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CWG3204 [expr.call] Simplify restrictions on arguments for ellipsis parameters #918
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[-][expr.call] Simplify restrictions on arguments for ellipsis parameters[/-][+]CWG3204 [expr.call] Simplify restrictions on arguments for ellipsis parameters[/+]on Jun 25, 2026 There are no expressions of qualified void type.
And now that I'm looking at this again, I think we should lift the restriction on
std::meta::info. Using an ellipsis parameter to create the worst possible implicit conversion sequence in an overload set is a common technique, and saying that the call is ill-formed if the argument has typestd::meta::infomeans the call is ill-formed even in an unevaluated context. Moreover, the restriction does not apply to (what used to be) consteval-only types other thanstd::meta::info. I think these considerations strongly suggest that the restriction was unintentional: it crept in simply because P2996 did not update [expr.call]/12.Reacted by Daniel M. KatzYeah, we certainly didn't mean to constrain
infoin this way. Another point for the strategy of, "If P2996 didn't update the paragraph, there's probably a bug."Reacted by Brian Bi
Full name of submitter: Brian Bi
Issue description: The following wording in [expr.call]/12 is an unnecessarily abstruse way of describing which arguments can be passed to an ellipsis:
Prior to C++26, the only argument type that is not permitted is
void. Since C++26, cvstd::meta::infois also disallowed, but neither Clang nor GCC currently enforces this restriction and it is not clear whether it is intentionally disallowed.