Uses of \@tempa in \Ref

[muzimuzhi]

Brief outline of the enhancement

\Ref is the only kernel macro which uses \@tempa. It's ok when \Ref was provided by varioref package, but when it's moved to the kernel, maybe \@tempa can be replaced with \reserved@a.

latex2e/base/ltxref.dtx

Lines 549 to 557 in 803ec3b

	% \changes{v1.1l}{2019/08/22}{Commanded moved from \texttt{varioref.sty}}
	% \changes{v1.1p}{2022/04/12}{Macro reimplemented with a starred version}%
	% \begin{macrocode}
	\def\@kernel@Ref#1{\protected@edef\@tempa{\@kernel@ref{#1}}%
	\expandafter\MakeUppercase\@tempa}
	\def\@kernel@sRef#1{\protected@edef\@tempa{\@kernel@sref{#1}}%
	\expandafter\MakeUppercase\@tempa}
	\NewDocumentCommand\Ref{s}
	{\IfBooleanTF{#1}{\@kernel@sRef}{\@kernel@Ref}}

What to do about its rollback codes?

[FrankMittelbach]

yes we could/should change that (don't think it warrants rollback, though - I think we can just alter the 2022 code). Otherwise it would mean splitting the rollback into chunks which is painful and not really that helpful in this case.