[clang-tools-extra] [clang-tidy][performance-unnecessary-value-param] Avoid in coroutines (PR #140912)

[Dmitry Polukhin via cfe-commits]

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@@ -0,0 +1,81 @@
+// RUN: %check_clang_tidy -std=c++20-or-later %s performance-unnecessary-value-param %t -- -fix-errors
+
+namespace std {
+
+template <typename R, typename...> struct coroutine_traits {
+  using promise_type = typename R::promise_type;
+};
+
+template <typename Promise = void> struct coroutine_handle;
+
+template <> struct coroutine_handle<void> {
+  static coroutine_handle from_address(void *addr) noexcept {
+    coroutine_handle me;
+    me.ptr = addr;
+    return me;
+  }
+  void operator()() { resume(); }
+  void *address() const noexcept { return ptr; }
+  void resume() const {  }
+  void destroy() const { }
+  bool done() const { return true; }
+  coroutine_handle &operator=(decltype(nullptr)) {
+    ptr = nullptr;
+    return *this;
+  }
+  coroutine_handle(decltype(nullptr)) : ptr(nullptr) {}
+  coroutine_handle() : ptr(nullptr) {}
+  //  void reset() { ptr = nullptr; } // add to P0057?
+  explicit operator bool() const { return ptr; }
+
+protected:
+  void *ptr;
+};
+
+template <typename Promise> struct coroutine_handle : coroutine_handle<> {
+  using coroutine_handle<>::operator=;
+
+  static coroutine_handle from_address(void *addr) noexcept {
+    coroutine_handle me;
+    me.ptr = addr;
+    return me;
+  }
+
+  Promise &promise() const {
+    return *reinterpret_cast<Promise *>(
+        __builtin_coro_promise(ptr, alignof(Promise), false));
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dmpolukhin wrote:

Yep, it is better example than used from clang-tools-extra/test/clang-tidy/checkers/misc/coroutine-hostile-raii.cpp

https://github.com/llvm/llvm-project/pull/140912