Extract InvocationKind class into separate file

compiler/resolution/src/org/jetbrains/kotlin/contracts/description/Effects.kt

@@ -56,14 +56,4 @@ class ReturnsEffectDeclaration(val value: ConstantReference) : EffectDeclaration
 class CallsEffectDeclaration(val variableReference: VariableReference, val kind: InvocationKind) : EffectDeclaration {
     override fun <R, D> accept(contractDescriptionVisitor: ContractDescriptionVisitor<R, D>, data: D): R =
         contractDescriptionVisitor.visitCallsEffectDeclaration(this, data)
-}
+}
-
-enum class InvocationKind {
-    AT_MOST_ONCE,
-    EXACTLY_ONCE,
-    AT_LEAST_ONCE,
-    UNKNOWN
-}
-
-fun InvocationKind.isDefinitelyVisited(): Boolean = this == InvocationKind.EXACTLY_ONCE || this == InvocationKind.AT_LEAST_ONCE
-fun InvocationKind.canBeRevisited(): Boolean = this == InvocationKind.UNKNOWN || this == InvocationKind.AT_LEAST_ONCE

compiler/resolution/src/org/jetbrains/kotlin/contracts/description/InvocationKind.kt

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2010-2018 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.contracts.description
+
+enum class InvocationKind {
+    AT_MOST_ONCE,
+    EXACTLY_ONCE,
+    AT_LEAST_ONCE,
+    UNKNOWN
+}
+
+fun InvocationKind.isDefinitelyVisited(): Boolean = this == InvocationKind.EXACTLY_ONCE || this == InvocationKind.AT_LEAST_ONCE
+fun InvocationKind.canBeRevisited(): Boolean = this == InvocationKind.UNKNOWN || this == InvocationKind.AT_LEAST_ONCE
+