* [Bug c++/95310] [concepts] Unrelated template parameters printed in diagnostic
2020-05-25 8:46 [Bug c++/95310] New: [concepts] Unrelated template parameters printed in diagnostic ensadc at mailnesia dot com
@ 2020-05-27 14:12 ` ppalka at gcc dot gnu.org
2020-10-13 19:39 ` redi at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: ppalka at gcc dot gnu.org @ 2020-05-27 14:12 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95310
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2020-05-27
Ever confirmed|0 |1
CC| |ppalka at gcc dot gnu.org
--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Confirmed.
^ permalink raw reply [flat|nested] 5+ messages in thread* [Bug c++/95310] [concepts] Unrelated template parameters printed in diagnostic
2020-05-25 8:46 [Bug c++/95310] New: [concepts] Unrelated template parameters printed in diagnostic ensadc at mailnesia dot com
2020-05-27 14:12 ` [Bug c++/95310] " ppalka at gcc dot gnu.org
@ 2020-10-13 19:39 ` redi at gcc dot gnu.org
2020-10-17 5:31 ` ensadc at mailnesia dot com
2020-10-20 3:20 ` ppalka at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: redi at gcc dot gnu.org @ 2020-10-13 19:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95310
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk by r11-3372-d6587211c02c4e2566c4e545c09757f3fbb7adab
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/95310] [concepts] Unrelated template parameters printed in diagnostic
2020-05-25 8:46 [Bug c++/95310] New: [concepts] Unrelated template parameters printed in diagnostic ensadc at mailnesia dot com
2020-05-27 14:12 ` [Bug c++/95310] " ppalka at gcc dot gnu.org
2020-10-13 19:39 ` redi at gcc dot gnu.org
@ 2020-10-17 5:31 ` ensadc at mailnesia dot com
2020-10-20 3:20 ` ppalka at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: ensadc at mailnesia dot com @ 2020-10-17 5:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95310
--- Comment #3 from ensadc at mailnesia dot com ---
When verifying the fix, I noticed a new bug:
====
template <class T> requires true
using iter_reference_t = decltype(*T{});
template <typename F>
struct result {
using type = iter_reference_t<F>;
};
template <class Out, class T>
concept indirectly_writable = requires(Out&& o, T&& t) {
iter_reference_t<Out>(*o) = 0;
};
template<class In, class Out>
requires indirectly_writable<Out, iter_reference_t<In>>
void copy(In in, Out out) {}
void test(const int* p, int* q) {
copy(q, p);
}
====
<source>: In function 'void test(const int*, int*)':
<source>:19:14: error: no matching function for call to 'copy(int*&, const
int*&)'
19 | copy(q, p);
| ^
<source>:16:6: note: candidate: 'template<class In, class Out> requires
indirectly_writable<Out, decltype(*{})> void copy(In, Out)'
16 | void copy(In in, Out out) {}
| ^~~~
<source>:16:6: note: template argument deduction/substitution failed:
<source>:16:6: note: constraints not satisfied
<source>: In substitution of 'template<class In, class Out> requires
indirectly_writable<Out, decltype(*{})> void copy(In, Out) [with In = int*; Out
= const int*]':
<source>:19:14: required from here
<source>:10:9: required for the satisfaction of 'indirectly_writable<Out,
iter_reference_t<F> >' [with Out = const int*; In = int*]
<source>:10:31: in requirements with 'Out&& o', 'T&& t' [with T = int&; Out =
const int*]
<source>:11:29: note: the required expression 'decltype(*{})(*o)=0' is invalid
11 | iter_reference_t<Out>(*o) = 0;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
cc1plus: note: set '-fconcepts-diagnostics-depth=' to at least 2 for more
detail
====
In
<source>:10:9: required for the satisfaction of 'indirectly_writable<Out,
iter_reference_t<F> >' [with Out = const int*; In = int*]
Note the mismatch between `F` and `In`.
GCC 10.2 prints `F = int*` instead of `In = int*`:
<source>:10:9: required for the satisfaction of 'indirectly_writable<Out,
iter_reference_t<F> >' [with Out = const int*; F = int*]
The name `F` comes from a completely unrelated class template, but at least the
names match in GCC 10.2.
(Interestingly, the alias template is not expanded in this line.)
^ permalink raw reply [flat|nested] 5+ messages in thread* [Bug c++/95310] [concepts] Unrelated template parameters printed in diagnostic
2020-05-25 8:46 [Bug c++/95310] New: [concepts] Unrelated template parameters printed in diagnostic ensadc at mailnesia dot com
` (2 preceding siblings ...)
2020-10-17 5:31 ` ensadc at mailnesia dot com
@ 2020-10-20 3:20 ` ppalka at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: ppalka at gcc dot gnu.org @ 2020-10-20 3:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95310
--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to ensadc from comment #3)
> When verifying the fix, I noticed a new bug:
Thanks for the heads up.
>
> ====
> template <class T> requires true
> using iter_reference_t = decltype(*T{});
>
> template <typename F>
> struct result {
> using type = iter_reference_t<F>;
> };
>
> template <class Out, class T>
> concept indirectly_writable = requires(Out&& o, T&& t) {
> iter_reference_t<Out>(*o) = 0;
> };
>
> template<class In, class Out>
> requires indirectly_writable<Out, iter_reference_t<In>>
> void copy(In in, Out out) {}
>
> void test(const int* p, int* q) {
> copy(q, p);
> }
>
> ====
> <source>: In function 'void test(const int*, int*)':
> <source>:19:14: error: no matching function for call to 'copy(int*&, const
> int*&)'
> 19 | copy(q, p);
> | ^
> <source>:16:6: note: candidate: 'template<class In, class Out> requires
> indirectly_writable<Out, decltype(*{})> void copy(In, Out)'
> 16 | void copy(In in, Out out) {}
> | ^~~~
> <source>:16:6: note: template argument deduction/substitution failed:
> <source>:16:6: note: constraints not satisfied
> <source>: In substitution of 'template<class In, class Out> requires
> indirectly_writable<Out, decltype(*{})> void copy(In, Out) [with In = int*;
> Out = const int*]':
> <source>:19:14: required from here
> <source>:10:9: required for the satisfaction of 'indirectly_writable<Out,
> iter_reference_t<F> >' [with Out = const int*; In = int*]
> <source>:10:31: in requirements with 'Out&& o', 'T&& t' [with T = int&;
> Out = const int*]
> <source>:11:29: note: the required expression 'decltype(*{})(*o)=0' is
> invalid
> 11 | iter_reference_t<Out>(*o) = 0;
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
> cc1plus: note: set '-fconcepts-diagnostics-depth=' to at least 2 for more
> detail
> ====
>
> In
>
> <source>:10:9: required for the satisfaction of
> 'indirectly_writable<Out, iter_reference_t<F> >' [with Out = const int*; In
> = int*]
>
> Note the mismatch between `F` and `In`.
>
> GCC 10.2 prints `F = int*` instead of `In = int*`:
>
> <source>:10:9: required for the satisfaction of
> 'indirectly_writable<Out, iter_reference_t<F> >' [with Out = const int*; F =
> int*]
>
> The name `F` comes from a completely unrelated class template, but at least
> the names match in GCC 10.2.
>
> (Interestingly, the alias template is not expanded in this line.)
Hmm, so the r11-3373 patch fixed only the printing of template parameters
within the constraint's parameter mapping, i.e. within the [with ...] part of
the diagnostic. But as your latest testcase shows, within the diagnostic the
constraint itself could also refer to an unrelated template parameter. To fix
this part of the diagnostic I think we would have to more generally fix PR66968
once and for all..
^ permalink raw reply [flat|nested] 5+ messages in thread