Expand ConeTypeContext, implement FIR type inference & related checkers

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

@@ -123,8 +123,9 @@ class ConeFlexibleType(val lowerBound: ConeLookupTagBasedType, val upperBound: C
         get() = lowerBound.nullability.takeIf { it == upperBound.nullability } ?: ConeNullability.UNKNOWN
 }
 
-class ConeCapturedTypeConstructor(val projection: ConeKotlinTypeProjection) : TypeConstructorMarker {
-    var supertypes: List<ConeKotlinType>? = null
+class ConeCapturedTypeConstructor(val projection: ConeKotlinTypeProjection, var supertypes: List<ConeKotlinType>? = null) :
+    TypeConstructorMarker {
+
 }
 
 class ConeCapturedType(
@@ -143,4 +144,18 @@ class ConeCapturedType(
 
     override val typeArguments: Array<out ConeKotlinTypeProjection>
         get() = emptyArray()
+}
+
+class ConeTypeVariableType(
+    override val nullability: ConeNullability,
+    override val lookupTag: ConeClassifierLookupTag
+) : ConeLookupTagBasedType() {
+    override val typeArguments: Array<out ConeKotlinTypeProjection> get() = emptyArray()
+}
+
+class ConeDefinitelyNotNullType(val original: ConeKotlinType): ConeKotlinType(), DefinitelyNotNullTypeMarker {
+    override val typeArguments: Array<out ConeKotlinTypeProjection>
+        get() = original.typeArguments
+    override val nullability: ConeNullability
+        get() = ConeNullability.NOT_NULL
 }

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

@@ -55,6 +55,7 @@ fun ConeKotlinType.toIrType(session: FirSession, declarationStorage: Fir2IrDecla
             upperBound.toIrType(session, declarationStorage)
         }
         is ConeCapturedType -> TODO()
+        is ConeDefinitelyNotNullType -> TODO()
     }
 }
 
@@ -102,7 +103,7 @@ fun FirReference.toSymbol(declarationStorage: Fir2IrDeclarationStorage): IrSymbo
 
 fun FirNamedReference.toSymbol(declarationStorage: Fir2IrDeclarationStorage): IrSymbol? {
     if (this is FirResolvedCallableReference) {
-        when (val callableSymbol = this.callableSymbol) {
+        when (val callableSymbol = this.coneSymbol) {
             is FirFunctionSymbol -> return callableSymbol.toFunctionSymbol(declarationStorage)
             is FirPropertySymbol -> return callableSymbol.toPropertySymbol(declarationStorage)
             is FirVariableSymbol -> return callableSymbol.toValueSymbol(declarationStorage)

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/CopyUtils.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
+import org.jetbrains.kotlin.fir.expressions.impl.FirFunctionCallImpl
+import org.jetbrains.kotlin.fir.types.FirTypeProjection
+import org.jetbrains.kotlin.fir.types.FirTypeRef
+
+fun FirFunctionCall.copy(
+    annotations: List<FirAnnotationCall> = this.annotations,
+    arguments: List<FirExpression> = this.arguments,
+    calleeReference: FirNamedReference = this.calleeReference,
+    explicitReceiver: FirExpression? = this.explicitReceiver,
+    psi: PsiElement? = this.psi,
+    safe: Boolean = this.safe,
+    session: FirSession = this.session,
+    typeArguments: List<FirTypeProjection> = this.typeArguments,
+    resultType: FirTypeRef = this.typeRef
+): FirFunctionCall {
+    return FirFunctionCallImpl(
+        session, psi, safe
+    ).apply {
+        this.annotations.addAll(annotations)
+        this.arguments.addAll(arguments)
+        this.calleeReference = calleeReference
+        this.explicitReceiver = explicitReceiver
+        this.typeArguments.addAll(typeArguments)
+        this.typeRef = resultType
+    }
+}
+

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ResolveUtils.kt

@@ -42,7 +42,7 @@ fun ConeClassifierLookupTag.toSymbol(useSiteSession: FirSession): ConeClassifier
     when (this) {
         is ConeClassLikeLookupTag -> toSymbol(useSiteSession)
         is ConeTypeParameterSymbol -> this
-        else -> error("sealed")
+        else -> error("sealed ${this::class}")
     }
 
 fun ConeClassLikeLookupTag.constructClassType(typeArguments: Array<ConeKotlinTypeProjection>, isNullable: Boolean): ConeLookupTagBasedType {
@@ -116,7 +116,8 @@ fun <T : ConeKotlinType> T.withNullability(nullability: ConeNullability): T {
         is ConeFunctionTypeImpl -> ConeFunctionTypeImpl(receiverType, parameterTypes, returnType, lookupTag, nullability.isNullable) as T
         is ConeTypeParameterTypeImpl -> ConeTypeParameterTypeImpl(lookupTag, nullability.isNullable) as T
         is ConeFlexibleType -> ConeFlexibleType(lowerBound.withNullability(nullability), upperBound.withNullability(nullability)) as T
-        else -> TODO("FIX KOTLIN COMPILER")
+        is ConeTypeVariableType -> ConeTypeVariableType(nullability, lookupTag) as T
+        else -> error("sealed: ${this::class}")
     }
 }
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import org.jetbrains.kotlin.fir.declarations.FirAnonymousFunction
+import org.jetbrains.kotlin.fir.declarations.FirValueParameter
+import org.jetbrains.kotlin.fir.expressions.FirCallableReferenceAccess
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
+import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
+import org.jetbrains.kotlin.fir.resolve.withNullability
+import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilder
+import org.jetbrains.kotlin.resolve.calls.inference.addSubtypeConstraintIfCompatible
+import org.jetbrains.kotlin.resolve.calls.inference.model.SimpleConstraintSystemConstraintPosition
+
+
+fun resolveArgumentExpression(
+    /*
+    csBuilder: ConstraintSystemBuilder,
+    argument: KotlinCallArgument,
+    expectedType: UnwrappedType?,
+    diagnosticsHolder: KotlinDiagnosticsHolder,
+    isReceiver: Boolean
+     */
+    csBuilder: ConstraintSystemBuilder,
+    argument: FirExpression,
+    expectedType: ConeKotlinType,
+    sink: CheckerSink,
+    isReceiver: Boolean,
+    typeProvider: (FirExpression) -> FirTypeRef?
+) {
+    return when (argument) {
+        is FirQualifiedAccessExpression, is FirFunctionCall -> checkPlainExpressionArgument(csBuilder, argument, expectedType, sink, isReceiver, typeProvider)
+        // TODO:!
+        is FirAnonymousFunction -> Unit
+        // TODO:!
+        is FirCallableReferenceAccess -> Unit
+        // TODO:!
+        //TODO: Collection literal
+        else -> checkPlainExpressionArgument(csBuilder, argument, expectedType, sink, isReceiver, typeProvider)
+    }
+}
+
+fun checkPlainExpressionArgument(
+    csBuilder: ConstraintSystemBuilder,
+    argument: FirExpression,
+    expectedType: ConeKotlinType?,
+    sink: CheckerSink,
+    isReceiver: Boolean,
+    typeProvider: (FirExpression) -> FirTypeRef?
+) {
+    if (expectedType == null) return
+    val argumentType = typeProvider(argument)?.coneTypeSafe<ConeKotlinType>() ?: return
+
+    val position = SimpleConstraintSystemConstraintPosition //TODO
+
+    if (!csBuilder.addSubtypeConstraintIfCompatible(argumentType, expectedType, position)) {
+        if (!isReceiver) {
+            csBuilder.addSubtypeConstraint(argumentType, expectedType, position)
+        }
+        val nullableExpectedType = expectedType.withNullability(ConeNullability.NULLABLE)
+        if (csBuilder.addSubtypeConstraintIfCompatible(argumentType, nullableExpectedType, position)) {
+            sink.reportApplicability(CandidateApplicability.WRONG_RECEIVER) // TODO
+        }
+
+    }
+}
+
+internal fun Candidate.resolveArgument(
+    argument: FirExpression,
+    parameter: FirValueParameter,
+    isReceiver: Boolean,
+    typeProvider: (FirExpression) -> FirTypeRef?,
+    sink: CheckerSink
+) {
+
+    val expectedType = prepareExpectedType(argument, parameter)
+    resolveArgumentExpression(this.system.getBuilder(), argument, expectedType, sink, isReceiver, typeProvider)
+}
+
+private fun Candidate.prepareExpectedType(argument: FirExpression, parameter: FirValueParameter): ConeKotlinType {
+    val expectedType = argument.getExpectedType(parameter/*, LanguageVersionSettings*/)
+    return this.substitutor.substituteOrSelf(expectedType)
+}
+
+internal fun FirExpression.getExpectedType(parameter: FirValueParameter/*, languageVersionSettings: LanguageVersionSettings*/) =
+//    if (this.isSpread || this.isArrayAssignedAsNamedArgumentInAnnotation(parameter, languageVersionSettings)) {
+//        parameter.type.unwrap()
+//    } else {
+    parameter.returnTypeRef.coneTypeUnsafe()//?.varargElementType?.unwrap() ?: parameter.type.unwrap()
+//    }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CallResolver.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.fir.renderWithType
 import org.jetbrains.kotlin.fir.resolve.FirSymbolProvider
 import org.jetbrains.kotlin.fir.resolve.defaultType
 import org.jetbrains.kotlin.fir.resolve.scope
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.transformers.ReturnTypeCalculator
 import org.jetbrains.kotlin.fir.scopes.FirPosition
 import org.jetbrains.kotlin.fir.scopes.FirScope
@@ -22,14 +23,22 @@ import org.jetbrains.kotlin.fir.symbols.*
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.calls.inference.model.ConstraintStorage
 import org.jetbrains.kotlin.resolve.calls.tasks.ExplicitReceiverKind
 import org.jetbrains.kotlin.utils.addToStdlib.cast
 
 
+
+
 class CallInfo(
-    val variableAccess: Boolean,
+    val callKind: CallKind,
+
     val explicitReceiver: FirExpression?,
-    val argumentCount: Int
+
+    val arguments: List<FirExpression>,
+    val typeArguments: List<FirTypeProjection>,
+
+    val typeProvider: (FirExpression) -> FirTypeRef?
 ) {
 
 }
@@ -50,11 +59,20 @@ class CheckerSinkImpl : CheckerSink {
 class Candidate(
     val symbol: ConeSymbol,
     val receiverKind: ExplicitReceiverKind,
-    val callKind: CallKind
-)
+    private val inferenceComponents: InferenceComponents,
+    private val baseSystem: ConstraintStorage
+) {
+    val system by lazy {
+        val system = inferenceComponents.createConstraintSystem()
+        system.addOtherSystem(baseSystem)
+        system
+    }
+    lateinit var substitutor: ConeSubstitutor
+}
 
 sealed class CallKind {
     abstract fun sequence(): List<ResolutionStage>
+
     object Function : CallKind() {
         override fun sequence(): List<ResolutionStage> {
             return functionCallResolutionSequence()
@@ -177,19 +195,31 @@ abstract class TowerDataConsumer {
 fun createVariableConsumer(
     session: FirSession,
     name: Name,
-    explicitReceiver: FirExpression?,
-    explicitReceiverType: FirTypeRef?
+    callInfo: CallInfo,
+    inferenceComponents: InferenceComponents
 ): TowerDataConsumer {
-    return createSimpleConsumer(session, name, TowerScopeLevel.Token.Properties, explicitReceiver, explicitReceiverType, CallKind.VariableAccess)
+    return createSimpleConsumer(
+        session,
+        name,
+        TowerScopeLevel.Token.Properties,
+        callInfo,
+        inferenceComponents
+    )
 }
 
 fun createFunctionConsumer(
     session: FirSession,
     name: Name,
-    explicitReceiver: FirExpression?,
-    explicitReceiverType: FirTypeRef?
+    callInfo: CallInfo,
+    inferenceComponents: InferenceComponents
 ): TowerDataConsumer {
-    return createSimpleConsumer(session, name, TowerScopeLevel.Token.Functions, explicitReceiver, explicitReceiverType, CallKind.Function)
+    return createSimpleConsumer(
+        session,
+        name,
+        TowerScopeLevel.Token.Functions,
+        callInfo,
+        inferenceComponents
+    )
 }
 
 
@@ -197,18 +227,24 @@ fun createSimpleConsumer(
     session: FirSession,
     name: Name,
     token: TowerScopeLevel.Token<*>,
-    explicitReceiver: FirExpression?,
-    explicitReceiverType: FirTypeRef?,
-    callKind: CallKind
+    callInfo: CallInfo,
+    inferenceComponents: InferenceComponents
 ): TowerDataConsumer {
-    return if (explicitReceiver != null) {
-        ExplicitReceiverTowerDataConsumer(session, name, token, object : ReceiverValueWithPossibleTypes {
-            override val type: ConeKotlinType
-                get() = explicitReceiverType?.coneTypeSafe()
-                    ?: ConeKotlinErrorType("No type calculated for: ${explicitReceiver.renderWithType()}") // TODO: assert here
-        }, callKind)
+    val factory = CandidateFactory(inferenceComponents, callInfo)
+    return if (callInfo.explicitReceiver != null) {
+        ExplicitReceiverTowerDataConsumer(
+            session,
+            name,
+            token,
+            object : ReceiverValueWithPossibleTypes {
+                override val type: ConeKotlinType
+                    get() = callInfo.typeProvider(callInfo.explicitReceiver)?.coneTypeSafe()
+                        ?: ConeKotlinErrorType("No type calculated for: ${callInfo.explicitReceiver.renderWithType()}") // TODO: assert here
+            },
+            factory
+        )
     } else {
-        NoExplicitReceiverTowerDataConsumer(session, name, token, callKind)
+        NoExplicitReceiverTowerDataConsumer(session, name, token, factory)
     }
 }
 
@@ -217,7 +253,7 @@ class ExplicitReceiverTowerDataConsumer<T : ConeSymbol>(
     val name: Name,
     val token: TowerScopeLevel.Token<T>,
     val explicitReceiver: ReceiverValueWithPossibleTypes,
-    val callKind: CallKind
+    val candidateFactory: CandidateFactory
 ) : TowerDataConsumer() {
 
     var groupId = 0
@@ -237,7 +273,14 @@ class ExplicitReceiverTowerDataConsumer<T : ConeSymbol>(
                     null,
                     object : TowerScopeLevel.TowerScopeLevelProcessor<T> {
                         override fun consumeCandidate(symbol: T, boundDispatchReceiver: ReceiverValueWithPossibleTypes?): ProcessorAction {
-                            resultCollector.consumeCandidate(groupId, Candidate(symbol, ExplicitReceiverKind.DISPATCH_RECEIVER, callKind))
+                            resultCollector.consumeCandidate(
+                                groupId,
+                                candidateFactory.createCandidate(
+                                    symbol,
+                                    boundDispatchReceiver,
+                                    ExplicitReceiverKind.DISPATCH_RECEIVER
+                                )
+                            )
                             return ProcessorAction.NEXT
                         }
                     }
@@ -249,7 +292,14 @@ class ExplicitReceiverTowerDataConsumer<T : ConeSymbol>(
                     explicitReceiver,
                     object : TowerScopeLevel.TowerScopeLevelProcessor<T> {
                         override fun consumeCandidate(symbol: T, boundDispatchReceiver: ReceiverValueWithPossibleTypes?): ProcessorAction {
-                            resultCollector.consumeCandidate(groupId, Candidate(symbol, ExplicitReceiverKind.EXTENSION_RECEIVER, callKind))
+                            resultCollector.consumeCandidate(
+                                groupId,
+                                candidateFactory.createCandidate(
+                                    symbol,
+                                    boundDispatchReceiver,
+                                    ExplicitReceiverKind.EXTENSION_RECEIVER
+                                )
+                            )
                             return ProcessorAction.NEXT
                         }
                     }
@@ -263,7 +313,7 @@ class NoExplicitReceiverTowerDataConsumer<T : ConeSymbol>(
     val session: FirSession,
     val name: Name,
     val token: TowerScopeLevel.Token<T>,
-    val callKind: CallKind
+    val candidateFactory: CandidateFactory
 ) : TowerDataConsumer() {
     var groupId = 0
 
@@ -284,7 +334,10 @@ class NoExplicitReceiverTowerDataConsumer<T : ConeSymbol>(
                     null,
                     object : TowerScopeLevel.TowerScopeLevelProcessor<T> {
                         override fun consumeCandidate(symbol: T, boundDispatchReceiver: ReceiverValueWithPossibleTypes?): ProcessorAction {
-                            resultCollector.consumeCandidate(groupId, Candidate(symbol, ExplicitReceiverKind.NO_EXPLICIT_RECEIVER, callKind))
+                            resultCollector.consumeCandidate(
+                                groupId,
+                                candidateFactory.createCandidate(symbol, boundDispatchReceiver, ExplicitReceiverKind.NO_EXPLICIT_RECEIVER)
+                            )
                             return ProcessorAction.NEXT
                         }
                     }
@@ -350,7 +403,7 @@ class CandidateCollector(val callInfo: CallInfo) {
         val sink = CheckerSinkImpl()
 
 
-        candidate.callKind.sequence().forEach {
+        callInfo.callKind.sequence().forEach {
             it.check(candidate, sink, callInfo)
         }
 
@@ -374,9 +427,9 @@ class CandidateCollector(val callInfo: CallInfo) {
     }
 
 
-    fun successCandidates(): List<ConeSymbol> {
+    fun bestCandidates(): List<Candidate> {
         if (groupNumbers.isEmpty()) return emptyList()
-        val result = mutableListOf<ConeSymbol>()
+        val result = mutableListOf<Candidate>()
         var bestGroup = groupNumbers.first()
         for ((index, candidate) in candidates.withIndex()) {
             val group = groupNumbers[index]
@@ -385,7 +438,7 @@ class CandidateCollector(val callInfo: CallInfo) {
                 result.clear()
             }
             if (bestGroup == group) {
-                result.add(candidate.symbol)
+                result.add(candidate)
             }
         }
         return result

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CandidateFactory.kt

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
+import org.jetbrains.kotlin.fir.symbols.ConeSymbol
+import org.jetbrains.kotlin.resolve.calls.components.PostponedArgumentsAnalyzer
+import org.jetbrains.kotlin.resolve.calls.inference.model.ConstraintStorage
+import org.jetbrains.kotlin.resolve.calls.tasks.ExplicitReceiverKind
+
+class CandidateFactory(
+    val inferenceComponents: InferenceComponents,
+    callInfo: CallInfo
+) {
+
+    val baseSystem: ConstraintStorage
+
+    init {
+        val system = inferenceComponents.createConstraintSystem()
+        callInfo.arguments.forEach {
+            system.addSubsystemFromExpression(it)
+        }
+        baseSystem = system.asReadOnlyStorage()
+    }
+
+    fun createCandidate(
+        symbol: ConeSymbol,
+        boundDispatchReceiver: ReceiverValueWithPossibleTypes?,
+        explicitReceiverKind: ExplicitReceiverKind
+    ): Candidate {
+        return Candidate(symbol, explicitReceiverKind, inferenceComponents, baseSystem)
+    }
+}
+
+private fun PostponedArgumentsAnalyzer.Context.addSubsystemFromExpression(expression: FirExpression) {
+    when (expression) {
+        is FirFunctionCall -> expression.candidate()?.let { addOtherSystem(it.system.asReadOnlyStorage()) }
+    }
+}
+
+internal fun FirFunctionCall.candidate(): Candidate? {
+    val callee = this.calleeReference
+    return when (callee) {
+        is FirNamedReferenceWithCandidate -> return callee.candidate
+        else -> null
+    }
+}

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

@@ -0,0 +1,308 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import org.jetbrains.kotlin.fir.resolve.FirSymbolProvider
+import org.jetbrains.kotlin.fir.resolve.constructType
+import org.jetbrains.kotlin.fir.resolve.substitution.AbstractConeSubstitutor
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
+import org.jetbrains.kotlin.fir.resolve.withArguments
+import org.jetbrains.kotlin.fir.resolve.withNullability
+import org.jetbrains.kotlin.fir.service
+import org.jetbrains.kotlin.fir.symbols.ConeClassLikeSymbol
+import org.jetbrains.kotlin.fir.symbols.ConeClassifierSymbol
+import org.jetbrains.kotlin.fir.symbols.StandardClassIds
+import org.jetbrains.kotlin.fir.symbols.invoke
+import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.fir.types.impl.ConeClassTypeImpl
+import org.jetbrains.kotlin.types.AbstractTypeChecker
+import org.jetbrains.kotlin.types.AbstractTypeCheckerContext
+import org.jetbrains.kotlin.types.model.*
+import org.jetbrains.kotlin.utils.addToStdlib.cast
+
+interface ConeInferenceContext : TypeSystemInferenceExtensionContext,
+    ConeTypeContext {
+
+    val symbolProvider: FirSymbolProvider get() = session.service()
+
+    override fun nullableNothingType(): SimpleTypeMarker {
+        return StandardClassIds.Nothing(symbolProvider).constructType(emptyArray(), true)
+    }
+
+    override fun nullableAnyType(): SimpleTypeMarker {
+        return StandardClassIds.Any(symbolProvider).constructType(emptyArray(), true)
+    }
+
+    override fun nothingType(): SimpleTypeMarker {
+        return StandardClassIds.Nothing(symbolProvider).constructType(emptyArray(), false)
+    }
+
+    override fun createFlexibleType(lowerBound: SimpleTypeMarker, upperBound: SimpleTypeMarker): KotlinTypeMarker {
+        require(lowerBound is ConeLookupTagBasedType)
+        require(upperBound is ConeLookupTagBasedType)
+
+        return ConeFlexibleType(lowerBound, upperBound)
+    }
+
+    override fun createSimpleType(
+        constructor: TypeConstructorMarker,
+        arguments: List<TypeArgumentMarker>,
+        nullable: Boolean
+    ): SimpleTypeMarker {
+        require(constructor is ConeClassifierSymbol)
+        when (constructor) {
+            is ConeClassLikeSymbol -> return ConeClassTypeImpl(
+                constructor.toLookupTag(),
+                arguments.cast(),
+                nullable
+            )
+            else -> error("!")
+        }
+
+    }
+
+    override fun createTypeArgument(type: KotlinTypeMarker, variance: TypeVariance): TypeArgumentMarker {
+        require(type is ConeKotlinType)
+        return when (variance) {
+            TypeVariance.INV -> type
+            TypeVariance.IN -> ConeKotlinTypeProjectionIn(type)
+            TypeVariance.OUT -> ConeKotlinTypeProjectionOut(type)
+        }
+    }
+
+    override fun createStarProjection(typeParameter: TypeParameterMarker): TypeArgumentMarker {
+        return ConeStarProjection
+    }
+
+    override fun newBaseTypeCheckerContext(errorTypesEqualToAnything: Boolean): AbstractTypeCheckerContext {
+        return ConeTypeCheckerContext(errorTypesEqualToAnything, session)
+    }
+
+    override fun KotlinTypeMarker.canHaveUndefinedNullability(): Boolean {
+        require(this is ConeKotlinType)
+        return this is ConeCapturedType /*|| this is ConeTypeVariable // TODO */
+                || this is ConeTypeParameterType
+    }
+
+    fun ConeKotlinType.typeDepthSimple(): Int {
+        // if (this is TypeUtils.SpecialType) return 0 // TODO: WTF?
+
+        val maxInArguments = this.typeArguments.asSequence().map {
+            if (it.isStarProjection()) 1 else it.getType().typeDepth()
+        }.max() ?: 0
+
+        return maxInArguments + 1
+    }
+
+    override fun SimpleTypeMarker.typeDepth(): Int {
+        require(this is ConeKotlinType)
+        return this.typeDepthSimple()
+    }
+
+    override fun KotlinTypeMarker.typeDepth(): Int {
+        require(this is ConeKotlinType)
+        return when (this) {
+            is ConeFlexibleType -> Math.max(lowerBound.typeDepthSimple(), upperBound.typeDepthSimple())
+            else -> typeDepthSimple()
+        }
+    }
+
+    override fun KotlinTypeMarker.contains(predicate: (KotlinTypeMarker) -> Boolean): Boolean {
+        return this.containsInternal(predicate)
+    }
+
+    private fun KotlinTypeMarker?.containsInternal(
+        predicate: (KotlinTypeMarker) -> Boolean,
+        visited: HashSet<KotlinTypeMarker> = hashSetOf()
+    ): Boolean {
+        if (this == null) return false
+        if (this in visited) return false
+        visited += this
+
+        /*
+        TODO:?
+        UnwrappedType unwrappedType = type.unwrap();
+         */
+
+        if (predicate(this)) return true
+
+        val flexibleType = this.asFlexibleType()
+        if (flexibleType != null
+            && (flexibleType.lowerBound().containsInternal(predicate, visited)
+                    || flexibleType.upperBound().containsInternal(predicate, visited))
+        ) {
+            return true
+        }
+
+
+        if (this is DefinitelyNotNullTypeMarker
+            && this.original().containsInternal(predicate, visited)
+        ) {
+            return true
+        }
+        /*
+        TODO:
+
+        TypeConstructor typeConstructor = type.getConstructor();
+        if (typeConstructor instanceof IntersectionTypeConstructor) {
+            IntersectionTypeConstructor intersectionTypeConstructor = (IntersectionTypeConstructor) typeConstructor;
+            for (KotlinType supertype : intersectionTypeConstructor.getSupertypes()) {
+                if (contains(supertype, isSpecialType, visited)) return true;
+            }
+            return false;
+        }
+         */
+
+        val simpleType = this.asSimpleType() ?: return false
+        repeat(simpleType.argumentsCount()) { index ->
+            val argument = simpleType.getArgument(index)
+            if (!argument.isStarProjection() && argument.getType().containsInternal(predicate, visited)) return true
+        }
+
+        return false
+    }
+
+    override fun TypeConstructorMarker.isUnitTypeConstructor(): Boolean {
+        return this is ConeClassLikeSymbol && this.classId == StandardClassIds.Unit
+    }
+
+    override fun Collection<KotlinTypeMarker>.singleBestRepresentative(): KotlinTypeMarker? {
+        if (this.size == 1) return this.first()
+
+        val context = newBaseTypeCheckerContext(true)
+        return this.firstOrNull { candidate ->
+            this.all { other ->
+                // We consider error types equal to anything here, so that intersections like
+                // {Array<String>, Array<[ERROR]>} work correctly
+                candidate == other || AbstractTypeChecker.equalTypes(context, candidate, other)
+            }
+        }
+    }
+
+    override fun KotlinTypeMarker.isUnit(): Boolean {
+        require(this is ConeKotlinType)
+        return this.typeConstructor().isUnitTypeConstructor() && !this.isNullable
+    }
+
+    override fun KotlinTypeMarker.withNullability(nullable: Boolean): KotlinTypeMarker {
+        require(this is ConeKotlinType)
+        return this.withNullability(ConeNullability.create(nullable))
+    }
+
+    override fun KotlinTypeMarker.makeDefinitelyNotNullOrNotNull(): KotlinTypeMarker {
+        return this.withNullability(false) //TODO("not implemented")
+    }
+
+    override fun SimpleTypeMarker.makeSimpleTypeDefinitelyNotNullOrNotNull(): SimpleTypeMarker {
+        return this.withNullability(false) //TODO("not implemented")
+    }
+
+    override fun createCapturedType(
+        constructorProjection: TypeArgumentMarker,
+        constructorSupertypes: List<KotlinTypeMarker>,
+        lowerType: KotlinTypeMarker?,
+        captureStatus: CaptureStatus
+    ): CapturedTypeMarker {
+        require(lowerType is ConeKotlinType?)
+        require(constructorProjection is ConeKotlinTypeProjection)
+        return ConeCapturedType(
+            captureStatus,
+            lowerType,
+            constructor = ConeCapturedTypeConstructor(constructorProjection, constructorSupertypes.cast())
+        )
+    }
+
+    override fun createStubType(typeVariable: TypeVariableMarker): StubTypeMarker {
+        TODO("not implemented")
+    }
+
+    override fun KotlinTypeMarker.removeAnnotations(): KotlinTypeMarker {
+        return this // TODO
+    }
+
+    override fun SimpleTypeMarker.replaceArguments(newArguments: List<TypeArgumentMarker>): SimpleTypeMarker {
+        require(this is ConeKotlinType)
+        return this.withArguments(newArguments.cast<List<ConeKotlinTypeProjection>>().toTypedArray())
+    }
+
+    override fun KotlinTypeMarker.hasExactAnnotation(): Boolean {
+        return false // TODO
+    }
+
+    override fun KotlinTypeMarker.hasNoInferAnnotation(): Boolean {
+        return false // TODO
+    }
+
+    override fun TypeVariableMarker.freshTypeConstructor(): TypeConstructorMarker {
+        require(this is ConeTypeVariable)
+        return this.typeConstructor
+    }
+
+    override fun CapturedTypeMarker.typeConstructorProjection(): TypeArgumentMarker {
+        require(this is ConeCapturedType)
+        return this.constructor.projection
+    }
+
+    override fun KotlinTypeMarker.isNullableType(): Boolean {
+        require(this is ConeKotlinType)
+        if (this.isMarkedNullable)
+            return true
+
+        if (this is ConeFlexibleType && this.upperBound.isNullableType())
+            return true
+
+        if (this is ConeTypeParameterType /* || is TypeVariable */)
+            return hasNullableSuperType(type)
+
+        // TODO: Intersection types
+        return false
+    }
+
+    override fun DefinitelyNotNullTypeMarker.original(): SimpleTypeMarker {
+        require(this is ConeDefinitelyNotNullType)
+        return this.original()
+    }
+
+    override fun typeSubstitutorByTypeConstructor(map: Map<TypeConstructorMarker, KotlinTypeMarker>): TypeSubstitutorMarker {
+        return object : AbstractConeSubstitutor(),
+            TypeSubstitutorMarker {
+            override fun substituteType(type: ConeKotlinType): ConeKotlinType? {
+                val new = map[type.typeConstructor()] ?: return null
+                return new as ConeKotlinType
+            }
+        }
+    }
+
+    override fun TypeSubstitutorMarker.safeSubstitute(type: KotlinTypeMarker): KotlinTypeMarker {
+        if (this === NoSubstitutor) return type
+        require(this is ConeSubstitutor)
+        require(type is ConeKotlinType)
+        return this.substituteOrSelf(type)
+    }
+
+    override fun TypeVariableMarker.defaultType(): SimpleTypeMarker {
+        require(this is ConeTypeVariable)
+        return this.defaultType
+    }
+
+    override fun captureFromExpression(type: KotlinTypeMarker): KotlinTypeMarker? {
+        return type
+    }
+
+
+    override fun createErrorTypeWithCustomConstructor(debugName: String, constructor: TypeConstructorMarker): KotlinTypeMarker {
+        return ConeKotlinErrorType("$debugName c: $constructor")
+    }
+
+    override fun CapturedTypeMarker.captureStatus(): CaptureStatus {
+        require(this is ConeCapturedType)
+        return this.captureStatus
+    }
+
+    override fun TypeConstructorMarker.isCapturedTypeConstructor(): Boolean {
+        return this is ConeCapturedTypeConstructor
+    }
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CreateFreshTypeVariableSubstitutorStage.kt

@@ -0,0 +1,133 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import org.jetbrains.kotlin.fir.declarations.FirCallableDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirCallableMemberDeclaration
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutorByMap
+import org.jetbrains.kotlin.fir.resolve.transformers.firUnsafe
+import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.fir.types.impl.FirTypePlaceholderProjection
+import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemOperation
+import org.jetbrains.kotlin.resolve.calls.inference.model.SimpleConstraintSystemConstraintPosition
+
+
+internal object CreateFreshTypeVariableSubstitutorStage : ResolutionStage() {
+    override fun check(candidate: Candidate, sink: CheckerSink, callInfo: CallInfo) {
+        val csBuilder = candidate.system.getBuilder()
+        val declaration = candidate.symbol.firUnsafe<FirCallableDeclaration>()
+        if (declaration !is FirCallableMemberDeclaration || declaration.typeParameters.isEmpty()) {
+            candidate.substitutor = ConeSubstitutor.Empty
+            return
+        }
+        val (substitutor, freshVariables) = createToFreshVariableSubstitutorAndAddInitialConstraints(declaration, candidate, csBuilder)
+        candidate.substitutor = substitutor
+
+
+        // bad function -- error on declaration side
+        if (csBuilder.hasContradiction) {
+            sink.reportApplicability(CandidateApplicability.INAPPLICABLE) //TODO: auto report it
+            return
+        }
+
+        // optimization
+//        if (resolvedCall.typeArgumentMappingByOriginal == NoExplicitArguments && knownTypeParametersResultingSubstitutor == null) {
+//            return
+//        }
+
+        val typeParameters = declaration.typeParameters
+        for (index in typeParameters.indices) {
+            val typeParameter = typeParameters[index]
+            val freshVariable = freshVariables[index]
+
+//            val knownTypeArgument = knownTypeParametersResultingSubstitutor?.substitute(typeParameter.defaultType)
+//            if (knownTypeArgument != null) {
+//                csBuilder.addEqualityConstraint(
+//                    freshVariable.defaultType,
+//                    knownTypeArgument.unwrap(),
+//                    KnownTypeParameterConstraintPosition(knownTypeArgument)
+//                )
+//                continue
+//            }
+
+
+            val typeArgument =
+                callInfo.typeArguments.getOrElse(index) { FirTypePlaceholderProjection }//resolvedCall.typeArgumentMappingByOriginal.getTypeArgument(typeParameter)
+//
+            if (typeArgument is FirTypeProjectionWithVariance) {
+                csBuilder.addEqualityConstraint(
+                    freshVariable.defaultType,
+                    typeArgument.typeRef.coneTypeUnsafe(),
+                    SimpleConstraintSystemConstraintPosition // TODO
+                )
+            } else {
+                assert(typeArgument == FirTypePlaceholderProjection) // TODO
+//                assert(typeArgument == TypeArgumentPlaceholder) {
+//                    "Unexpected typeArgument: $typeArgument, ${typeArgument.javaClass.canonicalName}"
+//                }
+            }
+        }
+    }
+
+}
+
+fun createToFreshVariableSubstitutorAndAddInitialConstraints(
+    declaration: FirCallableMemberDeclaration,
+    candidate: Candidate,
+    csBuilder: ConstraintSystemOperation
+): Pair<ConeSubstitutor, List<ConeTypeVariable>> {
+
+    val typeParameters = declaration.typeParameters
+
+    val freshTypeVariables = typeParameters.map { TypeParameterBasedTypeVariable(it.symbol) }
+
+    val toFreshVariables = ConeSubstitutorByMap(freshTypeVariables.associate { it.typeParameterSymbol to it.defaultType })
+
+    for (freshVariable in freshTypeVariables) {
+        csBuilder.registerVariable(freshVariable)
+    }
+
+    fun TypeParameterBasedTypeVariable.addSubtypeConstraint(
+        upperBound: ConeKotlinType//,
+        //position: DeclaredUpperBoundConstraintPosition
+    ) {
+        csBuilder.addSubtypeConstraint(defaultType, toFreshVariables.substituteOrSelf(upperBound), SimpleConstraintSystemConstraintPosition)
+    }
+
+    for (index in typeParameters.indices) {
+        val typeParameter = typeParameters[index]
+        val freshVariable = freshTypeVariables[index]
+        //val position = DeclaredUpperBoundConstraintPosition(typeParameter)
+
+        for (upperBound in typeParameter.bounds) {
+            freshVariable.addSubtypeConstraint(upperBound.coneTypeUnsafe()/*, position*/)
+        }
+    }
+
+//    if (candidateDescriptor is TypeAliasConstructorDescriptor) {
+//        val typeAliasDescriptor = candidateDescriptor.typeAliasDescriptor
+//        val originalTypes = typeAliasDescriptor.underlyingType.arguments.map { it.type }
+//        val originalTypeParameters = candidateDescriptor.underlyingConstructorDescriptor.typeParameters
+//        for (index in typeParameters.indices) {
+//            val typeParameter = typeParameters[index]
+//            val freshVariable = freshTypeVariables[index]
+//            val typeMapping = originalTypes.mapIndexedNotNull { i: Int, kotlinType: KotlinType ->
+//                if (kotlinType == typeParameter.defaultType) i else null
+//            }
+//            for (originalIndex in typeMapping) {
+//                // there can be null in case we already captured type parameter in outer class (in case of inner classes)
+//                // see test innerClassTypeAliasConstructor.kt
+//                val originalTypeParameter = originalTypeParameters.getOrNull(originalIndex) ?: continue
+//                val position = DeclaredUpperBoundConstraintPosition(originalTypeParameter)
+//                for (upperBound in originalTypeParameter.upperBounds) {
+//                    freshVariable.addSubtypeConstraint(upperBound, position)
+//                }
+//            }
+//        }
+//    }
+    return toFreshVariables to freshTypeVariables
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/FirNamedReferenceWithCandidate.kt

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.fir.*
+import org.jetbrains.kotlin.fir.references.FirResolvedCallableReferenceImpl
+import org.jetbrains.kotlin.fir.symbols.ConeCallableSymbol
+import org.jetbrains.kotlin.name.Name
+
+class FirNamedReferenceWithCandidate(session: FirSession, psi: PsiElement?, name: Name, val candidate: Candidate) :
+    FirResolvedCallableReferenceImpl(session, psi, name, candidate.symbol as ConeCallableSymbol)

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/InferenceCompletion.kt

@@ -0,0 +1,134 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import org.jetbrains.kotlin.fir.types.ConeKotlinType
+import org.jetbrains.kotlin.fir.types.FirTypeRef
+import org.jetbrains.kotlin.resolve.calls.inference.components.KotlinConstraintSystemCompleter
+import org.jetbrains.kotlin.resolve.calls.inference.components.TypeVariableDirectionCalculator
+import org.jetbrains.kotlin.resolve.calls.inference.components.VariableFixationFinder
+import org.jetbrains.kotlin.resolve.calls.inference.model.VariableWithConstraints
+import org.jetbrains.kotlin.resolve.calls.model.PostponedResolvedAtom
+import org.jetbrains.kotlin.types.model.KotlinTypeMarker
+import org.jetbrains.kotlin.types.model.isIntegerLiteralTypeConstructor
+import org.jetbrains.kotlin.types.model.typeConstructor
+
+
+fun Candidate.computeCompletionMode(
+    components: InferenceComponents,
+    expectedType: FirTypeRef?,
+    currentReturnType: ConeKotlinType?
+): KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode {
+    // Presence of expected type means that we trying to complete outermost call => completion mode should be full
+    if (expectedType != null) return KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.FULL
+
+    // This is questionable as null return type can be only for error call
+    if (currentReturnType == null) return KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.PARTIAL
+
+    return when {
+        // Consider call foo(bar(x)), if return type of bar is a proper one, then we can complete resolve for bar => full completion mode
+        // Otherwise, we shouldn't complete bar until we process call foo
+        system.getBuilder().isProperType(currentReturnType) -> KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.FULL
+
+        // Nested call is connected with the outer one through the UPPER constraint (returnType <: expectedOuterType)
+        // This means that there will be no new LOWER constraints =>
+        //   it's possible to complete call now if there are proper LOWER constraints
+        system.getBuilder().isTypeVariable(currentReturnType) ->
+            if (hasProperNonTrivialLowerConstraints(components, currentReturnType))
+                KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.FULL
+            else
+                KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.PARTIAL
+
+        else -> KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.PARTIAL
+    }
+}
+
+val Candidate.csBuilder get() = system.getBuilder()
+
+private fun Candidate.hasProperNonTrivialLowerConstraints(components: InferenceComponents, typeVariable: ConeKotlinType): Boolean {
+    assert(csBuilder.isTypeVariable(typeVariable)) { "$typeVariable is not a type variable" }
+
+    val context = components.ctx
+    val constructor = typeVariable.typeConstructor(context)
+    val variableWithConstraints = csBuilder.currentStorage().notFixedTypeVariables[constructor] ?: return false
+    val constraints = variableWithConstraints.constraints
+    return constraints.isNotEmpty() && constraints.all {
+        !it.type.typeConstructor(context).isIntegerLiteralTypeConstructor(context) &&
+                it.kind.isLower() && csBuilder.isProperType(it.type)
+    }
+
+}
+
+
+class ConstraintSystemCompleter(val components: InferenceComponents) {
+    val variableFixationFinder = VariableFixationFinder(components.trivialConstraintTypeInferenceOracle)
+    fun complete(
+        c: KotlinConstraintSystemCompleter.Context,
+        completionMode: KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode,
+        candidateReturnType: ConeKotlinType
+    ) {
+
+        while (true) {
+//            if (analyzePostponeArgumentIfPossible(c, topLevelAtoms, analyze)) continue
+
+
+//            val allTypeVariables = getOrderedAllTypeVariables(c, collectVariablesFromContext, topLevelAtoms)
+            val allTypeVariables = c.notFixedTypeVariables.keys.toList()
+//            val postponedKtPrimitives = getOrderedNotAnalyzedPostponedArguments(topLevelAtoms)
+            val variableForFixation =
+                variableFixationFinder.findFirstVariableForFixation(
+                    c, allTypeVariables, emptyList(), completionMode, candidateReturnType
+                ) ?: break
+
+//            if (shouldForceCallableReferenceOrLambdaResolution(completionMode, variableForFixation)) {
+//                if (forcePostponedAtomResolution<ResolvedCallableReferenceAtom>(topLevelAtoms, analyze)) continue
+//                if (forcePostponedAtomResolution<LambdaWithTypeVariableAsExpectedTypeAtom>(topLevelAtoms, analyze)) continue
+//            }
+
+            if (variableForFixation.hasProperConstraint || completionMode == KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.FULL) {
+                val variableWithConstraints = c.notFixedTypeVariables.getValue(variableForFixation.variable)
+
+                fixVariable(c, candidateReturnType, variableWithConstraints, emptyList())
+
+//                if (!variableForFixation.hasProperConstraint) {
+//                    c.addError(NotEnoughInformationForTypeParameter(variableWithConstraints.typeVariable))
+//                }
+                continue
+            }
+
+            break
+        }
+
+        if (completionMode == KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.FULL) {
+            // force resolution for all not-analyzed argument's
+//            getOrderedNotAnalyzedPostponedArguments(topLevelAtoms).forEach(analyze)
+//
+//            if (c.notFixedTypeVariables.isNotEmpty() && c.postponedTypeVariables.isEmpty()) {
+//                runCompletion(c, completionMode, topLevelAtoms, topLevelType, analyze)
+//            }
+        }
+    }
+
+    private fun fixVariable(
+        c: KotlinConstraintSystemCompleter.Context,
+        topLevelType: KotlinTypeMarker,
+        variableWithConstraints: VariableWithConstraints,
+        postponedResolveKtPrimitives: List<PostponedResolvedAtom>
+    ) {
+        val direction = TypeVariableDirectionCalculator(c, postponedResolveKtPrimitives, topLevelType).getDirection(variableWithConstraints)
+        fixVariable(c, variableWithConstraints, direction)
+    }
+
+    fun fixVariable(
+        c: KotlinConstraintSystemCompleter.Context,
+        variableWithConstraints: VariableWithConstraints,
+        direction: TypeVariableDirectionCalculator.ResolveDirection
+    ) {
+        val resultType = components.resultTypeResolver.findResultType(c, variableWithConstraints, direction)
+        c.fixVariable(variableWithConstraints.typeVariable, resultType)
+    }
+
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/InferenceUtil.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import org.jetbrains.kotlin.fir.resolve.*
+import org.jetbrains.kotlin.fir.symbols.*
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
+import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.calls.inference.components.*
+import org.jetbrains.kotlin.resolve.calls.inference.model.NewConstraintSystemImpl
+import org.jetbrains.kotlin.types.AbstractTypeApproximator
+import org.jetbrains.kotlin.types.model.*
+
+
+fun ConeInferenceContext.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 ConeTypeVariableTypeConstructor(val debugName: String) : ConeSymbol, ConeClassifierLookupTag, TypeVariableTypeConstructorMarker {
+    override val name: Name get() = Name.identifier(debugName)
+}
+
+class TypeParameterBasedTypeVariable(val typeParameterSymbol: FirTypeParameterSymbol) :
+    ConeTypeVariable(typeParameterSymbol.name.identifier)
+
+open class ConeTypeVariable(name: String) : TypeVariableMarker {
+    val typeConstructor = ConeTypeVariableTypeConstructor(name)
+    val defaultType = ConeTypeVariableType(ConeNullability.NOT_NULL, typeConstructor)
+}
+
+class InferenceComponents(val ctx: TypeSystemInferenceExtensionContextDelegate) {
+    private val approximator = object : AbstractTypeApproximator(ctx) {}
+    val trivialConstraintTypeInferenceOracle = TrivialConstraintTypeInferenceOracle(ctx)
+    private val incorporator = ConstraintIncorporator(approximator, trivialConstraintTypeInferenceOracle)
+    private val injector = ConstraintInjector(incorporator, approximator)
+    val resultTypeResolver = ResultTypeResolver(approximator, trivialConstraintTypeInferenceOracle)
+
+    fun createConstraintSystem(): NewConstraintSystemImpl {
+        return NewConstraintSystemImpl(injector, ctx)
+    }
+}
+

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/OverloadConflictResolver.kt

@@ -0,0 +1,215 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.calls
+
+import org.jetbrains.kotlin.fir.declarations.FirCallableDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirConstructor
+import org.jetbrains.kotlin.fir.declarations.FirNamedFunction
+import org.jetbrains.kotlin.fir.resolve.transformers.firUnsafe
+import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
+import org.jetbrains.kotlin.resolve.OverloadabilitySpecificityCallbacks
+import org.jetbrains.kotlin.resolve.calls.inference.model.NewConstraintSystemImpl
+import org.jetbrains.kotlin.resolve.calls.inference.model.SimpleConstraintSystemConstraintPosition
+import org.jetbrains.kotlin.resolve.calls.results.FlatSignature
+import org.jetbrains.kotlin.resolve.calls.results.SimpleConstraintSystem
+import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
+import org.jetbrains.kotlin.resolve.calls.results.isSignatureNotLessSpecific
+import org.jetbrains.kotlin.types.model.KotlinTypeMarker
+import org.jetbrains.kotlin.types.model.TypeParameterMarker
+import org.jetbrains.kotlin.types.model.TypeSubstitutorMarker
+import org.jetbrains.kotlin.types.model.TypeSystemInferenceExtensionContext
+
+class ConeOverloadConflictResolver(
+    val specificityComparator: TypeSpecificityComparator,
+    val inferenceComponents: InferenceComponents
+
+) {
+
+    fun chooseMaximallySpecificCandidates(
+        candidates: Collection<Candidate>,
+        //checkArgumentsMode: CheckArgumentTypesMode,
+        discriminateGenerics: Boolean//,
+        //isDebuggerContext: Boolean
+    ): Set<Candidate> {
+
+        val candidatesSet = candidates.toSet()
+
+        val maximallySpecific = findMaximallySpecificCall(candidatesSet, false/*, isDebuggerContext*/)
+        if (maximallySpecific != null) {
+            return setOf(maximallySpecific)
+        }
+
+        return candidatesSet
+
+    }
+
+    private fun createFlatSignature(call: Candidate): FlatSignature<Candidate> {
+        val declaration = call.symbol.firUnsafe<FirCallableDeclaration>()
+        return when (declaration) {
+            is FirNamedFunction -> createFlatSignature(call, declaration)
+            is FirConstructor -> createFlatSignature(call, declaration)
+            else -> error("Not supported: $declaration")
+        }
+    }
+
+    private fun createFlatSignature(call: Candidate, constructor: FirConstructor): FlatSignature<Candidate> {
+        return FlatSignature(
+            call,
+            constructor.typeParameters.map { it.symbol },
+            constructor.valueParameters.map { it.returnTypeRef.coneTypeUnsafe() },
+            //constructor.receiverTypeRef != null,
+            false,
+            constructor.valueParameters.any { it.isVararg },
+            constructor.valueParameters.count { it.defaultValue != null },
+            constructor.isExpect,
+            false // TODO
+        )
+    }
+
+    private fun createFlatSignature(call: Candidate, function: FirNamedFunction): FlatSignature<Candidate> {
+        return FlatSignature(
+            call,
+            function.typeParameters.map { it.symbol },
+            function.valueParameters.map { it.returnTypeRef.coneTypeUnsafe() },
+            function.receiverTypeRef != null,
+            function.valueParameters.any { it.isVararg },
+            function.valueParameters.count { it.defaultValue != null },
+            function.isExpect,
+            false // TODO
+        )
+    }
+
+    private fun createEmptyConstraintSystem(): SimpleConstraintSystem {
+        return ConeSimpleConstraintSystemImpl(inferenceComponents.createConstraintSystem())
+    }
+
+    private fun findMaximallySpecificCall(
+        candidates: Set<Candidate>,
+        discriminateGenerics: Boolean//,
+        //isDebuggerContext: Boolean
+    ): Candidate? {
+        val filteredCandidates = candidates//uniquifyCandidatesSet(candidates)
+
+        if (filteredCandidates.size <= 1) return filteredCandidates.singleOrNull()
+
+        val conflictingCandidates = filteredCandidates.map { candidateCall ->
+            createFlatSignature(candidateCall)
+        }
+
+        val bestCandidatesByParameterTypes = conflictingCandidates.filter { candidate ->
+            isMostSpecific(candidate, conflictingCandidates) { call1, call2 ->
+                isNotLessSpecificCallWithArgumentMapping(call1, call2, discriminateGenerics)
+            }
+        }
+
+        return bestCandidatesByParameterTypes.exactMaxWith { call1, call2 ->
+            isOfNotLessSpecificShape(call1, call2)// && isOfNotLessSpecificVisibilityForDebugger(call1, call2, isDebuggerContext)
+        }?.origin
+    }
+
+
+    private inline fun <C : Any> Collection<C>.exactMaxWith(isNotWorse: (C, C) -> Boolean): C? {
+        var result: C? = null
+        for (candidate in this) {
+            if (result == null || isNotWorse(candidate, result)) {
+                result = candidate
+            }
+        }
+        if (result == null) return null
+        if (any { it != result && isNotWorse(it, result!!) }) {
+            return null
+        }
+        return result
+    }
+
+    private inline fun <C> isMostSpecific(candidate: C, candidates: Collection<C>, isNotLessSpecific: (C, C) -> Boolean): Boolean =
+        candidates.all { other ->
+            candidate === other ||
+                    isNotLessSpecific(candidate, other)
+        }
+
+    /**
+     * `call1` is not less specific than `call2`
+     */
+    private fun isNotLessSpecificCallWithArgumentMapping(
+        call1: FlatSignature<Candidate>,
+        call2: FlatSignature<Candidate>,
+        discriminateGenerics: Boolean
+    ): Boolean {
+        return compareCallsByUsedArguments(
+            call1,
+            call2,
+            discriminateGenerics
+        )
+    }
+
+
+
+    /**
+     * Returns `true` if [call1] is definitely more or equally specific [call2],
+     * `false` otherwise.
+     */
+    private fun compareCallsByUsedArguments(
+        call1: FlatSignature<Candidate>,
+        call2: FlatSignature<Candidate>,
+        discriminateGenerics: Boolean
+    ): Boolean {
+        if (discriminateGenerics) {
+            val isGeneric1 = call1.isGeneric
+            val isGeneric2 = call2.isGeneric
+            // generic loses to non-generic
+            if (isGeneric1 && !isGeneric2) return false
+            if (!isGeneric1 && isGeneric2) return true
+            // two generics are non-comparable
+            if (isGeneric1 && isGeneric2) return false
+        }
+
+        if (!call1.isExpect && call2.isExpect) return true
+        if (call1.isExpect && !call2.isExpect) return false
+
+        return createEmptyConstraintSystem().isSignatureNotLessSpecific(
+            call1,
+            call2,
+            OverloadabilitySpecificityCallbacks,
+            specificityComparator
+        )
+    }
+
+    private fun isOfNotLessSpecificShape(
+        call1: FlatSignature<Candidate>,
+        call2: FlatSignature<Candidate>
+    ): Boolean {
+        val hasVarargs1 = call1.hasVarargs
+        val hasVarargs2 = call2.hasVarargs
+        if (hasVarargs1 && !hasVarargs2) return false
+        if (!hasVarargs1 && hasVarargs2) return true
+
+        if (call1.numDefaults > call2.numDefaults) {
+            return false
+        }
+
+        return true
+    }
+
+}
+
+object NoSubstitutor : TypeSubstitutorMarker
+
+class ConeSimpleConstraintSystemImpl(val system: NewConstraintSystemImpl) : SimpleConstraintSystem {
+    override fun registerTypeVariables(typeParameters: Collection<TypeParameterMarker>): TypeSubstitutorMarker {
+        return NoSubstitutor
+    }
+
+    override fun addSubtypeConstraint(subType: KotlinTypeMarker, superType: KotlinTypeMarker) {
+        system.addSubtypeConstraint(subType, superType, SimpleConstraintSystemConstraintPosition)
+    }
+
+    override fun hasContradiction(): Boolean = system.hasContradiction
+
+    override val context: TypeSystemInferenceExtensionContext
+        get() = system
+
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/ResolverParts.kt

@@ -10,26 +10,42 @@ import org.jetbrains.kotlin.fir.resolve.transformers.firUnsafe
 import org.jetbrains.kotlin.fir.symbols.impl.FirFunctionSymbol
 
 
-sealed class ResolutionStage {
+abstract class ResolutionStage {
     abstract fun check(candidate: Candidate, sink: CheckerSink, callInfo: CallInfo)
 }
 
-sealed class CheckerStage : ResolutionStage()
+abstract class CheckerStage : ResolutionStage()
 
 internal object MapArguments : ResolutionStage() {
     override fun check(candidate: Candidate, sink: CheckerSink, callInfo: CallInfo) {
         val symbol = candidate.symbol as? FirFunctionSymbol ?: return sink.reportApplicability(CandidateApplicability.HIDDEN)
-        if (symbol.firUnsafe<FirFunction>().valueParameters.size != callInfo.argumentCount) {
+        if (symbol.firUnsafe<FirFunction>().valueParameters.size != callInfo.arguments.size) {
             return sink.reportApplicability(CandidateApplicability.PARAMETER_MAPPING_ERROR)
         }
     }
 
 }
 
+internal object CheckArguments : CheckerStage() {
+    override fun check(candidate: Candidate, sink: CheckerSink, callInfo: CallInfo) {
+        val symbol = candidate.symbol as? FirFunctionSymbol ?: error("Can't check arguments for non function")
+        val declaration = symbol.fir as FirFunction
+        for ((parameter, argument) in declaration.valueParameters.zip(callInfo.arguments)) {
+
+            candidate.resolveArgument(argument, parameter, isReceiver = false, typeProvider = callInfo.typeProvider, sink = sink)
+        }
+
+        if (candidate.system.hasContradiction) {
+            sink.reportApplicability(CandidateApplicability.INAPPLICABLE)
+        }
+    }
+
+}
+
 
 internal fun functionCallResolutionSequence() =
-    listOf<ResolutionStage>(MapArguments)
+    listOf<ResolutionStage>(MapArguments, CreateFreshTypeVariableSubstitutorStage, CheckArguments)
 
 
 internal fun qualifiedAccessResolutionSequence() =
-    listOf<ResolutionStage>()
+    listOf<ResolutionStage>(CreateFreshTypeVariableSubstitutorStage)

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt

@@ -0,0 +1,130 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.substitution
+
+import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterSymbol
+import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.fir.types.impl.ConeAbbreviatedTypeImpl
+import org.jetbrains.kotlin.fir.types.impl.ConeClassTypeImpl
+
+
+interface ConeSubstitutor {
+    fun substituteOrSelf(type: ConeKotlinType): ConeKotlinType
+    fun substituteOrNull(type: ConeKotlinType): ConeKotlinType?
+
+    object Empty : ConeSubstitutor {
+        override fun substituteOrSelf(type: ConeKotlinType): ConeKotlinType {
+            return type
+        }
+
+        override fun substituteOrNull(type: ConeKotlinType): ConeKotlinType? {
+            return null
+        }
+
+    }
+}
+
+fun ConeSubstitutor.substituteOrNull(type: ConeKotlinType?): ConeKotlinType? {
+    return type?.let { substituteOrNull(it) }
+}
+
+abstract class AbstractConeSubstitutor : ConeSubstitutor {
+    private fun wrapProjection(old: ConeKotlinTypeProjection, newType: ConeKotlinType): ConeKotlinTypeProjection {
+        return when (old) {
+            is ConeStarProjection -> old
+            is ConeKotlinTypeProjectionIn -> ConeKotlinTypeProjectionIn(newType)
+            is ConeKotlinTypeProjectionOut -> ConeKotlinTypeProjectionOut(newType)
+            is ConeKotlinType -> newType
+            else -> old
+        }
+    }
+
+    abstract fun substituteType(type: ConeKotlinType): ConeKotlinType?
+
+    override fun substituteOrSelf(type: ConeKotlinType): ConeKotlinType {
+        return substituteOrNull(type) ?: type
+    }
+
+    override fun substituteOrNull(type: ConeKotlinType): ConeKotlinType? {
+        val newType = substituteType(type)
+        return (newType ?: type).substituteRecursive() ?: newType
+    }
+
+    private fun ConeKotlinType.substituteRecursive(): ConeKotlinType? {
+        return when (this) {
+            is ConeClassErrorType -> return null
+            is ConeClassType -> this.substituteArguments()
+            is ConeAbbreviatedType -> this.substituteArguments()
+            is ConeFunctionType -> TODO()
+            is ConeTypeParameterType -> return null
+            is ConeTypeVariableType -> return null
+            is ConeFlexibleType -> this.substituteBounds()
+            is ConeCapturedType -> TODO()
+            is ConeDefinitelyNotNullType -> this.substituteOriginal()
+        }
+    }
+
+    private fun ConeDefinitelyNotNullType.substituteOriginal(): ConeDefinitelyNotNullType? {
+        TODO()
+    }
+
+    private fun ConeFlexibleType.substituteBounds(): ConeFlexibleType? {
+        val newLowerBound = substituteOrNull(lowerBound) as ConeLookupTagBasedType?
+        val newUpperBound = substituteOrNull(upperBound) as ConeLookupTagBasedType?
+        if (newLowerBound != null || newUpperBound != null) {
+            return ConeFlexibleType(newLowerBound ?: lowerBound, newUpperBound ?: upperBound)
+        }
+        return null
+    }
+
+    private fun ConeKotlinType.substituteArguments(): ConeKotlinType? {
+        val newArguments by lazy { arrayOfNulls<ConeKotlinTypeProjection>(typeArguments.size) }
+        var initialized = false
+        for ((index, typeArgument) in this.typeArguments.withIndex()) {
+            val type = (typeArgument as? ConeTypedProjection)?.type ?: continue
+            val newType = substituteOrNull(type)
+            if (newType != null) {
+                initialized = true
+                newArguments[index] = wrapProjection(typeArgument, newType)
+            }
+        }
+
+        if (initialized) {
+            for ((index, typeArgument) in this.typeArguments.withIndex()) {
+                if (newArguments[index] == null) {
+                    newArguments[index] = typeArgument
+                }
+            }
+            @Suppress("UNCHECKED_CAST")
+            return when (this) {
+                is ConeClassTypeImpl -> ConeClassTypeImpl(
+                    lookupTag,
+                    newArguments as Array<ConeKotlinTypeProjection>,
+                    nullability.isNullable
+                )
+                is ConeAbbreviatedTypeImpl -> ConeAbbreviatedTypeImpl(
+                    abbreviationLookupTag,
+                    newArguments as Array<ConeKotlinTypeProjection>,
+                    nullability.isNullable
+                )
+                is ConeClassLikeType -> error("Unknown class-like type to substitute: $this, ${this::class}")
+                else -> error("Unknown type to substitute: $this, ${this::class}")
+            }
+        }
+        return null
+    }
+
+
+}
+
+
+class ConeSubstitutorByMap(val substitution: Map<ConeTypeParameterSymbol, ConeKotlinType>) : AbstractConeSubstitutor() {
+
+    override fun substituteType(type: ConeKotlinType): ConeKotlinType? {
+        if (type !is ConeTypeParameterType) return null
+        return substitution[type.lookupTag]
+    }
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirBodyResolveTransformer.kt

@@ -10,13 +10,10 @@ import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.references.FirErrorNamedReference
-import org.jetbrains.kotlin.fir.references.FirResolvedCallableReferenceImpl
 import org.jetbrains.kotlin.fir.references.FirSimpleNamedReference
 import org.jetbrains.kotlin.fir.resolve.*
-import org.jetbrains.kotlin.fir.resolve.calls.CallInfo
-import org.jetbrains.kotlin.fir.resolve.calls.CallResolver
-import org.jetbrains.kotlin.fir.resolve.calls.createFunctionConsumer
-import org.jetbrains.kotlin.fir.resolve.calls.createVariableConsumer
+import org.jetbrains.kotlin.fir.resolve.calls.*
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.scopes.FirScope
 import org.jetbrains.kotlin.fir.scopes.addImportingScopes
 import org.jetbrains.kotlin.fir.scopes.impl.FirLocalScope
@@ -24,16 +21,17 @@ import org.jetbrains.kotlin.fir.scopes.impl.FirTopLevelDeclaredMemberScope
 import org.jetbrains.kotlin.fir.scopes.impl.withReplacedConeType
 import org.jetbrains.kotlin.fir.symbols.*
 import org.jetbrains.kotlin.fir.types.*
-import org.jetbrains.kotlin.fir.types.impl.ConeClassTypeImpl
-import org.jetbrains.kotlin.fir.types.impl.FirComputingImplicitTypeRef
-import org.jetbrains.kotlin.fir.types.impl.FirErrorTypeRefImpl
-import org.jetbrains.kotlin.fir.types.impl.FirResolvedTypeRefImpl
+import org.jetbrains.kotlin.fir.types.impl.*
 import org.jetbrains.kotlin.fir.visitors.CompositeTransformResult
 import org.jetbrains.kotlin.fir.visitors.FirTransformer
 import org.jetbrains.kotlin.fir.visitors.compose
 import org.jetbrains.kotlin.ir.expressions.IrConstKind
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.calls.inference.buildAbstractResultingSubstitutor
+import org.jetbrains.kotlin.resolve.calls.inference.components.KotlinConstraintSystemCompleter
+import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
+import org.jetbrains.kotlin.types.model.*
 import org.jetbrains.kotlin.utils.addIfNotNull
 
 open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOnly: Boolean) : FirTransformer<Any?>() {
@@ -115,7 +113,7 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
                 resolved.resultType =
                     resolved.conversionTypeRef.withReplacedConeType(
                         session,
-                        resolved.conversionTypeRef.coneTypeUnsafe<ConeKotlinType>().withNullability(ConeNullability.NULLABLE)
+                        resolved.conversionTypeRef.coneTypeUnsafe().withNullability(ConeNullability.NULLABLE)
                     )
             }
             else -> error("Unknown type operator")
@@ -143,16 +141,36 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
     val jump = ReturnTypeCalculatorWithJump(session)
 
     private fun <T> storeTypeFromCallee(access: T) where T : FirQualifiedAccess, T : FirExpression {
-        access.resultType =
-            when (val newCallee = access.calleeReference) {
-                is FirErrorNamedReference ->
-                    FirErrorTypeRefImpl(session, access.psi, newCallee.errorReason)
-                is FirResolvedCallableReference ->
-                    jump.tryCalculateReturnType(newCallee.callableSymbol.firUnsafe())
-                else -> return
-            }
+        access.resultType = typeFromCallee(access)
     }
 
+    private fun <T> typeFromCallee(access: T): FirResolvedTypeRef where T : FirQualifiedAccess, T : FirExpression {
+        return when (val newCallee = access.calleeReference) {
+            is FirErrorNamedReference ->
+                FirErrorTypeRefImpl(session, access.psi, newCallee.errorReason)
+            is FirResolvedCallableReference ->
+                jump.tryCalculateReturnType(newCallee.callableSymbol.firUnsafe())
+            else -> error("Failed to extract type from: $newCallee")
+        }
+    }
+
+    val inferenceComponents = InferenceComponents(object : ConeInferenceContext, TypeSystemInferenceExtensionContextDelegate {
+        override fun findCommonIntegerLiteralTypesSuperType(explicitSupertypes: List<SimpleTypeMarker>): SimpleTypeMarker? {
+            TODO("not implemented")
+        }
+
+        override fun TypeConstructorMarker.getApproximatedIntegerLiteralType(): KotlinTypeMarker {
+            TODO("not implemented")
+        }
+
+        override val session: FirSession
+            get() = this@FirBodyResolveTransformer.session
+
+        override fun KotlinTypeMarker.removeExactAnnotation(): KotlinTypeMarker {
+            return this
+        }
+    })
+
     override fun transformQualifiedAccessExpression(
         qualifiedAccessExpression: FirQualifiedAccessExpression,
         data: Any?
@@ -180,13 +198,9 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
         }
         val callee = qualifiedAccessExpression.calleeReference as? FirSimpleNamedReference ?: return qualifiedAccessExpression.compose()
 
-        qualifiedAccessExpression.explicitReceiver?.visitNoTransform(this, null)
+        val receiver = qualifiedAccessExpression.explicitReceiver?.transformSingle(this, null)
 
-        val receiver = qualifiedAccessExpression.explicitReceiver
-
-        //val checkers = listOf(VariableApplicabilityChecker(callee.name))
-
-        val info = CallInfo(true, receiver, 0)
+        val info = CallInfo(CallKind.VariableAccess, receiver, emptyList(), emptyList()) { it.resultType }
         val resolver = CallResolver(jump, session)
         resolver.callInfo = info
         resolver.scopes = (scopes + localScopes).asReversed()
@@ -194,40 +208,44 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
         val consumer = createVariableConsumer(
             session,
             callee.name,
-            qualifiedAccessExpression.explicitReceiver,
-            qualifiedAccessExpression.explicitReceiver?.resultType
+            info, inferenceComponents
         )
         val result = resolver.runTowerResolver(consumer)
-        val successCandidates = result.successCandidates()
-        val resultExpression = qualifiedAccessExpression.transformCalleeReference(this, successCandidates)
+
+        val nameReference = createResolvedNamedReference(
+            callee,
+            result.bestCandidates(),
+            result.currentApplicability
+        )
+
+        val resultExpression =
+            qualifiedAccessExpression.transformCalleeReference(StoreNameReference, nameReference)
         storeTypeFromCallee(resultExpression as FirQualifiedAccessExpression)
         return resultExpression.compose()
     }
 
-    override fun transformFunctionCall(functionCall: FirFunctionCall, data: Any?): CompositeTransformResult<FirStatement> {
+    private fun resolveCallAndSelectCandidate(functionCall: FirFunctionCall, expectedTypeRef: FirTypeRef?): FirFunctionCall {
 
         val functionCall = functionCall.transformChildren(this, null) as FirFunctionCall
 
-        if (functionCall.calleeReference !is FirSimpleNamedReference) return functionCall.compose()
-
         val name = functionCall.calleeReference.name
 
-        val expectedTypeRef = data as FirTypeRef?
-
         val receiver = functionCall.explicitReceiver
         val arguments = functionCall.arguments
+        val typeArguments = functionCall.typeArguments
 
 
-        val info = CallInfo(false, receiver, arguments.size)
+        val info = CallInfo(CallKind.Function, receiver, arguments, typeArguments) { it.resultType }
         val resolver = CallResolver(jump, session)
         resolver.callInfo = info
         resolver.scopes = (scopes + localScopes).asReversed()
 
-
-
-        val consumer = createFunctionConsumer(session, name, receiver, receiver?.resultType)
+        val consumer = createFunctionConsumer(session, name, info, inferenceComponents)
         val result = resolver.runTowerResolver(consumer)
-        val successCandidates = result.successCandidates()
+        val bestCandidates = result.bestCandidates()
+        val reducedCandidates = ConeOverloadConflictResolver(TypeSpecificityComparator.NONE, inferenceComponents)
+            .chooseMaximallySpecificCandidates(bestCandidates, discriminateGenerics = false)
+
 
 //        fun isInvoke()
 //
@@ -257,33 +275,103 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
 //            }
 //            else -> functionCall
 //        }
-        val resultExpression = functionCall.transformCalleeReference(this, successCandidates)
+        val nameReference = createResolvedNamedReference(
+            functionCall.calleeReference,
+            reducedCandidates,
+            result.currentApplicability
+        )
 
-        storeTypeFromCallee(resultExpression as FirFunctionCall)
-        return resultExpression.compose()
+        val resultExpression = functionCall.transformCalleeReference(StoreNameReference, nameReference) as FirFunctionCall
+        val typeRef = typeFromCallee(functionCall)
+        if (typeRef.type is ConeKotlinErrorType) {
+            functionCall.resultType = typeRef
+        }
+        return resultExpression
     }
 
-    private fun createResolvedNamedReference(namedReference: FirNamedReference, candidates: List<ConeCallableSymbol>): FirNamedReference {
+    private fun completeTypeInference(functionCall: FirFunctionCall, expectedTypeRef: FirTypeRef?): FirFunctionCall {
+        val typeRef = typeFromCallee(functionCall)
+        if (typeRef.type is ConeKotlinErrorType) {
+            functionCall.resultType = typeRef
+            return functionCall
+        }
+        val candidate = functionCall.candidate() ?: return functionCall
+        val initialSubstitutor = candidate.substitutor
+
+        val initialType = initialSubstitutor.substituteOrSelf(typeRef.type)
+
+        val completionMode = candidate.computeCompletionMode(inferenceComponents, expectedTypeRef, initialType)
+        val completer = ConstraintSystemCompleter(inferenceComponents)
+        completer.complete(candidate.system.asConstraintSystemCompleterContext(), completionMode, initialType)
+
+
+        if (completionMode == KotlinConstraintSystemCompleter.ConstraintSystemCompletionMode.FULL) {
+            val finalSubstitutor =
+                candidate.system.asReadOnlyStorage().buildAbstractResultingSubstitutor(inferenceComponents.ctx) as ConeSubstitutor
+            return functionCall.transformSingle(
+                FirCallCompleterTransformer(session, finalSubstitutor, jump),
+                null
+            )
+        }
+        return functionCall
+    }
+
+    override fun transformFunctionCall(functionCall: FirFunctionCall, data: Any?): CompositeTransformResult<FirStatement> {
+        if (functionCall.calleeReference !is FirSimpleNamedReference) return functionCall.compose()
+        val expectedTypeRef = data as FirTypeRef?
+        val completeInference =
+            try {
+                val resultExpression = resolveCallAndSelectCandidate(functionCall, expectedTypeRef)
+                completeTypeInference(resultExpression, expectedTypeRef)
+            } catch (e: Throwable) {
+                throw RuntimeException("While resolving call ${functionCall.render()}", e)
+            }
+
+
+        return completeInference.compose()
+
+    }
+
+    private fun describeSymbol(symbol: ConeSymbol): String {
+        return when (symbol) {
+            is ConeClassLikeSymbol -> symbol.classId.asString()
+            is ConeCallableSymbol -> symbol.callableId.toString()
+            else -> "$symbol"
+        }
+    }
+
+    private fun createResolvedNamedReference(
+        namedReference: FirNamedReference,
+        candidates: Collection<Candidate>,
+        applicability: CandidateApplicability
+    ): FirNamedReference {
         val name = namedReference.name
-        return when (candidates.size) {
-            0 -> FirErrorNamedReference(
+        return when {
+            candidates.isEmpty() -> FirErrorNamedReference(
                 namedReference.session, namedReference.psi, "Unresolved name: $name"
             )
-            1 -> FirResolvedCallableReferenceImpl(
+            applicability < CandidateApplicability.RESOLVED -> {
+                FirErrorNamedReference(
+                    namedReference.session,
+                    namedReference.psi,
+                    "Inapplicable($applicability): ${candidates.map { describeSymbol(it.symbol) }}"
+                )
+            }
+            candidates.size == 1 -> FirNamedReferenceWithCandidate(
                 namedReference.session, namedReference.psi,
                 name, candidates.single()
             )
             else -> FirErrorNamedReference(
-                namedReference.session, namedReference.psi, "Ambiguity: $name, ${candidates.map { it.callableId }}"
+                namedReference.session, namedReference.psi, "Ambiguity: $name, ${candidates.map { describeSymbol(it.symbol) }}"
             )
         }
     }
 
-    override fun transformNamedReference(namedReference: FirNamedReference, data: Any?): CompositeTransformResult<FirNamedReference> {
-        if (namedReference is FirErrorNamedReference || namedReference is FirResolvedCallableReference) return namedReference.compose()
-        val referents = data as? List<ConeCallableSymbol> ?: return namedReference.compose()
-        return createResolvedNamedReference(namedReference, referents).compose()
-    }
+//    override fun transformNamedReference(namedReference: FirNamedReference, data: Any?): CompositeTransformResult<FirNamedReference> {
+//        if (namedReference is FirErrorNamedReference || namedReference is FirResolvedCallableReference) return namedReference.compose()
+//        val referents = data as? List<ConeCallableSymbol> ?: return namedReference.compose()
+//        return createResolvedNamedReference(namedReference, referents).compose()
+//    }
 
 
     override fun transformBlock(block: FirBlock, data: Any?): CompositeTransformResult<FirStatement> {
@@ -315,10 +403,10 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
     }
 
     override fun <T> transformConstExpression(constExpression: FirConstExpression<T>, data: Any?): CompositeTransformResult<FirStatement> {
-        val expectedType = data as? FirTypeRef
+        val expectedType = data as FirTypeRef?
 
         val kind = constExpression.kind
-        if (expectedType is FirImplicitTypeRef || expectedType == null ||
+        if (expectedType == null || expectedType is FirImplicitTypeRef || expectedType == null ||
             kind == IrConstKind.Null || kind == IrConstKind.Boolean || kind == IrConstKind.Char
         ) {
             val symbol = when (kind) {
@@ -424,7 +512,7 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
 
     override fun transformExpression(expression: FirExpression, data: Any?): CompositeTransformResult<FirStatement> {
         if (expression.resultType is FirImplicitTypeRef) {
-            val type = FirErrorTypeRefImpl(session, expression.psi, "Type calculating for ${expression.render()} is not supported")
+            val type = FirErrorTypeRefImpl(session, expression.psi, "Type calculating for ${expression::class} is not supported")
             expression.resultType = type
         }
         return super.transformExpression(expression, data)
@@ -568,3 +656,16 @@ inline fun <reified T : FirElement> ConeSymbol.firSafeNullable(): T? {
 interface ReturnTypeCalculator {
     fun tryCalculateReturnType(declaration: FirTypedDeclaration): FirResolvedTypeRef
 }
+
+private object StoreNameReference : FirTransformer<FirNamedReference>() {
+    override fun <E : FirElement> transformElement(element: E, data: FirNamedReference): CompositeTransformResult<E> {
+        return element.compose()
+    }
+
+    override fun transformNamedReference(
+        namedReference: FirNamedReference,
+        data: FirNamedReference
+    ): CompositeTransformResult<FirNamedReference> {
+        return data.compose()
+    }
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompleterTransformer.kt

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.transformers
+
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.copy
+import org.jetbrains.kotlin.fir.declarations.FirCallableMemberDeclaration
+import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
+import org.jetbrains.kotlin.fir.expressions.FirStatement
+import org.jetbrains.kotlin.fir.references.FirResolvedCallableReferenceImpl
+import org.jetbrains.kotlin.fir.resolve.calls.FirNamedReferenceWithCandidate
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
+import org.jetbrains.kotlin.fir.resolve.substitution.substituteOrNull
+import org.jetbrains.kotlin.fir.scopes.impl.withReplacedConeType
+import org.jetbrains.kotlin.fir.symbols.ConeSymbol
+import org.jetbrains.kotlin.fir.types.FirResolvedTypeRef
+import org.jetbrains.kotlin.fir.types.FirTypeProjectionWithVariance
+import org.jetbrains.kotlin.fir.types.impl.ConeTypeParameterTypeImpl
+import org.jetbrains.kotlin.fir.types.impl.FirResolvedTypeRefImpl
+import org.jetbrains.kotlin.fir.types.impl.FirTypeProjectionWithVarianceImpl
+import org.jetbrains.kotlin.fir.visitors.CompositeTransformResult
+import org.jetbrains.kotlin.fir.visitors.compose
+import org.jetbrains.kotlin.types.Variance
+
+class FirCallCompleterTransformer(
+    val session: FirSession,
+    private val finalSubstitutor: ConeSubstitutor,
+    private val typeCalculator: ReturnTypeCalculator
+) : FirAbstractTreeTransformer() {
+
+
+    override fun transformFunctionCall(functionCall: FirFunctionCall, data: Nothing?): CompositeTransformResult<FirStatement> {
+        val calleeReference = functionCall.calleeReference as? FirNamedReferenceWithCandidate ?: return functionCall.compose()
+        val functionCall = functionCall.transformChildren(this, data) as FirFunctionCall
+
+        val subCandidate = calleeReference.candidate
+        val declaration = subCandidate.symbol.firUnsafe<FirCallableMemberDeclaration>()
+        val newTypeParameters = declaration.typeParameters.map { ConeTypeParameterTypeImpl(it.symbol, false) }
+            .map { subCandidate.substitutor.substituteOrSelf(it) }
+            .map { finalSubstitutor.substituteOrSelf(it) }
+            .mapIndexed { index, type ->
+                when (val argument = functionCall.typeArguments.getOrNull(index)) {
+                    is FirTypeProjectionWithVariance -> {
+                        val typeRef = argument.typeRef as FirResolvedTypeRef
+                        FirTypeProjectionWithVarianceImpl(
+                            session,
+                            argument.psi,
+                            argument.variance,
+                            typeRef.withReplacedConeType(session, type)
+                        )
+                    }
+                    else -> {
+                        FirTypeProjectionWithVarianceImpl(
+                            session,
+                            argument?.psi,
+                            Variance.INVARIANT,
+                            FirResolvedTypeRefImpl(session, null, type, false, emptyList())
+                        )
+                    }
+                }
+            }
+
+        val typeRef = typeCalculator.tryCalculateReturnType(declaration)
+
+        val initialType = subCandidate.substitutor.substituteOrNull(typeRef.type)
+        val finalType = finalSubstitutor.substituteOrNull(initialType)
+
+        val resultType = typeRef.withReplacedConeType(session, finalType)
+
+        return functionCall.copy(
+            resultType = resultType,
+            typeArguments = newTypeParameters,
+            calleeReference = FirResolvedCallableReferenceImpl(
+                calleeReference.session,
+                calleeReference.psi,
+                calleeReference.name,
+                calleeReference.callableSymbol
+            )
+        ).compose()
+
+    }
+
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirAbstractSimpleImportingScope.kt

@@ -52,7 +52,7 @@ abstract class FirAbstractSimpleImportingScope(session: FirSession) : FirAbstrac
         if (imports.isEmpty()) return ProcessorAction.NEXT
 
         for (import in imports) {
-            if (processCallables(import, name, token, processor).stop()) {
+            if (processCallables(import, import.importedName!!, token, processor).stop()) {
                 return ProcessorAction.STOP
             }
         }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassSubstitutionScope.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.fir.declarations.FirNamedFunction
 import org.jetbrains.kotlin.fir.declarations.impl.FirDeclarationStatusImpl
 import org.jetbrains.kotlin.fir.declarations.impl.FirMemberFunctionImpl
 import org.jetbrains.kotlin.fir.declarations.impl.FirValueParameterImpl
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutorByMap
 import org.jetbrains.kotlin.fir.resolve.transformers.ReturnTypeCalculatorWithJump
 import org.jetbrains.kotlin.fir.resolve.transformers.firUnsafe
 import org.jetbrains.kotlin.fir.scopes.FirScope
@@ -20,72 +21,18 @@ import org.jetbrains.kotlin.fir.symbols.*
 import org.jetbrains.kotlin.fir.symbols.impl.FirFunctionSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirVariableSymbol
 import org.jetbrains.kotlin.fir.types.*
-import org.jetbrains.kotlin.fir.types.impl.ConeAbbreviatedTypeImpl
-import org.jetbrains.kotlin.fir.types.impl.ConeClassTypeImpl
 import org.jetbrains.kotlin.fir.types.impl.FirResolvedTypeRefImpl
 import org.jetbrains.kotlin.name.Name
 
 class FirClassSubstitutionScope(
     private val session: FirSession,
     private val useSiteScope: FirScope,
-    private val substitution: Map<ConeTypeParameterSymbol, ConeKotlinType>
+    substitution: Map<ConeTypeParameterSymbol, ConeKotlinType>
 ) : FirScope {
 
     private val fakeOverrides = mutableMapOf<ConeCallableSymbol, ConeCallableSymbol>()
 
-    private fun wrapProjection(old: ConeKotlinTypeProjection, newType: ConeKotlinType): ConeKotlinTypeProjection {
-        return when (old) {
-            is ConeStarProjection -> old
-            is ConeKotlinTypeProjectionIn -> ConeKotlinTypeProjectionIn(newType)
-            is ConeKotlinTypeProjectionOut -> ConeKotlinTypeProjectionOut(newType)
-            is ConeKotlinType -> newType
-            else -> old
-        }
-    }
-
-    private fun ConeKotlinType.substitute(): ConeKotlinType? {
-        if (this is ConeTypeParameterType) return substitution[lookupTag]
-
-        val newArguments by lazy { arrayOfNulls<ConeKotlinTypeProjection>(typeArguments.size) }
-        var initialized = false
-        for ((index, typeArgument) in this.typeArguments.withIndex()) {
-            val type = (typeArgument as? ConeTypedProjection)?.type ?: continue
-            val newType = type.substitute()
-            if (newType != null) {
-                initialized = true
-                newArguments[index] = wrapProjection(typeArgument, newType)
-            }
-        }
-
-        if (initialized) {
-            for ((index, typeArgument) in this.typeArguments.withIndex()) {
-                if (newArguments[index] == null) {
-                    newArguments[index] = typeArgument
-                }
-            }
-            @Suppress("UNCHECKED_CAST")
-            return when (this) {
-                is ConeKotlinErrorType -> error("Trying to substitute arguments for error type")
-                is ConeTypeParameterType -> error("Trying to substitute arguments for type parameter")
-                is ConeClassTypeImpl -> ConeClassTypeImpl(
-                    lookupTag,
-                    newArguments as Array<ConeKotlinTypeProjection>,
-                    nullability.isNullable
-                )
-                is ConeAbbreviatedTypeImpl -> ConeAbbreviatedTypeImpl(
-                    abbreviationLookupTag,
-                    newArguments as Array<ConeKotlinTypeProjection>,
-                    nullability.isNullable
-                )
-                is ConeFunctionType -> TODO("Substitute function type properly")
-                is ConeClassLikeType -> error("Unknown class-like type to substitute: $this, ${this::class}")
-                is ConeFlexibleType -> error("Trying to substitute arguments for flexible type")
-                is ConeCapturedType -> error("Not supported")
-            }
-        }
-        return null
-    }
-
+    private val substitutor = ConeSubstitutorByMap(substitution)
 
     override fun processFunctionsByName(name: Name, processor: (ConeFunctionSymbol) -> ProcessorAction): ProcessorAction {
         useSiteScope.processFunctionsByName(name) process@{ original ->
@@ -104,6 +51,10 @@ class FirClassSubstitutionScope(
 
     private val typeCalculator by lazy { ReturnTypeCalculatorWithJump(session) }
 
+    private fun ConeKotlinType.substitute(): ConeKotlinType? {
+        return substitutor.substituteOrNull(this)
+    }
+
     private fun createFakeOverride(original: ConeFunctionSymbol): FirFunctionSymbol {
 
         val member = original.firUnsafe<FirFunction>()

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

@@ -10,13 +10,13 @@ import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.expandedConeType
 import org.jetbrains.kotlin.fir.declarations.superConeTypes
+import org.jetbrains.kotlin.fir.resolve.calls.ConeTypeVariableTypeConstructor
+import org.jetbrains.kotlin.fir.resolve.constructType
 import org.jetbrains.kotlin.fir.resolve.directExpansionType
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.resolve.withArguments
-import org.jetbrains.kotlin.fir.symbols.ConeClassLikeSymbol
-import org.jetbrains.kotlin.fir.symbols.ConeClassSymbol
-import org.jetbrains.kotlin.fir.symbols.ConeSymbol
-import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterSymbol
+import org.jetbrains.kotlin.fir.service
+import org.jetbrains.kotlin.fir.symbols.*
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeAliasSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
@@ -47,9 +47,12 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
         assert(this is ConeKotlinType)
         return when (this) {
             is ConeAbbreviatedType -> directExpansionType(session)
+                ?: ConeClassErrorType("no expansion for type-alias: ${this.abbreviationLookupTag.classId}")
             is ConeCapturedType -> this
             is ConeLookupTagBasedType -> this
-            else -> null
+            is ConeDefinitelyNotNullType -> this
+            is ConeFlexibleType -> null
+            else -> error("Unknown simpleType: $this")
         }
     }
 
@@ -130,6 +133,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
     override fun SimpleTypeMarker.typeConstructor(): TypeConstructorMarker {
         return when (this) {
             is ConeCapturedType -> constructor
+            is ConeTypeVariableType -> this.lookupTag as ConeTypeVariableTypeConstructor // TODO: WTF
             is ConeLookupTagBasedType -> this.lookupTag.toSymbol(session) ?: ErrorTypeConstructor("Unresolved: ${this.lookupTag}")
             else -> error("?: ${this}")
         }
@@ -145,7 +149,8 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
     override fun SimpleTypeMarker.getArgument(index: Int): TypeArgumentMarker {
         require(this is ConeKotlinType)
 
-        return this.typeArguments[index]
+        return this.typeArguments.getOrNull(index)
+            ?: StandardClassIds.Any(session.service()).constructType(emptyArray(), false) // TODO wtf
     }
 
     override fun KotlinTypeMarker.asTypeArgument(): TypeArgumentMarker {
@@ -184,7 +189,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
     override fun TypeConstructorMarker.parametersCount(): Int {
         //require(this is ConeSymbol)
         return when (this) {
-            is ConeTypeParameterSymbol, is ConeCapturedTypeConstructor, is ErrorTypeConstructor -> 0
+            is ConeTypeParameterSymbol, is ConeCapturedTypeConstructor, is ErrorTypeConstructor, is ConeTypeVariableTypeConstructor -> 0
             is FirClassSymbol -> fir.typeParameters.size
             is FirTypeAliasSymbol -> fir.typeParameters.size
             else -> error("?!:10")
@@ -205,7 +210,8 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
         if (this is ErrorTypeConstructor) return emptyList()
         //require(this is ConeSymbol)
         return when (this) {
-            is ConeTypeParameterSymbol -> emptyList()
+            is ConeTypeVariableTypeConstructor -> emptyList()
+            is FirTypeParameterSymbol -> fir.bounds.map { it.coneTypeUnsafe() }
             is FirClassSymbol -> fir.superConeTypes
             is FirTypeAliasSymbol -> listOfNotNull(fir.expandedConeType)
             is ConeCapturedTypeConstructor -> supertypes!!
@@ -263,7 +269,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
     }
 
     override fun captureFromArguments(type: SimpleTypeMarker, status: CaptureStatus): SimpleTypeMarker? {
-        require(type is ConeLookupTagBasedType) { ":( $type" }
+        require(type is ConeKotlinType)
         val typeConstructor = type.typeConstructor()
         if (type.argumentsCount() != typeConstructor.parametersCount()) return null
         if (type.asArgumentList().all(this) { !it.isStarProjection() && it.getVariance() == TypeVariance.INV }) return null
@@ -314,7 +320,6 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
     }
 
     override fun TypeConstructorMarker.isAnyConstructor(): Boolean {
-        assert(this is ConeSymbol)
         return this is ConeClassLikeSymbol && classId.asString() == "kotlin/Any"
     }
 
@@ -332,36 +337,39 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext {
     override fun SimpleTypeMarker.isSingleClassifierType(): Boolean {
         if (isError()) return false
         if (this is ConeCapturedType) return true
+        if (this is ConeTypeVariableType) return false
         require(this is ConeLookupTagBasedType)
         val symbol = this.lookupTag.toSymbol(session)
         return symbol is FirClassSymbol ||
                 symbol is FirTypeParameterSymbol
     }
 
-    override fun intersectTypes(types: List<KotlinTypeMarker>): KotlinTypeMarker {
-        TODO("not implemented")
-    }
-
-    override fun intersectTypes(types: List<SimpleTypeMarker>): SimpleTypeMarker {
-        TODO("not implemented")
-    }
-
-    override fun prepareType(type: KotlinTypeMarker): KotlinTypeMarker {
-        TODO("not implemented")
-    }
-
-    override fun SimpleTypeMarker.isStubType(): Boolean {
-        TODO("not implemented")
-    }
-
     override fun captureFromExpression(type: KotlinTypeMarker): KotlinTypeMarker? {
         TODO("not implemented")
     }
 
     override fun SimpleTypeMarker.isPrimitiveType(): Boolean {
-        TODO("not implemented")
+        return false //TODO
     }
 
+    override fun SimpleTypeMarker.isStubType(): Boolean {
+        return false // TODO
+    }
+
+    override fun intersectTypes(types: List<SimpleTypeMarker>): SimpleTypeMarker {
+        return types.first() // TODO: proper implementation
+    }
+
+    override fun intersectTypes(types: List<KotlinTypeMarker>): KotlinTypeMarker {
+        return types.first() // TODO: proper implementation
+    }
+
+    override fun prepareType(type: KotlinTypeMarker): KotlinTypeMarker {
+        return when (type) {
+            is ConeAbbreviatedType -> prepareType(type.directExpansionType(session) ?: ConeClassErrorType("unresolved"))
+            else -> type
+        }
+    }
 }
 
 class ConeTypeCheckerContext(override val isErrorTypeEqualsToAnything: Boolean, override val session: FirSession) :
@@ -379,16 +387,11 @@ class ConeTypeCheckerContext(override val isErrorTypeEqualsToAnything: Boolean,
         return a == b
     }
 
-    override fun intersectTypes(types: List<KotlinTypeMarker>): KotlinTypeMarker {
-        return types.first() // TODO: proper implementation
+    override fun prepareType(type: KotlinTypeMarker): KotlinTypeMarker {
+        return super<ConeTypeContext>.prepareType(type)
     }
 
     override val KotlinTypeMarker.isAllowedTypeVariable: Boolean
         get() = false
 
-
-    override fun prepareType(type: KotlinTypeMarker): KotlinTypeMarker {
-        return super<ConeTypeContext>.prepareType(type)
-    }
-
 }

compiler/fir/resolve/testData/resolve/expresssions/access.txt

@@ -36,8 +36,8 @@ FILE: access.kt
             ^plus String()
         }
 
-        public final fun R|Foo|.check(): <ERROR TYPE REF: Ambiguity: plus, [kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus]> {
-            ^check R|/Foo.abc|().<Ambiguity: plus, [kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus]>#(R|/Bar.bar|())
+        public final fun R|Foo|.check(): R|kotlin/String| {
+            ^check R|/Foo.abc|().R|/Bar.plus|(R|/Bar.bar|())
         }
 
     }

compiler/fir/resolve/testData/resolve/expresssions/checkArguments.kt

@@ -0,0 +1,16 @@
+class A
+open class B
+class C : B
+
+
+fun bar(a: A) = a
+fun bar(b: B) = b
+
+fun foo() {
+    val a = A()
+    val b = B()
+    val c = C()
+    val ra = bar(a)
+    val rb = bar(b)
+    val rc = bar(c)
+}

compiler/fir/resolve/testData/resolve/expresssions/checkArguments.txt

@@ -0,0 +1,27 @@
+FILE: checkArguments.kt
+    public final class A : R|kotlin/Any| {
+        public constructor(): super<R|kotlin/Any|>()
+
+    }
+    public open class B : R|kotlin/Any| {
+        public constructor(): super<R|kotlin/Any|>()
+
+    }
+    public final class C : R|B|, R|kotlin/Any| {
+        public constructor(): super<R|kotlin/Any|>()
+
+    }
+    public final fun bar(a: R|A|): R|A| {
+        ^bar R|<local>/a|
+    }
+    public final fun bar(b: R|B|): R|B| {
+        ^bar R|<local>/b|
+    }
+    public final fun foo(): R|kotlin/Unit| {
+        lval a: R|A| = R|/A.A|()
+        lval b: R|B| = R|/B.B|()
+        lval c: R|C| = R|/C.C|()
+        lval ra: R|A| = R|/bar|(R|<local>/a|)
+        lval rb: R|B| = R|/bar|(R|<local>/b|)
+        lval rc: R|B| = R|/bar|(R|<local>/c|)
+    }

compiler/fir/resolve/testData/resolve/expresssions/inference/id.kt

@@ -0,0 +1,8 @@
+fun <T> id(t: T) = t
+
+
+fun main() {
+    val a = id("string")
+    val b = id(null)
+    val c = id(id(a))
+}

compiler/fir/resolve/testData/resolve/expresssions/inference/id.txt

@@ -0,0 +1,9 @@
+FILE: id.kt
+    public final fun <T> id(t: R|T|): R|T| {
+        ^id R|<local>/t|
+    }
+    public final fun main(): R|kotlin/Unit| {
+        lval a: R|kotlin/String| = R|/id|<R|kotlin/String|>(String(string))
+        lval b: R|kotlin/Nothing|? = R|/id|<R|kotlin/Nothing|?>(Null(null))
+        lval c: R|kotlin/String| = R|/id|<R|kotlin/String|>(R|/id|<R|kotlin/String|>(R|<local>/a|))
+    }

compiler/fir/resolve/testData/resolve/expresssions/inference/typeParameters.kt

@@ -0,0 +1,11 @@
+interface Foo
+class FooImpl : Foo
+class Bar
+
+fun <T : Foo> foo(t: T) = t
+
+
+fun main(fooImpl: FooImpl, bar: Bar) {
+    val a = foo(fooImpl)
+    val b = foo(bar)
+}

compiler/fir/resolve/testData/resolve/expresssions/inference/typeParameters.txt

@@ -0,0 +1,22 @@
+FILE: typeParameters.kt
+    public abstract interface Foo : R|kotlin/Any| {
+    }
+    public final class FooImpl : R|Foo| {
+        public constructor(): R|FooImpl| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final class Bar : R|kotlin/Any| {
+        public constructor(): R|Bar| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final fun <T : R|Foo|> foo(t: R|T|): R|T| {
+        ^foo R|<local>/t|
+    }
+    public final fun main(fooImpl: R|FooImpl|, bar: R|Bar|): R|kotlin/Unit| {
+        lval a: R|FooImpl| = R|/foo|<R|FooImpl|>(R|<local>/fooImpl|)
+        lval b: <ERROR TYPE REF: Inapplicable(INAPPLICABLE): [/foo]> = <Inapplicable(INAPPLICABLE): [/foo]>#(R|<local>/bar|)
+    }

compiler/fir/resolve/testData/resolve/expresssions/inference/typeParameters2.kt

@@ -0,0 +1,11 @@
+interface Foo
+class FooImpl : Foo
+class FooBarImpl : Foo
+
+fun <T : Foo> foo(t: T) = t
+
+
+fun main(fooImpl: FooImpl, fooBarImpl: FooBarImpl) {
+    val a = foo<FooImpl>(fooBarImpl)
+    val b = foo<Foo>(fooImpl)
+}

compiler/fir/resolve/testData/resolve/expresssions/inference/typeParameters2.txt

@@ -0,0 +1,22 @@
+FILE: typeParameters2.kt
+    public abstract interface Foo : R|kotlin/Any| {
+    }
+    public final class FooImpl : R|Foo| {
+        public constructor(): R|FooImpl| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final class FooBarImpl : R|Foo| {
+        public constructor(): R|FooBarImpl| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final fun <T : R|Foo|> foo(t: R|T|): R|T| {
+        ^foo R|<local>/t|
+    }
+    public final fun main(fooImpl: R|FooImpl|, fooBarImpl: R|FooBarImpl|): R|kotlin/Unit| {
+        lval a: <ERROR TYPE REF: Inapplicable(INAPPLICABLE): [/foo]> = <Inapplicable(INAPPLICABLE): [/foo]>#<R|FooImpl|>(R|<local>/fooBarImpl|)
+        lval b: R|Foo| = R|/foo|<R|Foo|>(R|<local>/fooImpl|)
+    }

compiler/fir/resolve/testData/resolve/fromBuilder/enums.txt

@@ -70,7 +70,7 @@ FILE: enums.kt
 
         }
 
-        public final val g: R|kotlin/Double| = <Unresolved name: G>#.<Unresolved name: times>#(R|/Planet.m|).<Unresolved name: div>#(R|/Planet.r|.<Ambiguity: times, [kotlin/Double.times, kotlin/Double.times, kotlin/Double.times, kotlin/Double.times, kotlin/Double.times, kotlin/Double.times]>#(R|/Planet.r|))
+        public final val g: R|kotlin/Double| = <Unresolved name: G>#.<Unresolved name: times>#(R|/Planet.m|).<Unresolved name: div>#(R|/Planet.r|.R|kotlin/Double.times|(R|/Planet.r|))
             public get(): R|kotlin/Double|
 
         public abstract fun sayHello(): R|kotlin/Unit|

compiler/fir/resolve/testData/resolve/stdlib/helloWorld.kt

@@ -0,0 +1,3 @@
+fun main() {
+    println("Hello, world!")
+}

compiler/fir/resolve/testData/resolve/stdlib/helloWorld.txt

@@ -0,0 +1,4 @@
+FILE: helloWorld.kt
+    public final fun main(): R|kotlin/Unit| {
+        R|kotlin/io/println|(String(Hello, world!))
+    }

compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirResolveTestCaseGenerated.java

@@ -159,6 +159,11 @@ public class FirResolveTestCaseGenerated extends AbstractFirResolveTestCase {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/fir/resolve/testData/resolve/expresssions"), Pattern.compile("^([^.]+)\\.kt$"), TargetBackend.ANY, true);
         }
 
+        @TestMetadata("checkArguments.kt")
+        public void testCheckArguments() throws Exception {
+            runTest("compiler/fir/resolve/testData/resolve/expresssions/checkArguments.kt");
+        }
+
         @TestMetadata("constructor.kt")
         public void testConstructor() throws Exception {
             runTest("compiler/fir/resolve/testData/resolve/expresssions/constructor.kt");
@@ -189,6 +194,36 @@ public class FirResolveTestCaseGenerated extends AbstractFirResolveTestCase {
             runTest("compiler/fir/resolve/testData/resolve/expresssions/when.kt");
         }
 
+        @TestMetadata("compiler/fir/resolve/testData/resolve/expresssions/inference")
+        @TestDataPath("$PROJECT_ROOT")
+        @RunWith(JUnit3RunnerWithInners.class)
+        public static class Inference extends AbstractFirResolveTestCase {
+            private void runTest(String testDataFilePath) throws Exception {
+                KotlinTestUtils.runTest(this::doTest, TargetBackend.ANY, testDataFilePath);
+            }
+
+            public void testAllFilesPresentInInference() throws Exception {
+                KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(),
+                                                                new File("compiler/fir/resolve/testData/resolve/expresssions/inference"),
+                                                                Pattern.compile("^([^.]+)\\.kt$"), TargetBackend.ANY, true);
+            }
+
+            @TestMetadata("id.kt")
+            public void testId() throws Exception {
+                runTest("compiler/fir/resolve/testData/resolve/expresssions/inference/id.kt");
+            }
+
+            @TestMetadata("typeParameters.kt")
+            public void testTypeParameters() throws Exception {
+                runTest("compiler/fir/resolve/testData/resolve/expresssions/inference/typeParameters.kt");
+            }
+
+            @TestMetadata("typeParameters2.kt")
+            public void testTypeParameters2() throws Exception {
+                runTest("compiler/fir/resolve/testData/resolve/expresssions/inference/typeParameters2.kt");
+            }
+        }
+
         @TestMetadata("compiler/fir/resolve/testData/resolve/expresssions/invoke")
         @TestDataPath("$PROJECT_ROOT")
         @RunWith(JUnit3RunnerWithInners.class)

compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirResolveTestCaseWithStdlibGenerated.java

@@ -39,6 +39,11 @@ public class FirResolveTestCaseWithStdlibGenerated extends AbstractFirResolveTes
         runTest("compiler/fir/resolve/testData/resolve/stdlib/functionX.kt");
     }
 
+    @TestMetadata("helloWorld.kt")
+    public void testHelloWorld() throws Exception {
+        runTest("compiler/fir/resolve/testData/resolve/stdlib/helloWorld.kt");
+    }
+
     @TestMetadata("reflectionClass.kt")
     public void testReflectionClass() throws Exception {
         runTest("compiler/fir/resolve/testData/resolve/stdlib/reflectionClass.kt");

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt

@@ -34,6 +34,8 @@ fun FirElement.render(): String = buildString { this@render.accept(FirRenderer(t
 
 fun ConeKotlinType.render(): String {
     return when (this) {
+        is ConeTypeVariableType -> "TypeVariable(${this.lookupTag.name})"
+        is ConeDefinitelyNotNullType -> "${original.render()}!"
         is ConeKotlinErrorType -> "error: $reason"
         is ConeClassErrorType -> "class error: $reason"
         is ConeCapturedType -> "captured type: lowerType = ${lowerType?.render()}"

compiler/fir/tree/src/org/jetbrains/kotlin/fir/references/FirResolvedCallableReferenceImpl.kt

@@ -12,7 +12,7 @@ import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.symbols.ConeCallableSymbol
 import org.jetbrains.kotlin.name.Name
 
-class FirResolvedCallableReferenceImpl(
+open class FirResolvedCallableReferenceImpl(
     session: FirSession,
     psi: PsiElement?,
     override val name: Name,

compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/impl/FirTypePlaceholderProjection.kt

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. 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.impl
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.types.FirTypeProjection
+
+object FirTypePlaceholderProjection : FirTypeProjection {
+    override val psi: PsiElement?
+        get() = null // TODO
+    override val session: FirSession
+        get() = error("ahahahhahah")
+}