C++: Add testcase with false positive from github#5318.

Author: MathiasVP

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/AssignWhereCompareMeant/AssignWhereCompareMeant.expected

@@ -19,3 +19,11 @@
 | test.cpp:144:32:144:36 | ... = ... | Use of '=' where '==' may have been intended. |
 | test.cpp:150:32:150:36 | ... = ... | Use of '=' where '==' may have been intended. |
 | test.cpp:153:46:153:50 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:160:7:160:12 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:162:7:162:12 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:163:7:163:12 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:164:7:164:12 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:166:22:166:27 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:168:24:168:29 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:169:23:169:28 | ... = ... | Use of '=' where '==' may have been intended. |
+| test.cpp:171:7:171:12 | ... = ... | Use of '=' where '==' may have been intended. |

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/AssignWhereCompareMeant/test.cpp

@@ -153,3 +153,21 @@ void f3(int x, int y) {
   if((x == 10) || ((z == z) && (x == 1)) && (y = 2)) { // BAD
   }
 }
+
+bool use(int);
+
+void f4(int x, bool b) {
+  if((x = 10) && use(x)) {} // GOOD [FALSE POSITIVE]: This is likely just a short-hand way of writing an assignment
+                            // followed by a boolean check.
+  if((x = 10) && b && use(x)) {} // GOOD [FALSE POSITIVE]: Same reason as above
+  if((x = 10) && use(x) && b) {} // GOOD [FALSE POSITIVE]: Same reason as above
+  if((x = 10) && (use(x) && b)) {} // GOOD [FALSE POSITIVE]: Same reason as above
+
+  if(use(x) && b && (x = 10)) {} // BAD: The assignment is the last thing that happens in the comparison.
+                                 // This doesn't match the usual pattern.
+  if((use(x) && b) && (x = 10)) {} // BAD: Same reason as above
+  if(use(x) && (b && (x = 10))) {} // BAD: Same reason as above
+
+  if((x = 10) || use(x)) {} // BAD: This doesn't follow the usual style of writing an assignment in
+                            // a boolean check.
+}