[Bug c++/106631] New: Unhelpful diagnostic on variable template specialization with unknown name

["barry.revzin at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106631

            Bug ID: 106631
           Summary: Unhelpful diagnostic on variable template
                    specialization with unknown name
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barry.revzin at gmail dot com
  Target Milestone: ---

Short example:

template <class T>
constexpr bool trait = true;

template <>
constexpr bool triat<int> = false;

Note the typo on triat.

The current error message gcc provides is:

<source>:5:21: error: expected initializer before '<' token
    5 | constexpr bool triat<int> = false;
      |                     ^

Which is... technically true. Given that triat doesn't exist as a variable
template, the next thing coming up needs to be an initializer for it, since
this is really a declaration. But the intent was for it to specialize trait -
it seems like it's more likely that this kind of error would come from getting
the name of the variable template wrong rather than spelling the initializer
incorrectly?

So something like:

<source>:5:21: error: unknown variable template 'triat' being specialized
    5 | constexpr bool triat<int> = false;
      |                ^~~~~
    note: did you mean trait?

Would be much more helpful.