[Bug c++/96331] Class template argument deduction (CTAD) with Concepts
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96331 Patrick Palka changed: What|Removed |Added Resolution|--- |DUPLICATE Status|NEW |RESOLVED CC||ppalka at gcc dot gnu.org --- Comment #5 from Patrick Palka --- This appears to be a dup of PR93083 which is fixed for GCC >= 10.3. *** This bug has been marked as a duplicate of bug 93083 ***
[Bug c++/96331] Class template argument deduction (CTAD) with Concepts
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96331
Pilar Latiesa changed:
What|Removed |Added
CC||pilarlatiesa at gmail dot com
--- Comment #4 from Pilar Latiesa ---
Another testcase, taken from
https://stackoverflow.com/questions/64567607/why-is-there-an-error-no-matching-function-for-call-to-aa-auto
template
struct A {};
template
struct B {};
template
struct is_B {};
template
struct is_B> {}; // error
template
using B_t = B; // error
[Bug c++/96331] Class template argument deduction (CTAD) with Concepts
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96331 Jonathan Wakely changed: What|Removed |Added Resolution|INVALID |--- Status|RESOLVED|NEW Ever confirmed|0 |1 Last reconfirmed||2020-10-02 Keywords||rejects-valid --- Comment #3 from Jonathan Wakely --- Reopening then, thanks, Tim.
[Bug c++/96331] Class template argument deduction (CTAD) with Concepts
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96331
TC changed:
What|Removed |Added
CC||rs2740 at gmail dot com
--- Comment #2 from TC ---
(In reply to Jonathan Wakely from comment #1)
> (In reply to Nicole from comment #0)
> > template
>
> This is not valid. fixed_string is a class template, not a type and not a
> concept. So you can't use it as a template parameter.
>
> I don't think this is a bug.
It is a placeholder for a deduced class type, which is allowed by
[temp.param]/6.3.
The example can be reduced drastically:
template
struct S { };
template
concept C = true;
static_assert(C{}>); // OK
template
void f() requires C { // error
}
:11:19: error: class template argument deduction failed:
11 | void f() requires C {
| ^~~~
:11:19: error: no matching function for call to 'S(S<...auto...>)'
:2:8: note: candidate: 'template S()-> S'
2 | struct S {
|^
:2:8: note: template argument deduction/substitution failed:
:11:19: note: candidate expects 0 arguments, 1 provided
11 | void f() requires C {
| ^~~~
:2:8: note: candidate: 'template S(S)-> S'
2 | struct S {
|^
:2:8: note: template argument deduction/substitution failed:
:11:19: note: mismatched types 'S' and 'S<...auto...>'
11 | void f() requires C {
| ^~~~
Compiler returned: 1
[Bug c++/96331] Class template argument deduction (CTAD) with Concepts
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96331 Jonathan Wakely changed: What|Removed |Added Resolution|--- |INVALID Status|UNCONFIRMED |RESOLVED --- Comment #1 from Jonathan Wakely --- (In reply to Nicole from comment #0) > template This is not valid. fixed_string is a class template, not a type and not a concept. So you can't use it as a template parameter. I don't think this is a bug.
