On 1/10/25 1:36 PM, Patrick Palka wrote:
On Tue, 1 Oct 2024, Patrick Palka wrote:
On Mon, 16 Sep 2024, Patrick Palka wrote:
On Thu, 30 Nov 2023, Patrick Palka wrote:
On Fri, 3 Nov 2023, Patrick Palka wrote:
On Tue, 3 May 2022, Jason Merrill wrote:
On 5/2/22 14:50, Patrick Palka wrote:
Currently when checking the constraints of a class template, we do so in
the context of the template, not the specialized type. This is the best
we can do for a primary template since the specialized type is valid
only if the primary template's constraints are satisfied.
Hmm, that's unfortunate. It ought to be possible, if awkward, to form the
type long enough to check its constraints.
(Sorry, lost track of this patch...)
Seems doable, but I'm not sure if would make any difference in practice?
If the access context during satisfaction of a primary class template's
constraints is the specialization rather than the primary template,
then that should only make a difference if there's some friend declaration
naming the specialization. But that'd mean the specialization's
constraints had to have been satisfied at that point, before the friend
declaration went into effect. So either the constraints don't depend on
the access granted by the friend declaration anyway, or they do and the
program is ill-formed (due to either satifaction failure or instability) IIUC.
For example, I don't think an adapted version of the testcase without a
partial specialization is valid, regardless of whether the access context
during satisfaction of A<B> is A<B> or just A:
template<class T>
concept fooable = requires(T t) { t.foo(); };
template<fooable T>
struct A { };
struct B {
private:
friend struct A<B>; // satisfaction failure at this point
void foo();
};
template struct A<B>;
... so in light of the above, I wonder if the original patch can go in
as-is?
Ping.
Ping.
Ping.
As I commented on the PR, we probably want to stop considering
friendship at all in this testcase, so the value of fooable<T> does not
depend on where it appears. The resolution for 2589 is still under
review, but there seems to be general agreement on that point.
Sorry I didn't previously point to that in this thread.
Jason
