For openSUSE Leap 15.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:frispete:haskell/openSUSE_Leap_15.2/home:frispete:haskell.repo
zypper refresh
zypper install ghc-asn1-types
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:frispete:haskell/openSUSE_Leap_15.1/home:frispete:haskell.repo
zypper refresh
zypper install ghc-asn1-types
For openSUSE Leap 15.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:frispete:haskell/openSUSE_Leap_15.0/home:frispete:haskell.repo
zypper refresh
zypper install ghc-asn1-types