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Defect report: integral-to-boolean conversion in converted constant expressions

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Hi,

In both C++98 and C++11, the following code appears to be ill-formed:

   template<bool b>  struct S {};
   S<0>  s;

However, EDG, g++ and clang all accept it. The reason this is ill-formed is
that the non-type template argument is a converted constant expression of type
'bool' (see [temp.arg.nontype]p5), and the second conversion in the implicit
conversion sequence is a boolean conversion, which is not allowed in the
conversion for a converted constant expression (see [expr.const]p3).
Conversions in the other direction (from 'bool' to integer types) are
permitted here, since they're integral promotions.

Suggested resolution: In [expr.const]p3, add "boolean conversions from
integral or unscoped enumeration type other than narrowing conversions" to the
list of conversions allowed in a converted constant expression.

Thanks,
Richard


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Defect report: integral-to-boolean conversion in converted       constant expressions "Richard Smith"<richard@metafoo.co.uk> - 2011-10-19 15:24 -0700
  Re: Defect report: integral-to-boolean conversion in converted      constant expressions Daniel Krügler<daniel.kruegler@googlemail.com> - 2011-10-25 09:59 -0700

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