This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 114a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2024-04-18
[Voted into WP at March, 2010 meeting.]
12.2.4.2 [over.best.ics] paragraph 4 says,
However, when considering the argument of a user-defined conversion function that is a candidate by 12.2.2.4 [over.match.ctor] when invoked for the copying of the temporary in the second step of a class copy-initialization, by 12.2.2.8 [over.match.list] when passing the initializer list as a single argument or when the initializer list has exactly one element and a conversion to some class X or reference to (possibly cv-qualified) X is considered for the first parameter of a constructor of X, or by 12.2.2.5 [over.match.copy], 12.2.2.6 [over.match.conv], or 12.2.2.7 [over.match.ref] in all cases, only standard conversion sequences and ellipsis conversion sequences are allowed.
This is not quite right, as this applies to constructor arguments, not just arguments of user-defined conversion functions. Furthermore, the word “allowed” might be better replaced by something like,
considered (in particular, for the purposes of determining whether the candidate function (that is either a constructor or a conversion function) is viable)
Proposed resolution (October, 2009):
Change 12.2.4.2 [over.best.ics] paragraph 4 as follows:
However, when considering the argument of a constructor or user-defined conversion function that is a candidate by 12.2.2.4 [over.match.ctor] when invoked for the copying of the temporary in the second step of a class copy-initialization, by 12.2.2.8 [over.match.list] when passing the initializer list as a single argument or when the initializer list has exactly one element and a conversion to some class X or reference to (possibly cv-qualified) X is considered for the first parameter of a constructor of X, or by 12.2.2.5 [over.match.copy], 12.2.2.6 [over.match.conv], or 12.2.2.7 [over.match.ref] in all cases, only standard conversion sequences and ellipsis conversion sequences areallowedconsidered.