From: waffl3x <waffl3x@protonmail.com>
To: Jason Merrill <jason@redhat.com>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH v5 1/1] c++: Initial support for P0847R7 (Deducing This) [PR102609]
Date: Mon, 27 Nov 2023 01:30:20 +0000 [thread overview]
Message-ID: <JOMwd4InHP6tKKVq365PumKCoVSHflf1vxQbfCpnXCPukvZkZDtee_ErCiFINZ1eVMsNh4hmKZBdQstUxqNgvTNYj285f3YpG8EgJPO8nzQ=@protonmail.com> (raw)
In-Reply-To: <7623e2db-ba29-42f2-85df-c2e796d7305b@redhat.com>
> > Now with that out of the way, I do still kind of feel icky about it.
> > This really is a MASSIVE edge case that will almost never matter. As
> > far as I know, instantiating explicitly like so...
> >
> > auto f = [x = 42](this auto&&) -> int { return x; };
> > int (*fp)(int&) = &decltype(f)::operator();
> >
> > ...is the only way to coerce the explicit object parameter of the
> > lambda's call operator into deducing as an unrelated type. Cases that
> > are not deduced can be caught trivially while parsing the lambda and
> > are the only reasonable cases where you might have an unrelated type.
> > Perhaps it might become relevant in the future if a proposal like
> > https://atomgalaxy.github.io/isocpp-1107/D1107.html ever made it in,
> > but we aren't there yet. So as it stands, I'm pretty certain that it's
> > just impossible to instantiate a lambda's call operator with an
> > unrelated xobj parameter type except for the above case with
> > address-of. If you can think of another, please do share, but I've
> > spent a fair amount of time on it and came up with nothing.
>
>
> I think you're right.
>
I was about to send a quick e-mail amending this, before I respond to
everything else I want to include this test case I just came up with minutes
ago.
template<typename T>
struct S : T {
using T::operator();
operator int() const {return {};}
};
int main()
{
auto s0 = S{[](this auto&& self) { return self; }};
auto s1 = S{[x = 0](this auto&& self) { return self; }};
s0.operator()<int>();
s1.operator()<int>();
}
So I was wrong, but, the good news is that this does demonstrate that there
is a code path where my diagnostic works.
template<typename T>
concept NotInt = (!__is_same (T, int));
template<bool> struct enable_if {};
template<> struct enable_if<true> { using type = decltype(nullptr); };
template<bool B> using enable_if_t = typename enable_if<B>::type;
template<NotInt T>
void using_concepts(T) {}
template<typename T, enable_if_t<!__is_same (T, int)> = nullptr>
void using_enable_if(T) {}
void test()
{
void (*fp_concepts)(int) = &using_concepts;
void (*fp_enable_if)(int) = &using_enable_if;
using_concepts(0);
using_enable_if(0);
}
I also have this test case that demonstrates the difference in diagnostic
quality. This is unrelated to explicit object member functions though, but
it does demonstrate that the diagnostics that I currently produce are in
equal quality to the ones already produced in these cases.
At this point I feel like I am unlikely to start fixing the bug with
captures not being treated as const tonight. Cleaning up the tests is taking
me longer than I thought.
Anyway I'm just rushing this e-mail to clarify this mistake, admittedly I am
a little excited to have found (which in hindsight should have been obvious)
a test case that more directly calls a lambda's call operator with an
unrelated type.
Alex
next prev parent reply other threads:[~2023-11-27 1:30 UTC|newest]
Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-31 6:02 [PATCH 1/2] " waffl3x
2023-08-31 8:33 ` Jakub Jelinek
2023-09-02 8:43 ` waffl3x
2023-09-11 13:49 ` [PATCH v2 " waffl3x
2023-09-19 20:14 ` Jason Merrill
2023-09-20 0:30 ` waffl3x
2023-09-20 21:19 ` Jason Merrill
2023-09-21 11:28 ` waffl3x
2023-09-22 11:30 ` Jason Merrill
2023-09-26 1:56 ` [PATCH v3 " waffl3x
2023-09-27 22:43 ` Hans-Peter Nilsson
2023-09-27 23:35 ` Waffl3x
2023-10-17 20:53 ` Jason Merrill
2023-10-17 21:11 ` Jason Merrill
2023-10-18 11:46 ` waffl3x
2023-10-18 14:17 ` Jason Merrill
2023-10-18 17:28 ` waffl3x
2023-10-18 17:45 ` Jakub Jelinek
2023-10-18 18:12 ` Jason Merrill
2023-10-19 21:05 ` waffl3x
2023-10-19 21:11 ` Jakub Jelinek
2023-10-19 21:31 ` waffl3x
2023-10-19 21:53 ` Jakub Jelinek
2023-10-19 22:18 ` Jason Merrill
[not found] ` <Q2xXS2RkwtzDslDUAsi4YWupkb9s3QKvecqsxLNUr=5FL-MdSmzIJcZ96S3B9Avk30GneMm8R67JsQ4D-Uj1JB6N8dhTw6LAlNsrpLKHuLP2o=3D@protonmail.com>
2023-10-19 22:51 ` waffl3x
2023-10-19 23:35 ` waffl3x
2023-10-20 2:39 ` Jason Merrill
2023-10-20 4:34 ` waffl3x
2023-10-20 16:01 ` Jason Merrill
[not found] ` <zXWkSXEO=5FH62WXyNUeV1zNAx9wSVGQ5ooxKAfpN2InCP4X25uOC0yTZlnMqbDMoIa4lGwj0hP-KEP5UIcMs1S1zkhz=5FZx4oM3oz09DY2BRg=3D@protonmail.com>
[not found] ` <9YnRZJPkB8KCk8R86UDwWBoNnmOEAir4IU4enb1qIGgVdkB6dwy76ClgAzwpPqpToQ9sLTBs50EIRwhivBJU6RAFfLt-fjJxdYTZ35YVFWA=3D@protonmail.com>
2023-10-28 4:07 ` waffl3x
2023-10-28 23:21 ` waffl3x
2023-11-01 23:15 ` waffl3x
2023-11-02 7:01 ` waffl3x
2023-11-02 7:01 ` Jakub Jelinek
2023-11-03 3:04 ` Jason Merrill
2023-11-03 4:44 ` waffl3x
2023-11-03 18:05 ` Jason Merrill
2023-11-04 6:40 ` waffl3x
2023-11-09 18:44 ` Jason Merrill
2023-11-10 4:24 ` waffl3x
2023-11-10 23:12 ` Jason Merrill
2023-11-11 10:43 ` waffl3x
2023-11-11 11:24 ` waffl3x
2023-11-14 3:48 ` Jason Merrill
2023-11-14 4:36 ` waffl3x
2023-11-18 6:43 ` waffl3x
2023-11-19 6:22 ` Jason Merrill
2023-11-19 13:39 ` waffl3x
2023-11-19 16:31 ` Jason Merrill
2023-11-19 18:36 ` waffl3x
2023-11-19 20:34 ` Jason Merrill
2023-11-19 21:44 ` waffl3x
2023-11-20 14:35 ` Jason Merrill
[not found] ` <1MdaTybBd=5Fo4uw-Gb23fYyd5GNz7qFqoSe=5Ff5h90LY=5FBdzM2ge2qPSyCuiCLYoYcZSjmVv13fw1LmjQC=5FM2L8raS1fydY5pEJ=5Fvwvv5Z-0k=3D@protonmail.com>
2023-11-21 10:02 ` waffl3x
2023-11-21 13:04 ` [PATCH v5 1/1] " waffl3x
2023-11-22 3:22 ` Jason Merrill
2023-11-22 20:46 ` waffl3x
2023-11-22 21:38 ` Jason Merrill
[not found] ` <kltTuyDDwoyOmhBWostMKm5zF3sQCGz3HjMBrBUK6LOZp1-AbGMl5ijKKMlOncwR2yiWippyp89sFPZykNF3OVyz4yknnCVwn=5FiHJPUl25k=3D@protonmail.com>
[not found] ` <dHEpSeuiljMbH0YhwLULApd3yO3LNaVkamGW2KJBYBl0EgMrtpJZ41GeTVOc77siD1kh2vkF4zwInWWGxYXfcnW4XV7sfDPX7cY028JiORE=3D@protonmail.com>
2023-11-22 21:56 ` waffl3x
2023-11-22 22:44 ` waffl3x
2023-11-24 6:49 ` waffl3x
2023-11-24 23:26 ` waffl3x
2023-11-25 1:14 ` waffl3x
2023-11-26 21:30 ` Jason Merrill
2023-11-26 23:10 ` waffl3x
2023-11-27 1:16 ` Jason Merrill
[not found] ` <BEI8PD7nktTuX7dimb22uDnR0b8Bc8ozi4xx9KbiEFj8TjgUCxMfEPpcIPL0bkdThBBab97T1uEJ9rUM3va1eiE1TyRw=5FiLrxwKgg30ZaW0=3D@protonmail.com>
2023-11-27 1:30 ` waffl3x [this message]
2023-11-27 1:44 ` waffl3x
2023-11-27 2:40 ` Jason Merrill
2023-11-27 5:35 ` [PATCH v6 " waffl3x
2023-11-28 3:31 ` waffl3x
2023-11-28 10:00 ` waffl3x
2023-11-30 5:00 ` Jason Merrill
2023-11-30 6:36 ` waffl3x
2023-11-30 14:55 ` Jason Merrill
2023-12-01 6:02 ` waffl3x
2023-12-01 16:52 ` Jason Merrill
2023-12-02 1:31 ` waffl3x
2023-12-02 15:02 ` Jason Merrill
[not found] ` <KQegse=5FguOyql4Ok1lrAgS7gasZJd1pOoPbCTdGxcHh-G4A9Tlf5zCnGJmqtshMt72edmcXdIapaZNPp4VJp5Ar9PHZbUrbwDsPjTSUrnOI=3D@protonmail.com>
[not found] ` <59LofhYhxl7MLEuElXwZcESRB6MpjdG-iq-89B63siDRo5k0j-y6z-PVa6Y3iE1xE5LkJwpwTFi82bd0RZjB1yZbSJptFdPTBWfvOGj1W78=3D@protonmail.com>
2023-12-05 4:35 ` waffl3x
2023-12-05 4:39 ` waffl3x
2023-12-05 5:54 ` waffl3x
2023-12-06 7:33 ` [PATCH v7 " waffl3x
2023-12-06 8:48 ` Jakub Jelinek
2023-12-06 9:31 ` waffl3x
2023-12-06 11:08 ` waffl3x
2023-12-08 19:25 ` Jason Merrill
2023-12-10 15:22 ` waffl3x
2023-12-10 18:59 ` Jason Merrill
2023-12-22 9:01 ` waffl3x
2023-12-22 17:26 ` Jason Merrill
2023-12-23 7:10 ` waffl3x
2023-12-26 16:37 ` Jason Merrill
2024-01-01 15:17 ` waffl3x
2024-01-01 15:34 ` waffl3x
2024-01-01 17:12 ` waffl3x
2024-01-06 12:37 ` waffl3x
2023-11-25 17:32 ` [PATCH v5 " Jason Merrill
2023-11-25 22:59 ` waffl3x
2023-09-19 20:24 ` [PATCH 1/2] " Jason Merrill
[not found] <b=5FiIXwWwO63ZE1ZSZHUIAdWyA2sqGsE3FM7eXfsInWogDyBZRsw8CwNsvFSDmEVmBtdq0pqb4zJ55HN2JCR7boDNramlEfne-R5PWdUXjbA=3D@protonmail.com>
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