[clang-tools-extra] [clang-tidy] Fix false positive in bugprone-use-after-move with std::forward on derived classes (PR #199905)

[Baranov Victor via cfe-commits]

================
@@ -1814,3 +1814,46 @@ namespace GH62206 {
     (d) = b; // Should not warn
   }
 } // namespace GH62206
+
+namespace GH63202 {
+
+struct Person {
+  std::string name;
+  Person() = default;
+  Person(Person&&) = default;
+  Person& operator=(Person&&) = default;
+};
+
+struct SpecialPerson : Person {
+  std::string surname;
+
+  // Valid: partial move
+  SpecialPerson(SpecialPerson&& sp)
+    : Person(std::move(sp)), surname(std::move(sp.surname)) {}
+
+  // Valid: partial forward — case fixed by this patch
+  SpecialPerson(SpecialPerson&& sp, int)
+    : Person(std::forward<Person>(sp)), surname(std::move(sp.surname)) {}
+
+  // Invalid: access base class member after base move
+  SpecialPerson(SpecialPerson&& sp, char)
+    : Person(std::move(sp)), surname(std::move(sp.name))
+    // CHECK-NOTES: [[@LINE-1]]:48: warning: 'sp' used after it was moved [bugprone-use-after-move]
+    // CHECK-NOTES: [[@LINE-2]]:7: note: move occurred here
+  {}
+};
+
+void invalidFullMove(SpecialPerson&& sp) {
+  SpecialPerson other(std::move(sp));
+  sp.surname = "1";
+  // CHECK-NOTES: [[@LINE-1]]:3: warning: 'sp' used after it was moved [bugprone-use-after-move]
+  // CHECK-NOTES: [[@LINE-3]]:17: note: move occurred here
+}
+
+void invalidFullForward(SpecialPerson&& sp) {
+  SpecialPerson other(std::forward<SpecialPerson>(sp));
+  sp.surname = "1";
+  // CHECK-NOTES: [[@LINE-1]]:3: warning: 'sp' used after it was forwarded [bugprone-use-after-move]
+  // CHECK-NOTES: [[@LINE-3]]:17: note: forward occurred here
+}
----------------
vbvictor wrote:

Please add tests in template context, like

```cpp
template <typename T>                                                                                               
void partialForwardTemplate(T&& sp) {...}
```

https://github.com/llvm/llvm-project/pull/199905