all singleClassifier types marked nullable if any,
+         * and other types is captured types or type parameters without not-null upper bound. Example: `String? & T` such types we should leave as is.
+         */
+        val resultNullability = inputTypes.fold(ResultNullability.START) { nullability, nextType ->
+            nullability.combine(nextType.type, context)
+        }
+
+        val inputTypesWithCorrectNullability = inputTypes.mapTo(LinkedHashSet()) {
+            if (resultNullability == ResultNullability.NOT_NULL) with(context) {
+                val resultType = it.makeDefinitelyNotNullOrNotNull() as ConeKotlinType
+                statusMap[resultType] = statusMap.remove(it)!!
+                resultType
+            } else it
+        }
+
+        return intersectTypesWithoutIntersectionType(context, inputTypesWithCorrectNullability, statusMap)
+    }
+
+    private fun intersectTypesWithoutIntersectionType(
+        context: ConeTypeContext,
+        inputTypes: Set<ConeKotlinType>,
+        statusMap: MutableMap<ConeKotlinType, IntersectionStatus>
+    ): ConeKotlinType {
+        if (inputTypes.size == 1) return inputTypes.single().type
+
+        // Any and Nothing should leave
+        // Note that duplicates should be dropped because we have Set here.
+        val errorMessage = { "This collections cannot be empty! input types: ${inputTypes.joinToString()}" }
+
+        val filteredEqualTypes = filterTypes(inputTypes) { lower, upper ->
+            /*
+             * Here we drop types from intersection set for cases like that:
+             *
+             * interface A
+             * interface B : A
+             *
+             * type = (A & B & ...)
+             *
+             * We want to drop A from that set, because it's useless for type checking. But in case if
+             *   A came from inference and B came from smartcast we want to safe both types in intersection
+             */
+            isStrictSupertype(context, lower, upper) && statusMap[lower]!! <= statusMap[upper]!!
+        }
+        assert(filteredEqualTypes.isNotEmpty(), errorMessage)
+
+        // TODO
+        // IntegerLiteralTypeConstructor.findIntersectionType(filteredEqualTypes)?.let { return it }
+
+        val filteredSuperAndEqualTypes = filterTypes(filteredEqualTypes) { a, b ->
+            AbstractTypeChecker.equalTypes(context, a, b)
+        }
+        assert(filteredSuperAndEqualTypes.isNotEmpty(), errorMessage)
+
+        if (filteredSuperAndEqualTypes.size < 2) return filteredSuperAndEqualTypes.single()
+
+        val constructor = ConeIntersectionTypeConstructor(
+            filteredSuperAndEqualTypes,
+            filteredSuperAndEqualTypes.associateWithTo(mutableMapOf()) { statusMap[it]!! }
+        )
+        return ConeIntersectionType(constructor)
+    }
+
+    private fun filterTypes(
+        inputTypes: Collection<ConeKotlinType>,
+        predicate: (lower: ConeKotlinType, upper: ConeKotlinType) -> Boolean
+    ): List<ConeKotlinType> {
+        val filteredTypes = ArrayList(inputTypes)
+        val iterator = filteredTypes.iterator()
+        while (iterator.hasNext()) {
+            val upper = iterator.next()
+            val shouldFilter = filteredTypes.any { lower -> lower !== upper && predicate(lower, upper) }
+
+            if (shouldFilter) iterator.remove()
+        }
+        return filteredTypes
+    }
+
+    private fun isStrictSupertype(context: ConeTypeContext, subtype: ConeKotlinType, supertype: ConeKotlinType): Boolean {
+        return with(AbstractTypeChecker) {
+            isSubtypeOf(context, subtype, supertype) && !isSubtypeOf(context, supertype, subtype)
+        }
+    }
+
+    @Suppress("NOTHING_TO_INLINE")
+    private inline fun MutableMap<ConeKotlinType, IntersectionStatus>.updateStatus(type: ConeKotlinType, status: IntersectionStatus) {
+        // We should keep status FROM_SMARTCAST for correct diagnostic reporting
+        val existingStatus = get(type)
+        if (existingStatus == null) {
+            put(type, status)
+        } else {
+            put(type, minOf(status, existingStatus))
+        }
+    }
+
+    private fun flatIntersectionTypes(
+        inputTypes: List<ConeKotlinType>,
+        intersectionStatus: List<IntersectionStatus>,
+        typeCollector: MutableList<ConeKotlinType>,
+        statusMap: MutableMap<ConeKotlinType, IntersectionStatus>
+    ) {
+        for ((inputType, status) in inputTypes.zip(intersectionStatus)) {
+            if (inputType is ConeIntersectionType) {
+                for (type in inputType.intersectedTypes) {
+                    typeCollector += type
+                    statusMap.updateStatus(type, status)
+                }
+            } else {
+                typeCollector += inputType
+                statusMap.updateStatus(inputType, status)
+            }
+        }
+    }
+
+    private enum class ResultNullability {
+        START {
+            override fun combine(nextType: ConeKotlinType, context: ConeTypeContext): ResultNullability =
+                nextType.resultNullability(context)
+        },
+        ACCEPT_NULL {
+            override fun combine(nextType: ConeKotlinType, context: ConeTypeContext): ResultNullability =
+                nextType.resultNullability(context)
+        },
+        // example: type parameter without not-null supertype
+        UNKNOWN {
+            override fun combine(nextType: ConeKotlinType, context: ConeTypeContext): ResultNullability =
+                nextType.resultNullability(context).let {
+                    if (it == ACCEPT_NULL) this else it
+                }
+        },
+        NOT_NULL {
+            override fun combine(nextType: ConeKotlinType, context: ConeTypeContext): ResultNullability = this
+        };
+
+        abstract fun combine(nextType: ConeKotlinType, context: ConeTypeContext): ResultNullability
+
+        protected fun ConeKotlinType.resultNullability(context: ConeTypeContext): ResultNullability =
+            when {
+                isMarkedNullable -> ACCEPT_NULL
+                ConeNullabilityChecker.isSubtypeOfAny(context, this) -> NOT_NULL
+                else -> UNKNOWN
+            }
+    }
+}
\ No newline at end of file
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
new file mode 100644
index 00000000000..ce2aedcb618
--- /dev/null
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt
@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2019 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.types
+
+import org.jetbrains.kotlin.types.AbstractNullabilityChecker
+import org.jetbrains.kotlin.types.AbstractTypeCheckerContext
+
+object ConeNullabilityChecker {
+    fun isSubtypeOfAny(context: ConeTypeContext, type: ConeKotlinType): Boolean {
+        val actualType = with(context) { type.lowerBoundIfFlexible() }
+        return with(AbstractNullabilityChecker) {
+            context.newBaseTypeCheckerContext(false)
+                .hasNotNullSupertype(actualType, AbstractTypeCheckerContext.SupertypesPolicy.LowerIfFlexible)
+        }
+    }
+}
\ No newline at end of file
diff --git a/compiler/fir/resolve/testData/resolve/intersectionTypes.kt b/compiler/fir/resolve/testData/resolve/intersectionTypes.kt
new file mode 100644
index 00000000000..96ce7df60d9
--- /dev/null
+++ b/compiler/fir/resolve/testData/resolve/intersectionTypes.kt
@@ -0,0 +1,14 @@
+interface A
+
+interface B
+
+class Clazz1 : A, B
+class Clazz2 : A, B
+
+fun <K> select(x: K, y: K): K
+
+fun test() = select(Clazz1(), Clazz2())
+
+fun <T> makeNull(x: T): T? = null
+
+fun testNull() = makeNull(select(Clazz1(), Clazz2()))
\ No newline at end of file
diff --git a/compiler/fir/resolve/testData/resolve/intersectionTypes.txt b/compiler/fir/resolve/testData/resolve/intersectionTypes.txt
index 4d7759be1c0..c1b24d926d3 100644
--- a/compiler/fir/resolve/testData/resolve/intersectionTypes.txt
+++ b/compiler/fir/resolve/testData/resolve/intersectionTypes.txt
@@ -19,9 +19,9 @@ FILE: intersectionTypes.kt
     public final fun test(): R|it(A & B)| {
         ^test R|/select|<R|it(A & B)|>(R|/Clazz1.Clazz1|(), R|/Clazz2.Clazz2|())
     }
-    public final fun <T> makeNull(x: R|T|): R|T|? {
+    public final fun <T> makeNull(x: R|T|): R|T?| {
         ^makeNull Null(null)
     }
-    public final fun testNull(): R|it(A & B)| {
+    public final fun testNull(): R|it(A? & B?)| {
         ^testNull R|/makeNull|<R|it(A & B)|>(R|/select|<R|it(A & B)|>(R|/Clazz1.Clazz1|(), R|/Clazz2.Clazz2|()))
     }
diff --git a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirResolveTestCaseGenerated.java b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirResolveTestCaseGenerated.java
index 2be4be3193d..67c3f787af6 100644
--- a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirResolveTestCaseGenerated.java
+++ b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirResolveTestCaseGenerated.java
@@ -94,6 +94,11 @@ public class FirResolveTestCaseGenerated extends AbstractFirResolveTestCase {
         runTest("compiler/fir/resolve/testData/resolve/genericFunctions.kt");
     }
 
+    @TestMetadata("intersectionTypes.kt")
+    public void testIntersectionTypes() throws Exception {
+        runTest("compiler/fir/resolve/testData/resolve/intersectionTypes.kt");
+    }
+
     @TestMetadata("nestedClass.kt")
     public void testNestedClass() throws Exception {
         runTest("compiler/fir/resolve/testData/resolve/nestedClass.kt");
diff --git a/compiler/testData/ir/irText/types/intersectionType1_NI.fir.txt b/compiler/testData/ir/irText/types/intersectionType1_NI.fir.txt
index d6d41289953..13f8c458068 100644
--- a/compiler/testData/ir/irText/types/intersectionType1_NI.fir.txt
+++ b/compiler/testData/ir/irText/types/intersectionType1_NI.fir.txt
@@ -34,7 +34,7 @@ FILE fqName:<root> fileName:/intersectionType1_NI.kt
       RETURN type=kotlin.Nothing from='public final fun foo <T> (a: kotlin.Array<<root>.In<T of <root>.foo>>, b: kotlin.Array<<root>.In<kotlin.String>>): kotlin.Boolean declared in <root>'
         CALL 'public final fun ofType <K> (y: kotlin.Any?): kotlin.Boolean [inline] declared in <root>' type=kotlin.Boolean origin=null
           $receiver: CALL 'public final fun get (index: kotlin.Int): <root>.In<T of <root>.foo> declared in kotlin.Array' type=<root>.In<T of <root>.foo> origin=null
-            $this: CALL 'public final fun select <S> (x: S of <root>.select, y: S of <root>.select): S of <root>.select declared in <root>' type=kotlin.Array<<root>.In<T of <root>.foo>> origin=null
+            $this: CALL 'public final fun select <S> (x: S of <root>.select, y: S of <root>.select): S of <root>.select declared in <root>' type=kotlin.Array<out <root>.In<T of <root>.foo>> origin=null
               <S>: <none>
               x: GET_VAR 'a: kotlin.Array<<root>.In<T of <root>.foo>> declared in <root>.foo' type=kotlin.Array<<root>.In<T of <root>.foo>> origin=null
               y: GET_VAR 'b: kotlin.Array<<root>.In<kotlin.String>> declared in <root>.foo' type=kotlin.Array<<root>.In<kotlin.String>> origin=null
diff --git a/compiler/testData/ir/irText/types/intersectionType1_OI.fir.txt b/compiler/testData/ir/irText/types/intersectionType1_OI.fir.txt
index 939eafa058f..a460eab0281 100644
--- a/compiler/testData/ir/irText/types/intersectionType1_OI.fir.txt
+++ b/compiler/testData/ir/irText/types/intersectionType1_OI.fir.txt
@@ -34,7 +34,7 @@ FILE fqName:<root> fileName:/intersectionType1_OI.kt
       RETURN type=kotlin.Nothing from='public final fun foo <T> (a: kotlin.Array<<root>.In<T of <root>.foo>>, b: kotlin.Array<<root>.In<kotlin.String>>): kotlin.Boolean declared in <root>'
         CALL 'public final fun ofType <K> (y: kotlin.Any?): kotlin.Boolean [inline] declared in <root>' type=kotlin.Boolean origin=null
           $receiver: CALL 'public final fun get (index: kotlin.Int): <root>.In<T of <root>.foo> declared in kotlin.Array' type=<root>.In<T of <root>.foo> origin=null
-            $this: CALL 'public final fun select <S> (x: S of <root>.select, y: S of <root>.select): S of <root>.select declared in <root>' type=kotlin.Array<<root>.In<T of <root>.foo>> origin=null
+            $this: CALL 'public final fun select <S> (x: S of <root>.select, y: S of <root>.select): S of <root>.select declared in <root>' type=kotlin.Array<out <root>.In<T of <root>.foo>> origin=null
               <S>: <none>
               x: GET_VAR 'a: kotlin.Array<<root>.In<T of <root>.foo>> declared in <root>.foo' type=kotlin.Array<<root>.In<T of <root>.foo>> origin=null
               y: GET_VAR 'b: kotlin.Array<<root>.In<kotlin.String>> declared in <root>.foo' type=kotlin.Array<<root>.In<kotlin.String>> origin=null
diff --git a/compiler/testData/ir/irText/types/intersectionType2_NI.fir.txt b/compiler/testData/ir/irText/types/intersectionType2_NI.fir.txt
index 4e723c57c78..f0bb3a91a0e 100644
--- a/compiler/testData/ir/irText/types/intersectionType2_NI.fir.txt
+++ b/compiler/testData/ir/irText/types/intersectionType2_NI.fir.txt
@@ -75,24 +75,24 @@ FILE fqName:<root> fileName:/intersectionType2_NI.kt
       RETURN type=kotlin.Nothing from='public final fun run <T> (fn: kotlin.Function0<T of <root>.run>): T of <root>.run declared in <root>'
         CALL 'public abstract fun invoke (): T of <root>.run declared in kotlin.Function0' type=T of <root>.run origin=null
           $this: GET_VAR 'fn: kotlin.Function0<T of <root>.run> declared in <root>.run' type=kotlin.Function0<T of <root>.run> origin=null
-  FUN name:foo visibility:public modality:FINAL <> () returnType:<root>.B
+  FUN name:foo visibility:public modality:FINAL <> () returnType:<root>.Foo
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun foo (): <root>.B declared in <root>'
-        CALL 'public final fun run <T> (fn: kotlin.Function0<T of <root>.run>): T of <root>.run declared in <root>' type=<root>.B origin=null
+      RETURN type=kotlin.Nothing from='public final fun foo (): <root>.Foo declared in <root>'
+        CALL 'public final fun run <T> (fn: kotlin.Function0<T of <root>.run>): T of <root>.run declared in <root>' type=<root>.Foo origin=null
           <T>: <none>
-          fn: FUN_EXPR type=kotlin.Function0<<root>.B> origin=LAMBDA
-            FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:<root>.B
+          fn: FUN_EXPR type=kotlin.Function0<<root>.Foo> origin=LAMBDA
+            FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:<root>.Foo
               BLOCK_BODY
                 VAR name:mm type:<root>.B [val]
                   CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.B' type=<root>.B origin=null
                 VAR name:nn type:<root>.C [val]
                   CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.C' type=<root>.C origin=null
-                VAR name:c type:<root>.B [val]
-                  WHEN type=<root>.B origin=IF
+                VAR name:c type:<root>.Foo [val]
+                  WHEN type=<root>.Foo origin=IF
                     BRANCH
                       if: CONST Boolean type=kotlin.Boolean value=true
                       then: GET_VAR 'val mm: <root>.B [val] declared in <root>.foo.<anonymous>' type=<root>.B origin=null
                     BRANCH
                       if: CONST Boolean type=kotlin.Boolean value=true
                       then: GET_VAR 'val nn: <root>.C [val] declared in <root>.foo.<anonymous>' type=<root>.C origin=null
-                GET_VAR 'val c: <root>.B [val] declared in <root>.foo.<anonymous>' type=<root>.B origin=null
+                GET_VAR 'val c: <root>.Foo [val] declared in <root>.foo.<anonymous>' type=<root>.Foo origin=null
diff --git a/compiler/testData/ir/irText/types/intersectionType2_OI.fir.txt b/compiler/testData/ir/irText/types/intersectionType2_OI.fir.txt
index 2458b15c566..c7dc4a3486a 100644
--- a/compiler/testData/ir/irText/types/intersectionType2_OI.fir.txt
+++ b/compiler/testData/ir/irText/types/intersectionType2_OI.fir.txt
@@ -75,24 +75,24 @@ FILE fqName:<root> fileName:/intersectionType2_OI.kt
       RETURN type=kotlin.Nothing from='public final fun run <T> (fn: kotlin.Function0<T of <root>.run>): T of <root>.run declared in <root>'
         CALL 'public abstract fun invoke (): T of <root>.run declared in kotlin.Function0' type=T of <root>.run origin=null
           $this: GET_VAR 'fn: kotlin.Function0<T of <root>.run> declared in <root>.run' type=kotlin.Function0<T of <root>.run> origin=null
-  FUN name:foo visibility:public modality:FINAL <> () returnType:<root>.B
+  FUN name:foo visibility:public modality:FINAL <> () returnType:<root>.Foo
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun foo (): <root>.B declared in <root>'
-        CALL 'public final fun run <T> (fn: kotlin.Function0<T of <root>.run>): T of <root>.run declared in <root>' type=<root>.B origin=null
+      RETURN type=kotlin.Nothing from='public final fun foo (): <root>.Foo declared in <root>'
+        CALL 'public final fun run <T> (fn: kotlin.Function0<T of <root>.run>): T of <root>.run declared in <root>' type=<root>.Foo origin=null
           <T>: <none>
-          fn: FUN_EXPR type=kotlin.Function0<<root>.B> origin=LAMBDA
-            FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:<root>.B
+          fn: FUN_EXPR type=kotlin.Function0<<root>.Foo> origin=LAMBDA
+            FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:<root>.Foo
               BLOCK_BODY
                 VAR name:mm type:<root>.B [val]
                   CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.B' type=<root>.B origin=null
                 VAR name:nn type:<root>.C [val]
                   CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.C' type=<root>.C origin=null
-                VAR name:c type:<root>.B [val]
-                  WHEN type=<root>.B origin=IF
+                VAR name:c type:<root>.Foo [val]
+                  WHEN type=<root>.Foo origin=IF
                     BRANCH
                       if: CONST Boolean type=kotlin.Boolean value=true
                       then: GET_VAR 'val mm: <root>.B [val] declared in <root>.foo.<anonymous>' type=<root>.B origin=null
                     BRANCH
                       if: CONST Boolean type=kotlin.Boolean value=true
                       then: GET_VAR 'val nn: <root>.C [val] declared in <root>.foo.<anonymous>' type=<root>.C origin=null
-                GET_VAR 'val c: <root>.B [val] declared in <root>.foo.<anonymous>' type=<root>.B origin=null
+                GET_VAR 'val c: <root>.Foo [val] declared in <root>.foo.<anonymous>' type=<root>.Foo origin=null