From e6996ea29a496eba1e7143eb14aeef4a8f5ab4cb Mon Sep 17 00:00:00 2001
From: Owen Mansel-Chan <owen-mc@github.com>
Date: Thu, 5 Mar 2026 12:11:25 +0000
Subject: [PATCH] Add model validation for constructor summary models

---
 .../code/csharp/dataflow/internal/ExternalFlow.qll  | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/ExternalFlow.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/ExternalFlow.qll
index edfaae018e9..2f797ac5da0 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/ExternalFlow.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/ExternalFlow.qll
@@ -239,12 +239,23 @@ module ModelValidation {
     )
   }
 
+  string getIncorrectConstructorSummaryOutput() {
+    exists(string namespace, string type, string name, string output |
+      summaryModel(namespace, type, _, name, _, _, _, output, _, _, _) and
+      type = name and
+      output.matches("ReturnValue%") and
+      result =
+        "Constructor model for " + namespace + "." + type +
+          " should use `Argument[this]` in the output, not `ReturnValue`."
+    )
+  }
+
   /** Holds if some row in a MaD flow model appears to contain typos. */
   query predicate invalidModelRow(string msg) {
     msg =
       [
         getInvalidModelSignature(), getInvalidModelInput(), getInvalidModelOutput(),
-        KindVal::getInvalidModelKind()
+        getIncorrectConstructorSummaryOutput(), KindVal::getInvalidModelKind()
       ]
   }
 }