diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionCallbacksImpl.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionCallbacksImpl.kt
index a0f6cbe8f6e..2fd5855f2f5 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionCallbacksImpl.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionCallbacksImpl.kt
@@ -120,6 +120,7 @@ class KotlinResolutionCallbacksImpl(
             val lastExpressionArgument = getLastDeparentesizedExpression(psiCallArgument)?.let { lastExpression ->
                 if (expectedReturnType?.isUnit() == true) return@let null // coercion to Unit
 
+                // todo lastExpression can be if without else
                 val lastExpressionType = trace.getType(lastExpression)
                 val lastExpressionTypeInfo = KotlinTypeInfo(lastExpressionType, lambdaInfo.dataFlowInfoAfter ?: functionTypeInfo.dataFlowInfo)
                 createCallArgument(lastExpression, lastExpressionTypeInfo)
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinToResolvedCallTransformer.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinToResolvedCallTransformer.kt
index 96c5a3b917f..c7c45d1e044 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinToResolvedCallTransformer.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinToResolvedCallTransformer.kt
@@ -70,6 +70,7 @@ class KotlinToResolvedCallTransformer(
             allResolvedCalls.add(result)
 
             if (trace != null) {
+                // todo: check checkers order
                 val callCheckerContext = CallCheckerContext(context.replaceBindingTrace(trace), languageFeatureSettings)
                 for (resolvedCall in allResolvedCalls) {
                     runCallCheckers(resolvedCall, callCheckerContext)
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewCallArguments.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewCallArguments.kt
index 4843b961f9e..cc42e9b2cbb 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewCallArguments.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewCallArguments.kt
@@ -221,7 +221,7 @@ internal fun createSimplePSICallArgument(
     // we should use DFI after this argument, because there can be some useful smartcast. Popular case: if branches.
     val receiverToCast = transformToReceiverWithSmartCastInfo(
             ownerDescriptor, bindingContext,
-            typeInfoForArgument.dataFlowInfo,
+            typeInfoForArgument.dataFlowInfo, // dataFlowInfoBeforeThisArgument cannot be used here, because of if() { if (x != null) return; x }
             ExpressionReceiver.create(ktExpression, baseType, bindingContext)
     ).prepareReceiverRegardingCaptureTypes()
 
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewResolutionOldInference.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewResolutionOldInference.kt
index c42a663c96c..3318c527886 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewResolutionOldInference.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewResolutionOldInference.kt
@@ -108,7 +108,7 @@ class NewResolutionOldInference(
             ): ScopeTowerProcessor<MyCandidate> {
                 val functionFactory = outer.CandidateFactoryImpl(name, context, tracing)
                 val variableFactory = outer.CandidateFactoryImpl(name, context, tracing)
-                return CompositeScopeTowerProcessor(
+                return PrioritizedCompositeScopeTowerProcessor(
                         createSimpleFunctionProcessor(scopeTower, name, functionFactory, explicitReceiver, classValueReceiver = false),
                         createVariableProcessor(scopeTower, name, variableFactory, explicitReceiver, classValueReceiver = false)
                 )
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/PSICallResolver.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/PSICallResolver.kt
index bb339fcd6d2..8ee6ebeac74 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/PSICallResolver.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/PSICallResolver.kt
@@ -531,14 +531,14 @@ class PSICallResolver(
                             LHSResult.Object(ClassQualifier(calleeExpression, classifier))
                         }
                         else {
-                            LHSResult.Empty // this is error case actually
+                            LHSResult.Error
                         }
                     }
                     else {
                         val fakeArgument = FakeValueArgumentForLeftCallableReference(ktExpression)
 
                         val kotlinCallArgument = createSimplePSICallArgument(context, fakeArgument, lhsResult.typeInfo)
-                        kotlinCallArgument?.let { LHSResult.Expression(it as SimpleKotlinCallArgument) } ?: LHSResult.Empty
+                        kotlinCallArgument?.let { LHSResult.Expression(it as SimpleKotlinCallArgument) } ?: LHSResult.Error
                     }
                 }
                 is DoubleColonLHS.Type -> {
@@ -547,7 +547,7 @@ class PSICallResolver(
                         LHSResult.Type(qualifier, lhsResult.type.unwrap())
                     }
                     else {
-                        LHSResult.Empty // this is error case actually
+                        LHSResult.Error
                     }
                 }
             }
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ExpressionTypingServices.java b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ExpressionTypingServices.java
index b6a9cc5f973..542ef78086c 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ExpressionTypingServices.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ExpressionTypingServices.java
@@ -318,7 +318,6 @@ public class ExpressionTypingServices {
             ContextDependency dependency = context.contextDependency;
             if (KotlinResolutionConfigurationKt.getUSE_NEW_INFERENCE()) {
                 dependency = ContextDependency.INDEPENDENT;
-
             }
 
             return blockLevelVisitor.getTypeInfo(statementExpression, context.replaceExpectedType(expectedType).replaceContextDependency(dependency), true);
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolution.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolution.kt
index ea2bc6ab9f3..0232530dbc5 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolution.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolution.kt
@@ -35,13 +35,10 @@ import org.jetbrains.kotlin.resolve.scopes.receivers.DetailedReceiver
 import org.jetbrains.kotlin.resolve.scopes.receivers.QualifierReceiver
 import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue
 import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValueWithSmartCastInfo
-import org.jetbrains.kotlin.types.ErrorUtils
-import org.jetbrains.kotlin.types.KotlinType
-import org.jetbrains.kotlin.types.UnwrappedType
+import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.expressions.CoercionStrategy
 import org.jetbrains.kotlin.types.typeUtil.immediateSupertypes
 import org.jetbrains.kotlin.types.typeUtil.isUnit
-import org.jetbrains.kotlin.types.upperIfFlexible
 import org.jetbrains.kotlin.utils.SmartList
 import org.jetbrains.kotlin.utils.addIfNotNull
 
@@ -87,7 +84,7 @@ class CallableReferenceCandidate(
 fun createCallableReferenceProcessor(factory: CallableReferencesCandidateFactory): ScopeTowerProcessor<CallableReferenceCandidate> {
     val lhsResult = factory.argument.lhsResult
     when (lhsResult) {
-        LHSResult.Empty, is LHSResult.Expression -> {
+        LHSResult.Empty, LHSResult.Error, is LHSResult.Expression -> {
             val explicitReceiver = (lhsResult as? LHSResult.Expression)?.lshCallArgument?.receiver
             return factory.createCallableProcessor(explicitReceiver)
         }
@@ -95,18 +92,18 @@ fun createCallableReferenceProcessor(factory: CallableReferencesCandidateFactory
             val static = factory.createCallableProcessor(lhsResult.qualifier)
             val unbound = factory.createCallableProcessor(lhsResult.unboundDetailedReceiver)
 
-            // note that if we use CompositeScopeTowerProcessor then static will win over unbound members
-            val staticOrUnbound = CompositeSimpleScopeTowerProcessor(static, unbound)
+            // note that if we use PrioritizedCompositeScopeTowerProcessor then static will win over unbound members
+            val staticOrUnbound = SamePriorityCompositeScopeTowerProcessor(static, unbound)
 
             val asValue = lhsResult.qualifier.classValueReceiverWithSmartCastInfo ?: return staticOrUnbound
-            return CompositeScopeTowerProcessor(staticOrUnbound, factory.createCallableProcessor(asValue))
+            return PrioritizedCompositeScopeTowerProcessor(staticOrUnbound, factory.createCallableProcessor(asValue))
         }
         is LHSResult.Object -> {
             // callable reference to nested class constructor
             val static = factory.createCallableProcessor(lhsResult.qualifier)
             val boundObjectReference = factory.createCallableProcessor(lhsResult.objectValueReceiver)
 
-            return CompositeSimpleScopeTowerProcessor(static, boundObjectReference)
+            return SamePriorityCompositeScopeTowerProcessor(static, boundObjectReference)
         }
     }
 }
@@ -120,33 +117,37 @@ fun ConstraintSystemOperation.checkCallableReference(
         expectedType: UnwrappedType?,
         ownerDescriptor: DeclarationDescriptor
 ): Pair<FreshVariableNewTypeSubstitutor, KotlinCallDiagnostic?> {
-    val invisibleMember = Visibilities.findInvisibleMember(dispatchReceiver?.asReceiverValueForVisibilityChecks,
-                                                           candidateDescriptor, ownerDescriptor)
-
     val position = ArgumentConstraintPosition(argument)
 
-    val toFreshSubstitutor = createToFreshVariableSubstitutorAndAddInitialConstraints(candidateDescriptor, this, kotlinCall = null)
-    val reflectionType = toFreshSubstitutor.safeSubstitute(reflectionCandidateType)
+    val toFreshSubstitutor = createToFreshVariableSubstitutorAndAddInitialConstraints(candidateDescriptor, this)
 
     if (expectedType != null) {
-        addSubtypeConstraint(reflectionType, expectedType, position)
+        addSubtypeConstraint(toFreshSubstitutor.safeSubstitute(reflectionCandidateType), expectedType, position)
     }
 
     addReceiverConstraint(toFreshSubstitutor, dispatchReceiver, candidateDescriptor.dispatchReceiverParameter, position)
     addReceiverConstraint(toFreshSubstitutor, extensionReceiver, candidateDescriptor.extensionReceiverParameter, position)
 
+    val invisibleMember = Visibilities.findInvisibleMember(dispatchReceiver?.asReceiverValueForVisibilityChecks,
+                                                           candidateDescriptor, ownerDescriptor)
     return toFreshSubstitutor to invisibleMember?.let(::VisibilityError)
 }
 
 
 private fun ConstraintSystemOperation.addReceiverConstraint(
         toFreshSubstitutor: FreshVariableNewTypeSubstitutor,
-        receiver: CallableReceiver?,
-        candidateReceiver: ReceiverParameterDescriptor?,
+        receiverArgument: CallableReceiver?,
+        receiverParameter: ReceiverParameterDescriptor?,
         position: ArgumentConstraintPosition
 ) {
-    val expectedType = toFreshSubstitutor.safeSubstitute(candidateReceiver?.value?.type?.unwrap() ?: return)
-    val receiverType = receiver?.receiver?.stableType ?: return
+    if (receiverArgument == null || receiverParameter == null) {
+        assert(receiverArgument == null) { "Receiver argument should be null if parameter is: $receiverArgument" }
+        assert(receiverParameter == null) { "Receiver parameter should be null if argument is: $receiverParameter" }
+        return
+    }
+
+    val expectedType = toFreshSubstitutor.safeSubstitute(receiverParameter.value.type.unwrap())
+    val receiverType = receiverArgument.receiver.stableType
     addSubtypeConstraint(receiverType, expectedType, position)
 }
 
@@ -170,11 +171,17 @@ class CallableReferencesCandidateFactory(
         val dispatchCallableReceiver = towerCandidate.dispatchReceiver?.let { toCallableReceiver(it, explicitReceiverKind == DISPATCH_RECEIVER) }
         val extensionCallableReceiver = extensionReceiver?.let { toCallableReceiver(it, explicitReceiverKind == EXTENSION_RECEIVER) }
         val candidateDescriptor = towerCandidate.descriptor
+        val diagnostics = SmartList<KotlinCallDiagnostic>()
 
-        val (reflectionCandidateType, defaults) = buildReflectionType(candidateDescriptor,
-                                                          dispatchCallableReceiver,
-                                                          extensionCallableReceiver,
-                                                          expectedType)
+        val (reflectionCandidateType, defaults) = buildReflectionType(
+                candidateDescriptor,
+                dispatchCallableReceiver,
+                extensionCallableReceiver,
+                expectedType)
+
+        if (defaults != 0) {
+            diagnostics.add(CallableReferencesDefaultArgumentUsed(argument, candidateDescriptor, defaults))
+        }
 
         if (candidateDescriptor !is CallableMemberDescriptor) {
             val status = ResolutionCandidateStatus(listOf(NotCallableMemberReference(argument, candidateDescriptor)))
@@ -182,15 +189,15 @@ class CallableReferencesCandidateFactory(
                                               explicitReceiverKind, reflectionCandidateType, defaults, status)
         }
 
-        val diagnostics = SmartList<KotlinCallDiagnostic>()
         diagnostics.addAll(towerCandidate.diagnostics)
         // todo smartcast on receiver diagnostic and CheckInstantiationOfAbstractClass
 
         compatibilityChecker {
             if (it.hasContradiction) return@compatibilityChecker
 
-            val (_, visibilityError) = it.checkCallableReference(argument, dispatchCallableReceiver, extensionCallableReceiver, candidateDescriptor,
-                                      reflectionCandidateType, expectedType, scopeTower.lexicalScope.ownerDescriptor)
+            val (_, visibilityError) = it.checkCallableReference(
+                    argument, dispatchCallableReceiver, extensionCallableReceiver, candidateDescriptor,
+                    reflectionCandidateType, expectedType, scopeTower.lexicalScope.ownerDescriptor)
 
             diagnostics.addIfNotNull(visibilityError)
 
@@ -244,8 +251,10 @@ class CallableReferencesCandidateFactory(
         }
         if (mappedArguments.any { it == null }) return null
 
-        val unitExpectedType = functionType.let(KotlinType::getReturnTypeFromFunctionType).takeIf { it.upperIfFlexible().isUnit() }
-        val coercion = if (unitExpectedType != null) CoercionStrategy.COERCION_TO_UNIT else CoercionStrategy.NO_COERCION
+        // lower(Unit!) = Unit
+        val returnExpectedType = functionType.getReturnTypeFromFunctionType().lowerIfFlexible()
+
+        val coercion = if (returnExpectedType.isUnit()) CoercionStrategy.COERCION_TO_UNIT else CoercionStrategy.NO_COERCION
 
         @Suppress("UNCHECKED_CAST")
         return Triple(mappedArguments as Array<KotlinType>, coercion, defaults)
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolver.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolver.kt
index 221d40ae6a5..7ce5c9c64ef 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolver.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/CallableReferenceResolver.kt
@@ -30,6 +30,7 @@ import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
 import org.jetbrains.kotlin.resolve.calls.tower.ImplicitScopeTower
 import org.jetbrains.kotlin.resolve.calls.tower.TowerResolver
 import org.jetbrains.kotlin.types.UnwrappedType
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 
 class CallableReferenceOverloadConflictResolver(
@@ -68,11 +69,11 @@ class CallableReferenceResolver(
         val argument = postponedArgument.argument
         val expectedType = postponedArgument.expectedType
 
-        val subLHSCall = ((argument.lhsResult as? LHSResult.Expression)?.lshCallArgument as? SubKotlinCallArgument)
+        val subLHSCall = argument.lhsResult.safeAs<LHSResult.Expression>()?.lshCallArgument.safeAs<SubKotlinCallArgument>()
         if (subLHSCall != null) {
             csBuilder.addInnerCall(subLHSCall.resolvedCall)
         }
-        val candidates = runRLSResolution(scopeTower, argument, expectedType) { checkCallableReference ->
+        val candidates = runRHSResolution(scopeTower, argument, expectedType) { checkCallableReference ->
             csBuilder.runTransaction { checkCallableReference(this); false }
         }
         val chosenCandidate = when (candidates.size) {
@@ -93,18 +94,20 @@ class CallableReferenceResolver(
     }
 
 
-    private fun runRLSResolution(
+    private fun runRHSResolution(
             scopeTower: ImplicitScopeTower,
             callableReference: CallableReferenceKotlinCallArgument,
             expectedType: UnwrappedType?, // this type can have not fixed type variable inside
-            compatibilityChecker: ((ConstraintSystemOperation) -> Unit) -> Unit // you can run anything throw this operation and all this operation will be roll backed
+            compatibilityChecker: ((ConstraintSystemOperation) -> Unit) -> Unit // you can run anything throw this operation and all this operation will be rolled back
     ): Set<CallableReferenceCandidate> {
         val factory = CallableReferencesCandidateFactory(callableReference, callComponents, scopeTower, compatibilityChecker, expectedType)
         val processor = createCallableReferenceProcessor(factory)
         val candidates = towerResolver.runResolve(scopeTower, processor, useOrder = true)
-        return callableReferenceOverloadConflictResolver.chooseMaximallySpecificCandidates(candidates, CheckArgumentTypesMode.CHECK_VALUE_ARGUMENTS,
-                                                                   discriminateGenerics = false,
-                                                                   isDebuggerContext = scopeTower.isDebuggerContext)
+        return callableReferenceOverloadConflictResolver.chooseMaximallySpecificCandidates(
+                candidates,
+                CheckArgumentTypesMode.CHECK_VALUE_ARGUMENTS,
+                discriminateGenerics = false, // we can't specify generics explicitly for callable references
+                isDebuggerContext = scopeTower.isDebuggerContext)
     }
 }
 
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponeArgumentsChecks.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponeArgumentsChecks.kt
index 812acbea6fb..1c9a0d2c997 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponeArgumentsChecks.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponeArgumentsChecks.kt
@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.resolve.calls.inference.model.TypeVariableForLambdaR
 import org.jetbrains.kotlin.resolve.calls.model.*
 import org.jetbrains.kotlin.types.UnwrappedType
 import org.jetbrains.kotlin.types.typeUtil.builtIns
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 fun createPostponedArgumentAndPerformInitialChecks(
         csBuilder: ConstraintSystemBuilder,
@@ -60,20 +61,20 @@ private fun preprocessLambdaArgument(
         if (argument.parametersTypes != null) {
             parameters = argument.parametersTypes!!.mapIndexed {
                 index, type ->
-                type ?: expectedParameters.getOrNull(index)?.type?.unwrap() ?: builtIns.anyType
+                type ?: expectedParameters.getOrNull(index)?.type?.unwrap() ?: builtIns.nullableAnyType
             }
         }
         else {
             // lambda without explicit parameters: { }
             parameters = expectedParameters.map { it.type.unwrap() }
         }
-        returnType = (argument as? FunctionExpression)?.returnType ?: expectedType.getReturnTypeFromFunctionType().unwrap()
+        returnType = argument.safeAs<FunctionExpression>()?.returnType ?: expectedType.getReturnTypeFromFunctionType().unwrap()
     }
     else {
         val isFunctionSupertype = KotlinBuiltIns.isNotNullOrNullableFunctionSupertype(expectedType)
-        receiverType = (argument as? FunctionExpression)?.receiverType
+        receiverType = argument.safeAs<FunctionExpression>()?.receiverType
         parameters = argument.parametersTypes?.map { it ?: builtIns.nothingType } ?: emptyList()
-        returnType = (argument as? FunctionExpression)?.returnType ?:
+        returnType = argument.safeAs<FunctionExpression>()?.returnType ?:
                      expectedType.arguments.singleOrNull()?.type?.unwrap()?.takeIf { isFunctionSupertype } ?:
                      createFreshTypeVariableForLambdaReturnType(csBuilder, argument, builtIns)
 
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/ResolutionParts.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/ResolutionParts.kt
index a19575623f0..3c839e0390b 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/ResolutionParts.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/ResolutionParts.kt
@@ -109,7 +109,7 @@ internal object CreateDescriptorWithFreshTypeVariables : ResolutionPart {
             descriptorWithFreshTypes = candidateDescriptor
             return emptyList()
         }
-        val toFreshVariables = createToFreshVariableSubstitutorAndAddInitialConstraints(candidateDescriptor, csBuilder, kotlinCall)
+        val toFreshVariables = createToFreshVariableSubstitutorAndAddInitialConstraints(candidateDescriptor, csBuilder)
         typeVariablesForFreshTypeParameters = toFreshVariables.freshVariables
 
         // bad function -- error on declaration side
@@ -164,12 +164,11 @@ internal object CreateDescriptorWithFreshTypeVariables : ResolutionPart {
 
     fun createToFreshVariableSubstitutorAndAddInitialConstraints(
             candidateDescriptor: CallableDescriptor,
-            csBuilder: ConstraintSystemOperation,
-            kotlinCall: KotlinCall?
+            csBuilder: ConstraintSystemOperation
     ): FreshVariableNewTypeSubstitutor {
         val typeParameters = candidateDescriptor.typeParameters
 
-        val freshTypeVariables = typeParameters.map { TypeVariableFromCallableDescriptor(it, kotlinCall) }
+        val freshTypeVariables = typeParameters.map { TypeVariableFromCallableDescriptor(it) }
 
         val toFreshVariables = FreshVariableNewTypeSubstitutor(freshTypeVariables)
 
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/model/TypeVariable.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/model/TypeVariable.kt
index 0b90785f4d7..575abd9706f 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/model/TypeVariable.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/model/TypeVariable.kt
@@ -20,11 +20,12 @@ import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
-import org.jetbrains.kotlin.resolve.calls.model.KotlinCall
 import org.jetbrains.kotlin.resolve.calls.model.LambdaKotlinCallArgument
 import org.jetbrains.kotlin.resolve.descriptorUtil.builtIns
-import org.jetbrains.kotlin.resolve.scopes.MemberScope
-import org.jetbrains.kotlin.types.*
+import org.jetbrains.kotlin.types.KotlinType
+import org.jetbrains.kotlin.types.KotlinTypeFactory
+import org.jetbrains.kotlin.types.SimpleType
+import org.jetbrains.kotlin.types.TypeConstructor
 import org.jetbrains.kotlin.types.checker.NewTypeVariableConstructor
 
 
@@ -53,8 +54,7 @@ sealed class NewTypeVariable(builtIns: KotlinBuiltIns, name: String) {
 }
 
 class TypeVariableFromCallableDescriptor(
-        val originalTypeParameter: TypeParameterDescriptor,
-        val call: KotlinCall? = null
+        val originalTypeParameter: TypeParameterDescriptor
 ) : NewTypeVariable(originalTypeParameter.builtIns, originalTypeParameter.name.identifier)
 
 class TypeVariableForLambdaReturnType(
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallArguments.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallArguments.kt
index 778d8d1f542..5fdaf63588d 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallArguments.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallArguments.kt
@@ -110,6 +110,8 @@ sealed class LHSResult {
 
     // todo this case is forbid for now
     object Empty: LHSResult()
+
+    object Error: LHSResult()
 }
 
 interface CallableReferenceKotlinCallArgument : PostponableKotlinCallArgument {
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallDiagnistics.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallDiagnistics.kt
index 17ead7fdc52..fbb7d4a5f63 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallDiagnistics.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallDiagnistics.kt
@@ -98,6 +98,15 @@ class CallableReferenceNotCompatible(
         val callableReverenceType: UnwrappedType
 ) : InapplicableArgumentDiagnostic()
 
+// supported by FE but not supported by BE now
+class CallableReferencesDefaultArgumentUsed(
+    val argument: CallableReferenceKotlinCallArgument,
+    val candidate: CallableDescriptor,
+    val defaultsCount: Int
+) : KotlinCallDiagnostic(IMPOSSIBLE_TO_GENERATE) {
+    override fun report(reporter: DiagnosticReporter) = reporter.onCallArgument(argument, this)
+}
+
 class NotCallableMemberReference(
         override val argument: CallableReferenceKotlinCallArgument,
         val candidate: CallableDescriptor
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/OverloadingConflictResolver.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/OverloadingConflictResolver.kt
index afcb08f68cb..068f0753c28 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/OverloadingConflictResolver.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/OverloadingConflictResolver.kt
@@ -38,7 +38,7 @@ open class OverloadingConflictResolver<C : Any>(
         private val getResultingDescriptor: (C) -> CallableDescriptor,
         private val createEmptyConstraintSystem: () -> SimpleConstraintSystem,
         private val createFlatSignature: (C) -> FlatSignature<C>,
-        private val getVariableCandidates: (C) -> C?, // vor variable WithInvoke
+        private val getVariableCandidates: (C) -> C?, // for variable WithInvoke
         private val isFromSources: (CallableDescriptor) -> Boolean
 ) {
 
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/InvokeProcessors.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/InvokeProcessors.kt
index 2ac6288728b..ac68d186966 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/InvokeProcessors.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/InvokeProcessors.kt
@@ -17,8 +17,6 @@
 package org.jetbrains.kotlin.resolve.calls.tower
 
 import org.jetbrains.kotlin.builtins.isBuiltinExtensionFunctionalType
-import org.jetbrains.kotlin.descriptors.FunctionDescriptor
-import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.calls.tasks.ExplicitReceiverKind
 import org.jetbrains.kotlin.resolve.calls.tasks.createSynthesizedInvokes
@@ -182,7 +180,7 @@ fun <C : Candidate> createCallTowerProcessorForExplicitInvoke(
             usualInvoke
         }
         else {
-            CompositeScopeTowerProcessor(
+            PrioritizedCompositeScopeTowerProcessor(
                     usualInvoke,
                     InvokeExtensionScopeTowerProcessor(functionContext, invokeExtensionDescriptor, explicitReceiver = null)
             )
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/ScopeTowerProcessors.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/ScopeTowerProcessors.kt
index ab90436e1be..bc633033abd 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/ScopeTowerProcessors.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/ScopeTowerProcessors.kt
@@ -32,14 +32,14 @@ class KnownResultProcessor<out C>(
 }
 
 // use this if processors priority is important
-class CompositeScopeTowerProcessor<out C>(
+class PrioritizedCompositeScopeTowerProcessor<out C>(
         vararg val processors: ScopeTowerProcessor<C>
 ) : ScopeTowerProcessor<C> {
     override fun process(data: TowerData): List<Collection<C>> = processors.flatMap { it.process(data) }
 }
 
 // use this if all processors has same priority
-class CompositeSimpleScopeTowerProcessor<C : Candidate>(
+class SamePriorityCompositeScopeTowerProcessor<out C>(
         private vararg val processors: SimpleScopeTowerProcessor<C>
 ): SimpleScopeTowerProcessor<C> {
     override fun simpleProcess(data: TowerData): Collection<C> = processors.flatMap { it.simpleProcess(data) }
@@ -192,7 +192,7 @@ private fun <C : Candidate> createSimpleProcessor(
 
     if (classValueReceiver && explicitReceiver is QualifierReceiver) {
         val classValue = explicitReceiver.classValueReceiverWithSmartCastInfo ?: return withoutClassValueProcessor
-        return CompositeScopeTowerProcessor(
+        return PrioritizedCompositeScopeTowerProcessor(
                 withoutClassValueProcessor,
                 ExplicitReceiverScopeTowerProcessor(scopeTower, context, classValue, collectCandidates)
         )
@@ -200,11 +200,14 @@ private fun <C : Candidate> createSimpleProcessor(
     return withoutClassValueProcessor
 }
 
-fun <C : Candidate> createCallableReferenceProcessor(scopeTower: ImplicitScopeTower, name: Name, context: CandidateFactory<C>,
-                                                     explicitReceiver: DetailedReceiver?): SimpleScopeTowerProcessor<C> {
+fun <C : Candidate> createCallableReferenceProcessor(
+        scopeTower: ImplicitScopeTower,
+        name: Name, context: CandidateFactory<C>,
+        explicitReceiver: DetailedReceiver?
+): SimpleScopeTowerProcessor<C> {
     val variable = createSimpleProcessorWithoutClassValueReceiver(scopeTower, context, explicitReceiver) { getVariables(name, it) }
     val function = createSimpleProcessorWithoutClassValueReceiver(scopeTower, context, explicitReceiver) { getFunctions(name, it) }
-    return CompositeSimpleScopeTowerProcessor(variable, function)
+    return SamePriorityCompositeScopeTowerProcessor(variable, function)
 }
 
 fun <C : Candidate> createVariableProcessor(scopeTower: ImplicitScopeTower, name: Name,
@@ -213,7 +216,7 @@ fun <C : Candidate> createVariableProcessor(scopeTower: ImplicitScopeTower, name
 
 fun <C : Candidate> createVariableAndObjectProcessor(scopeTower: ImplicitScopeTower, name: Name,
                                                      context: CandidateFactory<C>, explicitReceiver: DetailedReceiver?, classValueReceiver: Boolean = true
-) = CompositeScopeTowerProcessor(
+) = PrioritizedCompositeScopeTowerProcessor(
         createVariableProcessor(scopeTower, name, context, explicitReceiver),
         createSimpleProcessor(scopeTower, context, explicitReceiver, classValueReceiver) { getObjects(name, it) }
 )
@@ -229,7 +232,7 @@ fun <С: Candidate> createFunctionProcessor(
         simpleContext: CandidateFactory<С>,
         factoryProviderForInvoke: CandidateFactoryProviderForInvoke<С>,
         explicitReceiver: DetailedReceiver?
-): CompositeScopeTowerProcessor<С> {
+): PrioritizedCompositeScopeTowerProcessor<С> {
 
     // a.foo() -- simple function call
     val simpleFunction = createSimpleFunctionProcessor(scopeTower, name, simpleContext, explicitReceiver)
@@ -242,7 +245,7 @@ fun <С: Candidate> createFunctionProcessor(
         InvokeExtensionTowerProcessor(scopeTower, name, factoryProviderForInvoke, it)
     }
 
-    return CompositeScopeTowerProcessor(simpleFunction, invokeProcessor, invokeExtensionProcessor)
+    return PrioritizedCompositeScopeTowerProcessor(simpleFunction, invokeProcessor, invokeExtensionProcessor)
 }
 
 
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/types/TypeApproximator.kt b/compiler/resolution/src/org/jetbrains/kotlin/types/TypeApproximator.kt
index 30f52eb8adf..61bce7f1da4 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/types/TypeApproximator.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/types/TypeApproximator.kt
@@ -132,9 +132,9 @@ class TypeApproximator {
 
                 if (conf.flexible) {
                     /**
-                     * Let inputTypes = L_1..U_1; resultType = L_2..U_2
-                     * We should create resultType such as inputTypes <: resultType.
-                     * It means that if A <: inputTypes, then A <: U_1. And, because inputTypes <: resultType,
+                     * Let inputType = L_1..U_1; resultType = L_2..U_2
+                     * We should create resultType such as inputType <: resultType.
+                     * It means that if A <: inputType, then A <: U_1. And, because inputType <: resultType,
                      * A <: resultType => A <: U_2. I.e. for every type A such A <: U_1, A <: U_2 => U_1 <: U_2.
                      *
                      * Similar for L_1 <: L_2: Let B : resultType <: B. L_2 <: B and L_1 <: B.
@@ -147,7 +147,7 @@ class TypeApproximator {
 
                     /**
                      * If C <: L..U then C <: L.
-                     * inputTypes.lower <: lowerResult => inputTypes.lower <: lowerResult?.lowerIfFlexible()
+                     * inputType.lower <: lowerResult => inputType.lower <: lowerResult?.lowerIfFlexible()
                      * i.e. this type is correct. We use this type, because this type more flexible.
                      *
                      * If U_1 <: U_2.lower .. U_2.upper, then we know only that U_1 <: U_2.upper.
diff --git a/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java b/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
index 23266871a5a..a5f414e7310 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
+++ b/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
@@ -277,8 +277,6 @@ public abstract class KotlinBuiltIns {
 
         public final FqNameUnsafe functionSupertype = fqNameUnsafe("Function");
 
-
-
         public final FqName throwable = fqName("Throwable");
         public final FqName comparable = fqName("Comparable");