Introduce TraversingContext

Author: sergeypospelov

utbot-framework/src/main/kotlin/org/utbot/engine/TraversalContext.kt

@@ -0,0 +1,30 @@
+package org.utbot.engine
+
+/**
+ * Represents a mutable _Context_ during the [ExecutionState] traversing. This _Context_ consists of all mutable and
+ * immutable properties and fields which are created and updated during analysis of **one** Jimple instruction.
+ *
+ * Traverser functions should be implemented as an extension functions with [TraversalContext] as a receiver.
+ *
+ * TODO: extend this class with other properties, such as [Environment], which is [Traverser] mutable property now.
+ */
+class TraversalContext {
+    // TODO: move properties from [UtBotSymbolicEngine] here
+
+
+    // TODO: Q: maybe it's better to pass stateConsumer as an argument to constructor?
+    private val states = mutableListOf<ExecutionState>()
+
+    /**
+     * Offers new [ExecutionState] which can be obtained later with [nextStates].
+     */
+    fun offerState(state: ExecutionState) {
+        states.add(state)
+    }
+
+    /**
+     * New states from traversal.
+     */
+    val nextStates: Collection<ExecutionState>
+        get() = states
+}