Using the combination \MakeTextLowercase and \cftchapterfont in the memoir class with the hyperref package causes strange issues when attempting to make the table of contents’ chapter titles minuscule.
\documentclass{memoir}
\usepackage{hyperref}
\renewcommand*{\cftchapterfont}{\MakeTextLowercase}
\begin{document}
\tableofcontents
\chapter{This Is a Chapter}
\end{document}
The first errors are like this, and then follows a load of missing/extra {/} and control sequences.
! Undefined control sequence.
\find@pdflink ...ode \protected@edef \Hy@testname
{#2}\ifx \Hy@testname \@em...
l.1 ...entsline {chapter}{Contents}{1}{section*.1}
I think some packages/fonts have an option to always use minuscule small caps, but I want to use garamondx and from my reading of the garamondx manual, I have yet to find a way. How can I make hyperref behave?

\MakeTextLowercaseis not expandable and can't go to the ToC generated withhyperref– Oct 01 '17 at 21:45\MakeTextLowercaseis not a font changing declaration. The\cftchapterfontshould be defined as a declaration such as\scshapeor\bfseries, whereas\MakeTextLowercaseis a command taking an argument. – egreg Oct 01 '17 at 21:52memoirmanual, so assumed it was appropriate:\renewcommand\cftchapterfont{\scshape\MakeTextLowercase}– gnucchi Oct 01 '17 at 22:06\@chapternot matching the definition, or being unusable when you actually want another title in the ToC? – gnucchi Oct 01 '17 at 22:21