[NI] Extract InferenceStepResolver into a separate component

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

@@ -20,14 +20,10 @@ import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilder
-import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintInjector
+import org.jetbrains.kotlin.resolve.calls.inference.components.*
-import org.jetbrains.kotlin.resolve.calls.inference.components.FixationOrderCalculator
-import org.jetbrains.kotlin.resolve.calls.inference.components.NewTypeSubstitutor
-import org.jetbrains.kotlin.resolve.calls.inference.components.ResultTypeResolver
 import org.jetbrains.kotlin.resolve.calls.inference.model.ExpectedTypeConstraintPosition
 import org.jetbrains.kotlin.resolve.calls.inference.model.LambdaArgumentConstraintPosition
 import org.jetbrains.kotlin.resolve.calls.inference.model.NewTypeVariable
-import org.jetbrains.kotlin.resolve.calls.inference.model.NotEnoughInformationForTypeParameter
 import org.jetbrains.kotlin.resolve.calls.inference.returnTypeOrNothing
 import org.jetbrains.kotlin.resolve.calls.inference.substituteAndApproximateCapturedTypes
 import org.jetbrains.kotlin.resolve.calls.model.*
@@ -41,9 +37,9 @@ import org.jetbrains.kotlin.types.typeUtil.builtIns
 import org.jetbrains.kotlin.types.typeUtil.contains
 
 class KotlinCallCompleter(
-        private val resultTypeResolver: ResultTypeResolver,
         private val fixationOrderCalculator: FixationOrderCalculator,
-        private val additionalDiagnosticReporter: AdditionalDiagnosticReporter
+        private val additionalDiagnosticReporter: AdditionalDiagnosticReporter,
+        private val inferenceStepResolver: InferenceStepResolver
 ) {
     interface Context {
         val innerCalls: List<ResolvedKotlinCall.OnlyResolvedKotlinCall>
@@ -194,19 +190,7 @@ class KotlinCallCompleter(
         }
 
         val completionOrder = fixationOrderCalculator.computeCompletionOrder(c.asFixationOrderCalculatorContext(), descriptorWithFreshTypes.returnTypeOrNothing)
-        for ((variableWithConstraints, direction) in completionOrder) {
+        return inferenceStepResolver.resolveVariables(c, completionOrder)
-            if (c.hasContradiction) return true
-            val variable = variableWithConstraints.typeVariable
-
-            val resultType = resultTypeResolver.findResultType(c.asResultTypeResolverContext(), variableWithConstraints, direction)
-            if (resultType == null) {
-                c.addError(NotEnoughInformationForTypeParameter(variable))
-                break
-            }
-            c.fixVariable(variable, resultType)
-            return false
-        }
-        return true
     }
 
     private fun analyzeLambda(c: Context, resolutionCallbacks: KotlinResolutionCallbacks, lambda: PostponedLambdaArgument) {

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

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.resolve.calls.inference.components
+
+import org.jetbrains.kotlin.resolve.calls.components.KotlinCallCompleter
+import org.jetbrains.kotlin.resolve.calls.inference.model.NotEnoughInformationForTypeParameter
+
+class InferenceStepResolver(
+        private val resultTypeResolver: ResultTypeResolver
+) {
+    /**
+     * Resolves one or more of the `variables`.
+     * Returns `true` if type variable resolution should stop.
+     */
+    fun resolveVariables(c: KotlinCallCompleter.Context, variables: List<FixationOrderCalculator.NodeWithDirection>): Boolean {
+        for ((variableWithConstraints, direction) in variables) {
+            if (c.hasContradiction) return true
+            val variable = variableWithConstraints.typeVariable
+            val resultType = resultTypeResolver.findResultType(c.asResultTypeResolverContext(), variableWithConstraints, direction)
+            if (resultType == null) {
+                c.addError(NotEnoughInformationForTypeParameter(variable))
+                break
+            }
+            c.fixVariable(variable, resultType)
+            return false
+        }
+        return true
+    }
+}