diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignatureForResolvedCall.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignatureForResolvedCall.kt
index a9efdd113c6..5a13f1cfd46 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignatureForResolvedCall.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignatureForResolvedCall.kt
@@ -17,7 +17,6 @@
 package org.jetbrains.kotlin.resolve.calls.results
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
-import org.jetbrains.kotlin.descriptors.MemberDescriptor
 import org.jetbrains.kotlin.psi.ValueArgument
 import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl
@@ -26,7 +25,6 @@ import org.jetbrains.kotlin.resolve.calls.model.MutableResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.VariableAsFunctionResolvedCallImpl
 import org.jetbrains.kotlin.resolve.calls.results.FlatSignature.Companion.argumentValueType
-import org.jetbrains.kotlin.resolve.calls.results.FlatSignature.Companion.extensionReceiverTypeOrEmpty
 import org.jetbrains.kotlin.types.KotlinType
 import java.util.*
 
@@ -50,14 +48,7 @@ fun <RC : ResolvedCall<*>> RC.createFlatSignature(): FlatSignature<RC> {
         }
     }
 
-    return FlatSignature(this,
-                         originalDescriptor.typeParameters,
-                         valueParameterTypes = originalDescriptor.extensionReceiverTypeOrEmpty() +
-                                               call.valueArguments.map { valueArgumentToParameterType[it] },
-                         hasExtensionReceiver = originalDescriptor.extensionReceiverParameter != null,
-                         hasVarargs = originalDescriptor.valueParameters.any { it.varargElementType != null },
-                         numDefaults = numDefaults,
-                         isPlatform = originalDescriptor is MemberDescriptor && originalDescriptor.isPlatform)
+    return FlatSignature.create(this, originalDescriptor, numDefaults, call.valueArguments.map { valueArgumentToParameterType[it] })
 }
 
 fun createOverloadingConflictResolver(
@@ -71,4 +62,4 @@ fun createOverloadingConflictResolver(
         MutableResolvedCall<*>::createFlatSignature,
         { (it as? VariableAsFunctionResolvedCallImpl)?.variableCall },
         { DescriptorToSourceUtils.descriptorToDeclaration(it) != null}
-)
\ No newline at end of file
+)
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt
index acce7f91542..ee50dba839d 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt
@@ -36,7 +36,7 @@ interface TypeSpecificityComparator {
     }
 }
 
-class FlatSignature<out T>(
+class FlatSignature<out T> private constructor(
         val origin: T,
         val typeParameters: Collection<TypeParameterDescriptor>,
         val valueParameterTypes: List<KotlinType?>,
@@ -48,20 +48,31 @@ class FlatSignature<out T>(
     val isGeneric = typeParameters.isNotEmpty()
 
     companion object {
-        fun <D : CallableDescriptor> createFromCallableDescriptor(descriptor: D): FlatSignature<D> =
-                FlatSignature(descriptor,
-                              descriptor.typeParameters,
-                              valueParameterTypes = descriptor.extensionReceiverTypeOrEmpty() + descriptor.valueParameters.map { it.argumentValueType },
-                              hasExtensionReceiver = descriptor.extensionReceiverParameter != null,
-                              hasVarargs = descriptor.valueParameters.any { it.varargElementType != null },
-                              numDefaults = 0,
-                              isPlatform = descriptor is MemberDescriptor && descriptor.isPlatform)
+        fun <T> create(
+                origin: T,
+                descriptor: CallableDescriptor,
+                numDefaults: Int,
+                parameterTypes: List<KotlinType?>
+        ): FlatSignature<T> {
+            val extensionReceiverType = descriptor.extensionReceiverParameter?.type
 
-        val ValueParameterDescriptor.argumentValueType: KotlinType
-            get() = varargElementType ?: type
+            return FlatSignature(origin,
+                                 descriptor.typeParameters,
+                                 valueParameterTypes =
+                                    extensionReceiverType.singletonOrEmptyList() + parameterTypes,
+                                 hasExtensionReceiver = extensionReceiverType != null,
+                                 hasVarargs = descriptor.valueParameters.any { it.varargElementType != null },
+                                 numDefaults = numDefaults,
+                                 isPlatform = descriptor is MemberDescriptor && descriptor.isPlatform
+            )
+        }
 
-        fun CallableDescriptor.extensionReceiverTypeOrEmpty() =
-                extensionReceiverParameter?.type.singletonOrEmptyList()
+        fun <D : CallableDescriptor> createFromCallableDescriptor(
+                descriptor: D
+        ): FlatSignature<D> =
+                create(descriptor, descriptor, numDefaults = 0, parameterTypes = descriptor.valueParameters.map { it.argumentValueType })
+
+        val ValueParameterDescriptor.argumentValueType get() = varargElementType ?: type
     }
 }