I used this answer to make all the math in my document adhere to Sans-Serif font.
However, whenever I use the Polyglossia package and add another language, I get an error which says:
Package Polyglossia error: The current Latin font Arial(1) does not contain the "Cyrillic" script! Please define \cyrillicfont with \newfontfamily command.
I get this error despite the fact that did define the Cyrillic font (using this answer).
The error can be produced using Greek, Hebrew and Arabic as well.
MWE:
%:Preamble
%:Class
\documentclass[]{article}
%:Language
\usepackage{polyglossia}
%Commenting out the following lines produces the error:
%\setdefaultlanguage{russian}
%\setotherlanguage{english}
%\setmainfont[Ligatures=TeX]{Arial}
%\newfontfamily\cyrillicfont{Arial}[Script=Cyrillic]
%:Fonts
\usepackage{fontspec}
\renewcommand\familydefault{\sfdefault}
%:Math_Font
% Taken from:https://tex.stackexchange.com/a/41501/179187
\DeclareMathVersion{sans}
\SetSymbolFont{operators}{sans}{OT1}{cmbr}{m}{n}
\SetSymbolFont{letters}{sans}{OML}{cmbrm}{m}{it}
\SetSymbolFont{symbols}{sans}{OMS}{cmbrs}{m}{n}
\SetMathAlphabet{\mathit}{sans}{OT1}{cmbr}{m}{sl}
\SetMathAlphabet{\mathbf}{sans}{OT1}{cmbr}{bx}{n}
\SetMathAlphabet{\mathtt}{sans}{OT1}{cmtl}{m}{n}
\SetSymbolFont{largesymbols}{sans}{OMX}{iwona}{m}{n}
\DeclareMathVersion{boldsans}
\SetSymbolFont{operators}{boldsans}{OT1}{cmbr}{b}{n}
\SetSymbolFont{letters}{boldsans}{OML}{cmbrm}{b}{it}
\SetSymbolFont{symbols}{boldsans}{OMS}{cmbrs}{b}{n}
\SetMathAlphabet{\mathit}{boldsans}{OT1}{cmbr}{b}{sl}
\SetMathAlphabet{\mathbf}{boldsans}{OT1}{cmbr}{bx}{n}
\SetMathAlphabet{\mathtt}{boldsans}{OT1}{cmtl}{b}{n}
\SetSymbolFont{largesymbols}{boldsans}{OMX}{iwona}{bx}{n}
\DeclareMathVersion{sans}
\SetSymbolFont{operators}{sans}{OT1}{cmsmf}{m}{n}
\SetSymbolFont{letters}{sans}{OML}{cmssm}{m}{it}
\SetSymbolFont{symbols}{sans}{OMS}{cmsssy}{m}{n}
\SetMathAlphabet{\mathit}{sans}{OT1}{cmssm}{m}{sl}
\SetMathAlphabet{\mathbf}{sans}{OT1}{cmsssy}{bx}{n}
\SetMathAlphabet{\mathtt}{sans}{OT1}{cmssex}{m}{n}
\SetSymbolFont{largesymbols}{sans}{OMX}{cmssex}{m}{n}
\newif\IfInSansMode
\let\oldsf\sffamily
\renewcommand*{\sffamily}{\oldsf\mathversion{sans}\InSansModetrue}
\let\oldbf\bfseries
\renewcommand*{\bfseries}{\oldbf\IfInSansMode\mathversion{boldsans}\else\mathversion{bold}\fi\relax}
\let\oldnorm\normalfont
\renewcommand*{\normalfont}{\oldnorm\InSansModefalse\mathversion{normal}}
\let\oldrm\rmfamily
\renewcommand*{\rmfamily}{\oldrm\InSansModefalse\mathversion{normal}}
%:Start
\begin{document}
R
$R$
$\mathsf{R=r}$
\end{document}
