unified: More precise CFG node for implicit setter arguments

Author: asgerf

unified/ql/lib/codeql/unified/internal/dataflow/DataFlowNode.qll

@@ -379,18 +379,19 @@ class BuilderNode extends TDataFlowNodeStage1 {
       exists(DataFlowCall call, Expr access, boolean isPost |
         this.isImplicitArgument(call, _, isPost)
       |
-        (
-          access = call.asExplicitCall()
-          or
-          access = call.asGetterCall()
-          or
-          access = call.asSetterCall()
-        ) and
+        (access = call.asExplicitCall() or access = call.asGetterCall()) and
         (
           isPost = false and cfgNode.injects(access)
           or
           isPost = true and cfgNode.isAfter(access)
         )
+        or
+        access = call.asSetterCall() and
+        exists(Assignment assignment | isInAssignmentContext(access, assignment) |
+          isPost = false and cfgNode.injects(assignment)
+          or
+          isPost = true and cfgNode.isAfter(assignment)
+        )
       )
     )
   }