C++: test for resolving specialisations dependent on template aliases

cpp/ql/test/library-tests/templates/dependent_template_alias/test.cpp

@@ -0,0 +1,37 @@
+
+template <typename>
+using Z = int;
+
+template <typename T, typename U = int>
+struct Thing {
+  int x;
+};
+
+template <typename T>
+struct Thing<T, Z<typename T::Undefined>> {
+  int y;
+};
+
+// Note that float::Undefined is an error, so this should match the primary
+// template, not the partial specialization.
+Thing<float> thing_float;
+
+void f() {
+  // If we incorrectly matched the partial specialization, this write to x would
+  // be an error.
+  thing_float.x = 1;
+}
+
+// Now, a type that actually does define Undefined
+struct S {
+  using Undefined = int;
+};
+
+// S::Undefined is okay, so this should match the partial specialization.
+Thing<S> thing_s;
+
+void g() {
+  // If we incorrectly matched the primary template, this write to y would be an
+  // error.
+  thing_s.y = 1;
+}

cpp/ql/test/library-tests/templates/dependent_template_alias/test.expected

@@ -0,0 +1,2 @@
+| test.cpp:17:14:17:24 | thing_float | test.cpp:6:8:6:12 | Thing<float, int> | test.cpp:7:7:7:7 | x |
+| test.cpp:31:10:31:16 | thing_s | test.cpp:11:8:11:41 | Thing<S, int> | test.cpp:12:7:12:7 | y |

cpp/ql/test/library-tests/templates/dependent_template_alias/test.ql

@@ -0,0 +1,6 @@
+import cpp
+
+from Variable v, Class c
+where c = v.getType()
+  and v.getFile().getBaseName() = "test.cpp"
+select v, c, c.getAMemberVariable()