[NI] Introduce method to add extra constraints before completion

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/ManyCandidatesResolver.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2000-2018 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.resolve.calls.tower
+
+import org.jetbrains.kotlin.resolve.calls.components.InferenceSession
+import org.jetbrains.kotlin.resolve.calls.model.CallResolutionResult
+
+abstract class ManyCandidatesResolver : InferenceSession {
+    private val partiallyResolvedCalls = arrayListOf<CallResolutionResult>()
+
+    override fun shouldFixTypeVariables(): Boolean {
+        return false
+    }
+
+    override fun addPartiallyResolvedCall(call: CallResolutionResult) {
+        partiallyResolvedCalls.add(call)
+    }
+}

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/InferenceSession.kt

@@ -5,16 +5,19 @@
 
 package org.jetbrains.kotlin.resolve.calls.components
 
+import org.jetbrains.kotlin.resolve.calls.inference.NewConstraintSystem
 import org.jetbrains.kotlin.resolve.calls.model.CallResolutionResult
 
 interface InferenceSession {
     companion object {
         val default = object : InferenceSession {
+            override fun prepareBeforeCompletion(commonSystem: NewConstraintSystem) {}
             override fun shouldFixTypeVariables(): Boolean = false
             override fun addPartiallyResolvedCall(call: CallResolutionResult) {}
         }
     }
 
+    fun prepareBeforeCompletion(commonSystem: NewConstraintSystem)
     fun shouldFixTypeVariables(): Boolean
     fun addPartiallyResolvedCall(call: CallResolutionResult)
 }