From 03c3ef9528ab60a62fd987de02ea6ff444c227de Mon Sep 17 00:00:00 2001
From: Mathias Vorreiter Pedersen <mathiasvp@github.com>
Date: Tue, 23 Jun 2026 19:47:13 +0100
Subject: [PATCH] C++: Add tests with missing reverse flow.

---
 .../dataflow/external-models/flow.ext.yml     |  5 +++-
 .../dataflow/external-models/sinks.expected   |  2 ++
 .../dataflow/external-models/sources.expected |  2 ++
 .../dataflow/external-models/test.cpp         | 24 +++++++++++++++++++
 4 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/cpp/ql/test/library-tests/dataflow/external-models/flow.ext.yml b/cpp/ql/test/library-tests/dataflow/external-models/flow.ext.yml
index 76d649152bd..92c76ca2566 100644
--- a/cpp/ql/test/library-tests/dataflow/external-models/flow.ext.yml
+++ b/cpp/ql/test/library-tests/dataflow/external-models/flow.ext.yml
@@ -21,4 +21,7 @@ extensions:
       - ["", "", False, "callWithNonTypeTemplate<T>", "(const T &)", "", "Argument[*0]", "ReturnValue", "value", "manual"]
       - ["", "TemplateClass1<T>", False, "templateFunction<U>", "(T,U)", "", "Argument[0]", "ReturnValue", "value", "manual"]
       - ["", "TemplateClass1", True, "templateFunction2<U,V>", "(U,V)", "", "Argument[1]", "ReturnValue", "value", "manual"]
-      - ["", "TemplateClass2<T,U>", True, "function", "(U,T)", "", "Argument[1]", "ReturnValue", "value", "manual"]
\ No newline at end of file
+      - ["", "TemplateClass2<T,U>", True, "function", "(U,T)", "", "Argument[1]", "ReturnValue", "value", "manual"]
+      - ["", "ReverseFlow", True, "get_ptr", "", "", "ReturnValue[*]", "Argument[-1].Field[value]", "value", "manual"]
+      - ["", "MyString", True, "operator[]", "", "", "ReturnValue[*]", "Argument[-1]", "taint", "manual"]
+      - ["", "MyString", True, "operator[]", "", "", "Argument[-1]", "ReturnValue[*]", "taint", "manual"]
\ No newline at end of file
diff --git a/cpp/ql/test/library-tests/dataflow/external-models/sinks.expected b/cpp/ql/test/library-tests/dataflow/external-models/sinks.expected
index 03a0d442c1c..98b0eff8757 100644
--- a/cpp/ql/test/library-tests/dataflow/external-models/sinks.expected
+++ b/cpp/ql/test/library-tests/dataflow/external-models/sinks.expected
@@ -19,3 +19,5 @@
 | test.cpp:149:10:149:10 | z | test-sink |
 | test.cpp:158:10:158:10 | z | test-sink |
 | test.cpp:173:10:173:10 | y | test-sink |
+| test.cpp:190:11:190:11 | x | test-sink |
+| test.cpp:196:11:196:11 | c | test-sink |
diff --git a/cpp/ql/test/library-tests/dataflow/external-models/sources.expected b/cpp/ql/test/library-tests/dataflow/external-models/sources.expected
index 4040cff4fd2..6b6c05e989b 100644
--- a/cpp/ql/test/library-tests/dataflow/external-models/sources.expected
+++ b/cpp/ql/test/library-tests/dataflow/external-models/sources.expected
@@ -13,6 +13,8 @@
 | test.cpp:146:10:146:18 | call to ymlSource | local |
 | test.cpp:155:10:155:18 | call to ymlSource | local |
 | test.cpp:170:10:170:18 | call to ymlSource | local |
+| test.cpp:188:18:188:26 | call to ymlSource | local |
+| test.cpp:194:10:194:20 | call to ymlSource | local |
 | windows.cpp:22:15:22:29 | *call to GetCommandLineA | local |
 | windows.cpp:34:17:34:38 | *call to GetEnvironmentStringsA | local |
 | windows.cpp:39:36:39:38 | GetEnvironmentVariableA output argument | local |
diff --git a/cpp/ql/test/library-tests/dataflow/external-models/test.cpp b/cpp/ql/test/library-tests/dataflow/external-models/test.cpp
index 01bf6cc4093..3d572cd0920 100644
--- a/cpp/ql/test/library-tests/dataflow/external-models/test.cpp
+++ b/cpp/ql/test/library-tests/dataflow/external-models/test.cpp
@@ -171,4 +171,28 @@ void test_class1() {
 	Class1<int> c;
 	auto y = c.templateFunction3<unsigned long>(0UL, x);
 	ymlSink(y); // $ ir
+}
+
+struct ReverseFlow {
+	int value;
+	int& get_ptr();
+};
+
+struct MyString {
+	char& operator[](unsigned);
+};
+
+void test_reverse_flow(unsigned i, unsigned j) {
+	{
+		ReverseFlow rf;
+		rf.get_ptr() = ymlSource();
+		int x = rf.value;
+		ymlSink(x); // $ MISSING: ir
+	}
+	{
+		MyString s;
+		s[i] = ymlSource();
+		char c = s[j];
+		ymlSink(c); // $ MISSING: ir
+	}
 }
\ No newline at end of file