Proposed resolution (approved by CWG 2022-10-21):

1. Change in 9.12.5 [dcl.attr.deprecated] paragraph 2 as follows:

   The attribute may be applied to the declaration of a class, a typedef-name, a variable, a non-static data member, a function, a namespace, an enumeration, an enumerator, a concept, or a template specialization.

2. Change in 13.7.9 [temp.concept] paragraph 1 as follows:

   A concept is a template that defines constraints on its template arguments.

   concept-definition:
       concept concept-name attribute-specifier-seqopt = constraint-expression ;
   
   concept-name:
       identifier
   

   A concept-definition declares a concept. Its identifier becomes a concept-name referring to that concept within its scope. The optional attribute-specifier-seq appertains to the concept.

CWG telecon 2022-10-07:

Agreed.

[Accepted as a DR at the November, 2022 meeting.]

The grammar for a concept-definition does not include an attribute-specifier-seq_opt, making it impossible to deprecate an attribute. This seems like an oversight.