[Bug c++/89642] New: gcc rejects valid implicit typename context in cast

[blitzrakete at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89642

            Bug ID: 89642
           Summary: gcc rejects valid implicit typename context in cast
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: blitzrakete at gmail dot com
  Target Milestone: ---

template <typename T>
void f(T t) {
  static_cast<int(T::type)>(t); // gcc rejects, but this is well-formed
}

gcc rejects the above with:

<source>: In function 'void f(T)':

<source>:3:18: error: expected '>' before '(' token

    3 |   static_cast<int(T::type)>(t);

      |                  ^

But the code is well-formed, since the smallest enclosing type-id of
`int(T::type)` is the type-id of the static_cast, which is a valid type-id-only
context as per [temp.res]p5.