C#: Add support for synthetic fields in MaD for C#.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll

@@ -3075,6 +3075,7 @@ ContentApprox getContentApprox(Content c) {
  * ensuring that they are visible to the taint tracking / data flow library.
  */
 private module SyntheticFields {
+  private import semmle.code.csharp.dataflow.internal.ExternalFlow
   private import semmle.code.csharp.frameworks.system.threading.Tasks
   private import semmle.code.csharp.frameworks.system.runtime.CompilerServices
 }

csharp/ql/lib/semmle/code/csharp/dataflow/internal/ExternalFlow.qll

@@ -431,6 +431,17 @@ Declaration interpretElement(
   )
 }
 
+private predicate parseSynthField(AccessPathToken c, string name) {
+  c.getName() = "SyntheticField" and name = c.getAnArgument()
+}
+
+/**
+ * An adapter class for adding synthetic fields from MaD.
+ */
+private class SyntheticFieldAdapter extends SyntheticField {
+  SyntheticFieldAdapter() { parseSynthField(_, this) }
+}
+
 cached
 private module Cached {
   /**