This page is a snapshot from the LWG issues list, see the Library Active Issues List for more information and the meaning of NAD Concepts status.

### 989. late_check and library

Section: 16 [library] Status: NAD Concepts Submitter: Alisdair Meredith Opened: 2009-02-24 Last modified: 2016-01-28

Priority: Not Prioritized

View other active issues in [library].

View all other issues in [library].

View all issues with NAD Concepts status.

Discussion:

The example in 6.9p2 shows how late_check blocks inhibit concept_map lookup inside a constrained context, and so inhibit concept map adaption by users to meet template requirements.

Do we need some text in clause 17 prohibitting use of late_check in library template definitions unless otherwise documented?

[ Doug adds: ]

> We need something like this, but it should be a more general statement about implementations respecting the concept maps provided by the user. Use of late_check is one way in which implementations can subvert the concept maps provided by the user, but there are other ways as well ("pattern-based" overloading, tricks with "auto" concept maps and defaulted associated type arguments).

[ Batavia (2009-05): ]

> Move to Open, pending proposed wording from Alisdair and/or Doug for further review.

Proposed resolution: