C#: Fix issue with summary tests, such that the output is compatiable with flow summary interpreter.

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

@@ -357,9 +357,14 @@ private class UnboundValueOrRefType extends ValueOrRefType {
   }
 }
 
-private class UnboundCallable extends Callable {
+/** An unbound callable. */
+class UnboundCallable extends Callable {
   UnboundCallable() { this.isUnboundDeclaration() }
 
+  /**
+   * Holds if this unbound callable overrides or implements (transitively)
+   * `that` unbound callable.
+   */
   predicate overridesOrImplementsUnbound(UnboundCallable that) {
     exists(Callable c |
       this.(Virtualizable).overridesOrImplementsOrEquals(c) or

csharp/ql/test/library-tests/dataflow/library/FlowSummariesFiltered.ql

@@ -1,4 +1,5 @@
 import shared.FlowSummaries
+private import semmle.code.csharp.dataflow.ExternalFlow
 
 class IncludeFilteredSummarizedCallable extends IncludeSummarizedCallable {
   IncludeFilteredSummarizedCallable() { this instanceof SummarizedCallable }
@@ -14,8 +15,8 @@ class IncludeFilteredSummarizedCallable extends IncludeSummarizedCallable {
     this.propagatesFlow(input, output, preservesValue) and
     not exists(IncludeSummarizedCallable rsc |
       rsc.isBaseCallableOrPrototype() and
-      this.(Virtualizable).overridesOrImplements(rsc) and
-      rsc.propagatesFlow(input, output, preservesValue)
+      rsc.propagatesFlow(input, output, preservesValue) and
+      this.(UnboundCallable).overridesOrImplementsUnbound(rsc)
     )
   }
 }

csharp/ql/test/shared/FlowSummaries.qll

@@ -20,9 +20,11 @@ abstract class IncludeSummarizedCallable extends RelevantSummarizedCallable {
   predicate isBaseCallableOrPrototype() {
     this.getDeclaringType() instanceof Interface
     or
-    this.(Modifiable).isAbstract()
-    or
-    this.getDeclaringType().(Modifiable).isAbstract() and this.(Virtualizable).isVirtual()
+    exists(Modifiable m | m = [this.(Modifiable), this.(Accessor).getDeclaration()] |
+      m.isAbstract()
+      or
+      this.getDeclaringType().(Modifiable).isAbstract() and m.(Virtualizable).isVirtual()
+    )
   }
 
   /** Gets a string representing, whether the summary should apply for all overrides of this. */