[This answer of @R. Martinho Fernandes][1] shows, that the safe-bool idiom is apperently deprecated in C++11, as it can be replaced by a simple

    explicit operator bool() const;
according to the standard quote in the answer `&#167;4 [conv] p3`:
&gt;An expression e can be implicitly converted to a type `T` if and only if the declaration `T t=e;` is well-formed, for some invented temporary variable `t` (&#167;8.5). Certain language constructs require that an expression be converted to a Boolean value. An expression `e` appearing in such a context is said to be **contextually converted** to `bool` and **is well-formed if and only if the declaration `bool t(e);` is well-formed**, for some invented temporary variable t (&#167;8.5).

The highlighted part clearly shows the &quot;implicit explicit cast&quot; (called &quot;contextual conversion&quot; in the standard) as @R. Martinho put it.

The &quot;certain language constructs&quot; that require that &quot;implicit explicit cast&quot; seem to be the following:

* `if`, `while`, `for` (`&#167;6.4 [stmt.select] p4`)
* binary logical operators `&amp;&amp;` and `||` (`&#167;5.14 [expr.log.and/or] p1` for both)
* the logical negation operator `!` (`&#167;5.3.1 [expr.unary.op] p9`)
* conditional operator `?:` (`&#167;5.14 [expr.cond] p1`)
* `static_assert` (`&#167;7 [dcl.dcl] p4`)
* `noexcept` (`&#167;15.4 [except.spec] p2`)

Is our assumption in the title correct? I hope we didn&#39;t overlook any potential drawbacks.

  [1]: https://stackoverflow.com/questions/6242296/conversion-function-for-error-checking-considered-good/6242355#6242355

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Is the safe-bool idiom obsolete in C++11?