Before we worry about what to change, I want to note that the original
example is syntactically incorrect. The example is
$ bash -c ': $(case x in x) esac)'
But the manual page makes it clear that each case must be ended with
";;".
case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac
Now, I haven't investigated what cleverness Bash uses, but all the cases
I've tested that conform to the case syntax are handled correctly inside
this $(...):
$ bash -c ': $( case x in x) : ;; esac )'
$ bash -c ': $( case x in x) true ;; esac )'
$ bash -c ': $( case x in (x) true ;; esac )'
It even works with the degenerate case where there are no coices, though
writing it is hard because "esac" is a keyword:
$ bash -c ': $( case x in
more> esac )'
This is with an old version, 4.2.53(1).
Dale