CPP: Add a test involving templates.

Author: geoffw0

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/ComparisonPrecedence/ComparisonPrecedence.expected

@@ -1,3 +1,6 @@
+| template.cpp:4:7:4:15 | ... < ... | Check the comparison operator precedence. |
+| template.cpp:4:7:4:15 | ... < ... | Check the comparison operator precedence. |
+| template.cpp:10:7:10:15 | ... < ... | Check the comparison operator precedence. |
 | test.cpp:42:6:42:14 | ... < ... | Check the comparison operator precedence. |
 | test.cpp:43:6:43:14 | ... > ... | Check the comparison operator precedence. |
 | test.cpp:44:6:44:16 | ... <= ... | Check the comparison operator precedence. |

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/ComparisonPrecedence/template.cpp

@@ -0,0 +1,32 @@
+
+template <typename T>
+void templateFunc1(T x, T y, T z) {
+  if (x < y < z) {} // BAD (though dubious as we can imagine other instantiations using an overloaded `operator<`)
+  if (x < y && y < z) {} // GOOD
+};
+
+template <typename T>
+void templateFunc2(T x, T y, T z) {
+  if (x < y < z) {} // GOOD (used with an overloaded `operator<`) [FALSE POSITIVE]
+  if (x < y && y < z) {} // GOOD
+};
+
+struct myStruct {
+  operator bool() {
+    return true;
+  }
+
+  myStruct operator<(myStruct &other) {
+    return other; // non-standard `operator<` behaviour
+  }
+};
+
+int main() {
+  int x = 3;
+  myStruct y;
+ 
+  templateFunc1(x, x, x);
+  templateFunc2(y, y, y);
+
+  return 0;
+}