[Bug c++/102925] New: [11.2]ICE with concept of std::convertible_to with lambda in unevaluated-context

[Bug c++/102925] New: [11.2]ICE with concept of std::convertible_to with lambda in unevaluated-context

[nickhuang99 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102925

            Bug ID: 102925
           Summary: [11.2]ICE with concept of std::convertible_to with
                    lambda in unevaluated-context
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nickhuang99 at hotmail dot com
  Target Milestone: ---

The following code causes ICE in 11.2 when clang and MSVC++ all work fine.
(https://www.godbolt.org/z/eGq118ohT)
This ICE is fixed in trunk with a different issue of no matching template
declaration for template specialization. 

#include <concepts>

template<class T>
concept IsLambda=std::convertible_to<T,decltype(+[]{})>;

template<IsLambda T> 
void foo(T t){ t();}

template<>
void foo<decltype(+[]{})>(decltype(+[]{}) t){
    t();
}



<source>:10:6: error: template-id 'foo<void (*)()>' for 'void foo(void (*)())'
does not match any template declaration
   10 | void foo<decltype(+[]{})>(decltype(+[]{}) t){
      |      ^~~~~~~~~~~~~~~~~~~~
<source>:7:6: note: candidate is: 'template<class T>  requires  IsLambda<T>
void foo(T)'
    7 | void foo(T t){ t();}
      |      ^~~
Compiler returned: 1

[Bug c++/102925] [11.2]ICE with concept of std::convertible_to with lambda in unevaluated-context

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102925

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|                            |102728

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
PR 102728 is for the rejects valid.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102728
[Bug 102728] requires statement fails to recognize lambda in unevaluated
context

[Bug c++/102925] [11.2]ICE with concept of std::convertible_to with lambda in unevaluated-context

[nickhuang99 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102925

--- Comment #2 from qingzhe huang <nickhuang99 at hotmail dot com> ---
I suspect this is related to template-specialization-related issue because if I
use original implementation of "std::convertible_to" to declare my concept
(https://en.cppreference.com/w/cpp/concepts/convertible_to), 

template <class From, class To>
concept convertible_to =
  std::is_convertible_v<From, To> &&
  requires {
    static_cast<To>(std::declval<From>());
  };


then it works. (https://www.godbolt.org/z/99eoToze3)
See this concept is not a specialization of concept "std::convertible_to"

template<class T>
concept IsLambda=std::is_convertible_v<T,decltype(+[]{})>
&& requires{
     static_cast<decltype(+[]{})>(std::declval<T>());
};

[Bug c++/102925] [11.2]ICE with concept of std::convertible_to with lambda in unevaluated-context

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102925

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED
   Target Milestone|---                         |13.0

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Was fixed in GCC 13.