[Clang] Implementation of P2280R4 caused worse diagnostic messages

[frederick-vs-ja]

llvm-project/clang/test/SemaCXX/constant-expression-cxx11.cpp

Lines 2015 to 2016 in 52dd4b9

	constexpr int &n = n; // expected-error {{constant expression}} cxx23-note {{reference to 'n' is not a constant expression}} cxx23-note {{address of non-static constexpr variable 'n' may differ}} expected-warning {{not yet bound to a value}}
	// cxx11_20-note@-1 {{use of reference outside its lifetime is not allowed in a constant expression}}

This looks strange. The old message looks better (see also CWG453) and the new one is possibly misleading as we perhaps shouldn't say the address of a reference variable.

Originally posted by @frederick-vs-ja in #95474 (comment)

This is still reproducible on the trunk. Godbolt link.