[FIR2IR] Approximate non-denotable types when converting ConeType to IrType

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt

@@ -236,7 +236,8 @@ class ConeRawType(lowerBound: ConeKotlinType, upperBound: ConeKotlinType) : Cone
  *   only via ConeTypeIntersector
  */
 class ConeIntersectionType(
-    val intersectedTypes: Collection<ConeKotlinType>
+    val intersectedTypes: Collection<ConeKotlinType>,
+    val alternativeType: ConeKotlinType? = null,
 ) : ConeSimpleKotlinType(), IntersectionTypeConstructorMarker {
     override val typeArguments: Array<out ConeTypeProjection>
         get() = emptyArray()
@@ -266,7 +267,10 @@ class ConeIntersectionType(
         if (hashCode != 0) return hashCode
         return intersectedTypes.hashCode().also { hashCode = it }
     }
+}
 
+fun ConeIntersectionType.withAlternative(alternativeType: ConeKotlinType): ConeIntersectionType {
+    return ConeIntersectionType(intersectedTypes, alternativeType)
 }
 
 fun ConeIntersectionType.mapTypes(func: (ConeKotlinType) -> ConeKotlinType): ConeIntersectionType {

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrTypeConverter.kt

@@ -8,8 +8,11 @@ package org.jetbrains.kotlin.fir.backend
 import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
 import org.jetbrains.kotlin.fir.expressions.classId
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
+import org.jetbrains.kotlin.fir.resolve.substitution.AbstractConeSubstitutor
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.symbols.StandardClassIds
+import org.jetbrains.kotlin.fir.typeContext
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.impl.*
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
@@ -20,6 +23,7 @@ import org.jetbrains.kotlin.ir.types.impl.IrSimpleTypeImpl
 import org.jetbrains.kotlin.ir.types.impl.IrStarProjectionImpl
 import org.jetbrains.kotlin.ir.types.impl.makeTypeProjection
 import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.types.TypeApproximatorConfiguration
 import org.jetbrains.kotlin.types.Variance
 
 class Fir2IrTypeConverter(
@@ -60,6 +64,8 @@ class Fir2IrTypeConverter(
     private val capturedTypeCache = mutableMapOf<ConeCapturedType, IrType>()
     private val errorTypeForCapturedTypeStub by lazy { createErrorType() }
 
+    private val typeApproximator = ConeTypeApproximator(session.typeContext)
+
     fun FirTypeRef.toIrType(typeContext: ConversionTypeContext = ConversionTypeContext.DEFAULT): IrType {
         capturedTypeCache.clear()
         return when (this) {
@@ -106,9 +112,10 @@ class Fir2IrTypeConverter(
                     typeAnnotations += callGenerator.convertToIrConstructorCall(attributeAnnotation) as? IrConstructorCall ?: continue
                 }
                 val expandedType = fullyExpandedType(session)
+                val approximatedType = approximateType(expandedType)
                 IrSimpleTypeImpl(
-                    irSymbol, !typeContext.definitelyNotNull && expandedType.isMarkedNullable,
-                    expandedType.typeArguments.map { it.toIrTypeArgument(typeContext) },
+                    irSymbol, !typeContext.definitelyNotNull && approximatedType.isMarkedNullable,
+                    approximatedType.typeArguments.map { it.toIrTypeArgument(typeContext) },
                     typeAnnotations
                 )
             }
@@ -211,6 +218,22 @@ class Fir2IrTypeConverter(
     private fun getBuiltInClassSymbol(classId: ClassId?): IrClassSymbol? {
         return classIdToSymbolMap[classId] ?: getArrayClassSymbol(classId)
     }
+
+    private fun approximateType(type: ConeKotlinType): ConeKotlinType {
+        if (type is ConeClassLikeType && type.typeArguments.isEmpty()) return type
+        val substitutor = object : AbstractConeSubstitutor() {
+            override fun substituteType(type: ConeKotlinType): ConeKotlinType? {
+                return if (type is ConeIntersectionType) {
+                    type.alternativeType?.let { substituteOrSelf(it) }
+                } else null
+            }
+        }
+        val typeWithSpecifiedIntersectionTypes = substitutor.substituteOrSelf(type)
+        return typeApproximator.approximateToSuperType(
+            typeWithSpecifiedIntersectionTypes,
+            TypeApproximatorConfiguration.PublicDeclaration
+        ) ?: type
+    }
 }
 
 fun FirTypeRef.toIrType(

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirBlackBoxCodegenTestGenerated.java

@@ -16616,6 +16616,12 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/inference/integerLiteralTypeInLamdaReturnType.kt");
         }
 
+        @Test
+        @TestMetadata("intersectionTypeInArguments.kt")
+        public void testIntersectionTypeInArguments() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/intersectionTypeInArguments.kt");
+        }
+
         @Test
         @TestMetadata("kt10822.kt")
         public void testKt10822() throws Exception {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeInferenceContext.kt

@@ -485,7 +485,11 @@ interface ConeInferenceContext : TypeSystemInferenceExtensionContext, ConeTypeCo
         firstCandidate: KotlinTypeMarker,
         secondCandidate: KotlinTypeMarker
     ): KotlinTypeMarker {
-        // TODO
-        return firstCandidate
+        require(firstCandidate is ConeKotlinType)
+        require(secondCandidate is ConeKotlinType)
+        val intersectionType = firstCandidate.lowerBoundIfFlexible() as? ConeIntersectionType ?: error {
+            "Expected type is intersection, found $firstCandidate"
+        }
+        return intersectionType.withAlternative(secondCandidate)
     }
 }