CWG2678 std::source_location::current is unimplementable

Author: burblebee

source/basic.tex

@@ -680,6 +680,11 @@
 shall be constant-initialized if
 the object is constant-initialized in any such definition.
 
+\item In each such definition,
+corresponding manifestly constant-evaluated expressions
+that are not value-dependent
+shall have the same value\iref{expr.const,temp.dep.constexpr}.
+
 \item In each such definition, the overloaded operators referred
 to, the implicit calls to conversion functions, constructors, operator
 new functions and operator delete functions, shall refer to the same