I propose adding noexcept as an attribute. It would be used after a function call to a noexcept(false) function. It asserts that, in that context, the function will not throw any exceptions. I also propose that, if a function that only has calls to noexcept functions, or calls with the [[noexcept]] attribute, the compiler must emit a diagnostic (presumably a warning) if the function is noexcept(false).