[llvm] [ADT] Add a missing call to a unique_function destructor after move (PR #98747)

[David Blaikie via llvm-commits]

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@@ -310,4 +310,25 @@ class Incomplete {};
 Incomplete incompleteFunction() { return {}; }
 const Incomplete incompleteFunctionConst() { return {}; }
 
+// Check that the moved-from captured state is properly destroyed during
+// move construction/assignment.
+TEST(UniqueFunctionTest, MovedFromStateIsDestroyedCorrectly) {
+  static int NumOfMovesCalled = 0;
+  static int NumOfDestructorsCalled = 0;
+  struct State {
+    State() = default;
+    State(const State &) = delete;
+    State(State &&) { ++NumOfMovesCalled; }
+    State &operator=(const State &) = delete;
+    State &operator=(State &&Rhs) { return *new (this) State{std::move(Rhs)}; }
+    ~State() { ++NumOfDestructorsCalled; }
+  };
+  {
+    unique_function<void()> CapturingFunction{[state = State{}] {}};
+    unique_function<void()> CapturingFunctionMoved{
+        std::move(CapturingFunction)};
+  }
+  EXPECT_EQ(NumOfDestructorsCalled, 1 + NumOfMovesCalled);
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dwblaikie wrote:

Might be ore obvious/clear to have the default ctor count too - maybe count all the ctor calls together, then check that the dtor calls == ctor calls. 

But also, might be worth checking - I think we have a reusable special member counting type utility used in other tests that could be reused here? llvm/unittests/ADT/CountCopyAndMove.h - though, admittedly, we haven't been great about using that everywhere, and various data structure tests certainly have their own versions, but maybe we can try to stem the tide of more of them?

https://github.com/llvm/llvm-project/pull/98747