C#: Update the Summary model generator with better support for IEnumerable typed parameters.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/commons/Collections.qll

@@ -66,6 +66,17 @@ class CollectionType extends RefType {
   }
 }
 
+/** An IEnumerable type. */
+class IEnumerableType extends RefType {
+  IEnumerableType() {
+    this.hasQualifiedName("System.Collections", "IEnumerable")
+    or
+    this.(ConstructedType)
+        .getUnboundGeneric()
+        .hasQualifiedName("System.Collections.Generic", "IEnumerable<>")
+  }
+}
+
 /** An object creation that creates an empty collection. */
 class EmptyCollectionCreation extends ObjectCreation {
   EmptyCollectionCreation() {

csharp/ql/src/utils/model-generator/ModelGeneratorUtilsSpecific.qll

@@ -70,9 +70,14 @@ private predicate isPrimitiveTypeUsedForBulkData(Type t) {
   t.getName().regexpMatch("byte|char|Byte|Char")
 }
 
+private predicate isContainerType(Type t) {
+  t instanceof CollectionType or
+  t instanceof IEnumerableType
+}
+
 private string parameterAccess(Parameter p) {
   if
-    p.getType() instanceof CollectionType and
+    isContainerType(p.getType()) and
     not isPrimitiveTypeUsedForBulkData(p.getType().(ArrayType).getElementType())
   then result = "Argument[" + p.getPosition() + "].Element"
   else result = "Argument[" + p.getPosition() + "]"