[ 2022-03-04; Reflector poll ]

Set priority to 3 after reflector poll. Probably NAD, since [allocator.requirements.general]/11 allows any allocator instantiation to fail with a hard error outside the immediate context, making it impossible to guarantee a SFINAE-friendly result. Also unclear what motivation there is for it being SFINAE friendly.

[ 2022-01-29; Daniel comments ]

This issue has some overlap with LWG 3545 in regard to the question how we should handle the rebind member template of the pointer_traits primary template as specified by [pointer.traits.types] p3. It would seem preferable to decide for the same approach in both cases.

[allocator.traits.types]/11 says that the instantiation of rebind_alloc is sometimes ill-formed, however, it's unclear such ill-formedness results in substitution failure or hard error. It seems that current implementations (libc++, libstd++, MSVC STL) give substitution errors, and we should reword [allocator.traits.types]/11 with "Constraints:".