https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94673
gcc-bugs at marehr dot dialup.fu-berlin.de changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |WORKSFORME
Status|UNCONFIRMED |RESOLVED
--- Comment #5 from gcc-bugs at marehr dot dialup.fu-berlin.de ---
(In reply to Patrick Palka from comment #4)
> Don't we already do this with -fconcepts-diagnostics-depth=2 ?
You are right, sorry! Haven't checked that again thoroughly, and it seems that
you do.
> -fconcepts-diagnostics-depth=2
will produce
```
<source>:18:15: error: static assertion failed
18 | static_assert(foo<int &&>); // fails with clang
| ^~~~~~~~~~~
<source>:18:15: note: constraints not satisfied
<source>:9:9: required by the constraints of 'template<class t> concept foo'
<source>:9:15: in requirements with 't v' [with t = int&&]
<source>:11:6: note: 'v' does not satisfy return-type-requirement, because
11 | {v} -> std::same_as<t &>;
| ~^~~~~~~~~~~~~~~~~~~~~~~
<source>:11:6: error: deduced expression type does not satisfy placeholder
constraints
<source>:11:6: note: constraints not satisfied
In file included from
/opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/compare:39,
from
/opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/bits/stl_pair.h:65,
from
/opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/utility:70,
from <source>:1:
/opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/concepts:57:15: required
for the satisfaction of '__same_as<_Tp, _Up>' [with _Tp = int&&; _Up = int&]
/opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/concepts:62:13: required
for the satisfaction of 'same_as<decltype(auto) [requires
std::same_as<<placeholder>, t&>], t&>' [with decltype(auto) [requires
std::same_as<<placeholder>, t&>] = int&&; t = int&&]
/opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/concepts:57:32: note: the
expression 'is_same_v<_Tp, _Up> [with _Tp = int&&; _Up = int&]' evaluated to
'false'
57 | concept __same_as = std::is_same_v<_Tp, _Up>;
|
```
It seems that the behaviour changed again in gcc-11:
```
template <typename t>
concept foo = requires(t v)
{
{v} -> same_as<t &>;
};
static_assert(foo<int &&>); // true in gcc-10, false in gcc-11
```
Thank you again, from my POV can be closed.
