CPP: Add test case.

geoffw0 · geoffw0 · commit 73b186a6952f · 2018-11-07T13:34:42.000Z
diff --git a/cpp/ql/test/query-tests/Likely Bugs/Likely Typos/ExprHasNoEffect/ExprHasNoEffect.expected b/cpp/ql/test/query-tests/Likely Bugs/Likely Typos/ExprHasNoEffect/ExprHasNoEffect.expected
@@ -1,5 +1,7 @@
 | preproc.c:89:2:89:4 | call to fn4 | This expression has no effect (because $@ has no external side effects). | preproc.c:33:5:33:7 | fn4 | fn4 |
 | preproc.c:94:2:94:4 | call to fn9 | This expression has no effect (because $@ has no external side effects). | preproc.c:78:5:78:7 | fn9 | fn9 |
+| template.cpp:4:3:4:3 | call to operator++ | This expression has no effect (because $@ has no external side effects). | template.cpp:9:10:9:19 | operator++ | operator++ |
+| template.cpp:19:3:19:3 | call to operator++ | This expression has no effect (because $@ has no external side effects). | template.cpp:9:10:9:19 | operator++ | operator++ |
 | test.c:7:5:7:5 | 0 | This expression has no effect. | test.c:7:5:7:5 | 0 |  |
 | test.c:9:8:9:8 | 1 | This expression has no effect. | test.c:9:8:9:8 | 1 |  |
 | test.c:9:11:9:11 | 2 | This expression has no effect. | test.c:9:11:9:11 | 2 |  |
diff --git a/cpp/ql/test/query-tests/Likely Bugs/Likely Typos/ExprHasNoEffect/template.cpp b/cpp/ql/test/query-tests/Likely Bugs/Likely Typos/ExprHasNoEffect/template.cpp
@@ -0,0 +1,22 @@
+
+template<class T>
+void Increment(T &t) {
+	t++; // GOOD (sometimes has an effect) [FALSE POSITIVE]
+}
+
+class Nothing {
+public:
+	Nothing operator++(int) {
+		return *this; // do nothing
+	}
+};
+
+void myTemplateTest() {
+	int i = 0;
+	Nothing n;
+
+	i++; // GOOD (always has an effect)
+	n++; // BAD (never has an effect)
+	Increment(i);
+	Increment(n);
+}
