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    CWG Issue 671</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="671"></A><H4>671.
  
Explicit conversion from a scoped enumeration type to integral type
</H4>
<B>Section: </B>7.6.1.9&#160; [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD1
 &#160;&#160;&#160;

 <B>Submitter: </B>Daveed Vandevoorde
 &#160;&#160;&#160;

 <B>Date: </B>22 December 2007<BR>


<P>[Voted into the WP at the September, 2008 meeting.]</P>

<P>There appears to be no provision in the Standard for explicit
conversion of a value of a scoped enumeration type to an integral
type, even though the inverse conversion is permitted.  That is,</P>

<PRE>
    enum class E { e };
    static_cast&lt;E&gt;(0);       //<SPAN CLASS="cmnt"> #1: OK</SPAN>
    static_cast&lt;int&gt;(E::e);  //<SPAN CLASS="cmnt"> #2: error</SPAN>
</PRE>

<P>This is because values of scope enumeration types (intentionally)
cannot be implicitly converted to integral types (7.3.7 [<A href="https://wg21.link/conv.prom">conv.prom</A>]
and 7.3.9 [<A href="https://wg21.link/conv.integral">conv.integral</A>]) and 7.6.1.9 [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>] was not
updated to permit #2, although #1 is covered by paragraph 8.</P>

<P><B>Proposed resolution (June, 2008):</B></P>

<P>Add the following as a new paragraph following 7.6.1.9 [<A href="https://wg21.link/expr.static.cast#8">expr.static.cast</A>] paragraph 8:</P>

<BLOCKQUOTE>

A value of a scoped enumeration type (9.8.1 [<A href="https://wg21.link/dcl.enum">dcl.enum</A>]) can be
explicitly converted to an integral type.  The value is unchanged if
the original value can be represented by the specified
type. Otherwise, the resulting value is unspecified.

</BLOCKQUOTE>

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