[Bug c++/86298] New: template argument cannot be narrowed to type 'int'

[zhonghao at pku dot org.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86298

            Bug ID: 86298
           Summary: template argument cannot be narrowed to type 'int'
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhonghao at pku dot org.cn
  Target Milestone: ---

The code is as follow:

template <typename ,int, int = 9223372036854775807L >
struct as_nview { };

template <typename Sequence, int I0> 
struct as_nview<Sequence, I0> 
{ };

g++ produces only a warning message, and it points to a wrong location:

warning: overflow in conversion from 'long int' to 'int' changes value from
'9223372036854775807' to '-1' [-Woverflow]
 struct as_nview<Sequence, I0>
                             ^

Instead, clang++ rejects the code:

 error: non-type template argument evaluates to
      9223372036854775807, which cannot be narrowed to type 'int'
      [-Wc++11-narrowing]
template <typename ,int, int = 9223372036854775807L >


The error message of clang++ seem to be more reasonable, right?