[Bug c++/102137] New: class template argument deduction with template template parameter allows explicit deduction guide

[johelegp at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102137

            Bug ID: 102137
           Summary: class template argument deduction with template
                    template parameter allows explicit deduction guide
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://godbolt.org/z/qc4e95TEK.
```C++
template<class T> struct B { B(int){} };  explicit B(int) -> B<int>;
template<template<class> class T> void f() { [[maybe_unused]] T _ = 0; }
void g() { f<B>(); }
```