AutoFakeSlant does not work when specifying BoldFont

[yuishin-kikuchi]

Description

AutoFakeSlant does not work when specifying BoldFont.
Problem occurs with both xelatex/lualatex.

Check/indicate

• [ chk ] Relevant for XeTeX
• [ chk ] Relevant for LuaTeX
• [ chk ] Issue tracker has been searched for similar issues?
• [ chk ] Links to <tex.stackexchange.com> discussion if appropriate

Minimal example demonstrating the issue

\documentclass{article}
\usepackage[no-math]{fontspec}
\setmainfont{Roboto}[
  UprightFont=*-Regular,
  BoldFont=*-Bold,
  AutoFakeSlant=0.5,
] % I know roboto family has italic and bold italic version.
\begin{document}
{The quick brown fox}\par
{\bfseries The quick brown fox}\par
{\itshape The quick brown fox}\par
{\bfseries\itshape The quick brown fox}\par % why not slanted?
\end{document}

Further details

The code:

\setmainfont{Roboto}[
  UprightFont=*-Regular,
  BoldFont=*-Bold,
  AutoFakeSlant=0.5,
  BoldItalicFeatures={
    Font=*-Bold,
    FakeSlant=0.5,
  }
]

works fine.
But this is redundant.