[Bug c++/102002] New: spec requires typename can be dropped when used as template function return type consisting of template parameter which is at global scope

[Bug c++/102002] New: spec requires typename can be dropped when used as template function return type consisting of template parameter which is at global scope

[nickhuang99 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102002

            Bug ID: 102002
           Summary: spec requires typename can be dropped when used as
                    template function return type consisting of template
                    parameter  which is at global scope
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nickhuang99 at hotmail dot com
  Target Milestone: ---

Spec considers *typename* can be dropped when there is no ambiguous of
regarding identifier as type. And
example(https://timsong-cpp.github.io/cppwp/temp.res#general-example-5) shows
this OK.

   template<class T> T::R f();//OK, return type of a function declaration at
global scope

However, all compilers including GCC, clang, MSVC++ complains missing typename
because 

error: need ‘typename’ before ‘T::R’ because ‘T’ is a dependent scope
    1 | template<class T> T::R f();
      |                   ^
      |                   typename 



Here I quote spec(https://timsong-cpp.github.io/cppwp/temp.res#general-4.1):
   A qualified or unqualified name is said to be in a type-only context if it
is the terminal name of
    a typename-specifier, nested-name-specifier, elaborated-type-specifier,
class-or-decltype
...

I understand this relaxation of enforcing *typename* is not so critical. Still
it is nice to strictly follow spec.

[Bug c++/102002] spec requires typename can be dropped when used as template function return type consisting of template parameter which is at global scope

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102002

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |WORKSFORME
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
You need to use -std=c++20.

[Bug c++/102002] spec requires typename can be dropped when used as template function return type consisting of template parameter which is at global scope

[nickhuang99 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102002

--- Comment #2 from qingzhe huang <nickhuang99 at hotmail dot com> ---
Thank you and my apology.