Proposed resolution (approved by CWG 2024-03-20):

1. Change in 9.5.4 [dcl.init.ref] bullet 5.3 as follows:

   Otherwise, if the initializer expression

   • is an rvalue (but not a bit-field) or function lvalue and “cv1 T1” is reference-compatible with “cv2 T2”, or
   • has a class type (i.e., T2 is a class type), where T1 is not reference-related to T2, and can be converted to an rvalue or function lvalue of type “cv3 T3”, where “cv1 T1” is reference-compatible with “cv3 T3” (see 12.2.2.7 [over.match.ref]),

   then the initializer expression in the first case and the converted expression in the second case is called the converted initializer. If the converted initializer is a prvalue, let its type be denoted by T4; the temporary materialization conversion (7.3.5 [conv.rval]) is applied, considering the type of the prvalue to be is adjusted to type “cv1 T4” (7.3.6 [conv.qual]) and the temporary materialization conversion (7.3.5 [conv.rval]) is applied. In any case, the reference binds to the resulting glvalue (or to an appropriate base class subobject).

2. Append to the example in 9.5.4 [dcl.init.ref] bullet 5.3 as follows:

     B&& rrb = x;  // binds directly to the result of operator B
   
     constexpr int f() {
       const int &x = 42;
       const_cast<int &>(x) = 1;  // undefined behavior
       return x;
     }
     constexpr int z = f();   // error: not a constant expression
   

3. Change the example in 9.5.4 [dcl.init.ref] bullet 5.4 as follows:

     const double& rcd2 = 2;   // rcd2 refers to temporary with type const double and value 2.0