[Bug c++/90320] New: Explicit constructor called implicitly

[mitza at ociweb dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90320

            Bug ID: 90320
           Summary: Explicit constructor called implicitly
           Product: gcc
           Version: 8.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mitza at ociweb dot com
  Target Milestone: ---

May be related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87605 but this
doesn't involve the ternary operator.

The following example instantiates and calls M::M<M&>(M&) on GCC 8.3 and trunk
(godbolt.org), clang and other compilers don't.

struct M {
  explicit M(int);
  template <typename T> explicit M(T&&);
  M& a();
};

struct V {
  V(M m);
};

void addV(const V&);

int main() {
  addV(M(1).a());
}