Swift: Add a LocalFlowSource and FlowSource class.

Author: geoffw0

swift/ql/lib/codeql/swift/dataflow/FlowSources.qll

@@ -5,12 +5,26 @@
 private import ExternalFlow
 private import internal.DataFlowPublic
 
-/** A data flow source of remote user input. */
-abstract class RemoteFlowSource extends Node {
-  /** Gets a string that describes the type of this remote flow source. */
+/**
+ * A data flow source of user input, whether local or remote.
+ */
+abstract class FlowSource extends Node {
+  /** Gets a string that describes the type of this flow source. */
   abstract string getSourceType();
 }
 
+/**
+ * A data flow source of local user input, that is, user input from the same
+ * device as the code is running on.
+ */
+abstract class LocalFlowSource extends FlowSource { }
+
+/**
+ * A data flow source of remote user input. In this context, 'remote' means
+ * either across a network or from another application that is not trusted.
+ */
+abstract class RemoteFlowSource extends FlowSource { }
+
 /**
  * A data flow source of remote user input that is defined through 'models as data'.
  */