In ["What breaks without implicit `T*`-to-`bool` conversion?"](/blog/2025/10/05/pointer-to-bool-conversion/) (2025-10-05) I wrote that in a proprietary C++17 codebase my audit turned up "one non-`explicit` `operator bool`, and zero bugs." On closer inspection we found that that non-explicit `operator bool` actually was causing a real bug! Consider this hypothetical type that behaves something like `unique_ptr` ([Godbolt](https://godbolt.org/z/EMc96648a)): struct IntPtr { explicit IntPtr() = d...| Arthur O’Dwyer