loading latexrelease errors if deprecation is checked

[u-fischer]

Minimal example showing the bug

\ExplSyntaxOn
\debug_on:n {deprecation}
\ExplSyntaxOff
\RequirePackage[2025/01/01]{latexrelease}

errors with

(./test-utf8.tex
LaTeX2e <2025-11-01>
L3 programming layer <2025-11-14>
(c:/texlive/2025/texmf-dist/tex/latex/l3kernel/l3debug.def
File: l3debug.def 2025-12-24 L3 Debugging support
)
(c:/texlive/2025/texmf-dist/tex/latex/base/latexrelease.sty
LaTeX Info: Redefining \IfTargetDateBefore on input line 292.
Package: latexrelease 2025/01/31 v1.0q LaTeX release emulation and tests (inclu
ding releases up to 2025-11-01)

Runaway text?
\cs_gset_protected:Npn \__latexrelease_declare_command:w {\@star@or@long \ETC.
! Forbidden control sequence found while scanning text of \unexpanded.
<inserted text> 
                }
l.551   \msg_new:nnnn \msg_gset:nnnn
                                    
? x

(this affects e.g. test github-0401 which doesn't compile).

[muzimuzhi]

To ignore _new errors when rolling back, latexrelease redefines several new-commands to their set/declare relatives without checking if the control sequence to be defined is free. This includes redefining \msg_new:nnnn to \msg_gset:nnnn, but the latter was deprecated by l3kernel 2024-02-13.

Considering the uses of non-global \defs in latexrelease, we can assume the latexrelease package is always loaded at the top-level (although it's only checked/force since LaTeX2e 2024-06-01), the \msg_new:nnnn can be redefined to \msg_set:nnnn to avoid the l3debug deprecation error.