Proposed resolution (approved by CWG 2023-10-06):
Change in 7.7 [expr.const] paragraph 19 as follows:
[Note 11: Except for a static_assert-message, aAmanifestly constant-evaluated expression is evaluated even in an unevaluated operand (7.2.3 [expr.context]). —end note]
Change the grammar in 9.1 [dcl.pre] as follows:
static_assert-message: unevaluated-stringconditional-expressionconstant-expression
Change in 9.1 [dcl.pre] bullet 11.2 as follows:
- ...
- if the static_assert-message is a
conditional-expressionconstant-expression M, ...