C#: Implement isVariableCaptureContentSet

Author: hvitved

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

@@ -1158,7 +1158,8 @@ private module Cached {
   cached
   newtype TContentSet =
     TSingletonContent(Content c) { not c instanceof PropertyContent } or
-    TPropertyContentSet(Property p) { p.isUnboundDeclaration() }
+    TPropertyContentSet(Property p) { p.isUnboundDeclaration() } or
+    TVariableCaptureContentSet()
 
   cached
   newtype TContentApprox =
@@ -2952,13 +2953,9 @@ Content getLambdaArgumentContent(LambdaCallKind kind, ArgumentPosition pos) {
   exists(kind)
 }
 
-predicate isLambdaInstanceParameter(ParameterNode p) {
-  exists(DataFlowCallable c, ParameterPosition ppos |
-    lambdaCreation(_, _, c) and
-    isParameterNode(p, c, ppos) and
-    ppos.isDelegateSelf()
-  )
-}
+predicate isLambdaInstanceParameter(ParameterNode p) { p instanceof DelegateSelfReferenceNode }
+
+predicate isVariableCaptureContentSet(ContentSet c) { c.isCapturedVariable() }
 
 private predicate isLocalFunctionCallReceiver(
   LocalFunctionCall call, LocalFunctionAccess receiver, LocalFunction f

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

@@ -323,6 +323,8 @@ class ContentSet extends TContentSet {
    */
   predicate isProperty(Property p) { this = TPropertyContentSet(p) }
 
+  predicate isCapturedVariable() { this = TVariableCaptureContentSet() }
+
   /**
    * Holds if this content set represents the `i`th argument of a delegate call.
    */
@@ -361,6 +363,9 @@ class ContentSet extends TContentSet {
       or
       overridesOrImplementsSourceDecl(p1, p2)
     )
+    or
+    this.isCapturedVariable() and
+    result instanceof CapturedVariableContent
   }
 
   /** Gets a textual representation of this content set. */