[all-commits] [llvm/llvm-project] 64216b: [Sema] -Wpointer-bool-conversion: suppress lambda ...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 64216ba1e427fab1ee38ef9492d3fbca907606b9
      https://github.com/llvm/llvm-project/commit/64216ba1e427fab1ee38ef9492d3fbca907606b9
  Author: Fangrui Song <i at maskray.me>
  Date:   2024-03-01 (Fri, 01 Mar 2024)

  Changed paths:
    M clang/lib/Sema/SemaChecking.cpp
    M clang/test/SemaCXX/warn-bool-conversion.cpp

  Log Message:
  -----------
  [Sema] -Wpointer-bool-conversion: suppress lambda function pointer conversion diagnostic during instantiation (#83497)

I have seen two internal pieces of code that uses a template type
parameter to accept any callable type (function pointer, std::function,
closure type, etc). The diagnostic added in #83152 would require
adaptation to the template, which is difficult and also seems
unnecessary. Example:

```cpp
template <typename... Ts>
static bool IsFalse(const Ts&...) { return false; }

template <typename T, typename... Ts,
          typename = typename std::enable_if<std::is_constructible<bool, const T&>::value>::type>
static bool IsFalse(const T& p, const Ts&...) {
  return p ? false : true;
}

template <typename... Args>
void Init(Args&&... args) {
  if (IsFalse(absl::implicit_cast<const typename std::decay<Args>::type&>(
              args)...)) {
    // A callable object convertible to false is either a null pointer or a
    // null functor (e.g., a default-constructed std::function).
    empty_ = true;
  } else {
    empty_ = false;
    new (&factory_) Factory(std::forward<Args>(args)...);
  }
}
```



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