C++: Remove extra type check in AV Rule 82

These type checks were overlapping with `assignOperatorWithWrongType` is
are no longer needed now that `assignOperatorWithWrongType` is improved.
They were causing FPs and misleading error messages on uninstantiated
templates.

Author: jbj

cpp/ql/src/jsf/4.10 Classes/AV Rule 82.ql

@@ -51,7 +51,6 @@ predicate dereferenceThis(Expr e) {
  * This includes functions whose body is not in the database.
  */
 predicate returnsPointerThis(Function f) {
-  f.getType().getUnspecifiedType() instanceof PointerType and
   forall(ReturnStmt s | s.getEnclosingFunction() = f and reachable(s) |
     // `return this`
     pointerThis(s.getExpr())
@@ -64,7 +63,6 @@ predicate returnsPointerThis(Function f) {
  * database.
  */
 predicate returnsDereferenceThis(Function f) {
-  f.getType().getUnspecifiedType() instanceof ReferenceType and
   forall(ReturnStmt s | s.getEnclosingFunction() = f and reachable(s) |
     // `return *this`
     dereferenceThis(s.getExpr())

cpp/ql/test/query-tests/jsf/4.10 Classes/AV Rule 82/AV Rule 82.cpp

@@ -189,7 +189,7 @@ struct second {
 
 struct TemplatedAssignmentGood {
   template<typename T>
-  typename second<T, TemplatedAssignmentGood &>::type operator=(T val) { // GOOD [FALSE POSITIVE]
+  typename second<T, TemplatedAssignmentGood &>::type operator=(T val) { // GOOD
     return *this;
   }
 };

cpp/ql/test/query-tests/jsf/4.10 Classes/AV Rule 82/AV Rule 82.expected

@@ -2,6 +2,4 @@
 | AV Rule 82.cpp:24:8:24:16 | operator= | Assignment operator in class Bad2 should have return type Bad2&. Otherwise a copy is created at each call. |
 | AV Rule 82.cpp:63:29:63:29 | operator= | Assignment operator in class TemplateReturnAssignment<int> does not return a reference to *this. |
 | AV Rule 82.cpp:63:29:63:37 | operator= | Assignment operator in class TemplateReturnAssignment<T> does not return a reference to *this. |
-| AV Rule 82.cpp:192:55:192:63 | operator= | Assignment operator in class TemplatedAssignmentGood does not return a reference to *this. |
 | AV Rule 82.cpp:199:52:199:52 | operator= | Assignment operator in class TemplatedAssignmentBad should have return type TemplatedAssignmentBad&. Otherwise a copy is created at each call. |
-| AV Rule 82.cpp:199:52:199:60 | operator= | Assignment operator in class TemplatedAssignmentBad does not return a reference to *this. |