ulem with hspace error

Question

The following code

\documentclass{minimal}
\usepackage{ulem}
\begin{document}
\emph{\hspace*{2in}}
\end{document}

used to work without error, to produce an underlined blank space of width 2 inches. Now with a brand new MikTeX installation, I get the following error

! Extra }, or forgotten \endgroup.
\UL@stop ...alty \ifnum \lastkern =\thr@@ \egroup 
                                                  \egroup \ifdim \wd \UL@box...
l.4 \emph{\hspace*{2in}}

Here are the file dates, etc.

This is pdfTeX, Version 3.14159265-2.6-1.40.21 (MiKTeX 21.1) (preloaded format=pdflatex 2021.2.7)  7 FEB 2021 13:50
entering extended mode
**./untitled-2.tex
(untitled-2.tex
LaTeX2e <2020-10-01> patch level 4
L3 programming layer <2021-01-09> xparse <2020-03-03>
("C:\Program Files\MiKTeX\tex/latex/base\minimal.cls"
Document Class: minimal 2001/05/25 Standard LaTeX minimal class
) ("C:\Program Files\MiKTeX\tex/latex/ulem\ulem.sty"
\UL@box=\box47
\UL@hyphenbox=\box48
\UL@skip=\skip47
\UL@hook=\toks15
\UL@height=\dimen138
\UL@pe=\count177
\UL@pixel=\dimen139
\ULC@box=\box49
Package: ulem 2019/11/18
\ULdepth=\dimen140
)
("C:\Program Files\MiKTeX\tex/latex/l3backend\l3backend-pdftex.def"
File: l3backend-pdftex.def 2021-01-09 L3 backend support: PDF output (pdfTeX)
\l__kernel_color_stack_int=\count178
\l__pdf_internal_box=\box50
)

Answer 1

Update

With a current LaTeX (LaTeX2e <2021-06-01> patch level 1) the patch is no longer needed.

Old answer

The \hspace command has been extended to allow calculations if the calc package is loaded. ulem hasn't updated its code yet to this change (but the maintainer has been informed). The needed patch would be something like this:

\documentclass{article}
\usepackage{calc}
\usepackage{ulem}
\makeatletter
\def\@hspace#1{\begingroup\setlength\skip@{#1}%
    \edef\x{\endgroup\hskip\the\skip@\relax}\x}%
\makeatother %return @ to normal meaning
\begin{document}

\emph{\hspace*{2in+1cm}}
\end{document}

Answer 2

The \emph{} command is for italicizing, You use \underline{} for underlining. The following MWE generates the blank space you're after on my machine. You must have redefined \emph{} in another document or something.

\documentclass{minimal}


\begin{document}

\underline{\hspace{2 in}}

\end{document}

Answer 3

I am not sure what changed. However, if you use a \kern rather than the \hspace*, it works.

\documentclass{article}
\usepackage{ulem}
\begin{document}
x\emph{\kern2in}x
\end{document}