\documentclass{article}
\usepackage{fontspec}
\setmainfont[BoldItalicFont={Times New Roman}]{DejaVu Sans}
\begin{document}
1. This is normal as expected.
\textit{2. This is in italic as expected.}
\textbf{3. This is in bold as expected.}
\textit{\textbf{4. This is NOT in italic and bold as expected.}}
\textbf{\textit{5. This is NOT in bold and italic as expected.}}
\end{document}
The output is as below:
What is the correct way to make \setmainfont[BoldItalicFont={Times New Roman}]{DejaVu Sans}
take effect?