[Bug c++/88103] New: Wrong value category when conditional expression result is used as object expression

[okannen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88103

            Bug ID: 88103
           Summary: Wrong value category when conditional expression
                    result is used as object expression
           Product: gcc
           Version: 8.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: okannen at gmail dot com
  Target Milestone: ---

In the code below, if the conditional expression is an xvalue, and only when
this xvalue is used as the object expression in class member access, gcc treat
it as if it were an lvalue. The problem does not happen when the conditional
expression is a prvalue:


struct A {
    A(int);
    A&& foo() && ;
    int i;
};
void free(A&&);

void test_xvalue(A a){
  //No error
  A&& ref = true? static_cast<A&&>(a) : static_cast<A&&>(a); 

  //No error
  free(true? static_cast<A&&>(a) : static_cast<A&&>(a));

  //Unexpected error: passing A as this discard qualifier
  (true? static_cast<A&&>(a) : static_cast<A&&>(a)).foo();

  //Unexpected error: error cannot bind rvalue reference 
  //                  of type int&& to lvalue of type int
  int&& k=(true? static_cast<A&&>(a) : static_cast<A&&>(a)).i;
}
void test_prvalue(A a){
  //No error
  A&& ref = true? static_cast<A&&>(a) : 1; 

  //No error
  free(true? static_cast<A&&>(a) : 1);

  //No error
  (true? static_cast<A&&>(a) : 1).foo();

  //No error
  int&& k=(true? static_cast<A&&>(a) : 1).i;
}