C++: Work around issue with ConditionalDeclExpr.

Author: geoffw0

cpp/ql/src/Best Practices/Unused Entities/UnusedLocals.ql

@@ -61,5 +61,6 @@ where
   not exists(Literal l |
     l.getEnclosingFunction() = f and
     not exists(l.getValue())
-  )
+  ) and
+  not any(ConditionDeclExpr cde).getEnclosingFunction() = f
 select v, "Variable " + v.getName() + " is not used"

cpp/ql/test/query-tests/Best Practices/Unused Entities/UnusedLocals/UnusedLocals.expected

@@ -7,7 +7,6 @@
 | code2.cpp:64:7:64:8 | v3 | Variable v3 is not used |
 | code2.cpp:108:11:108:12 | v2 | Variable v2 is not used |
 | code2.cpp:128:9:128:9 | b | Variable b is not used |
-| code2.cpp:141:18:141:18 | b | Variable b is not used |
 | code.c:10:18:10:18 | y | Variable y is not used |
 | code.c:11:18:11:18 | z | Variable z is not used |
 | code.c:18:7:18:7 | x | Variable x is not used |

cpp/ql/test/query-tests/Best Practices/Unused Entities/UnusedLocals/code2.cpp

@@ -138,7 +138,7 @@ int test_lambdas2()
 
 void test_if_initializer()
 {
-	bool a = false, b = true; // GOOD: a, b are both used [FALSE POSITIVE]
+	bool a = false, b = true; // GOOD: a, b are both used
 
 	if (a = b; a)
 	{