CPP: Add a simplified test case for ImplicitThisFieldAccess.

Author: geoffw0

cpp/ql/test/library-tests/access/FieldAccess/FieldAccess.cpp

@@ -96,3 +96,22 @@ class MyClass {
 
   int x, y;
 };
+
+class MyHasDestructor1 {
+public:
+  ~MyHasDestructor1() {
+    // ...
+  }
+};
+
+class MyHasDestructor2 {
+public:
+  int x;
+  MyHasDestructor1 v;
+
+  ~MyHasDestructor2() {
+    x++; // PointerFieldAccess, the `this->` is generated rather than implicit.
+
+    // ImplicitThisFieldAccess on call `v`s destructor.
+  }
+};

cpp/ql/test/library-tests/access/FieldAccess/FieldAccess.expected

@@ -24,3 +24,5 @@
 | FieldAccess.cpp:93:18:93:18 | y | ptr |
 | FieldAccess.cpp:94:11:94:11 | y | ptr |
 | FieldAccess.cpp:94:20:94:20 | y | val |
+| FieldAccess.cpp:113:5:113:5 | x | ptr |
+| FieldAccess.cpp:116:3:116:3 | v | this |