Created attachment 527020 [details] ebuild that triggers the problem cargo eclass breaks if the source directory contains a directory named `man`. When the source directory contains a directory named `man`, cargo eclass tries to install man pages from it. However, this seems to be broken as the `cargo_src_install` invokes doman with the directory itself causing `install` to complain breaking the build. I attached an ebuild that should trigger the issue.
Created attachment 527022 [details] build log
I believe it's been fixed in https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=dd53899da2ac044f815030e82a6fcf357df1dff9 closing.