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CWG3003 Naming a deducible template for class template argument deduction #2443
Description
The core language specification is clear that dependent names cannot designate templates subject to class template argument deduction, thus excluding the names of template template parameters.
However, https://wg21.link/range.utility.conv.to#4 relies on such a non-existing facility.
CWG3003 seeks to add a note to highlight the status quo of the core language specification.
LWG4381 asks for removal of that unimplementable feature.
If (L)EWG wishes to add a feature to the core language that makes https://wg21.link/range.utility.conv.to#4 valid (possibly limited to situations similar to the first example in CWG3003, excluding the second example), a paper would be needed.
Activity
jfbastien commentedon Sep 28, 2025
Discussed with chairs, LEWG will see first if they need it, and ask EWG for it if so.
je4d commentedon Nov 8, 2025
EWG discussed this in Kona on Friday afternoon along with the proposed fixes in #2467 and #2469, and took the following poll:
CWG3003: EWG wants to keep ranges::to as currently specified, with the understanding that specification is incomplete for CTAD in template parameters, to be fixed later
consensus.
jensmaurer commentedon Mar 25, 2026
CWG in Croydon: P3865R2 is ready for Saturday's straw polls. No action from LEWG needed.